release: 0.2.2

Unfortunately removal of internal/hlog brought about some changes that breaks API. This will likely be the last 0.2.x release.

Signed-off-by: Ophestra <cat@gensokyo.uk>

cmd/hakurei/command.go

@@ -6,11 +6,9 @@ import (
 	"io"
 	"log"
 	"os"
-	"os/signal"
 	"os/user"
 	"strconv"
 	"sync"
-	"syscall"
 	"time"
 
 	"hakurei.app/command"
@@ -24,7 +22,7 @@ import (
 	"hakurei.app/system/dbus"
 )
 
-func buildCommand(out io.Writer) command.Command {
+func buildCommand(ctx context.Context, out io.Writer) command.Command {
 	var (
 		flagVerbose bool
 		flagJSON    bool
@@ -44,35 +42,35 @@ func buildCommand(out io.Writer) command.Command {
 		config := tryPath(args[0])
 		config.Args = append(config.Args, args[1:]...)
 
-		runApp(config)
+		app.Main(ctx, config)
 		panic("unreachable")
 	})
 
 	{
 		var (
-			dbusConfigSession string
+			flagDBusConfigSession string
-			dbusConfigSystem  string
+			flagDBusConfigSystem  string
-			mpris             bool
+			flagDBusMpris         bool
-			dbusVerbose       bool
+			flagDBusVerbose       bool
 
-			fid      string
+			flagID       string
-			aid      int
+			flagIdentity int
-			groups   command.RepeatableFlag
+			flagGroups   command.RepeatableFlag
-			homeDir  string
+			flagHomeDir  string
-			userName string
+			flagUserName string
 
-			wayland, x11, dBus, pulse bool
+			flagWayland, flagX11, flagDBus, flagPulse bool
 		)
 
 		c.NewCommand("run", "Configure and start a permissive default sandbox", func(args []string) error {
 			// initialise config from flags
 			config := &hst.Config{
-				ID:   fid,
+				ID:   flagID,
 				Args: args,
 			}
 
-			if aid < 0 || aid > 9999 {
+			if flagIdentity < 0 || flagIdentity > 9999 {
-				log.Fatalf("aid %d out of range", aid)
+				log.Fatalf("identity %d out of range", flagIdentity)
 			}
 
 			// resolve home/username from os when flag is unset
@@ -80,14 +78,7 @@ func buildCommand(out io.Writer) command.Command {
 				passwd     *user.User
 				passwdOnce sync.Once
 				passwdFunc = func() {
-					var us string
+					us := strconv.Itoa(app.HsuUid(new(app.Hsu).MustID(), flagIdentity))
-					if uid, err := std.Uid(aid); err != nil {
-						hlog.PrintBaseError(err, "cannot obtain uid from setuid wrapper:")
-						os.Exit(1)
-					} else {
-						us = strconv.Itoa(uid)
-					}
-
 					if u, err := user.LookupId(us); err != nil {
 						hlog.Verbosef("cannot look up uid %s", us)
 						passwd = &user.User{
@@ -103,21 +94,21 @@ func buildCommand(out io.Writer) command.Command {
 				}
 			)
 
-			if homeDir == "os" {
+			if flagHomeDir == "os" {
 				passwdOnce.Do(passwdFunc)
-				homeDir = passwd.HomeDir
+				flagHomeDir = passwd.HomeDir
 			}
 
-			if userName == "chronos" {
+			if flagUserName == "chronos" {
 				passwdOnce.Do(passwdFunc)
-				userName = passwd.Username
+				flagUserName = passwd.Username
 			}
 
-			config.Identity = aid
+			config.Identity = flagIdentity
-			config.Groups = groups
+			config.Groups = flagGroups
-			config.Username = userName
+			config.Username = flagUserName
 
-			if a, err := container.NewAbs(homeDir); err != nil {
+			if a, err := container.NewAbs(flagHomeDir); err != nil {
 				log.Fatal(err.Error())
 				return err
 			} else {
@@ -125,105 +116,114 @@ func buildCommand(out io.Writer) command.Command {
 			}
 
 			var e system.Enablement
-			if wayland {
+			if flagWayland {
 				e |= system.EWayland
 			}
-			if x11 {
+			if flagX11 {
 				e |= system.EX11
 			}
-			if dBus {
+			if flagDBus {
 				e |= system.EDBus
 			}
-			if pulse {
+			if flagPulse {
 				e |= system.EPulse
 			}
 			config.Enablements = hst.NewEnablements(e)
 
 			// parse D-Bus config file from flags if applicable
-			if dBus {
+			if flagDBus {
-				if dbusConfigSession == "builtin" {
+				if flagDBusConfigSession == "builtin" {
-					config.SessionBus = dbus.NewConfig(fid, true, mpris)
+					config.SessionBus = dbus.NewConfig(flagID, true, flagDBusMpris)
 				} else {
-					if conf, err := dbus.NewConfigFromFile(dbusConfigSession); err != nil {
+					if conf, err := dbus.NewConfigFromFile(flagDBusConfigSession); err != nil {
-						log.Fatalf("cannot load session bus proxy config from %q: %s", dbusConfigSession, err)
+						log.Fatalf("cannot load session bus proxy config from %q: %s", flagDBusConfigSession, err)
 					} else {
 						config.SessionBus = conf
 					}
 				}
 
 				// system bus proxy is optional
-				if dbusConfigSystem != "nil" {
+				if flagDBusConfigSystem != "nil" {
-					if conf, err := dbus.NewConfigFromFile(dbusConfigSystem); err != nil {
+					if conf, err := dbus.NewConfigFromFile(flagDBusConfigSystem); err != nil {
-						log.Fatalf("cannot load system bus proxy config from %q: %s", dbusConfigSystem, err)
+						log.Fatalf("cannot load system bus proxy config from %q: %s", flagDBusConfigSystem, err)
 					} else {
 						config.SystemBus = conf
 					}
 				}
 
 				// override log from configuration
-				if dbusVerbose {
+				if flagDBusVerbose {
-					config.SessionBus.Log = true
+					if config.SessionBus != nil {
-					config.SystemBus.Log = true
+						config.SessionBus.Log = true
+					}
+					if config.SystemBus != nil {
+						config.SystemBus.Log = true
+					}
 				}
 			}
 
-			// invoke app
+			app.Main(ctx, config)
-			runApp(config)
 			panic("unreachable")
 		}).
-			Flag(&dbusConfigSession, "dbus-config", command.StringFlag("builtin"),
+			Flag(&flagDBusConfigSession, "dbus-config", command.StringFlag("builtin"),
 				"Path to session bus proxy config file, or \"builtin\" for defaults").
-			Flag(&dbusConfigSystem, "dbus-system", command.StringFlag("nil"),
+			Flag(&flagDBusConfigSystem, "dbus-system", command.StringFlag("nil"),
 				"Path to system bus proxy config file, or \"nil\" to disable").
-			Flag(&mpris, "mpris", command.BoolFlag(false),
+			Flag(&flagDBusMpris, "mpris", command.BoolFlag(false),
 				"Allow owning MPRIS D-Bus path, has no effect if custom config is available").
-			Flag(&dbusVerbose, "dbus-log", command.BoolFlag(false),
+			Flag(&flagDBusVerbose, "dbus-log", command.BoolFlag(false),
 				"Force buffered logging in the D-Bus proxy").
-			Flag(&fid, "id", command.StringFlag(""),
+			Flag(&flagID, "id", command.StringFlag(""),
 				"Reverse-DNS style Application identifier, leave empty to inherit instance identifier").
-			Flag(&aid, "a", command.IntFlag(0),
+			Flag(&flagIdentity, "a", command.IntFlag(0),
 				"Application identity").
-			Flag(nil, "g", &groups,
+			Flag(nil, "g", &flagGroups,
 				"Groups inherited by all container processes").
-			Flag(&homeDir, "d", command.StringFlag("os"),
+			Flag(&flagHomeDir, "d", command.StringFlag("os"),
 				"Container home directory").
-			Flag(&userName, "u", command.StringFlag("chronos"),
+			Flag(&flagUserName, "u", command.StringFlag("chronos"),
 				"Passwd user name within sandbox").
-			Flag(&wayland, "wayland", command.BoolFlag(false),
+			Flag(&flagWayland, "wayland", command.BoolFlag(false),
 				"Enable connection to Wayland via security-context-v1").
-			Flag(&x11, "X", command.BoolFlag(false),
+			Flag(&flagX11, "X", command.BoolFlag(false),
 				"Enable direct connection to X11").
-			Flag(&dBus, "dbus", command.BoolFlag(false),
+			Flag(&flagDBus, "dbus", command.BoolFlag(false),
 				"Enable proxied connection to D-Bus").
-			Flag(&pulse, "pulse", command.BoolFlag(false),
+			Flag(&flagPulse, "pulse", command.BoolFlag(false),
 				"Enable direct connection to PulseAudio")
 	}
 
-	var showFlagShort bool
+	{
-	c.NewCommand("show", "Show live or local app configuration", func(args []string) error {
+		var flagShort bool
-		switch len(args) {
+		c.NewCommand("show", "Show live or local app configuration", func(args []string) error {
-		case 0: // system
+			switch len(args) {
-			printShowSystem(os.Stdout, showFlagShort, flagJSON)
+			case 0: // system
+				printShowSystem(os.Stdout, flagShort, flagJSON)
 
-		case 1: // instance
+			case 1: // instance
-			name := args[0]
+				name := args[0]
-			config, entry := tryShort(name)
+				config, entry := tryShort(name)
-			if config == nil {
+				if config == nil {
-				config = tryPath(name)
+					config = tryPath(name)
+				}
+				printShowInstance(os.Stdout, time.Now().UTC(), entry, config, flagShort, flagJSON)
+
+			default:
+				log.Fatal("show requires 1 argument")
 			}
-			printShowInstance(os.Stdout, time.Now().UTC(), entry, config, showFlagShort, flagJSON)
+			return errSuccess
+		}).Flag(&flagShort, "short", command.BoolFlag(false), "Omit filesystem information")
+	}
 
-		default:
+	{
-			log.Fatal("show requires 1 argument")
+		var flagShort bool
-		}
+		c.NewCommand("ps", "List active instances", func(args []string) error {
-		return errSuccess
+			var sc hst.Paths
-	}).Flag(&showFlagShort, "short", command.BoolFlag(false), "Omit filesystem information")
+			app.CopyPaths(&sc, new(app.Hsu).MustID())
-
+			printPs(os.Stdout, time.Now().UTC(), state.NewMulti(sc.RunDirPath.String()), flagShort, flagJSON)
-	var psFlagShort bool
+			return errSuccess
-	c.NewCommand("ps", "List active instances", func(args []string) error {
+		}).Flag(&flagShort, "short", command.BoolFlag(false), "Print instance id")
-		printPs(os.Stdout, time.Now().UTC(), state.NewMulti(std.Paths().RunDirPath.String()), psFlagShort, flagJSON)
+	}
-		return errSuccess
-	}).Flag(&psFlagShort, "short", command.BoolFlag(false), "Print instance id")
 
 	c.Command("version", "Display version information", func(args []string) error {
 		fmt.Println(internal.Version())
@@ -247,20 +247,3 @@ func buildCommand(out io.Writer) command.Command {
 
 	return c
 }
-
-func runApp(config *hst.Config) {
-	ctx, stop := signal.NotifyContext(context.Background(),
-		syscall.SIGINT, syscall.SIGTERM)
-	defer stop() // unreachable
-	a := app.MustNew(ctx, std)
-
-	rs := new(app.RunState)
-	if sa, err := a.Seal(config); err != nil {
-		hlog.PrintBaseError(err, "cannot seal app:")
-		internal.Exit(1)
-	} else {
-		internal.Exit(app.PrintRunStateErr(rs, sa.Run(rs)))
-	}
-
-	*(*int)(nil) = 0 // not reached
-}

cmd/hakurei/command_test.go

@@ -68,7 +68,7 @@ Flags:
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
 			out := new(bytes.Buffer)
-			c := buildCommand(out)
+			c := buildCommand(t.Context(), out)
 			if err := c.Parse(tc.args); !errors.Is(err, command.ErrHelp) && !errors.Is(err, flag.ErrHelp) {
 				t.Errorf("Parse: error = %v; want %v",
 					err, command.ErrHelp)

cmd/hakurei/main.go

@@ -4,15 +4,17 @@ package main
 //go:generate cp ../../LICENSE .
 
 import (
+	"context"
 	_ "embed"
 	"errors"
 	"log"
 	"os"
+	"os/signal"
+	"syscall"
 
 	"hakurei.app/container"
 	"hakurei.app/internal"
 	"hakurei.app/internal/hlog"
-	"hakurei.app/internal/sys"
 )
 
 var (
@@ -24,8 +26,6 @@ var (
 
 func init() { hlog.Prepare("hakurei") }
 
-var std sys.State = new(sys.Std)
-
 func main() {
 	// early init path, skips root check and duplicate PR_SET_DUMPABLE
 	container.TryArgv0(hlog.Output{}, hlog.Prepare, internal.InstallOutput)
@@ -44,7 +44,11 @@ func main() {
 		log.Fatal("this program must not run as root")
 	}
 
-	buildCommand(os.Stderr).MustParse(os.Args[1:], func(err error) {
+	ctx, stop := signal.NotifyContext(context.Background(),
+		syscall.SIGINT, syscall.SIGTERM)
+	defer stop() // unreachable
+
+	buildCommand(ctx, os.Stderr).MustParse(os.Args[1:], func(err error) {
 		hlog.Verbosef("command returned %v", err)
 		if errors.Is(err, errSuccess) {
 			hlog.BeforeExit()

cmd/hakurei/parse.go

@@ -11,6 +11,7 @@ import (
 	"syscall"
 
 	"hakurei.app/hst"
+	"hakurei.app/internal/app"
 	"hakurei.app/internal/app/state"
 	"hakurei.app/internal/hlog"
 )
@@ -87,7 +88,9 @@ func tryShort(name string) (config *hst.Config, entry *state.State) {
 	if likePrefix && len(name) >= 8 {
 		hlog.Verbose("argument looks like prefix")
 
-		s := state.NewMulti(std.Paths().RunDirPath.String())
+		var sc hst.Paths
+		app.CopyPaths(&sc, new(app.Hsu).MustID())
+		s := state.NewMulti(sc.RunDirPath.String())
 		if entries, err := state.Join(s); err != nil {
 			log.Printf("cannot join store: %v", err)
 			// drop to fetch from file

cmd/hakurei/print.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"io"
 	"log"
-	"os"
 	"slices"
 	"strconv"
 	"strings"
@@ -13,8 +12,8 @@ import (
 	"time"
 
 	"hakurei.app/hst"
+	"hakurei.app/internal/app"
 	"hakurei.app/internal/app/state"
-	"hakurei.app/internal/hlog"
 	"hakurei.app/system/dbus"
 )
 
@@ -22,15 +21,8 @@ func printShowSystem(output io.Writer, short, flagJSON bool) {
 	t := newPrinter(output)
 	defer t.MustFlush()
 
-	info := &hst.Info{Paths: std.Paths()}
+	info := &hst.Info{User: new(app.Hsu).MustID()}
-
+	app.CopyPaths(&info.Paths, info.User)
-	// get hid by querying uid of identity 0
-	if uid, err := std.Uid(0); err != nil {
-		hlog.PrintBaseError(err, "cannot obtain uid from setuid wrapper:")
-		os.Exit(1)
-	} else {
-		info.User = (uid / 10000) - 100
-	}
 
 	if flagJSON {
 		printJSON(output, short, info)

cmd/hsu/main.go

@@ -15,7 +15,7 @@ import (
 const (
 	hsuConfFile = "/etc/hsurc"
 	envShim     = "HAKUREI_SHIM"
-	envAID      = "HAKUREI_APP_ID"
+	envIdentity = "HAKUREI_IDENTITY"
 	envGroups   = "HAKUREI_GROUPS"
 
 	PR_SET_NO_NEW_PRIVS = 0x26
@@ -48,8 +48,8 @@ func main() {
 	}
 
 	// uid = 1000000 +
-	//   fid * 10000 +
+	//    id * 10000 +
-	//           aid
+	//      identity
 	uid := 1000000
 
 	// refuse to run if hsurc is not protected correctly
@@ -62,29 +62,25 @@ func main() {
 	}
 
 	// authenticate before accepting user input
+	var id int
 	if f, err := os.Open(hsuConfFile); err != nil {
 		log.Fatal(err)
-	} else if fid, ok := mustParseConfig(f, puid); !ok {
+	} else if v, ok := mustParseConfig(f, puid); !ok {
 		log.Fatalf("uid %d is not in the hsurc file", puid)
 	} else {
-		uid += fid * 10000
+		id = v
-	}
+		if err = f.Close(); err != nil {
+			log.Fatal(err)
+		}
 
-	// allowed aid range 0 to 9999
+		uid += id * 10000
-	if as, ok := os.LookupEnv(envAID); !ok {
-		log.Fatal("HAKUREI_APP_ID not set")
-	} else if aid, err := parseUint32Fast(as); err != nil || aid < 0 || aid > 9999 {
-		log.Fatal("invalid aid")
-	} else {
-		uid += aid
 	}
 
 	// pass through setup fd to shim
 	var shimSetupFd string
 	if s, ok := os.LookupEnv(envShim); !ok {
-		// hakurei requests target uid
+		// hakurei requests hsurc user id
-		// print resolved uid and exit
+		fmt.Print(id)
-		fmt.Print(uid)
 		os.Exit(0)
 	} else if len(s) != 1 || s[0] > '9' || s[0] < '3' {
 		log.Fatal("HAKUREI_SHIM holds an invalid value")
@@ -92,6 +88,15 @@ func main() {
 		shimSetupFd = s
 	}
 
+	// allowed identity range 0 to 9999
+	if as, ok := os.LookupEnv(envIdentity); !ok {
+		log.Fatal("HAKUREI_IDENTITY not set")
+	} else if identity, err := parseUint32Fast(as); err != nil || identity < 0 || identity > 9999 {
+		log.Fatal("invalid identity")
+	} else {
+		uid += identity
+	}
+
 	// supplementary groups
 	var suppGroups, suppCurrent []int
 

container/autoetc.go

@@ -3,7 +3,6 @@ package container
 import (
 	"encoding/gob"
 	"fmt"
-	"io/fs"
 )
 
 func init() { gob.Register(new(AutoEtcOp)) }
@@ -24,7 +23,7 @@ func (e *AutoEtcOp) Valid() bool                                { return e != ni
 func (e *AutoEtcOp) early(*setupState, syscallDispatcher) error { return nil }
 func (e *AutoEtcOp) apply(state *setupState, k syscallDispatcher) error {
 	if state.nonrepeatable&nrAutoEtc != 0 {
-		return msg.WrapErr(fs.ErrInvalid, "autoetc is not repeatable")
+		return OpRepeatError("autoetc")
 	}
 	state.nonrepeatable |= nrAutoEtc
 
@@ -32,10 +31,10 @@ func (e *AutoEtcOp) apply(state *setupState, k syscallDispatcher) error {
 	rel := e.hostRel() + "/"
 
 	if err := k.mkdirAll(target, 0755); err != nil {
-		return wrapErrSelf(err)
+		return err
 	}
 	if d, err := k.readdir(toSysroot(e.hostPath().String())); err != nil {
-		return wrapErrSelf(err)
+		return err
 	} else {
 		for _, ent := range d {
 			n := ent.Name()
@@ -44,12 +43,12 @@ func (e *AutoEtcOp) apply(state *setupState, k syscallDispatcher) error {
 
 			case "mtab":
 				if err = k.symlink(FHSProc+"mounts", target+n); err != nil {
-					return wrapErrSelf(err)
+					return err
 				}
 
 			default:
 				if err = k.symlink(rel+n, target+n); err != nil {
-					return wrapErrSelf(err)
+					return err
 				}
 			}
 		}
@@ -65,5 +64,5 @@ func (e *AutoEtcOp) Is(op Op) bool {
 	ve, ok := op.(*AutoEtcOp)
 	return ok && e.Valid() && ve.Valid() && *e == *ve
 }
-func (*AutoEtcOp) prefix() string   { return "setting up" }
+func (*AutoEtcOp) prefix() (string, bool) { return "setting up", true }
-func (e *AutoEtcOp) String() string { return fmt.Sprintf("auto etc %s", e.Prefix) }
+func (e *AutoEtcOp) String() string       { return fmt.Sprintf("auto etc %s", e.Prefix) }

container/autoetc_test.go

@@ -2,14 +2,15 @@ package container
 
 import (
 	"errors"
-	"io/fs"
 	"os"
 	"testing"
+
+	"hakurei.app/container/stub"
 )
 
 func TestAutoEtcOp(t *testing.T) {
 	t.Run("nonrepeatable", func(t *testing.T) {
-		wantErr := msg.WrapErr(fs.ErrInvalid, "autoetc is not repeatable")
+		wantErr := OpRepeatError("autoetc")
 		if err := (&AutoEtcOp{Prefix: "81ceabb30d37bbdb3868004629cb84e9"}).apply(&setupState{nonrepeatable: nrAutoEtc}, nil); !errors.Is(err, wantErr) {
 			t.Errorf("apply: error = %v, want %v", err, wantErr)
 		}
@@ -18,22 +19,22 @@ func TestAutoEtcOp(t *testing.T) {
 	checkOpBehaviour(t, []opBehaviourTestCase{
 		{"mkdirAll", new(Params), &AutoEtcOp{
 			Prefix: "81ceabb30d37bbdb3868004629cb84e9",
-		}, nil, nil, []kexpect{
+		}, nil, nil, []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot/etc/", os.FileMode(0755)}, nil, errUnique},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/etc/", os.FileMode(0755)}, nil, stub.UniqueError(3)),
-		}, wrapErrSelf(errUnique)},
+		}, stub.UniqueError(3)},
 
 		{"readdir", new(Params), &AutoEtcOp{
 			Prefix: "81ceabb30d37bbdb3868004629cb84e9",
-		}, nil, nil, []kexpect{
+		}, nil, nil, []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot/etc/", os.FileMode(0755)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/etc/", os.FileMode(0755)}, nil, nil),
-			{"readdir", expectArgs{"/sysroot/etc/.host/81ceabb30d37bbdb3868004629cb84e9"}, stubDir(), errUnique},
+			call("readdir", stub.ExpectArgs{"/sysroot/etc/.host/81ceabb30d37bbdb3868004629cb84e9"}, stubDir(), stub.UniqueError(2)),
-		}, wrapErrSelf(errUnique)},
+		}, stub.UniqueError(2)},
 
 		{"symlink", new(Params), &AutoEtcOp{
 			Prefix: "81ceabb30d37bbdb3868004629cb84e9",
-		}, nil, nil, []kexpect{
+		}, nil, nil, []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot/etc/", os.FileMode(0755)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/etc/", os.FileMode(0755)}, nil, nil),
-			{"readdir", expectArgs{"/sysroot/etc/.host/81ceabb30d37bbdb3868004629cb84e9"}, stubDir(".host",
+			call("readdir", stub.ExpectArgs{"/sysroot/etc/.host/81ceabb30d37bbdb3868004629cb84e9"}, stubDir(".host",
 				"alsa", "bash_logout", "bashrc", "binfmt.d", "dbus-1", "default", "dhcpcd.exit-hook", "fonts",
 				"fstab", "fuse.conf", "group", "host.conf", "hostname", "hosts", "hsurc", "inputrc", "issue", "kbd",
 				"locale.conf", "login.defs", "lsb-release", "lvm", "machine-id", "man_db.conf", "mdadm.conf",
@@ -41,15 +42,15 @@ func TestAutoEtcOp(t *testing.T) {
 				"nsswitch.conf", "os-release", "pam", "pam.d", "passwd", "pipewire", "pki", "polkit-1", "profile",
 				"protocols", "resolv.conf", "resolvconf.conf", "rpc", "services", "set-environment", "shadow", "shells",
 				"ssh", "ssl", "static", "subgid", "subuid", "sudoers", "sway", "sysctl.d", "systemd", "terminfo",
-				"tmpfiles.d", "udev", "vconsole.conf", "X11", "xdg", "zoneinfo"), nil},
+				"tmpfiles.d", "udev", "vconsole.conf", "X11", "xdg", "zoneinfo"), nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/alsa", "/sysroot/etc/alsa"}, nil, errUnique},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/alsa", "/sysroot/etc/alsa"}, nil, stub.UniqueError(1)),
-		}, wrapErrSelf(errUnique)},
+		}, stub.UniqueError(1)},
 
 		{"symlink mtab", new(Params), &AutoEtcOp{
 			Prefix: "81ceabb30d37bbdb3868004629cb84e9",
-		}, nil, nil, []kexpect{
+		}, nil, nil, []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot/etc/", os.FileMode(0755)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/etc/", os.FileMode(0755)}, nil, nil),
-			{"readdir", expectArgs{"/sysroot/etc/.host/81ceabb30d37bbdb3868004629cb84e9"}, stubDir(".host",
+			call("readdir", stub.ExpectArgs{"/sysroot/etc/.host/81ceabb30d37bbdb3868004629cb84e9"}, stubDir(".host",
 				"alsa", "bash_logout", "bashrc", "binfmt.d", "dbus-1", "default", "dhcpcd.exit-hook", "fonts",
 				"fstab", "fuse.conf", "group", "host.conf", "hostname", "hosts", "hsurc", "inputrc", "issue", "kbd",
 				"locale.conf", "login.defs", "lsb-release", "lvm", "machine-id", "man_db.conf", "mdadm.conf",
@@ -57,41 +58,41 @@ func TestAutoEtcOp(t *testing.T) {
 				"nsswitch.conf", "os-release", "pam", "pam.d", "passwd", "pipewire", "pki", "polkit-1", "profile",
 				"protocols", "resolv.conf", "resolvconf.conf", "rpc", "services", "set-environment", "shadow", "shells",
 				"ssh", "ssl", "static", "subgid", "subuid", "sudoers", "sway", "sysctl.d", "systemd", "terminfo",
-				"tmpfiles.d", "udev", "vconsole.conf", "X11", "xdg", "zoneinfo"), nil},
+				"tmpfiles.d", "udev", "vconsole.conf", "X11", "xdg", "zoneinfo"), nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/alsa", "/sysroot/etc/alsa"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/alsa", "/sysroot/etc/alsa"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/bash_logout", "/sysroot/etc/bash_logout"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/bash_logout", "/sysroot/etc/bash_logout"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/bashrc", "/sysroot/etc/bashrc"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/bashrc", "/sysroot/etc/bashrc"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/binfmt.d", "/sysroot/etc/binfmt.d"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/binfmt.d", "/sysroot/etc/binfmt.d"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/dbus-1", "/sysroot/etc/dbus-1"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/dbus-1", "/sysroot/etc/dbus-1"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/default", "/sysroot/etc/default"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/default", "/sysroot/etc/default"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/dhcpcd.exit-hook", "/sysroot/etc/dhcpcd.exit-hook"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/dhcpcd.exit-hook", "/sysroot/etc/dhcpcd.exit-hook"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/fonts", "/sysroot/etc/fonts"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/fonts", "/sysroot/etc/fonts"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/fstab", "/sysroot/etc/fstab"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/fstab", "/sysroot/etc/fstab"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/fuse.conf", "/sysroot/etc/fuse.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/fuse.conf", "/sysroot/etc/fuse.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/host.conf", "/sysroot/etc/host.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/host.conf", "/sysroot/etc/host.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/hostname", "/sysroot/etc/hostname"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/hostname", "/sysroot/etc/hostname"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/hosts", "/sysroot/etc/hosts"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/hosts", "/sysroot/etc/hosts"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/hsurc", "/sysroot/etc/hsurc"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/hsurc", "/sysroot/etc/hsurc"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/inputrc", "/sysroot/etc/inputrc"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/inputrc", "/sysroot/etc/inputrc"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/issue", "/sysroot/etc/issue"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/issue", "/sysroot/etc/issue"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/kbd", "/sysroot/etc/kbd"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/kbd", "/sysroot/etc/kbd"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/locale.conf", "/sysroot/etc/locale.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/locale.conf", "/sysroot/etc/locale.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/login.defs", "/sysroot/etc/login.defs"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/login.defs", "/sysroot/etc/login.defs"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/lsb-release", "/sysroot/etc/lsb-release"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/lsb-release", "/sysroot/etc/lsb-release"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/lvm", "/sysroot/etc/lvm"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/lvm", "/sysroot/etc/lvm"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/machine-id", "/sysroot/etc/machine-id"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/machine-id", "/sysroot/etc/machine-id"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/man_db.conf", "/sysroot/etc/man_db.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/man_db.conf", "/sysroot/etc/man_db.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/mdadm.conf", "/sysroot/etc/mdadm.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/mdadm.conf", "/sysroot/etc/mdadm.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/modprobe.d", "/sysroot/etc/modprobe.d"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/modprobe.d", "/sysroot/etc/modprobe.d"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/modules-load.d", "/sysroot/etc/modules-load.d"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/modules-load.d", "/sysroot/etc/modules-load.d"}, nil, nil),
-			{"symlink", expectArgs{"/proc/mounts", "/sysroot/etc/mtab"}, nil, errUnique},
+			call("symlink", stub.ExpectArgs{"/proc/mounts", "/sysroot/etc/mtab"}, nil, stub.UniqueError(0)),
-		}, wrapErrSelf(errUnique)},
+		}, stub.UniqueError(0)},
 
 		{"success nested", new(Params), &AutoEtcOp{
 			Prefix: "81ceabb30d37bbdb3868004629cb84e9",
-		}, nil, nil, []kexpect{
+		}, nil, nil, []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot/etc/", os.FileMode(0755)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/etc/", os.FileMode(0755)}, nil, nil),
-			{"readdir", expectArgs{"/sysroot/etc/.host/81ceabb30d37bbdb3868004629cb84e9"}, stubDir(".host",
+			call("readdir", stub.ExpectArgs{"/sysroot/etc/.host/81ceabb30d37bbdb3868004629cb84e9"}, stubDir(".host",
 				"alsa", "bash_logout", "bashrc", "binfmt.d", "dbus-1", "default", "dhcpcd.exit-hook", "fonts",
 				"fstab", "fuse.conf", "group", "host.conf", "hostname", "hosts", "hsurc", "inputrc", "issue", "kbd",
 				"locale.conf", "login.defs", "lsb-release", "lvm", "machine-id", "man_db.conf", "mdadm.conf",
@@ -99,79 +100,79 @@ func TestAutoEtcOp(t *testing.T) {
 				"nsswitch.conf", "os-release", "pam", "pam.d", "passwd", "pipewire", "pki", "polkit-1", "profile",
 				"protocols", "resolv.conf", "resolvconf.conf", "rpc", "services", "set-environment", "shadow", "shells",
 				"ssh", "ssl", "static", "subgid", "subuid", "sudoers", "sway", "sysctl.d", "systemd", "terminfo",
-				"tmpfiles.d", "udev", "vconsole.conf", "X11", "xdg", "zoneinfo"), nil},
+				"tmpfiles.d", "udev", "vconsole.conf", "X11", "xdg", "zoneinfo"), nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/alsa", "/sysroot/etc/alsa"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/alsa", "/sysroot/etc/alsa"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/bash_logout", "/sysroot/etc/bash_logout"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/bash_logout", "/sysroot/etc/bash_logout"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/bashrc", "/sysroot/etc/bashrc"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/bashrc", "/sysroot/etc/bashrc"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/binfmt.d", "/sysroot/etc/binfmt.d"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/binfmt.d", "/sysroot/etc/binfmt.d"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/dbus-1", "/sysroot/etc/dbus-1"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/dbus-1", "/sysroot/etc/dbus-1"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/default", "/sysroot/etc/default"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/default", "/sysroot/etc/default"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/dhcpcd.exit-hook", "/sysroot/etc/dhcpcd.exit-hook"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/dhcpcd.exit-hook", "/sysroot/etc/dhcpcd.exit-hook"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/fonts", "/sysroot/etc/fonts"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/fonts", "/sysroot/etc/fonts"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/fstab", "/sysroot/etc/fstab"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/fstab", "/sysroot/etc/fstab"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/fuse.conf", "/sysroot/etc/fuse.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/fuse.conf", "/sysroot/etc/fuse.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/host.conf", "/sysroot/etc/host.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/host.conf", "/sysroot/etc/host.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/hostname", "/sysroot/etc/hostname"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/hostname", "/sysroot/etc/hostname"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/hosts", "/sysroot/etc/hosts"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/hosts", "/sysroot/etc/hosts"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/hsurc", "/sysroot/etc/hsurc"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/hsurc", "/sysroot/etc/hsurc"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/inputrc", "/sysroot/etc/inputrc"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/inputrc", "/sysroot/etc/inputrc"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/issue", "/sysroot/etc/issue"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/issue", "/sysroot/etc/issue"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/kbd", "/sysroot/etc/kbd"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/kbd", "/sysroot/etc/kbd"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/locale.conf", "/sysroot/etc/locale.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/locale.conf", "/sysroot/etc/locale.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/login.defs", "/sysroot/etc/login.defs"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/login.defs", "/sysroot/etc/login.defs"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/lsb-release", "/sysroot/etc/lsb-release"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/lsb-release", "/sysroot/etc/lsb-release"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/lvm", "/sysroot/etc/lvm"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/lvm", "/sysroot/etc/lvm"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/machine-id", "/sysroot/etc/machine-id"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/machine-id", "/sysroot/etc/machine-id"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/man_db.conf", "/sysroot/etc/man_db.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/man_db.conf", "/sysroot/etc/man_db.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/mdadm.conf", "/sysroot/etc/mdadm.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/mdadm.conf", "/sysroot/etc/mdadm.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/modprobe.d", "/sysroot/etc/modprobe.d"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/modprobe.d", "/sysroot/etc/modprobe.d"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/modules-load.d", "/sysroot/etc/modules-load.d"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/modules-load.d", "/sysroot/etc/modules-load.d"}, nil, nil),
-			{"symlink", expectArgs{"/proc/mounts", "/sysroot/etc/mtab"}, nil, nil},
+			call("symlink", stub.ExpectArgs{"/proc/mounts", "/sysroot/etc/mtab"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/nanorc", "/sysroot/etc/nanorc"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/nanorc", "/sysroot/etc/nanorc"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/netgroup", "/sysroot/etc/netgroup"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/netgroup", "/sysroot/etc/netgroup"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/nix", "/sysroot/etc/nix"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/nix", "/sysroot/etc/nix"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/nixos", "/sysroot/etc/nixos"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/nixos", "/sysroot/etc/nixos"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/NIXOS", "/sysroot/etc/NIXOS"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/NIXOS", "/sysroot/etc/NIXOS"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/nscd.conf", "/sysroot/etc/nscd.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/nscd.conf", "/sysroot/etc/nscd.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/nsswitch.conf", "/sysroot/etc/nsswitch.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/nsswitch.conf", "/sysroot/etc/nsswitch.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/os-release", "/sysroot/etc/os-release"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/os-release", "/sysroot/etc/os-release"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/pam", "/sysroot/etc/pam"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/pam", "/sysroot/etc/pam"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/pam.d", "/sysroot/etc/pam.d"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/pam.d", "/sysroot/etc/pam.d"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/pipewire", "/sysroot/etc/pipewire"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/pipewire", "/sysroot/etc/pipewire"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/pki", "/sysroot/etc/pki"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/pki", "/sysroot/etc/pki"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/polkit-1", "/sysroot/etc/polkit-1"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/polkit-1", "/sysroot/etc/polkit-1"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/profile", "/sysroot/etc/profile"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/profile", "/sysroot/etc/profile"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/protocols", "/sysroot/etc/protocols"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/protocols", "/sysroot/etc/protocols"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/resolv.conf", "/sysroot/etc/resolv.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/resolv.conf", "/sysroot/etc/resolv.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/resolvconf.conf", "/sysroot/etc/resolvconf.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/resolvconf.conf", "/sysroot/etc/resolvconf.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/rpc", "/sysroot/etc/rpc"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/rpc", "/sysroot/etc/rpc"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/services", "/sysroot/etc/services"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/services", "/sysroot/etc/services"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/set-environment", "/sysroot/etc/set-environment"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/set-environment", "/sysroot/etc/set-environment"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/shadow", "/sysroot/etc/shadow"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/shadow", "/sysroot/etc/shadow"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/shells", "/sysroot/etc/shells"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/shells", "/sysroot/etc/shells"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/ssh", "/sysroot/etc/ssh"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/ssh", "/sysroot/etc/ssh"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/ssl", "/sysroot/etc/ssl"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/ssl", "/sysroot/etc/ssl"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/static", "/sysroot/etc/static"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/static", "/sysroot/etc/static"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/subgid", "/sysroot/etc/subgid"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/subgid", "/sysroot/etc/subgid"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/subuid", "/sysroot/etc/subuid"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/subuid", "/sysroot/etc/subuid"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/sudoers", "/sysroot/etc/sudoers"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/sudoers", "/sysroot/etc/sudoers"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/sway", "/sysroot/etc/sway"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/sway", "/sysroot/etc/sway"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/sysctl.d", "/sysroot/etc/sysctl.d"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/sysctl.d", "/sysroot/etc/sysctl.d"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/systemd", "/sysroot/etc/systemd"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/systemd", "/sysroot/etc/systemd"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/terminfo", "/sysroot/etc/terminfo"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/terminfo", "/sysroot/etc/terminfo"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/tmpfiles.d", "/sysroot/etc/tmpfiles.d"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/tmpfiles.d", "/sysroot/etc/tmpfiles.d"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/udev", "/sysroot/etc/udev"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/udev", "/sysroot/etc/udev"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/vconsole.conf", "/sysroot/etc/vconsole.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/vconsole.conf", "/sysroot/etc/vconsole.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/X11", "/sysroot/etc/X11"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/X11", "/sysroot/etc/X11"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/xdg", "/sysroot/etc/xdg"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/xdg", "/sysroot/etc/xdg"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/zoneinfo", "/sysroot/etc/zoneinfo"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/zoneinfo", "/sysroot/etc/zoneinfo"}, nil, nil),
 		}, nil},
 
 		{"success", new(Params), &AutoEtcOp{
 			Prefix: "81ceabb30d37bbdb3868004629cb84e9",
-		}, nil, nil, []kexpect{
+		}, nil, nil, []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot/etc/", os.FileMode(0755)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/etc/", os.FileMode(0755)}, nil, nil),
-			{"readdir", expectArgs{"/sysroot/etc/.host/81ceabb30d37bbdb3868004629cb84e9"}, stubDir(
+			call("readdir", stub.ExpectArgs{"/sysroot/etc/.host/81ceabb30d37bbdb3868004629cb84e9"}, stubDir(
 				"alsa", "bash_logout", "bashrc", "binfmt.d", "dbus-1", "default", "dhcpcd.exit-hook", "fonts",
 				"fstab", "fuse.conf", "group", "host.conf", "hostname", "hosts", "hsurc", "inputrc", "issue", "kbd",
 				"locale.conf", "login.defs", "lsb-release", "lvm", "machine-id", "man_db.conf", "mdadm.conf",
@@ -179,72 +180,72 @@ func TestAutoEtcOp(t *testing.T) {
 				"nsswitch.conf", "os-release", "pam", "pam.d", "passwd", "pipewire", "pki", "polkit-1", "profile",
 				"protocols", "resolv.conf", "resolvconf.conf", "rpc", "services", "set-environment", "shadow", "shells",
 				"ssh", "ssl", "static", "subgid", "subuid", "sudoers", "sway", "sysctl.d", "systemd", "terminfo",
-				"tmpfiles.d", "udev", "vconsole.conf", "X11", "xdg", "zoneinfo"), nil},
+				"tmpfiles.d", "udev", "vconsole.conf", "X11", "xdg", "zoneinfo"), nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/alsa", "/sysroot/etc/alsa"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/alsa", "/sysroot/etc/alsa"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/bash_logout", "/sysroot/etc/bash_logout"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/bash_logout", "/sysroot/etc/bash_logout"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/bashrc", "/sysroot/etc/bashrc"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/bashrc", "/sysroot/etc/bashrc"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/binfmt.d", "/sysroot/etc/binfmt.d"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/binfmt.d", "/sysroot/etc/binfmt.d"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/dbus-1", "/sysroot/etc/dbus-1"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/dbus-1", "/sysroot/etc/dbus-1"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/default", "/sysroot/etc/default"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/default", "/sysroot/etc/default"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/dhcpcd.exit-hook", "/sysroot/etc/dhcpcd.exit-hook"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/dhcpcd.exit-hook", "/sysroot/etc/dhcpcd.exit-hook"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/fonts", "/sysroot/etc/fonts"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/fonts", "/sysroot/etc/fonts"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/fstab", "/sysroot/etc/fstab"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/fstab", "/sysroot/etc/fstab"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/fuse.conf", "/sysroot/etc/fuse.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/fuse.conf", "/sysroot/etc/fuse.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/host.conf", "/sysroot/etc/host.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/host.conf", "/sysroot/etc/host.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/hostname", "/sysroot/etc/hostname"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/hostname", "/sysroot/etc/hostname"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/hosts", "/sysroot/etc/hosts"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/hosts", "/sysroot/etc/hosts"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/hsurc", "/sysroot/etc/hsurc"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/hsurc", "/sysroot/etc/hsurc"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/inputrc", "/sysroot/etc/inputrc"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/inputrc", "/sysroot/etc/inputrc"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/issue", "/sysroot/etc/issue"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/issue", "/sysroot/etc/issue"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/kbd", "/sysroot/etc/kbd"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/kbd", "/sysroot/etc/kbd"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/locale.conf", "/sysroot/etc/locale.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/locale.conf", "/sysroot/etc/locale.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/login.defs", "/sysroot/etc/login.defs"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/login.defs", "/sysroot/etc/login.defs"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/lsb-release", "/sysroot/etc/lsb-release"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/lsb-release", "/sysroot/etc/lsb-release"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/lvm", "/sysroot/etc/lvm"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/lvm", "/sysroot/etc/lvm"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/machine-id", "/sysroot/etc/machine-id"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/machine-id", "/sysroot/etc/machine-id"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/man_db.conf", "/sysroot/etc/man_db.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/man_db.conf", "/sysroot/etc/man_db.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/mdadm.conf", "/sysroot/etc/mdadm.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/mdadm.conf", "/sysroot/etc/mdadm.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/modprobe.d", "/sysroot/etc/modprobe.d"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/modprobe.d", "/sysroot/etc/modprobe.d"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/modules-load.d", "/sysroot/etc/modules-load.d"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/modules-load.d", "/sysroot/etc/modules-load.d"}, nil, nil),
-			{"symlink", expectArgs{"/proc/mounts", "/sysroot/etc/mtab"}, nil, nil},
+			call("symlink", stub.ExpectArgs{"/proc/mounts", "/sysroot/etc/mtab"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/nanorc", "/sysroot/etc/nanorc"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/nanorc", "/sysroot/etc/nanorc"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/netgroup", "/sysroot/etc/netgroup"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/netgroup", "/sysroot/etc/netgroup"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/nix", "/sysroot/etc/nix"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/nix", "/sysroot/etc/nix"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/nixos", "/sysroot/etc/nixos"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/nixos", "/sysroot/etc/nixos"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/NIXOS", "/sysroot/etc/NIXOS"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/NIXOS", "/sysroot/etc/NIXOS"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/nscd.conf", "/sysroot/etc/nscd.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/nscd.conf", "/sysroot/etc/nscd.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/nsswitch.conf", "/sysroot/etc/nsswitch.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/nsswitch.conf", "/sysroot/etc/nsswitch.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/os-release", "/sysroot/etc/os-release"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/os-release", "/sysroot/etc/os-release"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/pam", "/sysroot/etc/pam"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/pam", "/sysroot/etc/pam"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/pam.d", "/sysroot/etc/pam.d"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/pam.d", "/sysroot/etc/pam.d"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/pipewire", "/sysroot/etc/pipewire"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/pipewire", "/sysroot/etc/pipewire"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/pki", "/sysroot/etc/pki"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/pki", "/sysroot/etc/pki"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/polkit-1", "/sysroot/etc/polkit-1"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/polkit-1", "/sysroot/etc/polkit-1"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/profile", "/sysroot/etc/profile"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/profile", "/sysroot/etc/profile"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/protocols", "/sysroot/etc/protocols"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/protocols", "/sysroot/etc/protocols"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/resolv.conf", "/sysroot/etc/resolv.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/resolv.conf", "/sysroot/etc/resolv.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/resolvconf.conf", "/sysroot/etc/resolvconf.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/resolvconf.conf", "/sysroot/etc/resolvconf.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/rpc", "/sysroot/etc/rpc"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/rpc", "/sysroot/etc/rpc"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/services", "/sysroot/etc/services"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/services", "/sysroot/etc/services"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/set-environment", "/sysroot/etc/set-environment"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/set-environment", "/sysroot/etc/set-environment"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/shadow", "/sysroot/etc/shadow"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/shadow", "/sysroot/etc/shadow"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/shells", "/sysroot/etc/shells"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/shells", "/sysroot/etc/shells"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/ssh", "/sysroot/etc/ssh"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/ssh", "/sysroot/etc/ssh"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/ssl", "/sysroot/etc/ssl"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/ssl", "/sysroot/etc/ssl"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/static", "/sysroot/etc/static"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/static", "/sysroot/etc/static"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/subgid", "/sysroot/etc/subgid"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/subgid", "/sysroot/etc/subgid"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/subuid", "/sysroot/etc/subuid"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/subuid", "/sysroot/etc/subuid"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/sudoers", "/sysroot/etc/sudoers"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/sudoers", "/sysroot/etc/sudoers"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/sway", "/sysroot/etc/sway"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/sway", "/sysroot/etc/sway"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/sysctl.d", "/sysroot/etc/sysctl.d"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/sysctl.d", "/sysroot/etc/sysctl.d"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/systemd", "/sysroot/etc/systemd"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/systemd", "/sysroot/etc/systemd"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/terminfo", "/sysroot/etc/terminfo"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/terminfo", "/sysroot/etc/terminfo"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/tmpfiles.d", "/sysroot/etc/tmpfiles.d"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/tmpfiles.d", "/sysroot/etc/tmpfiles.d"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/udev", "/sysroot/etc/udev"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/udev", "/sysroot/etc/udev"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/vconsole.conf", "/sysroot/etc/vconsole.conf"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/vconsole.conf", "/sysroot/etc/vconsole.conf"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/X11", "/sysroot/etc/X11"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/X11", "/sysroot/etc/X11"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/xdg", "/sysroot/etc/xdg"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/xdg", "/sysroot/etc/xdg"}, nil, nil),
-			{"symlink", expectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/zoneinfo", "/sysroot/etc/zoneinfo"}, nil, nil},
+			call("symlink", stub.ExpectArgs{".host/81ceabb30d37bbdb3868004629cb84e9/zoneinfo", "/sysroot/etc/zoneinfo"}, nil, nil),
 		}, nil},
 	})
 

container/autoroot.go

@@ -3,7 +3,6 @@ package container
 import (
 	"encoding/gob"
 	"fmt"
-	"io/fs"
 )
 
 func init() { gob.Register(new(AutoRootOp)) }
@@ -23,19 +22,20 @@ type AutoRootOp struct {
 	// obtained during early;
 	// these wrap the underlying Op because BindMountOp is relatively complex,
 	// so duplicating that code would be unwise
-	resolved []Op
+	resolved []*BindMountOp
 }
 
 func (r *AutoRootOp) Valid() bool { return r != nil && r.Host != nil }
 
 func (r *AutoRootOp) early(state *setupState, k syscallDispatcher) error {
 	if d, err := k.readdir(r.Host.String()); err != nil {
-		return wrapErrSelf(err)
+		return err
 	} else {
-		r.resolved = make([]Op, 0, len(d))
+		r.resolved = make([]*BindMountOp, 0, len(d))
 		for _, ent := range d {
 			name := ent.Name()
 			if IsAutoRootBindable(name) {
+				// careful: the Valid method is skipped, make sure this is always valid
 				op := &BindMountOp{
 					Source: r.Host.Append(name),
 					Target: AbsFHSRoot.Append(name),
@@ -53,12 +53,12 @@ func (r *AutoRootOp) early(state *setupState, k syscallDispatcher) error {
 
 func (r *AutoRootOp) apply(state *setupState, k syscallDispatcher) error {
 	if state.nonrepeatable&nrAutoRoot != 0 {
-		return msg.WrapErr(fs.ErrInvalid, "autoroot is not repeatable")
+		return OpRepeatError("autoroot")
 	}
 	state.nonrepeatable |= nrAutoRoot
 
 	for _, op := range r.resolved {
-		k.verbosef("%s %s", op.prefix(), op)
+		// these are exclusively BindMountOp, do not attempt to print identifying message
 		if err := op.apply(state, k); err != nil {
 			return err
 		}
@@ -72,7 +72,7 @@ func (r *AutoRootOp) Is(op Op) bool {
 		r.Host.Is(vr.Host) &&
 		r.Flags == vr.Flags
 }
-func (*AutoRootOp) prefix() string { return "setting up" }
+func (*AutoRootOp) prefix() (string, bool) { return "setting up", true }
 func (r *AutoRootOp) String() string {
 	return fmt.Sprintf("auto root %q flags %#x", r.Host, r.Flags)
 }

container/autoroot_test.go

@@ -2,14 +2,15 @@ package container
 
 import (
 	"errors"
-	"io/fs"
 	"os"
 	"testing"
+
+	"hakurei.app/container/stub"
 )
 
 func TestAutoRootOp(t *testing.T) {
 	t.Run("nonrepeatable", func(t *testing.T) {
-		wantErr := msg.WrapErr(fs.ErrInvalid, "autoroot is not repeatable")
+		wantErr := OpRepeatError("autoroot")
 		if err := new(AutoRootOp).apply(&setupState{nonrepeatable: nrAutoRoot}, nil); !errors.Is(err, wantErr) {
 			t.Errorf("apply: error = %v, want %v", err, wantErr)
 		}
@@ -19,100 +20,99 @@ func TestAutoRootOp(t *testing.T) {
 		{"readdir", &Params{ParentPerm: 0750}, &AutoRootOp{
 			Host:  MustAbs("/"),
 			Flags: BindWritable,
-		}, []kexpect{
+		}, []stub.Call{
-			{"readdir", expectArgs{"/"}, stubDir(), errUnique},
+			call("readdir", stub.ExpectArgs{"/"}, stubDir(), stub.UniqueError(2)),
-		}, wrapErrSelf(errUnique), nil, nil},
+		}, stub.UniqueError(2), nil, nil},
 
 		{"early", &Params{ParentPerm: 0750}, &AutoRootOp{
 			Host:  MustAbs("/"),
 			Flags: BindWritable,
-		}, []kexpect{
+		}, []stub.Call{
-			{"readdir", expectArgs{"/"}, stubDir("bin", "dev", "etc", "home", "lib64",
+			call("readdir", stub.ExpectArgs{"/"}, stubDir("bin", "dev", "etc", "home", "lib64",
-				"lost+found", "mnt", "nix", "proc", "root", "run", "srv", "sys", "tmp", "usr", "var"), nil},
+				"lost+found", "mnt", "nix", "proc", "root", "run", "srv", "sys", "tmp", "usr", "var"), nil),
-			{"evalSymlinks", expectArgs{"/bin"}, "", errUnique},
+			call("evalSymlinks", stub.ExpectArgs{"/bin"}, "", stub.UniqueError(1)),
-		}, wrapErrSelf(errUnique), nil, nil},
+		}, stub.UniqueError(1), nil, nil},
 
 		{"apply", &Params{ParentPerm: 0750}, &AutoRootOp{
 			Host:  MustAbs("/"),
 			Flags: BindWritable,
-		}, []kexpect{
+		}, []stub.Call{
-			{"readdir", expectArgs{"/"}, stubDir("bin", "dev", "etc", "home", "lib64",
+			call("readdir", stub.ExpectArgs{"/"}, stubDir("bin", "dev", "etc", "home", "lib64",
-				"lost+found", "mnt", "nix", "proc", "root", "run", "srv", "sys", "tmp", "usr", "var"), nil},
+				"lost+found", "mnt", "nix", "proc", "root", "run", "srv", "sys", "tmp", "usr", "var"), nil),
-			{"evalSymlinks", expectArgs{"/bin"}, "/usr/bin", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/bin"}, "/usr/bin", nil),
-			{"evalSymlinks", expectArgs{"/home"}, "/home", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/home"}, "/home", nil),
-			{"evalSymlinks", expectArgs{"/lib64"}, "/lib64", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/lib64"}, "/lib64", nil),
-			{"evalSymlinks", expectArgs{"/lost+found"}, "/lost+found", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/lost+found"}, "/lost+found", nil),
-			{"evalSymlinks", expectArgs{"/nix"}, "/nix", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/nix"}, "/nix", nil),
-			{"evalSymlinks", expectArgs{"/root"}, "/root", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/root"}, "/root", nil),
-			{"evalSymlinks", expectArgs{"/run"}, "/run", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/run"}, "/run", nil),
-			{"evalSymlinks", expectArgs{"/srv"}, "/srv", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/srv"}, "/srv", nil),
-			{"evalSymlinks", expectArgs{"/sys"}, "/sys", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/sys"}, "/sys", nil),
-			{"evalSymlinks", expectArgs{"/usr"}, "/usr", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/usr"}, "/usr", nil),
-			{"evalSymlinks", expectArgs{"/var"}, "/var", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/var"}, "/var", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/usr/bin"), MustAbs("/bin"), MustAbs("/bin"), BindWritable}}}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/usr/bin"}, isDirFi(false), stub.UniqueError(0)),
-			{"stat", expectArgs{"/host/usr/bin"}, isDirFi(false), errUnique},
+		}, stub.UniqueError(0)},
-		}, wrapErrSelf(errUnique)},
 
 		{"success pd", &Params{ParentPerm: 0750}, &AutoRootOp{
 			Host:  MustAbs("/"),
 			Flags: BindWritable,
-		}, []kexpect{
+		}, []stub.Call{
-			{"readdir", expectArgs{"/"}, stubDir("bin", "dev", "etc", "home", "lib64",
+			call("readdir", stub.ExpectArgs{"/"}, stubDir("bin", "dev", "etc", "home", "lib64",
-				"lost+found", "mnt", "nix", "proc", "root", "run", "srv", "sys", "tmp", "usr", "var"), nil},
+				"lost+found", "mnt", "nix", "proc", "root", "run", "srv", "sys", "tmp", "usr", "var"), nil),
-			{"evalSymlinks", expectArgs{"/bin"}, "/usr/bin", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/bin"}, "/usr/bin", nil),
-			{"evalSymlinks", expectArgs{"/home"}, "/home", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/home"}, "/home", nil),
-			{"evalSymlinks", expectArgs{"/lib64"}, "/lib64", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/lib64"}, "/lib64", nil),
-			{"evalSymlinks", expectArgs{"/lost+found"}, "/lost+found", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/lost+found"}, "/lost+found", nil),
-			{"evalSymlinks", expectArgs{"/nix"}, "/nix", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/nix"}, "/nix", nil),
-			{"evalSymlinks", expectArgs{"/root"}, "/root", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/root"}, "/root", nil),
-			{"evalSymlinks", expectArgs{"/run"}, "/run", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/run"}, "/run", nil),
-			{"evalSymlinks", expectArgs{"/srv"}, "/srv", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/srv"}, "/srv", nil),
-			{"evalSymlinks", expectArgs{"/sys"}, "/sys", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/sys"}, "/sys", nil),
-			{"evalSymlinks", expectArgs{"/usr"}, "/usr", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/usr"}, "/usr", nil),
-			{"evalSymlinks", expectArgs{"/var"}, "/var", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/var"}, "/var", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/usr/bin"), MustAbs("/bin"), MustAbs("/bin"), BindWritable}}}, nil, nil}, {"stat", expectArgs{"/host/usr/bin"}, isDirFi(true), nil}, {"mkdirAll", expectArgs{"/sysroot/bin", os.FileMode(0700)}, nil, nil}, {"bindMount", expectArgs{"/host/usr/bin", "/sysroot/bin", uintptr(0x4004), false}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/usr/bin"}, isDirFi(true), nil), call("mkdirAll", stub.ExpectArgs{"/sysroot/bin", os.FileMode(0700)}, nil, nil), call("verbosef", stub.ExpectArgs{"mounting %q on %q flags %#x", []any{"/host/usr/bin", "/sysroot/bin", uintptr(0x4004)}}, nil, nil), call("bindMount", stub.ExpectArgs{"/host/usr/bin", "/sysroot/bin", uintptr(0x4004), false}, nil, nil),
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/home"), MustAbs("/home"), MustAbs("/home"), BindWritable}}}, nil, nil}, {"stat", expectArgs{"/host/home"}, isDirFi(true), nil}, {"mkdirAll", expectArgs{"/sysroot/home", os.FileMode(0700)}, nil, nil}, {"bindMount", expectArgs{"/host/home", "/sysroot/home", uintptr(0x4004), false}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/home"}, isDirFi(true), nil), call("mkdirAll", stub.ExpectArgs{"/sysroot/home", os.FileMode(0700)}, nil, nil), call("verbosef", stub.ExpectArgs{"mounting %q flags %#x", []any{"/sysroot/home", uintptr(0x4004)}}, nil, nil), call("bindMount", stub.ExpectArgs{"/host/home", "/sysroot/home", uintptr(0x4004), false}, nil, nil),
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/lib64"), MustAbs("/lib64"), MustAbs("/lib64"), BindWritable}}}, nil, nil}, {"stat", expectArgs{"/host/lib64"}, isDirFi(true), nil}, {"mkdirAll", expectArgs{"/sysroot/lib64", os.FileMode(0700)}, nil, nil}, {"bindMount", expectArgs{"/host/lib64", "/sysroot/lib64", uintptr(0x4004), false}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/lib64"}, isDirFi(true), nil), call("mkdirAll", stub.ExpectArgs{"/sysroot/lib64", os.FileMode(0700)}, nil, nil), call("verbosef", stub.ExpectArgs{"mounting %q flags %#x", []any{"/sysroot/lib64", uintptr(0x4004)}}, nil, nil), call("bindMount", stub.ExpectArgs{"/host/lib64", "/sysroot/lib64", uintptr(0x4004), false}, nil, nil),
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/lost+found"), MustAbs("/lost+found"), MustAbs("/lost+found"), BindWritable}}}, nil, nil}, {"stat", expectArgs{"/host/lost+found"}, isDirFi(true), nil}, {"mkdirAll", expectArgs{"/sysroot/lost+found", os.FileMode(0700)}, nil, nil}, {"bindMount", expectArgs{"/host/lost+found", "/sysroot/lost+found", uintptr(0x4004), false}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/lost+found"}, isDirFi(true), nil), call("mkdirAll", stub.ExpectArgs{"/sysroot/lost+found", os.FileMode(0700)}, nil, nil), call("verbosef", stub.ExpectArgs{"mounting %q flags %#x", []any{"/sysroot/lost+found", uintptr(0x4004)}}, nil, nil), call("bindMount", stub.ExpectArgs{"/host/lost+found", "/sysroot/lost+found", uintptr(0x4004), false}, nil, nil),
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/nix"), MustAbs("/nix"), MustAbs("/nix"), BindWritable}}}, nil, nil}, {"stat", expectArgs{"/host/nix"}, isDirFi(true), nil}, {"mkdirAll", expectArgs{"/sysroot/nix", os.FileMode(0700)}, nil, nil}, {"bindMount", expectArgs{"/host/nix", "/sysroot/nix", uintptr(0x4004), false}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/nix"}, isDirFi(true), nil), call("mkdirAll", stub.ExpectArgs{"/sysroot/nix", os.FileMode(0700)}, nil, nil), call("verbosef", stub.ExpectArgs{"mounting %q flags %#x", []any{"/sysroot/nix", uintptr(0x4004)}}, nil, nil), call("bindMount", stub.ExpectArgs{"/host/nix", "/sysroot/nix", uintptr(0x4004), false}, nil, nil),
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/root"), MustAbs("/root"), MustAbs("/root"), BindWritable}}}, nil, nil}, {"stat", expectArgs{"/host/root"}, isDirFi(true), nil}, {"mkdirAll", expectArgs{"/sysroot/root", os.FileMode(0700)}, nil, nil}, {"bindMount", expectArgs{"/host/root", "/sysroot/root", uintptr(0x4004), false}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/root"}, isDirFi(true), nil), call("mkdirAll", stub.ExpectArgs{"/sysroot/root", os.FileMode(0700)}, nil, nil), call("verbosef", stub.ExpectArgs{"mounting %q flags %#x", []any{"/sysroot/root", uintptr(0x4004)}}, nil, nil), call("bindMount", stub.ExpectArgs{"/host/root", "/sysroot/root", uintptr(0x4004), false}, nil, nil),
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/run"), MustAbs("/run"), MustAbs("/run"), BindWritable}}}, nil, nil}, {"stat", expectArgs{"/host/run"}, isDirFi(true), nil}, {"mkdirAll", expectArgs{"/sysroot/run", os.FileMode(0700)}, nil, nil}, {"bindMount", expectArgs{"/host/run", "/sysroot/run", uintptr(0x4004), false}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/run"}, isDirFi(true), nil), call("mkdirAll", stub.ExpectArgs{"/sysroot/run", os.FileMode(0700)}, nil, nil), call("verbosef", stub.ExpectArgs{"mounting %q flags %#x", []any{"/sysroot/run", uintptr(0x4004)}}, nil, nil), call("bindMount", stub.ExpectArgs{"/host/run", "/sysroot/run", uintptr(0x4004), false}, nil, nil),
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/srv"), MustAbs("/srv"), MustAbs("/srv"), BindWritable}}}, nil, nil}, {"stat", expectArgs{"/host/srv"}, isDirFi(true), nil}, {"mkdirAll", expectArgs{"/sysroot/srv", os.FileMode(0700)}, nil, nil}, {"bindMount", expectArgs{"/host/srv", "/sysroot/srv", uintptr(0x4004), false}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/srv"}, isDirFi(true), nil), call("mkdirAll", stub.ExpectArgs{"/sysroot/srv", os.FileMode(0700)}, nil, nil), call("verbosef", stub.ExpectArgs{"mounting %q flags %#x", []any{"/sysroot/srv", uintptr(0x4004)}}, nil, nil), call("bindMount", stub.ExpectArgs{"/host/srv", "/sysroot/srv", uintptr(0x4004), false}, nil, nil),
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/sys"), MustAbs("/sys"), MustAbs("/sys"), BindWritable}}}, nil, nil}, {"stat", expectArgs{"/host/sys"}, isDirFi(true), nil}, {"mkdirAll", expectArgs{"/sysroot/sys", os.FileMode(0700)}, nil, nil}, {"bindMount", expectArgs{"/host/sys", "/sysroot/sys", uintptr(0x4004), false}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/sys"}, isDirFi(true), nil), call("mkdirAll", stub.ExpectArgs{"/sysroot/sys", os.FileMode(0700)}, nil, nil), call("verbosef", stub.ExpectArgs{"mounting %q flags %#x", []any{"/sysroot/sys", uintptr(0x4004)}}, nil, nil), call("bindMount", stub.ExpectArgs{"/host/sys", "/sysroot/sys", uintptr(0x4004), false}, nil, nil),
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/usr"), MustAbs("/usr"), MustAbs("/usr"), BindWritable}}}, nil, nil}, {"stat", expectArgs{"/host/usr"}, isDirFi(true), nil}, {"mkdirAll", expectArgs{"/sysroot/usr", os.FileMode(0700)}, nil, nil}, {"bindMount", expectArgs{"/host/usr", "/sysroot/usr", uintptr(0x4004), false}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/usr"}, isDirFi(true), nil), call("mkdirAll", stub.ExpectArgs{"/sysroot/usr", os.FileMode(0700)}, nil, nil), call("verbosef", stub.ExpectArgs{"mounting %q flags %#x", []any{"/sysroot/usr", uintptr(0x4004)}}, nil, nil), call("bindMount", stub.ExpectArgs{"/host/usr", "/sysroot/usr", uintptr(0x4004), false}, nil, nil),
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/var"), MustAbs("/var"), MustAbs("/var"), BindWritable}}}, nil, nil}, {"stat", expectArgs{"/host/var"}, isDirFi(true), nil}, {"mkdirAll", expectArgs{"/sysroot/var", os.FileMode(0700)}, nil, nil}, {"bindMount", expectArgs{"/host/var", "/sysroot/var", uintptr(0x4004), false}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/var"}, isDirFi(true), nil), call("mkdirAll", stub.ExpectArgs{"/sysroot/var", os.FileMode(0700)}, nil, nil), call("verbosef", stub.ExpectArgs{"mounting %q flags %#x", []any{"/sysroot/var", uintptr(0x4004)}}, nil, nil), call("bindMount", stub.ExpectArgs{"/host/var", "/sysroot/var", uintptr(0x4004), false}, nil, nil),
 		}, nil},
 
