release: 0.4.7

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

.gitattributes

@@ -0,0 +1 @@
+*.az linguist-language=Azalea

.gitea/workflows/release.yml

@@ -14,7 +14,7 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Build for release
-        run: nix build --print-out-paths --print-build-logs .#dist
+        run: nix build --print-out-paths --print-build-logs ./test#dist
 
       - name: Release
         uses: https://gitea.com/actions/release-action@main

.gitea/workflows/test.yml

@@ -12,7 +12,7 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Run NixOS test
-        run: nix build --out-link "result" --print-out-paths --print-build-logs .#checks.x86_64-linux.hakurei
+        run: nix build --out-link "result" --print-out-paths --print-build-logs ./test#checks.x86_64-linux.hakurei
 
       - name: Upload test output
         uses: actions/upload-artifact@v3
@@ -29,7 +29,7 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Run NixOS test
-        run: nix build --out-link "result" --print-out-paths --print-build-logs .#checks.x86_64-linux.race
+        run: nix build --out-link "result" --print-out-paths --print-build-logs ./test#checks.x86_64-linux.race
 
       - name: Upload test output
         uses: actions/upload-artifact@v3
@@ -46,7 +46,7 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Run NixOS test
-        run: nix build --out-link "result" --print-out-paths --print-build-logs .#checks.x86_64-linux.sandbox
+        run: nix build --out-link "result" --print-out-paths --print-build-logs ./test#checks.x86_64-linux.sandbox
 
       - name: Upload test output
         uses: actions/upload-artifact@v3
@@ -63,7 +63,7 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Run NixOS test
-        run: nix build --out-link "result" --print-out-paths --print-build-logs .#checks.x86_64-linux.sandbox-race
+        run: nix build --out-link "result" --print-out-paths --print-build-logs ./test#checks.x86_64-linux.sandbox-race
 
       - name: Upload test output
         uses: actions/upload-artifact@v3
@@ -80,7 +80,7 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Run NixOS test
-        run: nix build --out-link "result" --print-out-paths --print-build-logs .#checks.x86_64-linux.sharefs
+        run: nix build --out-link "result" --print-out-paths --print-build-logs ./test#checks.x86_64-linux.sharefs
 
       - name: Upload test output
         uses: actions/upload-artifact@v3
@@ -103,7 +103,7 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Run checks
-        run: nix --print-build-logs --experimental-features 'nix-command flakes' flake check
+        run: nix --print-build-logs --experimental-features 'nix-command flakes' flake check ./test
 
   dist:
     name: Create distribution
@@ -116,9 +116,9 @@ jobs:
         id: build-test
         run: >-
           export HAKUREI_REV="$(git rev-parse --short HEAD)" &&
-          sed -i.old 's/version = /version = "0.0.0-'$HAKUREI_REV'"; # version = /' package.nix &&
-          nix build --print-out-paths --print-build-logs .#dist &&
-          mv package.nix.old package.nix &&
+          sed -i.old 's/version = /version = "0.0.0-'$HAKUREI_REV'"; # version = /' test/package.nix &&
+          nix build --print-out-paths --print-build-logs ./test#dist &&
+          mv test/{package.nix.old,package.nix} &&
           echo "rev=$HAKUREI_REV" >> $GITHUB_OUTPUT
 
       - name: Upload test build

.gitignore

@@ -1,4 +1,5 @@
 # produced by tools and text editors
+*.swp
 *.qcow2
 *.test
 *.out

README.md

@@ -11,7 +11,7 @@
   <a href="https://git.gensokyo.uk/rosa/hakurei/actions"><img src="https://git.gensokyo.uk/rosa/hakurei/actions/workflows/test.yml/badge.svg?branch=staging&style=flat-square" alt="Gitea Workflow Status" /></a>
   <br/>
   <a href="https://git.gensokyo.uk/rosa/hakurei/releases"><img src="https://img.shields.io/gitea/v/release/rosa/hakurei?gitea_url=https%3A%2F%2Fgit.gensokyo.uk&color=purple" alt="Release" /></a>
-  <a href="https://goreportcard.com/report/hakurei.app"><img src="https://goreportcard.com/badge/hakurei.app" alt="Go Report Card" /></a>
+  <a href="https://git.gensokyo.uk/rosa/hakurei/src/branch/master/LICENSE"><img src="https://img.shields.io/badge/license-MIT-pink" alt="MIT License" /></a>
   <a href="https://hakurei.app"><img src="https://img.shields.io/website?url=https%3A%2F%2Fhakurei.app" alt="Website" /></a>
 </p>
 
@@ -57,9 +57,4 @@ package [internal/rosa](https://pkg.go.dev/hakurei.app/internal/rosa).
 - [fuse](https://github.com/libfuse/libfuse) to implement the filesystem.
 
 New dependencies will generally not be added. Patches adding new dependencies
-are very likely to be rejected.
-
-## NixOS Module (deprecated)
-
-The NixOS module is in maintenance mode and will be removed once planterette is
-feature-complete. Full module documentation can be found [here](options.md).
+are very likely to be rejected.

check/absolute.go

@@ -20,8 +20,8 @@ func (e AbsoluteError) Error() string {
 }
 
 func (e AbsoluteError) Is(target error) bool {
-	var ce AbsoluteError
-	if !errors.As(target, &ce) {
+	ce, ok := errors.AsType[AbsoluteError](target)
+	if !ok {
 		return errors.Is(target, syscall.EINVAL)
 	}
 	return e == ce
@@ -31,6 +31,8 @@ func (e AbsoluteError) Is(target error) bool {
 type Absolute struct{ pathname unique.Handle[string] }
 
 var (
+	_ fmt.GoStringer = new(Absolute)
+
 	_ encoding.TextAppender    = new(Absolute)
 	_ encoding.TextMarshaler   = new(Absolute)
 	_ encoding.TextUnmarshaler = new(Absolute)
@@ -40,6 +42,10 @@ var (
 	_ encoding.BinaryUnmarshaler = new(Absolute)
 )
 
+func (a *Absolute) GoString() string {
+	return fmt.Sprintf("check.MustAbs(%q)", a.String())
+}
+
 // ok returns whether [Absolute] is not the zero value.
 func (a *Absolute) ok() bool { return a != nil && *a != (Absolute{}) }
 

cmd/app/app.go

@@ -0,0 +1,354 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"strconv"
+	"strings"
+
+	"hakurei.app/check"
+	"hakurei.app/ext"
+	"hakurei.app/fhs"
+	"hakurei.app/hst"
+)
+
+// parsePair parses a NUL-delimited quoted paths pair.
+func parsePair(s string) (source, target *check.Absolute, err error) {
+	var p string
+	if p, err = strconv.Unquote(s); err != nil {
+		return
+	}
+	_source, _target, ok := strings.Cut(p, "\x00")
+	if source, err = check.NewAbs(_source); err != nil {
+		return
+	}
+	if !ok {
+		return
+	}
+	target, err = check.NewAbs(_target)
+	return
+}
+
+// parse decodes a high-level configuration stream and returns its
+// corresponding [hst.Config].
+func parse(
+	id string,
+	base *check.Absolute,
+	r io.Reader,
+	templateP *string,
+) (*hst.Config, error) {
+	shell := fhs.AbsRoot.Append("bin", "zsh")
+	home := hst.AbsPrivateTmp.Append("home")
+
+	root := hst.FSOverlay{
+		Target: fhs.AbsRoot,
+		Lower:  []*check.Absolute{base.Append("initial")},
+	}
+	c := hst.Config{
+		ID:          id,
+		Enablements: new(hst.Enablements),
+
+		SessionBus: &hst.BusConfig{
+			Own: []string{
+				id + ".*",
+				"org.mpris.MediaPlayer2." + id + ".*",
+			},
+			Filter: true,
+		},
+		SystemBus: &hst.BusConfig{Filter: true},
+
+		Container: &hst.ContainerConfig{
+			Env: make(map[string]string),
+			Filesystem: []hst.FilesystemConfigJSON{
+				{FilesystemConfig: &root},
+				{FilesystemConfig: &hst.FSBind{
+					Target: home,
+					Source: base.Append("state", id),
+					Write:  true,
+					Ensure: true,
+				}},
+
+				{FilesystemConfig: &hst.FSEphemeral{
+					Target: fhs.AbsVar.Append("tmp"),
+					Write:  true,
+					Perm:   01777,
+				}},
+			},
+
+			Username: "chronos",
+			Shell:    shell,
+			Home:     home,
+			Path:     shell,
+			Args:     []string{"zsh", "-c"},
+
+			Flags: hst.FCoverRun,
+		},
+	}
+
+	s := bufio.NewScanner(r)
+	scanOnce := func() error {
+		if s.Scan() {
+			return nil
+		}
+		if err := s.Err(); err != nil {
+			return err
+		}
+		return io.ErrUnexpectedEOF
+	}
+
+	if err := scanOnce(); err != nil {
+		return nil, err
+	}
+	if template, identity, ok := strings.Cut(s.Text(), ":"); !ok {
+		return nil, io.ErrUnexpectedEOF
+	} else if v, err := strconv.Atoi(identity); err != nil {
+		return nil, err
+	} else {
+		if templateP != nil {
+			*templateP = template
+		}
+		c.Identity = v
+		root.Upper = base.Append("template", template)
+	}
+
+	if err := scanOnce(); err != nil {
+		return nil, err
+	}
+	c.Container.Args = append(c.Container.Args, s.Text(), "")
+
+	var flagInteractive, flagGPU, flagSystemBus bool
+	flags := map[string]*bool{
+		"interactive": &flagInteractive,
+		"gpu":         &flagGPU,
+		"system_bus":  &flagSystemBus,
+	}
+
+	for s.Scan() {
+		key, value, ok := strings.Cut(s.Text(), " ")
+		if key != "" && key[0] == ';' {
+			continue
+		}
+
+		if !ok {
+			if key == "" {
+				continue
+			}
+
+			var p *bool
+			if p, ok = flags[key]; ok {
+				*p = true
+				continue
+			}
+
+			switch key {
+			case "wayland":
+				*c.Enablements |= hst.EWayland
+			case "x11":
+				*c.Enablements |= hst.EX11
+			case "dbus":
+				*c.Enablements |= hst.EDBus
+			case "pipewire":
+				*c.Enablements |= hst.EPipeWire
+
+			case "multiarch":
+				c.Container.Flags |= hst.FMultiarch
+			case "devel":
+				c.Container.Flags |= hst.FDevel
+			case "userns":
+				c.Container.Flags |= hst.FUserns
+			case "net":
+				c.Container.Flags |= hst.FHostNet
+			case "abstract":
+				c.Container.Flags |= hst.FHostAbstract
+			case "tty":
+				c.Container.Flags |= hst.FTty
+			case "mapuid":
+				c.Container.Flags |= hst.FMapRealUID
+			case "device":
+				c.Container.Flags |= hst.FDevice
+
+			case "share_runtime":
+				c.Container.Flags |= hst.FShareRuntime
+			case "share_tmpdir":
+				c.Container.Flags |= hst.FShareTmpdir
+
+			default:
+				return nil, fmt.Errorf("invalid flag %q", key)
+			}
+
+			continue
+		}
+
+		switch key {
+		case "username":
+			c.Container.Username = value
+			continue
+
+		case "hostname":
+			c.Container.Hostname = value
+			continue
+
+		case "group":
+			c.Groups = append(c.Groups, value)
+			continue
+
+		case "sched_policy":
+			if err := c.SchedPolicy.UnmarshalText([]byte(value)); err != nil {
+				return nil, err
+			}
+			continue
+
+		case "sched_priority":
+			v, err := strconv.Atoi(value)
+			if err != nil {
+				return nil, err
+			}
+			c.SchedPriority = ext.Int(v)
+			continue
+
+		case "insecure":
+			switch value {
+			case "pipewire":
+				*c.Enablements |= hst.EPipeWire
+				c.DirectPipeWire = true
+				continue
+
+			default:
+				return nil, fmt.Errorf("invalid insecure flag %q", value)
+			}
+
+		case "env":
+			if key, value, ok = strings.Cut(value, "="); !ok {
+				return nil, fmt.Errorf("invalid environment %q", key)
+			}
+			c.Container.Env[key] = value
+			continue
+
+		case "ro":
+			source, target, err := parsePair(value)
+			if err != nil {
+				return nil, err
+			}
+			c.Container.Filesystem = append(c.Container.Filesystem,
+				hst.FilesystemConfigJSON{FilesystemConfig: &hst.FSBind{
+					Target: target,
+					Source: source,
+				}},
+			)
+			continue
+
+		case "ro+":
+			source, target, err := parsePair(value)
+			if err != nil {
+				return nil, err
+			}
+			c.Container.Filesystem = append(c.Container.Filesystem,
+				hst.FilesystemConfigJSON{FilesystemConfig: &hst.FSBind{
+					Target:   target,
+					Source:   source,
+					Optional: true,
+				}},
+			)
+			continue
+
+		case "rw":
+			source, target, err := parsePair(value)
+			if err != nil {
+				return nil, err
+			}
+			c.Container.Filesystem = append(c.Container.Filesystem,
+				hst.FilesystemConfigJSON{FilesystemConfig: &hst.FSBind{
+					Target: target,
+					Source: source,
+					Write:  true,
+				}},
+			)
+			continue
+
+		case "dev":
+			source, target, err := parsePair(value)
+			if err != nil {
+				return nil, err
+			}
+			c.Container.Filesystem = append(c.Container.Filesystem,
+				hst.FilesystemConfigJSON{FilesystemConfig: &hst.FSBind{
+					Target: target,
+					Source: source,
+					Device: true,
+				}},
+			)
+			continue
+
+		case "own":
+			c.SessionBus.Own = append(c.SessionBus.Own, value)
+			continue
+		case "own_system":
+			c.SystemBus.Own = append(c.SystemBus.Own, value)
+			continue
+
+		case "talk":
+			c.SessionBus.Talk = append(c.SessionBus.Talk, value)
+			continue
+		case "talk_system":
+			c.SystemBus.Talk = append(c.SystemBus.Talk, value)
+			continue
+
+		default:
+			return nil, fmt.Errorf("invalid key %q", key)
+		}
+	}
+	if err := s.Err(); err != nil {
+		return nil, err
+	}
+
+	if flagInteractive {
+		c.Container.Args[1] += "i"
+	}
+
+	if flagGPU {
+		c.Container.Filesystem = append(c.Container.Filesystem, []hst.FilesystemConfigJSON{
+			{FilesystemConfig: &hst.FSBind{
+				Source:   fhs.AbsDev.Append("dri"),
+				Device:   true,
+				Optional: true,
+			}},
+		}...)
+	}
+
+	if !flagSystemBus {
+		c.SystemBus = nil
+	}
+
+	if c.Container.Flags&hst.FShareTmpdir == 0 &&
+		(c.Enablements.Unwrap()&hst.EX11 == 0 ||
+			c.Container.Flags&(hst.FHostNet|hst.FHostAbstract) ==
+				hst.FHostNet|hst.FHostAbstract) {
+		c.Container.Filesystem = append(c.Container.Filesystem,
+			hst.FilesystemConfigJSON{FilesystemConfig: &hst.FSEphemeral{
+				Target: fhs.AbsTmp,
+				Write:  true,
+				Perm:   01777,
+			}},
+		)
+	}
+
+	return &c, nil
+}
+
+// list prints names of non-hidden entries in pathname.
+func list(pathname *check.Absolute, dir bool) error {
+	dents, err := os.ReadDir(pathname.String())
+	if err != nil {
+		return err
+	}
+	for _, dent := range dents {
+		name := dent.Name()
+		if (dent.IsDir() != dir) || (len(name) > 0 && name[0] == '.') {
+			continue
+		}
+		fmt.Println(dent.Name())
+	}
+	return nil
+}

cmd/app/app_test.go

@@ -0,0 +1,148 @@
+package main
+
+import (
+	"reflect"
+	"strings"
+	"testing"
+
+	"hakurei.app/check"
+	"hakurei.app/fhs"
+	"hakurei.app/hst"
+)
+
+func TestParse(t *testing.T) {
+	t.Parallel()
+
+	base := fhs.AbsProc.Append("nonexistent")
+	testCases := []struct {
+		name string
+		data string
+		want *hst.Config
+		err  error
+	}{
+		{"com.discordapp.Discord", `nonfree:8
+exec Discord --ozone-platform-hint=wayland
+
+gpu
+wayland
+dbus
+system_bus
+pipewire
+userns
+net
+mapuid
+
+share_runtime
+share_tmpdir
+
+group media_rw
+env ELECTRON_TRASH=gio
+rw "/sdcard"
+; remove before reusing
+ro "/bin\x00/.hakurei/bin"
+
+talk org.kde.StatusNotifierWatcher
+talk com.canonical.AppMenu.Registrar
+talk com.canonical.indicator.application
+talk com.canonical.Unity
+`, &hst.Config{
+			Identity:    8,
+			ID:          "com.discordapp.Discord",
+			Enablements: new(hst.EWayland | hst.EDBus | hst.EPipeWire),
+			Groups:      []string{"media_rw"},
+
+			SessionBus: &hst.BusConfig{
+				Talk: []string{
+					"org.kde.StatusNotifierWatcher",
+					"com.canonical.AppMenu.Registrar",
+					"com.canonical.indicator.application",
+					"com.canonical.Unity",
+				},
+				Own: []string{
+					"com.discordapp.Discord.*",
+					"org.mpris.MediaPlayer2.com.discordapp.Discord.*",
+				},
+				Filter: true,
+			},
+			SystemBus: &hst.BusConfig{Filter: true},
+
+			Container: &hst.ContainerConfig{
+				Env: map[string]string{
+					"ELECTRON_TRASH": "gio",
+				},
+				Filesystem: []hst.FilesystemConfigJSON{
+					{FilesystemConfig: &hst.FSOverlay{
+						Target: fhs.AbsRoot,
+						Lower: []*check.Absolute{
+							base.Append("initial"),
+						},
+						Upper: base.Append("template", "nonfree"),
+					}},
+					{FilesystemConfig: &hst.FSBind{
+						Target: hst.AbsPrivateTmp.Append("home"),
+						Source: base.Append("state", "com.discordapp.Discord"),
+						Write:  true,
+						Ensure: true,
+					}},
+
+					{FilesystemConfig: &hst.FSEphemeral{
+						Target: fhs.AbsVar.Append("tmp"),
+						Write:  true,
+						Perm:   01777,
+					}},
+
+					{FilesystemConfig: &hst.FSBind{
+						Source: check.MustAbs("/sdcard"),
+						Write:  true,
+					}},
+					{FilesystemConfig: &hst.FSBind{
+						Target: check.MustAbs("/.hakurei/bin"),
+						Source: check.MustAbs("/bin"),
+					}},
+
+					{FilesystemConfig: &hst.FSBind{
+						Source:   fhs.AbsDev.Append("dri"),
+						Device:   true,
+						Optional: true,
+					}},
+				},
+
+				Username: "chronos",
+				Shell:    fhs.AbsRoot.Append("bin", "zsh"),
+				Home:     hst.AbsPrivateTmp.Append("home"),
+				Path:     fhs.AbsRoot.Append("bin", "zsh"),
+				Args: []string{
+					"zsh", "-c",
+					"exec Discord --ozone-platform-hint=wayland",
+					"",
+				},
+
+				Flags: hst.FCoverRun | hst.FUserns | hst.FHostNet | hst.FMapRealUID |
+					hst.FShareRuntime | hst.FShareTmpdir,
+			},
+		}, nil},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			got, err := parse(
+				tc.name,
+				base,
+				strings.NewReader(tc.data),
+				nil,
+			)
+
+			if !reflect.DeepEqual(err, tc.err) {
+				t.Errorf("parse: error = %v, want %v", err, tc.err)
+			}
+			if err != nil {
+				return
+			}
+
+			if !reflect.DeepEqual(got, tc.want) {
+				t.Errorf("parse: %#v, want %#v", got, tc.want)
+			}
+		})
+	}
+}