 		{"success", &Params{ParentPerm: 0750}, &AutoRootOp{
 			Host: MustAbs("/var/lib/planterette/base/debian:f92c9052"),
-		}, []kexpect{
+		}, []stub.Call{
-			{"readdir", expectArgs{"/var/lib/planterette/base/debian:f92c9052"}, stubDir("bin", "dev", "etc", "home", "lib64",
+			call("readdir", stub.ExpectArgs{"/var/lib/planterette/base/debian:f92c9052"}, stubDir("bin", "dev", "etc", "home", "lib64",
-				"lost+found", "mnt", "nix", "proc", "root", "run", "srv", "sys", "tmp", "usr", "var"), nil},
+				"lost+found", "mnt", "nix", "proc", "root", "run", "srv", "sys", "tmp", "usr", "var"), nil),
-			{"evalSymlinks", expectArgs{"/var/lib/planterette/base/debian:f92c9052/bin"}, "/var/lib/planterette/base/debian:f92c9052/usr/bin", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/var/lib/planterette/base/debian:f92c9052/bin"}, "/var/lib/planterette/base/debian:f92c9052/usr/bin", nil),
-			{"evalSymlinks", expectArgs{"/var/lib/planterette/base/debian:f92c9052/home"}, "/var/lib/planterette/base/debian:f92c9052/home", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/var/lib/planterette/base/debian:f92c9052/home"}, "/var/lib/planterette/base/debian:f92c9052/home", nil),
-			{"evalSymlinks", expectArgs{"/var/lib/planterette/base/debian:f92c9052/lib64"}, "/var/lib/planterette/base/debian:f92c9052/lib64", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/var/lib/planterette/base/debian:f92c9052/lib64"}, "/var/lib/planterette/base/debian:f92c9052/lib64", nil),
-			{"evalSymlinks", expectArgs{"/var/lib/planterette/base/debian:f92c9052/lost+found"}, "/var/lib/planterette/base/debian:f92c9052/lost+found", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/var/lib/planterette/base/debian:f92c9052/lost+found"}, "/var/lib/planterette/base/debian:f92c9052/lost+found", nil),
-			{"evalSymlinks", expectArgs{"/var/lib/planterette/base/debian:f92c9052/nix"}, "/var/lib/planterette/base/debian:f92c9052/nix", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/var/lib/planterette/base/debian:f92c9052/nix"}, "/var/lib/planterette/base/debian:f92c9052/nix", nil),
-			{"evalSymlinks", expectArgs{"/var/lib/planterette/base/debian:f92c9052/root"}, "/var/lib/planterette/base/debian:f92c9052/root", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/var/lib/planterette/base/debian:f92c9052/root"}, "/var/lib/planterette/base/debian:f92c9052/root", nil),
-			{"evalSymlinks", expectArgs{"/var/lib/planterette/base/debian:f92c9052/run"}, "/var/lib/planterette/base/debian:f92c9052/run", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/var/lib/planterette/base/debian:f92c9052/run"}, "/var/lib/planterette/base/debian:f92c9052/run", nil),
-			{"evalSymlinks", expectArgs{"/var/lib/planterette/base/debian:f92c9052/srv"}, "/var/lib/planterette/base/debian:f92c9052/srv", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/var/lib/planterette/base/debian:f92c9052/srv"}, "/var/lib/planterette/base/debian:f92c9052/srv", nil),
-			{"evalSymlinks", expectArgs{"/var/lib/planterette/base/debian:f92c9052/sys"}, "/var/lib/planterette/base/debian:f92c9052/sys", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/var/lib/planterette/base/debian:f92c9052/sys"}, "/var/lib/planterette/base/debian:f92c9052/sys", nil),
-			{"evalSymlinks", expectArgs{"/var/lib/planterette/base/debian:f92c9052/usr"}, "/var/lib/planterette/base/debian:f92c9052/usr", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/var/lib/planterette/base/debian:f92c9052/usr"}, "/var/lib/planterette/base/debian:f92c9052/usr", nil),
-			{"evalSymlinks", expectArgs{"/var/lib/planterette/base/debian:f92c9052/var"}, "/var/lib/planterette/base/debian:f92c9052/var", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/var/lib/planterette/base/debian:f92c9052/var"}, "/var/lib/planterette/base/debian:f92c9052/var", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/var/lib/planterette/base/debian:f92c9052/usr/bin"), MustAbs("/var/lib/planterette/base/debian:f92c9052/bin"), MustAbs("/bin"), 0}}}, nil, nil}, {"stat", expectArgs{"/host/var/lib/planterette/base/debian:f92c9052/usr/bin"}, isDirFi(true), nil}, {"mkdirAll", expectArgs{"/sysroot/bin", os.FileMode(0700)}, nil, nil}, {"bindMount", expectArgs{"/host/var/lib/planterette/base/debian:f92c9052/usr/bin", "/sysroot/bin", uintptr(0x4005), false}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/var/lib/planterette/base/debian:f92c9052/usr/bin"}, isDirFi(true), nil), call("mkdirAll", stub.ExpectArgs{"/sysroot/bin", os.FileMode(0700)}, nil, nil), call("verbosef", stub.ExpectArgs{"mounting %q on %q flags %#x", []any{"/host/var/lib/planterette/base/debian:f92c9052/usr/bin", "/sysroot/bin", uintptr(0x4005)}}, nil, nil), call("bindMount", stub.ExpectArgs{"/host/var/lib/planterette/base/debian:f92c9052/usr/bin", "/sysroot/bin", uintptr(0x4005), false}, nil, nil),
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/var/lib/planterette/base/debian:f92c9052/home"), MustAbs("/var/lib/planterette/base/debian:f92c9052/home"), MustAbs("/home"), 0}}}, nil, nil}, {"stat", expectArgs{"/host/var/lib/planterette/base/debian:f92c9052/home"}, isDirFi(true), nil}, {"mkdirAll", expectArgs{"/sysroot/home", os.FileMode(0700)}, nil, nil}, {"bindMount", expectArgs{"/host/var/lib/planterette/base/debian:f92c9052/home", "/sysroot/home", uintptr(0x4005), false}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/var/lib/planterette/base/debian:f92c9052/home"}, isDirFi(true), nil), call("mkdirAll", stub.ExpectArgs{"/sysroot/home", os.FileMode(0700)}, nil, nil), call("verbosef", stub.ExpectArgs{"mounting %q on %q flags %#x", []any{"/host/var/lib/planterette/base/debian:f92c9052/home", "/sysroot/home", uintptr(0x4005)}}, nil, nil), call("bindMount", stub.ExpectArgs{"/host/var/lib/planterette/base/debian:f92c9052/home", "/sysroot/home", uintptr(0x4005), false}, nil, nil),
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/var/lib/planterette/base/debian:f92c9052/lib64"), MustAbs("/var/lib/planterette/base/debian:f92c9052/lib64"), MustAbs("/lib64"), 0}}}, nil, nil}, {"stat", expectArgs{"/host/var/lib/planterette/base/debian:f92c9052/lib64"}, isDirFi(true), nil}, {"mkdirAll", expectArgs{"/sysroot/lib64", os.FileMode(0700)}, nil, nil}, {"bindMount", expectArgs{"/host/var/lib/planterette/base/debian:f92c9052/lib64", "/sysroot/lib64", uintptr(0x4005), false}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/var/lib/planterette/base/debian:f92c9052/lib64"}, isDirFi(true), nil), call("mkdirAll", stub.ExpectArgs{"/sysroot/lib64", os.FileMode(0700)}, nil, nil), call("verbosef", stub.ExpectArgs{"mounting %q on %q flags %#x", []any{"/host/var/lib/planterette/base/debian:f92c9052/lib64", "/sysroot/lib64", uintptr(0x4005)}}, nil, nil), call("bindMount", stub.ExpectArgs{"/host/var/lib/planterette/base/debian:f92c9052/lib64", "/sysroot/lib64", uintptr(0x4005), false}, nil, nil),
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/var/lib/planterette/base/debian:f92c9052/lost+found"), MustAbs("/var/lib/planterette/base/debian:f92c9052/lost+found"), MustAbs("/lost+found"), 0}}}, nil, nil}, {"stat", expectArgs{"/host/var/lib/planterette/base/debian:f92c9052/lost+found"}, isDirFi(true), nil}, {"mkdirAll", expectArgs{"/sysroot/lost+found", os.FileMode(0700)}, nil, nil}, {"bindMount", expectArgs{"/host/var/lib/planterette/base/debian:f92c9052/lost+found", "/sysroot/lost+found", uintptr(0x4005), false}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/var/lib/planterette/base/debian:f92c9052/lost+found"}, isDirFi(true), nil), call("mkdirAll", stub.ExpectArgs{"/sysroot/lost+found", os.FileMode(0700)}, nil, nil), call("verbosef", stub.ExpectArgs{"mounting %q on %q flags %#x", []any{"/host/var/lib/planterette/base/debian:f92c9052/lost+found", "/sysroot/lost+found", uintptr(0x4005)}}, nil, nil), call("bindMount", stub.ExpectArgs{"/host/var/lib/planterette/base/debian:f92c9052/lost+found", "/sysroot/lost+found", uintptr(0x4005), false}, nil, nil),
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/var/lib/planterette/base/debian:f92c9052/nix"), MustAbs("/var/lib/planterette/base/debian:f92c9052/nix"), MustAbs("/nix"), 0}}}, nil, nil}, {"stat", expectArgs{"/host/var/lib/planterette/base/debian:f92c9052/nix"}, isDirFi(true), nil}, {"mkdirAll", expectArgs{"/sysroot/nix", os.FileMode(0700)}, nil, nil}, {"bindMount", expectArgs{"/host/var/lib/planterette/base/debian:f92c9052/nix", "/sysroot/nix", uintptr(0x4005), false}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/var/lib/planterette/base/debian:f92c9052/nix"}, isDirFi(true), nil), call("mkdirAll", stub.ExpectArgs{"/sysroot/nix", os.FileMode(0700)}, nil, nil), call("verbosef", stub.ExpectArgs{"mounting %q on %q flags %#x", []any{"/host/var/lib/planterette/base/debian:f92c9052/nix", "/sysroot/nix", uintptr(0x4005)}}, nil, nil), call("bindMount", stub.ExpectArgs{"/host/var/lib/planterette/base/debian:f92c9052/nix", "/sysroot/nix", uintptr(0x4005), false}, nil, nil),
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/var/lib/planterette/base/debian:f92c9052/root"), MustAbs("/var/lib/planterette/base/debian:f92c9052/root"), MustAbs("/root"), 0}}}, nil, nil}, {"stat", expectArgs{"/host/var/lib/planterette/base/debian:f92c9052/root"}, isDirFi(true), nil}, {"mkdirAll", expectArgs{"/sysroot/root", os.FileMode(0700)}, nil, nil}, {"bindMount", expectArgs{"/host/var/lib/planterette/base/debian:f92c9052/root", "/sysroot/root", uintptr(0x4005), false}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/var/lib/planterette/base/debian:f92c9052/root"}, isDirFi(true), nil), call("mkdirAll", stub.ExpectArgs{"/sysroot/root", os.FileMode(0700)}, nil, nil), call("verbosef", stub.ExpectArgs{"mounting %q on %q flags %#x", []any{"/host/var/lib/planterette/base/debian:f92c9052/root", "/sysroot/root", uintptr(0x4005)}}, nil, nil), call("bindMount", stub.ExpectArgs{"/host/var/lib/planterette/base/debian:f92c9052/root", "/sysroot/root", uintptr(0x4005), false}, nil, nil),
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/var/lib/planterette/base/debian:f92c9052/run"), MustAbs("/var/lib/planterette/base/debian:f92c9052/run"), MustAbs("/run"), 0}}}, nil, nil}, {"stat", expectArgs{"/host/var/lib/planterette/base/debian:f92c9052/run"}, isDirFi(true), nil}, {"mkdirAll", expectArgs{"/sysroot/run", os.FileMode(0700)}, nil, nil}, {"bindMount", expectArgs{"/host/var/lib/planterette/base/debian:f92c9052/run", "/sysroot/run", uintptr(0x4005), false}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/var/lib/planterette/base/debian:f92c9052/run"}, isDirFi(true), nil), call("mkdirAll", stub.ExpectArgs{"/sysroot/run", os.FileMode(0700)}, nil, nil), call("verbosef", stub.ExpectArgs{"mounting %q on %q flags %#x", []any{"/host/var/lib/planterette/base/debian:f92c9052/run", "/sysroot/run", uintptr(0x4005)}}, nil, nil), call("bindMount", stub.ExpectArgs{"/host/var/lib/planterette/base/debian:f92c9052/run", "/sysroot/run", uintptr(0x4005), false}, nil, nil),
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/var/lib/planterette/base/debian:f92c9052/srv"), MustAbs("/var/lib/planterette/base/debian:f92c9052/srv"), MustAbs("/srv"), 0}}}, nil, nil}, {"stat", expectArgs{"/host/var/lib/planterette/base/debian:f92c9052/srv"}, isDirFi(true), nil}, {"mkdirAll", expectArgs{"/sysroot/srv", os.FileMode(0700)}, nil, nil}, {"bindMount", expectArgs{"/host/var/lib/planterette/base/debian:f92c9052/srv", "/sysroot/srv", uintptr(0x4005), false}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/var/lib/planterette/base/debian:f92c9052/srv"}, isDirFi(true), nil), call("mkdirAll", stub.ExpectArgs{"/sysroot/srv", os.FileMode(0700)}, nil, nil), call("verbosef", stub.ExpectArgs{"mounting %q on %q flags %#x", []any{"/host/var/lib/planterette/base/debian:f92c9052/srv", "/sysroot/srv", uintptr(0x4005)}}, nil, nil), call("bindMount", stub.ExpectArgs{"/host/var/lib/planterette/base/debian:f92c9052/srv", "/sysroot/srv", uintptr(0x4005), false}, nil, nil),
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/var/lib/planterette/base/debian:f92c9052/sys"), MustAbs("/var/lib/planterette/base/debian:f92c9052/sys"), MustAbs("/sys"), 0}}}, nil, nil}, {"stat", expectArgs{"/host/var/lib/planterette/base/debian:f92c9052/sys"}, isDirFi(true), nil}, {"mkdirAll", expectArgs{"/sysroot/sys", os.FileMode(0700)}, nil, nil}, {"bindMount", expectArgs{"/host/var/lib/planterette/base/debian:f92c9052/sys", "/sysroot/sys", uintptr(0x4005), false}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/var/lib/planterette/base/debian:f92c9052/sys"}, isDirFi(true), nil), call("mkdirAll", stub.ExpectArgs{"/sysroot/sys", os.FileMode(0700)}, nil, nil), call("verbosef", stub.ExpectArgs{"mounting %q on %q flags %#x", []any{"/host/var/lib/planterette/base/debian:f92c9052/sys", "/sysroot/sys", uintptr(0x4005)}}, nil, nil), call("bindMount", stub.ExpectArgs{"/host/var/lib/planterette/base/debian:f92c9052/sys", "/sysroot/sys", uintptr(0x4005), false}, nil, nil),
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/var/lib/planterette/base/debian:f92c9052/usr"), MustAbs("/var/lib/planterette/base/debian:f92c9052/usr"), MustAbs("/usr"), 0}}}, nil, nil}, {"stat", expectArgs{"/host/var/lib/planterette/base/debian:f92c9052/usr"}, isDirFi(true), nil}, {"mkdirAll", expectArgs{"/sysroot/usr", os.FileMode(0700)}, nil, nil}, {"bindMount", expectArgs{"/host/var/lib/planterette/base/debian:f92c9052/usr", "/sysroot/usr", uintptr(0x4005), false}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/var/lib/planterette/base/debian:f92c9052/usr"}, isDirFi(true), nil), call("mkdirAll", stub.ExpectArgs{"/sysroot/usr", os.FileMode(0700)}, nil, nil), call("verbosef", stub.ExpectArgs{"mounting %q on %q flags %#x", []any{"/host/var/lib/planterette/base/debian:f92c9052/usr", "/sysroot/usr", uintptr(0x4005)}}, nil, nil), call("bindMount", stub.ExpectArgs{"/host/var/lib/planterette/base/debian:f92c9052/usr", "/sysroot/usr", uintptr(0x4005), false}, nil, nil),
-			{"verbosef", expectArgs{"%s %s", []any{"mounting", &BindMountOp{MustAbs("/var/lib/planterette/base/debian:f92c9052/var"), MustAbs("/var/lib/planterette/base/debian:f92c9052/var"), MustAbs("/var"), 0}}}, nil, nil}, {"stat", expectArgs{"/host/var/lib/planterette/base/debian:f92c9052/var"}, isDirFi(true), nil}, {"mkdirAll", expectArgs{"/sysroot/var", os.FileMode(0700)}, nil, nil}, {"bindMount", expectArgs{"/host/var/lib/planterette/base/debian:f92c9052/var", "/sysroot/var", uintptr(0x4005), false}, nil, nil},
+			call("stat", stub.ExpectArgs{"/host/var/lib/planterette/base/debian:f92c9052/var"}, isDirFi(true), nil), call("mkdirAll", stub.ExpectArgs{"/sysroot/var", os.FileMode(0700)}, nil, nil), call("verbosef", stub.ExpectArgs{"mounting %q on %q flags %#x", []any{"/host/var/lib/planterette/base/debian:f92c9052/var", "/sysroot/var", uintptr(0x4005)}}, nil, nil), call("bindMount", stub.ExpectArgs{"/host/var/lib/planterette/base/debian:f92c9052/var", "/sysroot/var", uintptr(0x4005), false}, nil, nil),
 		}, nil},
 	})
 
@@ -140,7 +140,7 @@ func TestAutoRootOp(t *testing.T) {
 		}, &AutoRootOp{
 			Host:     MustAbs("/"),
 			Flags:    BindWritable,
-			resolved: []Op{new(BindMountOp)},
+			resolved: []*BindMountOp{new(BindMountOp)},
 		}, true},
 
 		{"flags differs", &AutoRootOp{

container/container.go

@@ -64,7 +64,7 @@ type (
 		Args []string
 		// Deliver SIGINT to the initial process on context cancellation.
 		ForwardCancel bool
-		// time to wait for linger processes after death of initial process
+		// Time to wait for processes lingering after the initial process terminates.
 		AdoptWaitDelay time.Duration
 
 		// Mapped Uid in user namespace.
@@ -99,17 +99,66 @@ type (
 	}
 )
 
-// Start starts the container init. The init process blocks until Serve is called.
+// A StartError contains additional information on a container startup failure.
-func (p *Container) Start() error {
+type StartError struct {
-	if p.cmd != nil {
+	// Fatal suggests whether this error should be considered fatal for the entire program.
-		return errors.New("container: already started")
+	Fatal bool
+	// Step refers to the part of the setup this error is returned from.
+	Step string
+	// Err is the underlying error.
+	Err error
+	// Origin is whether this error originated from the [Container.Start] method.
+	Origin bool
+	// Passthrough is whether the Error method is passed through to Err.
+	Passthrough bool
+}
+
+func (e *StartError) Unwrap() error { return e.Err }
+func (e *StartError) Error() string {
+	if e.Passthrough {
+		return e.Err.Error()
 	}
-	if p.Ops == nil || len(*p.Ops) == 0 {
+	if e.Origin {
-		return errors.New("container: starting an empty container")
+		return e.Step
 	}
 
-	ctx, cancel := context.WithCancel(p.ctx)
+	{
-	p.cancel = cancel
+		var syscallError *os.SyscallError
+		if errors.As(e.Err, &syscallError) && syscallError != nil {
+			return e.Step + " " + syscallError.Error()
+		}
+	}
+
+	return e.Step + ": " + e.Err.Error()
+}
+
+// Message returns a user-facing error message.
+func (e *StartError) Message() string {
+	if e.Passthrough {
+		switch {
+		case errors.As(e.Err, new(*os.PathError)),
+			errors.As(e.Err, new(*os.SyscallError)):
+			return "cannot " + e.Err.Error()
+
+		default:
+			return e.Err.Error()
+		}
+	}
+	if e.Origin {
+		return e.Step
+	}
+	return "cannot " + e.Error()
+}
+
+// Start starts the container init. The init process blocks until Serve is called.
+func (p *Container) Start() error {
+	if p == nil || p.cmd == nil ||
+		p.Ops == nil || len(*p.Ops) == 0 {
+		return errors.New("container: starting an invalid container")
+	}
+	if p.cmd.Process != nil {
+		return errors.New("container: already started")
+	}
 
 	// map to overflow id to work around ownership checks
 	if p.Uid < 1 {
@@ -131,9 +180,17 @@ func (p *Container) Start() error {
 		p.AdoptWaitDelay = 0
 	}
 
-	p.cmd = exec.CommandContext(ctx, MustExecutable())
+	if p.cmd.Stdin == nil {
+		p.cmd.Stdin = p.Stdin
+	}
+	if p.cmd.Stdout == nil {
+		p.cmd.Stdout = p.Stdout
+	}
+	if p.cmd.Stderr == nil {
+		p.cmd.Stderr = p.Stderr
+	}
+
 	p.cmd.Args = []string{initName}
-	p.cmd.Stdin, p.cmd.Stdout, p.cmd.Stderr = p.Stdin, p.Stdout, p.Stderr
 	p.cmd.WaitDelay = p.WaitDelay
 	if p.Cancel != nil {
 		p.cmd.Cancel = func() error { return p.Cancel(p.cmd) }
@@ -167,8 +224,7 @@ func (p *Container) Start() error {
 
 	// place setup pipe before user supplied extra files, this is later restored by init
 	if fd, e, err := Setup(&p.cmd.ExtraFiles); err != nil {
-		return wrapErrSuffix(err,
+		return &StartError{true, "set up params stream", err, false, false}
-			"cannot create shim setup pipe:")
 	} else {
 		p.setup = e
 		p.cmd.Env = []string{setupEnv + "=" + strconv.Itoa(fd)}
@@ -183,8 +239,7 @@ func (p *Container) Start() error {
 		done <- func() error { // setup depending on per-thread state must happen here
 			// PR_SET_NO_NEW_PRIVS: depends on per-thread state but acts on all processes created from that thread
 			if err := SetNoNewPrivs(); err != nil {
-				return wrapErrSuffix(err,
+				return &StartError{true, "prctl(PR_SET_NO_NEW_PRIVS)", err, false, false}
-					"prctl(PR_SET_NO_NEW_PRIVS):")
 			}
 
 			// landlock: depends on per-thread state but acts on a process group
@@ -200,28 +255,24 @@ func (p *Container) Start() error {
 						// already covered by namespaces (pid)
 						goto landlockOut
 					}
-					return wrapErrSuffix(err,
+					return &StartError{false, "get landlock ABI", err, false, false}
-						"landlock does not appear to be enabled:")
 				} else if abi < 6 {
 					if p.HostAbstract {
 						// see above comment
 						goto landlockOut
 					}
-					return msg.WrapErr(ENOSYS,
+					return &StartError{false, "kernel version too old for LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET", ENOSYS, true, false}
-						"kernel version too old for LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET")
 				} else {
 					msg.Verbosef("landlock abi version %d", abi)
 				}
 
 				if rulesetFd, err := rulesetAttr.Create(0); err != nil {
-					return wrapErrSuffix(err,
+					return &StartError{true, "create landlock ruleset", err, false, false}
-						"cannot create landlock ruleset:")
 				} else {
 					msg.Verbosef("enforcing landlock ruleset %s", rulesetAttr)
 					if err = LandlockRestrictSelf(rulesetFd, 0); err != nil {
 						_ = Close(rulesetFd)
-						return wrapErrSuffix(err,
+						return &StartError{true, "enforce landlock ruleset", err, false, false}
-							"cannot enforce landlock ruleset:")
 					}
 					if err = Close(rulesetFd); err != nil {
 						msg.Verbosef("cannot close landlock ruleset: %v", err)
@@ -234,7 +285,7 @@ func (p *Container) Start() error {
 
 			msg.Verbose("starting container init")
 			if err := p.cmd.Start(); err != nil {
-				return msg.WrapErr(err, err.Error())
+				return &StartError{false, "start container init", err, false, true}
 			}
 			return nil
 		}()
@@ -257,7 +308,7 @@ func (p *Container) Serve() error {
 
 	if p.Path == nil {
 		p.cancel()
-		return msg.WrapErr(EINVAL, "invalid executable pathname")
+		return &StartError{false, "invalid executable pathname", EINVAL, true, false}
 	}
 
 	// do not transmit nil
@@ -285,7 +336,7 @@ func (p *Container) Serve() error {
 
 // Wait waits for the container init process to exit and releases any resources associated with the [Container].
 func (p *Container) Wait() error {
-	if p.cmd == nil {
+	if p.cmd == nil || p.cmd.Process == nil {
 		return EINVAL
 	}
 
@@ -297,6 +348,36 @@ func (p *Container) Wait() error {
 	return err
 }
 
+// StdinPipe calls the [exec.Cmd] method with the same name.
+func (p *Container) StdinPipe() (w io.WriteCloser, err error) {
+	if p.Stdin != nil {
+		return nil, errors.New("container: Stdin already set")
+	}
+	w, err = p.cmd.StdinPipe()
+	p.Stdin = p.cmd.Stdin
+	return
+}
+
+// StdoutPipe calls the [exec.Cmd] method with the same name.
+func (p *Container) StdoutPipe() (r io.ReadCloser, err error) {
+	if p.Stdout != nil {
+		return nil, errors.New("container: Stdout already set")
+	}
+	r, err = p.cmd.StdoutPipe()
+	p.Stdout = p.cmd.Stdout
+	return
+}
+
+// StderrPipe calls the [exec.Cmd] method with the same name.
+func (p *Container) StderrPipe() (r io.ReadCloser, err error) {
+	if p.Stderr != nil {
+		return nil, errors.New("container: Stderr already set")
+	}
+	r, err = p.cmd.StderrPipe()
+	p.Stderr = p.cmd.Stderr
+	return
+}
+
 func (p *Container) String() string {
 	return fmt.Sprintf("argv: %q, filter: %v, rules: %d, flags: %#x, presets: %#x",
 		p.Args, !p.SeccompDisable, len(p.SeccompRules), int(p.SeccompFlags), int(p.SeccompPresets))
@@ -312,7 +393,11 @@ func (p *Container) ProcessState() *os.ProcessState {
 
 // New returns the address to a new instance of [Container] that requires further initialisation before use.
 func New(ctx context.Context) *Container {
-	return &Container{ctx: ctx, Params: Params{Ops: new(Ops)}}
+	p := &Container{ctx: ctx, Params: Params{Ops: new(Ops)}}
+	c, cancel := context.WithCancel(ctx)
+	p.cancel = cancel
+	p.cmd = exec.CommandContext(c, MustExecutable())
+	return p
 }
 
 // NewCommand calls [New] and initialises the [Params.Path] and [Params.Args] fields.

container/container_test.go

@@ -7,9 +7,11 @@ import (
 	"errors"
 	"fmt"
 	"log"
+	"net"
 	"os"
 	"os/exec"
 	"os/signal"
+	"reflect"
 	"strconv"
 	"strings"
 	"syscall"
@@ -26,6 +28,143 @@ import (
 	"hakurei.app/ldd"
 )
 
+func TestStartError(t *testing.T) {
+	testCases := []struct {
+		name string
+		err  error
+		s    string
+		is   error
+		isF  error
+		msg  string
+	}{
+		{"params env", &container.StartError{
+			Fatal: true,
+			Step:  "set up params stream",
+			Err:   container.ErrReceiveEnv,
+		},
+			"set up params stream: environment variable not set",
+			container.ErrReceiveEnv, syscall.EBADF,
+			"cannot set up params stream: environment variable not set"},
+
+		{"params", &container.StartError{
+			Fatal: true,
+			Step:  "set up params stream",
+			Err:   &os.SyscallError{Syscall: "pipe2", Err: syscall.EBADF},
+		},
+			"set up params stream pipe2: bad file descriptor",
+			syscall.EBADF, os.ErrInvalid,
+			"cannot set up params stream pipe2: bad file descriptor"},
+
+		{"PR_SET_NO_NEW_PRIVS", &container.StartError{
+			Fatal: true,
+			Step:  "prctl(PR_SET_NO_NEW_PRIVS)",
+			Err:   syscall.EPERM,
+		},
+			"prctl(PR_SET_NO_NEW_PRIVS): operation not permitted",
+			syscall.EPERM, syscall.EACCES,
+			"cannot prctl(PR_SET_NO_NEW_PRIVS): operation not permitted"},
+
+		{"landlock abi", &container.StartError{
+			Step: "get landlock ABI",
+			Err:  syscall.ENOSYS,
+		},
+			"get landlock ABI: function not implemented",
+			syscall.ENOSYS, syscall.ENOEXEC,
+			"cannot get landlock ABI: function not implemented"},
+
+		{"landlock old", &container.StartError{
+			Step:   "kernel version too old for LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET",
+			Err:    syscall.ENOSYS,
+			Origin: true,
+		},
+			"kernel version too old for LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET",
+			syscall.ENOSYS, syscall.ENOSPC,
+			"kernel version too old for LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET"},
+
+		{"landlock create", &container.StartError{
+			Fatal: true,
+			Step:  "create landlock ruleset",
+			Err:   syscall.EBADFD,
+		},
+			"create landlock ruleset: file descriptor in bad state",
+			syscall.EBADFD, syscall.EBADF,
+			"cannot create landlock ruleset: file descriptor in bad state"},
+
+		{"landlock enforce", &container.StartError{
+			Fatal: true,
+			Step:  "enforce landlock ruleset",
+			Err:   syscall.ENOTRECOVERABLE,
+		},
+			"enforce landlock ruleset: state not recoverable",
+			syscall.ENOTRECOVERABLE, syscall.ETIMEDOUT,
+			"cannot enforce landlock ruleset: state not recoverable"},
+
+		{"start", &container.StartError{
+			Step: "start container init",
+			Err: &os.PathError{
+				Op:   "fork/exec",
+				Path: "/proc/nonexistent",
+				Err:  syscall.ENOENT,
+			}, Passthrough: true,
+		},
+			"fork/exec /proc/nonexistent: no such file or directory",
+			syscall.ENOENT, syscall.ENOSYS,
+			"cannot fork/exec /proc/nonexistent: no such file or directory"},
+
+		{"start syscall", &container.StartError{
+			Step: "start container init",
+			Err: &os.SyscallError{
+				Syscall: "open",
+				Err:     syscall.ENOSYS,
+			}, Passthrough: true,
+		},
+			"open: function not implemented",
+			syscall.ENOSYS, syscall.ENOENT,
+			"cannot open: function not implemented"},
+
+		{"start other", &container.StartError{
+			Step: "start container init",
+			Err: &net.OpError{
+				Op:  "dial",
+				Net: "unix",
+				Err: syscall.ECONNREFUSED,
+			}, Passthrough: true,
+		},
+			"dial unix: connection refused",
+			syscall.ECONNREFUSED, syscall.ECONNABORTED,
+			"dial unix: connection refused"},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Run("error", func(t *testing.T) {
+				if got := tc.err.Error(); got != tc.s {
+					t.Errorf("Error: %q, want %q", got, tc.s)
+				}
+			})
+
+			t.Run("is", func(t *testing.T) {
+				if !errors.Is(tc.err, tc.is) {
+					t.Error("Is: unexpected false")
+				}
+				if errors.Is(tc.err, tc.isF) {
+					t.Errorf("Is: unexpected true")
+				}
+			})
+
+			t.Run("msg", func(t *testing.T) {
+				if got, ok := container.GetErrorMessage(tc.err); !ok {
+					if tc.msg != "" {
+						t.Errorf("GetErrorMessage: err does not implement MessageError")
+					}
+					return
+				} else if got != tc.msg {
+					t.Errorf("GetErrorMessage: %q, want %q", got, tc.msg)
+				}
+			})
+		})
+	}
+}
+
 const (
 	ignore  = "\x00"
 	ignoreV = -1
@@ -75,7 +214,7 @@ var containerTestCases = []struct {
 		1000, 100, nil, 0, seccomp.PresetExt},
 	{"custom rules", true, true, true, false,
 		emptyOps, emptyMnt,
-		1, 31, []seccomp.NativeRule{{seccomp.ScmpSyscall(syscall.SYS_SETUID), seccomp.ScmpErrno(syscall.EPERM), nil}}, 0, seccomp.PresetExt},
+		1, 31, []seccomp.NativeRule{{Syscall: seccomp.ScmpSyscall(syscall.SYS_SETUID), Errno: seccomp.ScmpErrno(syscall.EPERM)}}, 0, seccomp.PresetExt},
 
 	{"tmpfs", true, false, false, true,
 		earlyOps(new(container.Ops).
@@ -100,6 +239,7 @@ var containerTestCases = []struct {
 			ent("/tty", "/dev/tty", "rw,nosuid", "devtmpfs", "devtmpfs", ignore),
 			ent("/", "/dev/pts", "rw,nosuid,noexec,relatime", "devpts", "devpts", "rw,mode=620,ptmxmode=666"),
 			ent("/", "/dev/mqueue", "rw,nosuid,nodev,noexec,relatime", "mqueue", "mqueue", "rw"),
+			ent("/", "/dev/shm", "rw,nosuid,nodev,relatime", "tmpfs", "tmpfs", ignore),
 		),
 		1971, 100, nil, 0, seccomp.PresetStrict},
 
@@ -116,6 +256,7 @@ var containerTestCases = []struct {
 			ent("/urandom", "/dev/urandom", "rw,nosuid", "devtmpfs", "devtmpfs", ignore),
 			ent("/tty", "/dev/tty", "rw,nosuid", "devtmpfs", "devtmpfs", ignore),
 			ent("/", "/dev/pts", "rw,nosuid,noexec,relatime", "devpts", "devpts", "rw,mode=620,ptmxmode=666"),
+			ent("/", "/dev/shm", "rw,nosuid,nodev,relatime", "tmpfs", "tmpfs", ignore),
 		),
 		1971, 100, nil, 0, seccomp.PresetStrict},
 
@@ -215,9 +356,11 @@ func TestContainer(t *testing.T) {
 	t.Run("cancel", testContainerCancel(nil, func(t *testing.T, c *container.Container) {
 		wantErr := context.Canceled
 		wantExitCode := 0
-		if err := c.Wait(); !errors.Is(err, wantErr) {
+		if err := c.Wait(); !reflect.DeepEqual(err, wantErr) {
-			container.GetOutput().PrintBaseErr(err, "wait:")
+			if m, ok := container.InternalMessageFromError(err); ok {
-			t.Errorf("Wait: error = %v, want %v", err, wantErr)
+				t.Error(m)
+			}
+			t.Errorf("Wait: error = %#v, want %#v", err, wantErr)
 		}
 		if ps := c.ProcessState(); ps == nil {
 			t.Errorf("ProcessState unexpectedly returned nil")
@@ -231,7 +374,9 @@ func TestContainer(t *testing.T) {
 	}, func(t *testing.T, c *container.Container) {
 		var exitError *exec.ExitError
 		if err := c.Wait(); !errors.As(err, &exitError) {
-			container.GetOutput().PrintBaseErr(err, "wait:")
+			if m, ok := container.InternalMessageFromError(err); ok {
+				t.Error(m)
+			}
 			t.Errorf("Wait: error = %v", err)
 		}
 		if code := exitError.ExitCode(); code != blockExitCodeInterrupt {
@@ -311,17 +456,26 @@ func TestContainer(t *testing.T) {
 
 			if err := c.Start(); err != nil {
 				_, _ = output.WriteTo(os.Stdout)
-				container.GetOutput().PrintBaseErr(err, "start:")
+				if m, ok := container.InternalMessageFromError(err); ok {
-				t.Fatalf("cannot start container: %v", err)
+					t.Fatal(m)
+				} else {
+					t.Fatalf("cannot start container: %v", err)
+				}
 			} else if err = c.Serve(); err != nil {
 				_, _ = output.WriteTo(os.Stdout)
-				container.GetOutput().PrintBaseErr(err, "serve:")
+				if m, ok := container.InternalMessageFromError(err); ok {
-				t.Errorf("cannot serve setup params: %v", err)
+					t.Error(m)
+				} else {
+					t.Errorf("cannot serve setup params: %v", err)
+				}
 			}
 			if err := c.Wait(); err != nil {
 				_, _ = output.WriteTo(os.Stdout)
-				container.GetOutput().PrintBaseErr(err, "wait:")
+				if m, ok := container.InternalMessageFromError(err); ok {
-				t.Fatalf("wait: %v", err)
+					t.Fatal(m)
+				} else {
+					t.Fatalf("wait: %v", err)
+				}
 			}
 		})
 	}
@@ -374,11 +528,17 @@ func testContainerCancel(
 		}
 
 		if err := c.Start(); err != nil {
-			container.GetOutput().PrintBaseErr(err, "start:")
+			if m, ok := container.InternalMessageFromError(err); ok {
-			t.Fatalf("cannot start container: %v", err)
+				t.Fatal(m)
+			} else {
+				t.Fatalf("cannot start container: %v", err)
+			}
 		} else if err = c.Serve(); err != nil {
-			container.GetOutput().PrintBaseErr(err, "serve:")
+			if m, ok := container.InternalMessageFromError(err); ok {
-			t.Errorf("cannot serve setup params: %v", err)
+				t.Error(m)
+			} else {
+				t.Errorf("cannot serve setup params: %v", err)
+			}
 		}
 		<-ready
 		cancel()

container/dispatcher.go

@@ -53,7 +53,7 @@ type syscallDispatcher interface {
 	receive(key string, e any, fdp *uintptr) (closeFunc func() error, err error)
 
 	// bindMount provides procPaths.bindMount.
-	bindMount(source, target string, flags uintptr, eq bool) error
+	bindMount(source, target string, flags uintptr) error
 	// remount provides procPaths.remount.
 	remount(target string, flags uintptr) error
 	// mountTmpfs provides mountTmpfs.
@@ -138,8 +138,6 @@ type syscallDispatcher interface {
 	resume() bool
 	// beforeExit provides [Msg.BeforeExit].
 	beforeExit()
-	// printBaseErr provides [Msg.PrintBaseErr].
-	printBaseErr(err error, fallback string)
 }
 
 // direct implements syscallDispatcher on the current kernel.
@@ -163,8 +161,8 @@ func (direct) receive(key string, e any, fdp *uintptr) (func() error, error) {
 	return Receive(key, e, fdp)
 }
 
-func (direct) bindMount(source, target string, flags uintptr, eq bool) error {
+func (direct) bindMount(source, target string, flags uintptr) error {
-	return hostProc.bindMount(source, target, flags, eq)
+	return hostProc.bindMount(source, target, flags)
 }
 func (direct) remount(target string, flags uintptr) error {
 	return hostProc.remount(target, flags)
@@ -225,7 +223,7 @@ func (direct) pivotRoot(newroot, putold string) (err error) {
 	return syscall.PivotRoot(newroot, putold)
 }
 func (direct) mount(source, target, fstype string, flags uintptr, data string) (err error) {
-	return syscall.Mount(source, target, fstype, flags, data)
+	return mount(source, target, fstype, flags, data)
 }
 func (direct) unmount(target string, flags int) (err error) {
 	return syscall.Unmount(target, flags)
@@ -234,12 +232,11 @@ func (direct) wait4(pid int, wstatus *syscall.WaitStatus, options int, rusage *s
 	return syscall.Wait4(pid, wstatus, options, rusage)
 }
 
-func (direct) printf(format string, v ...any)          { log.Printf(format, v...) }
+func (direct) printf(format string, v ...any)   { log.Printf(format, v...) }
-func (direct) fatal(v ...any)                          { log.Fatal(v...) }
+func (direct) fatal(v ...any)                   { log.Fatal(v...) }
-func (direct) fatalf(format string, v ...any)          { log.Fatalf(format, v...) }
+func (direct) fatalf(format string, v ...any)   { log.Fatalf(format, v...) }
-func (direct) verbose(v ...any)                        { msg.Verbose(v...) }
+func (direct) verbose(v ...any)                 { msg.Verbose(v...) }
-func (direct) verbosef(format string, v ...any)        { msg.Verbosef(format, v...) }
+func (direct) verbosef(format string, v ...any) { msg.Verbosef(format, v...) }
-func (direct) suspend()                                { msg.Suspend() }
+func (direct) suspend()                         { msg.Suspend() }
-func (direct) resume() bool                            { return msg.Resume() }
+func (direct) resume() bool                     { return msg.Resume() }
-func (direct) beforeExit()                             { msg.BeforeExit() }
+func (direct) beforeExit()                      { msg.BeforeExit() }
-func (direct) printBaseErr(err error, fallback string) { msg.PrintBaseErr(err, fallback) }

container/dispatcher_test.go

@@ -2,7 +2,6 @@ package container
 
 import (
 	"bytes"
-	"errors"
 	"io"
 	"io/fs"
 	"os"
@@ -11,16 +10,14 @@ import (
 	"runtime"
 	"slices"
 	"strings"
-	"sync"
 	"syscall"
 	"testing"
 	"time"
 
 	"hakurei.app/container/seccomp"
+	"hakurei.app/container/stub"
 )
 
-var errUnique = errors.New("unique error injected by the test suite")
-
 type opValidTestCase struct {
 	name string
 	op   Op
@@ -28,9 +25,15 @@ type opValidTestCase struct {
 }
 
 func checkOpsValid(t *testing.T, testCases []opValidTestCase) {
+	t.Helper()
+
 	t.Run("valid", func(t *testing.T) {
+		t.Helper()
+
 		for _, tc := range testCases {
 			t.Run(tc.name, func(t *testing.T) {
+				t.Helper()
+
 				if got := tc.op.Valid(); got != tc.want {
 					t.Errorf("Valid: %v, want %v", got, tc.want)
 				}
@@ -46,9 +49,15 @@ type opsBuilderTestCase struct {
 }
 
 func checkOpsBuilder(t *testing.T, testCases []opsBuilderTestCase) {
+	t.Helper()
+
 	t.Run("build", func(t *testing.T) {
+		t.Helper()
+
 		for _, tc := range testCases {
 			t.Run(tc.name, func(t *testing.T) {
+				t.Helper()
+
 				if !slices.EqualFunc(*tc.ops, tc.want, func(op Op, v Op) bool { return op.Is(v) }) {
 					t.Errorf("Ops: %#v, want %#v", tc.ops, tc.want)
 				}
@@ -64,9 +73,15 @@ type opIsTestCase struct {
 }
 
 func checkOpIs(t *testing.T, testCases []opIsTestCase) {
+	t.Helper()
+
 	t.Run("is", func(t *testing.T) {
+		t.Helper()
+
 		for _, tc := range testCases {
 			t.Run(tc.name, func(t *testing.T) {
+				t.Helper()
+
 				if got := tc.op.Is(tc.v); got != tc.want {
 					t.Errorf("Is: %v, want %v", got, tc.want)
 				}
@@ -84,16 +99,26 @@ type opMetaTestCase struct {
 }
 
 func checkOpMeta(t *testing.T, testCases []opMetaTestCase) {
+	t.Helper()
+
 	t.Run("meta", func(t *testing.T) {
+		t.Helper()
+
 		for _, tc := range testCases {
 			t.Run(tc.name, func(t *testing.T) {
+				t.Helper()
+
 				t.Run("prefix", func(t *testing.T) {
-					if got := tc.op.prefix(); got != tc.wantPrefix {
+					t.Helper()
+
+					if got, _ := tc.op.prefix(); got != tc.wantPrefix {
 						t.Errorf("prefix: %q, want %q", got, tc.wantPrefix)
 					}
 				})
 
 				t.Run("string", func(t *testing.T) {
+					t.Helper()
+
 					if got := tc.op.String(); got != tc.wantString {
 						t.Errorf("String: %s, want %s", got, tc.wantString)
 					}
@@ -103,23 +128,36 @@ func checkOpMeta(t *testing.T, testCases []opMetaTestCase) {
 	})
 }
 
+// call initialises a [stub.Call].
+// This keeps composites analysis happy without making the test cases too bloated.
+func call(name string, args stub.ExpectArgs, ret any, err error) stub.Call {
+	return stub.Call{Name: name, Args: args, Ret: ret, Err: err}
+}
+
 type simpleTestCase struct {
 	name    string
 	f       func(k syscallDispatcher) error
-	want    [][]kexpect
+	want    stub.Expect
 	wantErr error
 }
 
 func checkSimple(t *testing.T, fname string, testCases []simpleTestCase) {
+	t.Helper()
+
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
-			defer handleExitStub()
+			t.Helper()
-			k := &kstub{t: t, want: tc.want, wg: new(sync.WaitGroup)}
+
-			if err := tc.f(k); !errors.Is(err, tc.wantErr) {
+			wait4signal := make(chan struct{})
+			k := &kstub{wait4signal, stub.New(t, func(s *stub.Stub[syscallDispatcher]) syscallDispatcher { return &kstub{wait4signal, s} }, tc.want)}
+			defer stub.HandleExit(t)
+			if err := tc.f(k); !reflect.DeepEqual(err, tc.wantErr) {
 				t.Errorf("%s: error = %v, want %v", fname, err, tc.wantErr)
 			}
-			k.handleIncomplete(func(k *kstub) {
+			k.VisitIncomplete(func(s *stub.Stub[syscallDispatcher]) {
-				t.Errorf("%s: %d calls, want %d (track %d)", fname, k.pos, len(k.want[k.track]), k.track)
+				t.Helper()
+
+				t.Errorf("%s: %d calls, want %d", fname, s.Pos(), s.Len())
 			})
 		})
 	}
@@ -130,36 +168,45 @@ type opBehaviourTestCase struct {
 	params *Params
 	op     Op
 
-	early        []kexpect
+	early        []stub.Call
 	wantErrEarly error
 
-	apply        []kexpect
+	apply        []stub.Call
 	wantErrApply error
 }
 
 func checkOpBehaviour(t *testing.T, testCases []opBehaviourTestCase) {
+	t.Helper()
+
 	t.Run("behaviour", func(t *testing.T) {
+		t.Helper()
+
 		for _, tc := range testCases {
 			t.Run(tc.name, func(t *testing.T) {
-				defer handleExitStub()
+				t.Helper()
+
 				state := &setupState{Params: tc.params}
-				k := &kstub{t: t, want: [][]kexpect{slices.Concat(tc.early, []kexpect{{name: "\x00"}}, tc.apply)}, wg: new(sync.WaitGroup)}
+				k := &kstub{nil, stub.New(t,
+					func(s *stub.Stub[syscallDispatcher]) syscallDispatcher { return &kstub{nil, s} },
+					stub.Expect{Calls: slices.Concat(tc.early, []stub.Call{{Name: stub.CallSeparator}}, tc.apply)},
+				)}
+				defer stub.HandleExit(t)
 				errEarly := tc.op.early(state, k)
-				k.expect("\x00")
+				k.Expects(stub.CallSeparator)
-				if !errors.Is(errEarly, tc.wantErrEarly) {
+				if !reflect.DeepEqual(errEarly, tc.wantErrEarly) {
 					t.Errorf("early: error = %v, want %v", errEarly, tc.wantErrEarly)
 				}
 				if errEarly != nil {
 					goto out
 				}
 
-				if err := tc.op.apply(state, k); !errors.Is(err, tc.wantErrApply) {
+				if err := tc.op.apply(state, k); !reflect.DeepEqual(err, tc.wantErrApply) {
 					t.Errorf("apply: error = %v, want %v", err, tc.wantErrApply)
 				}
 
 			out:
-				k.handleIncomplete(func(k *kstub) {
+				k.VisitIncomplete(func(s *stub.Stub[syscallDispatcher]) {
-					count := k.pos - 1 // separator
+					count := k.Pos() - 1 // separator
 					if count < len(tc.early) {
 						t.Errorf("early: %d calls, want %d", count, len(tc.early))
 					} else {
@@ -226,8 +273,6 @@ func (writeErrOsFile) Stat() (fs.FileInfo, error)  { panic("unreachable") }
 func (writeErrOsFile) Read([]byte) (int, error)    { panic("unreachable") }
 func (writeErrOsFile) Close() error                { panic("unreachable") }
 
-type expectArgs = [5]any
-
 type isDirFi bool
 
 func (isDirFi) Name() string       { panic("unreachable") }
@@ -252,184 +297,94 @@ func (nameDentry) IsDir() bool                { panic("unreachable") }
 func (nameDentry) Type() fs.FileMode          { panic("unreachable") }
 func (nameDentry) Info() (fs.FileInfo, error) { panic("unreachable") }
 
-type kexpect struct {
+const (
-	name string
+	// magicWait4Signal must be used in a single pair of signal and wait4 calls across two goroutines
-	args expectArgs
+	// originating from the same toplevel kstub.
-	ret  any
+	// To enable this behaviour this value must be the last element of the args field in the wait4 call
-	err  error
+	// and the ret value of the signal call.
-}
+	magicWait4Signal = 0xdef
-
+)
-func (k *kexpect) error(ok ...bool) error {
-	if !slices.Contains(ok, false) {
-		return k.err
-	}
-	return syscall.ENOTRECOVERABLE
-}
-
-func handleExitStub() {
-	r := recover()
-	if r == 0xdeadbeef {
-		return
-	}
-	if r != nil {
-		panic(r)
-	}
-}
 
 type kstub struct {
-	t *testing.T
+	wait4signal chan struct{}
-
+	*stub.Stub[syscallDispatcher]
-	want [][]kexpect
-	// pos is the current position in want[track].
-	pos int
-	// track is the current active want.
-	track int
-	// sub stores addresses of kstub created by new.
-	sub []*kstub
-	// wg waits for all descendants to complete.
-	wg *sync.WaitGroup
 }
 
-// handleIncomplete calls f on an incomplete k and all its descendants.
+func (k *kstub) new(f func(k syscallDispatcher)) { k.Helper(); k.New(f) }
-func (k *kstub) handleIncomplete(f func(k *kstub)) {
-	k.wg.Wait()
 
-	if k.want != nil && len(k.want[k.track]) != k.pos {
+func (k *kstub) lockOSThread() { k.Helper(); k.Expects("lockOSThread") }
-		f(k)
-	}
-	for _, sk := range k.sub {
-		sk.handleIncomplete(f)
-	}
-}
-
-// expect checks name and returns the current kexpect and advances pos.
-func (k *kstub) expect(name string) (expect *kexpect) {
-	if len(k.want[k.track]) == k.pos {
-		k.t.Fatal("expect: want too short")
-	}
-	expect = &k.want[k.track][k.pos]
-	if name != expect.name {
-		if expect.name == "\x00" {
-			k.t.Fatalf("expect: func = %s, separator overrun", name)
-		}
-		if name == "\x00" {
-			k.t.Fatalf("expect: separator, want %s", expect.name)
-		}
-		k.t.Fatalf("expect: func = %s, want %s", name, expect.name)
-	}
-	k.pos++
-	return
-}
-
-// checkArg checks an argument comparable with the == operator. Avoid using this with pointers.
-func checkArg[T comparable](k *kstub, arg string, got T, n int) bool {
-	if k.pos == 0 {
-		panic("invalid call to checkArg")
-	}
-	expect := k.want[k.track][k.pos-1]
-	want, ok := expect.args[n].(T)
-	if !ok || got != want {
-		k.t.Errorf("%s: %s = %#v, want %#v (%d)", expect.name, arg, got, want, k.pos-1)
-		return false
-	}
-	return true
-}
-
-// checkArgReflect checks an argument of any type.
-func checkArgReflect(k *kstub, arg string, got any, n int) bool {
-	if k.pos == 0 {
-		panic("invalid call to checkArgReflect")
-	}
-	expect := k.want[k.track][k.pos-1]
-	want := expect.args[n]
-	if !reflect.DeepEqual(got, want) {
-		k.t.Errorf("%s: %s = %#v, want %#v (%d)", expect.name, arg, got, want, k.pos-1)
-		return false
-	}
-	return true
-}
-
-func (k *kstub) new(f func(k syscallDispatcher)) {
-	k.expect("new")
-	if len(k.want) <= k.track+1 {
-		k.t.Fatalf("new: track overrun")
-	}
-	sk := &kstub{t: k.t, want: k.want, track: len(k.sub) + 1, wg: k.wg}
-	k.sub = append(k.sub, sk)
-	k.wg.Add(1)
-	go func() {
-		defer k.wg.Done()
-		defer handleExitStub()
-		f(sk)
-	}()
-}
-
-func (k *kstub) lockOSThread() { k.expect("lockOSThread") }
 
 func (k *kstub) setPtracer(pid uintptr) error {
-	return k.expect("setPtracer").error(
+	k.Helper()
-		checkArg(k, "pid", pid, 0))
+	return k.Expects("setPtracer").Error(
+		stub.CheckArg(k.Stub, "pid", pid, 0))
 }
 
 func (k *kstub) setDumpable(dumpable uintptr) error {
-	return k.expect("setDumpable").error(
+	k.Helper()
-		checkArg(k, "dumpable", dumpable, 0))
+	return k.Expects("setDumpable").Error(
+		stub.CheckArg(k.Stub, "dumpable", dumpable, 0))
 }
 
-func (k *kstub) setNoNewPrivs() error { return k.expect("setNoNewPrivs").err }
+func (k *kstub) setNoNewPrivs() error { k.Helper(); return k.Expects("setNoNewPrivs").Err }
-func (k *kstub) lastcap() uintptr     { return k.expect("lastcap").ret.(uintptr) }
+func (k *kstub) lastcap() uintptr     { k.Helper(); return k.Expects("lastcap").Ret.(uintptr) }
 
 func (k *kstub) capset(hdrp *capHeader, datap *[2]capData) error {
-	return k.expect("capset").error(
+	k.Helper()
-		checkArgReflect(k, "hdrp", hdrp, 0),
+	return k.Expects("capset").Error(
-		checkArgReflect(k, "datap", datap, 1))
+		stub.CheckArgReflect(k.Stub, "hdrp", hdrp, 0),
+		stub.CheckArgReflect(k.Stub, "datap", datap, 1))
 }
 
 func (k *kstub) capBoundingSetDrop(cap uintptr) error {
-	return k.expect("capBoundingSetDrop").error(
+	k.Helper()
-		checkArg(k, "cap", cap, 0))
+	return k.Expects("capBoundingSetDrop").Error(
+		stub.CheckArg(k.Stub, "cap", cap, 0))
 }
 
-func (k *kstub) capAmbientClearAll() error { return k.expect("capAmbientClearAll").err }
+func (k *kstub) capAmbientClearAll() error { k.Helper(); return k.Expects("capAmbientClearAll").Err }
 
 func (k *kstub) capAmbientRaise(cap uintptr) error {
-	return k.expect("capAmbientRaise").error(
+	k.Helper()
-		checkArg(k, "cap", cap, 0))
+	return k.Expects("capAmbientRaise").Error(
+		stub.CheckArg(k.Stub, "cap", cap, 0))
 }
 
 func (k *kstub) isatty(fd int) bool {
-	expect := k.expect("isatty")
+	k.Helper()
-	if !checkArg(k, "fd", fd, 0) {
+	expect := k.Expects("isatty")
-		k.t.FailNow()
+	if !stub.CheckArg(k.Stub, "fd", fd, 0) {
+		k.FailNow()
 	}
-	return expect.ret.(bool)
+	return expect.Ret.(bool)
 }
 
 func (k *kstub) receive(key string, e any, fdp *uintptr) (closeFunc func() error, err error) {
-	expect := k.expect("receive")
+	k.Helper()
+	expect := k.Expects("receive")
 
 	var closed bool
 	closeFunc = func() error {
 		if closed {
-			k.t.Error("closeFunc called more than once")
+			k.Error("closeFunc called more than once")
 			return os.ErrClosed
 		}
 		closed = true
 
-		if expect.ret != nil {
+		if expect.Ret != nil {
 			// use return stored in kexpect for closeFunc instead
-			return expect.ret.(error)
+			return expect.Ret.(error)
 		}
 		return nil
 	}
-	err = expect.error(
+	err = expect.Error(
-		checkArg(k, "key", key, 0),
+		stub.CheckArg(k.Stub, "key", key, 0),
-		checkArgReflect(k, "e", e, 1),
+		stub.CheckArgReflect(k.Stub, "e", e, 1),
-		checkArgReflect(k, "fdp", fdp, 2))
+		stub.CheckArgReflect(k.Stub, "fdp", fdp, 2))
 
 	// 3 is unused so stores params
-	if expect.args[3] != nil {
+	if expect.Args[3] != nil {
-		if v, ok := expect.args[3].(*initParams); ok && v != nil {
+		if v, ok := expect.Args[3].(*initParams); ok && v != nil {
 			if p, ok0 := e.(*initParams); ok0 && p != nil {
 				*p = *v
 			}
@@ -437,8 +392,8 @@ func (k *kstub) receive(key string, e any, fdp *uintptr) (closeFunc func() error
 	}
 
 	// 4 is unused so stores fd
-	if expect.args[4] != nil {
+	if expect.Args[4] != nil {
-		if v, ok := expect.args[4].(uintptr); ok && v >= 3 {
+		if v, ok := expect.Args[4].(uintptr); ok && v >= 3 {
 			if fdp != nil {
 				*fdp = v
 			}
@@ -448,247 +403,291 @@ func (k *kstub) receive(key string, e any, fdp *uintptr) (closeFunc func() error
 	return
 }
 
-func (k *kstub) bindMount(source, target string, flags uintptr, eq bool) error {
+func (k *kstub) bindMount(source, target string, flags uintptr) error {
-	return k.expect("bindMount").error(
+	k.Helper()
-		checkArg(k, "source", source, 0),
+	return k.Expects("bindMount").Error(
-		checkArg(k, "target", target, 1),
+		stub.CheckArg(k.Stub, "source", source, 0),
-		checkArg(k, "flags", flags, 2),
+		stub.CheckArg(k.Stub, "target", target, 1),
-		checkArg(k, "eq", eq, 3))
+		stub.CheckArg(k.Stub, "flags", flags, 2))
 }
 
 func (k *kstub) remount(target string, flags uintptr) error {
-	return k.expect("remount").error(
+	k.Helper()
-		checkArg(k, "target", target, 0),
+	return k.Expects("remount").Error(
-		checkArg(k, "flags", flags, 1))
+		stub.CheckArg(k.Stub, "target", target, 0),
+		stub.CheckArg(k.Stub, "flags", flags, 1))
 }
 
 func (k *kstub) mountTmpfs(fsname, target string, flags uintptr, size int, perm os.FileMode) error {
-	return k.expect("mountTmpfs").error(
+	k.Helper()
-		checkArg(k, "fsname", fsname, 0),
+	return k.Expects("mountTmpfs").Error(
-		checkArg(k, "target", target, 1),
+		stub.CheckArg(k.Stub, "fsname", fsname, 0),
-		checkArg(k, "flags", flags, 2),
+		stub.CheckArg(k.Stub, "target", target, 1),
-		checkArg(k, "size", size, 3),
+		stub.CheckArg(k.Stub, "flags", flags, 2),
-		checkArg(k, "perm", perm, 4))
+		stub.CheckArg(k.Stub, "size", size, 3),
+		stub.CheckArg(k.Stub, "perm", perm, 4))
 }
 
 func (k *kstub) ensureFile(name string, perm, pperm os.FileMode) error {
-
+	k.Helper()
-	return k.expect("ensureFile").error(
+	return k.Expects("ensureFile").Error(
-		checkArg(k, "name", name, 0),
+		stub.CheckArg(k.Stub, "name", name, 0),
-		checkArg(k, "perm", perm, 1),
+		stub.CheckArg(k.Stub, "perm", perm, 1),
-		checkArg(k, "pperm", pperm, 2))
+		stub.CheckArg(k.Stub, "pperm", pperm, 2))
 }
 
 func (k *kstub) seccompLoad(rules []seccomp.NativeRule, flags seccomp.ExportFlag) error {
-	return k.expect("seccompLoad").error(
+	k.Helper()
-		checkArgReflect(k, "rules", rules, 0),
+	return k.Expects("seccompLoad").Error(
-		checkArg(k, "flags", flags, 1))
+		stub.CheckArgReflect(k.Stub, "rules", rules, 0),
+		stub.CheckArg(k.Stub, "flags", flags, 1))
 }
 
 func (k *kstub) notify(c chan<- os.Signal, sig ...os.Signal) {
-	expect := k.expect("notify")
+	k.Helper()
-	if c == nil || expect.error(
+	expect := k.Expects("notify")
-		checkArgReflect(k, "sig", sig, 1)) != nil {
+	if c == nil || expect.Error(
-		k.t.FailNow()
+		stub.CheckArgReflect(k.Stub, "sig", sig, 1)) != nil {
+		k.FailNow()
 	}
 
 	// export channel for external instrumentation
-	if chanf, ok := expect.args[0].(func(c chan<- os.Signal)); ok && chanf != nil {
+	if chanf, ok := expect.Args[0].(func(c chan<- os.Signal)); ok && chanf != nil {
 		chanf(c)
 	}
 }
 
 func (k *kstub) start(c *exec.Cmd) error {
-	expect := k.expect("start")
+	k.Helper()
-	err := expect.error(
+	expect := k.Expects("start")
-		checkArg(k, "c.Path", c.Path, 0),
+	err := expect.Error(
-		checkArgReflect(k, "c.Args", c.Args, 1),
+		stub.CheckArg(k.Stub, "c.Path", c.Path, 0),
-		checkArgReflect(k, "c.Env", c.Env, 2),
+		stub.CheckArgReflect(k.Stub, "c.Args", c.Args, 1),
-		checkArg(k, "c.Dir", c.Dir, 3))
+		stub.CheckArgReflect(k.Stub, "c.Env", c.Env, 2),
+		stub.CheckArg(k.Stub, "c.Dir", c.Dir, 3))
 
-	if process, ok := expect.ret.(*os.Process); ok && process != nil {
+	if process, ok := expect.Ret.(*os.Process); ok && process != nil {
 		c.Process = process
 	}
 	return err
 }
 
 func (k *kstub) signal(c *exec.Cmd, sig os.Signal) error {
-	return k.expect("signal").error(
+	k.Helper()
-		checkArg(k, "c.Path", c.Path, 0),
+	expect := k.Expects("signal")
-		checkArgReflect(k, "c.Args", c.Args, 1),
+	if v, ok := expect.Ret.(int); ok && v == magicWait4Signal {
-		checkArgReflect(k, "c.Env", c.Env, 2),
+		if k.wait4signal == nil {
-		checkArg(k, "c.Dir", c.Dir, 3),
+			panic("kstub not initialised for wait4 simulation")
-		checkArg(k, "sig", sig, 4))
+		}
+		defer func() { close(k.wait4signal) }()
+	}
+	return expect.Error(
+		stub.CheckArg(k.Stub, "c.Path", c.Path, 0),
+		stub.CheckArgReflect(k.Stub, "c.Args", c.Args, 1),
+		stub.CheckArgReflect(k.Stub, "c.Env", c.Env, 2),
+		stub.CheckArg(k.Stub, "c.Dir", c.Dir, 3),
+		stub.CheckArg(k.Stub, "sig", sig, 4))
 }
 
 func (k *kstub) evalSymlinks(path string) (string, error) {
-	expect := k.expect("evalSymlinks")
+	k.Helper()
-	return expect.ret.(string), expect.error(
+	expect := k.Expects("evalSymlinks")
-		checkArg(k, "path", path, 0))
+	return expect.Ret.(string), expect.Error(
+		stub.CheckArg(k.Stub, "path", path, 0))
 }
 
 func (k *kstub) exit(code int) {
-	k.expect("exit")
+	k.Helper()
-	if !checkArg(k, "code", code, 0) {
+	k.Expects("exit")
-		k.t.FailNow()
+	if !stub.CheckArg(k.Stub, "code", code, 0) {
+		k.FailNow()
 	}
-	panic(0xdeadbeef)
+	panic(stub.PanicExit)
 }
 