cmd/app/lock.go

@@ -0,0 +1,112 @@
+package main
+
+import (
+	"errors"
+	"log"
+	"os"
+	"strconv"
+	"strings"
+
+	"hakurei.app/check"
+	"hakurei.app/fhs"
+	"hakurei.app/hst"
+	"hakurei.app/internal/env"
+	"hakurei.app/internal/lockedfile"
+	"hakurei.app/internal/outcome"
+)
+
+// MutationConflictError describes an active mutable instance.
+type MutationConflictError string
+
+func (e MutationConflictError) Error() string {
+	return "mutable instance active at " + string(e)
+}
+
+// informTemplate guards intention of a template or its derivatives.
+func informTemplate(base *check.Absolute, name string, mutable bool) (func() error, error) {
+	mu := lockedfile.MutexAt(base.Append("lock", name).String())
+	if unlock, err := mu.Lock(); err != nil {
+		return nil, err
+	} else {
+		defer unlock()
+	}
+
+	marker := base.Append("lock", "."+name)
+	if p, err := os.ReadFile(marker.String()); err == nil {
+		if _, err = os.Stat(fhs.AbsProc.Append(string(p)).String()); err == nil {
+			return nil, MutationConflictError(p)
+		} else if !errors.Is(err, os.ErrNotExist) {
+			return nil, err
+		}
+		log.Printf("removing stale marker by %s", string(p))
+		if err = os.Remove(marker.String()); err != nil {
+			return nil, err
+		}
+	} else if !errors.Is(err, os.ErrNotExist) {
+		return nil, err
+	}
+
+	if !mutable {
+		return nil, nil
+	}
+
+	var active []hst.ID
+	var sc hst.Paths
+	env.CopyPaths().Copy(&sc, new(outcome.Hsu).MustID(nil))
+	entries, copyError := outcome.NewStore(&sc).All()
+	var s hst.State
+	for eh := range entries {
+		s = hst.State{}
+		if _, err := eh.Load(&s); err != nil {
+			return nil, err
+		}
+
+		if s.Validate(0) != nil || len(s.Container.Filesystem) < 1 {
+			continue
+		}
+		root, ok := s.Container.Filesystem[0].FilesystemConfig.(*hst.FSOverlay)
+		if !ok || root == nil {
+			continue
+		}
+
+		if !root.Target.Is(fhs.AbsRoot) ||
+			len(root.Lower) != 1 ||
+			!root.Lower[0].Is(base.Append("initial")) ||
+			!root.Upper.Is(base.Append("template", name)) ||
+			root.Work != nil {
+			continue
+		}
+
+		active = append(active, s.ID)
+	}
+	if err := copyError(); err != nil {
+		return nil, err
+	}
+
+	if len(active) != 0 {
+		var buf strings.Builder
+		buf.WriteString("derivative instances still active:")
+		for _, id := range active {
+			buf.WriteString("\n\t")
+			buf.WriteString(id.String())
+		}
+		return nil, errors.New(buf.String())
+	}
+
+	return func() error { return os.RemoveAll(marker.String()) }, os.WriteFile(
+		marker.String(),
+		[]byte(strconv.Itoa(os.Getpid())),
+		0400,
+	)
+}
+
+// acquireTemplate obtains exclusivity of a template.
+func acquireTemplate(base *check.Absolute, name string) (remove func() error, err error) {
+	return informTemplate(base, name, true)
+}
+
+// enterTemplate checks against exclusivity of a template.
+func enterTemplate(base *check.Absolute, name string) error {
+	_, err := informTemplate(base, name, false)
+	return err
+}

cmd/app/main.go

@@ -0,0 +1,226 @@
+// The app program is a proof-of-concept frontend for cmd/hakurei.
+//
+// This program is not covered by the compatibility promise. The command line
+// interface and configuration syntax may change at any time.
+package main
+
+import (
+	"context"
+	"errors"
+	"io"
+	"log"
+	"os"
+	"os/exec"
+	"os/signal"
+	"path/filepath"
+	"syscall"
+
+	"hakurei.app/check"
+	"hakurei.app/command"
+	"hakurei.app/fhs"
+	"hakurei.app/hst"
+	"hakurei.app/message"
+)
+
+func main() {
+	log.SetFlags(0)
+	log.SetPrefix("app: ")
+	msg := message.New(log.Default())
+
+	ctx, stop := signal.NotifyContext(context.Background(),
+		syscall.SIGINT, syscall.SIGTERM, syscall.SIGHUP)
+	defer stop()
+
+	var (
+		flagVerbose  bool
+		flagBase     string
+		flagInsecure bool
+
+		base, template, initial *check.Absolute
+	)
+	c := command.New(os.Stderr, log.Printf, "app", func([]string) (err error) {
+		msg.SwapVerbose(flagVerbose)
+		flagBase = os.ExpandEnv(flagBase)
+		if flagBase == "" {
+			flagBase = "state"
+		}
+		if flagBase, err = filepath.Abs(flagBase); err != nil {
+			return
+		} else if base, err = check.NewAbs(flagBase); err != nil {
+			return
+		}
+
+		template = base.Append("template")
+		initial = base.Append("initial")
+		return
+	}).Flag(
+		&flagVerbose,
+		"v", command.BoolFlag(false),
+		"Increase log verbosity",
+	).Flag(
+		&flagBase,
+		"d", command.StringFlag("$ROSA_APP_PATH"),
+		"Configuration and state directory",
+	).Flag(
+		&flagInsecure,
+		"insecure", command.BoolFlag(false),
+		"Allow use of insecure compatibility options",
+	)
+
+	{
+		var (
+			flagShell string
+			flagHome  string
+		)
+		c.NewCommand(
+			"enter", "Enter mutable state template",
+			func(args []string) error {
+				if len(args) != 1 {
+					return list(template, true)
+				}
+
+				config := hst.Config{
+					ID: "app.hakurei.mutable." + args[0],
+					Container: &hst.ContainerConfig{
+						Hostname: args[0] + "-mutable",
+						Filesystem: []hst.FilesystemConfigJSON{
+							{FilesystemConfig: &hst.FSOverlay{
+								Target: fhs.AbsRoot,
+								Lower:  []*check.Absolute{initial},
+								Upper:  template.Append(args[0]),
+								Work:   base.Append("work", args[0]),
+							}},
+							{FilesystemConfig: &hst.FSEphemeral{
+								Target: fhs.AbsTmp,
+								Write:  true,
+								Perm:   0755,
+							}},
+						},
+						Username: "chronos",
+						Flags: hst.FNoPlace |
+							hst.FMultiarch |
+							hst.FDevel |
+							hst.FUserns |
+							hst.FHostNet |
+							hst.FTty,
+					},
+				}
+
+				if a, err := check.NewAbs(flagShell); err != nil {
+					return err
+				} else {
+					config.Container.Shell = a
+					config.Container.Path = a
+					config.Container.Args = []string{
+						"-" + filepath.Base(flagShell),
+					}
+				}
+
+				if a, err := check.NewAbs(flagHome); err != nil {
+					return err
+				} else {
+					config.Container.Home = a
+				}
+
+				remove, err := acquireTemplate(base, args[0])
+				if err != nil {
+					return err
+				}
+				err = run(ctx, msg, false, &config)
+				return errors.Join(err, remove())
+			},
+		).Flag(
+			&flagShell,
+			"shell", command.StringFlag("/bin/zsh"),
+			"Shell program within container",
+		).Flag(
+			&flagHome,
+			"home", command.StringFlag("/home/chronos"),
+			"Home directory within container",
+		)
+	}
+
+	{
+		var (
+			flagCommand string
+		)
+		c.NewCommand(
+			"run", "Start the named application",
+			func(args []string) error {
+				if len(args) < 1 {
+					return list(base.Append("app"), false)
+				}
+
+				var config *hst.Config
+				var r io.Reader
+				f, err := os.Open(base.Append("app", args[0]).String())
+				if err != nil {
+					return err
+				}
+				r = f
+
+				var common *os.File
+				if common, err = os.Open(base.Append("common").String()); err != nil {
+					if !errors.Is(err, os.ErrNotExist) {
+						_ = f.Close()
+						return err
+					}
+				} else {
+					r = io.MultiReader(f, common)
+				}
+
+				var name string
+				config, err = parse(args[0], base, r, &name)
+				if closeErr := f.Close(); err == nil {
+					err = closeErr
+				}
+				if common != nil {
+					if closeErr := common.Close(); err == nil {
+						err = closeErr
+					}
+				}
+				if err != nil {
+					return err
+				}
+
+				if flagCommand != "" {
+					config.Container.Args[2] = flagCommand
+				}
+
+				if err = enterTemplate(base, name); err != nil {
+					return err
+				}
+				return run(ctx, msg, flagInsecure, config, args[1:]...)
+			},
+		).
+			Flag(
+				&flagCommand,
+				"command", command.StringFlag(""),
+				"Override configured command",
+			)
+	}
+
+	c.MustParse(os.Args[1:], func(err error) {
+		if e, ok := errors.AsType[*exec.ExitError](err); ok && e != nil {
+			os.Exit(e.ExitCode())
+		}
+
+		if w, ok := err.(interface{ Unwrap() []error }); !ok {
+			var m string
+			m, ok = message.GetMessage(err)
+			if !ok {
+				log.Fatal(err)
+				return
+			}
+			log.Fatal(m)
+		} else {
+			errs := w.Unwrap()
+			for i, e := range errs {
+				if i == len(errs)-1 {
+					log.Fatal(e)
+				}
+				log.Println(e)
+			}
+		}
+	})
+}

cmd/app/run.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"os"
+	"os/exec"
+	"syscall"
+
+	"hakurei.app/hst"
+	"hakurei.app/message"
+)
+
+// run starts a container via cmd/hakurei and returns after it terminates.
+func run(
+	ctx context.Context,
+	msg message.Msg,
+	insecure bool,
+	config *hst.Config,
+	args ...string,
+) error {
+	c, cancel := context.WithCancel(ctx)
+	defer cancel()
+
+	cmd := exec.CommandContext(c, "hakurei")
+	cmd.Stdin, cmd.Stdout, cmd.Stderr = os.Stdin, os.Stdout, os.Stderr
+	cmd.Cancel = func() error {
+		return cmd.Process.Signal(syscall.SIGINT)
+	}
+	if msg.IsVerbose() {
+		cmd.Args = append(cmd.Args, "-v")
+	}
+	if insecure {
+		cmd.Args = append(cmd.Args, "--insecure")
+	}
+	cmd.Args = append(cmd.Args, "run", "3")
+	cmd.Args = append(cmd.Args, args...)
+
+	r, w, err := os.Pipe()
+	if err != nil {
+		return err
+	}
+	cmd.ExtraFiles = append(cmd.ExtraFiles, r)
+
+	if err = cmd.Start(); err != nil {
+		_, _ = r.Close(), w.Close()
+		return err
+	}
+
+	if err = r.Close(); err != nil {
+		_ = w.Close()
+		return err
+	} else if err = json.NewEncoder(w).Encode(&config); err != nil {
+		_ = w.Close()
+		return err
+	} else if err = w.Close(); err != nil {
+		return err
+	}
+
+	return cmd.Wait()
+}

cmd/dist/VERSION

@@ -1 +1 @@
-v0.4.3
+v0.4.7

cmd/dist/comp/_hakurei

@@ -36,6 +36,11 @@ _hakurei_show() {
     'files:files:__hakurei_files'
 }
 
+_hakurei_kill() {
+  _alternative \
+    'instances:domains:__hakurei_instances'
+}
+
 __hakurei_files() {
   _files -g "*.(json|hakurei)"
   return $?
@@ -60,6 +65,7 @@ __hakurei_instances() {
     "run:Load and start container from configuration file"
     "exec:Configure and start a permissive container"
     "show:Show live or local instance configuration"
+    "kill:Terminate an active instance"
     "ps:List active instances"
     "version:Display version information"
     "license:Show full license text"

cmd/dist/main.go

@@ -35,8 +35,11 @@ func getenv(key, fallback string) string {
 
 // mustRun runs a command with the current process's environment and panics
 // on error or non-zero exit code.
-func mustRun(ctx context.Context, name string, arg ...string) {
+func mustRun(ctx context.Context, env []string, name string, arg ...string) {
 	cmd := exec.CommandContext(ctx, name, arg...)
+	if env != nil {
+		cmd.Env = append(cmd.Environ(), env...)
+	}
 	cmd.Stdin, cmd.Stdout, cmd.Stderr = os.Stdin, os.Stdout, os.Stderr
 	if err := cmd.Run(); err != nil {
 		panic(err)
@@ -49,11 +52,12 @@ var comp []byte
 func main() {
 	log.SetFlags(0)
 	log.SetPrefix("")
+	log.SetOutput(os.Stdout)
 
 	verbose := os.Getenv("VERBOSE") != ""
 	runTests := os.Getenv("HAKUREI_DIST_MAKE") == ""
 	version = getenv("HAKUREI_VERSION", strings.TrimSpace(version))
-	prefix := getenv("PREFIX", "/usr")
+	prefix := getenv("PREFIX", "/usr/local")
 	destdir := getenv("DESTDIR", "dist")
 
 	if verbose {
@@ -91,26 +95,37 @@ func main() {
 		verboseFlag = "-buildvcs=false"
 	}
 
-	log.Printf("Building hakurei for %s/%s.", runtime.GOOS, runtime.GOARCH)
-	mustRun(ctx, "go", "generate", "./...")
+	log.Printf("Building hakurei %s for %s/%s.", version, runtime.GOOS, runtime.GOARCH)
+	mustRun(ctx, nil, "go", "generate", "./...")
 	mustRun(
-		ctx, "go", "build",
+		ctx, nil, "go", "build",
 		"-trimpath",
 		verboseFlag, "-o", s,
 		"-ldflags=-s -w "+
 			"-buildid= -linkmode external -extldflags=-static "+
 			"-X hakurei.app/internal/info.buildVersion="+version+" "+
 			"-X hakurei.app/internal/info.hakureiPath="+prefix+"/bin/hakurei "+
-			"-X hakurei.app/internal/info.hsuPath="+prefix+"/bin/hsu "+
-			"-X main.hakureiPath="+prefix+"/bin/hakurei",
-		"./...",
+			"-X hakurei.app/internal/info.hsuPath="+prefix+"/bin/hsu",
+		"./cmd/hakurei",
+		"./cmd/sharefs",
 	)
-	log.Println()
 
+	log.Printf("Building cmd/hsu for %s/%s.", runtime.GOOS, runtime.GOARCH)
+	mustRun(
+		ctx, []string{"CGO_ENABLED=0"}, "go", "build",
+		"-trimpath",
+		verboseFlag, "-o", s,
+		"-ldflags=-s -w "+
+			"-buildid= "+
+			"-X main.hakureiPath="+prefix+"/bin/hakurei",
+		"./cmd/hsu",
+	)
+
+	log.Println()
 	if runTests {
 		log.Println("##### Testing Hakurei.")
 		mustRun(
-			ctx, "go", "test",
+			ctx, nil, "go", "test",
 			"-ldflags=-buildid= -linkmode external -extldflags=-static",
 			"./...",
 		)
@@ -202,7 +217,7 @@ func main() {
 	mustWriteFile("comp/", nil, os.ModeDir|0755)
 	mustWriteFile("comp/_hakurei", comp, 0644)
 	mustWriteFile("install.sh", []byte(`#!/bin/sh -e
-cd "$(dirname -- "$0")" || exit 1
+cd "$(dirname -- "$0")"
 
 install -vDm0755 "bin/hakurei" "${DESTDIR}`+prefix+`/bin/hakurei"
 install -vDm0755 "bin/sharefs" "${DESTDIR}`+prefix+`/bin/sharefs"
@@ -215,7 +230,7 @@ fi
 install -vDm0644 "comp/_hakurei" "${DESTDIR}`+prefix+`/share/zsh/site-functions/_hakurei"
 `), 0755)
 
-	mustWriteFromPath("README.md", "README.md", 0)
+	mustWriteFromPath("LICENSE", "LICENSE", 0)
 	mustWriteFile("hsurc.default", []byte("1000 0"), 0400)
 	mustWriteFromPath("bin/hsu", filepath.Join(s, "hsu"), 04511)
 	for _, name := range []string{

cmd/earlyinit/main.go

@@ -7,6 +7,7 @@ package main
 import (
 	"context"
 	"crypto/rand"
+	"io"
 	"log"
 	"os"
 	"os/signal"
@@ -19,6 +20,7 @@ import (
 	"hakurei.app/internal/kobject"
 	"hakurei.app/internal/report"
 	"hakurei.app/internal/uevent"
+	"hakurei.app/message"
 )
 
 var r report.Reporter
@@ -50,13 +52,14 @@ func init() {
 func fatal(v ...any) {
 	log.Println(v...)
 	log.Println("unable to continue, please reboot and resolve the problem manually")
+	log.SetOutput(io.Discard)
 	select {}
 }
 