-func (k *kstub) getpid() int { return k.expect("getpid").ret.(int) }
+func (k *kstub) getpid() int { k.Helper(); return k.Expects("getpid").Ret.(int) }
 
 func (k *kstub) stat(name string) (os.FileInfo, error) {
-	expect := k.expect("stat")
+	k.Helper()
-	return expect.ret.(os.FileInfo), expect.error(
+	expect := k.Expects("stat")
-		checkArg(k, "name", name, 0))
+	return expect.Ret.(os.FileInfo), expect.Error(
+		stub.CheckArg(k.Stub, "name", name, 0))
 }
 
 func (k *kstub) mkdir(name string, perm os.FileMode) error {
-	return k.expect("mkdir").error(
+	k.Helper()
-		checkArg(k, "name", name, 0),
+	return k.Expects("mkdir").Error(
-		checkArg(k, "perm", perm, 1))
+		stub.CheckArg(k.Stub, "name", name, 0),
+		stub.CheckArg(k.Stub, "perm", perm, 1))
 }
 
 func (k *kstub) mkdirTemp(dir, pattern string) (string, error) {
-	expect := k.expect("mkdirTemp")
+	k.Helper()
-	return expect.ret.(string), expect.error(
+	expect := k.Expects("mkdirTemp")
-		checkArg(k, "dir", dir, 0),
+	return expect.Ret.(string), expect.Error(
-		checkArg(k, "pattern", pattern, 1))
+		stub.CheckArg(k.Stub, "dir", dir, 0),
+		stub.CheckArg(k.Stub, "pattern", pattern, 1))
 }
 
 func (k *kstub) mkdirAll(path string, perm os.FileMode) error {
-	return k.expect("mkdirAll").error(
+	k.Helper()
-		checkArg(k, "path", path, 0),
+	return k.Expects("mkdirAll").Error(
-		checkArg(k, "perm", perm, 1))
+		stub.CheckArg(k.Stub, "path", path, 0),
+		stub.CheckArg(k.Stub, "perm", perm, 1))
 }
 
 func (k *kstub) readdir(name string) ([]os.DirEntry, error) {
-	expect := k.expect("readdir")
+	k.Helper()
-	return expect.ret.([]os.DirEntry), expect.error(
+	expect := k.Expects("readdir")
-		checkArg(k, "name", name, 0))
+	return expect.Ret.([]os.DirEntry), expect.Error(
+		stub.CheckArg(k.Stub, "name", name, 0))
 }
 
 func (k *kstub) openNew(name string) (osFile, error) {
-	expect := k.expect("openNew")
+	k.Helper()
-	return expect.ret.(osFile), expect.error(
+	expect := k.Expects("openNew")
-		checkArg(k, "name", name, 0))
+	return expect.Ret.(osFile), expect.Error(
+		stub.CheckArg(k.Stub, "name", name, 0))
 }
 
 func (k *kstub) writeFile(name string, data []byte, perm os.FileMode) error {
-	return k.expect("writeFile").error(
+	k.Helper()
-		checkArg(k, "name", name, 0),
+	return k.Expects("writeFile").Error(
-		checkArgReflect(k, "data", data, 1),
+		stub.CheckArg(k.Stub, "name", name, 0),
-		checkArg(k, "perm", perm, 2))
+		stub.CheckArgReflect(k.Stub, "data", data, 1),
+		stub.CheckArg(k.Stub, "perm", perm, 2))
 }
 
 func (k *kstub) createTemp(dir, pattern string) (osFile, error) {
-	expect := k.expect("createTemp")
+	k.Helper()
-	return expect.ret.(osFile), expect.error(
+	expect := k.Expects("createTemp")
-		checkArg(k, "dir", dir, 0),
+	return expect.Ret.(osFile), expect.Error(
-		checkArg(k, "pattern", pattern, 1))
+		stub.CheckArg(k.Stub, "dir", dir, 0),
+		stub.CheckArg(k.Stub, "pattern", pattern, 1))
 }
 
 func (k *kstub) remove(name string) error {
-	return k.expect("remove").error(
+	k.Helper()
-		checkArg(k, "name", name, 0))
+	return k.Expects("remove").Error(
+		stub.CheckArg(k.Stub, "name", name, 0))
 }
 
 func (k *kstub) newFile(fd uintptr, name string) *os.File {
-	expect := k.expect("newFile")
+	k.Helper()
-	if expect.error(
+	expect := k.Expects("newFile")
-		checkArg(k, "fd", fd, 0),
+	if expect.Error(
-		checkArg(k, "name", name, 1)) != nil {
+		stub.CheckArg(k.Stub, "fd", fd, 0),
-		k.t.FailNow()
+		stub.CheckArg(k.Stub, "name", name, 1)) != nil {
+		k.FailNow()
 	}
-	return expect.ret.(*os.File)
+	return expect.Ret.(*os.File)
 }
 
 func (k *kstub) symlink(oldname, newname string) error {
-	return k.expect("symlink").error(
+	k.Helper()
-		checkArg(k, "oldname", oldname, 0),
+	return k.Expects("symlink").Error(
-		checkArg(k, "newname", newname, 1))
+		stub.CheckArg(k.Stub, "oldname", oldname, 0),
+		stub.CheckArg(k.Stub, "newname", newname, 1))
 }
 
 func (k *kstub) readlink(name string) (string, error) {
-	expect := k.expect("readlink")
+	k.Helper()
-	return expect.ret.(string), expect.error(
+	expect := k.Expects("readlink")
-		checkArg(k, "name", name, 0))
+	return expect.Ret.(string), expect.Error(
+		stub.CheckArg(k.Stub, "name", name, 0))
 }
 
 func (k *kstub) umask(mask int) (oldmask int) {
-	expect := k.expect("umask")
+	k.Helper()
-	if !checkArg(k, "mask", mask, 0) {
+	expect := k.Expects("umask")
-		k.t.FailNow()
+	if !stub.CheckArg(k.Stub, "mask", mask, 0) {
+		k.FailNow()
 	}
-	return expect.ret.(int)
+	return expect.Ret.(int)
 }
 
 func (k *kstub) sethostname(p []byte) (err error) {
-	return k.expect("sethostname").error(
+	k.Helper()
-		checkArgReflect(k, "p", p, 0))
+	return k.Expects("sethostname").Error(
+		stub.CheckArgReflect(k.Stub, "p", p, 0))
 }
 
 func (k *kstub) chdir(path string) (err error) {
-	return k.expect("chdir").error(
+	k.Helper()
-		checkArg(k, "path", path, 0))
+	return k.Expects("chdir").Error(
+		stub.CheckArg(k.Stub, "path", path, 0))
 }
 
 func (k *kstub) fchdir(fd int) (err error) {
-	return k.expect("fchdir").error(
+	k.Helper()
-		checkArg(k, "fd", fd, 0))
+	return k.Expects("fchdir").Error(
+		stub.CheckArg(k.Stub, "fd", fd, 0))
 }
 
 func (k *kstub) open(path string, mode int, perm uint32) (fd int, err error) {
-	expect := k.expect("open")
+	k.Helper()
-	return expect.ret.(int), expect.error(
+	expect := k.Expects("open")
-		checkArg(k, "path", path, 0),
+	return expect.Ret.(int), expect.Error(
-		checkArg(k, "mode", mode, 1),
+		stub.CheckArg(k.Stub, "path", path, 0),
-		checkArg(k, "perm", perm, 2))
+		stub.CheckArg(k.Stub, "mode", mode, 1),
+		stub.CheckArg(k.Stub, "perm", perm, 2))
 }
 
 func (k *kstub) close(fd int) (err error) {
-	return k.expect("close").error(
+	k.Helper()
-		checkArg(k, "fd", fd, 0))
+	return k.Expects("close").Error(
+		stub.CheckArg(k.Stub, "fd", fd, 0))
 }
 
 func (k *kstub) pivotRoot(newroot, putold string) (err error) {
-	return k.expect("pivotRoot").error(
+	k.Helper()
-		checkArg(k, "newroot", newroot, 0),
+	return k.Expects("pivotRoot").Error(
-		checkArg(k, "putold", putold, 1))
+		stub.CheckArg(k.Stub, "newroot", newroot, 0),
+		stub.CheckArg(k.Stub, "putold", putold, 1))
 }
 
 func (k *kstub) mount(source, target, fstype string, flags uintptr, data string) (err error) {
-	return k.expect("mount").error(
+	k.Helper()
-		checkArg(k, "source", source, 0),
+	return k.Expects("mount").Error(
-		checkArg(k, "target", target, 1),
+		stub.CheckArg(k.Stub, "source", source, 0),
-		checkArg(k, "fstype", fstype, 2),
+		stub.CheckArg(k.Stub, "target", target, 1),
-		checkArg(k, "flags", flags, 3),
+		stub.CheckArg(k.Stub, "fstype", fstype, 2),
-		checkArg(k, "data", data, 4))
+		stub.CheckArg(k.Stub, "flags", flags, 3),
+		stub.CheckArg(k.Stub, "data", data, 4))
 }
 
 func (k *kstub) unmount(target string, flags int) (err error) {
-	return k.expect("unmount").error(
+	k.Helper()
-		checkArg(k, "target", target, 0),
+	return k.Expects("unmount").Error(
-		checkArg(k, "flags", flags, 1))
+		stub.CheckArg(k.Stub, "target", target, 0),
+		stub.CheckArg(k.Stub, "flags", flags, 1))
 }
 
 func (k *kstub) wait4(pid int, wstatus *syscall.WaitStatus, options int, rusage *syscall.Rusage) (wpid int, err error) {
-	expect := k.expect("wait4")
+	k.Helper()
-	// special case to prevent leaking the wait4 goroutine when testing initEntrypoint
+	expect := k.Expects("wait4")
-	if v, ok := expect.args[4].(int); ok && v == 0xdeadbeef {
+	if v, ok := expect.Args[4].(int); ok {
-		k.t.Log("terminating current goroutine as requested by kexpect")
+		switch v {
-		panic(0xdeadbeef)
+		case stub.PanicExit: // special case to prevent leaking the wait4 goroutine while testing initEntrypoint
+			panic(stub.PanicExit)
+
+		case magicWait4Signal: // block until corresponding signal call
+			if k.wait4signal == nil {
+				panic("kstub not initialised for wait4 simulation")
+			}
+			<-k.wait4signal
+		}
 	}
 
-	wpid = expect.ret.(int)
+	wpid = expect.Ret.(int)
-	err = expect.error(
+	err = expect.Error(
-		checkArg(k, "pid", pid, 0),
+		stub.CheckArg(k.Stub, "pid", pid, 0),
-		checkArg(k, "options", options, 2))
+		stub.CheckArg(k.Stub, "options", options, 2))
 
-	if wstatusV, ok := expect.args[1].(syscall.WaitStatus); wstatus != nil && ok {
+	if wstatusV, ok := expect.Args[1].(syscall.WaitStatus); wstatus != nil && ok {
 		*wstatus = wstatusV
 	}
-	if rusageV, ok := expect.args[3].(syscall.Rusage); rusage != nil && ok {
+	if rusageV, ok := expect.Args[3].(syscall.Rusage); rusage != nil && ok {
 		*rusage = rusageV
 	}
 
@@ -696,53 +695,50 @@ func (k *kstub) wait4(pid int, wstatus *syscall.WaitStatus, options int, rusage
 }
 
 func (k *kstub) printf(format string, v ...any) {
-	if k.expect("printf").error(
+	k.Helper()
-		checkArg(k, "format", format, 0),
+	if k.Expects("printf").Error(
-		checkArgReflect(k, "v", v, 1)) != nil {
+		stub.CheckArg(k.Stub, "format", format, 0),
-		k.t.FailNow()
+		stub.CheckArgReflect(k.Stub, "v", v, 1)) != nil {
+		k.FailNow()
 	}
 }
 
 func (k *kstub) fatal(v ...any) {
-	if k.expect("fatal").error(
+	k.Helper()
-		checkArgReflect(k, "v", v, 0)) != nil {
+	if k.Expects("fatal").Error(
-		k.t.FailNow()
+		stub.CheckArgReflect(k.Stub, "v", v, 0)) != nil {
+		k.FailNow()
 	}
-	panic(0xdeadbeef)
+	panic(stub.PanicExit)
 }
 
 func (k *kstub) fatalf(format string, v ...any) {
-	if k.expect("fatalf").error(
+	k.Helper()
-		checkArg(k, "format", format, 0),
+	if k.Expects("fatalf").Error(
-		checkArgReflect(k, "v", v, 1)) != nil {
+		stub.CheckArg(k.Stub, "format", format, 0),
-		k.t.FailNow()
+		stub.CheckArgReflect(k.Stub, "v", v, 1)) != nil {
+		k.FailNow()
 	}
-	panic(0xdeadbeef)
+	panic(stub.PanicExit)
 }
 
 func (k *kstub) verbose(v ...any) {
-	if k.expect("verbose").error(
+	k.Helper()
-		checkArgReflect(k, "v", v, 0)) != nil {
+	if k.Expects("verbose").Error(
-		k.t.FailNow()
+		stub.CheckArgReflect(k.Stub, "v", v, 0)) != nil {
+		k.FailNow()
 	}
 }
 
 func (k *kstub) verbosef(format string, v ...any) {
-	if k.expect("verbosef").error(
+	k.Helper()
-		checkArg(k, "format", format, 0),
+	if k.Expects("verbosef").Error(
-		checkArgReflect(k, "v", v, 1)) != nil {
+		stub.CheckArg(k.Stub, "format", format, 0),
-		k.t.FailNow()
+		stub.CheckArgReflect(k.Stub, "v", v, 1)) != nil {
+		k.FailNow()
 	}
 }
 
-func (k *kstub) suspend()     { k.expect("suspend") }
+func (k *kstub) suspend()     { k.Helper(); k.Expects("suspend") }
-func (k *kstub) resume() bool { return k.expect("resume").ret.(bool) }
+func (k *kstub) resume() bool { k.Helper(); return k.Expects("resume").Ret.(bool) }
-func (k *kstub) beforeExit()  { k.expect("beforeExit") }
+func (k *kstub) beforeExit()  { k.Helper(); k.Expects("beforeExit") }
-
-func (k *kstub) printBaseErr(err error, fallback string) {
-	if k.expect("printBaseErr").error(
-		checkArgReflect(k, "err", err, 0),
-		checkArg(k, "fallback", fallback, 1)) != nil {
-		k.t.FailNow()
-	}
-}

container/errors.go

@@ -0,0 +1,112 @@
+package container
+
+import (
+	"errors"
+	"os"
+	"syscall"
+
+	"hakurei.app/container/vfs"
+)
+
+// messageFromError returns a printable error message for a supported concrete type.
+func messageFromError(err error) (string, bool) {
+	if m, ok := messagePrefixP[MountError]("cannot ", err); ok {
+		return m, ok
+	}
+	if m, ok := messagePrefixP[os.PathError]("cannot ", err); ok {
+		return m, ok
+	}
+	if m, ok := messagePrefixP[AbsoluteError]("", err); ok {
+		return m, ok
+	}
+	if m, ok := messagePrefix[OpRepeatError]("", err); ok {
+		return m, ok
+	}
+	if m, ok := messagePrefix[OpStateError]("", err); ok {
+		return m, ok
+	}
+
+	if m, ok := messagePrefixP[vfs.DecoderError]("cannot ", err); ok {
+		return m, ok
+	}
+	if m, ok := messagePrefix[TmpfsSizeError]("", err); ok {
+		return m, ok
+	}
+
+	return zeroString, false
+}
+
+// messagePrefix checks and prefixes the error message of a non-pointer error.
+// While this is usable for pointer errors, such use should be avoided as nil check is omitted.
+func messagePrefix[T error](prefix string, err error) (string, bool) {
+	var targetError T
+	if errors.As(err, &targetError) {
+		return prefix + targetError.Error(), true
+	}
+	return zeroString, false
+}
+
+// messagePrefixP checks and prefixes the error message of a pointer error.
+func messagePrefixP[V any, T interface {
+	*V
+	error
+}](prefix string, err error) (string, bool) {
+	var targetError T
+	if errors.As(err, &targetError) && targetError != nil {
+		return prefix + targetError.Error(), true
+	}
+	return zeroString, false
+}
+
+type MountError struct {
+	Source, Target, Fstype string
+
+	Flags uintptr
+	Data  string
+	syscall.Errno
+}
+
+func (e *MountError) Unwrap() error {
+	if e.Errno == 0 {
+		return nil
+	}
+	return e.Errno
+}
+
+func (e *MountError) Error() string {
+	if e.Flags&syscall.MS_BIND != 0 {
+		if e.Flags&syscall.MS_REMOUNT != 0 {
+			return "remount " + e.Target + ": " + e.Errno.Error()
+		}
+		return "bind " + e.Source + " on " + e.Target + ": " + e.Errno.Error()
+	}
+
+	if e.Fstype != FstypeNULL {
+		return "mount " + e.Fstype + " on " + e.Target + ": " + e.Errno.Error()
+	}
+
+	// fallback case: if this is reached, the conditions for it to occur should be handled above
+	return "mount " + e.Target + ": " + e.Errno.Error()
+}
+
+// errnoFallback returns the concrete errno from an error, or a [os.PathError] fallback.
+func errnoFallback(op, path string, err error) (syscall.Errno, *os.PathError) {
+	var errno syscall.Errno
+	if !errors.As(err, &errno) {
+		return 0, &os.PathError{Op: op, Path: path, Err: err}
+	}
+	return errno, nil
+}
+
+// mount wraps syscall.Mount for error handling.
+func mount(source, target, fstype string, flags uintptr, data string) error {
+	err := syscall.Mount(source, target, fstype, flags, data)
+	if err == nil {
+		return nil
+	}
+	if errno, pathError := errnoFallback("mount", target, err); pathError != nil {
+		return pathError
+	} else {
+		return &MountError{source, target, fstype, flags, data, errno}
+	}
+}

container/errors_test.go

@@ -0,0 +1,168 @@
+package container
+
+import (
+	"errors"
+	"os"
+	"reflect"
+	"strconv"
+	"syscall"
+	"testing"
+
+	"hakurei.app/container/stub"
+	"hakurei.app/container/vfs"
+)
+
+func TestMessageFromError(t *testing.T) {
+	testCases := []struct {
+		name   string
+		err    error
+		want   string
+		wantOk bool
+	}{
+		{"mount", &MountError{
+			Source: SourceTmpfsEphemeral,
+			Target: "/sysroot/tmp",
+			Fstype: FstypeTmpfs,
+			Flags:  syscall.MS_NOSUID | syscall.MS_NODEV,
+			Data:   zeroString,
+			Errno:  syscall.EINVAL,
+		}, "cannot mount tmpfs on /sysroot/tmp: invalid argument", true},
+
+		{"path", &os.PathError{
+			Op:   "mount",
+			Path: "/sysroot",
+			Err:  stub.UniqueError(0xdeadbeef),
+		}, "cannot mount /sysroot: unique error 3735928559 injected by the test suite", true},
+
+		{"absolute", &AbsoluteError{"etc/mtab"},
+			`path "etc/mtab" is not absolute`, true},
+
+		{"repeat", OpRepeatError("autoetc"),
+			"autoetc is not repeatable", true},
+
+		{"state", OpStateError("overlay"),
+			"impossible overlay state reached", true},
+
+		{"vfs parse", &vfs.DecoderError{Op: "parse", Line: 0xdeadbeef, Err: &strconv.NumError{Func: "Atoi", Num: "meow", Err: strconv.ErrSyntax}},
+			`cannot parse mountinfo at line 3735928559: numeric field "meow" invalid syntax`, true},
+
+		{"tmpfs", TmpfsSizeError(-1),
+			"tmpfs size -1 out of bounds", true},
+
+		{"unsupported", stub.UniqueError(0xdeadbeef), zeroString, false},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			got, ok := messageFromError(tc.err)
+			if got != tc.want {
+				t.Errorf("messageFromError: %q, want %q", got, tc.want)
+			}
+			if ok != tc.wantOk {
+				t.Errorf("messageFromError: ok = %v, want %v", ok, tc.wantOk)
+			}
+		})
+	}
+}
+
+func TestMountError(t *testing.T) {
+	testCases := []struct {
+		name  string
+		err   error
+		errno syscall.Errno
+		want  string
+	}{
+		{"bind", &MountError{
+			Source: "/host/nix/store",
+			Target: "/sysroot/nix/store",
+			Fstype: FstypeNULL,
+			Flags:  syscall.MS_SILENT | syscall.MS_BIND | syscall.MS_REC,
+			Data:   zeroString,
+			Errno:  syscall.ENOSYS,
+		}, syscall.ENOSYS,
+			"bind /host/nix/store on /sysroot/nix/store: function not implemented"},
+
+		{"remount", &MountError{
+			Source: SourceNone,
+			Target: "/sysroot/nix/store",
+			Fstype: FstypeNULL,
+			Flags:  syscall.MS_SILENT | syscall.MS_BIND | syscall.MS_REMOUNT,
+			Data:   zeroString,
+			Errno:  syscall.EPERM,
+		}, syscall.EPERM,
+			"remount /sysroot/nix/store: operation not permitted"},
+
+		{"overlay", &MountError{
+			Source: SourceOverlay,
+			Target: sysrootPath,
+			Fstype: FstypeOverlay,
+			Data:   `lowerdir=/host/var/lib/planterette/base/debian\:f92c9052`,
+			Errno:  syscall.EINVAL,
+		}, syscall.EINVAL,
+			"mount overlay on /sysroot: invalid argument"},
+
+		{"fallback", &MountError{
+			Source: SourceNone,
+			Target: sysrootPath,
+			Fstype: FstypeNULL,
+			Errno:  syscall.ENOTRECOVERABLE,
+		}, syscall.ENOTRECOVERABLE,
+			"mount /sysroot: state not recoverable"},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Run("is", func(t *testing.T) {
+				if !errors.Is(tc.err, tc.errno) {
+					t.Errorf("Is: %#v is not %v", tc.err, tc.errno)
+				}
+			})
+			t.Run("error", func(t *testing.T) {
+				if got := tc.err.Error(); got != tc.want {
+					t.Errorf("Error: %q, want %q", got, tc.want)
+				}
+			})
+		})
+	}
+
+	t.Run("zero", func(t *testing.T) {
+		if errors.Is(new(MountError), syscall.Errno(0)) {
+			t.Errorf("Is: zero MountError unexpected true")
+		}
+	})
+}
+
+func TestErrnoFallback(t *testing.T) {
+	testCases := []struct {
+		name      string
+		err       error
+		wantErrno syscall.Errno
+		wantPath  *os.PathError
+	}{
+		{"mount", &MountError{
+			Errno: syscall.ENOTRECOVERABLE,
+		}, syscall.ENOTRECOVERABLE, nil},
+
+		{"path errno", &os.PathError{
+			Err: syscall.ETIMEDOUT,
+		}, syscall.ETIMEDOUT, nil},
+
+		{"fallback", stub.UniqueError(0xcafebabe), 0, &os.PathError{
+			Op:   "fallback",
+			Path: "/proc/nonexistent",
+			Err:  stub.UniqueError(0xcafebabe),
+		}},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			errno, err := errnoFallback(tc.name, Nonexistent, tc.err)
+			if errno != tc.wantErrno {
+				t.Errorf("errnoFallback: errno = %v, want %v", errno, tc.wantErrno)
+			}
+			if !reflect.DeepEqual(err, tc.wantPath) {
+				t.Errorf("errnoFallback: pathError = %#v, want %#v", err, tc.wantPath)
+			}
+		})
+	}
+}
+
+// InternalMessageFromError exports messageFromError for other tests.
+func InternalMessageFromError(err error) (string, bool) { return messageFromError(err) }

container/init.go

@@ -47,7 +47,9 @@ type (
 		// apply is called in intermediate root.
 		apply(state *setupState, k syscallDispatcher) error
 
-		prefix() string
+		// prefix returns a log message prefix, and whether this Op prints no identifying message on its own.
+		prefix() (string, bool)
+
 		Is(op Op) bool
 		Valid() bool
 		fmt.Stringer
@@ -68,6 +70,16 @@ const (
 	nrAutoRoot
 )
 
+// OpRepeatError is returned applying a repeated nonrepeatable [Op].
+type OpRepeatError string
+
+func (e OpRepeatError) Error() string { return string(e) + " is not repeatable" }
+
+// OpStateError indicates an impossible internal state has been reached in an [Op].
+type OpStateError string
+
+func (o OpStateError) Error() string { return "impossible " + string(o) + " state reached" }
+
 // initParams are params passed from parent.
 type initParams struct {
 	Params
@@ -106,7 +118,7 @@ func initEntrypoint(k syscallDispatcher, prepareLogger func(prefix string), setV
 		if errors.Is(err, EBADF) {
 			k.fatal("invalid setup descriptor")
 		}
-		if errors.Is(err, ErrNotSet) {
+		if errors.Is(err, ErrReceiveEnv) {
 			k.fatal("HAKUREI_SETUP not set")
 		}
 
@@ -174,10 +186,11 @@ func initEntrypoint(k syscallDispatcher, prepareLogger func(prefix string), setV
 		}
 
 		if err := op.early(state, k); err != nil {
-			k.printBaseErr(err,
+			if m, ok := messageFromError(err); ok {
-				fmt.Sprintf("cannot prepare op at index %d:", i))
+				k.fatal(m)
-			k.beforeExit()
+			} else {
-			k.exit(1)
+				k.fatalf("cannot prepare op at index %d: %v", i, err)
+			}
 		}
 	}
 
@@ -212,12 +225,15 @@ func initEntrypoint(k syscallDispatcher, prepareLogger func(prefix string), setV
 	chdir is allowed but discouraged */
 	for i, op := range *params.Ops {
 		// ops already checked during early setup
-		k.verbosef("%s %s", op.prefix(), op)
+		if prefix, ok := op.prefix(); ok {
+			k.verbosef("%s %s", prefix, op)
+		}
 		if err := op.apply(state, k); err != nil {
-			k.printBaseErr(err,
+			if m, ok := messageFromError(err); ok {
-				fmt.Sprintf("cannot apply op at index %d:", i))
+				k.fatal(m)
-			k.beforeExit()
+			} else {
-			k.exit(1)
+				k.fatalf("cannot apply op at index %d: %v", i, err)
+			}
 		}
 	}
 

container/initbind.go

@@ -43,7 +43,7 @@ func (b *BindMountOp) Valid() bool {
 func (b *BindMountOp) early(_ *setupState, k syscallDispatcher) error {
 	if b.Flags&BindEnsure != 0 {
 		if err := k.mkdirAll(b.Source.String(), 0700); err != nil {
-			return wrapErrSelf(err)
+			return err
 		}
 	}
 
@@ -52,7 +52,7 @@ func (b *BindMountOp) early(_ *setupState, k syscallDispatcher) error {
 			// leave sourceFinal as nil
 			return nil
 		}
-		return wrapErrSelf(err)
+		return err
 	} else {
 		b.sourceFinal, err = NewAbs(pathname)
 		return err
@@ -63,7 +63,7 @@ func (b *BindMountOp) apply(_ *setupState, k syscallDispatcher) error {
 	if b.sourceFinal == nil {
 		if b.Flags&BindOptional == 0 {
 			// unreachable
-			return msg.WrapErr(os.ErrClosed, "impossible bind state reached")
+			return OpStateError("bind")
 		}
 		return nil
 	}
@@ -74,10 +74,10 @@ func (b *BindMountOp) apply(_ *setupState, k syscallDispatcher) error {
 	// this perm value emulates bwrap behaviour as it clears bits from 0755 based on
 	// op->perms which is never set for any bind setup op so always results in 0700
 	if fi, err := k.stat(source); err != nil {
-		return wrapErrSelf(err)
+		return err
 	} else if fi.IsDir() {
 		if err = k.mkdirAll(target, 0700); err != nil {
-			return wrapErrSelf(err)
+			return err
 		}
 	} else if err = k.ensureFile(target, 0444, 0700); err != nil {
 		return err
@@ -91,7 +91,12 @@ func (b *BindMountOp) apply(_ *setupState, k syscallDispatcher) error {
 		flags |= syscall.MS_NODEV
 	}
 
-	return k.bindMount(source, target, flags, b.sourceFinal == b.Target)
+	if b.sourceFinal.String() == b.Target.String() {
+		k.verbosef("mounting %q flags %#x", target, flags)
+	} else {
+		k.verbosef("mounting %q on %q flags %#x", source, target, flags)
+	}
+	return k.bindMount(source, target, flags)
 }
 
 func (b *BindMountOp) Is(op Op) bool {
@@ -101,7 +106,7 @@ func (b *BindMountOp) Is(op Op) bool {
 		b.Target.Is(vb.Target) &&
 		b.Flags == vb.Flags
 }
-func (*BindMountOp) prefix() string { return "mounting" }
+func (*BindMountOp) prefix() (string, bool) { return "mounting", false }
 func (b *BindMountOp) String() string {
 	if b.Source == nil || b.Target == nil {
 		return "<invalid>"

container/initbind_test.go

@@ -5,6 +5,8 @@ import (
 	"os"
 	"syscall"
 	"testing"
+
+	"hakurei.app/container/stub"
 )
 
 func TestBindMountOp(t *testing.T) {
@@ -12,138 +14,156 @@ func TestBindMountOp(t *testing.T) {
 		{"ENOENT not optional", new(Params), &BindMountOp{
 			Source: MustAbs("/bin/"),
 			Target: MustAbs("/bin/"),
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/bin/"}, "", syscall.ENOENT},
+			call("evalSymlinks", stub.ExpectArgs{"/bin/"}, "", syscall.ENOENT),
-		}, wrapErrSelf(syscall.ENOENT), nil, nil},
+		}, syscall.ENOENT, nil, nil},
 
 		{"skip optional", new(Params), &BindMountOp{
 			Source: MustAbs("/bin/"),
 			Target: MustAbs("/bin/"),
 			Flags:  BindOptional,
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/bin/"}, "", syscall.ENOENT},
+			call("evalSymlinks", stub.ExpectArgs{"/bin/"}, "", syscall.ENOENT),
 		}, nil, nil, nil},
 
 		{"success optional", new(Params), &BindMountOp{
 			Source: MustAbs("/bin/"),
 			Target: MustAbs("/bin/"),
 			Flags:  BindOptional,
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/bin/"}, "/usr/bin", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/bin/"}, "/usr/bin", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"stat", expectArgs{"/host/usr/bin"}, isDirFi(true), nil},
+			call("stat", stub.ExpectArgs{"/host/usr/bin"}, isDirFi(true), nil),
-			{"mkdirAll", expectArgs{"/sysroot/bin", os.FileMode(0700)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/bin", os.FileMode(0700)}, nil, nil),
-			{"bindMount", expectArgs{"/host/usr/bin", "/sysroot/bin", uintptr(0x4005), false}, nil, nil},
+			call("verbosef", stub.ExpectArgs{"mounting %q on %q flags %#x", []any{"/host/usr/bin", "/sysroot/bin", uintptr(0x4005)}}, nil, nil),
+			call("bindMount", stub.ExpectArgs{"/host/usr/bin", "/sysroot/bin", uintptr(0x4005), false}, nil, nil),
 		}, nil},
 
 		{"ensureFile device", new(Params), &BindMountOp{
 			Source: MustAbs("/dev/null"),
 			Target: MustAbs("/dev/null"),
 			Flags:  BindWritable | BindDevice,
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/dev/null"}, "/dev/null", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/dev/null"}, "/dev/null", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"stat", expectArgs{"/host/dev/null"}, isDirFi(false), nil},
+			call("stat", stub.ExpectArgs{"/host/dev/null"}, isDirFi(false), nil),
-			{"ensureFile", expectArgs{"/sysroot/dev/null", os.FileMode(0444), os.FileMode(0700)}, nil, errUnique},
+			call("ensureFile", stub.ExpectArgs{"/sysroot/dev/null", os.FileMode(0444), os.FileMode(0700)}, nil, stub.UniqueError(5)),
-		}, errUnique},
+		}, stub.UniqueError(5)},
 
 		{"mkdirAll ensure", new(Params), &BindMountOp{
 			Source: MustAbs("/bin/"),
 			Target: MustAbs("/bin/"),
 			Flags:  BindEnsure,
-		}, []kexpect{
+		}, []stub.Call{
-			{"mkdirAll", expectArgs{"/bin/", os.FileMode(0700)}, nil, errUnique},
+			call("mkdirAll", stub.ExpectArgs{"/bin/", os.FileMode(0700)}, nil, stub.UniqueError(4)),
-		}, wrapErrSelf(errUnique), nil, nil},
+		}, stub.UniqueError(4), nil, nil},
 
 		{"success ensure", new(Params), &BindMountOp{
 			Source: MustAbs("/bin/"),
 			Target: MustAbs("/usr/bin/"),
 			Flags:  BindEnsure,
-		}, []kexpect{
+		}, []stub.Call{
-			{"mkdirAll", expectArgs{"/bin/", os.FileMode(0700)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/bin/", os.FileMode(0700)}, nil, nil),
-			{"evalSymlinks", expectArgs{"/bin/"}, "/usr/bin", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/bin/"}, "/usr/bin", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"stat", expectArgs{"/host/usr/bin"}, isDirFi(true), nil},
+			call("stat", stub.ExpectArgs{"/host/usr/bin"}, isDirFi(true), nil),
-			{"mkdirAll", expectArgs{"/sysroot/usr/bin", os.FileMode(0700)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/usr/bin", os.FileMode(0700)}, nil, nil),
-			{"bindMount", expectArgs{"/host/usr/bin", "/sysroot/usr/bin", uintptr(0x4005), false}, nil, nil},
+			call("verbosef", stub.ExpectArgs{"mounting %q on %q flags %#x", []any{"/host/usr/bin", "/sysroot/usr/bin", uintptr(0x4005)}}, nil, nil),
+			call("bindMount", stub.ExpectArgs{"/host/usr/bin", "/sysroot/usr/bin", uintptr(0x4005), false}, nil, nil),
 		}, nil},
 
 		{"success device ro", new(Params), &BindMountOp{
 			Source: MustAbs("/dev/null"),
 			Target: MustAbs("/dev/null"),
 			Flags:  BindDevice,
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/dev/null"}, "/dev/null", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/dev/null"}, "/dev/null", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"stat", expectArgs{"/host/dev/null"}, isDirFi(false), nil},
+			call("stat", stub.ExpectArgs{"/host/dev/null"}, isDirFi(false), nil),
-			{"ensureFile", expectArgs{"/sysroot/dev/null", os.FileMode(0444), os.FileMode(0700)}, nil, nil},
+			call("ensureFile", stub.ExpectArgs{"/sysroot/dev/null", os.FileMode(0444), os.FileMode(0700)}, nil, nil),
-			{"bindMount", expectArgs{"/host/dev/null", "/sysroot/dev/null", uintptr(0x4001), false}, nil, nil},
+			call("verbosef", stub.ExpectArgs{"mounting %q flags %#x", []any{"/sysroot/dev/null", uintptr(0x4001)}}, nil, nil),
+			call("bindMount", stub.ExpectArgs{"/host/dev/null", "/sysroot/dev/null", uintptr(0x4001), false}, nil, nil),
 		}, nil},
 
 		{"success device", new(Params), &BindMountOp{
 			Source: MustAbs("/dev/null"),
 			Target: MustAbs("/dev/null"),
 			Flags:  BindWritable | BindDevice,
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/dev/null"}, "/dev/null", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/dev/null"}, "/dev/null", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"stat", expectArgs{"/host/dev/null"}, isDirFi(false), nil},
+			call("stat", stub.ExpectArgs{"/host/dev/null"}, isDirFi(false), nil),
-			{"ensureFile", expectArgs{"/sysroot/dev/null", os.FileMode(0444), os.FileMode(0700)}, nil, nil},
+			call("ensureFile", stub.ExpectArgs{"/sysroot/dev/null", os.FileMode(0444), os.FileMode(0700)}, nil, nil),
-			{"bindMount", expectArgs{"/host/dev/null", "/sysroot/dev/null", uintptr(0x4000), false}, nil, nil},
+			call("verbosef", stub.ExpectArgs{"mounting %q flags %#x", []any{"/sysroot/dev/null", uintptr(0x4000)}}, nil, nil),
+			call("bindMount", stub.ExpectArgs{"/host/dev/null", "/sysroot/dev/null", uintptr(0x4000), false}, nil, nil),
 		}, nil},
 
 		{"evalSymlinks", new(Params), &BindMountOp{
 			Source: MustAbs("/bin/"),
 			Target: MustAbs("/bin/"),
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/bin/"}, "/usr/bin", errUnique},
+			call("evalSymlinks", stub.ExpectArgs{"/bin/"}, "/usr/bin", stub.UniqueError(3)),
-		}, wrapErrSelf(errUnique), nil, nil},
+		}, stub.UniqueError(3), nil, nil},
 
 		{"stat", new(Params), &BindMountOp{
 			Source: MustAbs("/bin/"),
 			Target: MustAbs("/bin/"),
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/bin/"}, "/usr/bin", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/bin/"}, "/usr/bin", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"stat", expectArgs{"/host/usr/bin"}, isDirFi(true), errUnique},
+			call("stat", stub.ExpectArgs{"/host/usr/bin"}, isDirFi(true), stub.UniqueError(2)),
-		}, wrapErrSelf(errUnique)},
+		}, stub.UniqueError(2)},
 
 		{"mkdirAll", new(Params), &BindMountOp{
 			Source: MustAbs("/bin/"),
 			Target: MustAbs("/bin/"),
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/bin/"}, "/usr/bin", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/bin/"}, "/usr/bin", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"stat", expectArgs{"/host/usr/bin"}, isDirFi(true), nil},
+			call("stat", stub.ExpectArgs{"/host/usr/bin"}, isDirFi(true), nil),
-			{"mkdirAll", expectArgs{"/sysroot/bin", os.FileMode(0700)}, nil, errUnique},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/bin", os.FileMode(0700)}, nil, stub.UniqueError(1)),
-		}, wrapErrSelf(errUnique)},
+		}, stub.UniqueError(1)},
 
 		{"bindMount", new(Params), &BindMountOp{
 			Source: MustAbs("/bin/"),
 			Target: MustAbs("/bin/"),
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/bin/"}, "/usr/bin", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/bin/"}, "/usr/bin", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"stat", expectArgs{"/host/usr/bin"}, isDirFi(true), nil},
+			call("stat", stub.ExpectArgs{"/host/usr/bin"}, isDirFi(true), nil),
-			{"mkdirAll", expectArgs{"/sysroot/bin", os.FileMode(0700)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/bin", os.FileMode(0700)}, nil, nil),
-			{"bindMount", expectArgs{"/host/usr/bin", "/sysroot/bin", uintptr(0x4005), false}, nil, errUnique},
+			call("verbosef", stub.ExpectArgs{"mounting %q on %q flags %#x", []any{"/host/usr/bin", "/sysroot/bin", uintptr(0x4005)}}, nil, nil),
-		}, errUnique},
+			call("bindMount", stub.ExpectArgs{"/host/usr/bin", "/sysroot/bin", uintptr(0x4005), false}, nil, stub.UniqueError(0)),
+		}, stub.UniqueError(0)},
+
+		{"success eval equals", new(Params), &BindMountOp{
+			Source: MustAbs("/bin/"),
+			Target: MustAbs("/bin/"),
+		}, []stub.Call{
+			call("evalSymlinks", stub.ExpectArgs{"/bin/"}, "/bin", nil),
+		}, nil, []stub.Call{
+			call("stat", stub.ExpectArgs{"/host/bin"}, isDirFi(true), nil),
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/bin", os.FileMode(0700)}, nil, nil),
+			call("verbosef", stub.ExpectArgs{"mounting %q on %q flags %#x", []any{"/host/bin", "/sysroot/bin", uintptr(0x4005)}}, nil, nil),
+			call("bindMount", stub.ExpectArgs{"/host/bin", "/sysroot/bin", uintptr(0x4005), false}, nil, nil),
+		}, nil},
 
 		{"success", new(Params), &BindMountOp{
 			Source: MustAbs("/bin/"),
 			Target: MustAbs("/bin/"),
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/bin/"}, "/usr/bin", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/bin/"}, "/usr/bin", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"stat", expectArgs{"/host/usr/bin"}, isDirFi(true), nil},
+			call("stat", stub.ExpectArgs{"/host/usr/bin"}, isDirFi(true), nil),
-			{"mkdirAll", expectArgs{"/sysroot/bin", os.FileMode(0700)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/bin", os.FileMode(0700)}, nil, nil),
-			{"bindMount", expectArgs{"/host/usr/bin", "/sysroot/bin", uintptr(0x4005), false}, nil, nil},
+			call("verbosef", stub.ExpectArgs{"mounting %q on %q flags %#x", []any{"/host/usr/bin", "/sysroot/bin", uintptr(0x4005)}}, nil, nil),
+			call("bindMount", stub.ExpectArgs{"/host/usr/bin", "/sysroot/bin", uintptr(0x4005), false}, nil, nil),
 		}, nil},
 	})
 
 	t.Run("unreachable", func(t *testing.T) {
 		t.Run("nil sourceFinal not optional", func(t *testing.T) {
-			wantErr := msg.WrapErr(os.ErrClosed, "impossible bind state reached")
+			wantErr := OpStateError("bind")
 			if err := new(BindMountOp).apply(nil, nil); !errors.Is(err, wantErr) {
 				t.Errorf("apply: error = %v, want %v", err, wantErr)
 			}

container/initdev.go

@@ -49,7 +49,6 @@ func (d *MountDevOp) apply(state *setupState, k syscallDispatcher) error {
 			toHost(FHSDev+name),
 			targetPath,
 			0,
-			true,
 		); err != nil {
 			return err
 		}
@@ -59,7 +58,7 @@ func (d *MountDevOp) apply(state *setupState, k syscallDispatcher) error {
 			FHSProc+"self/fd/"+string(rune(i+'0')),
 			path.Join(target, name),
 		); err != nil {
-			return wrapErrSelf(err)
+			return err
 		}
 	}
 	for _, pair := range [][2]string{
@@ -68,21 +67,21 @@ func (d *MountDevOp) apply(state *setupState, k syscallDispatcher) error {
 		{"pts/ptmx", "ptmx"},
 	} {
 		if err := k.symlink(pair[0], path.Join(target, pair[1])); err != nil {
-			return wrapErrSelf(err)
+			return err
 		}
 	}
 
+	devShmPath := path.Join(target, "shm")
 	devPtsPath := path.Join(target, "pts")
-	for _, name := range []string{path.Join(target, "shm"), devPtsPath} {
+	for _, name := range []string{devShmPath, devPtsPath} {
 		if err := k.mkdir(name, state.ParentPerm); err != nil {
-			return wrapErrSelf(err)
+			return err
 		}
 	}
 
 	if err := k.mount(SourceDevpts, devPtsPath, FstypeDevpts, MS_NOSUID|MS_NOEXEC,
 		"newinstance,ptmxmode=0666,mode=620"); err != nil {
-		return wrapErrSuffix(err,
+		return err
-			fmt.Sprintf("cannot mount devpts on %q:", devPtsPath))
 	}
 
 	if state.RetainSession {
@@ -92,12 +91,11 @@ func (d *MountDevOp) apply(state *setupState, k syscallDispatcher) error {
 				return err
 			}
 			if name, err := k.readlink(hostProc.stdout()); err != nil {
-				return wrapErrSelf(err)
+				return err
 			} else if err = k.bindMount(
 				toHost(name),
 				consolePath,
 				0,
-				false,
 			); err != nil {
 				return err
 			}
@@ -107,18 +105,21 @@ func (d *MountDevOp) apply(state *setupState, k syscallDispatcher) error {
 	if d.Mqueue {
 		mqueueTarget := path.Join(target, "mqueue")
 		if err := k.mkdir(mqueueTarget, state.ParentPerm); err != nil {
-			return wrapErrSelf(err)
+			return err
 		}
 		if err := k.mount(SourceMqueue, mqueueTarget, FstypeMqueue, MS_NOSUID|MS_NOEXEC|MS_NODEV, zeroString); err != nil {
-			return wrapErrSuffix(err, "cannot mount mqueue:")
+			return err
 		}
 	}
 
 	if d.Write {
 		return nil
 	}
-	return wrapErrSuffix(k.remount(target, MS_RDONLY),
+
-		fmt.Sprintf("cannot remount %q:", target))
+	if err := k.remount(target, MS_RDONLY); err != nil {
+		return err
+	}
+	return k.mountTmpfs(SourceTmpfs, devShmPath, MS_NOSUID|MS_NODEV, 0, 01777)
 }
 
 func (d *MountDevOp) Is(op Op) bool {
@@ -128,7 +129,7 @@ func (d *MountDevOp) Is(op Op) bool {
 		d.Mqueue == vd.Mqueue &&
 		d.Write == vd.Write
 }
-func (*MountDevOp) prefix() string { return "mounting" }
+func (*MountDevOp) prefix() (string, bool) { return "mounting", true }
 func (d *MountDevOp) String() string {
 	if d.Mqueue {
 		return fmt.Sprintf("dev on %q with mqueue", d.Target)

container/initmkdir.go

@@ -23,7 +23,7 @@ type MkdirOp struct {
 func (m *MkdirOp) Valid() bool                                { return m != nil && m.Path != nil }
 func (m *MkdirOp) early(*setupState, syscallDispatcher) error { return nil }
 func (m *MkdirOp) apply(_ *setupState, k syscallDispatcher) error {
-	return wrapErrSelf(k.mkdirAll(toSysroot(m.Path.String()), m.Perm))
+	return k.mkdirAll(toSysroot(m.Path.String()), m.Perm)
 }
 
 func (m *MkdirOp) Is(op Op) bool {
@@ -32,5 +32,5 @@ func (m *MkdirOp) Is(op Op) bool {
 		m.Path.Is(vm.Path) &&
 		m.Perm == vm.Perm
 }
-func (*MkdirOp) prefix() string   { return "creating" }
+func (*MkdirOp) prefix() (string, bool) { return "creating", true }
-func (m *MkdirOp) String() string { return fmt.Sprintf("directory %q perm %s", m.Path, m.Perm) }
+func (m *MkdirOp) String() string       { return fmt.Sprintf("directory %q perm %s", m.Path, m.Perm) }

container/initmkdir_test.go

@@ -3,6 +3,8 @@ package container
 import (
 	"os"
 	"testing"
+
+	"hakurei.app/container/stub"
 )
 
 func TestMkdirOp(t *testing.T) {
@@ -10,8 +12,8 @@ func TestMkdirOp(t *testing.T) {
 		{"success", new(Params), &MkdirOp{
 			Path: MustAbs("/.hakurei"),
 			Perm: 0500,
-		}, nil, nil, []kexpect{
+		}, nil, nil, []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot/.hakurei", os.FileMode(0500)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/.hakurei", os.FileMode(0500)}, nil, nil),
 		}, nil},
 	})
 

container/initoverlay.go

@@ -3,7 +3,6 @@ package container
 import (
 	"encoding/gob"
 	"fmt"
-	"io/fs"
 	"slices"
 	"strings"
 )
@@ -19,6 +18,39 @@ const (
 
 func init() { gob.Register(new(MountOverlayOp)) }
 
+const (
+	// OverlayEphemeralUnexpectedUpper is set when [MountOverlayOp.Work] is nil
+	// and [MountOverlayOp.Upper] holds an unexpected value.
+	OverlayEphemeralUnexpectedUpper = iota
+	// OverlayReadonlyLower is set when [MountOverlayOp.Lower] contains less than
+	// two entries when mounting readonly.
+	OverlayReadonlyLower
+	// OverlayEmptyLower is set when [MountOverlayOp.Lower] has length of zero.
+	OverlayEmptyLower
+)
+
+// OverlayArgumentError is returned for [MountOverlayOp] supplied with invalid argument.
+type OverlayArgumentError struct {
+	Type  uintptr
+	Value string
+}
+
+func (e *OverlayArgumentError) Error() string {
+	switch e.Type {
+	case OverlayEphemeralUnexpectedUpper:
+		return fmt.Sprintf("upperdir has unexpected value %q", e.Value)
+
+	case OverlayReadonlyLower:
+		return "readonly overlay requires at least two lowerdir"
+
+	case OverlayEmptyLower:
+		return "overlay requires at least one lowerdir"
+
+	default:
+		return fmt.Sprintf("invalid overlay argument error %#x", e.Type)
+	}
+}
+
 // Overlay appends an [Op] that mounts the overlay pseudo filesystem on [MountOverlayOp.Target].
 func (f *Ops) Overlay(target, state, work *Absolute, layers ...*Absolute) *Ops {
 	*f = append(*f, &MountOverlayOp{
@@ -89,7 +121,7 @@ func (o *MountOverlayOp) early(_ *setupState, k syscallDispatcher) error {
 			o.ephemeral = true // intermediate root not yet available
 
 		default:
-			return msg.WrapErr(fs.ErrInvalid, fmt.Sprintf("upperdir has unexpected value %q", o.Upper))
+			return &OverlayArgumentError{OverlayEphemeralUnexpectedUpper, o.Upper.String()}
 		}
 	}
 	// readonly handled in apply
@@ -97,12 +129,12 @@ func (o *MountOverlayOp) early(_ *setupState, k syscallDispatcher) error {
 	if !o.ephemeral {
 		if o.Upper != o.Work && (o.Upper == nil || o.Work == nil) {
 			// unreachable
-			return msg.WrapErr(fs.ErrClosed, "impossible overlay state reached")
+			return OpStateError("overlay")
 		}
 
 		if o.Upper != nil {
 			if v, err := k.evalSymlinks(o.Upper.String()); err != nil {
-				return wrapErrSelf(err)
+				return err
 			} else {
 				o.upper = EscapeOverlayDataSegment(toHost(v))
 			}
@@ -110,7 +142,7 @@ func (o *MountOverlayOp) early(_ *setupState, k syscallDispatcher) error {
 
 		if o.Work != nil {
 			if v, err := k.evalSymlinks(o.Work.String()); err != nil {
-				return wrapErrSelf(err)
+				return err
 			} else {
 				o.work = EscapeOverlayDataSegment(toHost(v))
 			}
@@ -120,7 +152,7 @@ func (o *MountOverlayOp) early(_ *setupState, k syscallDispatcher) error {
 	o.lower = make([]string, len(o.Lower))
 	for i, a := range o.Lower { // nil checked in Valid
 		if v, err := k.evalSymlinks(a.String()); err != nil {
-			return wrapErrSelf(err)
+			return err
 		} else {
 			o.lower[i] = EscapeOverlayDataSegment(toHost(v))
 		}
@@ -134,17 +166,17 @@ func (o *MountOverlayOp) apply(state *setupState, k syscallDispatcher) error {
 		target = toSysroot(target)
 	}
 	if err := k.mkdirAll(target, state.ParentPerm); err != nil {
-		return wrapErrSelf(err)
+		return err
 	}
 
 	if o.ephemeral {
 		var err error
 		// these directories are created internally, therefore early (absolute, symlink, prefix, escape) is bypassed
 		if o.upper, err = k.mkdirTemp(FHSRoot, intermediatePatternOverlayUpper); err != nil {
-			return wrapErrSelf(err)
+			return err
 		}
 		if o.work, err = k.mkdirTemp(FHSRoot, intermediatePatternOverlayWork); err != nil {
-			return wrapErrSelf(err)
+			return err
 		}
 	}
 
@@ -152,12 +184,12 @@ func (o *MountOverlayOp) apply(state *setupState, k syscallDispatcher) error {
 
 	if o.upper == zeroString && o.work == zeroString { // readonly
 		if len(o.Lower) < 2 {
-			return msg.WrapErr(fs.ErrInvalid, "readonly overlay requires at least two lowerdir")
+			return &OverlayArgumentError{OverlayReadonlyLower, zeroString}
 		}
 		// "upperdir=" and "workdir=" may be omitted. In that case the overlay will be read-only
 	} else {
 		if len(o.Lower) == 0 {
-			return msg.WrapErr(fs.ErrInvalid, "overlay requires at least one lowerdir")
+			return &OverlayArgumentError{OverlayEmptyLower, zeroString}
 		}
 		options = append(options,
 			OptionOverlayUpperdir+"="+o.upper,
@@ -167,8 +199,7 @@ func (o *MountOverlayOp) apply(state *setupState, k syscallDispatcher) error {
 		OptionOverlayLowerdir+"="+strings.Join(o.lower, SpecialOverlayPath),
 		OptionOverlayUserxattr)
 
-	return wrapErrSuffix(k.mount(SourceOverlay, target, FstypeOverlay, 0, strings.Join(options, SpecialOverlayOption)),
+	return k.mount(SourceOverlay, target, FstypeOverlay, 0, strings.Join(options, SpecialOverlayOption))
-		fmt.Sprintf("cannot mount overlay on %q:", o.Target))
 }
 
 func (o *MountOverlayOp) Is(op Op) bool {
@@ -178,7 +209,7 @@ func (o *MountOverlayOp) Is(op Op) bool {
 		slices.EqualFunc(o.Lower, vo.Lower, func(a *Absolute, v *Absolute) bool { return a.Is(v) }) &&
 		o.Upper.Is(vo.Upper) && o.Work.Is(vo.Work)
 }
-func (*MountOverlayOp) prefix() string { return "mounting" }
+func (*MountOverlayOp) prefix() (string, bool) { return "mounting", true }
 func (o *MountOverlayOp) String() string {
 	return fmt.Sprintf("overlay on %q with %d layers", o.Target, len(o.Lower))
 }

container/initoverlay_test.go

@@ -2,12 +2,40 @@ package container
 
 import (
 	"errors"
-	"io/fs"
 	"os"
 	"testing"
+
+	"hakurei.app/container/stub"
 )
 
 func TestMountOverlayOp(t *testing.T) {
+	t.Run("argument error", func(t *testing.T) {
+		testCases := []struct {
+			name string
+			err  *OverlayArgumentError
+			want string
+		}{
+			{"unexpected upper", &OverlayArgumentError{OverlayEphemeralUnexpectedUpper, "/proc/"},
+				`upperdir has unexpected value "/proc/"`},
+
+			{"lower ro short", &OverlayArgumentError{OverlayReadonlyLower, zeroString},
+				"readonly overlay requires at least two lowerdir"},
+
+			{"lower short", &OverlayArgumentError{OverlayEmptyLower, zeroString},
+				"overlay requires at least one lowerdir"},
+
+			{"oob", &OverlayArgumentError{0xdeadbeef, zeroString},
+				"invalid overlay argument error 0xdeadbeef"},
+		}
+		for _, tc := range testCases {
+			t.Run(tc.name, func(t *testing.T) {
+				if got := tc.err.Error(); got != tc.want {
+					t.Errorf("Error: %q, want %q", got, tc.want)
+				}
+			})
+		}
+	})
+
 	checkOpBehaviour(t, []opBehaviourTestCase{
 		{"mkdirTemp invalid ephemeral", &Params{ParentPerm: 0705}, &MountOverlayOp{
 			Target: MustAbs("/"),
@@ -16,7 +44,7 @@ func TestMountOverlayOp(t *testing.T) {
 				MustAbs("/var/lib/planterette/app/org.chromium.Chromium@debian:f92c9052"),
 			},
 			Upper: MustAbs("/proc/"),
-		}, nil, msg.WrapErr(fs.ErrInvalid, `upperdir has unexpected value "/proc/"`), nil, nil},
+		}, nil, &OverlayArgumentError{OverlayEphemeralUnexpectedUpper, "/proc/"}, nil, nil},
 
 		{"mkdirTemp upper ephemeral", &Params{ParentPerm: 0705}, &MountOverlayOp{
 			Target: MustAbs("/"),
@@ -25,13 +53,13 @@ func TestMountOverlayOp(t *testing.T) {
 				MustAbs("/var/lib/planterette/app/org.chromium.Chromium@debian:f92c9052"),
 			},
 			Upper: MustAbs("/"),
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/var/lib/planterette/base/debian:f92c9052"}, "/var/lib/planterette/base/debian:f92c9052", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/var/lib/planterette/base/debian:f92c9052"}, "/var/lib/planterette/base/debian:f92c9052", nil),
-			{"evalSymlinks", expectArgs{"/var/lib/planterette/app/org.chromium.Chromium@debian:f92c9052"}, "/var/lib/planterette/app/org.chromium.Chromium@debian:f92c9052", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/var/lib/planterette/app/org.chromium.Chromium@debian:f92c9052"}, "/var/lib/planterette/app/org.chromium.Chromium@debian:f92c9052", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot", os.FileMode(0705)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot", os.FileMode(0705)}, nil, nil),
-			{"mkdirTemp", expectArgs{"/", "overlay.upper.*"}, "overlay.upper.32768", errUnique},
+			call("mkdirTemp", stub.ExpectArgs{"/", "overlay.upper.*"}, "overlay.upper.32768", stub.UniqueError(6)),
-		}, wrapErrSelf(errUnique)},
+		}, stub.UniqueError(6)},
 
 		{"mkdirTemp work ephemeral", &Params{ParentPerm: 0705}, &MountOverlayOp{
 			Target: MustAbs("/"),
@@ -40,14 +68,14 @@ func TestMountOverlayOp(t *testing.T) {
 				MustAbs("/var/lib/planterette/app/org.chromium.Chromium@debian:f92c9052"),
 			},
 			Upper: MustAbs("/"),
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/var/lib/planterette/base/debian:f92c9052"}, "/var/lib/planterette/base/debian:f92c9052", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/var/lib/planterette/base/debian:f92c9052"}, "/var/lib/planterette/base/debian:f92c9052", nil),
-			{"evalSymlinks", expectArgs{"/var/lib/planterette/app/org.chromium.Chromium@debian:f92c9052"}, "/var/lib/planterette/app/org.chromium.Chromium@debian:f92c9052", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/var/lib/planterette/app/org.chromium.Chromium@debian:f92c9052"}, "/var/lib/planterette/app/org.chromium.Chromium@debian:f92c9052", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot", os.FileMode(0705)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot", os.FileMode(0705)}, nil, nil),
-			{"mkdirTemp", expectArgs{"/", "overlay.upper.*"}, "overlay.upper.32768", nil},
+			call("mkdirTemp", stub.ExpectArgs{"/", "overlay.upper.*"}, "overlay.upper.32768", nil),
-			{"mkdirTemp", expectArgs{"/", "overlay.work.*"}, "overlay.work.32768", errUnique},
+			call("mkdirTemp", stub.ExpectArgs{"/", "overlay.work.*"}, "overlay.work.32768", stub.UniqueError(5)),
-		}, wrapErrSelf(errUnique)},
+		}, stub.UniqueError(5)},
 
 		{"success ephemeral", &Params{ParentPerm: 0705}, &MountOverlayOp{
 			Target: MustAbs("/"),
@@ -56,20 +84,20 @@ func TestMountOverlayOp(t *testing.T) {
 				MustAbs("/var/lib/planterette/app/org.chromium.Chromium@debian:f92c9052"),
 			},
 			Upper: MustAbs("/"),
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/var/lib/planterette/base/debian:f92c9052"}, "/var/lib/planterette/base/debian:f92c9052", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/var/lib/planterette/base/debian:f92c9052"}, "/var/lib/planterette/base/debian:f92c9052", nil),
-			{"evalSymlinks", expectArgs{"/var/lib/planterette/app/org.chromium.Chromium@debian:f92c9052"}, "/var/lib/planterette/app/org.chromium.Chromium@debian:f92c9052", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/var/lib/planterette/app/org.chromium.Chromium@debian:f92c9052"}, "/var/lib/planterette/app/org.chromium.Chromium@debian:f92c9052", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot", os.FileMode(0705)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot", os.FileMode(0705)}, nil, nil),
-			{"mkdirTemp", expectArgs{"/", "overlay.upper.*"}, "overlay.upper.32768", nil},
+			call("mkdirTemp", stub.ExpectArgs{"/", "overlay.upper.*"}, "overlay.upper.32768", nil),
-			{"mkdirTemp", expectArgs{"/", "overlay.work.*"}, "overlay.work.32768", nil},
+			call("mkdirTemp", stub.ExpectArgs{"/", "overlay.work.*"}, "overlay.work.32768", nil),
-			{"mount", expectArgs{"overlay", "/sysroot", "overlay", uintptr(0), "" +
+			call("mount", stub.ExpectArgs{"overlay", "/sysroot", "overlay", uintptr(0), "" +
 				"upperdir=overlay.upper.32768," +
 				"workdir=overlay.work.32768," +
 				"lowerdir=" +
 				`/host/var/lib/planterette/base/debian\:f92c9052:` +
 				`/host/var/lib/planterette/app/org.chromium.Chromium@debian\:f92c9052,` +
-				"userxattr"}, nil, nil},
+				"userxattr"}, nil, nil),
 		}, nil},
 
 		{"short lower ro", &Params{ParentPerm: 0755}, &MountOverlayOp{
@@ -77,11 +105,11 @@ func TestMountOverlayOp(t *testing.T) {
 			Lower: []*Absolute{
 				MustAbs("/mnt-root/nix/.ro-store"),
 			},
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.ro-store"}, "/mnt-root/nix/.ro-store", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.ro-store"}, "/mnt-root/nix/.ro-store", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot/nix/store", os.FileMode(0755)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/nix/store", os.FileMode(0755)}, nil, nil),
-		}, msg.WrapErr(fs.ErrInvalid, "readonly overlay requires at least two lowerdir")},
+		}, &OverlayArgumentError{OverlayReadonlyLower, zeroString}},
 
 		{"success ro noPrefix", &Params{ParentPerm: 0755}, &MountOverlayOp{
 			Target: MustAbs("/nix/store"),
@@ -90,16 +118,16 @@ func TestMountOverlayOp(t *testing.T) {
 				MustAbs("/mnt-root/nix/.ro-store0"),
 			},
 			noPrefix: true,
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.ro-store"}, "/mnt-root/nix/.ro-store", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.ro-store"}, "/mnt-root/nix/.ro-store", nil),
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.ro-store0"}, "/mnt-root/nix/.ro-store0", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.ro-store0"}, "/mnt-root/nix/.ro-store0", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"mkdirAll", expectArgs{"/nix/store", os.FileMode(0755)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/nix/store", os.FileMode(0755)}, nil, nil),
-			{"mount", expectArgs{"overlay", "/nix/store", "overlay", uintptr(0), "" +
+			call("mount", stub.ExpectArgs{"overlay", "/nix/store", "overlay", uintptr(0), "" +
 				"lowerdir=" +
 				"/host/mnt-root/nix/.ro-store:" +
 				"/host/mnt-root/nix/.ro-store0," +
-				"userxattr"}, nil, nil},
+				"userxattr"}, nil, nil),
 		}, nil},
 
 		{"success ro", &Params{ParentPerm: 0755}, &MountOverlayOp{
@@ -108,102 +136,102 @@ func TestMountOverlayOp(t *testing.T) {
 				MustAbs("/mnt-root/nix/.ro-store"),
 				MustAbs("/mnt-root/nix/.ro-store0"),
 			},
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.ro-store"}, "/mnt-root/nix/.ro-store", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.ro-store"}, "/mnt-root/nix/.ro-store", nil),
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.ro-store0"}, "/mnt-root/nix/.ro-store0", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.ro-store0"}, "/mnt-root/nix/.ro-store0", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot/nix/store", os.FileMode(0755)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/nix/store", os.FileMode(0755)}, nil, nil),
-			{"mount", expectArgs{"overlay", "/sysroot/nix/store", "overlay", uintptr(0), "" +
+			call("mount", stub.ExpectArgs{"overlay", "/sysroot/nix/store", "overlay", uintptr(0), "" +
 				"lowerdir=" +
 				"/host/mnt-root/nix/.ro-store:" +
 				"/host/mnt-root/nix/.ro-store0," +
-				"userxattr"}, nil, nil},
+				"userxattr"}, nil, nil),
 		}, nil},
 
 		{"nil lower", &Params{ParentPerm: 0700}, &MountOverlayOp{
 			Target: MustAbs("/nix/store"),
 			Upper:  MustAbs("/mnt-root/nix/.rw-store/upper"),
 			Work:   MustAbs("/mnt-root/nix/.rw-store/work"),
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.rw-store/upper"}, "/mnt-root/nix/.rw-store/.upper", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.rw-store/upper"}, "/mnt-root/nix/.rw-store/.upper", nil),
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.rw-store/work"}, "/mnt-root/nix/.rw-store/.work", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.rw-store/work"}, "/mnt-root/nix/.rw-store/.work", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot/nix/store", os.FileMode(0700)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/nix/store", os.FileMode(0700)}, nil, nil),
-		}, msg.WrapErr(fs.ErrInvalid, "overlay requires at least one lowerdir")},
+		}, &OverlayArgumentError{OverlayEmptyLower, zeroString}},
 