 // must calls fatal with err if it is non-nil.
 func must(err error) {
 	if err != nil {
-		log.Println(err)
+		fatal(err)
 		select {}
 	}
 }
@@ -79,6 +82,8 @@ const (
 	// optionSystem specifies devpath of the system device.
 	optionSystem = "system"
 
+	// flagVerbose increases output verbosity.
+	flagVerbose = "verbose"
 	// flagStrict sets [report.DStrict] on r.
 	flagStrict = "strict"
 	// flagNoRecover sets [report.DNoRecover] on r.
@@ -116,6 +121,9 @@ func main() {
 		r.SetFlags(flag)
 	}
 
+	msg := message.New(log.Default())
+	msg.SwapVerbose(slices.Contains(flags, flagVerbose))
+
 	mustSyscall("mount devtmpfs", Mount(
 		"devtmpfs",
 		"/dev/",
@@ -131,6 +139,14 @@ func main() {
 		MS_NOSUID|MS_NOEXEC,
 		"mode=620,ptmxmode=666",
 	))
+	must(os.Mkdir("/dev/shm/", 0))
+	mustSyscall("mount shm", Mount(
+		"shm",
+		"/dev/shm/",
+		"tmpfs",
+		MS_NOSUID|MS_NODEV,
+		"",
+	))
 
 	// The kernel might be unable to set up the console. When that happens,
 	// printk is called with "Warning: unable to open an initial console."
@@ -193,12 +209,21 @@ func main() {
 	must1(rand.Read(uuid[:]))
 	ctx, cancel := context.WithCancel(context.Background())
 
-	go consume(ctx, &r, conn, uuid, events)
+	go consume(ctx, msg, &r, conn, uuid, events)
 	s := kobject.New(uuid, func(o *kobject.Object, env map[string]string) {
-		log.Printf("change %s: %q", o.DevPath, env)
+		p := make([]string, 0, len(env))
+		for k, v := range env {
+			p = append(p, k+"="+v)
+		}
+		slices.Sort(p)
+		log.Printf("change %s: %s", o.DevPath, strings.Join(p, ", "))
 	}, func(err error) {
+		severity := report.Inconsistent
+		if e, ok := err.(kobject.EventError); ok && e.Kind == kobject.EBadTarget {
+			severity = report.Trivial
+		}
 		r.Dispatch(
-			report.Inconsistent,
+			severity,
 			"processed inconsistent uevent",
 			err,
 		)
@@ -236,5 +261,6 @@ func main() {
 		[]byte("/system/lib/firmware"),
 		0,
 	))
+	go dispatchModprobe(ctx, s)
 
 }

cmd/earlyinit/modprobe.go

@@ -0,0 +1,74 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"log"
+	"os/exec"
+	"strings"
+
+	"hakurei.app/internal/kobject"
+	"hakurei.app/internal/report"
+	"hakurei.app/internal/uevent"
+)
+
+// ModprobeError describes an unsuccessful modprobe invocation.
+type ModprobeError struct {
+	ModAlias string `json:"modalias"`
+	Stdout   string `json:"stdout"`
+	Stderr   string `json:"stderr"`
+	ExitCode int    `json:"exit_code"`
+}
+
+var _ report.RepresentableError = ModprobeError{}
+
+func (ModprobeError) Representable() {}
+func (e ModprobeError) Error() string {
+	return fmt.Sprintf(
+		"%s (exit status %d)",
+		strings.TrimPrefix(strings.TrimSpace(e.Stderr), "modprobe: "),
+		e.ExitCode,
+	)
+}
+
+// dispatchModprobe invokes modprobe for [uevent.KOBJ_ADD] events raising new
+// MODALIAS strings.
+func dispatchModprobe(
+	ctx context.Context,
+	s *kobject.State,
+) {
+	aliases := make(chan string, 1<<8)
+	go func() {
+		defer close(aliases)
+		s.Range(ctx, func(o *kobject.Object, act uevent.KobjectAction) bool {
+			if act == uevent.KOBJ_ADD && o.Driver == "" && o.ModAlias != "" {
+				aliases <- o.ModAlias
+			}
+			return true
+		})
+	}()
+
+	for alias := range aliases {
+		stdout, err := exec.Command("/system/sbin/modprobe", alias).Output()
+		if err == nil {
+			if len(stdout) > 0 {
+				log.Println(string(stdout))
+			}
+			continue
+		}
+
+		exitError, ok := errors.AsType[*exec.ExitError](err)
+		if !ok || exitError == nil {
+			r.Dispatch(report.Degraded, "invoke modprobe", err)
+			continue
+		}
+
+		r.Dispatch(report.Trivial, "load device driver", ModprobeError{
+			ModAlias: alias,
+			Stdout:   string(stdout),
+			Stderr:   string(exitError.Stderr),
+			ExitCode: exitError.ExitCode(),
+		})
+	}
+}

cmd/earlyinit/mount.go

@@ -12,6 +12,7 @@ import (
 	"hakurei.app/check"
 	"hakurei.app/fhs"
 	"hakurei.app/internal/kobject"
+	"hakurei.app/internal/uevent"
 )
 
 // mustMountSystem waits for and mounts a system device matching pattern.
@@ -26,8 +27,9 @@ func mustMountSystem(
 	for {
 		var matchErr error
 		var systemPath *check.Absolute
-		s.Range(c, func(o *kobject.Object) bool {
-			if o.Subsystem != "block" ||
+		s.Range(c, func(o *kobject.Object, act uevent.KobjectAction) bool {
+			if (act != uevent.KOBJ_ADD && act != uevent.KOBJ_CHANGE) ||
+				o.Subsystem != "block" ||
 				o.Env["DEVTYPE"] != "disk" {
 				return true
 			}

cmd/earlyinit/uevent.go

@@ -2,12 +2,12 @@ package main
 
 import (
 	"context"
-	"log"
 	"time"
 
 	"hakurei.app/fhs"
 	"hakurei.app/internal/report"
 	"hakurei.app/internal/uevent"
+	"hakurei.app/message"
 )
 
 // newRejectColdboot returns a function to be called on every subsequent pending
@@ -56,6 +56,7 @@ func newRejectColdboot() func() bool {
 // consume continuously consumes events from conn with retries.
 func consume(
 	ctx context.Context,
+	msg message.Msg,
 	r *report.Reporter,
 	conn *uevent.Conn,
 	uuid uevent.UUID,
@@ -67,7 +68,7 @@ func consume(
 	coldboot := true
 retry:
 	if dispatchErr := conn.Consume(ctx, fhs.Sys, &uuid, events, coldboot, func(path string) {
-		log.Println("coldboot visited", path)
+		msg.Verbose("coldboot visited", path)
 	}, func(err error) bool {
 		if _, ok := err.(uevent.NeedsColdboot); ok && !nextColdboot() {
 			r.Dispatch(

cmd/hakurei/command.go

@@ -11,6 +11,7 @@ import (
 	"os/user"
 	"strconv"
 	"sync"
+	"syscall"
 	"time"
 
 	"hakurei.app/check"
@@ -372,6 +373,23 @@ func buildCommand(ctx context.Context, msg message.Msg, early *earlyHardeningErr
 			Flag(&flagNoStore, "no-store", command.BoolFlag(false), "Do not attempt to match from active instances")
 	}
 
+	c.NewCommand("kill", "Terminate an active instance", func(args []string) error {
+		if len(args) != 1 {
+			log.Fatal("kill requires 1 argument")
+		}
+
+		var sc hst.Paths
+		env.CopyPaths().Copy(&sc, new(outcome.Hsu).MustID(nil))
+		entry := tryIdentifier(msg, args[0], outcome.NewStore(&sc))
+		if entry == nil {
+			log.Fatalf("%q does not match any active instance", args[0])
+		}
+		if err := syscall.Kill(entry.PID, syscall.SIGTERM); err != nil {
+			log.Fatalf("cannot terminate %s: %v", entry.ID.String(), err)
+		}
+		return errSuccess
+	})
+
 	{
 		var flagShort bool
 		c.NewCommand("ps", "List active instances", func(args []string) error {

cmd/hakurei/command_test.go

@@ -19,13 +19,13 @@ func TestHelp(t *testing.T) {
 		want string
 	}{
 		{
-			"main", []string{}, `
-Usage:	hakurei [-h | --help] [-v] [--insecure] [--json] COMMAND [OPTIONS]
+			"main", []string{}, `usage: hakurei [-h | --help] [-v] [--insecure] [--json] <command> [<args>]
 
-Commands:
+commands:
     run         Load and start container from configuration file
     exec        Configure and start a permissive container
     show        Show live or local instance configuration
+    kill        Terminate an active instance
     ps          List active instances
     version     Display version information
     license     Show full license text
@@ -35,10 +35,14 @@ Commands:
 `,
 		},
 		{
-			"exec", []string{"exec", "-h"}, `
-Usage:	hakurei exec [-h | --help] [--dbus-config <value>] [--dbus-system <value>] [--mpris] [--dbus-log] [--id <value>] [-a <int>] [-g <value>] [-d <value>] [-u <value>] [--policy <value>] [--priority <int>] [--private-runtime] [--private-tmpdir] [--wayland] [-X] [--dbus] [--pipewire] [--pulse] COMMAND [OPTIONS]
+			"exec", []string{"exec", "-h"}, `usage: hakurei exec [-h | --help] [--dbus-config <value>]
+                    [--dbus-system <value>] [--mpris] [--dbus-log]
+                    [--id <value>] [-a <int>] [-g <value>] [-d <value>]
+                    [-u <value>] [--policy <value>] [--priority <int>]
+                    [--private-runtime] [--private-tmpdir] [--wayland] [-X]
+                    [--dbus] [--pipewire] [--pulse] <command> [<args>]
 
-Flags:
+flags:
   -X	Enable direct connection to X11
   -a int
     	Application identity

cmd/hakurei/json.go

@@ -7,7 +7,8 @@ import (
 	"strconv"
 )
 
-// decodeJSON decodes json from r and stores it in v. A non-nil error results in a call to fatal.
+// decodeJSON decodes json from r and stores it in v. A non-nil error results in
+// a call to fatal.
 func decodeJSON(fatal func(v ...any), op string, r io.Reader, v any) {
 	err := json.NewDecoder(r).Decode(v)
 	if err == nil {
@@ -47,14 +48,14 @@ func encodeJSON(fatal func(v ...any), output io.Writer, short bool, v any) {
 	}
 
 	if err := encoder.Encode(v); err != nil {
-		var marshalerError *json.MarshalerError
-		if errors.As(err, &marshalerError) && marshalerError != nil {
+		if e, ok := errors.AsType[*json.MarshalerError](err); ok && e != nil {
 			// this likely indicates an implementation error in hst
-			fatal("cannot encode json for " + marshalerError.Type.String() + ": " + marshalerError.Err.Error())
+			fatal("cannot encode json for " + e.Type.String() + ": " + e.Err.Error())
 			return
 		}
 
-		// UnsupportedTypeError, UnsupportedValueError: incorrect usage, does not need to be handled
+		// UnsupportedTypeError, UnsupportedValueError: incorrect usage, does
+		// not need to be handled
 		fatal("cannot write json: " + err.Error())
 	}
 }

cmd/hakurei/json_test.go

@@ -66,7 +66,7 @@ func TestEncodeJSON(t *testing.T) {
 		want string
 	}{
 		{"marshaler", errorJSONMarshaler{},
-			`cannot encode json for main.errorJSONMarshaler: unique error 3735928559 injected by the test suite`},
+			`cannot encode json for *main.errorJSONMarshaler: unique error 3735928559 injected by the test suite`},
 		{"default", func() {},
 			`cannot write json: json: unsupported type: func()`},
 	}

cmd/hakurei/print_test.go

@@ -64,7 +64,7 @@ func TestPrintShowInstance(t *testing.T) {
  Identity:       9 (org.chromium.Chromium)
  Enablements:    wayland, dbus, pipewire
  Groups:         video, dialout, plugdev
- Flags:          multiarch, compat, devel, userns, net, abstract, tty, mapuid, device, runtime, tmpdir
+ Flags:          multiarch, compat, devel, userns, net, abstract, tty, mapuid, noplace, device, cover_run, runtime, tmpdir
  Home:           /data/data/org.chromium.Chromium
  Hostname:       localhost
  Path:           /run/current-system/sw/bin/chromium
@@ -161,7 +161,7 @@ App
  Identity:       9 (org.chromium.Chromium)
  Enablements:    wayland, dbus, pipewire
  Groups:         video, dialout, plugdev
- Flags:          multiarch, compat, devel, userns, net, abstract, tty, mapuid, device, runtime, tmpdir
+ Flags:          multiarch, compat, devel, userns, net, abstract, tty, mapuid, noplace, device, cover_run, runtime, tmpdir
  Home:           /data/data/org.chromium.Chromium
  Hostname:       localhost
  Path:           /run/current-system/sw/bin/chromium
@@ -354,7 +354,9 @@ App
     "tty": true,
     "multiarch": true,
     "map_real_uid": true,
+    "noplace": true,
     "device": true,
+    "cover_run": true,
     "share_runtime": true,
     "share_tmpdir": true
   },
@@ -505,7 +507,9 @@ App
     "tty": true,
     "multiarch": true,
     "map_real_uid": true,
+    "noplace": true,
     "device": true,
+    "cover_run": true,
     "share_runtime": true,
     "share_tmpdir": true
   }
@@ -703,7 +707,9 @@ func TestPrintPs(t *testing.T) {
       "tty": true,
       "multiarch": true,
       "map_real_uid": true,
+      "noplace": true,
       "device": true,
+      "cover_run": true,
       "share_runtime": true,
       "share_tmpdir": true
     },

cmd/hsu/main.go

@@ -21,15 +21,6 @@
 // following paragraphs are considered an internal detail and not covered by the
 // compatibility promise.
 //
-// After checking credentials, hsu checks via /proc/ the absolute pathname of
-// its parent process, and fails if it does not match the hakurei pathname set
-// at link time. This is not a security feature: the priv-side is considered
-// trusted, and this feature makes no attempt to address the racy nature of
-// querying /proc/, or debuggers attached to the parent process. Instead, this
-// aims to discourage misuse and reduce confusion if the user accidentally
-// stumbles upon this program. It also prevents accidental use of the incorrect
-// installation of hsu in some environments.
-//
 // Since target container environment variables are set up in shim via the
 // [container] infrastructure, the environment is used for parameters from the
 // parent process.
@@ -62,7 +53,6 @@ import (
 	"runtime"
 	"slices"
 	"strconv"
-	"strings"
 	"syscall"
 )
 
@@ -107,18 +97,6 @@ func main() {
 		return
 	}
 
-	var toolPath string
-	pexe := filepath.Join("/proc", strconv.Itoa(os.Getppid()), "exe")
-	if p, err := os.Readlink(pexe); err != nil {
-		log.Fatalf("cannot read parent executable path: %v", err)
-	} else if strings.HasSuffix(p, " (deleted)") {
-		log.Fatal("hakurei executable has been deleted")
-	} else if p != hakureiPath {
-		log.Fatal("this program must be started by hakurei")
-	} else {
-		toolPath = p
-	}
-
 	// refuse to run if hsurc is not protected correctly
 	if s, err := os.Stat(hsuConfPath); err != nil {
 		log.Fatal(err)
@@ -205,7 +183,7 @@ func main() {
 		log.Fatalf("cannot set no_new_privs flag: %s", errno.Error())
 	}
 
-	if err := syscall.Exec(toolPath, []string{
+	if err := syscall.Exec(hakureiPath, []string{
 		"hakurei",
 		"shim",
 	}, []string{

cmd/mbf/cache.go

@@ -2,13 +2,15 @@ package main
 
 import (
 	"context"
+	"net/http"
 	"os"
 	"path/filepath"
+	"strconv"
 	"testing"
 
 	"hakurei.app/check"
-	"hakurei.app/container"
 	"hakurei.app/internal/pkg"
+	"hakurei.app/internal/rosa"
 	"hakurei.app/message"
 )
 
@@ -20,17 +22,29 @@ type cache struct {
 	// Should generally not be used directly.
 	c *pkg.Cache
 
-	cures, jobs int
+	attr pkg.CacheAttr
 	// Primarily to work around missing landlock LSM.
 	hostAbstract bool
 	// Set SCHED_IDLE.
 	idle bool
 	// Unset [pkg.CSuppressInit].
 	verboseInit bool
+	// Whether to enable output colours.
+	color bool
+	// Unset [pkg.CExternShallow].
+	deep bool
 	// Loaded artifact of [rosa.QEMU].
 	qemu pkg.Artifact
 
-	base string
+	base, mirror string
+}
+
+// writeTitle sets title of the terminal connected to [message.Msg].
+func writeTitle(msg message.Msg, s string) {
+	msg.Suspend()
+	w := msg.GetLogger().Writer()
+	_, _ = w.Write([]byte("\x1b]0;" + s + "\a"))
+	msg.Resume()
 }
 
 // open opens the underlying [pkg.Cache].
@@ -39,22 +53,35 @@ func (cache *cache) open() (err error) {
 		return os.ErrInvalid
 	}
 
+	var hostname string
+	if hostname, err = os.Hostname(); err != nil {
+		return
+	}
+
 	var base *check.Absolute
 	if cache.base, err = filepath.Abs(cache.base); err != nil {
 		return
 	} else if base, err = check.NewAbs(cache.base); err != nil {
 		return
 	}
+	var notify chan bool
 
-	var flags int
 	if cache.idle {
-		flags |= pkg.CSchedIdle
+		cache.attr.Flags |= pkg.CSchedIdle
 	}
 	if cache.hostAbstract {
-		flags |= pkg.CHostAbstract
+		cache.attr.Flags |= pkg.CHostAbstract
 	}
 	if !cache.verboseInit {
-		flags |= pkg.CSuppressInit
+		cache.attr.Flags |= pkg.CSuppressInit
+	}
+	if !cache.deep {
+		cache.attr.Flags |= pkg.CExternShallow
+	}
+	if cache.color {
+		cache.attr.Flags |= pkg.CColourOutput
+		notify = make(chan bool, 1<<12)
+		cache.attr.Notify = notify
 	}
 
 	done := make(chan struct{})
@@ -76,16 +103,56 @@ func (cache *cache) open() (err error) {
 	cache.c, err = pkg.Open(
 		cache.ctx,
 		cache.msg,
-		flags,
-		cache.cures,
-		cache.jobs,
 		base,
+		&cache.attr,
 	)
 	if err != nil {
 		return
 	}
 	done <- struct{}{}
 