 		{"evalSymlinks upper", &Params{ParentPerm: 0700}, &MountOverlayOp{
 			Target: MustAbs("/nix/store"),
 			Lower:  []*Absolute{MustAbs("/mnt-root/nix/.ro-store")},
 			Upper:  MustAbs("/mnt-root/nix/.rw-store/upper"),
 			Work:   MustAbs("/mnt-root/nix/.rw-store/work"),
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.rw-store/upper"}, "/mnt-root/nix/.rw-store/.upper", errUnique},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.rw-store/upper"}, "/mnt-root/nix/.rw-store/.upper", stub.UniqueError(4)),
-		}, wrapErrSelf(errUnique), nil, nil},
+		}, stub.UniqueError(4), nil, nil},
 
 		{"evalSymlinks work", &Params{ParentPerm: 0700}, &MountOverlayOp{
 			Target: MustAbs("/nix/store"),
 			Lower:  []*Absolute{MustAbs("/mnt-root/nix/.ro-store")},
 			Upper:  MustAbs("/mnt-root/nix/.rw-store/upper"),
 			Work:   MustAbs("/mnt-root/nix/.rw-store/work"),
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.rw-store/upper"}, "/mnt-root/nix/.rw-store/.upper", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.rw-store/upper"}, "/mnt-root/nix/.rw-store/.upper", nil),
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.rw-store/work"}, "/mnt-root/nix/.rw-store/.work", errUnique},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.rw-store/work"}, "/mnt-root/nix/.rw-store/.work", stub.UniqueError(3)),
-		}, wrapErrSelf(errUnique), nil, nil},
+		}, stub.UniqueError(3), nil, nil},
 
 		{"evalSymlinks lower", &Params{ParentPerm: 0700}, &MountOverlayOp{
 			Target: MustAbs("/nix/store"),
 			Lower:  []*Absolute{MustAbs("/mnt-root/nix/.ro-store")},
 			Upper:  MustAbs("/mnt-root/nix/.rw-store/upper"),
 			Work:   MustAbs("/mnt-root/nix/.rw-store/work"),
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.rw-store/upper"}, "/mnt-root/nix/.rw-store/.upper", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.rw-store/upper"}, "/mnt-root/nix/.rw-store/.upper", nil),
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.rw-store/work"}, "/mnt-root/nix/.rw-store/.work", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.rw-store/work"}, "/mnt-root/nix/.rw-store/.work", nil),
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.ro-store"}, "/mnt-root/nix/ro-store", errUnique},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.ro-store"}, "/mnt-root/nix/ro-store", stub.UniqueError(2)),
-		}, wrapErrSelf(errUnique), nil, nil},
+		}, stub.UniqueError(2), nil, nil},
 
 		{"mkdirAll", &Params{ParentPerm: 0700}, &MountOverlayOp{
 			Target: MustAbs("/nix/store"),
 			Lower:  []*Absolute{MustAbs("/mnt-root/nix/.ro-store")},
 			Upper:  MustAbs("/mnt-root/nix/.rw-store/upper"),
 			Work:   MustAbs("/mnt-root/nix/.rw-store/work"),
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.rw-store/upper"}, "/mnt-root/nix/.rw-store/.upper", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.rw-store/upper"}, "/mnt-root/nix/.rw-store/.upper", nil),
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.rw-store/work"}, "/mnt-root/nix/.rw-store/.work", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.rw-store/work"}, "/mnt-root/nix/.rw-store/.work", nil),
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.ro-store"}, "/mnt-root/nix/ro-store", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.ro-store"}, "/mnt-root/nix/ro-store", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot/nix/store", os.FileMode(0700)}, nil, errUnique},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/nix/store", os.FileMode(0700)}, nil, stub.UniqueError(1)),
-		}, wrapErrSelf(errUnique)},
+		}, stub.UniqueError(1)},
 
 		{"mount", &Params{ParentPerm: 0700}, &MountOverlayOp{
 			Target: MustAbs("/nix/store"),
 			Lower:  []*Absolute{MustAbs("/mnt-root/nix/.ro-store")},
 			Upper:  MustAbs("/mnt-root/nix/.rw-store/upper"),
 			Work:   MustAbs("/mnt-root/nix/.rw-store/work"),
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.rw-store/upper"}, "/mnt-root/nix/.rw-store/.upper", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.rw-store/upper"}, "/mnt-root/nix/.rw-store/.upper", nil),
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.rw-store/work"}, "/mnt-root/nix/.rw-store/.work", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.rw-store/work"}, "/mnt-root/nix/.rw-store/.work", nil),
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.ro-store"}, "/mnt-root/nix/ro-store", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.ro-store"}, "/mnt-root/nix/ro-store", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot/nix/store", os.FileMode(0700)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/nix/store", os.FileMode(0700)}, nil, nil),
-			{"mount", expectArgs{"overlay", "/sysroot/nix/store", "overlay", uintptr(0), "upperdir=/host/mnt-root/nix/.rw-store/.upper,workdir=/host/mnt-root/nix/.rw-store/.work,lowerdir=/host/mnt-root/nix/ro-store,userxattr"}, nil, errUnique},
+			call("mount", stub.ExpectArgs{"overlay", "/sysroot/nix/store", "overlay", uintptr(0), "upperdir=/host/mnt-root/nix/.rw-store/.upper,workdir=/host/mnt-root/nix/.rw-store/.work,lowerdir=/host/mnt-root/nix/ro-store,userxattr"}, nil, stub.UniqueError(0)),
-		}, wrapErrSuffix(errUnique, `cannot mount overlay on "/nix/store":`)},
+		}, stub.UniqueError(0)},
 
 		{"success single layer", &Params{ParentPerm: 0700}, &MountOverlayOp{
 			Target: MustAbs("/nix/store"),
 			Lower:  []*Absolute{MustAbs("/mnt-root/nix/.ro-store")},
 			Upper:  MustAbs("/mnt-root/nix/.rw-store/upper"),
 			Work:   MustAbs("/mnt-root/nix/.rw-store/work"),
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.rw-store/upper"}, "/mnt-root/nix/.rw-store/.upper", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.rw-store/upper"}, "/mnt-root/nix/.rw-store/.upper", nil),
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.rw-store/work"}, "/mnt-root/nix/.rw-store/.work", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.rw-store/work"}, "/mnt-root/nix/.rw-store/.work", nil),
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.ro-store"}, "/mnt-root/nix/ro-store", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.ro-store"}, "/mnt-root/nix/ro-store", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot/nix/store", os.FileMode(0700)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/nix/store", os.FileMode(0700)}, nil, nil),
-			{"mount", expectArgs{"overlay", "/sysroot/nix/store", "overlay", uintptr(0), "" +
+			call("mount", stub.ExpectArgs{"overlay", "/sysroot/nix/store", "overlay", uintptr(0), "" +
 				"upperdir=/host/mnt-root/nix/.rw-store/.upper," +
 				"workdir=/host/mnt-root/nix/.rw-store/.work," +
 				"lowerdir=/host/mnt-root/nix/ro-store," +
-				"userxattr"}, nil, nil},
+				"userxattr"}, nil, nil),
 		}, nil},
 
 		{"success", &Params{ParentPerm: 0700}, &MountOverlayOp{
@@ -217,17 +245,17 @@ func TestMountOverlayOp(t *testing.T) {
 			},
 			Upper: MustAbs("/mnt-root/nix/.rw-store/upper"),
 			Work:  MustAbs("/mnt-root/nix/.rw-store/work"),
-		}, []kexpect{
+		}, []stub.Call{
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.rw-store/upper"}, "/mnt-root/nix/.rw-store/.upper", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.rw-store/upper"}, "/mnt-root/nix/.rw-store/.upper", nil),
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.rw-store/work"}, "/mnt-root/nix/.rw-store/.work", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.rw-store/work"}, "/mnt-root/nix/.rw-store/.work", nil),
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.ro-store"}, "/mnt-root/nix/ro-store", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.ro-store"}, "/mnt-root/nix/ro-store", nil),
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.ro-store0"}, "/mnt-root/nix/ro-store0", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.ro-store0"}, "/mnt-root/nix/ro-store0", nil),
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.ro-store1"}, "/mnt-root/nix/ro-store1", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.ro-store1"}, "/mnt-root/nix/ro-store1", nil),
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.ro-store2"}, "/mnt-root/nix/ro-store2", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.ro-store2"}, "/mnt-root/nix/ro-store2", nil),
-			{"evalSymlinks", expectArgs{"/mnt-root/nix/.ro-store3"}, "/mnt-root/nix/ro-store3", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/mnt-root/nix/.ro-store3"}, "/mnt-root/nix/ro-store3", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot/nix/store", os.FileMode(0700)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/nix/store", os.FileMode(0700)}, nil, nil),
-			{"mount", expectArgs{"overlay", "/sysroot/nix/store", "overlay", uintptr(0), "" +
+			call("mount", stub.ExpectArgs{"overlay", "/sysroot/nix/store", "overlay", uintptr(0), "" +
 				"upperdir=/host/mnt-root/nix/.rw-store/.upper," +
 				"workdir=/host/mnt-root/nix/.rw-store/.work," +
 				"lowerdir=" +
@@ -236,13 +264,13 @@ func TestMountOverlayOp(t *testing.T) {
 				"/host/mnt-root/nix/ro-store1:" +
 				"/host/mnt-root/nix/ro-store2:" +
 				"/host/mnt-root/nix/ro-store3," +
-				"userxattr"}, nil, nil},
+				"userxattr"}, nil, nil),
 		}, nil},
 	})
 
 	t.Run("unreachable", func(t *testing.T) {
 		t.Run("nil Upper non-nil Work not ephemeral", func(t *testing.T) {
-			wantErr := msg.WrapErr(fs.ErrClosed, "impossible overlay state reached")
+			wantErr := OpStateError("overlay")
 			if err := (&MountOverlayOp{
 				Work: MustAbs("/"),
 			}).early(nil, nil); !errors.Is(err, wantErr) {

container/initplace.go

@@ -39,13 +39,11 @@ func (t *TmpfileOp) early(*setupState, syscallDispatcher) error { return nil }
 func (t *TmpfileOp) apply(state *setupState, k syscallDispatcher) error {
 	var tmpPath string
 	if f, err := k.createTemp(FHSRoot, intermediatePatternTmpfile); err != nil {
-		return wrapErrSelf(err)
+		return err
 	} else if _, err = f.Write(t.Data); err != nil {
-		return wrapErrSuffix(err,
+		return err
-			"cannot write to intermediate file:")
 	} else if err = f.Close(); err != nil {
-		return wrapErrSuffix(err,
+		return err
-			"cannot close intermediate file:")
 	} else {
 		tmpPath = f.Name()
 	}
@@ -57,11 +55,10 @@ func (t *TmpfileOp) apply(state *setupState, k syscallDispatcher) error {
 		tmpPath,
 		target,
 		syscall.MS_RDONLY|syscall.MS_NODEV,
-		false,
 	); err != nil {
 		return err
 	} else if err = k.remove(tmpPath); err != nil {
-		return wrapErrSelf(err)
+		return err
 	}
 	return nil
 }
@@ -72,7 +69,7 @@ func (t *TmpfileOp) Is(op Op) bool {
 		t.Path.Is(vt.Path) &&
 		string(t.Data) == string(vt.Data)
 }
-func (*TmpfileOp) prefix() string { return "placing" }
+func (*TmpfileOp) prefix() (string, bool) { return "placing", true }
 func (t *TmpfileOp) String() string {
 	return fmt.Sprintf("tmpfile %q (%d bytes)", t.Path, len(t.Data))
 }

container/initplace_test.go

@@ -3,6 +3,8 @@ package container
 import (
 	"os"
 	"testing"
+
+	"hakurei.app/container/stub"
 )
 
 func TestTmpfileOp(t *testing.T) {
@@ -16,59 +18,59 @@ func TestTmpfileOp(t *testing.T) {
 		{"createTemp", &Params{ParentPerm: 0700}, &TmpfileOp{
 			Path: samplePath,
 			Data: sampleData,
-		}, nil, nil, []kexpect{
+		}, nil, nil, []stub.Call{
-			{"createTemp", expectArgs{"/", "tmp.*"}, newCheckedFile(t, "tmp.32768", sampleDataString, nil), errUnique},
+			call("createTemp", stub.ExpectArgs{"/", "tmp.*"}, newCheckedFile(t, "tmp.32768", sampleDataString, nil), stub.UniqueError(5)),
-		}, wrapErrSelf(errUnique)},
+		}, stub.UniqueError(5)},
 
 		{"Write", &Params{ParentPerm: 0700}, &TmpfileOp{
 			Path: samplePath,
 			Data: sampleData,
-		}, nil, nil, []kexpect{
+		}, nil, nil, []stub.Call{
-			{"createTemp", expectArgs{"/", "tmp.*"}, writeErrOsFile{errUnique}, nil},
+			call("createTemp", stub.ExpectArgs{"/", "tmp.*"}, writeErrOsFile{stub.UniqueError(4)}, nil),
-		}, wrapErrSuffix(errUnique, "cannot write to intermediate file:")},
+		}, stub.UniqueError(4)},
 
 		{"Close", &Params{ParentPerm: 0700}, &TmpfileOp{
 			Path: samplePath,
 			Data: sampleData,
-		}, nil, nil, []kexpect{
+		}, nil, nil, []stub.Call{
-			{"createTemp", expectArgs{"/", "tmp.*"}, newCheckedFile(t, "tmp.32768", sampleDataString, errUnique), nil},
+			call("createTemp", stub.ExpectArgs{"/", "tmp.*"}, newCheckedFile(t, "tmp.32768", sampleDataString, stub.UniqueError(3)), nil),
-		}, wrapErrSuffix(errUnique, "cannot close intermediate file:")},
+		}, stub.UniqueError(3)},
 
 		{"ensureFile", &Params{ParentPerm: 0700}, &TmpfileOp{
 			Path: samplePath,
 			Data: sampleData,
-		}, nil, nil, []kexpect{
+		}, nil, nil, []stub.Call{
-			{"createTemp", expectArgs{"/", "tmp.*"}, newCheckedFile(t, "tmp.32768", sampleDataString, nil), nil},
+			call("createTemp", stub.ExpectArgs{"/", "tmp.*"}, newCheckedFile(t, "tmp.32768", sampleDataString, nil), nil),
-			{"ensureFile", expectArgs{"/sysroot/etc/passwd", os.FileMode(0444), os.FileMode(0700)}, nil, errUnique},
+			call("ensureFile", stub.ExpectArgs{"/sysroot/etc/passwd", os.FileMode(0444), os.FileMode(0700)}, nil, stub.UniqueError(2)),
-		}, errUnique},
+		}, stub.UniqueError(2)},
 
 		{"bindMount", &Params{ParentPerm: 0700}, &TmpfileOp{
 			Path: samplePath,
 			Data: sampleData,
-		}, nil, nil, []kexpect{
+		}, nil, nil, []stub.Call{
-			{"createTemp", expectArgs{"/", "tmp.*"}, newCheckedFile(t, "tmp.32768", sampleDataString, nil), nil},
+			call("createTemp", stub.ExpectArgs{"/", "tmp.*"}, newCheckedFile(t, "tmp.32768", sampleDataString, nil), nil),
-			{"ensureFile", expectArgs{"/sysroot/etc/passwd", os.FileMode(0444), os.FileMode(0700)}, nil, nil},
+			call("ensureFile", stub.ExpectArgs{"/sysroot/etc/passwd", os.FileMode(0444), os.FileMode(0700)}, nil, nil),
-			{"bindMount", expectArgs{"tmp.32768", "/sysroot/etc/passwd", uintptr(0x5), false}, nil, errUnique},
+			call("bindMount", stub.ExpectArgs{"tmp.32768", "/sysroot/etc/passwd", uintptr(0x5), false}, nil, stub.UniqueError(1)),
-		}, errUnique},
+		}, stub.UniqueError(1)},
 
 		{"remove", &Params{ParentPerm: 0700}, &TmpfileOp{
 			Path: samplePath,
 			Data: sampleData,
-		}, nil, nil, []kexpect{
+		}, nil, nil, []stub.Call{
-			{"createTemp", expectArgs{"/", "tmp.*"}, newCheckedFile(t, "tmp.32768", sampleDataString, nil), nil},
+			call("createTemp", stub.ExpectArgs{"/", "tmp.*"}, newCheckedFile(t, "tmp.32768", sampleDataString, nil), nil),
-			{"ensureFile", expectArgs{"/sysroot/etc/passwd", os.FileMode(0444), os.FileMode(0700)}, nil, nil},
+			call("ensureFile", stub.ExpectArgs{"/sysroot/etc/passwd", os.FileMode(0444), os.FileMode(0700)}, nil, nil),
-			{"bindMount", expectArgs{"tmp.32768", "/sysroot/etc/passwd", uintptr(0x5), false}, nil, nil},
+			call("bindMount", stub.ExpectArgs{"tmp.32768", "/sysroot/etc/passwd", uintptr(0x5), false}, nil, nil),
-			{"remove", expectArgs{"tmp.32768"}, nil, errUnique},
+			call("remove", stub.ExpectArgs{"tmp.32768"}, nil, stub.UniqueError(0)),
-		}, wrapErrSelf(errUnique)},
+		}, stub.UniqueError(0)},
 
 		{"success", &Params{ParentPerm: 0700}, &TmpfileOp{
 			Path: samplePath,
 			Data: sampleData,
-		}, nil, nil, []kexpect{
+		}, nil, nil, []stub.Call{
-			{"createTemp", expectArgs{"/", "tmp.*"}, newCheckedFile(t, "tmp.32768", sampleDataString, nil), nil},
+			call("createTemp", stub.ExpectArgs{"/", "tmp.*"}, newCheckedFile(t, "tmp.32768", sampleDataString, nil), nil),
-			{"ensureFile", expectArgs{"/sysroot/etc/passwd", os.FileMode(0444), os.FileMode(0700)}, nil, nil},
+			call("ensureFile", stub.ExpectArgs{"/sysroot/etc/passwd", os.FileMode(0444), os.FileMode(0700)}, nil, nil),
-			{"bindMount", expectArgs{"tmp.32768", "/sysroot/etc/passwd", uintptr(0x5), false}, nil, nil},
+			call("bindMount", stub.ExpectArgs{"tmp.32768", "/sysroot/etc/passwd", uintptr(0x5), false}, nil, nil),
-			{"remove", expectArgs{"tmp.32768"}, nil, nil},
+			call("remove", stub.ExpectArgs{"tmp.32768"}, nil, nil),
 		}, nil},
 	})
 

container/initproc.go

@@ -22,10 +22,9 @@ func (p *MountProcOp) early(*setupState, syscallDispatcher) error { return nil }
 func (p *MountProcOp) apply(state *setupState, k syscallDispatcher) error {
 	target := toSysroot(p.Target.String())
 	if err := k.mkdirAll(target, state.ParentPerm); err != nil {
-		return wrapErrSelf(err)
+		return err
 	}
-	return wrapErrSuffix(k.mount(SourceProc, target, FstypeProc, MS_NOSUID|MS_NOEXEC|MS_NODEV, zeroString),
+	return k.mount(SourceProc, target, FstypeProc, MS_NOSUID|MS_NOEXEC|MS_NODEV, zeroString)
-		fmt.Sprintf("cannot mount proc on %q:", p.Target.String()))
 }
 
 func (p *MountProcOp) Is(op Op) bool {
@@ -33,5 +32,5 @@ func (p *MountProcOp) Is(op Op) bool {
 	return ok && p.Valid() && vp.Valid() &&
 		p.Target.Is(vp.Target)
 }
-func (*MountProcOp) prefix() string   { return "mounting" }
+func (*MountProcOp) prefix() (string, bool) { return "mounting", true }
-func (p *MountProcOp) String() string { return fmt.Sprintf("proc on %q", p.Target) }
+func (p *MountProcOp) String() string       { return fmt.Sprintf("proc on %q", p.Target) }

container/initproc_test.go

@@ -3,6 +3,8 @@ package container
 import (
 	"os"
 	"testing"
+
+	"hakurei.app/container/stub"
 )
 
 func TestMountProcOp(t *testing.T) {
@@ -10,16 +12,16 @@ func TestMountProcOp(t *testing.T) {
 		{"mkdir", &Params{ParentPerm: 0755},
 			&MountProcOp{
 				Target: MustAbs("/proc/"),
-			}, nil, nil, []kexpect{
+			}, nil, nil, []stub.Call{
-				{"mkdirAll", expectArgs{"/sysroot/proc", os.FileMode(0755)}, nil, errUnique},
+				call("mkdirAll", stub.ExpectArgs{"/sysroot/proc", os.FileMode(0755)}, nil, stub.UniqueError(0)),
-			}, wrapErrSelf(errUnique)},
+			}, stub.UniqueError(0)},
 
 		{"success", &Params{ParentPerm: 0700},
 			&MountProcOp{
 				Target: MustAbs("/proc/"),
-			}, nil, nil, []kexpect{
+			}, nil, nil, []stub.Call{
-				{"mkdirAll", expectArgs{"/sysroot/proc", os.FileMode(0700)}, nil, nil},
+				call("mkdirAll", stub.ExpectArgs{"/sysroot/proc", os.FileMode(0700)}, nil, nil),
-				{"mount", expectArgs{"proc", "/sysroot/proc", "proc", uintptr(0xe), ""}, nil, nil},
+				call("mount", stub.ExpectArgs{"proc", "/sysroot/proc", "proc", uintptr(0xe), ""}, nil, nil),
 			}, nil},
 	})
 

container/initremount.go

@@ -22,8 +22,7 @@ type RemountOp struct {
 func (r *RemountOp) Valid() bool                              { return r != nil && r.Target != nil }
 func (*RemountOp) early(*setupState, syscallDispatcher) error { return nil }
 func (r *RemountOp) apply(_ *setupState, k syscallDispatcher) error {
-	return wrapErrSuffix(k.remount(toSysroot(r.Target.String()), r.Flags),
+	return k.remount(toSysroot(r.Target.String()), r.Flags)
-		fmt.Sprintf("cannot remount %q:", r.Target))
 }
 
 func (r *RemountOp) Is(op Op) bool {
@@ -32,5 +31,5 @@ func (r *RemountOp) Is(op Op) bool {
 		r.Target.Is(vr.Target) &&
 		r.Flags == vr.Flags
 }
-func (*RemountOp) prefix() string   { return "remounting" }
+func (*RemountOp) prefix() (string, bool) { return "remounting", true }
-func (r *RemountOp) String() string { return fmt.Sprintf("%q flags %#x", r.Target, r.Flags) }
+func (r *RemountOp) String() string       { return fmt.Sprintf("%q flags %#x", r.Target, r.Flags) }

container/initremount_test.go

@@ -3,6 +3,8 @@ package container
 import (
 	"syscall"
 	"testing"
+
+	"hakurei.app/container/stub"
 )
 
 func TestRemountOp(t *testing.T) {
@@ -10,8 +12,8 @@ func TestRemountOp(t *testing.T) {
 		{"success", new(Params), &RemountOp{
 			Target: MustAbs("/"),
 			Flags:  syscall.MS_RDONLY,
-		}, nil, nil, []kexpect{
+		}, nil, nil, []stub.Call{
-			{"remount", expectArgs{"/sysroot", uintptr(1)}, nil, nil},
+			call("remount", stub.ExpectArgs{"/sysroot", uintptr(1)}, nil, nil),
 		}, nil},
 	})
 

container/initsymlink.go

@@ -3,7 +3,6 @@ package container
 import (
 	"encoding/gob"
 	"fmt"
-	"io/fs"
 	"path"
 )
 
@@ -30,10 +29,10 @@ func (l *SymlinkOp) Valid() bool { return l != nil && l.Target != nil && l.LinkN
 func (l *SymlinkOp) early(_ *setupState, k syscallDispatcher) error {
 	if l.Dereference {
 		if !isAbs(l.LinkName) {
-			return msg.WrapErr(fs.ErrInvalid, fmt.Sprintf("path %q is not absolute", l.LinkName))
+			return &AbsoluteError{l.LinkName}
 		}
 		if name, err := k.readlink(l.LinkName); err != nil {
-			return wrapErrSelf(err)
+			return err
 		} else {
 			l.LinkName = name
 		}
@@ -44,9 +43,9 @@ func (l *SymlinkOp) early(_ *setupState, k syscallDispatcher) error {
 func (l *SymlinkOp) apply(state *setupState, k syscallDispatcher) error {
 	target := toSysroot(l.Target.String())
 	if err := k.mkdirAll(path.Dir(target), state.ParentPerm); err != nil {
-		return wrapErrSelf(err)
+		return err
 	}
-	return wrapErrSelf(k.symlink(l.LinkName, target))
+	return k.symlink(l.LinkName, target)
 }
 
 func (l *SymlinkOp) Is(op Op) bool {
@@ -56,7 +55,7 @@ func (l *SymlinkOp) Is(op Op) bool {
 		l.LinkName == vl.LinkName &&
 		l.Dereference == vl.Dereference
 }
-func (*SymlinkOp) prefix() string { return "creating" }
+func (*SymlinkOp) prefix() (string, bool) { return "creating", true }
 func (l *SymlinkOp) String() string {
 	return fmt.Sprintf("symlink on %q linkname %q", l.Target, l.LinkName)
 }

container/initsymlink_test.go

@@ -1,9 +1,10 @@
 package container
 
 import (
-	"io/fs"
 	"os"
 	"testing"
+
+	"hakurei.app/container/stub"
 )
 
 func TestSymlinkOp(t *testing.T) {
@@ -11,41 +12,41 @@ func TestSymlinkOp(t *testing.T) {
 		{"mkdir", &Params{ParentPerm: 0700}, &SymlinkOp{
 			Target:   MustAbs("/etc/nixos"),
 			LinkName: "/etc/static/nixos",
-		}, nil, nil, []kexpect{
+		}, nil, nil, []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot/etc", os.FileMode(0700)}, nil, errUnique},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/etc", os.FileMode(0700)}, nil, stub.UniqueError(1)),
-		}, wrapErrSelf(errUnique)},
+		}, stub.UniqueError(1)},
 
 		{"abs", &Params{ParentPerm: 0755}, &SymlinkOp{
 			Target:      MustAbs("/etc/mtab"),
 			LinkName:    "etc/mtab",
 			Dereference: true,
-		}, nil, msg.WrapErr(fs.ErrInvalid, `path "etc/mtab" is not absolute`), nil, nil},
+		}, nil, &AbsoluteError{"etc/mtab"}, nil, nil},
 
 		{"readlink", &Params{ParentPerm: 0755}, &SymlinkOp{
 			Target:      MustAbs("/etc/mtab"),
 			LinkName:    "/etc/mtab",
 			Dereference: true,
-		}, []kexpect{
+		}, []stub.Call{
-			{"readlink", expectArgs{"/etc/mtab"}, "/proc/mounts", errUnique},
+			call("readlink", stub.ExpectArgs{"/etc/mtab"}, "/proc/mounts", stub.UniqueError(0)),
-		}, wrapErrSelf(errUnique), nil, nil},
+		}, stub.UniqueError(0), nil, nil},
 
 		{"success noderef", &Params{ParentPerm: 0700}, &SymlinkOp{
 			Target:   MustAbs("/etc/nixos"),
 			LinkName: "/etc/static/nixos",
-		}, nil, nil, []kexpect{
+		}, nil, nil, []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot/etc", os.FileMode(0700)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/etc", os.FileMode(0700)}, nil, nil),
-			{"symlink", expectArgs{"/etc/static/nixos", "/sysroot/etc/nixos"}, nil, nil},
+			call("symlink", stub.ExpectArgs{"/etc/static/nixos", "/sysroot/etc/nixos"}, nil, nil),
 		}, nil},
 
 		{"success", &Params{ParentPerm: 0755}, &SymlinkOp{
 			Target:      MustAbs("/etc/mtab"),
 			LinkName:    "/etc/mtab",
 			Dereference: true,
-		}, []kexpect{
+		}, []stub.Call{
-			{"readlink", expectArgs{"/etc/mtab"}, "/proc/mounts", nil},
+			call("readlink", stub.ExpectArgs{"/etc/mtab"}, "/proc/mounts", nil),
-		}, nil, []kexpect{
+		}, nil, []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot/etc", os.FileMode(0755)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/etc", os.FileMode(0755)}, nil, nil),
-			{"symlink", expectArgs{"/proc/mounts", "/sysroot/etc/mtab"}, nil, nil},
+			call("symlink", stub.ExpectArgs{"/proc/mounts", "/sysroot/etc/mtab"}, nil, nil),
 		}, nil},
 	})
 

container/inittmpfs.go

@@ -3,14 +3,20 @@ package container
 import (
 	"encoding/gob"
 	"fmt"
-	"io/fs"
 	"math"
 	"os"
+	"strconv"
 	. "syscall"
 )
 
 func init() { gob.Register(new(MountTmpfsOp)) }
 
+type TmpfsSizeError int
+
+func (e TmpfsSizeError) Error() string {
+	return "tmpfs size " + strconv.Itoa(int(e)) + " out of bounds"
+}
+
 // Tmpfs appends an [Op] that mounts tmpfs on container path [MountTmpfsOp.Path].
 func (f *Ops) Tmpfs(target *Absolute, size int, perm os.FileMode) *Ops {
 	*f = append(*f, &MountTmpfsOp{SourceTmpfsEphemeral, target, MS_NOSUID | MS_NODEV, size, perm})
@@ -36,7 +42,7 @@ func (t *MountTmpfsOp) Valid() bool                                { return t !=
 func (t *MountTmpfsOp) early(*setupState, syscallDispatcher) error { return nil }
 func (t *MountTmpfsOp) apply(_ *setupState, k syscallDispatcher) error {
 	if t.Size < 0 || t.Size > math.MaxUint>>1 {
-		return msg.WrapErr(fs.ErrInvalid, fmt.Sprintf("size %d out of bounds", t.Size))
+		return TmpfsSizeError(t.Size)
 	}
 	return k.mountTmpfs(t.FSName, toSysroot(t.Path.String()), t.Flags, t.Size, t.Perm)
 }
@@ -50,5 +56,5 @@ func (t *MountTmpfsOp) Is(op Op) bool {
 		t.Size == vt.Size &&
 		t.Perm == vt.Perm
 }
-func (*MountTmpfsOp) prefix() string   { return "mounting" }
+func (*MountTmpfsOp) prefix() (string, bool) { return "mounting", true }
-func (t *MountTmpfsOp) String() string { return fmt.Sprintf("tmpfs on %q size %d", t.Path, t.Size) }
+func (t *MountTmpfsOp) String() string       { return fmt.Sprintf("tmpfs on %q size %d", t.Path, t.Size) }

container/inittmpfs_test.go

@@ -1,31 +1,40 @@
 package container
 
 import (
-	"io/fs"
 	"os"
 	"syscall"
 	"testing"
+
+	"hakurei.app/container/stub"
 )
 
 func TestMountTmpfsOp(t *testing.T) {
+	t.Run("size error", func(t *testing.T) {
+		tmpfsSizeError := TmpfsSizeError(-1)
+		want := "tmpfs size -1 out of bounds"
+		if got := tmpfsSizeError.Error(); got != want {
+			t.Errorf("Error: %q, want %q", got, want)
+		}
+	})
+
 	checkOpBehaviour(t, []opBehaviourTestCase{
 		{"size oob", new(Params), &MountTmpfsOp{
 			Size: -1,
-		}, nil, nil, nil, msg.WrapErr(fs.ErrInvalid, "size -1 out of bounds")},
+		}, nil, nil, nil, TmpfsSizeError(-1)},
 
 		{"success", new(Params), &MountTmpfsOp{
 			FSName: "ephemeral",
 			Path:   MustAbs("/run/user/1000/"),
 			Size:   1 << 10,
 			Perm:   0700,
-		}, nil, nil, []kexpect{
+		}, nil, nil, []stub.Call{
-			{"mountTmpfs", expectArgs{
+			call("mountTmpfs", stub.ExpectArgs{
 				"ephemeral",              // fsname
 				"/sysroot/run/user/1000", // target
 				uintptr(0),               // flags
 				0x400,                    // size
 				os.FileMode(0700),        // perm
-			}, nil, nil},
+			}, nil, nil),
 		}, nil},
 	})
 

container/mount.go

@@ -43,6 +43,8 @@ const (
 	// Note that any source value is allowed when fstype is [FstypeOverlay].
 	SourceOverlay = "overlay"
 
+	// SourceTmpfs is used when mounting tmpfs.
+	SourceTmpfs = "tmpfs"
 	// SourceTmpfsRootfs is used when mounting the tmpfs instance backing the intermediate root.
 	SourceTmpfsRootfs = "rootfs"
 	// SourceTmpfsDevtmpfs is used when mounting tmpfs representing a subset of host devtmpfs.
@@ -94,18 +96,11 @@ const (
 )
 
 // bindMount mounts source on target and recursively applies flags if MS_REC is set.
-func (p *procPaths) bindMount(source, target string, flags uintptr, eq bool) error {
+func (p *procPaths) bindMount(source, target string, flags uintptr) error {
 	// syscallDispatcher.bindMount and procPaths.remount must not be called from this function
 
-	if eq {
-		p.k.verbosef("resolved %q flags %#x", target, flags)
-	} else {
-		p.k.verbosef("resolved %q on %q flags %#x", source, target, flags)
-	}
-
 	if err := p.k.mount(source, target, FstypeNULL, MS_SILENT|MS_BIND|flags&MS_REC, zeroString); err != nil {
-		return wrapErrSuffix(err,
+		return err
-			fmt.Sprintf("cannot mount %q on %q:", source, target))
 	}
 
 	return p.k.remount(target, flags)
@@ -117,7 +112,7 @@ func (p *procPaths) remount(target string, flags uintptr) error {
 
 	var targetFinal string
 	if v, err := p.k.evalSymlinks(target); err != nil {
-		return wrapErrSelf(err)
+		return err
 	} else {
 		targetFinal = v
 		if targetFinal != target {
@@ -133,14 +128,12 @@ func (p *procPaths) remount(target string, flags uintptr) error {
 			destFd, err = p.k.open(targetFinal, O_PATH|O_CLOEXEC, 0)
 			return
 		}); err != nil {
-			return wrapErrSuffix(err,
+			return &os.PathError{Op: "open", Path: targetFinal, Err: err}
-				fmt.Sprintf("cannot open %q:", targetFinal))
 		}
 		if v, err := p.k.readlink(p.fd(destFd)); err != nil {
-			return wrapErrSelf(err)
+			return err
 		} else if err = p.k.close(destFd); err != nil {
-			return wrapErrSuffix(err,
+			return &os.PathError{Op: "close", Path: targetFinal, Err: err}
-				fmt.Sprintf("cannot close %q:", targetFinal))
 		} else {
 			targetKFinal = v
 		}
@@ -150,17 +143,11 @@ func (p *procPaths) remount(target string, flags uintptr) error {
 	return p.mountinfo(func(d *vfs.MountInfoDecoder) error {
 		n, err := d.Unfold(targetKFinal)
 		if err != nil {
-			if errors.Is(err, ESTALE) {
+			return err
-				return msg.WrapErr(err,
-					fmt.Sprintf("mount point %q never appeared in mountinfo", targetKFinal))
-			}
-			return wrapErrSuffix(err,
-				"cannot unfold mount hierarchy:")
 		}
 
 		if err = remountWithFlags(p.k, n, mf); err != nil {
-			return wrapErrSuffix(err,
+			return err
-				fmt.Sprintf("cannot remount %q:", n.Clean))
 		}
 		if flags&MS_REC == 0 {
 			return nil
@@ -172,11 +159,8 @@ func (p *procPaths) remount(target string, flags uintptr) error {
 				continue
 			}
 
-			err = remountWithFlags(p.k, cur, mf)
+			if err = remountWithFlags(p.k, cur, mf); err != nil && !errors.Is(err, EACCES) {
-
+				return err
-			if err != nil && !errors.Is(err, EACCES) {
-				return wrapErrSuffix(err,
-					fmt.Sprintf("cannot propagate flags to %q:", cur.Clean))
 			}
 		}
 
@@ -205,15 +189,13 @@ func mountTmpfs(k syscallDispatcher, fsname, target string, flags uintptr, size
 	// syscallDispatcher.mountTmpfs must not be called from this function
 
 	if err := k.mkdirAll(target, parentPerm(perm)); err != nil {
-		return wrapErrSelf(err)
+		return err
 	}
 	opt := fmt.Sprintf("mode=%#o", perm)
 	if size > 0 {
 		opt += fmt.Sprintf(",size=%d", size)
 	}
-	return wrapErrSuffix(
+	return k.mount(fsname, target, FstypeTmpfs, flags, opt)
-		k.mount(fsname, target, FstypeTmpfs, flags, opt),
-		fmt.Sprintf("cannot mount tmpfs on %q:", target))
 }
 
 func parentPerm(perm os.FileMode) os.FileMode {

container/mount_test.go

@@ -5,32 +5,30 @@ import (
 	"syscall"
 	"testing"
 
+	"hakurei.app/container/stub"
 	"hakurei.app/container/vfs"
 )
 
 func TestBindMount(t *testing.T) {
 	checkSimple(t, "bindMount", []simpleTestCase{
 		{"mount", func(k syscallDispatcher) error {
-			return newProcPaths(k, hostPath).bindMount("/host/nix", "/sysroot/nix", syscall.MS_RDONLY, true)
+			return newProcPaths(k, hostPath).bindMount("/host/nix", "/sysroot/nix", syscall.MS_RDONLY)
-		}, [][]kexpect{{
+		}, stub.Expect{Calls: []stub.Call{
-			{"verbosef", expectArgs{"resolved %q flags %#x", []any{"/sysroot/nix", uintptr(1)}}, nil, nil},
+			call("mount", stub.ExpectArgs{"/host/nix", "/sysroot/nix", "", uintptr(0x9000), ""}, nil, stub.UniqueError(0xbad)),
-			{"mount", expectArgs{"/host/nix", "/sysroot/nix", "", uintptr(0x9000), ""}, nil, errUnique},
+		}}, stub.UniqueError(0xbad)},
-		}}, wrapErrSuffix(errUnique, `cannot mount "/host/nix" on "/sysroot/nix":`)},
 
 		{"success ne", func(k syscallDispatcher) error {
-			return newProcPaths(k, hostPath).bindMount("/host/nix", "/sysroot/.host-nix", syscall.MS_RDONLY, false)
+			return newProcPaths(k, hostPath).bindMount("/host/nix", "/sysroot/.host-nix", syscall.MS_RDONLY)
-		}, [][]kexpect{{
+		}, stub.Expect{Calls: []stub.Call{
-			{"verbosef", expectArgs{"resolved %q on %q flags %#x", []any{"/host/nix", "/sysroot/.host-nix", uintptr(1)}}, nil, nil},
+			call("mount", stub.ExpectArgs{"/host/nix", "/sysroot/.host-nix", "", uintptr(0x9000), ""}, nil, nil),
-			{"mount", expectArgs{"/host/nix", "/sysroot/.host-nix", "", uintptr(0x9000), ""}, nil, nil},
+			call("remount", stub.ExpectArgs{"/sysroot/.host-nix", uintptr(1)}, nil, nil),
-			{"remount", expectArgs{"/sysroot/.host-nix", uintptr(1)}, nil, nil},
 		}}, nil},
 
 		{"success", func(k syscallDispatcher) error {
-			return newProcPaths(k, hostPath).bindMount("/host/nix", "/sysroot/nix", syscall.MS_RDONLY, true)
+			return newProcPaths(k, hostPath).bindMount("/host/nix", "/sysroot/nix", syscall.MS_RDONLY)
-		}, [][]kexpect{{
+		}, stub.Expect{Calls: []stub.Call{
-			{"verbosef", expectArgs{"resolved %q flags %#x", []any{"/sysroot/nix", uintptr(1)}}, nil, nil},
+			call("mount", stub.ExpectArgs{"/host/nix", "/sysroot/nix", "", uintptr(0x9000), ""}, nil, nil),
-			{"mount", expectArgs{"/host/nix", "/sysroot/nix", "", uintptr(0x9000), ""}, nil, nil},
+			call("remount", stub.ExpectArgs{"/sysroot/nix", uintptr(1)}, nil, nil),
-			{"remount", expectArgs{"/sysroot/nix", uintptr(1)}, nil, nil},
 		}}, nil},
 	})
 }
@@ -81,138 +79,138 @@ func TestRemount(t *testing.T) {
 	checkSimple(t, "remount", []simpleTestCase{
 		{"evalSymlinks", func(k syscallDispatcher) error {
 			return newProcPaths(k, hostPath).remount("/sysroot/nix", syscall.MS_REC|syscall.MS_RDONLY|syscall.MS_NODEV)
-		}, [][]kexpect{{
+		}, stub.Expect{Calls: []stub.Call{
-			{"evalSymlinks", expectArgs{"/sysroot/nix"}, "/sysroot/nix", errUnique},
+			call("evalSymlinks", stub.ExpectArgs{"/sysroot/nix"}, "/sysroot/nix", stub.UniqueError(6)),
-		}}, wrapErrSelf(errUnique)},
+		}}, stub.UniqueError(6)},
 
 		{"open", func(k syscallDispatcher) error {
 			return newProcPaths(k, hostPath).remount("/sysroot/nix", syscall.MS_REC|syscall.MS_RDONLY|syscall.MS_NODEV)
-		}, [][]kexpect{{
+		}, stub.Expect{Calls: []stub.Call{
-			{"evalSymlinks", expectArgs{"/sysroot/nix"}, "/sysroot/nix", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/sysroot/nix"}, "/sysroot/nix", nil),
-			{"open", expectArgs{"/sysroot/nix", 0x280000, uint32(0)}, 0xdeadbeef, errUnique},
+			call("open", stub.ExpectArgs{"/sysroot/nix", 0x280000, uint32(0)}, 0xdeadbeef, stub.UniqueError(5)),
-		}}, wrapErrSuffix(errUnique, `cannot open "/sysroot/nix":`)},
+		}}, &os.PathError{Op: "open", Path: "/sysroot/nix", Err: stub.UniqueError(5)}},
 
 		{"readlink", func(k syscallDispatcher) error {
 			return newProcPaths(k, hostPath).remount("/sysroot/nix", syscall.MS_REC|syscall.MS_RDONLY|syscall.MS_NODEV)
-		}, [][]kexpect{{
+		}, stub.Expect{Calls: []stub.Call{
-			{"evalSymlinks", expectArgs{"/sysroot/nix"}, "/sysroot/nix", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/sysroot/nix"}, "/sysroot/nix", nil),
-			{"open", expectArgs{"/sysroot/nix", 0x280000, uint32(0)}, 0xdeadbeef, nil},
+			call("open", stub.ExpectArgs{"/sysroot/nix", 0x280000, uint32(0)}, 0xdeadbeef, nil),
-			{"readlink", expectArgs{"/host/proc/self/fd/3735928559"}, "/sysroot/nix", errUnique},
+			call("readlink", stub.ExpectArgs{"/host/proc/self/fd/3735928559"}, "/sysroot/nix", stub.UniqueError(4)),
-		}}, wrapErrSelf(errUnique)},
+		}}, stub.UniqueError(4)},
 
 		{"close", func(k syscallDispatcher) error {
 			return newProcPaths(k, hostPath).remount("/sysroot/nix", syscall.MS_REC|syscall.MS_RDONLY|syscall.MS_NODEV)
-		}, [][]kexpect{{
+		}, stub.Expect{Calls: []stub.Call{
-			{"evalSymlinks", expectArgs{"/sysroot/nix"}, "/sysroot/nix", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/sysroot/nix"}, "/sysroot/nix", nil),
-			{"open", expectArgs{"/sysroot/nix", 0x280000, uint32(0)}, 0xdeadbeef, nil},
+			call("open", stub.ExpectArgs{"/sysroot/nix", 0x280000, uint32(0)}, 0xdeadbeef, nil),
-			{"readlink", expectArgs{"/host/proc/self/fd/3735928559"}, "/sysroot/nix", nil},
+			call("readlink", stub.ExpectArgs{"/host/proc/self/fd/3735928559"}, "/sysroot/nix", nil),
-			{"close", expectArgs{0xdeadbeef}, nil, errUnique},
+			call("close", stub.ExpectArgs{0xdeadbeef}, nil, stub.UniqueError(3)),
-		}}, wrapErrSuffix(errUnique, `cannot close "/sysroot/nix":`)},
+		}}, &os.PathError{Op: "close", Path: "/sysroot/nix", Err: stub.UniqueError(3)}},
 
-		{"mountinfo stale", func(k syscallDispatcher) error {
+		{"mountinfo no match", func(k syscallDispatcher) error {
 			return newProcPaths(k, hostPath).remount("/sysroot/nix", syscall.MS_REC|syscall.MS_RDONLY|syscall.MS_NODEV)
-		}, [][]kexpect{{
+		}, stub.Expect{Calls: []stub.Call{
-			{"evalSymlinks", expectArgs{"/sysroot/nix"}, "/sysroot/.hakurei", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/sysroot/nix"}, "/sysroot/.hakurei", nil),
-			{"verbosef", expectArgs{"target resolves to %q", []any{"/sysroot/.hakurei"}}, nil, nil},
+			call("verbosef", stub.ExpectArgs{"target resolves to %q", []any{"/sysroot/.hakurei"}}, nil, nil),
-			{"open", expectArgs{"/sysroot/.hakurei", 0x280000, uint32(0)}, 0xdeadbeef, nil},
+			call("open", stub.ExpectArgs{"/sysroot/.hakurei", 0x280000, uint32(0)}, 0xdeadbeef, nil),
-			{"readlink", expectArgs{"/host/proc/self/fd/3735928559"}, "/sysroot/.hakurei", nil},
+			call("readlink", stub.ExpectArgs{"/host/proc/self/fd/3735928559"}, "/sysroot/.hakurei", nil),
-			{"close", expectArgs{0xdeadbeef}, nil, nil},
+			call("close", stub.ExpectArgs{0xdeadbeef}, nil, nil),
-			{"openNew", expectArgs{"/host/proc/self/mountinfo"}, newConstFile(sampleMountinfoNix), nil},
+			call("openNew", stub.ExpectArgs{"/host/proc/self/mountinfo"}, newConstFile(sampleMountinfoNix), nil),
-		}}, msg.WrapErr(syscall.ESTALE, `mount point "/sysroot/.hakurei" never appeared in mountinfo`)},
+		}}, &vfs.DecoderError{Op: "unfold", Line: -1, Err: vfs.UnfoldTargetError("/sysroot/.hakurei")}},
 
 		{"mountinfo", func(k syscallDispatcher) error {
 			return newProcPaths(k, hostPath).remount("/sysroot/nix", syscall.MS_REC|syscall.MS_RDONLY|syscall.MS_NODEV)
-		}, [][]kexpect{{
+		}, stub.Expect{Calls: []stub.Call{
-			{"evalSymlinks", expectArgs{"/sysroot/nix"}, "/sysroot/nix", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/sysroot/nix"}, "/sysroot/nix", nil),
-			{"open", expectArgs{"/sysroot/nix", 0x280000, uint32(0)}, 0xdeadbeef, nil},
+			call("open", stub.ExpectArgs{"/sysroot/nix", 0x280000, uint32(0)}, 0xdeadbeef, nil),
-			{"readlink", expectArgs{"/host/proc/self/fd/3735928559"}, "/sysroot/nix", nil},
+			call("readlink", stub.ExpectArgs{"/host/proc/self/fd/3735928559"}, "/sysroot/nix", nil),
-			{"close", expectArgs{0xdeadbeef}, nil, nil},
+			call("close", stub.ExpectArgs{0xdeadbeef}, nil, nil),
-			{"openNew", expectArgs{"/host/proc/self/mountinfo"}, newConstFile("\x00"), nil},
+			call("openNew", stub.ExpectArgs{"/host/proc/self/mountinfo"}, newConstFile("\x00"), nil),
-		}}, wrapErrSuffix(vfs.ErrMountInfoFields, `cannot parse mountinfo:`)},
+		}}, &vfs.DecoderError{Op: "parse", Line: 0, Err: vfs.ErrMountInfoFields}},
 
 		{"mount", func(k syscallDispatcher) error {
 			return newProcPaths(k, hostPath).remount("/sysroot/nix", syscall.MS_REC|syscall.MS_RDONLY|syscall.MS_NODEV)
-		}, [][]kexpect{{
+		}, stub.Expect{Calls: []stub.Call{
-			{"evalSymlinks", expectArgs{"/sysroot/nix"}, "/sysroot/nix", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/sysroot/nix"}, "/sysroot/nix", nil),
-			{"open", expectArgs{"/sysroot/nix", 0x280000, uint32(0)}, 0xdeadbeef, nil},
+			call("open", stub.ExpectArgs{"/sysroot/nix", 0x280000, uint32(0)}, 0xdeadbeef, nil),
-			{"readlink", expectArgs{"/host/proc/self/fd/3735928559"}, "/sysroot/nix", nil},
+			call("readlink", stub.ExpectArgs{"/host/proc/self/fd/3735928559"}, "/sysroot/nix", nil),
-			{"close", expectArgs{0xdeadbeef}, nil, nil},
+			call("close", stub.ExpectArgs{0xdeadbeef}, nil, nil),
-			{"openNew", expectArgs{"/host/proc/self/mountinfo"}, newConstFile(sampleMountinfoNix), nil},
+			call("openNew", stub.ExpectArgs{"/host/proc/self/mountinfo"}, newConstFile(sampleMountinfoNix), nil),
-			{"mount", expectArgs{"none", "/sysroot/nix", "", uintptr(0x209027), ""}, nil, errUnique},
+			call("mount", stub.ExpectArgs{"none", "/sysroot/nix", "", uintptr(0x209027), ""}, nil, stub.UniqueError(2)),
-		}}, wrapErrSuffix(errUnique, `cannot remount "/sysroot/nix":`)},
+		}}, stub.UniqueError(2)},
 
 		{"mount propagate", func(k syscallDispatcher) error {
 			return newProcPaths(k, hostPath).remount("/sysroot/nix", syscall.MS_REC|syscall.MS_RDONLY|syscall.MS_NODEV)
-		}, [][]kexpect{{
+		}, stub.Expect{Calls: []stub.Call{
-			{"evalSymlinks", expectArgs{"/sysroot/nix"}, "/sysroot/nix", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/sysroot/nix"}, "/sysroot/nix", nil),
-			{"open", expectArgs{"/sysroot/nix", 0x280000, uint32(0)}, 0xdeadbeef, nil},
+			call("open", stub.ExpectArgs{"/sysroot/nix", 0x280000, uint32(0)}, 0xdeadbeef, nil),
-			{"readlink", expectArgs{"/host/proc/self/fd/3735928559"}, "/sysroot/nix", nil},
+			call("readlink", stub.ExpectArgs{"/host/proc/self/fd/3735928559"}, "/sysroot/nix", nil),
-			{"close", expectArgs{0xdeadbeef}, nil, nil},
+			call("close", stub.ExpectArgs{0xdeadbeef}, nil, nil),
-			{"openNew", expectArgs{"/host/proc/self/mountinfo"}, newConstFile(sampleMountinfoNix), nil},
+			call("openNew", stub.ExpectArgs{"/host/proc/self/mountinfo"}, newConstFile(sampleMountinfoNix), nil),
-			{"mount", expectArgs{"none", "/sysroot/nix", "", uintptr(0x209027), ""}, nil, nil},
+			call("mount", stub.ExpectArgs{"none", "/sysroot/nix", "", uintptr(0x209027), ""}, nil, nil),
-			{"mount", expectArgs{"none", "/sysroot/nix/.ro-store", "", uintptr(0x209027), ""}, nil, errUnique},
+			call("mount", stub.ExpectArgs{"none", "/sysroot/nix/.ro-store", "", uintptr(0x209027), ""}, nil, stub.UniqueError(1)),
-		}}, wrapErrSuffix(errUnique, `cannot propagate flags to "/sysroot/nix/.ro-store":`)},
+		}}, stub.UniqueError(1)},
 
 		{"success toplevel", func(k syscallDispatcher) error {
 			return newProcPaths(k, hostPath).remount("/sysroot/bin", syscall.MS_REC|syscall.MS_RDONLY|syscall.MS_NODEV)
-		}, [][]kexpect{{
+		}, stub.Expect{Calls: []stub.Call{
-			{"evalSymlinks", expectArgs{"/sysroot/bin"}, "/sysroot/bin", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/sysroot/bin"}, "/sysroot/bin", nil),
-			{"open", expectArgs{"/sysroot/bin", 0x280000, uint32(0)}, 0xbabe, nil},
+			call("open", stub.ExpectArgs{"/sysroot/bin", 0x280000, uint32(0)}, 0xbabe, nil),
-			{"readlink", expectArgs{"/host/proc/self/fd/47806"}, "/sysroot/bin", nil},
+			call("readlink", stub.ExpectArgs{"/host/proc/self/fd/47806"}, "/sysroot/bin", nil),
-			{"close", expectArgs{0xbabe}, nil, nil},
+			call("close", stub.ExpectArgs{0xbabe}, nil, nil),
-			{"openNew", expectArgs{"/host/proc/self/mountinfo"}, newConstFile(sampleMountinfoNix), nil},
+			call("openNew", stub.ExpectArgs{"/host/proc/self/mountinfo"}, newConstFile(sampleMountinfoNix), nil),
-			{"mount", expectArgs{"none", "/sysroot/bin", "", uintptr(0x209027), ""}, nil, nil},
+			call("mount", stub.ExpectArgs{"none", "/sysroot/bin", "", uintptr(0x209027), ""}, nil, nil),
 		}}, nil},
 
 		{"success EACCES", func(k syscallDispatcher) error {
 			return newProcPaths(k, hostPath).remount("/sysroot/nix", syscall.MS_REC|syscall.MS_RDONLY|syscall.MS_NODEV)
-		}, [][]kexpect{{
+		}, stub.Expect{Calls: []stub.Call{
-			{"evalSymlinks", expectArgs{"/sysroot/nix"}, "/sysroot/nix", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/sysroot/nix"}, "/sysroot/nix", nil),
-			{"open", expectArgs{"/sysroot/nix", 0x280000, uint32(0)}, 0xdeadbeef, nil},
+			call("open", stub.ExpectArgs{"/sysroot/nix", 0x280000, uint32(0)}, 0xdeadbeef, nil),
-			{"readlink", expectArgs{"/host/proc/self/fd/3735928559"}, "/sysroot/nix", nil},
+			call("readlink", stub.ExpectArgs{"/host/proc/self/fd/3735928559"}, "/sysroot/nix", nil),
-			{"close", expectArgs{0xdeadbeef}, nil, nil},
+			call("close", stub.ExpectArgs{0xdeadbeef}, nil, nil),
-			{"openNew", expectArgs{"/host/proc/self/mountinfo"}, newConstFile(sampleMountinfoNix), nil},
+			call("openNew", stub.ExpectArgs{"/host/proc/self/mountinfo"}, newConstFile(sampleMountinfoNix), nil),
-			{"mount", expectArgs{"none", "/sysroot/nix", "", uintptr(0x209027), ""}, nil, nil},
+			call("mount", stub.ExpectArgs{"none", "/sysroot/nix", "", uintptr(0x209027), ""}, nil, nil),
-			{"mount", expectArgs{"none", "/sysroot/nix/.ro-store", "", uintptr(0x209027), ""}, nil, syscall.EACCES},
+			call("mount", stub.ExpectArgs{"none", "/sysroot/nix/.ro-store", "", uintptr(0x209027), ""}, nil, syscall.EACCES),
-			{"mount", expectArgs{"none", "/sysroot/nix/store", "", uintptr(0x209027), ""}, nil, nil},
+			call("mount", stub.ExpectArgs{"none", "/sysroot/nix/store", "", uintptr(0x209027), ""}, nil, nil),
 		}}, nil},
 
 		{"success no propagate", func(k syscallDispatcher) error {
 			return newProcPaths(k, hostPath).remount("/sysroot/nix", syscall.MS_RDONLY|syscall.MS_NODEV)
-		}, [][]kexpect{{
+		}, stub.Expect{Calls: []stub.Call{
-			{"evalSymlinks", expectArgs{"/sysroot/nix"}, "/sysroot/nix", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/sysroot/nix"}, "/sysroot/nix", nil),
-			{"open", expectArgs{"/sysroot/nix", 0x280000, uint32(0)}, 0xdeadbeef, nil},
+			call("open", stub.ExpectArgs{"/sysroot/nix", 0x280000, uint32(0)}, 0xdeadbeef, nil),
-			{"readlink", expectArgs{"/host/proc/self/fd/3735928559"}, "/sysroot/nix", nil},
+			call("readlink", stub.ExpectArgs{"/host/proc/self/fd/3735928559"}, "/sysroot/nix", nil),
-			{"close", expectArgs{0xdeadbeef}, nil, nil},
+			call("close", stub.ExpectArgs{0xdeadbeef}, nil, nil),
-			{"openNew", expectArgs{"/host/proc/self/mountinfo"}, newConstFile(sampleMountinfoNix), nil},
+			call("openNew", stub.ExpectArgs{"/host/proc/self/mountinfo"}, newConstFile(sampleMountinfoNix), nil),
-			{"mount", expectArgs{"none", "/sysroot/nix", "", uintptr(0x209027), ""}, nil, nil},
+			call("mount", stub.ExpectArgs{"none", "/sysroot/nix", "", uintptr(0x209027), ""}, nil, nil),
 		}}, nil},
 
 		{"success case sensitive", func(k syscallDispatcher) error {
 			return newProcPaths(k, hostPath).remount("/sysroot/nix", syscall.MS_REC|syscall.MS_RDONLY|syscall.MS_NODEV)
-		}, [][]kexpect{{
+		}, stub.Expect{Calls: []stub.Call{
-			{"evalSymlinks", expectArgs{"/sysroot/nix"}, "/sysroot/nix", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/sysroot/nix"}, "/sysroot/nix", nil),
-			{"open", expectArgs{"/sysroot/nix", 0x280000, uint32(0)}, 0xdeadbeef, nil},
+			call("open", stub.ExpectArgs{"/sysroot/nix", 0x280000, uint32(0)}, 0xdeadbeef, nil),
-			{"readlink", expectArgs{"/host/proc/self/fd/3735928559"}, "/sysroot/nix", nil},
+			call("readlink", stub.ExpectArgs{"/host/proc/self/fd/3735928559"}, "/sysroot/nix", nil),
-			{"close", expectArgs{0xdeadbeef}, nil, nil},
+			call("close", stub.ExpectArgs{0xdeadbeef}, nil, nil),
-			{"openNew", expectArgs{"/host/proc/self/mountinfo"}, newConstFile(sampleMountinfoNix), nil},
+			call("openNew", stub.ExpectArgs{"/host/proc/self/mountinfo"}, newConstFile(sampleMountinfoNix), nil),
-			{"mount", expectArgs{"none", "/sysroot/nix", "", uintptr(0x209027), ""}, nil, nil},
+			call("mount", stub.ExpectArgs{"none", "/sysroot/nix", "", uintptr(0x209027), ""}, nil, nil),
-			{"mount", expectArgs{"none", "/sysroot/nix/.ro-store", "", uintptr(0x209027), ""}, nil, nil},
+			call("mount", stub.ExpectArgs{"none", "/sysroot/nix/.ro-store", "", uintptr(0x209027), ""}, nil, nil),
-			{"mount", expectArgs{"none", "/sysroot/nix/store", "", uintptr(0x209027), ""}, nil, nil},
+			call("mount", stub.ExpectArgs{"none", "/sysroot/nix/store", "", uintptr(0x209027), ""}, nil, nil),
 		}}, nil},
 
 		{"success", func(k syscallDispatcher) error {
 			return newProcPaths(k, hostPath).remount("/sysroot/.nix", syscall.MS_REC|syscall.MS_RDONLY|syscall.MS_NODEV)
-		}, [][]kexpect{{
+		}, stub.Expect{Calls: []stub.Call{
-			{"evalSymlinks", expectArgs{"/sysroot/.nix"}, "/sysroot/NIX", nil},
+			call("evalSymlinks", stub.ExpectArgs{"/sysroot/.nix"}, "/sysroot/NIX", nil),
-			{"verbosef", expectArgs{"target resolves to %q", []any{"/sysroot/NIX"}}, nil, nil},
+			call("verbosef", stub.ExpectArgs{"target resolves to %q", []any{"/sysroot/NIX"}}, nil, nil),
-			{"open", expectArgs{"/sysroot/NIX", 0x280000, uint32(0)}, 0xdeadbeef, nil},
+			call("open", stub.ExpectArgs{"/sysroot/NIX", 0x280000, uint32(0)}, 0xdeadbeef, nil),
-			{"readlink", expectArgs{"/host/proc/self/fd/3735928559"}, "/sysroot/nix", nil},
+			call("readlink", stub.ExpectArgs{"/host/proc/self/fd/3735928559"}, "/sysroot/nix", nil),
-			{"close", expectArgs{0xdeadbeef}, nil, nil},
+			call("close", stub.ExpectArgs{0xdeadbeef}, nil, nil),
-			{"openNew", expectArgs{"/host/proc/self/mountinfo"}, newConstFile(sampleMountinfoNix), nil},
+			call("openNew", stub.ExpectArgs{"/host/proc/self/mountinfo"}, newConstFile(sampleMountinfoNix), nil),
-			{"mount", expectArgs{"none", "/sysroot/nix", "", uintptr(0x209027), ""}, nil, nil},
+			call("mount", stub.ExpectArgs{"none", "/sysroot/nix", "", uintptr(0x209027), ""}, nil, nil),
-			{"mount", expectArgs{"none", "/sysroot/nix/.ro-store", "", uintptr(0x209027), ""}, nil, nil},
+			call("mount", stub.ExpectArgs{"none", "/sysroot/nix/.ro-store", "", uintptr(0x209027), ""}, nil, nil),
-			{"mount", expectArgs{"none", "/sysroot/nix/store", "", uintptr(0x209027), ""}, nil, nil},
+			call("mount", stub.ExpectArgs{"none", "/sysroot/nix/store", "", uintptr(0x209027), ""}, nil, nil),
 		}}, nil},
 	})
 }
@@ -221,18 +219,18 @@ func TestRemountWithFlags(t *testing.T) {
 	checkSimple(t, "remountWithFlags", []simpleTestCase{
 		{"noop unmatched", func(k syscallDispatcher) error {
 			return remountWithFlags(k, &vfs.MountInfoNode{MountInfoEntry: &vfs.MountInfoEntry{VfsOptstr: "rw,relatime,cat"}}, 0)
-		}, [][]kexpect{{
+		}, stub.Expect{Calls: []stub.Call{
-			{"verbosef", expectArgs{"unmatched vfs options: %q", []any{[]string{"cat"}}}, nil, nil},
+			call("verbosef", stub.ExpectArgs{"unmatched vfs options: %q", []any{[]string{"cat"}}}, nil, nil),
 		}}, nil},
 
 		{"noop", func(k syscallDispatcher) error {
 			return remountWithFlags(k, &vfs.MountInfoNode{MountInfoEntry: &vfs.MountInfoEntry{VfsOptstr: "rw,relatime"}}, 0)
-		}, nil, nil},
+		}, stub.Expect{}, nil},
 
 		{"success", func(k syscallDispatcher) error {
 			return remountWithFlags(k, &vfs.MountInfoNode{MountInfoEntry: &vfs.MountInfoEntry{VfsOptstr: "rw,relatime"}}, syscall.MS_RDONLY)
-		}, [][]kexpect{{
+		}, stub.Expect{Calls: []stub.Call{
-			{"mount", expectArgs{"none", "", "", uintptr(0x209021), ""}, nil, nil},
+			call("mount", stub.ExpectArgs{"none", "", "", uintptr(0x209021), ""}, nil, nil),
 		}}, nil},
 	})
 }
@@ -241,22 +239,22 @@ func TestMountTmpfs(t *testing.T) {
 	checkSimple(t, "mountTmpfs", []simpleTestCase{
 		{"mkdirAll", func(k syscallDispatcher) error {
 			return mountTmpfs(k, "ephemeral", "/sysroot/run/user/1000", 0, 1<<10, 0700)
-		}, [][]kexpect{{
+		}, stub.Expect{Calls: []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot/run/user/1000", os.FileMode(0700)}, nil, errUnique},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/run/user/1000", os.FileMode(0700)}, nil, stub.UniqueError(0)),
-		}}, wrapErrSelf(errUnique)},
+		}}, stub.UniqueError(0)},
 