+	if cache.mirror != "" {
+		var pub []byte
+		pub, err = os.ReadFile(base.Append("ed25519.pub").String())
+		if err != nil {
+			cache.c.Close()
+			return
+		}
+		var r rosa.Remote
+		if r, err = rosa.NewRemote(http.DefaultClient, cache.mirror, pub); err != nil {
+			cache.c.Close()
+			return err
+		}
+		cache.c.SetExternal(r)
+	}
+
+	if cache.attr.Notify != nil {
+		cache.msg.Suspend()
+		_, _ = cache.msg.GetLogger().Writer().Write([]byte("\x1b[22;0t"))
+		cache.msg.Resume()
+
+		prefix := hostname + ": mbf "
+		go func() {
+			var n, nc uint64
+			for enter := range notify {
+				if enter {
+					nc++
+				} else {
+					nc--
+					n++
+				}
+
+				if nc == 0 {
+					writeTitle(cache.msg, prefix[:len(prefix)-1])
+					continue
+				}
+				writeTitle(cache.msg, prefix+
+					"("+strconv.FormatUint(nc, 10)+
+					" running, "+strconv.FormatUint(n, 10)+" complete)")
+			}
+		}()
+	}
+
 	if cache.qemu != nil {
 		var pathname *check.Absolute
 		pathname, _, err = cache.c.Cure(cache.qemu)
@@ -94,24 +161,9 @@ func (cache *cache) open() (err error) {
 			return
 		}
 
-		pkg.RegisterArch("riscv64", container.BinfmtEntry{
-			Offset: 0,
-			Magic:  "\x7fELF\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\xf3\x00",
-			Mask:   "\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff",
-			Interpreter: pathname.Append(
-				"system/bin",
-				"qemu-riscv64",
-			),
-		})
-		pkg.RegisterArch("arm64", container.BinfmtEntry{
-			Offset: 0,
-			Magic:  "\x7fELF\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\xb7\x00",
-			Mask:   "\xff\xff\xff\xff\xff\xff\xff\xfc\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff",
-			Interpreter: pathname.Append(
-				"system/bin",
-				"qemu-aarch64",
-			),
-		})
+		for arch, entry := range rosa.Arches(pathname) {
+			pkg.RegisterArch(arch, entry)
+		}
 	}
 
 	return
@@ -121,6 +173,11 @@ func (cache *cache) open() (err error) {
 func (cache *cache) Close() {
 	if cache.c != nil {
 		cache.c.Close()
+		if cache.attr.Notify != nil {
+			cache.msg.Suspend()
+			_, _ = cache.msg.GetLogger().Writer().Write([]byte("\x1b[23;0t"))
+			cache.msg.Resume()
+		}
 	}
 }
 

cmd/mbf/daemon_test.go

@@ -28,8 +28,8 @@ func TestNoReply(t *testing.T) {
 	c, err := pkg.Open(
 		t.Context(),
 		message.New(log.New(os.Stderr, "cir: ", 0)),
-		0, 0, 0,
 		check.MustAbs(t.TempDir()),
+		nil,
 	)
 	if err != nil {
 		t.Fatalf("Open: error = %v", err)
@@ -63,7 +63,7 @@ func TestNoReply(t *testing.T) {
 	}
 
 	<-done
-	wantIdent := pkg.MustDecode("fiZf-ZY_Yq6qxJNrHbMiIPYCsGkUiKCRsZrcSELXTqZWtCnESlHmzV5ThhWWGGYG")
+	wantIdent := pkg.MustDecode("bpVsJ69hdKPBntMh_u777g7-quFNVmMlBJQOlM_thiQa9JnOFLAbe5OlR4zNjZ32")
 	if gotIdent := c.Ident(a).Value(); gotIdent != wantIdent {
 		t.Errorf(
 			"cureFromIR: %s, want %s",
@@ -124,7 +124,7 @@ func TestDaemon(t *testing.T) {
 	cancel()
 	<-done
 
-	const want = "fiZf-ZY_Yq6qxJNrHbMiIPYCsGkUiKCRsZrcSELXTqZWtCnESlHmzV5ThhWWGGYG"
+	const want = "bpVsJ69hdKPBntMh_u777g7-quFNVmMlBJQOlM_thiQa9JnOFLAbe5OlR4zNjZ32"
 	if got := filepath.Base(p.String()); got != want {
 		t.Errorf("cureRemote: %s, want %s", got, want)
 	}
@@ -132,8 +132,8 @@ func TestDaemon(t *testing.T) {
 	wantLog := []string{
 		"",
 		"daemon: aborting all pending cures",
-		"daemon: attempting to cancel invalid artifact kQm9fmnCmXST1-MMmxzcau2oKZCXXrlZydo4PkeV5hO_2PKfeC8t98hrbV_ZZx_j",
-		"daemon: fulfilled artifact fiZf-ZY_Yq6qxJNrHbMiIPYCsGkUiKCRsZrcSELXTqZWtCnESlHmzV5ThhWWGGYG",
+		"daemon: attempting to cancel invalid artifact 58Vy_5beLZCvZX__KzRKyIE6vATleaZP1ZBxbqoWnekz9aZ1zkxNgcIUFI5V1_Jf",
+		"daemon: fulfilled artifact " + want,
 	}
 	gotLog := strings.Split(buf.String(), "\n")
 	slices.Sort(gotLog)

cmd/mbf/info.go

@@ -21,7 +21,10 @@ func commandInfo(
 	r *rosa.Report,
 ) (err error) {
 	if len(args) == 0 {
-		return errors.New("info requires at least 1 argument")
+		for _, h := range rosa.Native().CollectAll() {
+			fmt.Println(h)
+		}
+		return nil
 	}
 
 	// recovered by HandleAccess

cmd/mbf/internal/pkgserver/search.go

@@ -74,7 +74,7 @@ func (s *searchCache) clean() {
 }
 func indexsum(in [][]int) int {
 	sum := 0
-	for i := 0; i < len(in); i++ {
+	for i := range in {
 		sum += in[i][1] - in[i][0]
 	}
 	return sum

cmd/mbf/main.go

@@ -14,6 +14,7 @@ package main
 
 import (
 	"context"
+	"crypto/ed25519"
 	"crypto/sha512"
 	"errors"
 	"fmt"
@@ -26,17 +27,17 @@ import (
 	"path/filepath"
 	"runtime"
 	"strconv"
+	"strings"
 	"sync"
 	"sync/atomic"
 	"syscall"
 	"time"
 	"unique"
+	"unsafe"
 
 	"hakurei.app/check"
 	"hakurei.app/command"
 	"hakurei.app/container"
-	"hakurei.app/container/seccomp"
-	"hakurei.app/container/std"
 	"hakurei.app/ext"
 	"hakurei.app/fhs"
 	"hakurei.app/internal/pkg"
@@ -47,6 +48,19 @@ import (
 	"hakurei.app/cmd/mbf/internal/pkgserver/ui"
 )
 
+// writeFileExcl is like [os.WriteFile], but sets [os.O_EXCL] instead.
+func writeFileExcl(name string, data []byte, perm os.FileMode) error {
+	f, err := os.OpenFile(name, os.O_WRONLY|os.O_CREATE|os.O_EXCL, perm)
+	if err != nil {
+		return err
+	}
+	_, err = f.Write(data)
+	if err1 := f.Close(); err1 != nil && err == nil {
+		err = err1
+	}
+	return err
+}
+
 func main() {
 	container.TryArgv0(nil)
 
@@ -78,6 +92,11 @@ func main() {
 
 	var cm cache
 	defer func() { cm.Close() }()
+	if cm.color = ext.Isatty(syscall.Stderr) &&
+		os.Getenv("NO_COLOR") == "" &&
+		os.Getenv("TERM") != "dumb"; cm.color {
+		log.SetPrefix("\x1b[2mmbf: \x1b[0m")
+	}
 
 	var (
 		flagQuiet bool
@@ -86,6 +105,8 @@ func main() {
 		flagCheck bool
 		flagLTO   bool
 		flagPT    bool
+		flagDry   bool
+		flagPath  string
 
 		flagSourcePath    string
 		flagCrossOverride int
@@ -107,6 +128,8 @@ func main() {
 		if cm.base == "" {
 			cm.base = "cache"
 		}
+		cm.mirror = os.ExpandEnv(cm.mirror)
+		azaleaPath := os.ExpandEnv(flagPath)
 
 		addr.Net = "unix"
 		addr.Name = os.ExpandEnv(addr.Name)
@@ -144,6 +167,17 @@ func main() {
 			}
 		}
 