 		{"success no size", func(k syscallDispatcher) error {
 			return mountTmpfs(k, "ephemeral", "/sysroot/run/user/1000", 0, 0, 0710)
-		}, [][]kexpect{{
+		}, stub.Expect{Calls: []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot/run/user/1000", os.FileMode(0750)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/run/user/1000", os.FileMode(0750)}, nil, nil),
-			{"mount", expectArgs{"ephemeral", "/sysroot/run/user/1000", "tmpfs", uintptr(0), "mode=0710"}, nil, nil},
+			call("mount", stub.ExpectArgs{"ephemeral", "/sysroot/run/user/1000", "tmpfs", uintptr(0), "mode=0710"}, nil, nil),
 		}}, nil},
 
 		{"success", func(k syscallDispatcher) error {
 			return mountTmpfs(k, "ephemeral", "/sysroot/run/user/1000", 0, 1<<10, 0700)
-		}, [][]kexpect{{
+		}, stub.Expect{Calls: []stub.Call{
-			{"mkdirAll", expectArgs{"/sysroot/run/user/1000", os.FileMode(0700)}, nil, nil},
+			call("mkdirAll", stub.ExpectArgs{"/sysroot/run/user/1000", os.FileMode(0700)}, nil, nil),
-			{"mount", expectArgs{"ephemeral", "/sysroot/run/user/1000", "tmpfs", uintptr(0), "mode=0700,size=1024"}, nil, nil},
+			call("mount", stub.ExpectArgs{"ephemeral", "/sysroot/run/user/1000", "tmpfs", uintptr(0), "mode=0700,size=1024"}, nil, nil),
 		}}, nil},
 	})
 }

container/msg.go

@@ -2,24 +2,34 @@ package container
 
 import (
 	"errors"
-	"fmt"
 	"log"
-	"os"
-	"reflect"
 	"sync/atomic"
-	"testing"
 )
 
+// MessageError is an error with a user-facing message.
+type MessageError interface {
+	// Message returns a user-facing error message.
+	Message() string
+
+	error
+}
+
+// GetErrorMessage returns whether an error implements [MessageError], and the message if it does.
+func GetErrorMessage(err error) (string, bool) {
+	var e MessageError
+	if !errors.As(err, &e) || e == nil {
+		return zeroString, false
+	}
+	return e.Message(), true
+}
+
 type Msg interface {
 	IsVerbose() bool
 	Verbose(v ...any)
 	Verbosef(format string, v ...any)
-	WrapErr(err error, a ...any) error
-	PrintBaseErr(err error, fallback string)
 
 	Suspend()
 	Resume() bool
-
 	BeforeExit()
 }
 
@@ -37,32 +47,21 @@ func (msg *DefaultMsg) Verbosef(format string, v ...any) {
 	}
 }
 
-// checkedWrappedErr implements error with strict checks for wrapped values.
-type checkedWrappedErr struct {
-	err error
-	a   []any
-}
-
-func (c *checkedWrappedErr) Error() string { return fmt.Sprintf("%v, a = %s", c.err, c.a) }
-func (c *checkedWrappedErr) Is(err error) bool {
-	var concreteErr *checkedWrappedErr
-	if !errors.As(err, &concreteErr) {
-		return false
-	}
-	return reflect.DeepEqual(c, concreteErr)
-}
-
-func (msg *DefaultMsg) WrapErr(err error, a ...any) error {
-	// provide a mostly bulletproof path to bypass this behaviour in tests
-	if testing.Testing() && os.Getenv("GOPATH") != Nonexistent {
-		return &checkedWrappedErr{err, a}
-	}
-
-	log.Println(a...)
-	return err
-}
-func (msg *DefaultMsg) PrintBaseErr(err error, fallback string) { log.Println(fallback, err) }
-
 func (msg *DefaultMsg) Suspend()     { msg.inactive.Store(true) }
 func (msg *DefaultMsg) Resume() bool { return msg.inactive.CompareAndSwap(true, false) }
 func (msg *DefaultMsg) BeforeExit()  {}
+
+// msg is the [Msg] implemented used by all exported [container] functions.
+var msg Msg = new(DefaultMsg)
+
+// GetOutput returns the current active [Msg] implementation.
+func GetOutput() Msg { return msg }
+
+// SetOutput replaces the current active [Msg] implementation.
+func SetOutput(v Msg) {
+	if v == nil {
+		msg = new(DefaultMsg)
+	} else {
+		msg = v
+	}
+}

container/msg_test.go

@@ -9,13 +9,36 @@ import (
 	"testing"
 
 	"hakurei.app/container"
-	"hakurei.app/internal/hlog"
 )
 
-func TestDefaultMsg(t *testing.T) {
+func TestMessageError(t *testing.T) {
-	// bypass WrapErr testing behaviour
+	testCases := []struct {
-	t.Setenv("GOPATH", container.Nonexistent)
+		name   string
+		err    error
+		want   string
+		wantOk bool
+	}{
+		{"nil", nil, "", false},
+		{"new", errors.New(":3"), "", false},
+		{"start", &container.StartError{
+			Step: "meow",
+			Err:  syscall.ENOTRECOVERABLE,
+		}, "cannot meow: state not recoverable", true},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			got, ok := container.GetErrorMessage(tc.err)
+			if got != tc.want {
+				t.Errorf("GetErrorMessage: %q, want %q", got, tc.want)
+			}
+			if ok != tc.wantOk {
+				t.Errorf("GetErrorMessage: ok = %v, want %v", ok, tc.wantOk)
+			}
+		})
+	}
+}
 
+func TestDefaultMsg(t *testing.T) {
 	{
 		w := log.Writer()
 		f := log.Flags()
@@ -48,21 +71,6 @@ func TestDefaultMsg(t *testing.T) {
 		}
 	})
 
-	t.Run("wrapErr", func(t *testing.T) {
-		buf := new(strings.Builder)
-		log.SetOutput(buf)
-		log.SetFlags(0)
-		if err := msg.WrapErr(syscall.EBADE, "\x00", "\x00"); err != syscall.EBADE {
-			t.Errorf("WrapErr: %v", err)
-		}
-		msg.PrintBaseErr(syscall.ENOTRECOVERABLE, "cannot cuddle cat:")
-
-		want := "\x00 \x00\ncannot cuddle cat: state not recoverable\n"
-		if buf.String() != want {
-			t.Errorf("WrapErr: %q, want %q", buf.String(), want)
-		}
-	})
-
 	t.Run("inactive", func(t *testing.T) {
 		{
 			inactive := msg.Resume()
@@ -83,25 +91,6 @@ func TestDefaultMsg(t *testing.T) {
 
 	// the function is a noop
 	t.Run("beforeExit", func(t *testing.T) { msg.BeforeExit() })
-
-	t.Run("checkedWrappedErr", func(t *testing.T) {
-		// temporarily re-enable testing behaviour
-		t.Setenv("GOPATH", "")
-		wrappedErr := msg.WrapErr(syscall.ENOTRECOVERABLE, "cannot cuddle cat:", syscall.ENOTRECOVERABLE)
-
-		t.Run("string", func(t *testing.T) {
-			want := "state not recoverable, a = [cannot cuddle cat: state not recoverable]"
-			if got := wrappedErr.Error(); got != want {
-				t.Errorf("Error: %q, want %q", got, want)
-			}
-		})
-
-		t.Run("bad concrete type", func(t *testing.T) {
-			if errors.Is(wrappedErr, syscall.ENOTRECOVERABLE) {
-				t.Error("incorrect type assertion")
-			}
-		})
-	})
 }
 
 type panicWriter struct{}
@@ -139,9 +128,6 @@ func (out *testOutput) Verbosef(format string, v ...any) {
 	out.t.Logf(format, v...)
 }
 
-func (out *testOutput) WrapErr(err error, a ...any) error       { return hlog.WrapErr(err, a...) }
-func (out *testOutput) PrintBaseErr(err error, fallback string) { hlog.PrintBaseError(err, fallback) }
-
 func (out *testOutput) Suspend() {
 	if out.suspended.CompareAndSwap(false, true) {
 		out.Verbose("suspend called")
@@ -160,3 +146,39 @@ func (out *testOutput) Resume() bool {
 }
 
 func (out *testOutput) BeforeExit() { out.Verbose("beforeExit called") }
+
+func TestGetSetOutput(t *testing.T) {
+	{
+		out := container.GetOutput()
+		t.Cleanup(func() { container.SetOutput(out) })
+	}
+
+	t.Run("default", func(t *testing.T) {
+		container.SetOutput(new(stubOutput))
+		if v, ok := container.GetOutput().(*container.DefaultMsg); ok {
+			t.Fatalf("SetOutput: got unexpected output %#v", v)
+		}
+		container.SetOutput(nil)
+		if _, ok := container.GetOutput().(*container.DefaultMsg); !ok {
+			t.Fatalf("SetOutput: got unexpected output %#v", container.GetOutput())
+		}
+	})
+
+	t.Run("stub", func(t *testing.T) {
+		container.SetOutput(new(stubOutput))
+		if _, ok := container.GetOutput().(*stubOutput); !ok {
+			t.Fatalf("SetOutput: got unexpected output %#v", container.GetOutput())
+		}
+	})
+}
+
+type stubOutput struct {
+	wrapF func(error, ...any) error
+}
+
+func (*stubOutput) IsVerbose() bool         { panic("unreachable") }
+func (*stubOutput) Verbose(...any)          { panic("unreachable") }
+func (*stubOutput) Verbosef(string, ...any) { panic("unreachable") }
+func (*stubOutput) Suspend()                { panic("unreachable") }
+func (*stubOutput) Resume() bool            { panic("unreachable") }
+func (*stubOutput) BeforeExit()             { panic("unreachable") }

container/output.go

@@ -1,26 +1,77 @@
 package container
 
-var msg Msg = new(DefaultMsg)
+import (
+	"bytes"
+	"io"
+	"sync"
+	"sync/atomic"
+	"syscall"
+)
 
-func GetOutput() Msg { return msg }
+const (
-func SetOutput(v Msg) {
+	suspendBufInitial = 1 << 12
-	if v == nil {
+	suspendBufMax     = 1 << 24
-		msg = new(DefaultMsg)
+)
-	} else {
+
-		msg = v
+// Suspendable proxies writes to a downstream [io.Writer] but optionally withholds writes
-	}
+// between calls to Suspend and Resume.
+type Suspendable struct {
+	Downstream io.Writer
+
+	s atomic.Bool
+
+	buf bytes.Buffer
+	// for growing buf
+	bufOnce sync.Once
+	// for synchronising all other buf operations
+	bufMu sync.Mutex
+
+	dropped int
 }
 
-func wrapErrSuffix(err error, a ...any) error {
+func (s *Suspendable) Write(p []byte) (n int, err error) {
-	if err == nil {
+	if !s.s.Load() {
-		return nil
+		return s.Downstream.Write(p)
 	}
-	return msg.WrapErr(err, append(a, err)...)
+	s.bufOnce.Do(func() { s.buf.Grow(suspendBufInitial) })
+
+	s.bufMu.Lock()
+	defer s.bufMu.Unlock()
+
+	if free := suspendBufMax - s.buf.Len(); free < len(p) {
+		// fast path
+		if free <= 0 {
+			s.dropped += len(p)
+			return 0, syscall.ENOMEM
+		}
+
+		n, _ = s.buf.Write(p[:free])
+		err = syscall.ENOMEM
+		s.dropped += len(p) - n
+		return
+	}
+
+	return s.buf.Write(p)
 }
 
-func wrapErrSelf(err error) error {
+// IsSuspended returns whether [Suspendable] is currently between a call to Suspend and Resume.
-	if err == nil {
+func (s *Suspendable) IsSuspended() bool { return s.s.Load() }
-		return nil
+
+// Suspend causes [Suspendable] to start withholding output in its buffer.
+func (s *Suspendable) Suspend() bool { return s.s.CompareAndSwap(false, true) }
+
+// Resume undoes the effect of Suspend and dumps the buffered into the downstream [io.Writer].
+func (s *Suspendable) Resume() (resumed bool, dropped uintptr, n int64, err error) {
+	if s.s.CompareAndSwap(true, false) {
+		s.bufMu.Lock()
+		defer s.bufMu.Unlock()
+
+		resumed = true
+		dropped = uintptr(s.dropped)
+
+		s.dropped = 0
+		n, err = io.Copy(s.Downstream, &s.buf)
+		s.buf.Reset()
 	}
-	return msg.WrapErr(err, err.Error())
+	return
 }

container/output_test.go

@@ -1,110 +1,155 @@
-package container
+package container_test
 
 import (
+	"bytes"
+	"errors"
 	"reflect"
+	"strconv"
 	"syscall"
 	"testing"
+
+	"hakurei.app/container"
+	"hakurei.app/container/stub"
 )
 
-func TestGetSetOutput(t *testing.T) {
+func TestSuspendable(t *testing.T) {
-	{
+	// copied from output.go
-		out := GetOutput()
+	const suspendBufMax = 1 << 24
-		t.Cleanup(func() { SetOutput(out) })
-	}
 
-	t.Run("default", func(t *testing.T) {
+	const (
-		SetOutput(new(stubOutput))
+		// equivalent to len(want.pt)
-		if v, ok := GetOutput().(*DefaultMsg); ok {
+		nSpecialPtEquiv = -iota - 1
-			t.Fatalf("SetOutput: got unexpected output %#v", v)
+		// equivalent to len(want.w)
-		}
+		nSpecialWEquiv
-		SetOutput(nil)
+		// suspends writer before executing test case, implies nSpecialWEquiv
-		if _, ok := GetOutput().(*DefaultMsg); !ok {
+		nSpecialSuspend
-			t.Fatalf("SetOutput: got unexpected output %#v", GetOutput())
+		// offset: resume writer and measure against dump instead, implies nSpecialPtEquiv
-		}
+		nSpecialDump
-	})
+	)
-
-	t.Run("stub", func(t *testing.T) {
-		SetOutput(new(stubOutput))
-		if _, ok := GetOutput().(*stubOutput); !ok {
-			t.Fatalf("SetOutput: got unexpected output %#v", GetOutput())
-		}
-	})
-}
-
-func TestWrapErr(t *testing.T) {
-	{
-		out := GetOutput()
-		t.Cleanup(func() { SetOutput(out) })
-	}
-
-	var wrapFp *func(error, ...any) error
-	s := new(stubOutput)
-	SetOutput(s)
-	wrapFp = &s.wrapF
 
+	// shares the same writer
 	testCases := []struct {
 		name    string
-		f       func(t *testing.T)
+		w, pt   []byte
+		err     error
 		wantErr error
-		wantA   []any
+		n       int
 	}{
-		{"suffix nil", func(t *testing.T) {
+		{"simple", []byte{0xde, 0xad, 0xbe, 0xef}, []byte{0xde, 0xad, 0xbe, 0xef},
-			if err := wrapErrSuffix(nil, "\x00"); err != nil {
+			nil, nil, nSpecialPtEquiv},
-				t.Errorf("wrapErrSuffix: %v", err)
+
-			}
+		{"error", []byte{0xb, 0xad}, []byte{0xb, 0xad},
-		}, nil, nil},
+			stub.UniqueError(0), stub.UniqueError(0), nSpecialPtEquiv},
-		{"suffix val", func(t *testing.T) {
+
-			if err := wrapErrSuffix(syscall.ENOTRECOVERABLE, "\x00\x00"); err != syscall.ENOTRECOVERABLE {
+		{"suspend short", []byte{0}, nil,
-				t.Errorf("wrapErrSuffix: %v", err)
+			nil, nil, nSpecialSuspend},
-			}
+		{"sw short 0", []byte{0xca, 0xfe, 0xba, 0xbe}, nil,
-		}, syscall.ENOTRECOVERABLE, []any{"\x00\x00", syscall.ENOTRECOVERABLE}},
+			nil, nil, nSpecialWEquiv},
-		{"self nil", func(t *testing.T) {
+		{"sw short 1", []byte{0xff}, nil,
-			if err := wrapErrSelf(nil); err != nil {
+			nil, nil, nSpecialWEquiv},
-				t.Errorf("wrapErrSelf: %v", err)
+		{"resume short", nil, []byte{0, 0xca, 0xfe, 0xba, 0xbe, 0xff}, nil, nil,
-			}
+			nSpecialDump},
-		}, nil, nil},
+
-		{"self val", func(t *testing.T) {
+		{"long pt", bytes.Repeat([]byte{0xff}, suspendBufMax+1), bytes.Repeat([]byte{0xff}, suspendBufMax+1),
-			if err := wrapErrSelf(syscall.ENOTRECOVERABLE); err != syscall.ENOTRECOVERABLE {
+			nil, nil, nSpecialPtEquiv},
-				t.Errorf("wrapErrSelf: %v", err)
+
-			}
+		{"suspend fill", bytes.Repeat([]byte{0xfe}, suspendBufMax), nil,
-		}, syscall.ENOTRECOVERABLE, []any{"state not recoverable"}},
+			nil, nil, nSpecialSuspend},
+		{"drop", []byte{0}, nil,
+			nil, syscall.ENOMEM, 0},
+		{"drop error", []byte{0}, nil,
+			stub.UniqueError(1), syscall.ENOMEM, 0},
+		{"resume fill", nil, bytes.Repeat([]byte{0xfe}, suspendBufMax),
+			nil, nil, nSpecialDump - 2},
+
+		{"suspend fill partial", bytes.Repeat([]byte{0xfd}, suspendBufMax-0xf), nil,
+			nil, nil, nSpecialSuspend},
+		{"partial write", bytes.Repeat([]byte{0xad}, 0x1f), nil,
+			nil, syscall.ENOMEM, 0xf},
+		{"full drop", []byte{0}, nil,
+			nil, syscall.ENOMEM, 0},
+		{"resume fill partial", nil, append(bytes.Repeat([]byte{0xfd}, suspendBufMax-0xf), bytes.Repeat([]byte{0xad}, 0xf)...),
+			nil, nil, nSpecialDump - 0x10 - 1},
 	}
 
+	var dw expectWriter
+
+	w := container.Suspendable{Downstream: &dw}
 	for _, tc := range testCases {
-		t.Run(tc.name, func(t *testing.T) {
+		// these share the same writer, so cannot be subtests
-			var (
+		t.Logf("writing step %q", tc.name)
-				gotErr error
+		dw.expect, dw.err = tc.pt, tc.err
-				gotA   []any
-			)
-			*wrapFp = func(err error, a ...any) error { gotErr = err; gotA = a; return err }
 
-			tc.f(t)
+		var (
-			if gotErr != tc.wantErr {
+			gotN   int
-				t.Errorf("WrapErr: err = %v, want %v", gotErr, tc.wantErr)
+			gotErr error
+		)
+
+		wantN := tc.n
+		switch wantN {
+		case nSpecialPtEquiv:
+			wantN = len(tc.pt)
+			gotN, gotErr = w.Write(tc.w)
+
+		case nSpecialWEquiv:
+			wantN = len(tc.w)
+			gotN, gotErr = w.Write(tc.w)
+
+		case nSpecialSuspend:
+			s := w.IsSuspended()
+			if ok := w.Suspend(); s && ok {
+				t.Fatal("Suspend: unexpected success")
 			}
 
-			if !reflect.DeepEqual(gotA, tc.wantA) {
+			wantN = len(tc.w)
-				t.Errorf("WrapErr: a = %v, want %v", gotA, tc.wantA)
+			gotN, gotErr = w.Write(tc.w)
+
+		default:
+			if wantN <= nSpecialDump {
+				if !w.IsSuspended() {
+					t.Fatal("IsSuspended unexpected false")
+				}
+
+				resumed, dropped, n, err := w.Resume()
+				if !resumed {
+					t.Fatal("Resume: resumed = false")
+				}
+				if wantDropped := nSpecialDump - wantN; int(dropped) != wantDropped {
+					t.Errorf("Resume: dropped = %d, want %d", dropped, wantDropped)
+				}
+
+				wantN = len(tc.pt)
+				gotN, gotErr = int(n), err
+			} else {
+				gotN, gotErr = w.Write(tc.w)
 			}
-		})
+		}
+
+		if gotN != wantN {
+			t.Errorf("Write: n = %d, want %d", gotN, wantN)
+		}
+
+		if !reflect.DeepEqual(gotErr, tc.wantErr) {
+			t.Errorf("Write: %v", gotErr)
+		}
 	}
 }
 
-type stubOutput struct {
+// expectWriter compares Write calls to expect.
-	wrapF func(error, ...any) error
+type expectWriter struct {
+	expect []byte
+	err    error
 }
 
-func (*stubOutput) IsVerbose() bool            { panic("unreachable") }
+func (w *expectWriter) Write(p []byte) (n int, err error) {
-func (*stubOutput) Verbose(...any)             { panic("unreachable") }
+	defer func() { w.expect = nil }()
-func (*stubOutput) Verbosef(string, ...any)    { panic("unreachable") }
-func (*stubOutput) PrintBaseErr(error, string) { panic("unreachable") }
-func (*stubOutput) Suspend()                   { panic("unreachable") }
-func (*stubOutput) Resume() bool               { panic("unreachable") }
-func (*stubOutput) BeforeExit()                { panic("unreachable") }
 
-func (s *stubOutput) WrapErr(err error, v ...any) error {
+	n, err = len(p), w.err
-	if s.wrapF == nil {
+	if w.expect == nil {
-		panic("unreachable")
+		return 0, errors.New("unexpected call to Write: " + strconv.Quote(string(p)))
 	}
-	return s.wrapF(err, v...)
+	if string(p) != string(w.expect) {
+		return 0, errors.New("p = " + strconv.Quote(string(p)) + ", want " + strconv.Quote(string(w.expect)))
+	}
+	return
 }

container/params.go

@@ -8,11 +8,6 @@ import (
 	"syscall"
 )
 
-var (
-	ErrNotSet   = errors.New("environment variable not set")
-	ErrFdFormat = errors.New("bad file descriptor representation")
-)
-
 // Setup appends the read end of a pipe for setup params transmission and returns its fd.
 func Setup(extraFiles *[]*os.File) (int, *gob.Encoder, error) {
 	if r, w, err := os.Pipe(); err != nil {
@@ -24,19 +19,23 @@ func Setup(extraFiles *[]*os.File) (int, *gob.Encoder, error) {
 	}
 }
 
+var (
+	ErrReceiveEnv = errors.New("environment variable not set")
+)
+
 // Receive retrieves setup fd from the environment and receives params.
 func Receive(key string, e any, fdp *uintptr) (func() error, error) {
 	var setup *os.File
 
 	if s, ok := os.LookupEnv(key); !ok {
-		return nil, ErrNotSet
+		return nil, ErrReceiveEnv
 	} else {
 		if fd, err := strconv.Atoi(s); err != nil {
-			return nil, ErrFdFormat
+			return nil, errors.Unwrap(err)
 		} else {
 			setup = os.NewFile(uintptr(fd), "setup")
 			if setup == nil {
-				return nil, syscall.EBADF
+				return nil, syscall.EDOM
 			}
 			if fdp != nil {
 				*fdp = setup.Fd()

container/params_test.go

@@ -29,8 +29,8 @@ func TestSetupReceive(t *testing.T) {
 			})
 		}
 
-		if _, err := container.Receive(key, nil, nil); !errors.Is(err, container.ErrNotSet) {
+		if _, err := container.Receive(key, nil, nil); !errors.Is(err, container.ErrReceiveEnv) {
-			t.Errorf("Receive: error = %v, want %v", err, container.ErrNotSet)
+			t.Errorf("Receive: error = %v, want %v", err, container.ErrReceiveEnv)
 		}
 	})
 
@@ -38,8 +38,8 @@ func TestSetupReceive(t *testing.T) {
 		const key = "TEST_ENV_FORMAT"
 		t.Setenv(key, "")
 
-		if _, err := container.Receive(key, nil, nil); !errors.Is(err, container.ErrFdFormat) {
+		if _, err := container.Receive(key, nil, nil); !errors.Is(err, strconv.ErrSyntax) {
-			t.Errorf("Receive: error = %v, want %v", err, container.ErrFdFormat)
+			t.Errorf("Receive: error = %v, want %v", err, strconv.ErrSyntax)
 		}
 	})
 
@@ -47,8 +47,8 @@ func TestSetupReceive(t *testing.T) {
 		const key = "TEST_ENV_RANGE"
 		t.Setenv(key, "-1")
 
-		if _, err := container.Receive(key, nil, nil); !errors.Is(err, syscall.EBADF) {
+		if _, err := container.Receive(key, nil, nil); !errors.Is(err, syscall.EDOM) {
-			t.Errorf("Receive: error = %v, want %v", err, syscall.EBADF)
+			t.Errorf("Receive: error = %v, want %v", err, syscall.EDOM)
 		}
 	})
 

container/path.go

@@ -2,7 +2,6 @@ package container
 
 import (
 	"errors"
-	"fmt"
 	"io/fs"
 	"os"
 	"path"
@@ -103,30 +102,29 @@ func toHost(name string) string {
 
 func createFile(name string, perm, pperm os.FileMode, content []byte) error {
 	if err := os.MkdirAll(path.Dir(name), pperm); err != nil {
-		return wrapErrSelf(err)
+		return err
 	}
 	f, err := os.OpenFile(name, syscall.O_CREAT|syscall.O_EXCL|syscall.O_WRONLY, perm)
 	if err != nil {
-		return wrapErrSelf(err)
+		return err
 	}
 	if content != nil {
 		_, err = f.Write(content)
 	}
-	return errors.Join(f.Close(), wrapErrSelf(err))
+	return errors.Join(f.Close(), err)
 }
 
 func ensureFile(name string, perm, pperm os.FileMode) error {
 	fi, err := os.Stat(name)
 	if err != nil {
 		if !os.IsNotExist(err) {
-			return wrapErrSelf(err)
+			return err
 		}
 		return createFile(name, perm, pperm, nil)
 	}
 
 	if mode := fi.Mode(); mode&fs.ModeDir != 0 || mode&fs.ModeSymlink != 0 {
-		err = msg.WrapErr(syscall.EISDIR,
+		err = &os.PathError{Op: "ensure", Path: name, Err: syscall.EISDIR}
-			fmt.Sprintf("path %q is a directory", name))
 	}
 	return err
 }
@@ -147,15 +145,14 @@ func (p *procPaths) stdout() string   { return p.self + "/fd/1" }
 func (p *procPaths) fd(fd int) string { return p.self + "/fd/" + strconv.Itoa(fd) }
 func (p *procPaths) mountinfo(f func(d *vfs.MountInfoDecoder) error) error {
 	if r, err := p.k.openNew(p.self + "/mountinfo"); err != nil {
-		return wrapErrSelf(err)
+		return err
 	} else {
 		d := vfs.NewMountInfoDecoder(r)
 		err0 := f(d)
 		if err = r.Close(); err != nil {
-			return wrapErrSelf(err)
+			return err
 		} else if err = d.Err(); err != nil {
-			return wrapErrSuffix(err,
+			return err
-				"cannot parse mountinfo:")
 		}
 		return err0
 	}

container/path_test.go

@@ -1,8 +1,6 @@
 package container
 
 import (
-	"errors"
-	"fmt"
 	"io"
 	"math"
 	"os"
@@ -56,20 +54,27 @@ func InternalToHostOvlEscape(s string) string { return EscapeOverlayDataSegment(
 
 func TestCreateFile(t *testing.T) {
 	t.Run("nonexistent", func(t *testing.T) {
-		if err := createFile(path.Join(Nonexistent, ":3"), 0644, 0755, nil); !errors.Is(err, wrapErrSelf(&os.PathError{
+		t.Run("mkdir", func(t *testing.T) {
-			Op:   "mkdir",
+			wantErr := &os.PathError{
-			Path: "/proc/nonexistent",
+				Op:   "mkdir",
-			Err:  syscall.ENOENT,
+				Path: "/proc/nonexistent",
-		})) {
+				Err:  syscall.ENOENT,
-			t.Errorf("createFile: error = %v", err)
+			}
-		}
+			if err := createFile(path.Join(Nonexistent, ":3"), 0644, 0755, nil); !reflect.DeepEqual(err, wantErr) {
-		if err := createFile(path.Join(Nonexistent), 0644, 0755, nil); !errors.Is(err, wrapErrSelf(&os.PathError{
+				t.Errorf("createFile: error = %#v, want %#v", err, wantErr)
-			Op:   "open",
+			}
-			Path: "/proc/nonexistent",
+		})
-			Err:  syscall.ENOENT,
+
-		})) {
+		t.Run("open", func(t *testing.T) {
-			t.Errorf("createFile: error = %v", err)
+			wantErr := &os.PathError{
-		}
+				Op:   "open",
+				Path: "/proc/nonexistent",
+				Err:  syscall.ENOENT,
+			}
+			if err := createFile(path.Join(Nonexistent), 0644, 0755, nil); !reflect.DeepEqual(err, wantErr) {
+				t.Errorf("createFile: error = %#v, want %#v", err, wantErr)
+			}
+		})
 	})
 
 	t.Run("touch", func(t *testing.T) {
@@ -120,13 +125,13 @@ func TestEnsureFile(t *testing.T) {
 				t.Fatalf("Chmod: error = %v", err)
 			}
 
-			wantErr := wrapErrSelf(&os.PathError{
+			wantErr := &os.PathError{
 				Op:   "stat",
 				Path: pathname,
 				Err:  syscall.EACCES,
-			})
+			}
-			if err := ensureFile(pathname, 0644, 0755); !errors.Is(err, wantErr) {
+			if err := ensureFile(pathname, 0644, 0755); !reflect.DeepEqual(err, wantErr) {
-				t.Errorf("ensureFile: error = %v, want %v", err, wantErr)
+				t.Errorf("ensureFile: error = %#v, want %#v", err, wantErr)
 			}
 
 			if err := os.Chmod(tempDir, 0755); err != nil {
@@ -136,9 +141,9 @@ func TestEnsureFile(t *testing.T) {
 
 		t.Run("directory", func(t *testing.T) {
 			pathname := t.TempDir()
-			wantErr := msg.WrapErr(syscall.EISDIR, fmt.Sprintf("path %q is a directory", pathname))
+			wantErr := &os.PathError{Op: "ensure", Path: pathname, Err: syscall.EISDIR}
-			if err := ensureFile(pathname, 0644, 0755); !errors.Is(err, wantErr) {
+			if err := ensureFile(pathname, 0644, 0755); !reflect.DeepEqual(err, wantErr) {
-				t.Errorf("ensureFile: error = %v, want %v", err, wantErr)
+				t.Errorf("ensureFile: error = %#v, want %#v", err, wantErr)
 			}
 		})
 
@@ -177,12 +182,12 @@ func TestProcPaths(t *testing.T) {
 	t.Run("mountinfo", func(t *testing.T) {
 		t.Run("nonexistent", func(t *testing.T) {
 			nonexistentProc := newProcPaths(direct{}, t.TempDir())
-			wantErr := wrapErrSelf(&os.PathError{
+			wantErr := &os.PathError{
 				Op:   "open",
 				Path: nonexistentProc.self + "/mountinfo",
 				Err:  syscall.ENOENT,
-			})
+			}
-			if err := nonexistentProc.mountinfo(func(*vfs.MountInfoDecoder) error { return syscall.EINVAL }); !errors.Is(err, wantErr) {
+			if err := nonexistentProc.mountinfo(func(*vfs.MountInfoDecoder) error { return syscall.EINVAL }); !reflect.DeepEqual(err, wantErr) {
 				t.Errorf("mountinfo: error = %v, want %v", err, wantErr)
 			}
 		})
@@ -217,11 +222,11 @@ func TestProcPaths(t *testing.T) {
 
 			t.Run("closed", func(t *testing.T) {
 				p := newProcPaths(direct{}, tempDir)
-				wantErr := wrapErrSelf(&os.PathError{
+				wantErr := &os.PathError{
 					Op:   "close",
 					Path: p.self + "/mountinfo",
 					Err:  os.ErrClosed,
-				})
+				}
 				if err := p.mountinfo(func(d *vfs.MountInfoDecoder) error {
 					v := reflect.ValueOf(d).Elem().FieldByName("s").Elem().FieldByName("r")
 					v = reflect.NewAt(v.Type(), unsafe.Pointer(v.UnsafeAddr()))
@@ -231,8 +236,8 @@ func TestProcPaths(t *testing.T) {
 					} else {
 						return f.Close()
 					}
-				}); !errors.Is(err, wantErr) {
+				}); !reflect.DeepEqual(err, wantErr) {
-					t.Errorf("mountinfo: error = %v, want %v", err, wantErr)
+					t.Errorf("mountinfo: error = %#v, want %#v", err, wantErr)
 				}
 			})
 
@@ -242,8 +247,8 @@ func TestProcPaths(t *testing.T) {
 					t.Fatalf("WriteFile: error = %v", err)
 				}
 
-				wantErr := wrapErrSuffix(vfs.ErrMountInfoFields, "cannot parse mountinfo:")
+				wantErr := &vfs.DecoderError{Op: "parse", Line: 0, Err: vfs.ErrMountInfoFields}
-				if err := newProcPaths(direct{}, tempDir).mountinfo(func(d *vfs.MountInfoDecoder) error { return d.Decode(new(*vfs.MountInfo)) }); !errors.Is(err, wantErr) {
+				if err := newProcPaths(direct{}, tempDir).mountinfo(func(d *vfs.MountInfoDecoder) error { return d.Decode(new(*vfs.MountInfo)) }); !reflect.DeepEqual(err, wantErr) {
 					t.Fatalf("mountinfo: error = %v, want %v", err, wantErr)
 				}
 			})

container/stub/call.go

@@ -0,0 +1,37 @@
+package stub
+
+import (
+	"slices"
+)
+
+// ExpectArgs is an array primarily for storing expected function arguments.
+// Its actual use is defined by the implementation.
+type ExpectArgs = [5]any
+
+// An Expect stores expected calls of a goroutine.
+type Expect struct {
+	Calls []Call
+
+	// Tracks are handed out to descendant goroutines in order.
+	Tracks []Expect
+}
+
+// A Call holds expected arguments of a function call and its outcome.
+type Call struct {
+	// Name is the function Name of this call. Must be unique.
+	Name string
+	// Args are the expected arguments of this Call.
+	Args ExpectArgs
+	// Ret is the return value of this Call.
+	Ret any
+	// Err is the returned error of this Call.
+	Err error
+}
+
+// Error returns [Call.Err] if all arguments are true, or [ErrCheck] otherwise.
+func (k *Call) Error(ok ...bool) error {
+	if !slices.Contains(ok, false) {
+		return k.Err
+	}
+	return ErrCheck
+}

container/stub/call_test.go

@@ -0,0 +1,23 @@
+package stub_test
+
+import (
+	"reflect"
+	"testing"
+
+	"hakurei.app/container/stub"
+)
+
+func TestCallError(t *testing.T) {
+	t.Run("contains false", func(t *testing.T) {
+		if err := new(stub.Call).Error(true, false, true); !reflect.DeepEqual(err, stub.ErrCheck) {
+			t.Errorf("Error: %#v, want %#v", err, stub.ErrCheck)
+		}
+	})
+
+	t.Run("passthrough", func(t *testing.T) {
+		wantErr := stub.UniqueError(0xbabe)
+		if err := (&stub.Call{Err: wantErr}).Error(true); !reflect.DeepEqual(err, wantErr) {
+			t.Errorf("Error: %#v, want %#v", err, wantErr)
+		}
+	})
+}

container/stub/errors.go

@@ -0,0 +1,25 @@
+package stub
+
+import (
+	"errors"
+	"strconv"
+)
+
+var (
+	ErrCheck = errors.New("one or more arguments did not match")
+)
+
+// UniqueError is an error that only equivalates to other [UniqueError] with the same magic value.
+type UniqueError uintptr
+
+func (e UniqueError) Error() string {
+	return "unique error " + strconv.Itoa(int(e)) + " injected by the test suite"
+}
+
+func (e UniqueError) Is(target error) bool {
+	var u UniqueError
+	if !errors.As(target, &u) {
+		return false
+	}
+	return e == u
+}

container/stub/errors_test.go

@@ -0,0 +1,35 @@
+package stub_test
+
+import (
+	"errors"
+	"syscall"
+	"testing"
+
+	"hakurei.app/container/stub"
+)
+
+func TestUniqueError(t *testing.T) {
+	t.Run("format", func(t *testing.T) {
+		want := "unique error 2989 injected by the test suite"
+		if got := stub.UniqueError(0xbad).Error(); got != want {
+			t.Errorf("Error: %q, want %q", got, want)
+		}
+	})
+
+	t.Run("is", func(t *testing.T) {
+		t.Run("type", func(t *testing.T) {
+			if errors.Is(stub.UniqueError(0), syscall.ENOTRECOVERABLE) {
+				t.Error("Is: unexpected true")
+			}
+		})
+
+		t.Run("val", func(t *testing.T) {
+			if errors.Is(stub.UniqueError(0), stub.UniqueError(1)) {
+				t.Error("Is: unexpected true")
+			}
+			if !errors.Is(stub.UniqueError(0xbad), stub.UniqueError(0xbad)) {
+				t.Error("Is: unexpected false")
+			}
+		})
+	})
+}

container/stub/exit.go

@@ -0,0 +1,44 @@
+package stub
+
+import "testing"
+
+// PanicExit is a magic panic value treated as a simulated exit.
+const PanicExit = 0xdeadbeef
+
+const (
+	panicFailNow = 0xcafe0000 + iota
+	panicFatal
+	panicFatalf
+)
+
+// HandleExit must be deferred before calling with the stub.
+func HandleExit(t testing.TB) {
+	switch r := recover(); r {
+	case PanicExit:
+		break
+
+	case panicFailNow:
+		t.FailNow()
+
+	case panicFatal, panicFatalf, nil:
+		break
+
+	default:
+		panic(r)
+	}
+}
+
+// handleExitNew handles exits from goroutines created by [Stub.New].
+func handleExitNew(t testing.TB) {
+	switch r := recover(); r {
+	case PanicExit, panicFatal, panicFatalf, nil:
+		break
+
+	case panicFailNow:
+		t.Fail()
+		break
+
+	default:
+		panic(r)
+	}
+}

container/stub/exit_test.go

@@ -0,0 +1,93 @@
+package stub_test
+
+import (
+	"testing"
+	_ "unsafe"
+
+	"hakurei.app/container/stub"
+)
+
+//go:linkname handleExitNew hakurei.app/container/stub.handleExitNew
+func handleExitNew(_ testing.TB)
+
+// overrideTFailNow overrides the Fail and FailNow method.
+type overrideTFailNow struct {
+	*testing.T
+	failNow bool
+	fail    bool
+}
+
+func (o *overrideTFailNow) FailNow() {
+	if o.failNow {
+		o.Errorf("attempted to FailNow twice")
+	}
+	o.failNow = true
+}
+
+func (o *overrideTFailNow) Fail() {
+	if o.fail {
+		o.Errorf("attempted to Fail twice")
+	}
+	o.fail = true
+}
+
+func TestHandleExit(t *testing.T) {
+	t.Run("exit", func(t *testing.T) {
+		defer stub.HandleExit(t)
+		panic(stub.PanicExit)
+	})
+
+	t.Run("goexit", func(t *testing.T) {
+		t.Run("FailNow", func(t *testing.T) {
+			ot := &overrideTFailNow{T: t}
+			defer func() {
+				if !ot.failNow {
+					t.Errorf("FailNow was never called")
+				}
+			}()
+			defer stub.HandleExit(ot)
+			panic(0xcafe0000)
+		})
+
+		t.Run("Fail", func(t *testing.T) {
+			ot := &overrideTFailNow{T: t}
+			defer func() {
+				if !ot.fail {
+					t.Errorf("Fail was never called")
+				}
+			}()
+			defer handleExitNew(ot)
+			panic(0xcafe0000)
+		})
+	})
+
+	t.Run("nil", func(t *testing.T) {
+		defer stub.HandleExit(t)
+	})
+
+	t.Run("passthrough", func(t *testing.T) {
+		t.Run("toplevel", func(t *testing.T) {
+			defer func() {
+				want := 0xcafebabe
+				if r := recover(); r != want {
+					t.Errorf("recover: %v, want %v", r, want)
+				}
+
+			}()
+			defer stub.HandleExit(t)
+			panic(0xcafebabe)
+		})
+
+		t.Run("new", func(t *testing.T) {
+			defer func() {
+				want := 0xcafe
+				if r := recover(); r != want {
+					t.Errorf("recover: %v, want %v", r, want)
+				}
+
+			}()
+			defer handleExitNew(t)
+			panic(0xcafe)
+		})
+	})
+}

container/stub/stub.go

@@ -0,0 +1,148 @@
+// Package stub provides function call level stubbing and validation
+// for library functions that are impossible to check otherwise.
+package stub
+
+import (
+	"reflect"
+	"sync"
+	"testing"
+)
+
+// this should prevent stub from being inadvertently imported outside tests
+var _ = func() {
+	if !testing.Testing() {
+		panic("stub imported while not in a test")
+	}
+}
+
+const (
+	// A CallSeparator denotes an injected separation between two groups of calls.
+	CallSeparator = "\x00"
+)
+
+// A Stub is a collection of tracks of expected calls.
+type Stub[K any] struct {
+	testing.TB
+
+	// makeK creates a new K for a descendant [Stub].
+	// This function may be called concurrently.
+	makeK func(s *Stub[K]) K
+
+	// want is a hierarchy of expected calls.
+	want Expect
+	// pos is the current position in [Expect.Calls].
+	pos int
+	// goroutine counts the number of goroutines created by this [Stub].
+	goroutine int
+	// sub stores the addresses of descendant [Stub] created by New.
+	sub []*Stub[K]
+	// wg waits for all descendants to complete.
+	wg *sync.WaitGroup
+}
+
+// New creates a root [Stub].
+func New[K any](tb testing.TB, makeK func(s *Stub[K]) K, want Expect) *Stub[K] {
+	return &Stub[K]{TB: tb, makeK: makeK, want: want, wg: new(sync.WaitGroup)}
+}
+
+func (s *Stub[K]) FailNow()                          { panic(panicFailNow) }
+func (s *Stub[K]) Fatal(args ...any)                 { s.Error(args...); panic(panicFatal) }
+func (s *Stub[K]) Fatalf(format string, args ...any) { s.Errorf(format, args...); panic(panicFatalf) }
+func (s *Stub[K]) SkipNow()                          { panic("invalid call to SkipNow") }
+func (s *Stub[K]) Skip(...any)                       { panic("invalid call to Skip") }
+func (s *Stub[K]) Skipf(string, ...any)              { panic("invalid call to Skipf") }
+
+// New calls f in a new goroutine
+func (s *Stub[K]) New(f func(k K)) {
+	s.Helper()
+
+	s.Expects("New")
+	if len(s.want.Tracks) <= s.goroutine {
+		s.Fatal("New: track overrun")
+	}
+	ds := &Stub[K]{TB: s.TB, makeK: s.makeK, want: s.want.Tracks[s.goroutine], wg: s.wg}
+	s.goroutine++
+	s.sub = append(s.sub, ds)
+	s.wg.Add(1)
+	go func() {
+		s.Helper()
+
+		defer s.wg.Done()
+		defer handleExitNew(s.TB)
+		f(s.makeK(ds))
+	}()
+}
+
+// Pos returns the current position of [Stub] in its [Expect.Calls]
+func (s *Stub[K]) Pos() int { return s.pos }
+
+// Len returns the length of [Expect.Calls].
+func (s *Stub[K]) Len() int { return len(s.want.Calls) }
+
+// VisitIncomplete calls f on an incomplete s and all its descendants.
+func (s *Stub[K]) VisitIncomplete(f func(s *Stub[K])) {
+	s.Helper()
+	s.wg.Wait()
+
+	if s.want.Calls != nil && len(s.want.Calls) != s.pos {
+		f(s)
+	}
+	for _, ds := range s.sub {
+		ds.VisitIncomplete(f)
+	}
+}
+
+// Expects checks the name of and returns the current [Call] and advances pos.
+func (s *Stub[K]) Expects(name string) (expect *Call) {
+	s.Helper()
+
+	if len(s.want.Calls) == s.pos {
+		s.Fatal("Expects: advancing beyond expected calls")
+	}
+	expect = &s.want.Calls[s.pos]
+	if name != expect.Name {
+		if expect.Name == CallSeparator {
+			s.Fatalf("Expects: func = %s, separator overrun", name)
+		}
+		if name == CallSeparator {
+			s.Fatalf("Expects: separator, want %s", expect.Name)
+		}
+		s.Fatalf("Expects: func = %s, want %s", name, expect.Name)
+	}
+	s.pos++
+	return
+}
+
+// CheckArg checks an argument comparable with the == operator. Avoid using this with pointers.
+func CheckArg[T comparable, K any](s *Stub[K], arg string, got T, n int) bool {
+	s.Helper()
+
+	pos := s.pos - 1
+	if pos < 0 || pos >= len(s.want.Calls) {
+		panic("invalid call to CheckArg")
+	}
+	expect := s.want.Calls[pos]
+	want, ok := expect.Args[n].(T)
+	if !ok || got != want {
+		s.Errorf("%s: %s = %#v, want %#v (%d)", expect.Name, arg, got, want, pos)
+		return false
+	}
+	return true
+}
+
+// CheckArgReflect checks an argument of any type.
+func CheckArgReflect[K any](s *Stub[K], arg string, got any, n int) bool {
+	s.Helper()
+
+	pos := s.pos - 1
+	if pos < 0 || pos >= len(s.want.Calls) {
+		panic("invalid call to CheckArgReflect")
+	}
+	expect := s.want.Calls[pos]
+	want := expect.Args[n]
+	if !reflect.DeepEqual(got, want) {
+		s.Errorf("%s: %s = %#v, want %#v (%d)", expect.Name, arg, got, want, pos)
+		return false
+	}
+	return true
+}

container/stub/stub_test.go

@@ -0,0 +1,296 @@
+package stub
+
+import (
+	"reflect"
+	"sync/atomic"
+	"testing"
+)
+
+// stubHolder embeds [Stub].
+type stubHolder struct{ *Stub[stubHolder] }
+
+// overrideT allows some methods of [testing.T] to be overridden.
+type overrideT struct {
+	*testing.T
+
+	error  atomic.Pointer[func(args ...any)]
+	errorf atomic.Pointer[func(format string, args ...any)]
+}
+
+func (t *overrideT) Error(args ...any) {
+	fp := t.error.Load()
+	if fp == nil || *fp == nil {
+		t.T.Error(args...)
+		return
+	}
+	(*fp)(args...)
+}
+
+func (t *overrideT) Errorf(format string, args ...any) {
+	fp := t.errorf.Load()
+	if fp == nil || *fp == nil {
+		t.T.Errorf(format, args...)
+		return
+	}
+	(*fp)(format, args...)
+}
+
+func TestStub(t *testing.T) {
+	t.Run("goexit", func(t *testing.T) {
+		t.Run("FailNow", func(t *testing.T) {
+			defer func() {
+				if r := recover(); r != panicFailNow {
+					t.Errorf("recover: %v", r)
+				}
+			}()
+			new(stubHolder).FailNow()
+		})
+
+		t.Run("SkipNow", func(t *testing.T) {
+			defer func() {
+				want := "invalid call to SkipNow"
+				if r := recover(); r != want {
+					t.Errorf("recover: %v, want %v", r, want)
+				}
+			}()
+			new(stubHolder).SkipNow()
+		})
+
+		t.Run("Skip", func(t *testing.T) {
+			defer func() {
+				want := "invalid call to Skip"
+				if r := recover(); r != want {
+					t.Errorf("recover: %v, want %v", r, want)
+				}
+			}()
+			new(stubHolder).Skip()
+		})
+
+		t.Run("Skipf", func(t *testing.T) {
+			defer func() {
+				want := "invalid call to Skipf"
+				if r := recover(); r != want {
+					t.Errorf("recover: %v, want %v", r, want)
+				}
+			}()
+			new(stubHolder).Skipf("")
+		})
+	})
+
+	t.Run("new", func(t *testing.T) {
+		t.Run("success", func(t *testing.T) {
+			s := New(t, func(s *Stub[stubHolder]) stubHolder { return stubHolder{s} }, Expect{Calls: []Call{
+				{"New", ExpectArgs{}, nil, nil},
+			}, Tracks: []Expect{{Calls: []Call{
+				{"done", ExpectArgs{0xbabe}, nil, nil},
+			}}}})
+
+			s.New(func(k stubHolder) {
+				expect := k.Expects("done")
+				if expect.Name != "done" {
+					t.Errorf("New: Name = %s, want done", expect.Name)
+				}
+				if expect.Args != (ExpectArgs{0xbabe}) {
+					t.Errorf("New: Args = %#v", expect.Args)
+				}
+				if expect.Ret != nil {
+					t.Errorf("New: Ret = %#v", expect.Ret)
+				}
+				if expect.Err != nil {
+					t.Errorf("New: Err = %#v", expect.Err)
+				}
+			})
+
+			if pos := s.Pos(); pos != 1 {
+				t.Errorf("Pos: %d, want 1", pos)
+			}
+			if l := s.Len(); l != 1 {
+				t.Errorf("Len: %d, want 1", l)
+			}
+
+			s.VisitIncomplete(func(s *Stub[stubHolder]) { panic("unreachable") })
+		})
+
+		t.Run("overrun", func(t *testing.T) {
+			ot := &overrideT{T: t}
+			ot.error.Store(checkError(t, "New: track overrun"))
+			s := New(ot, func(s *Stub[stubHolder]) stubHolder { return stubHolder{s} }, Expect{Calls: []Call{
+				{"New", ExpectArgs{}, nil, nil},
+				{"panic", ExpectArgs{"unreachable"}, nil, nil},
+			}})
+			func() { defer HandleExit(t); s.New(func(k stubHolder) { panic("unreachable") }) }()
+
+			var visit int
+			s.VisitIncomplete(func(s *Stub[stubHolder]) {
+				visit++
+				if visit > 1 {
+					panic("unexpected visit count")
+				}
+
+				want := Call{"panic", ExpectArgs{"unreachable"}, nil, nil}
+				if got := s.want.Calls[s.pos]; !reflect.DeepEqual(got, want) {
+					t.Errorf("VisitIncomplete: %#v, want %#v", got, want)
+				}
+			})
+		})
+
+		t.Run("expects", func(t *testing.T) {
+			t.Run("overrun", func(t *testing.T) {
+				ot := &overrideT{T: t}
+				ot.error.Store(checkError(t, "Expects: advancing beyond expected calls"))
+				s := New(ot, func(s *Stub[stubHolder]) stubHolder { return stubHolder{s} }, Expect{})
+				func() { defer HandleExit(t); s.Expects("unreachable") }()
+			})
+
+			t.Run("separator", func(t *testing.T) {
+				t.Run("overrun", func(t *testing.T) {
+					ot := &overrideT{T: t}
+					ot.errorf.Store(checkErrorf(t, "Expects: func = %s, separator overrun", "meow"))
+					s := New(ot, func(s *Stub[stubHolder]) stubHolder { return stubHolder{s} }, Expect{Calls: []Call{
+						{CallSeparator, ExpectArgs{}, nil, nil},
+					}})
+					func() { defer HandleExit(t); s.Expects("meow") }()
+				})
+
+				t.Run("mismatch", func(t *testing.T) {
+					ot := &overrideT{T: t}
+					ot.errorf.Store(checkErrorf(t, "Expects: separator, want %s", "panic"))
+					s := New(ot, func(s *Stub[stubHolder]) stubHolder { return stubHolder{s} }, Expect{Calls: []Call{
+						{"panic", ExpectArgs{}, nil, nil},
+					}})
+					func() { defer HandleExit(t); s.Expects(CallSeparator) }()
+				})
+			})
+
+			t.Run("mismatch", func(t *testing.T) {
+				ot := &overrideT{T: t}
+				ot.errorf.Store(checkErrorf(t, "Expects: func = %s, want %s", "meow", "nya"))
+				s := New(ot, func(s *Stub[stubHolder]) stubHolder { return stubHolder{s} }, Expect{Calls: []Call{
+					{"nya", ExpectArgs{}, nil, nil},
+				}})
+				func() { defer HandleExit(t); s.Expects("meow") }()
+			})
+		})
+	})
+}
+
+func TestCheckArg(t *testing.T) {
+	t.Run("oob negative", func(t *testing.T) {
+		defer func() {
+			want := "invalid call to CheckArg"
+			if r := recover(); r != want {
+				t.Errorf("recover: %v, want %v", r, want)
+			}
+		}()
+		s := New(t, func(s *Stub[stubHolder]) stubHolder { return stubHolder{s} }, Expect{})
+		CheckArg(s, "unreachable", struct{}{}, 0)
+	})
+
+	ot := &overrideT{T: t}
+	s := New(ot, func(s *Stub[stubHolder]) stubHolder { return stubHolder{s} }, Expect{Calls: []Call{
+		{"panic", ExpectArgs{PanicExit}, nil, nil},
+		{"meow", ExpectArgs{-1}, nil, nil},
+	}})
+	t.Run("match", func(t *testing.T) {
+		s.Expects("panic")
+		if !CheckArg(s, "v", PanicExit, 0) {
+			t.Errorf("CheckArg: unexpected false")
+		}
+	})
+	t.Run("mismatch", func(t *testing.T) {
+		defer HandleExit(t)
+		s.Expects("meow")
+		ot.errorf.Store(checkErrorf(t, "%s: %s = %#v, want %#v (%d)", "meow", "time", 0, -1, 1))
+		if CheckArg(s, "time", 0, 0) {
+			t.Errorf("CheckArg: unexpected true")
+		}
+	})
+	t.Run("oob", func(t *testing.T) {
+		s.pos++
+		defer func() {
+			want := "invalid call to CheckArg"
+			if r := recover(); r != want {
+				t.Errorf("recover: %v, want %v", r, want)
+			}
+		}()
+		CheckArg(s, "unreachable", struct{}{}, 0)
+	})
+}
+
+func TestCheckArgReflect(t *testing.T) {
+	t.Run("oob lower", func(t *testing.T) {
+		defer func() {
+			want := "invalid call to CheckArgReflect"
+			if r := recover(); r != want {
+				t.Errorf("recover: %v, want %v", r, want)
+			}
+		}()
+		s := New(t, func(s *Stub[stubHolder]) stubHolder { return stubHolder{s} }, Expect{})
+		CheckArgReflect(s, "unreachable", struct{}{}, 0)
+	})
+
+	ot := &overrideT{T: t}
+	s := New(ot, func(s *Stub[stubHolder]) stubHolder { return stubHolder{s} }, Expect{Calls: []Call{
+		{"panic", ExpectArgs{PanicExit}, nil, nil},
+		{"meow", ExpectArgs{-1}, nil, nil},
+	}})
+	t.Run("match", func(t *testing.T) {
+		s.Expects("panic")
+		if !CheckArgReflect(s, "v", PanicExit, 0) {
+			t.Errorf("CheckArgReflect: unexpected false")
+		}
+	})
+	t.Run("mismatch", func(t *testing.T) {
+		defer HandleExit(t)
+		s.Expects("meow")
+		ot.errorf.Store(checkErrorf(t, "%s: %s = %#v, want %#v (%d)", "meow", "time", 0, -1, 1))
+		if CheckArgReflect(s, "time", 0, 0) {
+			t.Errorf("CheckArgReflect: unexpected true")
+		}
+	})
+	t.Run("oob", func(t *testing.T) {
+		s.pos++
+		defer func() {
+			want := "invalid call to CheckArgReflect"
+			if r := recover(); r != want {
+				t.Errorf("recover: %v, want %v", r, want)
+			}
+		}()
+		CheckArgReflect(s, "unreachable", struct{}{}, 0)
+	})
+}
+
+func checkError(t *testing.T, wantArgs ...any) *func(args ...any) {
+	var called bool
+	f := func(args ...any) {
+		if called {
+			panic("invalid call to error")
+		}
+		called = true
+
+		if !reflect.DeepEqual(args, wantArgs) {
+			t.Errorf("Error: %#v, want %#v", args, wantArgs)
+		}
+		panic(PanicExit)
+	}
+	return &f
+}
+
+func checkErrorf(t *testing.T, wantFormat string, wantArgs ...any) *func(format string, args ...any) {
+	var called bool
+	f := func(format string, args ...any) {
+		if called {
+			panic("invalid call to errorf")
+		}
+		called = true
+
+		if format != wantFormat {
+			t.Errorf("Errorf: format = %q, want %q", format, wantFormat)
+		}
+		if !reflect.DeepEqual(args, wantArgs) {
+			t.Errorf("Errorf: args = %#v, want %#v", args, wantArgs)
+		}
+		panic(PanicExit)
+	}
+	return &f
+}

container/vfs/mountinfo.go

@@ -24,6 +24,32 @@ var (
 	ErrMountInfoSep    = errors.New("bad optional fields separator")
 )
 
+type DecoderError struct {
+	Op   string
+	Line int
+	Err  error
+}
+
+func (e *DecoderError) Unwrap() error { return e.Err }
+func (e *DecoderError) Error() string {
+	var s string
+
+	var numError *strconv.NumError
+	switch {
+	case errors.As(e.Err, &numError) && numError != nil:
+		s = "numeric field " + strconv.Quote(numError.Num) + " " + numError.Err.Error()
+
+	default:
+		s = e.Err.Error()
+	}
+
+	var atLine string
+	if e.Line >= 0 {
+		atLine = " at line " + strconv.Itoa(e.Line)
+	}
+	return e.Op + " mountinfo" + atLine + ": " + s
+}
+
 type (
 	// A MountInfoDecoder reads and decodes proc_pid_mountinfo(5) entries from an input stream.
 	MountInfoDecoder struct {
@@ -32,6 +58,7 @@ type (
 
 		current  *MountInfo
 		parseErr error
+		curLine  int
 		complete bool
 	}
 
@@ -132,9 +159,12 @@ func (d *MountInfoDecoder) Entries() iter.Seq[*MountInfoEntry] {
 
 func (d *MountInfoDecoder) Err() error {
 	if err := d.s.Err(); err != nil {
-		return err
+		return &DecoderError{"scan", d.curLine, err}
 	}
-	return d.parseErr
+	if d.parseErr != nil {
+		return &DecoderError{"parse", d.curLine, d.parseErr}
+	}
+	return nil
 }
 
 func (d *MountInfoDecoder) scan() bool {
@@ -160,6 +190,7 @@ func (d *MountInfoDecoder) scan() bool {
 		d.current.Next = m
 		d.current = d.current.Next
 	}
+	d.curLine++
 	return true
 }
 

container/vfs/mountinfo_test.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"errors"
 	"iter"
+	"os"
 	"path"
 	"reflect"
 	"slices"
@@ -15,62 +16,102 @@ import (
 	"hakurei.app/container/vfs"
 )
 
+func TestDecoderError(t *testing.T) {
+	testCases := []struct {
+		name    string
+		err     *vfs.DecoderError
+		want    string
+		target  error
+		targetF error
+	}{
+		{"errno", &vfs.DecoderError{Op: "parse", Line: 0xdeadbeef, Err: syscall.ENOTRECOVERABLE},
+			"parse mountinfo at line 3735928559: state not recoverable", syscall.ENOTRECOVERABLE, syscall.EROFS},
+
+		{"strconv", &vfs.DecoderError{Op: "parse", Line: 0xdeadbeef, Err: &strconv.NumError{Func: "Atoi", Num: "meow", Err: strconv.ErrSyntax}},
+			`parse mountinfo at line 3735928559: numeric field "meow" invalid syntax`, strconv.ErrSyntax, os.ErrInvalid},
+
+		{"unfold", &vfs.DecoderError{Op: "unfold", Line: -1, Err: vfs.UnfoldTargetError("/proc/nonexistent")},
+			"unfold mountinfo: mount point /proc/nonexistent never appeared in mountinfo", vfs.UnfoldTargetError("/proc/nonexistent"), os.ErrNotExist},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Run("error", func(t *testing.T) {
+				if got := tc.err.Error(); got != tc.want {
+					t.Errorf("Error: %s, want %s", got, tc.want)
+				}
+			})
+
+			t.Run("is", func(t *testing.T) {
+				if !errors.Is(tc.err, tc.target) {
+					t.Errorf("Is: unexpected false")
+				}
+				if errors.Is(tc.err, tc.targetF) {
+					t.Errorf("Is: unexpected true")
+				}
+			})
+		})
+	}
+}
+
 func TestMountInfo(t *testing.T) {
 	testCases := []mountInfoTest{
 		{"count", sampleMountinfoBase + `
 21 20 0:53/ /mnt/test rw,relatime - tmpfs  rw
 21 16 0:17 / /sys/fs/cgroup rw,nosuid,nodev,noexec,relatime - tmpfs tmpfs rw,mode=755`,
-			vfs.ErrMountInfoFields, "", nil, nil, nil},
+			&vfs.DecoderError{Op: "parse", Line: 6, Err: vfs.ErrMountInfoFields},
+			"", nil, nil, nil},
 
 		{"sep", sampleMountinfoBase + `
 21 20 0:53 / /mnt/test rw,relatime shared:212 _ tmpfs  rw
 21 16 0:17 / /sys/fs/cgroup rw,nosuid,nodev,noexec,relatime - tmpfs tmpfs rw,mode=755`,
-			vfs.ErrMountInfoSep, "", nil, nil, nil},
+			&vfs.DecoderError{Op: "parse", Line: 6, Err: vfs.ErrMountInfoSep},
+			"", nil, nil, nil},
 
 		{"id", sampleMountinfoBase + `
 id 20 0:53 / /mnt/test rw,relatime shared:212 - tmpfs  rw
 21 16 0:17 / /sys/fs/cgroup rw,nosuid,nodev,noexec,relatime - tmpfs tmpfs rw,mode=755`,
-			strconv.ErrSyntax, "", nil, nil, nil},
+			&vfs.DecoderError{Op: "parse", Line: 6, Err: &strconv.NumError{Func: "Atoi", Num: "id", Err: strconv.ErrSyntax}},
+			"", nil, nil, nil},
 
 		{"parent", sampleMountinfoBase + `
 21 parent 0:53 / /mnt/test rw,relatime shared:212 - tmpfs  rw
 21 16 0:17 / /sys/fs/cgroup rw,nosuid,nodev,noexec,relatime - tmpfs tmpfs rw,mode=755`,
-			strconv.ErrSyntax, "", nil, nil, nil},
+			&vfs.DecoderError{Op: "parse", Line: 6, Err: &strconv.NumError{Func: "Atoi", Num: "parent", Err: strconv.ErrSyntax}}, "", nil, nil, nil},
 
 		{"devno", sampleMountinfoBase + `
 21 20 053 / /mnt/test rw,relatime shared:212 - tmpfs  rw
 21 16 0:17 / /sys/fs/cgroup rw,nosuid,nodev,noexec,relatime - tmpfs tmpfs rw,mode=755`,
-			nil, "unexpected EOF", nil, nil, nil},
+			nil, "parse mountinfo at line 6: unexpected EOF", nil, nil, nil},
 
 		{"maj", sampleMountinfoBase + `
 21 20 maj:53 / /mnt/test rw,relatime shared:212 - tmpfs  rw
 21 16 0:17 / /sys/fs/cgroup rw,nosuid,nodev,noexec,relatime - tmpfs tmpfs rw,mode=755`,
-			nil, "expected integer", nil, nil, nil},
+			nil, "parse mountinfo at line 6: expected integer", nil, nil, nil},
 
 		{"min", sampleMountinfoBase + `
 21 20 0:min / /mnt/test rw,relatime shared:212 - tmpfs  rw
 21 16 0:17 / /sys/fs/cgroup rw,nosuid,nodev,noexec,relatime - tmpfs tmpfs rw,mode=755`,
-			nil, "expected integer", nil, nil, nil},
+			nil, "parse mountinfo at line 6: expected integer", nil, nil, nil},
 
 		{"mountroot", sampleMountinfoBase + `
 21 20 0:53  /mnt/test rw,relatime - tmpfs  rw
 21 16 0:17 / /sys/fs/cgroup rw,nosuid,nodev,noexec,relatime - tmpfs tmpfs rw,mode=755`,
-			vfs.ErrMountInfoEmpty, "", nil, nil, nil},
+			&vfs.DecoderError{Op: "parse", Line: 6, Err: vfs.ErrMountInfoEmpty}, "", nil, nil, nil},
 
 		{"target", sampleMountinfoBase + `
 21 20 0:53 /  rw,relatime - tmpfs  rw
 21 16 0:17 / /sys/fs/cgroup rw,nosuid,nodev,noexec,relatime - tmpfs tmpfs rw,mode=755`,
-			vfs.ErrMountInfoEmpty, "", nil, nil, nil},
+			&vfs.DecoderError{Op: "parse", Line: 6, Err: vfs.ErrMountInfoEmpty}, "", nil, nil, nil},
 
 		{"vfs options", sampleMountinfoBase + `
 21 20 0:53 / /mnt/test  - tmpfs  rw
 21 16 0:17 / /sys/fs/cgroup rw,nosuid,nodev,noexec,relatime - tmpfs tmpfs rw,mode=755`,
-			vfs.ErrMountInfoEmpty, "", nil, nil, nil},
+			&vfs.DecoderError{Op: "parse", Line: 6, Err: vfs.ErrMountInfoEmpty}, "", nil, nil, nil},
 
 		{"FS type", sampleMountinfoBase + `
-21 20 0:53 / /mnt/test rw,relatime -   rw
+21 16 0:17 / /sys/fs/cgroup rw,nosuid,nodev,noexec,relatime - tmpfs tmpfs rw,mode=755
-21 16 0:17 / /sys/fs/cgroup rw,nosuid,nodev,noexec,relatime - tmpfs tmpfs rw,mode=755`,
+21 20 0:53 / /mnt/test rw,relatime -   rw`,
-			vfs.ErrMountInfoEmpty, "", nil, nil, nil},
+			&vfs.DecoderError{Op: "parse", Line: 7, Err: vfs.ErrMountInfoEmpty}, "", nil, nil, nil},
 
 		{"base", sampleMountinfoBase, nil, "", []*wantMountInfo{
 			m(15, 20, 0, 3, "/", "/proc", "rw,relatime", o(), "proc", "/proc", "rw", syscall.MS_RELATIME, nil),
@@ -266,9 +307,9 @@ func (tc *mountInfoTest) check(t *testing.T, d *vfs.MountInfoDecoder, funcName s
 		})
 	} else if tc.wantNode != nil || tc.wantCollectF != nil {
 		panic("invalid test case")
-	} else if _, err := d.Unfold("/"); !errors.Is(err, tc.wantErr) {
+	} else if _, err := d.Unfold("/"); !reflect.DeepEqual(err, tc.wantErr) {
 		if tc.wantError == "" {
-			t.Errorf("Unfold: error = %v, wantErr %v",
+			t.Errorf("Unfold: error = %#v, wantErr %#v",
 				err, tc.wantErr)
 		} else if err != nil && err.Error() != tc.wantError {
 			t.Errorf("Unfold: error = %q, wantError %q",
@@ -276,9 +317,9 @@ func (tc *mountInfoTest) check(t *testing.T, d *vfs.MountInfoDecoder, funcName s
 		}
 	}
 
-	if err := gotErr(); !errors.Is(err, tc.wantErr) {
+	if err := gotErr(); !reflect.DeepEqual(err, tc.wantErr) {
 		if tc.wantError == "" {
-			t.Errorf("%s: error = %v, wantErr %v",
+			t.Errorf("%s: error = %#v, wantErr %#v",
 				funcName, err, tc.wantErr)
 		} else if err != nil && err.Error() != tc.wantError {
 			t.Errorf("%s: error = %q, wantError %q",

container/vfs/unfold.go

@@ -4,9 +4,14 @@ import (
 	"iter"
 	"path"
 	"strings"
-	"syscall"
 )
 
+type UnfoldTargetError string
+
+func (e UnfoldTargetError) Error() string {
+	return "mount point " + string(e) + " never appeared in mountinfo"
+}
+
 // MountInfoNode positions a [MountInfoEntry] in its mount hierarchy.
 type MountInfoNode struct {
 	*MountInfoEntry
@@ -65,7 +70,8 @@ func (d *MountInfoDecoder) Unfold(target string) (*MountInfoNode, error) {
 	}
 
 	if targetIndex == -1 {
-		return nil, syscall.ESTALE
+		// target does not exist in parsed mountinfo
+		return nil, &DecoderError{Op: "unfold", Line: -1, Err: UnfoldTargetError(targetClean)}
 	}
 
 	for _, cur := range mountinfo {

container/vfs/unfold_test.go

@@ -1,11 +1,9 @@
 package vfs_test
 
 import (
-	"errors"
 	"reflect"
 	"slices"
 	"strings"
-	"syscall"
 	"testing"
 
 	"hakurei.app/container/vfs"
@@ -26,7 +24,7 @@ func TestUnfold(t *testing.T) {
 			"no match",
 			sampleMountinfoBase,
 			"/mnt",
-			syscall.ESTALE, nil, nil, nil,
+			&vfs.DecoderError{Op: "unfold", Line: -1, Err: vfs.UnfoldTargetError("/mnt")}, nil, nil, nil,
 		},
 		{
 			"cover",
@@ -55,7 +53,7 @@ func TestUnfold(t *testing.T) {
 			d := vfs.NewMountInfoDecoder(strings.NewReader(tc.sample))
 			got, err := d.Unfold(tc.target)
 
-			if !errors.Is(err, tc.wantErr) {
+			if !reflect.DeepEqual(err, tc.wantErr) {
 				t.Errorf("Unfold: error = %v, wantErr %v",
 					err, tc.wantErr)
 			}

flake.lock

@@ -7,11 +7,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1753479839,
+        "lastModified": 1756679287,
-        "narHash": "sha256-E/rPVh7vyPMJUFl2NAew+zibNGfVbANr8BP8nLRbLkQ=",
+        "narHash": "sha256-Xd1vOeY9ccDf5VtVK12yM0FS6qqvfUop8UQlxEB+gTQ=",
         "owner": "nix-community",
         "repo": "home-manager",
-        "rev": "0b9bf983db4d064764084cd6748efb1ab8297d1e",
+        "rev": "07fc025fe10487dd80f2ec694f1cd790e752d0e8",
         "type": "github"
       },
       "original": {
@@ -23,11 +23,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1753345091,
+        "lastModified": 1757020766,
-        "narHash": "sha256-CdX2Rtvp5I8HGu9swBmYuq+ILwRxpXdJwlpg8jvN4tU=",
+        "narHash": "sha256-PLoSjHRa2bUbi1x9HoXgTx2AiuzNXs54c8omhadyvp0=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "3ff0e34b1383648053bba8ed03f201d3466f90c9",
+        "rev": "fe83bbdde2ccdc2cb9573aa846abe8363f79a97a",
         "type": "github"
       },
       "original": {

helper/container_test.go

@@ -11,10 +11,10 @@ import (
 )
 
 func TestContainer(t *testing.T) {
-	t.Run("start empty container", func(t *testing.T) {
+	t.Run("start invalid container", func(t *testing.T) {
 		h := helper.New(t.Context(), container.MustAbs(container.Nonexistent), "hakurei", argsWt, false, argF, nil, nil)
 
-		wantErr := "container: starting an empty container"
+		wantErr := "container: starting an invalid container"
 		if err := h.Start(); err == nil || err.Error() != wantErr {
 			t.Errorf("Start: error = %v, wantErr %q",
 				err, wantErr)

helper/helper_test.go

@@ -6,8 +6,10 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"reflect"
 	"strconv"
 	"strings"
+	"syscall"
 	"testing"
 	"time"
 
@@ -47,6 +49,10 @@ func argFChecked(argsFd, statFd int) (args []string) {
 	return
 }
 
+const (
+	containerTimeout = 30 * time.Second
+)
+
 // this function tests an implementation of the helper.Helper interface
 func testHelper(t *testing.T, createHelper func(ctx context.Context, setOutput func(stdoutP, stderrP *io.Writer), stat bool) helper.Helper) {
 	oldWaitDelay := helper.WaitDelay
@@ -54,18 +60,15 @@ func testHelper(t *testing.T, createHelper func(ctx context.Context, setOutput f
 	t.Cleanup(func() { helper.WaitDelay = oldWaitDelay })
 
 	t.Run("start helper with status channel and wait", func(t *testing.T) {
-		ctx, cancel := context.WithTimeout(t.Context(), 5*time.Second)
+		ctx, cancel := context.WithTimeout(t.Context(), containerTimeout)
 		stdout := new(strings.Builder)
 		h := createHelper(ctx, func(stdoutP, stderrP *io.Writer) { *stdoutP, *stderrP = stdout, os.Stderr }, true)
 
 		t.Run("wait not yet started helper", func(t *testing.T) {
-			defer func() {
+			if err := h.Wait(); !reflect.DeepEqual(err, syscall.EINVAL) &&
-				r := recover()
+				!reflect.DeepEqual(err, errors.New("exec: not started")) {
-				if r == nil {
+				t.Errorf("Wait: error = %v", err)
-					t.Fatalf("Wait did not panic")
+			}
-				}
-			}()
-			panic(fmt.Sprintf("unreachable: %v", h.Wait()))
 		})
 
 		t.Log("starting helper stub")
@@ -108,7 +111,7 @@ func testHelper(t *testing.T, createHelper func(ctx context.Context, setOutput f
 	})
 
 	t.Run("start helper and wait", func(t *testing.T) {
-		ctx, cancel := context.WithTimeout(t.Context(), 5*time.Second)
+		ctx, cancel := context.WithTimeout(t.Context(), containerTimeout)
 		defer cancel()
 		stdout := new(strings.Builder)
 		h := createHelper(ctx, func(stdoutP, stderrP *io.Writer) { *stdoutP, *stderrP = stdout, os.Stderr }, false)

hst/config.go

@@ -87,7 +87,9 @@ type (
 
 		// initial process environment variables
 		Env map[string]string `json:"env"`
-		// map target user uid to privileged user uid in the user namespace
+		// map target user uid to privileged user uid in the user namespace;
+		// some programs fail to connect to dbus session running as a different uid,
+		// this option works around it by mapping priv-side caller uid in container
 		MapRealUID bool `json:"map_real_uid"`
 
 		// pass through all devices

hst/hst.go

@@ -2,12 +2,42 @@
 package hst
 
 import (
+	"errors"
+	"net"
+	"os"
+
 	"hakurei.app/container"
 	"hakurei.app/container/seccomp"
 	"hakurei.app/system"
 	"hakurei.app/system/dbus"
 )
 
+// An AppError is returned while starting an app according to [hst.Config].
+type AppError struct {
+	Step string
+	Err  error
+	Msg  string
+}
+
+func (e *AppError) Error() string { return e.Err.Error() }
+func (e *AppError) Unwrap() error { return e.Err }
+func (e *AppError) Message() string {
+	if e.Msg != "" {
+		return e.Msg
+	}
+
+	switch {
+	case errors.As(e.Err, new(*os.PathError)),
+		errors.As(e.Err, new(*os.LinkError)),
+		errors.As(e.Err, new(*os.SyscallError)),
+		errors.As(e.Err, new(*net.OpError)):
+		return "cannot " + e.Error()
+
+	default:
+		return "cannot " + e.Step + ": " + e.Error()
+	}
+}
+
 // Paths contains environment-dependent paths used by hakurei.
 type Paths struct {
 	// temporary directory returned by [os.TempDir] (usually `/tmp`)

hst/hst_test.go

@@ -2,11 +2,93 @@ package hst_test
 
 import (
 	"encoding/json"
+	"errors"
+	"net"
+	"os"
+	"syscall"
 	"testing"
 
+	"hakurei.app/container"
+	"hakurei.app/container/stub"
 	"hakurei.app/hst"
 )
 
+func TestAppError(t *testing.T) {
+	testCases := []struct {
+		name    string
+		err     error
+		s       string
+		message string
+		is, isF error
+	}{
+		{"message", &hst.AppError{Step: "obtain uid from hsu", Err: stub.UniqueError(0),
+			Msg: "the setuid helper is missing: /run/wrappers/bin/hsu"},
+			"unique error 0 injected by the test suite",
+			"the setuid helper is missing: /run/wrappers/bin/hsu",
+			stub.UniqueError(0), os.ErrNotExist},
+
+		{"os.PathError", &hst.AppError{Step: "passthrough os.PathError",
+			Err: &os.PathError{Op: "stat", Path: "/proc/nonexistent", Err: os.ErrNotExist}},
+			"stat /proc/nonexistent: file does not exist",
+			"cannot stat /proc/nonexistent: file does not exist",
+			os.ErrNotExist, stub.UniqueError(0xdeadbeef)},
+
+		{"os.LinkError", &hst.AppError{Step: "passthrough os.LinkError",
+			Err: &os.LinkError{Op: "link", Old: "/proc/self", New: "/proc/nonexistent", Err: os.ErrNotExist}},
+			"link /proc/self /proc/nonexistent: file does not exist",
+			"cannot link /proc/self /proc/nonexistent: file does not exist",
+			os.ErrNotExist, stub.UniqueError(0xdeadbeef)},
+
+		{"os.SyscallError", &hst.AppError{Step: "passthrough os.SyscallError",
+			Err: &os.SyscallError{Syscall: "meow", Err: syscall.ENOSYS}},
+			"meow: function not implemented",
+			"cannot meow: function not implemented",
+			syscall.ENOSYS, syscall.ENOTRECOVERABLE},
+
+		{"net.OpError", &hst.AppError{Step: "passthrough net.OpError",
+			Err: &net.OpError{Op: "dial", Net: "cat", Err: net.UnknownNetworkError("cat")}},
+			"dial cat: unknown network cat",
+			"cannot dial cat: unknown network cat",
+			net.UnknownNetworkError("cat"), syscall.ENOTRECOVERABLE},
+
+		{"default", &hst.AppError{Step: "initialise container configuration", Err: stub.UniqueError(1)},
+			"unique error 1 injected by the test suite",
+			"cannot initialise container configuration: unique error 1 injected by the test suite",
+			stub.UniqueError(1), os.ErrInvalid},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Run("error", func(t *testing.T) {
+				if got := tc.err.Error(); got != tc.s {
+					t.Errorf("Error: %s, want %s", got, tc.s)
+				}
+			})
+
+			t.Run("message", func(t *testing.T) {
+				gotMessage, gotMessageOk := container.GetErrorMessage(tc.err)
+				if want := tc.message != "\x00"; gotMessageOk != want {
+					t.Errorf("GetErrorMessage: ok = %v, want %v", gotMessage, want)
+				}
+
+				if gotMessageOk {
+					if gotMessage != tc.message {
+						t.Errorf("GetErrorMessage: %s, want %s", gotMessage, tc.message)
+					}
+				}
+			})
+
+			t.Run("is", func(t *testing.T) {
+				if !errors.Is(tc.err, tc.is) {
+					t.Errorf("Is: unexpected false for %v", tc.is)
+				}
+				if errors.Is(tc.err, tc.isF) {
+					t.Errorf("Is: unexpected true for %v", tc.isF)
+				}
+			})
+		})
+	}
+}
+
 func TestTemplate(t *testing.T) {
 	const want = `{
 	"id": "org.chromium.Chromium",

internal/app/app.go

@@ -1,61 +1,28 @@
-// Package app defines the generic [App] interface.
+// Package app implements high-level hakurei container behaviour.
 package app
 
 import (
 	"context"
 	"log"
-	"syscall"
+	"os"
-	"time"
 
 	"hakurei.app/hst"
 	"hakurei.app/internal/app/state"
-	"hakurei.app/internal/sys"
 )
 
-type App interface {
+// Main runs an app according to [hst.Config] and terminates. Main does not return.
-	// ID returns a copy of [ID] held by App.
+func Main(ctx context.Context, config *hst.Config) {
-	ID() state.ID
+	var id state.ID
-
+	if err := state.NewAppID(&id); err != nil {
-	// Seal determines the outcome of config as a [SealedApp].
+		log.Fatal(err)
-	// The value of config might be overwritten and must not be used again.
-	Seal(config *hst.Config) (SealedApp, error)
-
-	String() string
-}
-
-type SealedApp interface {
-	// Run commits sealed system setup and starts the app process.
-	Run(rs *RunState) error
-}
-
-// RunState stores the outcome of a call to [SealedApp.Run].
-type RunState struct {
-	// Time is the exact point in time where the process was created.
-	// Location must be set to UTC.
-	//
-	// Time is nil if no process was ever created.
-	Time *time.Time
-	// RevertErr is stored by the deferred revert call.
-	RevertErr error
-	// WaitErr is the generic error value created by the standard library.
-	WaitErr error
-
-	syscall.WaitStatus
-}
-
-// SetStart stores the current time in [RunState] once.
-func (rs *RunState) SetStart() {
-	if rs.Time != nil {
-		panic("attempted to store time twice")
 	}
-	now := time.Now().UTC()
-	rs.Time = &now
-}
 
-func MustNew(ctx context.Context, os sys.State) App {
+	seal := outcome{id: &stringPair[state.ID]{id, id.String()}, syscallDispatcher: direct{}}
-	a, err := New(ctx, os)
+	if err := seal.finalise(ctx, config); err != nil {
-	if err != nil {
+		printMessageError("cannot seal app:", err)
-		log.Fatalf("cannot create app: %v", err)
+		os.Exit(1)
 	}
-	return a
+
+	seal.main()
+	panic("unreachable")
 }

internal/app/app_linux.go

@@ -1,69 +0,0 @@
-package app
-
-import (
-	"context"
-	"fmt"
-	"sync"
-
-	"hakurei.app/hst"
-	"hakurei.app/internal/app/state"
-	"hakurei.app/internal/sys"
-)
-
-func New(ctx context.Context, os sys.State) (App, error) {
-	a := new(app)
-	a.sys = os
-	a.ctx = ctx
-
-	id := new(state.ID)
-	err := state.NewAppID(id)
-	a.id = newID(id)
-
-	return a, err
-}
-
-type app struct {
-	id  *stringPair[state.ID]
-	sys sys.State
-	ctx context.Context
-
-	*outcome
-	mu sync.RWMutex
-}
-
-func (a *app) ID() state.ID { a.mu.RLock(); defer a.mu.RUnlock(); return a.id.unwrap() }
-
-func (a *app) String() string {
-	if a == nil {
-		return "(invalid app)"
-	}
-
-	a.mu.RLock()
-	defer a.mu.RUnlock()
-
-	if a.outcome != nil {
-		if a.outcome.user.uid == nil {
-			return fmt.Sprintf("(sealed app %s with invalid uid)", a.id)
-		}
-		return fmt.Sprintf("(sealed app %s as uid %s)", a.id, a.outcome.user.uid)
-	}
-
-	return fmt.Sprintf("(unsealed app %s)", a.id)
-}
-
-func (a *app) Seal(config *hst.Config) (SealedApp, error) {
-	a.mu.Lock()
-	defer a.mu.Unlock()
-
-	if a.outcome != nil {
-		panic("app sealed twice")
-	}
-
-	seal := new(outcome)
-	seal.id = a.id
-	err := seal.finalise(a.ctx, a.sys, config)
-	if err == nil {
-		a.outcome = seal
-	}
-	return seal, err
-}

internal/app/app_linux_test.go

@@ -1,106 +0,0 @@
-package app_test
-
-import (
-	"encoding/json"
-	"io/fs"
-	"reflect"
-	"testing"
-	"time"
-
-	"hakurei.app/container"
-	"hakurei.app/hst"
-	"hakurei.app/internal/app"
-	"hakurei.app/internal/app/state"
-	"hakurei.app/internal/hlog"
-	"hakurei.app/internal/sys"
-	"hakurei.app/system"
-)
-
-type sealTestCase struct {
-	name          string
-	os            sys.State
-	config        *hst.Config
-	id            state.ID
-	wantSys       *system.I
-	wantContainer *container.Params
-}
-
-func TestApp(t *testing.T) {
-	testCases := append(testCasesPd, testCasesNixos...)
-
-	for _, tc := range testCases {
-		t.Run(tc.name, func(t *testing.T) {
-			a := app.NewWithID(tc.id, tc.os)
-			var (
-				gotSys       *system.I
-				gotContainer *container.Params
-			)
-			if !t.Run("seal", func(t *testing.T) {
-				if sa, err := a.Seal(tc.config); err != nil {
-					hlog.PrintBaseError(err, "got generic error:")
-					t.Errorf("Seal: error = %v", err)
-					return
-				} else {
-					gotSys, gotContainer = app.AppIParams(a, sa)
-				}
-			}) {
-				return
-			}
-
-			t.Run("compare sys", func(t *testing.T) {
-				if !gotSys.Equal(tc.wantSys) {
-					t.Errorf("Seal: sys = %#v, want %#v",
-						gotSys, tc.wantSys)
-				}
-			})
-
-			t.Run("compare params", func(t *testing.T) {
-				if !reflect.DeepEqual(gotContainer, tc.wantContainer) {
-					t.Errorf("seal: params =\n%s\n, want\n%s",
-						mustMarshal(gotContainer), mustMarshal(tc.wantContainer))
-				}
-			})
-		})
-	}
-}
-
-func mustMarshal(v any) string {
-	if b, err := json.Marshal(v); err != nil {
-		panic(err.Error())
-	} else {
-		return string(b)
-	}
-}
-
-func stubDirEntries(names ...string) (e []fs.DirEntry, err error) {
-	e = make([]fs.DirEntry, len(names))
-	for i, name := range names {
-		e[i] = stubDirEntryPath(name)
-	}
-	return
-}
-
-type stubDirEntryPath string
-
-func (p stubDirEntryPath) Name() string               { return string(p) }
-func (p stubDirEntryPath) IsDir() bool                { panic("attempted to call IsDir") }
-func (p stubDirEntryPath) Type() fs.FileMode          { panic("attempted to call Type") }
-func (p stubDirEntryPath) Info() (fs.FileInfo, error) { panic("attempted to call Info") }
-
-type stubFileInfoMode fs.FileMode
-
-func (s stubFileInfoMode) Name() string       { panic("attempted to call Name") }
-func (s stubFileInfoMode) Size() int64        { panic("attempted to call Size") }
-func (s stubFileInfoMode) Mode() fs.FileMode  { return fs.FileMode(s) }
-func (s stubFileInfoMode) ModTime() time.Time { panic("attempted to call ModTime") }
-func (s stubFileInfoMode) IsDir() bool        { panic("attempted to call IsDir") }
-func (s stubFileInfoMode) Sys() any           { panic("attempted to call Sys") }
-
-type stubFileInfoIsDir bool
-
-func (s stubFileInfoIsDir) Name() string       { panic("attempted to call Name") }
-func (s stubFileInfoIsDir) Size() int64        { panic("attempted to call Size") }
-func (s stubFileInfoIsDir) Mode() fs.FileMode  { panic("attempted to call Mode") }
-func (s stubFileInfoIsDir) ModTime() time.Time { panic("attempted to call ModTime") }
-func (s stubFileInfoIsDir) IsDir() bool        { return bool(s) }
-func (s stubFileInfoIsDir) Sys() any           { panic("attempted to call Sys") }

internal/app/app_nixos_linux_test.go

@@ -1,167 +0,0 @@
-package app_test
-
-import (
-	"syscall"
-
-	"hakurei.app/container"
-	"hakurei.app/container/seccomp"
-	"hakurei.app/hst"
-	"hakurei.app/internal/app/state"
-	"hakurei.app/system"
-	"hakurei.app/system/acl"
-	"hakurei.app/system/dbus"
-)
-
-func m(pathname string) *container.Absolute { return container.MustAbs(pathname) }
-func f(c hst.FilesystemConfig) hst.FilesystemConfigJSON {
-	return hst.FilesystemConfigJSON{FilesystemConfig: c}
-}
-
-var testCasesNixos = []sealTestCase{
-	{
-		"nixos chromium direct wayland", new(stubNixOS),
-		&hst.Config{
-			ID:          "org.chromium.Chromium",
-			Path:        m("/nix/store/yqivzpzzn7z5x0lq9hmbzygh45d8rhqd-chromium-start"),
-			Enablements: hst.NewEnablements(system.EWayland | system.EDBus | system.EPulse),
-			Shell:       m("/run/current-system/sw/bin/zsh"),
-
-			Container: &hst.ContainerConfig{
-				Userns: true, HostNet: true, MapRealUID: true, Env: nil,
-				Filesystem: []hst.FilesystemConfigJSON{
-					f(&hst.FSBind{Source: m("/bin")}),
-					f(&hst.FSBind{Source: m("/usr/bin/")}),
-					f(&hst.FSBind{Source: m("/nix/store")}),
-					f(&hst.FSBind{Source: m("/run/current-system")}),
-					f(&hst.FSBind{Source: m("/sys/block"), Optional: true}),
-					f(&hst.FSBind{Source: m("/sys/bus"), Optional: true}),
-					f(&hst.FSBind{Source: m("/sys/class"), Optional: true}),
-					f(&hst.FSBind{Source: m("/sys/dev"), Optional: true}),
-					f(&hst.FSBind{Source: m("/sys/devices"), Optional: true}),
-					f(&hst.FSBind{Source: m("/run/opengl-driver")}),
-					f(&hst.FSBind{Source: m("/dev/dri"), Device: true, Optional: true}),
-					f(&hst.FSBind{Source: m("/etc/"), Target: m("/etc/"), Special: true}),
-					f(&hst.FSBind{Source: m("/var/lib/persist/module/hakurei/0/1"), Write: true, Ensure: true}),
-				},
-			},
-			SystemBus: &dbus.Config{
-				Talk:   []string{"org.bluez", "org.freedesktop.Avahi", "org.freedesktop.UPower"},
-				Filter: true,
-			},
-			SessionBus: &dbus.Config{
-				Talk: []string{
-					"org.freedesktop.FileManager1", "org.freedesktop.Notifications",
-					"org.freedesktop.ScreenSaver", "org.freedesktop.secrets",
-					"org.kde.kwalletd5", "org.kde.kwalletd6",
-				},
-				Own: []string{
-					"org.chromium.Chromium.*",
-					"org.mpris.MediaPlayer2.org.chromium.Chromium.*",
-					"org.mpris.MediaPlayer2.chromium.*",
-				},
-				Call: map[string]string{}, Broadcast: map[string]string{},
-				Filter: true,
-			},
-			DirectWayland: true,
-
-			Username: "u0_a1",
-			Home:     m("/var/lib/persist/module/hakurei/0/1"),
-			Identity: 1, Groups: []string{},
-		},
-		state.ID{
-			0x8e, 0x2c, 0x76, 0xb0,
-			0x66, 0xda, 0xbe, 0x57,
-			0x4c, 0xf0, 0x73, 0xbd,
-			0xb4, 0x6e, 0xb5, 0xc1,
-		},
-		system.New(1000001).
-			Ensure("/tmp/hakurei.1971", 0711).
-			Ensure("/tmp/hakurei.1971/runtime", 0700).UpdatePermType(system.User, "/tmp/hakurei.1971/runtime", acl.Execute).
-			Ensure("/tmp/hakurei.1971/runtime/1", 0700).UpdatePermType(system.User, "/tmp/hakurei.1971/runtime/1", acl.Read, acl.Write, acl.Execute).
-			Ensure("/tmp/hakurei.1971/tmpdir", 0700).UpdatePermType(system.User, "/tmp/hakurei.1971/tmpdir", acl.Execute).
-			Ensure("/tmp/hakurei.1971/tmpdir/1", 01700).UpdatePermType(system.User, "/tmp/hakurei.1971/tmpdir/1", acl.Read, acl.Write, acl.Execute).
-			Ensure("/run/user/1971/hakurei", 0700).UpdatePermType(system.User, "/run/user/1971/hakurei", acl.Execute).
-			Ensure("/run/user/1971", 0700).UpdatePermType(system.User, "/run/user/1971", acl.Execute). // this is ordered as is because the previous Ensure only calls mkdir if XDG_RUNTIME_DIR is unset
-			UpdatePermType(system.EWayland, "/run/user/1971/wayland-0", acl.Read, acl.Write, acl.Execute).
-			Ephemeral(system.Process, "/run/user/1971/hakurei/8e2c76b066dabe574cf073bdb46eb5c1", 0700).UpdatePermType(system.Process, "/run/user/1971/hakurei/8e2c76b066dabe574cf073bdb46eb5c1", acl.Execute).
-			Link("/run/user/1971/pulse/native", "/run/user/1971/hakurei/8e2c76b066dabe574cf073bdb46eb5c1/pulse").
-			CopyFile(nil, "/home/ophestra/xdg/config/pulse/cookie", 256, 256).
-			Ephemeral(system.Process, "/tmp/hakurei.1971/8e2c76b066dabe574cf073bdb46eb5c1", 0711).
-			MustProxyDBus("/tmp/hakurei.1971/8e2c76b066dabe574cf073bdb46eb5c1/bus", &dbus.Config{
-				Talk: []string{
-					"org.freedesktop.FileManager1", "org.freedesktop.Notifications",
-					"org.freedesktop.ScreenSaver", "org.freedesktop.secrets",
-					"org.kde.kwalletd5", "org.kde.kwalletd6",
-				},
-				Own: []string{
-					"org.chromium.Chromium.*",
-					"org.mpris.MediaPlayer2.org.chromium.Chromium.*",
-					"org.mpris.MediaPlayer2.chromium.*",
-				},
-				Call: map[string]string{}, Broadcast: map[string]string{},
-				Filter: true,
-			}, "/tmp/hakurei.1971/8e2c76b066dabe574cf073bdb46eb5c1/system_bus_socket", &dbus.Config{
-				Talk: []string{
-					"org.bluez",
-					"org.freedesktop.Avahi",
-					"org.freedesktop.UPower",
-				},
-				Filter: true,
-			}).
-			UpdatePerm("/tmp/hakurei.1971/8e2c76b066dabe574cf073bdb46eb5c1/bus", acl.Read, acl.Write).
-			UpdatePerm("/tmp/hakurei.1971/8e2c76b066dabe574cf073bdb46eb5c1/system_bus_socket", acl.Read, acl.Write),
-		&container.Params{
-			Uid:  1971,
-			Gid:  100,
-			Dir:  m("/var/lib/persist/module/hakurei/0/1"),
-			Path: m("/nix/store/yqivzpzzn7z5x0lq9hmbzygh45d8rhqd-chromium-start"),
-			Args: []string{"/nix/store/yqivzpzzn7z5x0lq9hmbzygh45d8rhqd-chromium-start"},
-			Env: []string{
-				"DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1971/bus",
-				"DBUS_SYSTEM_BUS_ADDRESS=unix:path=/run/dbus/system_bus_socket",
-				"HOME=/var/lib/persist/module/hakurei/0/1",
-				"PULSE_COOKIE=" + hst.Tmp + "/pulse-cookie",
-				"PULSE_SERVER=unix:/run/user/1971/pulse/native",
-				"SHELL=/run/current-system/sw/bin/zsh",
-				"TERM=xterm-256color",
-				"USER=u0_a1",
-				"WAYLAND_DISPLAY=wayland-0",
-				"XDG_RUNTIME_DIR=/run/user/1971",
-				"XDG_SESSION_CLASS=user",
-				"XDG_SESSION_TYPE=tty",
-			},
-			Ops: new(container.Ops).
-				Proc(m("/proc/")).
-				Tmpfs(hst.AbsTmp, 4096, 0755).
-				DevWritable(m("/dev/"), true).
-				Bind(m("/bin"), m("/bin"), 0).
-				Bind(m("/usr/bin/"), m("/usr/bin/"), 0).
-				Bind(m("/nix/store"), m("/nix/store"), 0).
-				Bind(m("/run/current-system"), m("/run/current-system"), 0).
-				Bind(m("/sys/block"), m("/sys/block"), container.BindOptional).
-				Bind(m("/sys/bus"), m("/sys/bus"), container.BindOptional).
-				Bind(m("/sys/class"), m("/sys/class"), container.BindOptional).
-				Bind(m("/sys/dev"), m("/sys/dev"), container.BindOptional).
-				Bind(m("/sys/devices"), m("/sys/devices"), container.BindOptional).
-				Bind(m("/run/opengl-driver"), m("/run/opengl-driver"), 0).
-				Bind(m("/dev/dri"), m("/dev/dri"), container.BindDevice|container.BindWritable|container.BindOptional).
-				Etc(m("/etc/"), "8e2c76b066dabe574cf073bdb46eb5c1").
-				Bind(m("/var/lib/persist/module/hakurei/0/1"), m("/var/lib/persist/module/hakurei/0/1"), container.BindWritable|container.BindEnsure).
-				Remount(m("/dev/"), syscall.MS_RDONLY).
-				Tmpfs(m("/run/user/"), 4096, 0755).
-				Bind(m("/tmp/hakurei.1971/runtime/1"), m("/run/user/1971"), container.BindWritable).
-				Bind(m("/tmp/hakurei.1971/tmpdir/1"), m("/tmp/"), container.BindWritable).
-				Place(m("/etc/passwd"), []byte("u0_a1:x:1971:100:Hakurei:/var/lib/persist/module/hakurei/0/1:/run/current-system/sw/bin/zsh\n")).
-				Place(m("/etc/group"), []byte("hakurei:x:100:\n")).
-				Bind(m("/run/user/1971/wayland-0"), m("/run/user/1971/wayland-0"), 0).
-				Bind(m("/run/user/1971/hakurei/8e2c76b066dabe574cf073bdb46eb5c1/pulse"), m("/run/user/1971/pulse/native"), 0).
-				Place(m(hst.Tmp+"/pulse-cookie"), nil).
-				Bind(m("/tmp/hakurei.1971/8e2c76b066dabe574cf073bdb46eb5c1/bus"), m("/run/user/1971/bus"), 0).
-				Bind(m("/tmp/hakurei.1971/8e2c76b066dabe574cf073bdb46eb5c1/system_bus_socket"), m("/run/dbus/system_bus_socket"), 0).
-				Remount(m("/"), syscall.MS_RDONLY),
-			SeccompPresets: seccomp.PresetExt | seccomp.PresetDenyTTY | seccomp.PresetDenyDevel,
-			HostNet:        true,
-			ForwardCancel:  true,
-		},
-	},
-}

internal/app/app_pd_linux_test.go

@@ -1,210 +0,0 @@
-package app_test
-
-import (
-	"os"
-	"syscall"
-
-	"hakurei.app/container"
-	"hakurei.app/container/seccomp"
-	"hakurei.app/hst"
-	"hakurei.app/internal/app/state"
-	"hakurei.app/system"
-	"hakurei.app/system/acl"
-	"hakurei.app/system/dbus"
-)
-
-var testCasesPd = []sealTestCase{
-	{
-		"nixos permissive defaults no enablements", new(stubNixOS),
-		&hst.Config{Username: "chronos", Home: m("/home/chronos")},
-		state.ID{
-			0x4a, 0x45, 0x0b, 0x65,
-			0x96, 0xd7, 0xbc, 0x15,
-			0xbd, 0x01, 0x78, 0x0e,
-			0xb9, 0xa6, 0x07, 0xac,
-		},
-		system.New(1000000).
-			Ensure("/tmp/hakurei.1971", 0711).
-			Ensure("/tmp/hakurei.1971/runtime", 0700).UpdatePermType(system.User, "/tmp/hakurei.1971/runtime", acl.Execute).
-			Ensure("/tmp/hakurei.1971/runtime/0", 0700).UpdatePermType(system.User, "/tmp/hakurei.1971/runtime/0", acl.Read, acl.Write, acl.Execute).
-			Ensure("/tmp/hakurei.1971/tmpdir", 0700).UpdatePermType(system.User, "/tmp/hakurei.1971/tmpdir", acl.Execute).
-			Ensure("/tmp/hakurei.1971/tmpdir/0", 01700).UpdatePermType(system.User, "/tmp/hakurei.1971/tmpdir/0", acl.Read, acl.Write, acl.Execute),
-		&container.Params{
-			Dir:  m("/home/chronos"),
-			Path: m("/run/current-system/sw/bin/zsh"),
-			Args: []string{"/run/current-system/sw/bin/zsh"},
-			Env: []string{
-				"HOME=/home/chronos",
-				"SHELL=/run/current-system/sw/bin/zsh",
-				"TERM=xterm-256color",
-				"USER=chronos",
-				"XDG_RUNTIME_DIR=/run/user/65534",
-				"XDG_SESSION_CLASS=user",
-				"XDG_SESSION_TYPE=tty",
-			},
-			Ops: new(container.Ops).
-				Root(m("/"), container.BindWritable).
-				Proc(m("/proc/")).
-				Tmpfs(hst.AbsTmp, 4096, 0755).
-				DevWritable(m("/dev/"), true).
-				Bind(m("/dev/kvm"), m("/dev/kvm"), container.BindWritable|container.BindDevice|container.BindOptional).
-				Readonly(m("/var/run/nscd"), 0755).
-				Etc(m("/etc/"), "4a450b6596d7bc15bd01780eb9a607ac").
-				Tmpfs(m("/run/user/1971"), 8192, 0755).
-				Tmpfs(m("/run/dbus"), 8192, 0755).
-				Remount(m("/dev/"), syscall.MS_RDONLY).
-				Tmpfs(m("/run/user/"), 4096, 0755).
-				Bind(m("/tmp/hakurei.1971/runtime/0"), m("/run/user/65534"), container.BindWritable).
-				Bind(m("/tmp/hakurei.1971/tmpdir/0"), m("/tmp/"), container.BindWritable).
-				Place(m("/etc/passwd"), []byte("chronos:x:65534:65534:Hakurei:/home/chronos:/run/current-system/sw/bin/zsh\n")).
-				Place(m("/etc/group"), []byte("hakurei:x:65534:\n")).
-				Remount(m("/"), syscall.MS_RDONLY),
-			SeccompPresets: seccomp.PresetExt | seccomp.PresetDenyDevel,
-			HostNet:        true,
-			HostAbstract:   true,
-			RetainSession:  true,
-			ForwardCancel:  true,
-		},
-	},
-	{
-		"nixos permissive defaults chromium", new(stubNixOS),
-		&hst.Config{
-			ID:       "org.chromium.Chromium",
-			Args:     []string{"zsh", "-c", "exec chromium "},
-			Identity: 9,
-			Groups:   []string{"video"},
-			Username: "chronos",
-			Home:     m("/home/chronos"),
-			SessionBus: &dbus.Config{
-				Talk: []string{
-					"org.freedesktop.Notifications",
-					"org.freedesktop.FileManager1",
-					"org.freedesktop.ScreenSaver",
-					"org.freedesktop.secrets",
-					"org.kde.kwalletd5",
-					"org.kde.kwalletd6",
-					"org.gnome.SessionManager",
-				},
-				Own: []string{
-					"org.chromium.Chromium.*",
-					"org.mpris.MediaPlayer2.org.chromium.Chromium.*",
-					"org.mpris.MediaPlayer2.chromium.*",
-				},
-				Call: map[string]string{
-					"org.freedesktop.portal.*": "*",
-				},
-				Broadcast: map[string]string{
-					"org.freedesktop.portal.*": "@/org/freedesktop/portal/*",
-				},
-				Filter: true,
-			},
-			SystemBus: &dbus.Config{
-				Talk: []string{
-					"org.bluez",
-					"org.freedesktop.Avahi",
-					"org.freedesktop.UPower",
-				},
-				Filter: true,
-			},
-			Enablements: hst.NewEnablements(system.EWayland | system.EDBus | system.EPulse),
-		},
-		state.ID{
-			0xeb, 0xf0, 0x83, 0xd1,
-			0xb1, 0x75, 0x91, 0x17,
-			0x82, 0xd4, 0x13, 0x36,
-			0x9b, 0x64, 0xce, 0x7c,
-		},
-		system.New(1000009).
-			Ensure("/tmp/hakurei.1971", 0711).
-			Ensure("/tmp/hakurei.1971/runtime", 0700).UpdatePermType(system.User, "/tmp/hakurei.1971/runtime", acl.Execute).
-			Ensure("/tmp/hakurei.1971/runtime/9", 0700).UpdatePermType(system.User, "/tmp/hakurei.1971/runtime/9", acl.Read, acl.Write, acl.Execute).
-			Ensure("/tmp/hakurei.1971/tmpdir", 0700).UpdatePermType(system.User, "/tmp/hakurei.1971/tmpdir", acl.Execute).
-			Ensure("/tmp/hakurei.1971/tmpdir/9", 01700).UpdatePermType(system.User, "/tmp/hakurei.1971/tmpdir/9", acl.Read, acl.Write, acl.Execute).
-			Ephemeral(system.Process, "/tmp/hakurei.1971/ebf083d1b175911782d413369b64ce7c", 0711).
-			Wayland(new(*os.File), "/tmp/hakurei.1971/ebf083d1b175911782d413369b64ce7c/wayland", "/run/user/1971/wayland-0", "org.chromium.Chromium", "ebf083d1b175911782d413369b64ce7c").
-			Ensure("/run/user/1971/hakurei", 0700).UpdatePermType(system.User, "/run/user/1971/hakurei", acl.Execute).
-			Ensure("/run/user/1971", 0700).UpdatePermType(system.User, "/run/user/1971", acl.Execute). // this is ordered as is because the previous Ensure only calls mkdir if XDG_RUNTIME_DIR is unset
-			Ephemeral(system.Process, "/run/user/1971/hakurei/ebf083d1b175911782d413369b64ce7c", 0700).UpdatePermType(system.Process, "/run/user/1971/hakurei/ebf083d1b175911782d413369b64ce7c", acl.Execute).
-			Link("/run/user/1971/pulse/native", "/run/user/1971/hakurei/ebf083d1b175911782d413369b64ce7c/pulse").
-			CopyFile(new([]byte), "/home/ophestra/xdg/config/pulse/cookie", 256, 256).
-			MustProxyDBus("/tmp/hakurei.1971/ebf083d1b175911782d413369b64ce7c/bus", &dbus.Config{
-				Talk: []string{
-					"org.freedesktop.Notifications",
-					"org.freedesktop.FileManager1",
-					"org.freedesktop.ScreenSaver",
-					"org.freedesktop.secrets",
-					"org.kde.kwalletd5",
-					"org.kde.kwalletd6",
-					"org.gnome.SessionManager",
-				},
-				Own: []string{
-					"org.chromium.Chromium.*",
-					"org.mpris.MediaPlayer2.org.chromium.Chromium.*",
-					"org.mpris.MediaPlayer2.chromium.*",
-				},
-				Call: map[string]string{
-					"org.freedesktop.portal.*": "*",
-				},
-				Broadcast: map[string]string{
-					"org.freedesktop.portal.*": "@/org/freedesktop/portal/*",
-				},
-				Filter: true,
-			}, "/tmp/hakurei.1971/ebf083d1b175911782d413369b64ce7c/system_bus_socket", &dbus.Config{
-				Talk: []string{
-					"org.bluez",
-					"org.freedesktop.Avahi",
-					"org.freedesktop.UPower",
-				},
-				Filter: true,
-			}).
-			UpdatePerm("/tmp/hakurei.1971/ebf083d1b175911782d413369b64ce7c/bus", acl.Read, acl.Write).
-			UpdatePerm("/tmp/hakurei.1971/ebf083d1b175911782d413369b64ce7c/system_bus_socket", acl.Read, acl.Write),
-		&container.Params{
-			Dir:  m("/home/chronos"),
-			Path: m("/run/current-system/sw/bin/zsh"),
-			Args: []string{"zsh", "-c", "exec chromium "},
-			Env: []string{
-				"DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/65534/bus",
-				"DBUS_SYSTEM_BUS_ADDRESS=unix:path=/run/dbus/system_bus_socket",
-				"HOME=/home/chronos",
-				"PULSE_COOKIE=" + hst.Tmp + "/pulse-cookie",
-				"PULSE_SERVER=unix:/run/user/65534/pulse/native",
-				"SHELL=/run/current-system/sw/bin/zsh",
-				"TERM=xterm-256color",
-				"USER=chronos",
-				"WAYLAND_DISPLAY=wayland-0",
-				"XDG_RUNTIME_DIR=/run/user/65534",
-				"XDG_SESSION_CLASS=user",
-				"XDG_SESSION_TYPE=tty",
-			},
-			Ops: new(container.Ops).
-				Root(m("/"), container.BindWritable).
-				Proc(m("/proc/")).
-				Tmpfs(hst.AbsTmp, 4096, 0755).
-				DevWritable(m("/dev/"), true).
-				Bind(m("/dev/dri"), m("/dev/dri"), container.BindWritable|container.BindDevice|container.BindOptional).
-				Bind(m("/dev/kvm"), m("/dev/kvm"), container.BindWritable|container.BindDevice|container.BindOptional).
-				Readonly(m("/var/run/nscd"), 0755).
-				Etc(m("/etc/"), "ebf083d1b175911782d413369b64ce7c").
-				Tmpfs(m("/run/user/1971"), 8192, 0755).
-				Tmpfs(m("/run/dbus"), 8192, 0755).
-				Remount(m("/dev/"), syscall.MS_RDONLY).
-				Tmpfs(m("/run/user/"), 4096, 0755).
-				Bind(m("/tmp/hakurei.1971/runtime/9"), m("/run/user/65534"), container.BindWritable).
-				Bind(m("/tmp/hakurei.1971/tmpdir/9"), m("/tmp/"), container.BindWritable).
-				Place(m("/etc/passwd"), []byte("chronos:x:65534:65534:Hakurei:/home/chronos:/run/current-system/sw/bin/zsh\n")).
-				Place(m("/etc/group"), []byte("hakurei:x:65534:\n")).
-				Bind(m("/tmp/hakurei.1971/ebf083d1b175911782d413369b64ce7c/wayland"), m("/run/user/65534/wayland-0"), 0).
-				Bind(m("/run/user/1971/hakurei/ebf083d1b175911782d413369b64ce7c/pulse"), m("/run/user/65534/pulse/native"), 0).
-				Place(m(hst.Tmp+"/pulse-cookie"), nil).
-				Bind(m("/tmp/hakurei.1971/ebf083d1b175911782d413369b64ce7c/bus"), m("/run/user/65534/bus"), 0).
-				Bind(m("/tmp/hakurei.1971/ebf083d1b175911782d413369b64ce7c/system_bus_socket"), m("/run/dbus/system_bus_socket"), 0).
-				Remount(m("/"), syscall.MS_RDONLY),
-			SeccompPresets: seccomp.PresetExt | seccomp.PresetDenyDevel,
-			HostNet:        true,
-			HostAbstract:   true,
-			RetainSession:  true,
-			ForwardCancel:  true,
-		},
-	},
-}

internal/app/app_stub_test.go

@@ -1,34 +1,24 @@
-package app_test
+package app
 
 import (
 	"fmt"
 	"io/fs"
 	"log"
+	"os/exec"
 	"os/user"
-	"strconv"
-
-	"hakurei.app/hst"
 )
 
-// fs methods are not implemented using a real FS
-// to help better understand filesystem access behaviour
 type stubNixOS struct {
 	lookPathErr map[string]error
 	usernameErr map[string]error
 }
 
-func (s *stubNixOS) Getuid() int                              { return 1971 }
+func (k *stubNixOS) new(func(k syscallDispatcher)) { panic("not implemented") }
-func (s *stubNixOS) Getgid() int                              { return 100 }
-func (s *stubNixOS) TempDir() string                          { return "/tmp" }
-func (s *stubNixOS) MustExecutable() string                   { return "/run/wrappers/bin/hakurei" }
-func (s *stubNixOS) Exit(code int)                            { panic("called exit on stub with code " + strconv.Itoa(code)) }
-func (s *stubNixOS) EvalSymlinks(path string) (string, error) { return path, nil }
-func (s *stubNixOS) Uid(aid int) (int, error)                 { return 1000000 + 0*10000 + aid, nil }
 
-func (s *stubNixOS) Println(v ...any)               { log.Println(v...) }
+func (k *stubNixOS) getuid() int { return 1971 }
-func (s *stubNixOS) Printf(format string, v ...any) { log.Printf(format, v...) }
+func (k *stubNixOS) getgid() int { return 100 }
 
-func (s *stubNixOS) LookupEnv(key string) (string, bool) {
+func (k *stubNixOS) lookupEnv(key string) (string, bool) {
 	switch key {
 	case "SHELL":
 		return "/run/current-system/sw/bin/zsh", true
@@ -40,6 +30,8 @@ func (s *stubNixOS) LookupEnv(key string) (string, bool) {
 		return "", false
 	case "HOME":
 		return "/home/ophestra", true
+	case "XDG_RUNTIME_DIR":
+		return "/run/user/1971", true
 	case "XDG_CONFIG_HOME":
 		return "/home/ophestra/xdg/config", true
 	default:
@@ -47,61 +39,7 @@ func (s *stubNixOS) LookupEnv(key string) (string, bool) {
 	}
 }
 
-func (s *stubNixOS) LookPath(file string) (string, error) {
+func (k *stubNixOS) stat(name string) (fs.FileInfo, error) {
-	if s.lookPathErr != nil {
-		if err, ok := s.lookPathErr[file]; ok {
-			return "", err
-		}
-	}
-
-	switch file {
-	case "zsh":
-		return "/run/current-system/sw/bin/zsh", nil
-	default:
-		panic(fmt.Sprintf("attempted to look up unexpected executable %q", file))
-	}
-}
-
-func (s *stubNixOS) LookupGroup(name string) (*user.Group, error) {
-	switch name {
-	case "video":
-		return &user.Group{Gid: "26", Name: "video"}, nil
-	default:
-		return nil, user.UnknownGroupError(name)
-	}
-}
-
-func (s *stubNixOS) ReadDir(name string) ([]fs.DirEntry, error) {
-	switch name {
-	case "/":
-		return stubDirEntries("bin", "boot", "dev", "etc", "home", "lib",
-			"lib64", "nix", "proc", "root", "run", "srv", "sys", "tmp", "usr", "var")
-	case "/run":
-		return stubDirEntries("agetty.reload", "binfmt", "booted-system",
-			"credentials", "cryptsetup", "current-system", "dbus", "host", "keys",
-			"libvirt", "libvirtd.pid", "lock", "log", "lvm", "mount", "NetworkManager",
-			"nginx", "nixos", "nscd", "opengl-driver", "pppd", "resolvconf", "sddm",
-			"store", "syncoid", "system", "systemd", "tmpfiles.d", "udev", "udisks2",
-			"user", "utmp", "virtlogd.pid", "wrappers", "zed.pid", "zed.state")
-	case "/etc":
-		return stubDirEntries("alsa", "bashrc", "binfmt.d", "dbus-1", "default",
-			"ethertypes", "fonts", "fstab", "fuse.conf", "group", "host.conf", "hostid",
-			"hostname", "hostname.CHECKSUM", "hosts", "inputrc", "ipsec.d", "issue", "kbd",
-			"libblockdev", "locale.conf", "localtime", "login.defs", "lsb-release", "lvm",
-			"machine-id", "man_db.conf", "modprobe.d", "modules-load.d", "mtab", "nanorc",
-			"netgroup", "NetworkManager", "nix", "nixos", "NIXOS", "nscd.conf", "nsswitch.conf",
-			"opensnitchd", "os-release", "pam", "pam.d", "passwd", "pipewire", "pki", "polkit-1",
-			"profile", "protocols", "qemu", "resolv.conf", "resolvconf.conf", "rpc", "samba",
-			"sddm.conf", "secureboot", "services", "set-environment", "shadow", "shells", "ssh",
-			"ssl", "static", "subgid", "subuid", "sudoers", "sysctl.d", "systemd", "terminfo",
-			"tmpfiles.d", "udev", "udisks2", "UPower", "vconsole.conf", "X11", "zfs", "zinputrc",
-			"zoneinfo", "zprofile", "zshenv", "zshrc")
-	default:
-		panic(fmt.Sprintf("attempted to read unexpected directory %q", name))
-	}
-}
-
-func (s *stubNixOS) Stat(name string) (fs.FileInfo, error) {
 	switch name {
 	case "/var/run/nscd":
 		return nil, nil
@@ -118,17 +56,144 @@ func (s *stubNixOS) Stat(name string) (fs.FileInfo, error) {
 	}
 }
 
-func (s *stubNixOS) Open(name string) (fs.File, error) {
+func (k *stubNixOS) readdir(name string) ([]fs.DirEntry, error) {
 	switch name {
+	case "/":
+		return stubDirEntries("bin", "boot", "dev", "etc", "home", "lib",
+			"lib64", "nix", "proc", "root", "run", "srv", "sys", "tmp", "usr", "var")
+
+	case "/run":
+		return stubDirEntries("agetty.reload", "binfmt", "booted-system",
+			"credentials", "cryptsetup", "current-system", "dbus", "host", "keys",
+			"libvirt", "libvirtd.pid", "lock", "log", "lvm", "mount", "NetworkManager",
+			"nginx", "nixos", "nscd", "opengl-driver", "pppd", "resolvconf", "sddm",
+			"store", "syncoid", "system", "systemd", "tmpfiles.d", "udev", "udisks2",
+			"user", "utmp", "virtlogd.pid", "wrappers", "zed.pid", "zed.state")
+
+	case "/etc":
+		return stubDirEntries("alsa", "bashrc", "binfmt.d", "dbus-1", "default",
+			"ethertypes", "fonts", "fstab", "fuse.conf", "group", "host.conf", "hostid",
+			"hostname", "hostname.CHECKSUM", "hosts", "inputrc", "ipsec.d", "issue", "kbd",
+			"libblockdev", "locale.conf", "localtime", "login.defs", "lsb-release", "lvm",
+			"machine-id", "man_db.conf", "modprobe.d", "modules-load.d", "mtab", "nanorc",
+			"netgroup", "NetworkManager", "nix", "nixos", "NIXOS", "nscd.conf", "nsswitch.conf",
+			"opensnitchd", "os-release", "pam", "pam.d", "passwd", "pipewire", "pki", "polkit-1",
+			"profile", "protocols", "qemu", "resolv.conf", "resolvconf.conf", "rpc", "samba",
+			"sddm.conf", "secureboot", "services", "set-environment", "shadow", "shells", "ssh",
+			"ssl", "static", "subgid", "subuid", "sudoers", "sysctl.d", "systemd", "terminfo",
+			"tmpfiles.d", "udev", "udisks2", "UPower", "vconsole.conf", "X11", "zfs", "zinputrc",
+			"zoneinfo", "zprofile", "zshenv", "zshrc")
+
 	default:
-		panic(fmt.Sprintf("attempted to open unexpected file %q", name))
+		panic(fmt.Sprintf("attempted to read unexpected directory %q", name))
 	}
 }
 
-func (s *stubNixOS) Paths() hst.Paths {
+func (k *stubNixOS) tempdir() string { return "/tmp/" }
-	return hst.Paths{
+
-		SharePath:   m("/tmp/hakurei.1971"),
+func (k *stubNixOS) evalSymlinks(path string) (string, error) {
-		RuntimePath: m("/run/user/1971"),
+	switch path {
-		RunDirPath:  m("/run/user/1971/hakurei"),
+	case "/run/user/1971":
+		return "/run/user/1971", nil
+	case "/tmp/hakurei.0":
+		return "/tmp/hakurei.0", nil
+	case "/run/dbus":
+		return "/run/dbus", nil
+	case "/dev/kvm":
+		return "/dev/kvm", nil
+	case "/etc/":
+		return "/etc/", nil
+	case "/bin":
+		return "/bin", nil
+	case "/boot":
+		return "/boot", nil
+	case "/home":
+		return "/home", nil
+	case "/lib":
+		return "/lib", nil
+	case "/lib64":
+		return "/lib64", nil
+	case "/nix":
+		return "/nix", nil
+	case "/root":
+		return "/root", nil
+	case "/run":
+		return "/run", nil
+	case "/srv":
+		return "/srv", nil
+	case "/sys":
+		return "/sys", nil
+	case "/usr":
+		return "/usr", nil
+	case "/var":
+		return "/var", nil
+	case "/dev/dri":
+		return "/dev/dri", nil
+	case "/usr/bin/":
+		return "/usr/bin/", nil
+	case "/nix/store":
+		return "/nix/store", nil
+	case "/run/current-system":
+		return "/nix/store/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa-nixos-system-satori-25.05.99999999.aaaaaaa", nil
+	case "/sys/block":
+		return "/sys/block", nil
+	case "/sys/bus":
+		return "/sys/bus", nil
+	case "/sys/class":
+		return "/sys/class", nil
+	case "/sys/dev":
+		return "/sys/dev", nil
+	case "/sys/devices":
+		return "/sys/devices", nil
+	case "/run/opengl-driver":
+		return "/nix/store/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa-graphics-drivers", nil
+	case "/var/lib/persist/module/hakurei/0/1":
+		return "/var/lib/persist/module/hakurei/0/1", nil
+	default:
+		panic(fmt.Sprintf("attempted to evaluate unexpected path %q", path))
 	}
 }
+
+func (k *stubNixOS) lookPath(file string) (string, error) {
+	if k.lookPathErr != nil {
+		if err, ok := k.lookPathErr[file]; ok {
+			return "", err
+		}
+	}
+
+	switch file {
+	case "zsh":
+		return "/run/current-system/sw/bin/zsh", nil
+	default:
+		panic(fmt.Sprintf("attempted to look up unexpected executable %q", file))
+	}
+}
+
+func (k *stubNixOS) lookupGroupId(name string) (string, error) {
+	switch name {
+	case "video":
+		return "26", nil
+	default:
+		return "", user.UnknownGroupError(name)
+	}
+}
+
+func (k *stubNixOS) cmdOutput(cmd *exec.Cmd) ([]byte, error) {
+	switch cmd.Path {
+	case "/proc/nonexistent/hsu":
+		return []byte{'0'}, nil
+	default:
+		panic(fmt.Sprintf("unexpected cmd %#v", cmd))
+	}
+}
+
+func (k *stubNixOS) overflowUid() int { return 65534 }
+func (k *stubNixOS) overflowGid() int { return 65534 }
+
+func (k *stubNixOS) mustHsuPath() string { return "/proc/nonexistent/hsu" }
+
+func (k *stubNixOS) fatalf(format string, v ...any) { panic(fmt.Sprintf(format, v...)) }
+
+func (k *stubNixOS) isVerbose() bool                  { return true }
+func (k *stubNixOS) verbose(v ...any)                 { log.Print(v...) }
+func (k *stubNixOS) verbosef(format string, v ...any) { log.Printf(format, v...) }

internal/app/app_test.go

@@ -0,0 +1,452 @@
+package app
+
+import (
+	"context"
+	"encoding/json"
+	"io/fs"
+	"os"
+	"reflect"
+	"syscall"
+	"testing"
+	"time"
+
+	"hakurei.app/container"
+	"hakurei.app/container/seccomp"
+	"hakurei.app/hst"
+	"hakurei.app/internal/app/state"
+	"hakurei.app/system"
+	"hakurei.app/system/acl"
+	"hakurei.app/system/dbus"
+)
+
+func TestApp(t *testing.T) {
+	testCases := []struct {
+		name       string
+		k          syscallDispatcher
+		config     *hst.Config
+		id         state.ID
+		wantSys    *system.I
+		wantParams *container.Params
+	}{
+		{
+			"nixos permissive defaults no enablements", new(stubNixOS),
+			&hst.Config{Username: "chronos", Home: m("/home/chronos")},
+			state.ID{
+				0x4a, 0x45, 0x0b, 0x65,
+				0x96, 0xd7, 0xbc, 0x15,
+				0xbd, 0x01, 0x78, 0x0e,
+				0xb9, 0xa6, 0x07, 0xac,
+			},
+			system.New(context.TODO(), 1000000).
+				Ensure("/tmp/hakurei.0", 0711).
+				Ensure("/tmp/hakurei.0/runtime", 0700).UpdatePermType(system.User, "/tmp/hakurei.0/runtime", acl.Execute).
+				Ensure("/tmp/hakurei.0/runtime/0", 0700).UpdatePermType(system.User, "/tmp/hakurei.0/runtime/0", acl.Read, acl.Write, acl.Execute).
+				Ensure("/tmp/hakurei.0/tmpdir", 0700).UpdatePermType(system.User, "/tmp/hakurei.0/tmpdir", acl.Execute).
+				Ensure("/tmp/hakurei.0/tmpdir/0", 01700).UpdatePermType(system.User, "/tmp/hakurei.0/tmpdir/0", acl.Read, acl.Write, acl.Execute),
+			&container.Params{
+				Dir:  m("/home/chronos"),
+				Path: m("/run/current-system/sw/bin/zsh"),
+				Args: []string{"/run/current-system/sw/bin/zsh"},
+				Env: []string{
+					"HOME=/home/chronos",
+					"SHELL=/run/current-system/sw/bin/zsh",
+					"TERM=xterm-256color",
+					"USER=chronos",
+					"XDG_RUNTIME_DIR=/run/user/65534",
+					"XDG_SESSION_CLASS=user",
+					"XDG_SESSION_TYPE=tty",
+				},
+				Ops: new(container.Ops).
+					Root(m("/"), container.BindWritable).
+					Proc(m("/proc/")).
+					Tmpfs(hst.AbsTmp, 4096, 0755).
+					DevWritable(m("/dev/"), true).
+					Tmpfs(m("/dev/shm"), 0, 01777).
+					Bind(m("/dev/kvm"), m("/dev/kvm"), container.BindWritable|container.BindDevice|container.BindOptional).
+					Readonly(m("/var/run/nscd"), 0755).
+					Etc(m("/etc/"), "4a450b6596d7bc15bd01780eb9a607ac").
+					Tmpfs(m("/run/user/1971"), 8192, 0755).
+					Tmpfs(m("/run/dbus"), 8192, 0755).
+					Remount(m("/dev/"), syscall.MS_RDONLY).
+					Tmpfs(m("/run/user/"), 4096, 0755).
+					Bind(m("/tmp/hakurei.0/runtime/0"), m("/run/user/65534"), container.BindWritable).
+					Bind(m("/tmp/hakurei.0/tmpdir/0"), m("/tmp/"), container.BindWritable).
+					Place(m("/etc/passwd"), []byte("chronos:x:65534:65534:Hakurei:/home/chronos:/run/current-system/sw/bin/zsh\n")).
+					Place(m("/etc/group"), []byte("hakurei:x:65534:\n")).
+					Remount(m("/"), syscall.MS_RDONLY),
+				SeccompPresets: seccomp.PresetExt | seccomp.PresetDenyDevel,
+				HostNet:        true,
+				HostAbstract:   true,
+				RetainSession:  true,
+				ForwardCancel:  true,
+			},
+		},
+		{
+			"nixos permissive defaults chromium", new(stubNixOS),
+			&hst.Config{
+				ID:       "org.chromium.Chromium",
+				Args:     []string{"zsh", "-c", "exec chromium "},
+				Identity: 9,
+				Groups:   []string{"video"},
+				Username: "chronos",
+				Home:     m("/home/chronos"),
+				SessionBus: &dbus.Config{
+					Talk: []string{
+						"org.freedesktop.Notifications",
+						"org.freedesktop.FileManager1",
+						"org.freedesktop.ScreenSaver",
+						"org.freedesktop.secrets",
+						"org.kde.kwalletd5",
+						"org.kde.kwalletd6",
+						"org.gnome.SessionManager",
+					},
+					Own: []string{
+						"org.chromium.Chromium.*",
+						"org.mpris.MediaPlayer2.org.chromium.Chromium.*",
+						"org.mpris.MediaPlayer2.chromium.*",
+					},
+					Call: map[string]string{
+						"org.freedesktop.portal.*": "*",
+					},
+					Broadcast: map[string]string{
+						"org.freedesktop.portal.*": "@/org/freedesktop/portal/*",
+					},
+					Filter: true,
+				},
+				SystemBus: &dbus.Config{
+					Talk: []string{
+						"org.bluez",
+						"org.freedesktop.Avahi",
+						"org.freedesktop.UPower",
+					},
+					Filter: true,
+				},
+				Enablements: hst.NewEnablements(system.EWayland | system.EDBus | system.EPulse),
+			},
+			state.ID{
+				0xeb, 0xf0, 0x83, 0xd1,
+				0xb1, 0x75, 0x91, 0x17,
+				0x82, 0xd4, 0x13, 0x36,
+				0x9b, 0x64, 0xce, 0x7c,
+			},
+			system.New(context.TODO(), 1000009).
+				Ensure("/tmp/hakurei.0", 0711).
+				Ensure("/tmp/hakurei.0/runtime", 0700).UpdatePermType(system.User, "/tmp/hakurei.0/runtime", acl.Execute).
+				Ensure("/tmp/hakurei.0/runtime/9", 0700).UpdatePermType(system.User, "/tmp/hakurei.0/runtime/9", acl.Read, acl.Write, acl.Execute).
+				Ensure("/tmp/hakurei.0/tmpdir", 0700).UpdatePermType(system.User, "/tmp/hakurei.0/tmpdir", acl.Execute).
+				Ensure("/tmp/hakurei.0/tmpdir/9", 01700).UpdatePermType(system.User, "/tmp/hakurei.0/tmpdir/9", acl.Read, acl.Write, acl.Execute).
+				Ephemeral(system.Process, "/tmp/hakurei.0/ebf083d1b175911782d413369b64ce7c", 0711).
+				Wayland(new(*os.File), "/tmp/hakurei.0/ebf083d1b175911782d413369b64ce7c/wayland", "/run/user/1971/wayland-0", "org.chromium.Chromium", "ebf083d1b175911782d413369b64ce7c").
+				Ensure("/run/user/1971/hakurei", 0700).UpdatePermType(system.User, "/run/user/1971/hakurei", acl.Execute).
+				Ensure("/run/user/1971", 0700).UpdatePermType(system.User, "/run/user/1971", acl.Execute). // this is ordered as is because the previous Ensure only calls mkdir if XDG_RUNTIME_DIR is unset
+				Ephemeral(system.Process, "/run/user/1971/hakurei/ebf083d1b175911782d413369b64ce7c", 0700).UpdatePermType(system.Process, "/run/user/1971/hakurei/ebf083d1b175911782d413369b64ce7c", acl.Execute).
+				Link("/run/user/1971/pulse/native", "/run/user/1971/hakurei/ebf083d1b175911782d413369b64ce7c/pulse").
+				CopyFile(new([]byte), "/home/ophestra/xdg/config/pulse/cookie", 256, 256).
+				MustProxyDBus("/tmp/hakurei.0/ebf083d1b175911782d413369b64ce7c/bus", &dbus.Config{
+					Talk: []string{
+						"org.freedesktop.Notifications",
+						"org.freedesktop.FileManager1",
+						"org.freedesktop.ScreenSaver",
+						"org.freedesktop.secrets",
+						"org.kde.kwalletd5",
+						"org.kde.kwalletd6",
+						"org.gnome.SessionManager",
+					},
+					Own: []string{
+						"org.chromium.Chromium.*",
+						"org.mpris.MediaPlayer2.org.chromium.Chromium.*",
+						"org.mpris.MediaPlayer2.chromium.*",
+					},
+					Call: map[string]string{
+						"org.freedesktop.portal.*": "*",
+					},
+					Broadcast: map[string]string{
+						"org.freedesktop.portal.*": "@/org/freedesktop/portal/*",
+					},
+					Filter: true,
+				}, "/tmp/hakurei.0/ebf083d1b175911782d413369b64ce7c/system_bus_socket", &dbus.Config{
+					Talk: []string{
+						"org.bluez",
+						"org.freedesktop.Avahi",
+						"org.freedesktop.UPower",
+					},
+					Filter: true,
+				}).
+				UpdatePerm("/tmp/hakurei.0/ebf083d1b175911782d413369b64ce7c/bus", acl.Read, acl.Write).
+				UpdatePerm("/tmp/hakurei.0/ebf083d1b175911782d413369b64ce7c/system_bus_socket", acl.Read, acl.Write),
+			&container.Params{
+				Dir:  m("/home/chronos"),
+				Path: m("/run/current-system/sw/bin/zsh"),
+				Args: []string{"zsh", "-c", "exec chromium "},
+				Env: []string{
+					"DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/65534/bus",
+					"DBUS_SYSTEM_BUS_ADDRESS=unix:path=/run/dbus/system_bus_socket",
+					"HOME=/home/chronos",
+					"PULSE_COOKIE=" + hst.Tmp + "/pulse-cookie",
+					"PULSE_SERVER=unix:/run/user/65534/pulse/native",
+					"SHELL=/run/current-system/sw/bin/zsh",
+					"TERM=xterm-256color",
+					"USER=chronos",
+					"WAYLAND_DISPLAY=wayland-0",
+					"XDG_RUNTIME_DIR=/run/user/65534",
+					"XDG_SESSION_CLASS=user",
+					"XDG_SESSION_TYPE=tty",
+				},
+				Ops: new(container.Ops).
+					Root(m("/"), container.BindWritable).
+					Proc(m("/proc/")).
+					Tmpfs(hst.AbsTmp, 4096, 0755).
+					DevWritable(m("/dev/"), true).
+					Tmpfs(m("/dev/shm"), 0, 01777).
+					Bind(m("/dev/dri"), m("/dev/dri"), container.BindWritable|container.BindDevice|container.BindOptional).
+					Bind(m("/dev/kvm"), m("/dev/kvm"), container.BindWritable|container.BindDevice|container.BindOptional).
+					Readonly(m("/var/run/nscd"), 0755).
+					Etc(m("/etc/"), "ebf083d1b175911782d413369b64ce7c").
+					Tmpfs(m("/run/user/1971"), 8192, 0755).
+					Tmpfs(m("/run/dbus"), 8192, 0755).
+					Remount(m("/dev/"), syscall.MS_RDONLY).
+					Tmpfs(m("/run/user/"), 4096, 0755).
+					Bind(m("/tmp/hakurei.0/runtime/9"), m("/run/user/65534"), container.BindWritable).
+					Bind(m("/tmp/hakurei.0/tmpdir/9"), m("/tmp/"), container.BindWritable).
+					Place(m("/etc/passwd"), []byte("chronos:x:65534:65534:Hakurei:/home/chronos:/run/current-system/sw/bin/zsh\n")).
+					Place(m("/etc/group"), []byte("hakurei:x:65534:\n")).
+					Bind(m("/tmp/hakurei.0/ebf083d1b175911782d413369b64ce7c/wayland"), m("/run/user/65534/wayland-0"), 0).
+					Bind(m("/run/user/1971/hakurei/ebf083d1b175911782d413369b64ce7c/pulse"), m("/run/user/65534/pulse/native"), 0).
+					Place(m(hst.Tmp+"/pulse-cookie"), nil).
+					Bind(m("/tmp/hakurei.0/ebf083d1b175911782d413369b64ce7c/bus"), m("/run/user/65534/bus"), 0).
+					Bind(m("/tmp/hakurei.0/ebf083d1b175911782d413369b64ce7c/system_bus_socket"), m("/run/dbus/system_bus_socket"), 0).
+					Remount(m("/"), syscall.MS_RDONLY),
+				SeccompPresets: seccomp.PresetExt | seccomp.PresetDenyDevel,
+				HostNet:        true,
+				HostAbstract:   true,
+				RetainSession:  true,
+				ForwardCancel:  true,
+			},
+		},
+
+		{
+			"nixos chromium direct wayland", new(stubNixOS),
+			&hst.Config{
+				ID:          "org.chromium.Chromium",
+				Path:        m("/nix/store/yqivzpzzn7z5x0lq9hmbzygh45d8rhqd-chromium-start"),
+				Enablements: hst.NewEnablements(system.EWayland | system.EDBus | system.EPulse),
+				Shell:       m("/run/current-system/sw/bin/zsh"),
+
+				Container: &hst.ContainerConfig{
+					Userns: true, HostNet: true, MapRealUID: true, Env: nil,
+					Filesystem: []hst.FilesystemConfigJSON{
+						f(&hst.FSBind{Source: m("/bin")}),
+						f(&hst.FSBind{Source: m("/usr/bin/")}),
+						f(&hst.FSBind{Source: m("/nix/store")}),
+						f(&hst.FSBind{Source: m("/run/current-system")}),
+						f(&hst.FSBind{Source: m("/sys/block"), Optional: true}),
+						f(&hst.FSBind{Source: m("/sys/bus"), Optional: true}),
+						f(&hst.FSBind{Source: m("/sys/class"), Optional: true}),
+						f(&hst.FSBind{Source: m("/sys/dev"), Optional: true}),
+						f(&hst.FSBind{Source: m("/sys/devices"), Optional: true}),
+						f(&hst.FSBind{Source: m("/run/opengl-driver")}),
+						f(&hst.FSBind{Source: m("/dev/dri"), Device: true, Optional: true}),
+						f(&hst.FSBind{Source: m("/etc/"), Target: m("/etc/"), Special: true}),
+						f(&hst.FSBind{Source: m("/var/lib/persist/module/hakurei/0/1"), Write: true, Ensure: true}),
+					},
+				},
+				SystemBus: &dbus.Config{
+					Talk:   []string{"org.bluez", "org.freedesktop.Avahi", "org.freedesktop.UPower"},
+					Filter: true,
+				},
+				SessionBus: &dbus.Config{
+					Talk: []string{
+						"org.freedesktop.FileManager1", "org.freedesktop.Notifications",
+						"org.freedesktop.ScreenSaver", "org.freedesktop.secrets",
+						"org.kde.kwalletd5", "org.kde.kwalletd6",
+					},
+					Own: []string{
+						"org.chromium.Chromium.*",
+						"org.mpris.MediaPlayer2.org.chromium.Chromium.*",
+						"org.mpris.MediaPlayer2.chromium.*",
+					},
+					Call: map[string]string{}, Broadcast: map[string]string{},
+					Filter: true,
+				},
+				DirectWayland: true,
+
+				Username: "u0_a1",
+				Home:     m("/var/lib/persist/module/hakurei/0/1"),
+				Identity: 1, Groups: []string{},
+			},
+			state.ID{
+				0x8e, 0x2c, 0x76, 0xb0,
+				0x66, 0xda, 0xbe, 0x57,
+				0x4c, 0xf0, 0x73, 0xbd,
+				0xb4, 0x6e, 0xb5, 0xc1,
+			},
+			system.New(context.TODO(), 1000001).
+				Ensure("/tmp/hakurei.0", 0711).
+				Ensure("/tmp/hakurei.0/runtime", 0700).UpdatePermType(system.User, "/tmp/hakurei.0/runtime", acl.Execute).
+				Ensure("/tmp/hakurei.0/runtime/1", 0700).UpdatePermType(system.User, "/tmp/hakurei.0/runtime/1", acl.Read, acl.Write, acl.Execute).
+				Ensure("/tmp/hakurei.0/tmpdir", 0700).UpdatePermType(system.User, "/tmp/hakurei.0/tmpdir", acl.Execute).
+				Ensure("/tmp/hakurei.0/tmpdir/1", 01700).UpdatePermType(system.User, "/tmp/hakurei.0/tmpdir/1", acl.Read, acl.Write, acl.Execute).
+				Ensure("/run/user/1971/hakurei", 0700).UpdatePermType(system.User, "/run/user/1971/hakurei", acl.Execute).
+				Ensure("/run/user/1971", 0700).UpdatePermType(system.User, "/run/user/1971", acl.Execute). // this is ordered as is because the previous Ensure only calls mkdir if XDG_RUNTIME_DIR is unset
+				UpdatePermType(system.EWayland, "/run/user/1971/wayland-0", acl.Read, acl.Write, acl.Execute).
+				Ephemeral(system.Process, "/run/user/1971/hakurei/8e2c76b066dabe574cf073bdb46eb5c1", 0700).UpdatePermType(system.Process, "/run/user/1971/hakurei/8e2c76b066dabe574cf073bdb46eb5c1", acl.Execute).
+				Link("/run/user/1971/pulse/native", "/run/user/1971/hakurei/8e2c76b066dabe574cf073bdb46eb5c1/pulse").
+				CopyFile(nil, "/home/ophestra/xdg/config/pulse/cookie", 256, 256).
+				Ephemeral(system.Process, "/tmp/hakurei.0/8e2c76b066dabe574cf073bdb46eb5c1", 0711).
+				MustProxyDBus("/tmp/hakurei.0/8e2c76b066dabe574cf073bdb46eb5c1/bus", &dbus.Config{
+					Talk: []string{
+						"org.freedesktop.FileManager1", "org.freedesktop.Notifications",
+						"org.freedesktop.ScreenSaver", "org.freedesktop.secrets",
+						"org.kde.kwalletd5", "org.kde.kwalletd6",
+					},
+					Own: []string{
+						"org.chromium.Chromium.*",
+						"org.mpris.MediaPlayer2.org.chromium.Chromium.*",
+						"org.mpris.MediaPlayer2.chromium.*",
+					},
+					Call: map[string]string{}, Broadcast: map[string]string{},
+					Filter: true,
+				}, "/tmp/hakurei.0/8e2c76b066dabe574cf073bdb46eb5c1/system_bus_socket", &dbus.Config{
+					Talk: []string{
+						"org.bluez",
+						"org.freedesktop.Avahi",
+						"org.freedesktop.UPower",
+					},
+					Filter: true,
+				}).
+				UpdatePerm("/tmp/hakurei.0/8e2c76b066dabe574cf073bdb46eb5c1/bus", acl.Read, acl.Write).
+				UpdatePerm("/tmp/hakurei.0/8e2c76b066dabe574cf073bdb46eb5c1/system_bus_socket", acl.Read, acl.Write),
+			&container.Params{
+				Uid:  1971,
+				Gid:  100,
+				Dir:  m("/var/lib/persist/module/hakurei/0/1"),
+				Path: m("/nix/store/yqivzpzzn7z5x0lq9hmbzygh45d8rhqd-chromium-start"),
+				Args: []string{"/nix/store/yqivzpzzn7z5x0lq9hmbzygh45d8rhqd-chromium-start"},
+				Env: []string{
+					"DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1971/bus",
+					"DBUS_SYSTEM_BUS_ADDRESS=unix:path=/run/dbus/system_bus_socket",
+					"HOME=/var/lib/persist/module/hakurei/0/1",
+					"PULSE_COOKIE=" + hst.Tmp + "/pulse-cookie",
+					"PULSE_SERVER=unix:/run/user/1971/pulse/native",
+					"SHELL=/run/current-system/sw/bin/zsh",
+					"TERM=xterm-256color",
+					"USER=u0_a1",
+					"WAYLAND_DISPLAY=wayland-0",
+					"XDG_RUNTIME_DIR=/run/user/1971",
+					"XDG_SESSION_CLASS=user",
+					"XDG_SESSION_TYPE=tty",
+				},
+				Ops: new(container.Ops).
+					Proc(m("/proc/")).
+					Tmpfs(hst.AbsTmp, 4096, 0755).
+					DevWritable(m("/dev/"), true).
+					Tmpfs(m("/dev/shm"), 0, 01777).
+					Bind(m("/bin"), m("/bin"), 0).
+					Bind(m("/usr/bin/"), m("/usr/bin/"), 0).
+					Bind(m("/nix/store"), m("/nix/store"), 0).
+					Bind(m("/run/current-system"), m("/run/current-system"), 0).
+					Bind(m("/sys/block"), m("/sys/block"), container.BindOptional).
+					Bind(m("/sys/bus"), m("/sys/bus"), container.BindOptional).
+					Bind(m("/sys/class"), m("/sys/class"), container.BindOptional).
+					Bind(m("/sys/dev"), m("/sys/dev"), container.BindOptional).
+					Bind(m("/sys/devices"), m("/sys/devices"), container.BindOptional).
+					Bind(m("/run/opengl-driver"), m("/run/opengl-driver"), 0).
+					Bind(m("/dev/dri"), m("/dev/dri"), container.BindDevice|container.BindWritable|container.BindOptional).
+					Etc(m("/etc/"), "8e2c76b066dabe574cf073bdb46eb5c1").
+					Bind(m("/var/lib/persist/module/hakurei/0/1"), m("/var/lib/persist/module/hakurei/0/1"), container.BindWritable|container.BindEnsure).
+					Remount(m("/dev/"), syscall.MS_RDONLY).
+					Tmpfs(m("/run/user/"), 4096, 0755).
+					Bind(m("/tmp/hakurei.0/runtime/1"), m("/run/user/1971"), container.BindWritable).
+					Bind(m("/tmp/hakurei.0/tmpdir/1"), m("/tmp/"), container.BindWritable).
+					Place(m("/etc/passwd"), []byte("u0_a1:x:1971:100:Hakurei:/var/lib/persist/module/hakurei/0/1:/run/current-system/sw/bin/zsh\n")).
+					Place(m("/etc/group"), []byte("hakurei:x:100:\n")).
+					Bind(m("/run/user/1971/wayland-0"), m("/run/user/1971/wayland-0"), 0).
+					Bind(m("/run/user/1971/hakurei/8e2c76b066dabe574cf073bdb46eb5c1/pulse"), m("/run/user/1971/pulse/native"), 0).
+					Place(m(hst.Tmp+"/pulse-cookie"), nil).
+					Bind(m("/tmp/hakurei.0/8e2c76b066dabe574cf073bdb46eb5c1/bus"), m("/run/user/1971/bus"), 0).
+					Bind(m("/tmp/hakurei.0/8e2c76b066dabe574cf073bdb46eb5c1/system_bus_socket"), m("/run/dbus/system_bus_socket"), 0).
+					Remount(m("/"), syscall.MS_RDONLY),
+				SeccompPresets: seccomp.PresetExt | seccomp.PresetDenyTTY | seccomp.PresetDenyDevel,
+				HostNet:        true,
+				ForwardCancel:  true,
+			},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Run("finalise", func(t *testing.T) {
+				seal := outcome{syscallDispatcher: tc.k, id: &stringPair[state.ID]{tc.id, tc.id.String()}}
+				err := seal.finalise(t.Context(), tc.config)
+				if err != nil {
+					if s, ok := container.GetErrorMessage(err); !ok {
+						t.Fatalf("Seal: error = %v", err)
+					} else {
+						t.Fatalf("Seal: %s", s)
+					}
+				}
+
+				t.Run("sys", func(t *testing.T) {
+					if !seal.sys.Equal(tc.wantSys) {
+						t.Errorf("Seal: sys = %#v, want %#v", seal.sys, tc.wantSys)
+					}
+				})
+
+				t.Run("params", func(t *testing.T) {
+					if !reflect.DeepEqual(seal.container, tc.wantParams) {
+						t.Errorf("seal: container =\n%s\n, want\n%s", mustMarshal(seal.container), mustMarshal(tc.wantParams))
+					}
+				})
+			})
+		})
+	}
+}
+
+func mustMarshal(v any) string {
+	if b, err := json.Marshal(v); err != nil {
+		panic(err.Error())
+	} else {
+		return string(b)
+	}
+}
+
+func stubDirEntries(names ...string) (e []fs.DirEntry, err error) {
+	e = make([]fs.DirEntry, len(names))
+	for i, name := range names {
+		e[i] = stubDirEntryPath(name)
+	}
+	return
+}
+
+type stubDirEntryPath string
+
+func (p stubDirEntryPath) Name() string               { return string(p) }
+func (p stubDirEntryPath) IsDir() bool                { panic("attempted to call IsDir") }
+func (p stubDirEntryPath) Type() fs.FileMode          { panic("attempted to call Type") }
+func (p stubDirEntryPath) Info() (fs.FileInfo, error) { panic("attempted to call Info") }
+
+type stubFileInfoMode fs.FileMode
+
+func (s stubFileInfoMode) Name() string       { panic("attempted to call Name") }
+func (s stubFileInfoMode) Size() int64        { panic("attempted to call Size") }
+func (s stubFileInfoMode) Mode() fs.FileMode  { return fs.FileMode(s) }
+func (s stubFileInfoMode) ModTime() time.Time { panic("attempted to call ModTime") }
+func (s stubFileInfoMode) IsDir() bool        { panic("attempted to call IsDir") }
+func (s stubFileInfoMode) Sys() any           { panic("attempted to call Sys") }
+
+type stubFileInfoIsDir bool
+
+func (s stubFileInfoIsDir) Name() string       { panic("attempted to call Name") }
+func (s stubFileInfoIsDir) Size() int64        { panic("attempted to call Size") }
+func (s stubFileInfoIsDir) Mode() fs.FileMode  { panic("attempted to call Mode") }
+func (s stubFileInfoIsDir) ModTime() time.Time { panic("attempted to call ModTime") }
+func (s stubFileInfoIsDir) IsDir() bool        { return bool(s) }
+func (s stubFileInfoIsDir) Sys() any           { panic("attempted to call Sys") }
+
+func m(pathname string) *container.Absolute {
+	return container.MustAbs(pathname)
+}
+
+func f(c hst.FilesystemConfig) hst.FilesystemConfigJSON {
+	return hst.FilesystemConfigJSON{FilesystemConfig: c}
+}

internal/app/container.go

@@ -11,20 +11,23 @@ import (
 	"hakurei.app/container"
 	"hakurei.app/container/seccomp"
 	"hakurei.app/hst"
-	"hakurei.app/internal/hlog"
-	"hakurei.app/internal/sys"
 	"hakurei.app/system/dbus"
 )
 
-// in practice there should be less than 30 entries added by the runtime;
+// in practice there should be less than 30 system mount points
-// allocating slightly more as a margin for future expansion
 const preallocateOpsCount = 1 << 5
 
 // newContainer initialises [container.Params] via [hst.ContainerConfig].
 // Note that remaining container setup must be queued by the caller.
-func newContainer(s *hst.ContainerConfig, os sys.State, prefix string, uid, gid *int) (*container.Params, map[string]string, error) {
+func newContainer(
+	k syscallDispatcher,
+	s *hst.ContainerConfig,
+	prefix string,
+	sc *hst.Paths,
+	uid, gid *int,
+) (*container.Params, map[string]string, error) {
 	if s == nil {
-		return nil, nil, hlog.WrapErr(syscall.EBADE, "invalid container configuration")
+		return nil, nil, newWithMessage("invalid container configuration")
 	}
 
 	params := &container.Params{
@@ -40,9 +43,7 @@ func newContainer(s *hst.ContainerConfig, os sys.State, prefix string, uid, gid
 		ForwardCancel: s.WaitDelay >= 0,
 	}
 
-	as := &hst.ApplyState{
+	as := &hst.ApplyState{AutoEtcPrefix: prefix}
-		AutoEtcPrefix: prefix,
-	}
 	{
 		ops := make(container.Ops, 0, preallocateOpsCount+len(s.Filesystem))
 		params.Ops = &ops
@@ -67,15 +68,13 @@ func newContainer(s *hst.ContainerConfig, os sys.State, prefix string, uid, gid
 	}
 
 	if s.MapRealUID {
-		/* some programs fail to connect to dbus session running as a different uid
+		params.Uid = k.getuid()
-		so this workaround is introduced to map priv-side caller uid in container */
-		params.Uid = os.Getuid()
 		*uid = params.Uid
-		params.Gid = os.Getgid()
+		params.Gid = k.getgid()
 		*gid = params.Gid
 	} else {
-		*uid = container.OverflowUid()
+		*uid = k.overflowUid()
-		*gid = container.OverflowGid()
+		*gid = k.overflowGid()
 	}
 
 	filesystem := s.Filesystem
@@ -102,13 +101,15 @@ func newContainer(s *hst.ContainerConfig, os sys.State, prefix string, uid, gid
 	} else {
 		params.Bind(container.AbsFHSDev, container.AbsFHSDev, container.BindWritable|container.BindDevice)
 	}
+	// /dev is mounted readonly later on, this prevents /dev/shm from going readonly with it
+	params.Tmpfs(container.AbsFHSDev.Append("shm"), 0, 01777)
 
 	/* retrieve paths and hide them if they're made available in the sandbox;
+
 	this feature tries to improve user experience of permissive defaults, and
 	to warn about issues in custom configuration; it is NOT a security feature
 	and should not be treated as such, ALWAYS be careful with what you bind */
 	var hidePaths []string
-	sc := os.Paths()
 	hidePaths = append(hidePaths, sc.RuntimePath.String(), sc.SharePath.String())
 	_, systemBusAddr := dbus.Address()
 	if entries, err := dbus.Parse([]byte(systemBusAddr)); err != nil {
@@ -125,11 +126,11 @@ func newContainer(s *hst.ContainerConfig, os sys.State, prefix string, uid, gid
 						// get parent dir of socket
 						dir := path.Dir(pair[1])
 						if dir == "." || dir == container.FHSRoot {
-							os.Printf("dbus socket %q is in an unusual location", pair[1])
+							k.verbosef("dbus socket %q is in an unusual location", pair[1])
 						}
 						hidePaths = append(hidePaths, dir)
 					} else {
-						os.Printf("dbus socket %q is not absolute", pair[1])
+						k.verbosef("dbus socket %q is not absolute", pair[1])
 					}
 				}
 			}
@@ -137,7 +138,7 @@ func newContainer(s *hst.ContainerConfig, os sys.State, prefix string, uid, gid
 	}
 	hidePathMatch := make([]bool, len(hidePaths))
 	for i := range hidePaths {
-		if err := evalSymlinks(os, &hidePaths[i]); err != nil {
+		if err := evalSymlinks(k, &hidePaths[i]); err != nil {
 			return nil, nil, err
 		}
 	}
@@ -156,7 +157,7 @@ func newContainer(s *hst.ContainerConfig, os sys.State, prefix string, uid, gid
 	// AutoRootOp is a collection of many BindMountOp internally
 	var autoRootEntries []fs.DirEntry
 	if autoroot != nil {
-		if d, err := os.ReadDir(autoroot.Source.String()); err != nil {
+		if d, err := k.readdir(autoroot.Source.String()); err != nil {
 			return nil, nil, err
 		} else {
 			// autoroot counter
@@ -192,7 +193,7 @@ func newContainer(s *hst.ContainerConfig, os sys.State, prefix string, uid, gid
 		}
 
 		hidePathSourceEval[i] = [2]string{a.String(), a.String()}
-		if err := evalSymlinks(os, &hidePathSourceEval[i][0]); err != nil {
+		if err := evalSymlinks(k, &hidePathSourceEval[i][0]); err != nil {
 			return nil, nil, err
 		}
 	}
@@ -208,7 +209,7 @@ func newContainer(s *hst.ContainerConfig, os sys.State, prefix string, uid, gid
 				return nil, nil, err
 			} else if ok {
 				hidePathMatch[i] = true
-				os.Printf("hiding path %q from %q", hidePaths[i], p[1])
+				k.verbosef("hiding path %q from %q", hidePaths[i], p[1])
 			}
 		}
 	}
@@ -239,12 +240,13 @@ func newContainer(s *hst.ContainerConfig, os sys.State, prefix string, uid, gid
 	return params, maps.Clone(s.Env), nil
 }
 
-func evalSymlinks(os sys.State, v *string) error {
+// evalSymlinks calls syscallDispatcher.evalSymlinks but discards errors unwrapping to [fs.ErrNotExist].
-	if p, err := os.EvalSymlinks(*v); err != nil {
+func evalSymlinks(k syscallDispatcher, v *string) error {
+	if p, err := k.evalSymlinks(*v); err != nil {
 		if !errors.Is(err, fs.ErrNotExist) {
 			return err
 		}
-		os.Printf("path %q does not yet exist", *v)
+		k.verbosef("path %q does not yet exist", *v)
 	} else {
 		*v = p
 	}

internal/app/dispatcher.go

@@ -0,0 +1,99 @@
+package app
+
+import (
+	"log"
+	"os"
+	"os/exec"
+	"os/user"
+	"path/filepath"
+
+	"hakurei.app/container"
+	"hakurei.app/internal"
+	"hakurei.app/internal/hlog"
+)
+
+// syscallDispatcher provides methods that make state-dependent system calls as part of their behaviour.
+type syscallDispatcher interface {
+	// new starts a goroutine with a new instance of syscallDispatcher.
+	// A syscallDispatcher must never be used in any goroutine other than the one owning it,
+	// just synchronising access is not enough, as this is for test instrumentation.
+	new(f func(k syscallDispatcher))
+
+	// getuid provides [os.Getuid].
+	getuid() int
+	// getgid provides [os.Getgid].
+	getgid() int
+	// lookupEnv provides [os.LookupEnv].
+	lookupEnv(key string) (string, bool)
+	// stat provides [os.Stat].
+	stat(name string) (os.FileInfo, error)
+	// readdir provides [os.ReadDir].
+	readdir(name string) ([]os.DirEntry, error)
+	// tempdir provides [os.TempDir].
+	tempdir() string
+
+	// evalSymlinks provides [filepath.EvalSymlinks].
+	evalSymlinks(path string) (string, error)
+
+	// lookPath provides exec.LookPath.
+	lookPath(file string) (string, error)
+
+	// lookupGroupId calls [user.LookupGroup] and returns the Gid field of the resulting [user.Group] struct.
+	lookupGroupId(name string) (string, error)
+
+	// cmdOutput provides the Output method of [exec.Cmd].
+	cmdOutput(cmd *exec.Cmd) ([]byte, error)
+
+	// overflowUid provides [container.OverflowUid].
+	overflowUid() int
+	// overflowGid provides [container.OverflowGid].
+	overflowGid() int
+
+	// mustHsuPath provides [internal.MustHsuPath].
+	mustHsuPath() string
+
+	// fatalf provides [log.Fatalf].
+	fatalf(format string, v ...any)
+
+	isVerbose() bool
+	verbose(v ...any)
+	verbosef(format string, v ...any)
+}
+
+// direct implements syscallDispatcher on the current kernel.
+type direct struct{}
+
+func (k direct) new(f func(k syscallDispatcher)) { go f(k) }
+
+func (direct) getuid() int                                { return os.Getuid() }
+func (direct) getgid() int                                { return os.Getgid() }
+func (direct) lookupEnv(key string) (string, bool)        { return os.LookupEnv(key) }
+func (direct) stat(name string) (os.FileInfo, error)      { return os.Stat(name) }
+func (direct) readdir(name string) ([]os.DirEntry, error) { return os.ReadDir(name) }
+func (direct) tempdir() string                            { return os.TempDir() }
+
+func (direct) evalSymlinks(path string) (string, error) { return filepath.EvalSymlinks(path) }
+
+func (direct) lookPath(file string) (string, error) { return exec.LookPath(file) }
+
+func (direct) lookupGroupId(name string) (gid string, err error) {
+	var group *user.Group
+	group, err = user.LookupGroup(name)
+	if group != nil {
+		gid = group.Gid
+	}
+	return
+}
+
+func (direct) cmdOutput(cmd *exec.Cmd) ([]byte, error) { return cmd.Output() }
+
+func (direct) overflowUid() int { return container.OverflowUid() }
+func (direct) overflowGid() int { return container.OverflowGid() }
+
+func (direct) mustHsuPath() string { return internal.MustHsuPath() }
+
+func (direct) fatalf(format string, v ...any) { log.Fatalf(format, v...) }
+
+func (k direct) isVerbose() bool                { return hlog.Load() }
+func (direct) verbose(v ...any)                 { hlog.Verbose(v...) }
+func (direct) verbosef(format string, v ...any) { hlog.Verbosef(format, v...) }

internal/app/errors.go

@@ -1,181 +0,0 @@
-package app
-
-import (
-	"errors"
-	"log"
-
-	"hakurei.app/internal/hlog"
-)
-
-func PrintRunStateErr(rs *RunState, runErr error) (code int) {
-	code = rs.ExitStatus()
-
-	if runErr != nil {
-		if rs.Time == nil {
-			hlog.PrintBaseError(runErr, "cannot start app:")
-		} else {
-			var e *hlog.BaseError
-			if !hlog.AsBaseError(runErr, &e) {
-				log.Println("wait failed:", runErr)
-			} else {
-				// Wait only returns either *app.ProcessError or *app.StateStoreError wrapped in a *app.BaseError
-				var se *StateStoreError
-				if !errors.As(runErr, &se) {
-					// does not need special handling
-					log.Print(e.Message())
-				} else {
-					// inner error are either unwrapped store errors
-					// or joined errors returned by *appSealTx revert
-					// wrapped in *app.BaseError
-					var ej RevertCompoundError
-					if !errors.As(se.InnerErr, &ej) {
-						// does not require special handling
-						log.Print(e.Message())
-					} else {
-						errs := ej.Unwrap()
-
-						// every error here is wrapped in *app.BaseError
-						for _, ei := range errs {
-							var eb *hlog.BaseError
-							if !errors.As(ei, &eb) {
-								// unreachable
-								log.Println("invalid error type returned by revert:", ei)
-							} else {
-								// print inner *app.BaseError message
-								log.Print(eb.Message())
-							}
-						}
-					}
-				}
-			}
-		}
-
-		if code == 0 {
-			code = 126
-		}
-	}
-
-	if rs.RevertErr != nil {
-		var stateStoreError *StateStoreError
-		if !errors.As(rs.RevertErr, &stateStoreError) || stateStoreError == nil {
-			hlog.PrintBaseError(rs.RevertErr, "generic fault during cleanup:")
-			goto out
-		}
-
-		if stateStoreError.Err != nil {
-			if len(stateStoreError.Err) == 2 {
-				if stateStoreError.Err[0] != nil {
-					if joinedErrs, ok := stateStoreError.Err[0].(interface{ Unwrap() []error }); !ok {
-						hlog.PrintBaseError(stateStoreError.Err[0], "generic fault during revert:")
-					} else {
-						for _, err := range joinedErrs.Unwrap() {
-							if err != nil {
-								hlog.PrintBaseError(err, "fault during revert:")
-							}
-						}
-					}
-				}
-				if stateStoreError.Err[1] != nil {
-					log.Printf("cannot close store: %v", stateStoreError.Err[1])
-				}
-			} else {
-				log.Printf("fault during cleanup: %v",
-					errors.Join(stateStoreError.Err...))
-			}
-		}
-
-		if stateStoreError.OpErr != nil {
-			log.Printf("blind revert due to store fault: %v",
-				stateStoreError.OpErr)
-		}
-
-		if stateStoreError.DoErr != nil {
-			hlog.PrintBaseError(stateStoreError.DoErr, "state store operation unsuccessful:")
-		}
-
-		if stateStoreError.Inner && stateStoreError.InnerErr != nil {
-			hlog.PrintBaseError(stateStoreError.InnerErr, "cannot destroy state entry:")
-		}
-
-	out:
-		if code == 0 {
-			code = 128
-		}
-	}
-	if rs.WaitErr != nil {
-		hlog.Verbosef("wait: %v", rs.WaitErr)
-	}
-	return
-}
-
-// StateStoreError is returned for a failed state save
-type StateStoreError struct {
-	// whether inner function was called
-	Inner bool
-	// returned by the Save/Destroy method of [state.Cursor]
-	InnerErr error
-	// returned by the Do method of [state.Store]
-	DoErr error
-	// stores an arbitrary store operation error
-	OpErr error
-	// stores arbitrary errors
-	Err []error
-}
-
-// save saves arbitrary errors in [StateStoreError] once.
-func (e *StateStoreError) save(errs ...error) {
-	if len(errs) == 0 || e.Err != nil {
-		panic("invalid call to save")
-	}
-	e.Err = errs
-}
-
-func (e *StateStoreError) equiv(a ...any) error {
-	if e.Inner && e.InnerErr == nil && e.DoErr == nil && e.OpErr == nil && errors.Join(e.Err...) == nil {
-		return nil
-	} else {
-		return hlog.WrapErrSuffix(e, a...)
-	}
-}
-
-func (e *StateStoreError) Error() string {
-	if e.Inner && e.InnerErr != nil {
-		return e.InnerErr.Error()
-	}
-	if e.DoErr != nil {
-		return e.DoErr.Error()
-	}
-	if e.OpErr != nil {
-		return e.OpErr.Error()
-	}
-	if err := errors.Join(e.Err...); err != nil {
-		return err.Error()
-	}
-
-	// equiv nullifies e for values where this is reached
-	panic("unreachable")
-}
-
-func (e *StateStoreError) Unwrap() (errs []error) {
-	errs = make([]error, 0, 3)
-	if e.InnerErr != nil {
-		errs = append(errs, e.InnerErr)
-	}
-	if e.DoErr != nil {
-		errs = append(errs, e.DoErr)
-	}
-	if e.OpErr != nil {
-		errs = append(errs, e.OpErr)
-	}
-	if err := errors.Join(e.Err...); err != nil {
-		errs = append(errs, err)
-	}
-	return
-}
-
-// A RevertCompoundError encapsulates errors returned by
-// the Revert method of [system.I].
-type RevertCompoundError interface {
-	Error() string
-	Unwrap() []error
-}

internal/app/export_linux_test.go

@@ -1,24 +0,0 @@
-package app
-
-import (
-	"hakurei.app/container"
-	"hakurei.app/internal/app/state"
-	"hakurei.app/internal/sys"
-	"hakurei.app/system"
-)
-
-func NewWithID(id state.ID, os sys.State) App {
-	a := new(app)
-	a.id = newID(&id)
-	a.sys = os
-	return a
-}
-
-func AppIParams(a App, sa SealedApp) (*system.I, *container.Params) {
-	v := a.(*app)
-	seal := sa.(*outcome)
-	if v.outcome != seal || v.id != seal.id {
-		panic("broken app/outcome link")
-	}
-	return seal.sys, seal.container
-}

internal/app/finalise.go

@@ -9,8 +9,7 @@ import (
 	"io"
 	"io/fs"
 	"os"
-	"path"
+	"os/user"
-	"regexp"
 	"slices"
 	"strconv"
 	"strings"
@@ -20,49 +19,20 @@ import (
 
 	"hakurei.app/container"
 	"hakurei.app/hst"
-	"hakurei.app/internal"
 	"hakurei.app/internal/app/state"
 	"hakurei.app/internal/hlog"
-	"hakurei.app/internal/sys"
 	"hakurei.app/system"
 	"hakurei.app/system/acl"
 	"hakurei.app/system/dbus"
 	"hakurei.app/system/wayland"
 )
 
-const (
+func newWithMessage(msg string) error { return newWithMessageError(msg, os.ErrInvalid) }
-	home  = "HOME"
+func newWithMessageError(msg string, err error) error {
-	shell = "SHELL"
+	return &hst.AppError{Step: "finalise", Err: err, Msg: msg}
+}
 
-	xdgConfigHome   = "XDG_CONFIG_HOME"
+// An outcome is the runnable state of a hakurei container via [hst.Config].
-	xdgRuntimeDir   = "XDG_RUNTIME_DIR"
-	xdgSessionClass = "XDG_SESSION_CLASS"
-	xdgSessionType  = "XDG_SESSION_TYPE"
-
-	term    = "TERM"
-	display = "DISPLAY"
-
-	pulseServer = "PULSE_SERVER"
-	pulseCookie = "PULSE_COOKIE"
-
-	dbusSessionBusAddress = "DBUS_SESSION_BUS_ADDRESS"
-	dbusSystemBusAddress  = "DBUS_SYSTEM_BUS_ADDRESS"
-)
-
-var (
-	ErrIdent = errors.New("invalid identity")
-	ErrName  = errors.New("invalid username")
-
-	ErrXDisplay = errors.New(display + " unset")
-
-	ErrPulseCookie = errors.New("pulse cookie not present")
-	ErrPulseSocket = errors.New("pulse socket not present")
-	ErrPulseMode   = errors.New("unexpected pulse socket mode")
-)
-
-var posixUsername = regexp.MustCompilePOSIX("^[a-z_]([A-Za-z0-9_-]{0,31}|[A-Za-z0-9_-]{0,30}\\$)$")
-
-// outcome stores copies of various parts of [hst.Config]
 type outcome struct {
 	// copied from initialising [app]
 	id *stringPair[state.ID]
@@ -83,8 +53,9 @@ type outcome struct {
 	container *container.Params
 	env       map[string]string
 	sync      *os.File
+	active    atomic.Bool
 
-	f atomic.Bool
+	syscallDispatcher
 }
 
 // shareHost holds optional share directory state that must not be accessed directly
@@ -136,8 +107,7 @@ func (share *shareHost) runtime() *container.Absolute {
 
 // hsuUser stores post-hsu credentials and metadata
 type hsuUser struct {
-	// identity
+	identity *stringPair[int]
-	aid *stringPair[int]
 	// target uid resolved by hid:aid
 	uid *stringPair[int]
 
@@ -150,59 +120,82 @@ type hsuUser struct {
 	username string
 }
 
-func (seal *outcome) finalise(ctx context.Context, sys sys.State, config *hst.Config) error {
+func (k *outcome) finalise(ctx context.Context, config *hst.Config) error {
-	if seal.ctx != nil {
+	const (
-		panic("finalise called twice")
+		home  = "HOME"
+		shell = "SHELL"
+
+		xdgConfigHome   = "XDG_CONFIG_HOME"
+		xdgRuntimeDir   = "XDG_RUNTIME_DIR"
+		xdgSessionClass = "XDG_SESSION_CLASS"
+		xdgSessionType  = "XDG_SESSION_TYPE"
+
+		term    = "TERM"
+		display = "DISPLAY"
+
+		pulseServer = "PULSE_SERVER"
+		pulseCookie = "PULSE_COOKIE"
+
+		dbusSessionBusAddress = "DBUS_SESSION_BUS_ADDRESS"
+		dbusSystemBusAddress  = "DBUS_SYSTEM_BUS_ADDRESS"
+	)
+
+	if ctx == nil {
+		// unreachable
+		panic("invalid call to finalise")
 	}
-	seal.ctx = ctx
+	if k.ctx != nil {
+		// unreachable
+		panic("attempting to finalise twice")
+	}
+	k.ctx = ctx
 
 	if config == nil {
-		return hlog.WrapErr(syscall.EINVAL, syscall.EINVAL.Error())
+		return newWithMessage("invalid configuration")
 	}
 	if config.Home == nil {
-		return hlog.WrapErr(os.ErrInvalid, "invalid path to home directory")
+		return newWithMessage("invalid path to home directory")
 	}
 
 	{
 		// encode initial configuration for state tracking
 		ct := new(bytes.Buffer)
 		if err := gob.NewEncoder(ct).Encode(config); err != nil {
-			return hlog.WrapErrSuffix(err,
+			return &hst.AppError{Step: "encode initial config", Err: err}
-				"cannot encode initial config:")
 		}
-		seal.ct = ct
+		k.ct = ct
 	}
 
-	// allowed aid range 0 to 9999, this is checked again in hsu
+	// allowed identity range 0 to 9999, this is checked again in hsu
 	if config.Identity < 0 || config.Identity > 9999 {
-		return hlog.WrapErr(ErrIdent,
+		return newWithMessage(fmt.Sprintf("identity %d out of range", config.Identity))
-			fmt.Sprintf("identity %d out of range", config.Identity))
 	}
 
-	seal.user = hsuUser{
+	k.user = hsuUser{
-		aid:      newInt(config.Identity),
+		identity: newInt(config.Identity),
 		home:     config.Home,
 		username: config.Username,
 	}
-	if seal.user.username == "" {
+
-		seal.user.username = "chronos"
+	hsu := Hsu{k: k}
-	} else if !posixUsername.MatchString(seal.user.username) ||
+	if k.user.username == "" {
-		len(seal.user.username) >= internal.Sysconf(internal.SC_LOGIN_NAME_MAX) {
+		k.user.username = "chronos"
-		return hlog.WrapErr(ErrName,
+	} else if !isValidUsername(k.user.username) {
-			fmt.Sprintf("invalid user name %q", seal.user.username))
+		return newWithMessage(fmt.Sprintf("invalid user name %q", k.user.username))
 	}
-	if u, err := sys.Uid(seal.user.aid.unwrap()); err != nil {
+	k.user.uid = newInt(HsuUid(hsu.MustID(), k.user.identity.unwrap()))
-		return err
+
-	} else {
+	k.user.supp = make([]string, len(config.Groups))
-		seal.user.uid = newInt(u)
-	}
-	seal.user.supp = make([]string, len(config.Groups))
 	for i, name := range config.Groups {
-		if g, err := sys.LookupGroup(name); err != nil {
+		if gid, err := k.lookupGroupId(name); err != nil {
-			return hlog.WrapErr(err,
+			var unknownGroupError user.UnknownGroupError
-				fmt.Sprintf("unknown group %q", name))
+			if errors.As(err, &unknownGroupError) {
+				return newWithMessageError(fmt.Sprintf("unknown group %q", name), unknownGroupError)
+			} else {
+				return &hst.AppError{Step: "look up group by name", Err: err}
+			}
 		} else {
-			seal.user.supp[i] = g.Gid
+			k.user.supp[i] = gid
 		}
 	}
 
@@ -212,7 +205,7 @@ func (seal *outcome) finalise(ctx context.Context, sys sys.State, config *hst.Co
 
 		if config.Shell == nil {
 			config.Shell = container.AbsFHSRoot.Append("bin", "sh")
-			s, _ := sys.LookupEnv(shell)
+			s, _ := k.lookupEnv(shell)
 			if a, err := container.NewAbs(s); err == nil {
 				config.Shell = a
 			}
@@ -221,10 +214,10 @@ func (seal *outcome) finalise(ctx context.Context, sys sys.State, config *hst.Co
 		// hsu clears the environment so resolve paths early
 		if config.Path == nil {
 			if len(config.Args) > 0 {
-				if p, err := sys.LookPath(config.Args[0]); err != nil {
+				if p, err := k.lookPath(config.Args[0]); err != nil {
-					return hlog.WrapErr(err, err.Error())
+					return &hst.AppError{Step: "look up executable file", Err: err}
 				} else if config.Path, err = container.NewAbs(p); err != nil {
-					return hlog.WrapErr(err, err.Error())
+					return newWithMessageError(err.Error(), err)
 				}
 			} else {
 				config.Path = config.Shell
@@ -239,7 +232,7 @@ func (seal *outcome) finalise(ctx context.Context, sys sys.State, config *hst.Co
 
 			Filesystem: []hst.FilesystemConfigJSON{
 				// autoroot, includes the home directory
-				{&hst.FSBind{
+				{FilesystemConfig: &hst.FSBind{
 					Target:  container.AbsFHSRoot,
 					Source:  container.AbsFHSRoot,
 					Write:   true,
@@ -257,7 +250,7 @@ func (seal *outcome) finalise(ctx context.Context, sys sys.State, config *hst.Co
 
 		// hide nscd from container if present
 		nscd := container.AbsFHSVar.Append("run/nscd")
-		if _, err := sys.Stat(nscd.String()); !errors.Is(err, fs.ErrNotExist) {
+		if _, err := k.stat(nscd.String()); !errors.Is(err, fs.ErrNotExist) {
 			conf.Filesystem = append(conf.Filesystem, hst.FilesystemConfigJSON{FilesystemConfig: &hst.FSEphemeral{Target: nscd}})
 		}
 
@@ -275,93 +268,95 @@ func (seal *outcome) finalise(ctx context.Context, sys sys.State, config *hst.Co
 
 	// late nil checks for pd behaviour
 	if config.Shell == nil {
-		return hlog.WrapErr(syscall.EINVAL, "invalid shell path")
+		return newWithMessage("invalid shell path")
 	}
 	if config.Path == nil {
-		return hlog.WrapErr(syscall.EINVAL, "invalid program path")
+		return newWithMessage("invalid program path")
 	}
 
+	// TODO(ophestra): revert this after params to shim
+	share := &shareHost{seal: k}
+	copyPaths(k.syscallDispatcher, &share.sc, hsu.MustID())
+
 	var mapuid, mapgid *stringPair[int]
 	{
 		var uid, gid int
 		var err error
-		seal.container, seal.env, err = newContainer(config.Container, sys, seal.id.String(), &uid, &gid)
+		k.container, k.env, err = newContainer(k, config.Container, k.id.String(), &share.sc, &uid, &gid)
-		seal.waitDelay = config.Container.WaitDelay
+		k.waitDelay = config.Container.WaitDelay
 		if err != nil {
-			return hlog.WrapErrSuffix(err,
+			return &hst.AppError{Step: "initialise container configuration", Err: err}
-				"cannot initialise container configuration:")
 		}
 		if len(config.Args) == 0 {
 			config.Args = []string{config.Path.String()}
 		}
-		seal.container.Path = config.Path
+		k.container.Path = config.Path
-		seal.container.Args = config.Args
+		k.container.Args = config.Args
 
 		mapuid = newInt(uid)
 		mapgid = newInt(gid)
-		if seal.env == nil {
+		if k.env == nil {
-			seal.env = make(map[string]string, 1<<6)
+			k.env = make(map[string]string, 1<<6)
 		}
 	}
 
 	// inner XDG_RUNTIME_DIR default formatting of `/run/user/%d` as mapped uid
 	innerRuntimeDir := container.AbsFHSRunUser.Append(mapuid.String())
-	seal.env[xdgRuntimeDir] = innerRuntimeDir.String()
+	k.env[xdgRuntimeDir] = innerRuntimeDir.String()
-	seal.env[xdgSessionClass] = "user"
+	k.env[xdgSessionClass] = "user"
-	seal.env[xdgSessionType] = "tty"
+	k.env[xdgSessionType] = "tty"
 
-	share := &shareHost{seal: seal, sc: sys.Paths()}
+	k.runDirPath = share.sc.RunDirPath
-	seal.runDirPath = share.sc.RunDirPath
+	k.sys = system.New(k.ctx, k.user.uid.unwrap())
-	seal.sys = system.New(seal.user.uid.unwrap())
+	k.sys.Ensure(share.sc.SharePath.String(), 0711)
-	seal.sys.Ensure(share.sc.SharePath.String(), 0711)
 
 	{
 		runtimeDir := share.sc.SharePath.Append("runtime")
-		seal.sys.Ensure(runtimeDir.String(), 0700)
+		k.sys.Ensure(runtimeDir.String(), 0700)
-		seal.sys.UpdatePermType(system.User, runtimeDir.String(), acl.Execute)
+		k.sys.UpdatePermType(system.User, runtimeDir.String(), acl.Execute)
-		runtimeDirInst := runtimeDir.Append(seal.user.aid.String())
+		runtimeDirInst := runtimeDir.Append(k.user.identity.String())
-		seal.sys.Ensure(runtimeDirInst.String(), 0700)
+		k.sys.Ensure(runtimeDirInst.String(), 0700)
-		seal.sys.UpdatePermType(system.User, runtimeDirInst.String(), acl.Read, acl.Write, acl.Execute)
+		k.sys.UpdatePermType(system.User, runtimeDirInst.String(), acl.Read, acl.Write, acl.Execute)
-		seal.container.Tmpfs(container.AbsFHSRunUser, 1<<12, 0755)
+		k.container.Tmpfs(container.AbsFHSRunUser, 1<<12, 0755)
-		seal.container.Bind(runtimeDirInst, innerRuntimeDir, container.BindWritable)
+		k.container.Bind(runtimeDirInst, innerRuntimeDir, container.BindWritable)
 	}
 
 	{
 		tmpdir := share.sc.SharePath.Append("tmpdir")
-		seal.sys.Ensure(tmpdir.String(), 0700)
+		k.sys.Ensure(tmpdir.String(), 0700)
-		seal.sys.UpdatePermType(system.User, tmpdir.String(), acl.Execute)
+		k.sys.UpdatePermType(system.User, tmpdir.String(), acl.Execute)
-		tmpdirInst := tmpdir.Append(seal.user.aid.String())
+		tmpdirInst := tmpdir.Append(k.user.identity.String())
-		seal.sys.Ensure(tmpdirInst.String(), 01700)
+		k.sys.Ensure(tmpdirInst.String(), 01700)
-		seal.sys.UpdatePermType(system.User, tmpdirInst.String(), acl.Read, acl.Write, acl.Execute)
+		k.sys.UpdatePermType(system.User, tmpdirInst.String(), acl.Read, acl.Write, acl.Execute)
 		// mount inner /tmp from share so it shares persistence and storage behaviour of host /tmp
-		seal.container.Bind(tmpdirInst, container.AbsFHSTmp, container.BindWritable)
+		k.container.Bind(tmpdirInst, container.AbsFHSTmp, container.BindWritable)
 	}
 
 	{
 		username := "chronos"
-		if seal.user.username != "" {
+		if k.user.username != "" {
-			username = seal.user.username
+			username = k.user.username
 		}
-		seal.container.Dir = seal.user.home
+		k.container.Dir = k.user.home
-		seal.env["HOME"] = seal.user.home.String()
+		k.env["HOME"] = k.user.home.String()
-		seal.env["USER"] = username
+		k.env["USER"] = username
-		seal.env[shell] = config.Shell.String()
+		k.env[shell] = config.Shell.String()
 
-		seal.container.Place(container.AbsFHSEtc.Append("passwd"),
+		k.container.Place(container.AbsFHSEtc.Append("passwd"),
-			[]byte(username+":x:"+mapuid.String()+":"+mapgid.String()+":Hakurei:"+seal.user.home.String()+":"+config.Shell.String()+"\n"))
+			[]byte(username+":x:"+mapuid.String()+":"+mapgid.String()+":Hakurei:"+k.user.home.String()+":"+config.Shell.String()+"\n"))
-		seal.container.Place(container.AbsFHSEtc.Append("group"),
+		k.container.Place(container.AbsFHSEtc.Append("group"),
 			[]byte("hakurei:x:"+mapgid.String()+":\n"))
 	}
 
 	// pass TERM for proper terminal I/O in initial process
-	if t, ok := sys.LookupEnv(term); ok {
+	if t, ok := k.lookupEnv(term); ok {
-		seal.env[term] = t
+		k.env[term] = t
 	}
 
 	if config.Enablements.Unwrap()&system.EWayland != 0 {
 		// outer wayland socket (usually `/run/user/%d/wayland-%d`)
 		var socketPath *container.Absolute
-		if name, ok := sys.LookupEnv(wayland.WaylandDisplay); !ok {
+		if name, ok := k.lookupEnv(wayland.WaylandDisplay); !ok {
 			hlog.Verbose(wayland.WaylandDisplay + " is not set, assuming " + wayland.FallbackName)
 			socketPath = share.sc.RuntimePath.Append(wayland.FallbackName)
 		} else if a, err := container.NewAbs(name); err != nil {
@@ -371,30 +366,29 @@ func (seal *outcome) finalise(ctx context.Context, sys sys.State, config *hst.Co
 		}
 
 		innerPath := innerRuntimeDir.Append(wayland.FallbackName)
-		seal.env[wayland.WaylandDisplay] = wayland.FallbackName
+		k.env[wayland.WaylandDisplay] = wayland.FallbackName
 
 		if !config.DirectWayland { // set up security-context-v1
 			appID := config.ID
 			if appID == "" {
 				// use instance ID in case app id is not set
-				appID = "app.hakurei." + seal.id.String()
+				appID = "app.hakurei." + k.id.String()
 			}
 			// downstream socket paths
 			outerPath := share.instance().Append("wayland")
-			seal.sys.Wayland(&seal.sync, outerPath.String(), socketPath.String(), appID, seal.id.String())
+			k.sys.Wayland(&k.sync, outerPath.String(), socketPath.String(), appID, k.id.String())
-			seal.container.Bind(outerPath, innerPath, 0)
+			k.container.Bind(outerPath, innerPath, 0)
 		} else { // bind mount wayland socket (insecure)
 			hlog.Verbose("direct wayland access, PROCEED WITH CAUTION")
 			share.ensureRuntimeDir()
-			seal.container.Bind(socketPath, innerPath, 0)
+			k.container.Bind(socketPath, innerPath, 0)
-			seal.sys.UpdatePermType(system.EWayland, socketPath.String(), acl.Read, acl.Write, acl.Execute)
+			k.sys.UpdatePermType(system.EWayland, socketPath.String(), acl.Read, acl.Write, acl.Execute)
 		}
 	}
 
 	if config.Enablements.Unwrap()&system.EX11 != 0 {
-		if d, ok := sys.LookupEnv(display); !ok {
+		if d, ok := k.lookupEnv(display); !ok {
-			return hlog.WrapErr(ErrXDisplay,
+			return newWithMessage("DISPLAY is not set")
-				"DISPLAY is not set")
 		} else {
 			socketDir := container.AbsFHSTmp.Append(".X11-unix")
 
@@ -411,20 +405,21 @@ func (seal *outcome) finalise(ctx context.Context, sys sys.State, config *hst.Co
 				}
 			}
 			if socketPath != nil {
-				if _, err := sys.Stat(socketPath.String()); err != nil {
+				if _, err := k.stat(socketPath.String()); err != nil {
 					if !errors.Is(err, fs.ErrNotExist) {
-						return hlog.WrapErrSuffix(err,
+						return &hst.AppError{Step: fmt.Sprintf("access X11 socket %q", socketPath), Err: err}
-							fmt.Sprintf("cannot access X11 socket %q:", socketPath))
 					}
 				} else {
-					seal.sys.UpdatePermType(system.EX11, socketPath.String(), acl.Read, acl.Write, acl.Execute)
+					k.sys.UpdatePermType(system.EX11, socketPath.String(), acl.Read, acl.Write, acl.Execute)
-					d = "unix:" + socketPath.String()
+					if !config.Container.HostAbstract {
+						d = "unix:" + socketPath.String()
+					}
 				}
 			}
 
-			seal.sys.ChangeHosts("#" + seal.user.uid.String())
+			k.sys.ChangeHosts("#" + k.user.uid.String())
-			seal.env[display] = d
+			k.env[display] = d
-			seal.container.Bind(socketDir, socketDir, 0)
+			k.container.Bind(socketDir, socketDir, 0)
 		}
 	}
 
@@ -434,46 +429,101 @@ func (seal *outcome) finalise(ctx context.Context, sys sys.State, config *hst.Co
 		// PulseAudio socket (usually `/run/user/%d/pulse/native`)
 		pulseSocket := pulseRuntimeDir.Append("native")
 
-		if _, err := sys.Stat(pulseRuntimeDir.String()); err != nil {
+		if _, err := k.stat(pulseRuntimeDir.String()); err != nil {
 			if !errors.Is(err, fs.ErrNotExist) {
-				return hlog.WrapErrSuffix(err,
+				return &hst.AppError{Step: fmt.Sprintf("access PulseAudio directory %q", pulseRuntimeDir), Err: err}
-					fmt.Sprintf("cannot access PulseAudio directory %q:", pulseRuntimeDir))
 			}
-			return hlog.WrapErr(ErrPulseSocket,
+			return newWithMessage(fmt.Sprintf("PulseAudio directory %q not found", pulseRuntimeDir))
-				fmt.Sprintf("PulseAudio directory %q not found", pulseRuntimeDir))
 		}
 
-		if s, err := sys.Stat(pulseSocket.String()); err != nil {
+		if s, err := k.stat(pulseSocket.String()); err != nil {
 			if !errors.Is(err, fs.ErrNotExist) {
-				return hlog.WrapErrSuffix(err,
+				return &hst.AppError{Step: fmt.Sprintf("access PulseAudio socket %q", pulseSocket), Err: err}
-					fmt.Sprintf("cannot access PulseAudio socket %q:", pulseSocket))
 			}
-			return hlog.WrapErr(ErrPulseSocket,
+			return newWithMessage(fmt.Sprintf("PulseAudio directory %q found but socket does not exist", pulseRuntimeDir))
-				fmt.Sprintf("PulseAudio directory %q found but socket does not exist", pulseRuntimeDir))
 		} else {
 			if m := s.Mode(); m&0o006 != 0o006 {
-				return hlog.WrapErr(ErrPulseMode,
+				return newWithMessage(fmt.Sprintf("unexpected permissions on %q: %s", pulseSocket, m))
-					fmt.Sprintf("unexpected permissions on %q:", pulseSocket), m)
 			}
 		}
 
 		// hard link pulse socket into target-executable share
 		innerPulseRuntimeDir := share.runtime().Append("pulse")
 		innerPulseSocket := innerRuntimeDir.Append("pulse", "native")
-		seal.sys.Link(pulseSocket.String(), innerPulseRuntimeDir.String())
+		k.sys.Link(pulseSocket.String(), innerPulseRuntimeDir.String())
-		seal.container.Bind(innerPulseRuntimeDir, innerPulseSocket, 0)
+		k.container.Bind(innerPulseRuntimeDir, innerPulseSocket, 0)
-		seal.env[pulseServer] = "unix:" + innerPulseSocket.String()
+		k.env[pulseServer] = "unix:" + innerPulseSocket.String()
 
 		// publish current user's pulse cookie for target user
-		if src, err := discoverPulseCookie(sys); err != nil {
+		var paCookiePath *container.Absolute
-			// not fatal
+		{
-			hlog.Verbose(strings.TrimSpace(err.(*hlog.BaseError).Message()))
+			const paLocateStep = "locate PulseAudio cookie"
-		} else {
+
+			// from environment
+			if p, ok := k.lookupEnv(pulseCookie); ok {
+				if a, err := container.NewAbs(p); err != nil {
+					return &hst.AppError{Step: paLocateStep, Err: err}
+				} else {
+					// this takes precedence, do not verify whether the file is accessible
+					paCookiePath = a
+					goto out
+				}
+			}
+
+			// $HOME/.pulse-cookie
+			if p, ok := k.lookupEnv(home); ok {
+				if a, err := container.NewAbs(p); err != nil {
+					return &hst.AppError{Step: paLocateStep, Err: err}
+				} else {
+					paCookiePath = a.Append(".pulse-cookie")
+				}
+
+				if s, err := k.stat(paCookiePath.String()); err != nil {
+					paCookiePath = nil
+					if !errors.Is(err, fs.ErrNotExist) {
+						return &hst.AppError{Step: "access PulseAudio cookie", Err: err}
+					}
+					// fallthrough
+				} else if s.IsDir() {
+					paCookiePath = nil
+				} else {
+					goto out
+				}
+			}
+
+			// $XDG_CONFIG_HOME/pulse/cookie
+			if p, ok := k.lookupEnv(xdgConfigHome); ok {
+				if a, err := container.NewAbs(p); err != nil {
+					return &hst.AppError{Step: paLocateStep, Err: err}
+				} else {
+					paCookiePath = a.Append("pulse", "cookie")
+				}
+				if s, err := k.stat(paCookiePath.String()); err != nil {
+					paCookiePath = nil
+					if !errors.Is(err, fs.ErrNotExist) {
+						return &hst.AppError{Step: "access PulseAudio cookie", Err: err}
+					}
+					// fallthrough
+				} else if s.IsDir() {
+					paCookiePath = nil
+				} else {
+					goto out
+				}
+			}
+		out:
+		}
+
+		if paCookiePath != nil {
 			innerDst := hst.AbsTmp.Append("/pulse-cookie")
-			seal.env[pulseCookie] = innerDst.String()
+			k.env[pulseCookie] = innerDst.String()
 			var payload *[]byte
-			seal.container.PlaceP(innerDst, &payload)
+			k.container.PlaceP(innerDst, &payload)
-			seal.sys.CopyFile(payload, src, 256, 256)
+			k.sys.CopyFile(payload, paCookiePath.String(), 256, 256)
+		} else {
+			hlog.Verbose("cannot locate PulseAudio cookie (tried " +
+				"$PULSE_COOKIE, " +
+				"$XDG_CONFIG_HOME/pulse/cookie, " +
+				"$HOME/.pulse-cookie)")
 		}
 	}
 
@@ -487,30 +537,30 @@ func (seal *outcome) finalise(ctx context.Context, sys sys.State, config *hst.Co
 		sessionPath, systemPath := share.instance().Append("bus"), share.instance().Append("system_bus_socket")
 
 		// configure dbus proxy
-		if f, err := seal.sys.ProxyDBus(
+		if f, err := k.sys.ProxyDBus(
 			config.SessionBus, config.SystemBus,
 			sessionPath.String(), systemPath.String(),
 		); err != nil {
 			return err
 		} else {
-			seal.dbusMsg = f
+			k.dbusMsg = f
 		}
 
 		// share proxy sockets
 		sessionInner := innerRuntimeDir.Append("bus")
-		seal.env[dbusSessionBusAddress] = "unix:path=" + sessionInner.String()
+		k.env[dbusSessionBusAddress] = "unix:path=" + sessionInner.String()
-		seal.container.Bind(sessionPath, sessionInner, 0)
+		k.container.Bind(sessionPath, sessionInner, 0)
-		seal.sys.UpdatePerm(sessionPath.String(), acl.Read, acl.Write)
+		k.sys.UpdatePerm(sessionPath.String(), acl.Read, acl.Write)
 		if config.SystemBus != nil {
 			systemInner := container.AbsFHSRun.Append("dbus/system_bus_socket")
-			seal.env[dbusSystemBusAddress] = "unix:path=" + systemInner.String()
+			k.env[dbusSystemBusAddress] = "unix:path=" + systemInner.String()
-			seal.container.Bind(systemPath, systemInner, 0)
+			k.container.Bind(systemPath, systemInner, 0)
-			seal.sys.UpdatePerm(systemPath.String(), acl.Read, acl.Write)
+			k.sys.UpdatePerm(systemPath.String(), acl.Read, acl.Write)
 		}
 	}
 
 	// mount root read-only as the final setup Op
-	seal.container.Remount(container.AbsFHSRoot, syscall.MS_RDONLY)
+	k.container.Remount(container.AbsFHSRoot, syscall.MS_RDONLY)
 
 	// append ExtraPerms last
 	for _, p := range config.ExtraPerms {
@@ -519,7 +569,7 @@ func (seal *outcome) finalise(ctx context.Context, sys sys.State, config *hst.Co
 		}
 
 		if p.Ensure {
-			seal.sys.Ensure(p.Path.String(), 0700)
+			k.sys.Ensure(p.Path.String(), 0700)
 		}
 
 		perms := make(acl.Perms, 0, 3)
@@ -532,63 +582,24 @@ func (seal *outcome) finalise(ctx context.Context, sys sys.State, config *hst.Co
 		if p.Execute {
 			perms = append(perms, acl.Execute)
 		}
-		seal.sys.UpdatePermType(system.User, p.Path.String(), perms...)
+		k.sys.UpdatePermType(system.User, p.Path.String(), perms...)
 	}
 
 	// flatten and sort env for deterministic behaviour
-	seal.container.Env = make([]string, 0, len(seal.env))
+	k.container.Env = make([]string, 0, len(k.env))
-	for k, v := range seal.env {
+	for key, value := range k.env {
-		if strings.IndexByte(k, '=') != -1 {
+		if strings.IndexByte(key, '=') != -1 {
-			return hlog.WrapErr(syscall.EINVAL,
+			return &hst.AppError{Step: "flatten environment", Err: syscall.EINVAL,
-				fmt.Sprintf("invalid environment variable %s", k))
+				Msg: fmt.Sprintf("invalid environment variable %s", key)}
 		}
-		seal.container.Env = append(seal.container.Env, k+"="+v)
+		k.container.Env = append(k.container.Env, key+"="+value)
 	}
-	slices.Sort(seal.container.Env)
+	slices.Sort(k.container.Env)
 
 	if hlog.Load() {
 		hlog.Verbosef("created application seal for uid %s (%s) groups: %v, argv: %s, ops: %d",
-			seal.user.uid, seal.user.username, config.Groups, seal.container.Args, len(*seal.container.Ops))
+			k.user.uid, k.user.username, config.Groups, k.container.Args, len(*k.container.Ops))
 	}
 
 	return nil
 }
-
-// discoverPulseCookie attempts various standard methods to discover the current user's PulseAudio authentication cookie
-func discoverPulseCookie(sys sys.State) (string, error) {
-	if p, ok := sys.LookupEnv(pulseCookie); ok {
-		return p, nil
-	}
-
-	// dotfile $HOME/.pulse-cookie
-	if p, ok := sys.LookupEnv(home); ok {
-		p = path.Join(p, ".pulse-cookie")
-		if s, err := sys.Stat(p); err != nil {
-			if !errors.Is(err, fs.ErrNotExist) {
-				return p, hlog.WrapErrSuffix(err,
-					fmt.Sprintf("cannot access PulseAudio cookie %q:", p))
-			}
-			// not found, try next method
-		} else if !s.IsDir() {
-			return p, nil
-		}
-	}
-
-	// $XDG_CONFIG_HOME/pulse/cookie
-	if p, ok := sys.LookupEnv(xdgConfigHome); ok {
-		p = path.Join(p, "pulse", "cookie")
-		if s, err := sys.Stat(p); err != nil {
-			if !errors.Is(err, fs.ErrNotExist) {
-				return p, hlog.WrapErrSuffix(err,
-					fmt.Sprintf("cannot access PulseAudio cookie %q:", p))
-			}
-			// not found, try next method
-		} else if !s.IsDir() {
-			return p, nil
-		}
-	}
-
-	return "", hlog.WrapErr(ErrPulseCookie,
-		fmt.Sprintf("cannot locate PulseAudio cookie (tried $%s, $%s/pulse/cookie, $%s/.pulse-cookie)",
-			pulseCookie, xdgConfigHome, home))
-}

internal/app/hsu.go

@@ -0,0 +1,96 @@
+package app
+
+import (
+	"errors"
+	"fmt"
+	"log"
+	"os"
+	"os/exec"
+	"strconv"
+	"sync"
+
+	"hakurei.app/container"
+	"hakurei.app/hst"
+	"hakurei.app/internal/hlog"
+)
+
+// Hsu caches responses from cmd/hsu.
+type Hsu struct {
+	idOnce sync.Once
+	idErr  error
+	id     int
+
+	kOnce sync.Once
+	k     syscallDispatcher
+}
+
+var ErrHsuAccess = errors.New("current user is not in the hsurc file")
+
+// ensureDispatcher ensures Hsu.k is not nil.
+func (h *Hsu) ensureDispatcher() {
+	h.kOnce.Do(func() {
+		if h.k == nil {
+			h.k = direct{}
+		}
+	})
+}
+
+// ID returns the current user hsurc identifier. ErrHsuAccess is returned if the current user is not in hsurc.
+func (h *Hsu) ID() (int, error) {
+	h.ensureDispatcher()
+	h.idOnce.Do(func() {
+		h.id = -1
+		hsuPath := h.k.mustHsuPath()
+
+		cmd := exec.Command(hsuPath)
+		cmd.Path = hsuPath
+		cmd.Stderr = os.Stderr // pass through fatal messages
+		cmd.Env = make([]string, 0)
+		cmd.Dir = container.FHSRoot
+		var (
+			p         []byte
+			exitError *exec.ExitError
+		)
+
+		const step = "obtain uid from hsu"
+		if p, h.idErr = h.k.cmdOutput(cmd); h.idErr == nil {
+			h.id, h.idErr = strconv.Atoi(string(p))
+			if h.idErr != nil {
+				h.idErr = &hst.AppError{Step: step, Err: h.idErr, Msg: "invalid uid string from hsu"}
+			}
+		} else if errors.As(h.idErr, &exitError) && exitError != nil && exitError.ExitCode() == 1 {
+			// hsu prints an error message in this case
+			h.idErr = &hst.AppError{Step: step, Err: ErrHsuAccess}
+		} else if os.IsNotExist(h.idErr) {
+			h.idErr = &hst.AppError{Step: step, Err: os.ErrNotExist,
+				Msg: fmt.Sprintf("the setuid helper is missing: %s", hsuPath)}
+		}
+	})
+
+	return h.id, h.idErr
+}
+
+// MustID calls [Hsu.ID] and terminates on error.
+func (h *Hsu) MustID() int {
+	id, err := h.ID()
+	if err == nil {
+		return id
+	}
+
+	const fallback = "cannot retrieve user id from setuid wrapper:"
+	if errors.Is(err, ErrHsuAccess) {
+		hlog.Verbose("*"+fallback, err)
+		os.Exit(1)
+		return -0xdeadbeef
+	} else if m, ok := container.GetErrorMessage(err); ok {
+		log.Fatal(m)
+		return -0xdeadbeef
+	} else {
+		log.Fatalln(fallback, err)
+		return -0xdeadbeef
+	}
+}
+
+// HsuUid returns target uid for the stable hsu uid format.
+// No bounds check is performed, a value retrieved from hsu is expected.
+func HsuUid(id, identity int) int { return 1000000 + id*10000 + identity }

internal/app/paths.go

@@ -0,0 +1,36 @@
+package app
+
+import (
+	"strconv"
+
+	"hakurei.app/container"
+	"hakurei.app/hst"
+)
+
+// CopyPaths populates a [hst.Paths] struct.
+func CopyPaths(v *hst.Paths, userid int) { copyPaths(direct{}, v, userid) }
+
+// copyPaths populates a [hst.Paths] struct.
+func copyPaths(k syscallDispatcher, v *hst.Paths, userid int) {
+	const xdgRuntimeDir = "XDG_RUNTIME_DIR"
+
+	if tempDir, err := container.NewAbs(k.tempdir()); err != nil {
+		k.fatalf("invalid TMPDIR: %v", err)
+	} else {
+		v.TempDir = tempDir
+	}
+
+	v.SharePath = v.TempDir.Append("hakurei." + strconv.Itoa(userid))
+	k.verbosef("process share directory at %q", v.SharePath)
+
+	r, _ := k.lookupEnv(xdgRuntimeDir)
+	if a, err := container.NewAbs(r); err != nil {
+		// fall back to path in share since hakurei has no hard XDG dependency
+		v.RunDirPath = v.SharePath.Append("run")
+		v.RuntimePath = v.RunDirPath.Append("compat")
+	} else {
+		v.RuntimePath = a
+		v.RunDirPath = v.RuntimePath.Append("hakurei")
+	}
+	k.verbosef("runtime directory at %q", v.RunDirPath)
+}

internal/app/process.go

@@ -0,0 +1,339 @@
+package app
+
+import (
+	"context"
+	"encoding/gob"
+	"errors"
+	"log"
+	"os"
+	"os/exec"
+	"strconv"
+	"strings"
+	"syscall"
+	"time"
+
+	"hakurei.app/container"
+	"hakurei.app/internal"
+	"hakurei.app/internal/app/state"
+	"hakurei.app/internal/hlog"
+	"hakurei.app/system"
+)
+
+// duration to wait for shim to exit, after container WaitDelay has elapsed.
+const shimWaitTimeout = 5 * time.Second
+
+// mainState holds persistent state bound to outcome.main.
+type mainState struct {
+	// done is whether beforeExit has been called already.
+	done bool
+
+	// Time is the exact point in time where the process was created.
+	// Location must be set to UTC.
+	//
+	// Time is nil if no process was ever created.
+	Time *time.Time
+
+	store   state.Store
+	cancel  context.CancelFunc
+	cmd     *exec.Cmd
+	cmdWait chan error
+
+	k *outcome
+	uintptr
+}
+
+const (
+	// mainNeedsRevert indicates the call to Commit has succeeded.
+	mainNeedsRevert uintptr = 1 << iota
+	// mainNeedsDestroy indicates the instance state entry is present in the store.
+	mainNeedsDestroy
+)
+
+// beforeExit must be called immediately before a call to [os.Exit].
+func (ms mainState) beforeExit(isFault bool) {
+	if ms.done {
+		panic("attempting to call beforeExit twice")
+	}
+	ms.done = true
+	defer hlog.BeforeExit()
+
+	if isFault && ms.cancel != nil {
+		ms.cancel()
+	}
+
+	var hasErr bool
+	// updates hasErr but does not terminate
+	perror := func(err error, message string) {
+		hasErr = true
+		printMessageError("cannot "+message+":", err)
+	}
+	exitCode := 1
+	defer func() {
+		if hasErr {
+			os.Exit(exitCode)
+		}
+	}()
+
+	// this also handles wait for a non-fault termination
+	if ms.cmd != nil && ms.cmdWait != nil {
+		waitDone := make(chan struct{})
+		// TODO(ophestra): enforce this limit early so it does not have to be done twice
+		shimTimeoutCompensated := shimWaitTimeout
+		if ms.k.waitDelay > MaxShimWaitDelay {
+			shimTimeoutCompensated += MaxShimWaitDelay
+		} else {
+			shimTimeoutCompensated += ms.k.waitDelay
+		}
+		// this ties waitDone to ctx with the additional compensated timeout duration
+		go func() { <-ms.k.ctx.Done(); time.Sleep(shimTimeoutCompensated); close(waitDone) }()
+
+		select {
+		case err := <-ms.cmdWait:
+			wstatus, ok := ms.cmd.ProcessState.Sys().(syscall.WaitStatus)
+			if ok {
+				if v := wstatus.ExitStatus(); v != 0 {
+					hasErr = true
+					exitCode = v
+				}
+			}
+
+			if hlog.Load() {
+				if !ok {
+					if err != nil {
+						hlog.Verbosef("wait: %v", err)
+					}
+				} else {
+					switch {
+					case wstatus.Exited():
+						hlog.Verbosef("process %d exited with code %d", ms.cmd.Process.Pid, wstatus.ExitStatus())
+
+					case wstatus.CoreDump():
+						hlog.Verbosef("process %d dumped core", ms.cmd.Process.Pid)
+
+					case wstatus.Signaled():
+						hlog.Verbosef("process %d got %s", ms.cmd.Process.Pid, wstatus.Signal())
+
+					default:
+						hlog.Verbosef("process %d exited with status %#x", ms.cmd.Process.Pid, wstatus)
+					}
+				}
+			}
+
+		case <-waitDone:
+			hlog.Resume()
+			// this is only reachable when shim did not exit within shimWaitTimeout, after its WaitDelay has elapsed.
+			// This is different from the container failing to terminate within its timeout period, as that is enforced
+			// by the shim. This path is instead reached when there is a lockup in shim preventing it from completing.
+			log.Printf("process %d did not terminate", ms.cmd.Process.Pid)
+		}
+
+		hlog.Resume()
+		if ms.k.sync != nil {
+			if err := ms.k.sync.Close(); err != nil {
+				perror(err, "close wayland security context")
+			}
+		}
+		if ms.k.dbusMsg != nil {
+			ms.k.dbusMsg()
+		}
+	}
+
+	if ms.uintptr&mainNeedsRevert != 0 {
+		if ok, err := ms.store.Do(ms.k.user.identity.unwrap(), func(c state.Cursor) {
+			if ms.uintptr&mainNeedsDestroy != 0 {
+				if err := c.Destroy(ms.k.id.unwrap()); err != nil {
+					perror(err, "destroy state entry")
+				}
+			}
+
+			var rt system.Enablement
+			if states, err := c.Load(); err != nil {
+				// it is impossible to continue from this point;
+				// revert per-process state here to limit damage
+				ec := system.Process
+				if revertErr := ms.k.sys.Revert((*system.Criteria)(&ec)); revertErr != nil {
+					var joinError interface {
+						Unwrap() []error
+						error
+					}
+					if !errors.As(revertErr, &joinError) || joinError == nil {
+						perror(revertErr, "revert system setup")
+					} else {
+						for _, v := range joinError.Unwrap() {
+							perror(v, "revert system setup step")
+						}
+					}
+				}
+				perror(err, "load instance states")
+			} else {
+				ec := system.Process
+				if l := len(states); l == 0 {
+					ec |= system.User
+				} else {
+					hlog.Verbosef("found %d instances, cleaning up without user-scoped operations", l)
+				}
+
+				// accumulate enablements of remaining launchers
+				for i, s := range states {
+					if s.Config != nil {
+						rt |= s.Config.Enablements.Unwrap()
+					} else {
+						log.Printf("state entry %d does not contain config", i)
+					}
+				}
+
+				ec |= rt ^ (system.EWayland | system.EX11 | system.EDBus | system.EPulse)
+				if hlog.Load() {
+					if ec > 0 {
+						hlog.Verbose("reverting operations scope", system.TypeString(ec))
+					}
+				}
+
+				if err = ms.k.sys.Revert((*system.Criteria)(&ec)); err != nil {
+					perror(err, "revert system setup")
+				}
+			}
+		}); err != nil {
+			if ok {
+				perror(err, "unlock state store")
+			} else {
+				perror(err, "open state store")
+			}
+		}
+	} else if ms.uintptr&mainNeedsDestroy != 0 {
+		panic("unreachable")
+	}
+
+	if ms.store != nil {
+		if err := ms.store.Close(); err != nil {
+			perror(err, "close state store")
+		}
+	}
+}
+
+// fatal calls printMessageError, performs necessary cleanup, followed by a call to [os.Exit](1).
+func (ms mainState) fatal(fallback string, ferr error) {
+	printMessageError(fallback, ferr)
+	ms.beforeExit(true)
+	os.Exit(1)
+}
+
+// main carries out outcome and terminates. main does not return.
+func (k *outcome) main() {
+	if !k.active.CompareAndSwap(false, true) {
+		panic("outcome: attempted to run twice")
+	}
+
+	// read comp value early for early failure
+	hsuPath := internal.MustHsuPath()
+
+	// ms.beforeExit required beyond this point
+	ms := &mainState{k: k}
+
+	if err := k.sys.Commit(); err != nil {
+		ms.fatal("cannot commit system setup:", err)
+	}
+	ms.uintptr |= mainNeedsRevert
+	ms.store = state.NewMulti(k.runDirPath.String())
+
+	ctx, cancel := context.WithCancel(k.ctx)
+	defer cancel()
+	ms.cancel = cancel
+
+	ms.cmd = exec.CommandContext(ctx, hsuPath)
+	ms.cmd.Stdin, ms.cmd.Stdout, ms.cmd.Stderr = os.Stdin, os.Stdout, os.Stderr
+	ms.cmd.Dir = container.FHSRoot // container init enters final working directory
+	// shim runs in the same session as monitor; see shim.go for behaviour
+	ms.cmd.Cancel = func() error { return ms.cmd.Process.Signal(syscall.SIGCONT) }
+
+	var e *gob.Encoder
+	if fd, encoder, err := container.Setup(&ms.cmd.ExtraFiles); err != nil {
+		ms.fatal("cannot create shim setup pipe:", err)
+	} else {
+		e = encoder
+		ms.cmd.Env = []string{
+			// passed through to shim by hsu
+			shimEnv + "=" + strconv.Itoa(fd),
+			// interpreted by hsu
+			"HAKUREI_IDENTITY=" + k.user.identity.String(),
+		}
+	}
+
+	if len(k.user.supp) > 0 {
+		hlog.Verbosef("attaching supplementary group ids %s", k.user.supp)
+		// interpreted by hsu
+		ms.cmd.Env = append(ms.cmd.Env, "HAKUREI_GROUPS="+strings.Join(k.user.supp, " "))
+	}
+
+	hlog.Verbosef("setuid helper at %s", hsuPath)
+	hlog.Suspend()
+	if err := ms.cmd.Start(); err != nil {
+		ms.fatal("cannot start setuid wrapper:", err)
+	}
+	startTime := time.Now().UTC()
+	ms.cmdWait = make(chan error, 1)
+	// this ties context back to the life of the process
+	go func() { ms.cmdWait <- ms.cmd.Wait(); cancel() }()
+	ms.Time = &startTime
+
+	// unfortunately the I/O here cannot be directly canceled;
+	// the cancellation path leads to fatal in this case so that is fine
+	select {
+	case err := <-func() (setupErr chan error) {
+		setupErr = make(chan error, 1)
+		go func() {
+			setupErr <- e.Encode(&shimParams{
+				os.Getpid(),
+				k.waitDelay,
+				k.container,
+				hlog.Load(),
+			})
+		}()
+		return
+	}():
+		if err != nil {
+			hlog.Resume()
+			ms.fatal("cannot transmit shim config:", err)
+		}
+
+	case <-ctx.Done():
+		hlog.Resume()
+		ms.fatal("shim context canceled:", newWithMessageError("shim setup canceled", ctx.Err()))
+	}
+
+	// shim accepted setup payload, create process state
+	if ok, err := ms.store.Do(k.user.identity.unwrap(), func(c state.Cursor) {
+		if err := c.Save(&state.State{
+			ID:   k.id.unwrap(),
+			PID:  ms.cmd.Process.Pid,
+			Time: *ms.Time,
+		}, k.ct); err != nil {
+			ms.fatal("cannot save state entry:", err)
+		}
+	}); err != nil {
+		if ok {
+			ms.uintptr |= mainNeedsDestroy
+			ms.fatal("cannot unlock state store:", err)
+		} else {
+			ms.fatal("cannot open state store:", err)
+		}
+	}
+	// state in store at this point, destroy defunct state entry on termination
+	ms.uintptr |= mainNeedsDestroy
+
+	// beforeExit ties shim process to context
+	ms.beforeExit(false)
+	os.Exit(0)
+}
+
+// printMessageError prints the error message according to [container.GetErrorMessage],
+// or fallback prepended to err if an error message is not available.
+func printMessageError(fallback string, err error) {
+	m, ok := container.GetErrorMessage(err)
+	if !ok {
+		log.Println(fallback, err)
+		return
+	}
+
+	log.Print(m)
+}

internal/app/process_linux.go

@@ -1,201 +0,0 @@
-package app
-
-import (
-	"context"
-	"encoding/gob"
-	"errors"
-	"log"
-	"os"
-	"os/exec"
-	"strconv"
-	"strings"
-	"syscall"
-	"time"
-
-	"hakurei.app/container"
-	"hakurei.app/internal"
-	"hakurei.app/internal/app/state"
-	"hakurei.app/internal/hlog"
-	"hakurei.app/system"
-)
-
-const shimWaitTimeout = 5 * time.Second
-
-func (seal *outcome) Run(rs *RunState) error {
-	if !seal.f.CompareAndSwap(false, true) {
-		// run does much more than just starting a process; calling it twice, even if the first call fails, will result
-		// in inconsistent state that is impossible to clean up; return here to limit damage and hopefully give the
-		// other Run a chance to return
-		return errors.New("outcome: attempted to run twice")
-	}
-
-	if rs == nil {
-		panic("invalid state")
-	}
-
-	// read comp value early to allow for early failure
-	hsuPath := internal.MustHsuPath()
-
-	if err := seal.sys.Commit(seal.ctx); err != nil {
-		return err
-	}
-	store := state.NewMulti(seal.runDirPath.String())
-	deferredStoreFunc := func(c state.Cursor) error { return nil } // noop until state in store
-	defer func() {
-		var revertErr error
-		storeErr := new(StateStoreError)
-		storeErr.Inner, storeErr.DoErr = store.Do(seal.user.aid.unwrap(), func(c state.Cursor) {
-			revertErr = func() error {
-				storeErr.InnerErr = deferredStoreFunc(c)
-
-				var rt system.Enablement
-				ec := system.Process
-				if states, err := c.Load(); err != nil {
-					// revert per-process state here to limit damage
-					storeErr.OpErr = err
-					return seal.sys.Revert((*system.Criteria)(&ec))
-				} else {
-					if l := len(states); l == 0 {
-						ec |= system.User
-					} else {
-						hlog.Verbosef("found %d instances, cleaning up without user-scoped operations", l)
-					}
-
-					// accumulate enablements of remaining launchers
-					for i, s := range states {
-						if s.Config != nil {
-							rt |= s.Config.Enablements.Unwrap()
-						} else {
-							log.Printf("state entry %d does not contain config", i)
-						}
-					}
-				}
-				ec |= rt ^ (system.EWayland | system.EX11 | system.EDBus | system.EPulse)
-				if hlog.Load() {
-					if ec > 0 {
-						hlog.Verbose("reverting operations scope", system.TypeString(ec))
-					}
-				}
-
-				return seal.sys.Revert((*system.Criteria)(&ec))
-			}()
-		})
-		storeErr.save(revertErr, store.Close())
-		rs.RevertErr = storeErr.equiv("error during cleanup:")
-	}()
-
-	ctx, cancel := context.WithCancel(seal.ctx)
-	defer cancel()
-	cmd := exec.CommandContext(ctx, hsuPath)
-	cmd.Stdin, cmd.Stdout, cmd.Stderr = os.Stdin, os.Stdout, os.Stderr
-	cmd.Dir = container.FHSRoot // container init enters final working directory
-	// shim runs in the same session as monitor; see shim.go for behaviour
-	cmd.Cancel = func() error { return cmd.Process.Signal(syscall.SIGCONT) }
-
-	var e *gob.Encoder
-	if fd, encoder, err := container.Setup(&cmd.ExtraFiles); err != nil {
-		return hlog.WrapErrSuffix(err,
-			"cannot create shim setup pipe:")
-	} else {
-		e = encoder
-		cmd.Env = []string{
-			// passed through to shim by hsu
-			shimEnv + "=" + strconv.Itoa(fd),
-			// interpreted by hsu
-			"HAKUREI_APP_ID=" + seal.user.aid.String(),
-		}
-	}
-
-	if len(seal.user.supp) > 0 {
-		hlog.Verbosef("attaching supplementary group ids %s", seal.user.supp)
-		// interpreted by hsu
-		cmd.Env = append(cmd.Env, "HAKUREI_GROUPS="+strings.Join(seal.user.supp, " "))
-	}
-
-	hlog.Verbosef("setuid helper at %s", hsuPath)
-	hlog.Suspend()
-	if err := cmd.Start(); err != nil {
-		return hlog.WrapErrSuffix(err,
-			"cannot start setuid wrapper:")
-	}
-	rs.SetStart()
-
-	// this prevents blocking forever on an early failure
-	waitErr, setupErr := make(chan error, 1), make(chan error, 1)
-	go func() { waitErr <- cmd.Wait(); cancel() }()
-	go func() {
-		setupErr <- e.Encode(&shimParams{
-			os.Getpid(),
-			seal.waitDelay,
-			seal.container,
-			hlog.Load(),
-		})
-	}()
-
-	select {
-	case err := <-setupErr:
-		if err != nil {
-			hlog.Resume()
-			return hlog.WrapErrSuffix(err,
-				"cannot transmit shim config:")
-		}
-
-	case <-ctx.Done():
-		hlog.Resume()
-		return hlog.WrapErr(syscall.ECANCELED,
-			"shim setup canceled")
-	}
-
-	// returned after blocking on waitErr
-	var earlyStoreErr = new(StateStoreError)
-	{
-		// shim accepted setup payload, create process state
-		sd := state.State{
-			ID:   seal.id.unwrap(),
-			PID:  cmd.Process.Pid,
-			Time: *rs.Time,
-		}
-		earlyStoreErr.Inner, earlyStoreErr.DoErr = store.Do(seal.user.aid.unwrap(), func(c state.Cursor) {
-			earlyStoreErr.InnerErr = c.Save(&sd, seal.ct)
-		})
-	}
-
-	// state in store at this point, destroy defunct state entry on return
-	deferredStoreFunc = func(c state.Cursor) error { return c.Destroy(seal.id.unwrap()) }
-
-	waitTimeout := make(chan struct{})
-	go func() { <-seal.ctx.Done(); time.Sleep(shimWaitTimeout); close(waitTimeout) }()
-
-	select {
-	case rs.WaitErr = <-waitErr:
-		rs.WaitStatus = cmd.ProcessState.Sys().(syscall.WaitStatus)
-		if hlog.Load() {
-			switch {
-			case rs.Exited():
-				hlog.Verbosef("process %d exited with code %d", cmd.Process.Pid, rs.ExitStatus())
-			case rs.CoreDump():
-				hlog.Verbosef("process %d dumped core", cmd.Process.Pid)
-			case rs.Signaled():
-				hlog.Verbosef("process %d got %s", cmd.Process.Pid, rs.Signal())
-			default:
-				hlog.Verbosef("process %d exited with status %#x", cmd.Process.Pid, rs.WaitStatus)
-			}
-		}
-	case <-waitTimeout:
-		rs.WaitErr = syscall.ETIMEDOUT
-		hlog.Resume()
-		log.Printf("process %d did not terminate", cmd.Process.Pid)
-	}
-
-	hlog.Resume()
-	if seal.sync != nil {
-		if err := seal.sync.Close(); err != nil {
-			log.Printf("cannot close wayland security context: %v", err)
-		}
-	}
-	if seal.dbusMsg != nil {
-		seal.dbusMsg()
-	}
-
-	return earlyStoreErr.equiv("cannot save process state:")
-}

internal/app/shim.go

@@ -45,8 +45,10 @@ const (
 	// ShimExitOrphan is returned when the shim is orphaned before monitor delivers a signal.
 	ShimExitOrphan = 3
 
+	// DefaultShimWaitDelay is used when WaitDelay has its zero value.
 	DefaultShimWaitDelay = 5 * time.Second
-	MaxShimWaitDelay     = 30 * time.Second
+	// MaxShimWaitDelay is used instead if WaitDelay exceeds its value.
+	MaxShimWaitDelay = 30 * time.Second
 )
 
 // ShimMain is the main function of the shim process and runs as the unconstrained target user.
@@ -65,7 +67,7 @@ func ShimMain() {
 		if errors.Is(err, syscall.EBADF) {
 			log.Fatal("invalid config descriptor")
 		}
-		if errors.Is(err, container.ErrNotSet) {
+		if errors.Is(err, container.ErrReceiveEnv) {
 			log.Fatal("HAKUREI_SHIM not set")
 		}
 
@@ -155,11 +157,11 @@ func ShimMain() {
 	}
 
 	if err := z.Start(); err != nil {
-		hlog.PrintBaseError(err, "cannot start container:")
+		printMessageError("cannot start container:", err)
 		os.Exit(1)
 	}
 	if err := z.Serve(); err != nil {
-		hlog.PrintBaseError(err, "cannot configure container:")
+		printMessageError("cannot configure container:", err)
 	}
 
 	if err := seccomp.Load(

internal/app/state/multi.go

@@ -27,27 +27,27 @@ type multiStore struct {
 	lock sync.RWMutex
 }
 
-func (s *multiStore) Do(aid int, f func(c Cursor)) (bool, error) {
+func (s *multiStore) Do(identity int, f func(c Cursor)) (bool, error) {
 	s.lock.RLock()
 	defer s.lock.RUnlock()
 
 	// load or initialise new backend
 	b := new(multiBackend)
 	b.lock.Lock()
-	if v, ok := s.backends.LoadOrStore(aid, b); ok {
+	if v, ok := s.backends.LoadOrStore(identity, b); ok {
 		b = v.(*multiBackend)
 	} else {
-		b.path = path.Join(s.base, strconv.Itoa(aid))
+		b.path = path.Join(s.base, strconv.Itoa(identity))
 
 		// ensure directory
 		if err := os.MkdirAll(b.path, 0700); err != nil && !errors.Is(err, fs.ErrExist) {
-			s.backends.CompareAndDelete(aid, b)
+			s.backends.CompareAndDelete(identity, b)
 			return false, err
 		}
 
 		// open locker file
 		if l, err := os.OpenFile(b.path+".lock", os.O_RDWR|os.O_CREATE, 0600); err != nil {
-			s.backends.CompareAndDelete(aid, b)
+			s.backends.CompareAndDelete(identity, b)
 			return false, err
 		} else {
 			b.lockfile = l

internal/app/state/state.go

@@ -17,7 +17,7 @@ type Store interface {
 	// Do calls f exactly once and ensures store exclusivity until f returns.
 	// Returns whether f is called and any errors during the locking process.
 	// Cursor provided to f becomes invalid as soon as f returns.
-	Do(aid int, f func(c Cursor)) (ok bool, err error)
+	Do(identity int, f func(c Cursor)) (ok bool, err error)
 
 	// List queries the store and returns a list of aids known to the store.
 	// Note that some or all returned aids might not have any active apps.

internal/app/strings.go

@@ -2,12 +2,9 @@ package app
 
 import (
 	"strconv"
-
-	"hakurei.app/internal/app/state"
 )
 
-func newInt(v int) *stringPair[int]            { return &stringPair[int]{v, strconv.Itoa(v)} }
+func newInt(v int) *stringPair[int] { return &stringPair[int]{v, strconv.Itoa(v)} }
-func newID(id *state.ID) *stringPair[state.ID] { return &stringPair[state.ID]{*id, id.String()} }
 
 // stringPair stores a value and its string representation.
 type stringPair[T comparable] struct {

internal/app/sysconf.go

@@ -0,0 +1,8 @@
+package app
+
+//#include <unistd.h>
+import "C"
+
+const _SC_LOGIN_NAME_MAX = C._SC_LOGIN_NAME_MAX
+
+func sysconf(name C.int) int { return int(C.sysconf(name)) }

internal/app/username.go

@@ -0,0 +1,12 @@
+package app
+
+import "regexp"
+
+// nameRegex is the default NAME_REGEX value from adduser.
+var nameRegex = regexp.MustCompilePOSIX(`^[a-zA-Z][a-zA-Z0-9_-]*\$?$`)
+
+// isValidUsername returns whether the argument is a valid username
+func isValidUsername(username string) bool {
+	return len(username) < sysconf(_SC_LOGIN_NAME_MAX) &&
+		nameRegex.MatchString(username)
+}

internal/hlog/errors.go

@@ -1,81 +0,0 @@
-package hlog
-
-import (
-	"fmt"
-	"log"
-	"reflect"
-	"strings"
-)
-
-// baseError implements a basic error container
-type baseError struct {
-	Err error
-}
-
-func (e *baseError) Error() string { return e.Err.Error() }
-func (e *baseError) Unwrap() error { return e.Err }
-
-// BaseError implements an error container with a user-facing message
-type BaseError struct {
-	message string
-	baseError
-}
-
-// Message returns a user-facing error message
-func (e *BaseError) Message() string { return e.message }
-
-// WrapErr wraps an error with a corresponding message.
-func WrapErr(err error, a ...any) error {
-	if err == nil {
-		return nil
-	}
-	return wrapErr(err, fmt.Sprintln(a...))
-}
-
-// WrapErrSuffix wraps an error with a corresponding message with err at the end of the message.
-func WrapErrSuffix(err error, a ...any) error {
-	if err == nil {
-		return nil
-	}
-	return wrapErr(err, fmt.Sprintln(append(a, err)...))
-}
-
-// WrapErrFunc wraps an error with a corresponding message returned by f.
-func WrapErrFunc(err error, f func(err error) string) error {
-	if err == nil {
-		return nil
-	}
-	return wrapErr(err, f(err))
-}
-
-func wrapErr(err error, message string) *BaseError {
-	return &BaseError{message, baseError{err}}
-}
-
-var (
-	baseErrorType = reflect.TypeFor[*BaseError]()
-)
-
-func AsBaseError(err error, target **BaseError) bool {
-	v := reflect.ValueOf(err)
-	if !v.CanConvert(baseErrorType) {
-		return false
-	}
-
-	*target = v.Convert(baseErrorType).Interface().(*BaseError)
-	return true
-}
-
-func PrintBaseError(err error, fallback string) {
-	var e *BaseError
-
-	if AsBaseError(err, &e) {
-		if msg := e.Message(); strings.TrimSpace(msg) != "" {
-			log.Print(msg)
-			return
-		}
-		Verbose("*"+fallback, err)
-		return
-	}
-	log.Println(fallback, err)
-}

internal/hlog/hlog.go

@@ -2,69 +2,17 @@
 package hlog
 
 import (
-	"bytes"
-	"io"
 	"log"
 	"os"
-	"sync"
+
-	"sync/atomic"
+	"hakurei.app/container"
-	"syscall"
 )
 
-const (
+var o = &container.Suspendable{Downstream: os.Stderr}
-	bufSize    = 4 * 1024
-	bufSizeMax = 16 * 1024 * 1024
-)
-
-var o = &suspendable{w: os.Stderr}
 
 // Prepare configures the system logger for [Suspend] and [Resume] to take effect.
 func Prepare(prefix string) { log.SetPrefix(prefix + ": "); log.SetFlags(0); log.SetOutput(o) }
 
-type suspendable struct {
-	w io.Writer
-	s atomic.Bool
-
-	buf     bytes.Buffer
-	bufOnce sync.Once
-	bufMu   sync.Mutex
-	dropped int
-}
-
-func (s *suspendable) Write(p []byte) (n int, err error) {
-	if !s.s.Load() {
-		return s.w.Write(p)
-	}
-	s.bufOnce.Do(func() { s.prepareBuf() })
-
-	s.bufMu.Lock()
-	defer s.bufMu.Unlock()
-
-	if l := len(p); s.buf.Len()+l > bufSizeMax {
-		s.dropped += l
-		return 0, syscall.ENOMEM
-	}
-	return s.buf.Write(p)
-}
-
-func (s *suspendable) prepareBuf()   { s.buf.Grow(bufSize) }
-func (s *suspendable) Suspend() bool { return o.s.CompareAndSwap(false, true) }
-func (s *suspendable) Resume() (resumed bool, dropped uintptr, n int64, err error) {
-	if o.s.CompareAndSwap(true, false) {
-		o.bufMu.Lock()
-		defer o.bufMu.Unlock()
-
-		resumed = true
-		dropped = uintptr(o.dropped)
-
-		o.dropped = 0
-		n, err = io.Copy(s.w, &s.buf)
-		s.buf = bytes.Buffer{}
-		s.prepareBuf()
-	}
-	return
-}
-
 func Suspend() bool { return o.Suspend() }
 func Resume() bool {
 	resumed, dropped, _, err := o.Resume()

internal/hlog/msg.go

@@ -2,11 +2,9 @@ package hlog
 
 type Output struct{}
 
-func (Output) IsVerbose() bool                         { return Load() }
+func (Output) IsVerbose() bool                  { return Load() }
-func (Output) Verbose(v ...any)                        { Verbose(v...) }
+func (Output) Verbose(v ...any)                 { Verbose(v...) }
-func (Output) Verbosef(format string, v ...any)        { Verbosef(format, v...) }
+func (Output) Verbosef(format string, v ...any) { Verbosef(format, v...) }
-func (Output) WrapErr(err error, a ...any) error       { return WrapErr(err, a...) }
+func (Output) Suspend()                         { Suspend() }
-func (Output) PrintBaseErr(err error, fallback string) { PrintBaseError(err, fallback) }
+func (Output) Resume() bool                     { return Resume() }
-func (Output) Suspend()                                { Suspend() }
+func (Output) BeforeExit()                      { BeforeExit() }
-func (Output) Resume() bool                            { return Resume() }
-func (Output) BeforeExit()                             { BeforeExit() }

internal/sys/interface.go

@@ -1,82 +0,0 @@
-// Package sys wraps OS interaction library functions.
-package sys
-
-import (
-	"io/fs"
-	"log"
-	"os/user"
-	"strconv"
-
-	"hakurei.app/container"
-	"hakurei.app/hst"
-	"hakurei.app/internal/hlog"
-)
-
-// State provides safe interaction with operating system state.
-type State interface {
-	// Getuid provides [os.Getuid].
-	Getuid() int
-	// Getgid provides [os.Getgid].
-	Getgid() int
-	// LookupEnv provides [os.LookupEnv].
-	LookupEnv(key string) (string, bool)
-	// TempDir provides [os.TempDir].
-	TempDir() string
-	// LookPath provides exec.LookPath.
-	LookPath(file string) (string, error)
-	// MustExecutable provides [container.MustExecutable].
-	MustExecutable() string
-	// LookupGroup provides [user.LookupGroup].
-	LookupGroup(name string) (*user.Group, error)
-	// ReadDir provides [os.ReadDir].
-	ReadDir(name string) ([]fs.DirEntry, error)
-	// Stat provides [os.Stat].
-	Stat(name string) (fs.FileInfo, error)
-	// Open provides [os.Open].
-	Open(name string) (fs.File, error)
-	// EvalSymlinks provides filepath.EvalSymlinks.
-	EvalSymlinks(path string) (string, error)
-	// Exit provides [os.Exit].
-	Exit(code int)
-
-	Println(v ...any)
-	Printf(format string, v ...any)
-
-	// Paths returns a populated [hst.Paths] struct.
-	Paths() hst.Paths
-	// Uid invokes hsu and returns target uid.
-	// Any errors returned by Uid is already wrapped [hlog.BaseError].
-	Uid(identity int) (int, error)
-}
-
-// GetUserID obtains user id from hsu by querying uid of identity 0.
-func GetUserID(os State) (int, error) {
-	if uid, err := os.Uid(0); err != nil {
-		return -1, err
-	} else {
-		return (uid / 10000) - 100, nil
-	}
-}
-
-// CopyPaths is a generic implementation of [hst.Paths].
-func CopyPaths(os State, v *hst.Paths, userid int) {
-	if tempDir, err := container.NewAbs(os.TempDir()); err != nil {
-		log.Fatalf("invalid TMPDIR: %v", err)
-	} else {
-		v.TempDir = tempDir
-	}
-
-	v.SharePath = v.TempDir.Append("hakurei." + strconv.Itoa(userid))
-	hlog.Verbosef("process share directory at %q", v.SharePath)
-
-	r, _ := os.LookupEnv(xdgRuntimeDir)
-	if a, err := container.NewAbs(r); err != nil {
-		// fall back to path in share since hakurei has no hard XDG dependency
-		v.RunDirPath = v.SharePath.Append("run")
-		v.RuntimePath = v.RunDirPath.Append("compat")
-	} else {
-		v.RuntimePath = a
-		v.RunDirPath = v.RuntimePath.Append("hakurei")
-	}
-	hlog.Verbosef("runtime directory at %q", v.RunDirPath)
-}

internal/sys/std.go

@@ -1,114 +0,0 @@
-package sys
-
-import (
-	"errors"
-	"fmt"
-	"io/fs"
-	"os"
-	"os/exec"
-	"os/user"
-	"path/filepath"
-	"strconv"
-	"sync"
-	"syscall"
-
-	"hakurei.app/container"
-	"hakurei.app/hst"
-	"hakurei.app/internal"
-	"hakurei.app/internal/hlog"
-)
-
-// Std implements System using the standard library.
-type Std struct {
-	paths     hst.Paths
-	pathsOnce sync.Once
-
-	uidOnce sync.Once
-	uidCopy map[int]struct {
-		uid int
-		err error
-	}
-	uidMu sync.RWMutex
-}
-
-func (s *Std) Getuid() int                                  { return os.Getuid() }
-func (s *Std) Getgid() int                                  { return os.Getgid() }
-func (s *Std) LookupEnv(key string) (string, bool)          { return os.LookupEnv(key) }
-func (s *Std) TempDir() string                              { return os.TempDir() }
-func (s *Std) LookPath(file string) (string, error)         { return exec.LookPath(file) }
-func (s *Std) MustExecutable() string                       { return container.MustExecutable() }
-func (s *Std) LookupGroup(name string) (*user.Group, error) { return user.LookupGroup(name) }
-func (s *Std) ReadDir(name string) ([]os.DirEntry, error)   { return os.ReadDir(name) }
-func (s *Std) Stat(name string) (fs.FileInfo, error)        { return os.Stat(name) }
-func (s *Std) Open(name string) (fs.File, error)            { return os.Open(name) }
-func (s *Std) EvalSymlinks(path string) (string, error)     { return filepath.EvalSymlinks(path) }
-func (s *Std) Exit(code int)                                { internal.Exit(code) }
-func (s *Std) Println(v ...any)                             { hlog.Verbose(v...) }
-func (s *Std) Printf(format string, v ...any)               { hlog.Verbosef(format, v...) }
-
-const xdgRuntimeDir = "XDG_RUNTIME_DIR"
-
-func (s *Std) Paths() hst.Paths {
-	s.pathsOnce.Do(func() {
-		if userid, err := GetUserID(s); err != nil {
-			hlog.PrintBaseError(err, "cannot obtain user id from hsu:")
-			hlog.BeforeExit()
-			s.Exit(1)
-		} else {
-			CopyPaths(s, &s.paths, userid)
-		}
-	})
-	return s.paths
-}
-
-func (s *Std) Uid(identity int) (int, error) {
-	s.uidOnce.Do(func() {
-		s.uidCopy = make(map[int]struct {
-			uid int
-			err error
-		})
-	})
-
-	{
-		s.uidMu.RLock()
-		u, ok := s.uidCopy[identity]
-		s.uidMu.RUnlock()
-		if ok {
-			return u.uid, u.err
-		}
-	}
-
-	s.uidMu.Lock()
-	defer s.uidMu.Unlock()
-
-	u := struct {
-		uid int
-		err error
-	}{}
-	defer func() { s.uidCopy[identity] = u }()
-
-	u.uid = -1
-	hsuPath := internal.MustHsuPath()
-
-	cmd := exec.Command(hsuPath)
-	cmd.Path = hsuPath
-	cmd.Stderr = os.Stderr // pass through fatal messages
-	cmd.Env = []string{"HAKUREI_APP_ID=" + strconv.Itoa(identity)}
-	cmd.Dir = container.FHSRoot
-	var (
-		p         []byte
-		exitError *exec.ExitError
-	)
-
-	if p, u.err = cmd.Output(); u.err == nil {
-		u.uid, u.err = strconv.Atoi(string(p))
-		if u.err != nil {
-			u.err = hlog.WrapErr(u.err, "invalid uid string from hsu")
-		}
-	} else if errors.As(u.err, &exitError) && exitError != nil && exitError.ExitCode() == 1 {
-		u.err = hlog.WrapErr(syscall.EACCES, "") // hsu prints to stderr in this case
-	} else if os.IsNotExist(u.err) {
-		u.err = hlog.WrapErr(os.ErrNotExist, fmt.Sprintf("the setuid helper is missing: %s", hsuPath))
-	}
-	return u.uid, u.err
-}

internal/sysconf.go

@@ -1,8 +0,0 @@
-package internal
-
-//#include <unistd.h>
-import "C"
-
-const SC_LOGIN_NAME_MAX = C._SC_LOGIN_NAME_MAX
-
-func Sysconf(name C.int) int { return int(C.sysconf(name)) }

options.md

@@ -35,7 +35,7 @@ package
 
 
 *Default:*
-` <derivation hakurei-static-x86_64-unknown-linux-musl-0.2.0> `
+` <derivation hakurei-static-x86_64-unknown-linux-musl-0.2.2> `
 
 
 
@@ -313,7 +313,7 @@ Extra paths to make available to the container\.
 
 
 *Type:*
-anything
+list of attribute set of anything
 
 
 
@@ -723,7 +723,7 @@ Common extra paths to make available to the container\.
 
 
 *Type:*
-anything
+list of attribute set of anything
 
 
 
@@ -759,7 +759,7 @@ package
 
 
 *Default:*
-` <derivation hakurei-hsu-0.2.0> `
+` <derivation hakurei-hsu-0.2.2> `
 
 
 

options.nix

@@ -203,7 +203,7 @@ in
               };
 
               extraPaths = mkOption {
-                type = anything;
+                type = listOf (attrsOf anything);
                 default = [ ];
                 description = ''
                   Extra paths to make available to the container.
@@ -261,7 +261,7 @@ in
       };
 
       commonPaths = mkOption {
-        type = types.anything;
+        type = types.listOf (types.attrsOf types.anything);
         default = [ ];
         description = ''
           Common extra paths to make available to the container.

package.nix

@@ -31,7 +31,7 @@
 
 buildGoModule rec {
   pname = "hakurei";
-  version = "0.2.0";
+  version = "0.2.2";
 
   srcFiltered = builtins.path {
     name = "${pname}-src";

system/acl.go

@@ -9,65 +9,59 @@ import (
 	"hakurei.app/system/acl"
 )
 
-// UpdatePerm appends an ephemeral acl update Op.
+// UpdatePerm calls UpdatePermType with the [Process] criteria.
 func (sys *I) UpdatePerm(path string, perms ...acl.Perm) *I {
 	sys.UpdatePermType(Process, path, perms...)
-
 	return sys
 }
 
-// UpdatePermType appends an acl update Op.
+// UpdatePermType maintains [acl.Perms] on a file until its [Enablement] is no longer satisfied.
 func (sys *I) UpdatePermType(et Enablement, path string, perms ...acl.Perm) *I {
-	sys.lock.Lock()
+	sys.ops = append(sys.ops, &aclUpdateOp{et, path, perms})
-	defer sys.lock.Unlock()
-
-	sys.ops = append(sys.ops, &ACL{et, path, perms})
-
 	return sys
 }
 
-type ACL struct {
+// aclUpdateOp implements [I.UpdatePermType].
+type aclUpdateOp struct {
 	et    Enablement
 	path  string
 	perms acl.Perms
 }
 
-func (a *ACL) Type() Enablement { return a.et }
+func (a *aclUpdateOp) Type() Enablement { return a.et }
 
-func (a *ACL) apply(sys *I) error {
+func (a *aclUpdateOp) apply(sys *I) error {
-	msg.Verbose("applying ACL", a)
+	sys.verbose("applying ACL", a)
-	return wrapErrSuffix(acl.Update(a.path, sys.uid, a.perms...),
+	return newOpError("acl", sys.aclUpdate(a.path, sys.uid, a.perms...), false)
-		fmt.Sprintf("cannot apply ACL entry to %q:", a.path))
 }
 
-func (a *ACL) revert(sys *I, ec *Criteria) error {
+func (a *aclUpdateOp) revert(sys *I, ec *Criteria) error {
-	if ec.hasType(a) {
+	if ec.hasType(a.Type()) {
-		msg.Verbose("stripping ACL", a)
+		sys.verbose("stripping ACL", a)
-		err := acl.Update(a.path, sys.uid)
+		err := sys.aclUpdate(a.path, sys.uid)
 		if errors.Is(err, os.ErrNotExist) {
 			// the ACL is effectively stripped if the file no longer exists
-			msg.Verbosef("target of ACL %s no longer exists", a)
+			sys.verbosef("target of ACL %s no longer exists", a)
 			err = nil
 		}
-		return wrapErrSuffix(err,
+		return newOpError("acl", err, true)
-			fmt.Sprintf("cannot strip ACL entry from %q:", a.path))
 	} else {
-		msg.Verbose("skipping ACL", a)
+		sys.verbose("skipping ACL", a)
 		return nil
 	}
 }
 
-func (a *ACL) Is(o Op) bool {
+func (a *aclUpdateOp) Is(o Op) bool {
-	a0, ok := o.(*ACL)
+	target, ok := o.(*aclUpdateOp)
-	return ok && a0 != nil &&
+	return ok && a != nil && target != nil &&
-		a.et == a0.et &&
+		a.et == target.et &&
-		a.path == a0.path &&
+		a.path == target.path &&
-		slices.Equal(a.perms, a0.perms)
+		slices.Equal(a.perms, target.perms)
 }
 
-func (a *ACL) Path() string { return a.path }
+func (a *aclUpdateOp) Path() string { return a.path }
 
-func (a *ACL) String() string {
+func (a *aclUpdateOp) String() string {
 	return fmt.Sprintf("%s type: %s path: %q",
 		a.perms, TypeString(a.et), a.path)
 }

system/acl/acl.go

@@ -29,8 +29,5 @@ func Update(name string, uid int, perms ...Perm) error {
 		(*C.acl_perm_t)(p),
 		C.size_t(len(perms)),
 	)
-	if r == 0 {
+	return newAclPathError(name, int(r), err)
-		return nil
-	}
-	return err
 }

system/acl/acl_getfacl_test.go

@@ -1,156 +0,0 @@
-package acl_test
-
-import (
-	"bufio"
-	"bytes"
-	"errors"
-	"fmt"
-	"io"
-	"os/exec"
-	"strconv"
-)
-
-type (
-	getFAclInvocation struct {
-		cmd *exec.Cmd
-		val []*getFAclResp
-		pe  []error
-	}
-
-	getFAclResp struct {
-		typ  fAclType
-		cred int32
-		val  fAclPerm
-
-		raw []byte
-	}
-
-	fAclPerm uintptr
-	fAclType uint8
-)
-
-const fAclBufSize = 16
-
-const (
-	fAclPermRead fAclPerm = 1 << iota
-	fAclPermWrite
-	fAclPermExecute
-)
-
-const (
-	fAclTypeUser fAclType = iota
-	fAclTypeGroup
-	fAclTypeMask
-	fAclTypeOther
-)
-
-func (c *getFAclInvocation) run(name string) error {
-	if c.cmd != nil {
-		panic("attempted to run twice")
-	}
-
-	c.cmd = exec.Command("getfacl", "--omit-header", "--absolute-names", "--numeric", name)
-
-	scanErr := make(chan error, 1)
-	if p, err := c.cmd.StdoutPipe(); err != nil {
-		return err
-	} else {
-		go c.parse(p, scanErr)
-	}
-
-	if err := c.cmd.Start(); err != nil {
-		return err
-	}
-
-	return errors.Join(<-scanErr, c.cmd.Wait())
-}
-
-func (c *getFAclInvocation) parse(pipe io.Reader, scanErr chan error) {
-	c.val = make([]*getFAclResp, 0, 4+fAclBufSize)
-
-	s := bufio.NewScanner(pipe)
-	for s.Scan() {
-		fields := bytes.SplitN(s.Bytes(), []byte{':'}, 3)
-		if len(fields) != 3 {
-			continue
-		}
-
-		resp := getFAclResp{}
-
-		switch string(fields[0]) {
-		case "user":
-			resp.typ = fAclTypeUser
-		case "group":
-			resp.typ = fAclTypeGroup
-		case "mask":
-			resp.typ = fAclTypeMask
-		case "other":
-			resp.typ = fAclTypeOther
-		default:
-			c.pe = append(c.pe, fmt.Errorf("unknown type %s", string(fields[0])))
-			continue
-		}
-
-		if len(fields[1]) == 0 {
-			resp.cred = -1
-		} else {
-			if cred, err := strconv.Atoi(string(fields[1])); err != nil {
-				c.pe = append(c.pe, err)
-				continue
-			} else {
-				resp.cred = int32(cred)
-				if resp.cred < 0 {
-					c.pe = append(c.pe, fmt.Errorf("credential %d out of range", resp.cred))
-					continue
-				}
-			}
-		}
-
-		if len(fields[2]) != 3 {
-			c.pe = append(c.pe, fmt.Errorf("invalid perm length %d", len(fields[2])))
-			continue
-		} else {
-			switch fields[2][0] {
-			case 'r':
-				resp.val |= fAclPermRead
-			case '-':
-			default:
-				c.pe = append(c.pe, fmt.Errorf("invalid perm %v", fields[2][0]))
-				continue
-			}
-			switch fields[2][1] {
-			case 'w':
-				resp.val |= fAclPermWrite
-			case '-':
-			default:
-				c.pe = append(c.pe, fmt.Errorf("invalid perm %v", fields[2][1]))
-				continue
-			}
-			switch fields[2][2] {
-			case 'x':
-				resp.val |= fAclPermExecute
-			case '-':
-			default:
-				c.pe = append(c.pe, fmt.Errorf("invalid perm %v", fields[2][2]))
-				continue
-			}
-		}
-
-		resp.raw = make([]byte, len(s.Bytes()))
-		copy(resp.raw, s.Bytes())
-		c.val = append(c.val, &resp)
-	}
-	scanErr <- s.Err()
-}
-
-func (r *getFAclResp) String() string {
-	if r.raw != nil && len(r.raw) > 0 {
-		return string(r.raw)
-	}
-
-	return "(user-initialised resp value)"
-}
-
-func (r *getFAclResp) equals(typ fAclType, cred int32, val fAclPerm) bool {
-	return r.typ == typ && r.cred == cred && r.val == val
-}

system/acl/acl_test.go

@@ -1,10 +1,16 @@
 package acl_test
 
 import (
+	"bufio"
+	"bytes"
 	"errors"
+	"fmt"
+	"io"
 	"os"
+	"os/exec"
 	"path"
 	"reflect"
+	"strconv"
 	"testing"
 
 	"hakurei.app/system/acl"
@@ -17,7 +23,7 @@ var (
 	cred = int32(os.Geteuid())
 )
 
-func TestUpdatePerm(t *testing.T) {
+func TestUpdate(t *testing.T) {
 	if os.Getenv("GO_TEST_SKIP_ACL") == "1" {
 		t.Log("acl test skipped")
 		t.SkipNow()
@@ -48,19 +54,19 @@ func TestUpdatePerm(t *testing.T) {
 
 	t.Run("default clear mask", func(t *testing.T) {
 		if err := acl.Update(testFilePath, uid); err != nil {
-			t.Fatalf("UpdatePerm: error = %v", err)
+			t.Fatalf("Update: error = %v", err)
 		}
 		if cur = getfacl(t, testFilePath); len(cur) != 4 {
-			t.Fatalf("UpdatePerm: %v", cur)
+			t.Fatalf("Update: %v", cur)
 		}
 	})
 
 	t.Run("default clear consistency", func(t *testing.T) {
 		if err := acl.Update(testFilePath, uid); err != nil {
-			t.Fatalf("UpdatePerm: error = %v", err)
+			t.Fatalf("Update: error = %v", err)
 		}
 		if val := getfacl(t, testFilePath); !reflect.DeepEqual(val, cur) {
-			t.Fatalf("UpdatePerm: %v, want %v", val, cur)
+			t.Fatalf("Update: %v, want %v", val, cur)
 		}
 	})
 
@@ -77,26 +83,171 @@ func testUpdate(t *testing.T, testFilePath, name string, cur []*getFAclResp, val
 	t.Run(name, func(t *testing.T) {
 		t.Cleanup(func() {
 			if err := acl.Update(testFilePath, uid); err != nil {
-				t.Fatalf("UpdatePerm: error = %v", err)
+				t.Fatalf("Update: error = %v", err)
 			}
 			if v := getfacl(t, testFilePath); !reflect.DeepEqual(v, cur) {
-				t.Fatalf("UpdatePerm: %v, want %v", v, cur)
+				t.Fatalf("Update: %v, want %v", v, cur)
 			}
 		})
 
 		if err := acl.Update(testFilePath, uid, perms...); err != nil {
-			t.Fatalf("UpdatePerm: error = %v", err)
+			t.Fatalf("Update: error = %v", err)
 		}
 		r := respByCred(getfacl(t, testFilePath), fAclTypeUser, cred)
 		if r == nil {
-			t.Fatalf("UpdatePerm did not add an ACL entry")
+			t.Fatalf("Update did not add an ACL entry")
 		}
 		if !r.equals(fAclTypeUser, cred, val) {
-			t.Fatalf("UpdatePerm(%s) = %s", name, r)
+			t.Fatalf("Update(%s) = %s", name, r)
 		}
 	})
 }
 
+type (
+	getFAclInvocation struct {
+		cmd *exec.Cmd
+		val []*getFAclResp
+		pe  []error
+	}
+
+	getFAclResp struct {
+		typ  fAclType
+		cred int32
+		val  fAclPerm
+
+		raw []byte
+	}
+
+	fAclPerm uintptr
+	fAclType uint8
+)
+
+const fAclBufSize = 16
+
+const (
+	fAclPermRead fAclPerm = 1 << iota
+	fAclPermWrite
+	fAclPermExecute
+)
+
+const (
+	fAclTypeUser fAclType = iota
+	fAclTypeGroup
+	fAclTypeMask
+	fAclTypeOther
+)
+
+func (c *getFAclInvocation) run(name string) error {
+	if c.cmd != nil {
+		panic("attempted to run twice")
+	}
+
+	c.cmd = exec.Command("getfacl", "--omit-header", "--absolute-names", "--numeric", name)
+
+	scanErr := make(chan error, 1)
+	if p, err := c.cmd.StdoutPipe(); err != nil {
+		return err
+	} else {
+		go c.parse(p, scanErr)
+	}
+
+	if err := c.cmd.Start(); err != nil {
+		return err
+	}
+
+	return errors.Join(<-scanErr, c.cmd.Wait())
+}
+
+func (c *getFAclInvocation) parse(pipe io.Reader, scanErr chan error) {
+	c.val = make([]*getFAclResp, 0, 4+fAclBufSize)
+
+	s := bufio.NewScanner(pipe)
+	for s.Scan() {
+		fields := bytes.SplitN(s.Bytes(), []byte{':'}, 3)
+		if len(fields) != 3 {
+			continue
+		}
+
+		resp := getFAclResp{}
+
+		switch string(fields[0]) {
+		case "user":
+			resp.typ = fAclTypeUser
+		case "group":
+			resp.typ = fAclTypeGroup
+		case "mask":
+			resp.typ = fAclTypeMask
+		case "other":
+			resp.typ = fAclTypeOther
+		default:
+			c.pe = append(c.pe, fmt.Errorf("unknown type %s", string(fields[0])))
+			continue
+		}
+
+		if len(fields[1]) == 0 {
+			resp.cred = -1
+		} else {
+			if cred, err := strconv.Atoi(string(fields[1])); err != nil {
+				c.pe = append(c.pe, err)
+				continue
+			} else {
+				resp.cred = int32(cred)
+				if resp.cred < 0 {
+					c.pe = append(c.pe, fmt.Errorf("credential %d out of range", resp.cred))
+					continue
+				}
+			}
+		}
+
+		if len(fields[2]) != 3 {
+			c.pe = append(c.pe, fmt.Errorf("invalid perm length %d", len(fields[2])))
+			continue
+		} else {
+			switch fields[2][0] {
+			case 'r':
+				resp.val |= fAclPermRead
+			case '-':
+			default:
+				c.pe = append(c.pe, fmt.Errorf("invalid perm %v", fields[2][0]))
+				continue
+			}
+			switch fields[2][1] {
+			case 'w':
+				resp.val |= fAclPermWrite
+			case '-':
+			default:
+				c.pe = append(c.pe, fmt.Errorf("invalid perm %v", fields[2][1]))
+				continue
+			}
+			switch fields[2][2] {
+			case 'x':
+				resp.val |= fAclPermExecute
+			case '-':
+			default:
+				c.pe = append(c.pe, fmt.Errorf("invalid perm %v", fields[2][2]))
+				continue
+			}
+		}
+
+		resp.raw = make([]byte, len(s.Bytes()))
+		copy(resp.raw, s.Bytes())
+		c.val = append(c.val, &resp)
+	}
+	scanErr <- s.Err()
+}
+
+func (r *getFAclResp) String() string {
+	if r.raw != nil && len(r.raw) > 0 {
+		return string(r.raw)
+	}
+
+	return "(user-initialised resp value)"
+}
+
+func (r *getFAclResp) equals(typ fAclType, cred int32, val fAclPerm) bool {
+	return r.typ == typ && r.cred == cred && r.val == val
+}
+
 func getfacl(t *testing.T, name string) []*getFAclResp {
 	c := new(getFAclInvocation)
 	if err := c.run(name); err != nil {

system/acl/libacl-helper.c

@@ -6,7 +6,7 @@
 
 int hakurei_acl_update_file_by_uid(const char *path_p, uid_t uid,
                                    acl_perm_t *perms, size_t plen) {
-  int ret = -1;
+  int ret;
   bool v;
   int i;
   acl_t acl;
@@ -15,51 +15,70 @@ int hakurei_acl_update_file_by_uid(const char *path_p, uid_t uid,
   void *qualifier_p;
   acl_permset_t permset;
 
+  ret = -1; /* acl_get_file */
   acl = acl_get_file(path_p, ACL_TYPE_ACCESS);
   if (acl == NULL)
     goto out;
 
-  // prune entries by uid
+  /* prune entries by uid */
   for (i = acl_get_entry(acl, ACL_FIRST_ENTRY, &entry); i == 1;
        i = acl_get_entry(acl, ACL_NEXT_ENTRY, &entry)) {
+    ret = -2; /* acl_get_tag_type */
     if (acl_get_tag_type(entry, &tag_type) != 0)
-      return -1;
+      goto out;
     if (tag_type != ACL_USER)
       continue;
 
+    ret = -3; /* acl_get_qualifier */
     qualifier_p = acl_get_qualifier(entry);
     if (qualifier_p == NULL)
-      return -1;
+      goto out;
     v = *(uid_t *)qualifier_p == uid;
     acl_free(qualifier_p);
 
     if (!v)
       continue;
 
-    acl_delete_entry(acl, entry);
+    ret = -4; /* acl_delete_entry */
+    if (acl_delete_entry(acl, entry) != 0)
+      goto out;
   }
 
   if (plen == 0)
     goto set;
 
+  ret = -5; /* acl_create_entry */
   if (acl_create_entry(&acl, &entry) != 0)
     goto out;
+
+  ret = -6; /* acl_get_permset */
   if (acl_get_permset(entry, &permset) != 0)
     goto out;
+
+  ret = -7; /* acl_add_perm */
   for (i = 0; i < plen; i++) {
     if (acl_add_perm(permset, perms[i]) != 0)
       goto out;
   }
+
+  ret = -8; /* acl_set_tag_type */
   if (acl_set_tag_type(entry, ACL_USER) != 0)
     goto out;
+
+  ret = -9; /* acl_set_qualifier */
   if (acl_set_qualifier(entry, (void *)&uid) != 0)
     goto out;
 
 set:
+  ret = -10; /* acl_calc_mask */
   if (acl_calc_mask(&acl) != 0)
     goto out;
+
+  ret = -11; /* acl_valid */
   if (acl_valid(acl) != 0)
     goto out;
+
+  ret = -12; /* acl_set_file */
   if (acl_set_file(path_p, ACL_TYPE_ACCESS, acl) == 0)
     ret = 0;