+		if azaleaPath != "" {
+			var root *os.Root
+			if a, err := check.NewAbs(azaleaPath); err != nil {
+				return err
+			} else if root, err = os.OpenRoot(a.String()); err != nil {
+				return err
+			} else if err = rosa.Native().RegisterFS(root.FS()); err != nil {
+				return err
+			}
+		}
+
 		return nil
 	}).Flag(
 		&flagQuiet,
@@ -174,17 +208,30 @@ func main() {
 		"v", command.BoolFlag(false),
 		"Do not suppress verbose output from init",
 	).Flag(
-		&cm.cures,
+		&cm.attr.Cures,
 		"cures", command.IntFlag(0),
 		"Maximum number of dependencies to cure at any given time",
 	).Flag(
-		&cm.jobs,
+		&cm.attr.Jobs,
 		"jobs", command.IntFlag(0),
 		"Preferred number of jobs to run, when applicable",
+	).Flag(
+		&cm.attr.Load,
+		"load-average", command.IntFlag(0),
+		"Preferred load average number, when applicable",
 	).Flag(
 		&cm.base,
 		"d", command.StringFlag("$MBF_CACHE_DIR"),
 		"Directory to store cured artifacts",
+	).Flag(
+		&cm.mirror,
+		"r", command.StringFlag("$MBF_REMOTE"),
+		"URL of mirror service",
+	).Flag(
+		&cm.deep,
+		"deep", command.BoolFlag(false),
+		"Cure all inputs even when the required artifact is available "+
+			"via the mirror service",
 	).Flag(
 		&cm.idle,
 		"sched-idle", command.BoolFlag(false),
@@ -204,10 +251,18 @@ func main() {
 		&flagPT,
 		"parse-time", command.BoolFlag(false),
 		"Print duration of the initial azalea parse",
+	).Flag(
+		&flagDry,
+		"dry", command.BoolFlag(false),
+		"Do not destroy cache entries",
 	).Flag(
 		&flagSourcePath,
 		"source", command.StringFlag(""),
 		"Override hakurei source tree",
+	).Flag(
+		&flagPath,
+		"p", command.StringFlag("$AZALEA_PATH"),
+		"Load additional azalea files",
 	)
 
 	c.NewCommand(
@@ -228,7 +283,7 @@ func main() {
 			if _, err := io.Copy(h, os.Stdin); err != nil {
 				return err
 			}
-			log.Println(pkg.Encode(pkg.Checksum(h.Sum(nil))))
+			fmt.Println(pkg.Encode(pkg.Checksum(h.Sum(nil))))
 			return nil
 		},
 	)
@@ -360,7 +415,10 @@ func main() {
 	)
 
 	{
-		var flagJobs int
+		var (
+			flagJobs    int
+			flagNoBlock bool
+		)
 		c.NewCommand("updates", command.UsageInternal, func([]string) error {
 			var (
 				errsMu sync.Mutex
@@ -379,6 +437,11 @@ func main() {
 							continue
 						}
 
+						if !flagNoBlock && meta.Blocked != "" {
+							msg.Verbosef("%s is blocked: %s", meta.Name, meta.Blocked)
+							continue
+						}
+
 						v, err := meta.GetVersions(ctx)
 						if err != nil {
 							errsMu.Lock()
@@ -419,9 +482,23 @@ func main() {
 			&flagJobs,
 			"j", command.IntFlag(32),
 			"Maximum number of simultaneous connections",
+		).Flag(
+			&flagNoBlock,
+			"ignore-block", command.BoolFlag(false),
+			"Inhibit update blocking",
 		)
 	}
 
+	c.NewCommand("blocked", command.UsageInternal, func([]string) error {
+		for _, p := range rosa.Native().CollectAll() {
+			meta, _ := rosa.Native().Std().Load(p)
+			if meta.Blocked != "" {
+				fmt.Printf("%s: %s\n", meta.Name, meta.Blocked)
+			}
+		}
+		return nil
+	})
+
 	c.NewCommand(
 		"daemon",
 		"Service artifact IR with Rosa OS extensions",
@@ -435,28 +512,118 @@ func main() {
 		},
 	)
 
+	c.NewCommand(
+		"keygen",
+		"Create keypair for local cache",
+		func([]string) error {
+			pub, priv, err := ed25519.GenerateKey(nil)
+			if err != nil {
+				return err
+			}
+
+			return errors.Join(writeFileExcl(filepath.Join(
+				cm.base,
+				"ed25519.pub",
+			), pub, 0444), writeFileExcl(filepath.Join(
+				cm.base,
+				"ed25519",
+			), priv, 0400))
+		},
+	)
+
+	c.NewCommand(
+		"serve",
+		"Export local cache as mirror",
+		func(args []string) error {
+			const shutdownTimeout = 15 * time.Second
+
+			if len(args) != 1 {
+				return errors.New("serve requires 1 argument")
+			}
+
+			var key ed25519.PrivateKey
+			if p, err := os.ReadFile(filepath.Join(cm.base, "ed25519")); err != nil {
+				return err
+			} else if len(p) != ed25519.PrivateKeySize {
+				return errors.New("invalid private key")
+			} else {
+				key = p
+			}
+
+			var h http.Handler
+			if base, err := os.OpenRoot(cm.base); err != nil {
+				return err
+			} else {
+				var mux http.ServeMux
+				rosa.NewMirror(msg, base.FS(), key).Register(&mux)
+				h = &mux
+			}
+
+			server := http.Server{Addr: args[0], Handler: h}
+			go func() {
+				<-ctx.Done()
+				cc, cancel := context.WithTimeout(context.Background(), shutdownTimeout)
+				defer cancel()
+				if err := server.Shutdown(cc); err != nil {
+					log.Fatal(err)
+				}
+			}()
+
+			msg.Verbosef("listening on %q", args[0])
+			err := server.ListenAndServe()
+			if errors.Is(err, http.ErrServerClosed) {
+				err = nil
+			}
+			return err
+		},
+	)
+
+	c.NewCommand(
+		"snapshot",
+		"Populate an empty directory with a static mirror snapshot",
+		func(args []string) error {
+			if len(args) != 1 {
+				return errors.New("snapshot requires 1 argument")
+			}
+
+			var key ed25519.PrivateKey
+			if p, err := os.ReadFile(filepath.Join(cm.base, "ed25519")); err != nil {
+				return err
+			} else if len(p) != ed25519.PrivateKeySize {
+				return errors.New("invalid private key")
+			} else {
+				key = p
+			}
+
+			var m rosa.Mirror
+			if base, err := os.OpenRoot(cm.base); err != nil {
+				return err
+			} else {
+				m = rosa.NewMirror(msg, base.FS(), key)
+			}
+
+		retry:
+			root, err := os.OpenRoot(args[0])
+			if err != nil {
+				if os.IsNotExist(err) {
+					if err = os.MkdirAll(args[0], 0755); err != nil {
+						return err
+					}
+					goto retry
+				}
+				return err
+			}
+
+			go func() { <-ctx.Done(); _ = root.Close() }()
+			return m.Populate(root)
+		},
+	)
+
 	{
-		var (
-			flagGentoo   string
-			flagChecksum string
-		)
 		c.NewCommand(
-			"stage3",
+			"stage4",
 			"Check for toolchain 3-stage non-determinism",
 			func(args []string) (err error) {
-				s := rosa.Std
-				if flagGentoo != "" {
-					s -= 3 // magic number to discourage misuse
-
-					var checksum pkg.Checksum
-					if len(flagChecksum) != 0 {
-						if err = pkg.Decode(&checksum, flagChecksum); err != nil {
-							return
-						}
-					}
-					rosa.Native().SetGentooStage3(flagGentoo, checksum)
-				}
-
 				var (
 					pathname *check.Absolute
 					checksum [2]unique.Handle[pkg.Checksum]
@@ -464,7 +631,7 @@ func main() {
 
 				_llvm := rosa.H("llvm")
 				if err = cm.Do(func(cache *pkg.Cache) (err error) {
-					_, llvm := rosa.Native().New(s - 2).Load(_llvm)
+					_, llvm := rosa.Native().New(rosa.Std - 2).Load(_llvm)
 					pathname, _, err = cache.Cure(llvm)
 					return
 				}); err != nil {
@@ -473,22 +640,32 @@ func main() {
 				log.Println("stage1:", pathname)
 
 				if err = cm.Do(func(cache *pkg.Cache) (err error) {
-					_, llvm := rosa.Native().New(s - 1).Load(_llvm)
-					pathname, checksum[0], err = cache.Cure(llvm)
+					_, llvm := rosa.Native().New(rosa.Std - 1).Load(_llvm)
+					pathname, _, err = cache.Cure(llvm)
 					return
 				}); err != nil {
 					return
 				}
 				log.Println("stage2:", pathname)
+
 				if err = cm.Do(func(cache *pkg.Cache) (err error) {
-					_, llvm := rosa.Native().New(s).Load(_llvm)
-					pathname, checksum[1], err = cache.Cure(llvm)
+					_, llvm := rosa.Native().New(rosa.Std).Load(_llvm)
+					pathname, checksum[0], err = cache.Cure(llvm)
 					return
 				}); err != nil {
 					return
 				}
 				log.Println("stage3:", pathname)
 
+				if err = cm.Do(func(cache *pkg.Cache) (err error) {
+					_, llvm := rosa.Native().New(rosa.Stage3).Load(_llvm)
+					pathname, checksum[1], err = cache.Cure(llvm)
+					return
+				}); err != nil {
+					return
+				}
+				log.Println("stage4:", pathname)
+
 				if checksum[0] != checksum[1] {
 					err = &pkg.ChecksumMismatchError{
 						Got:  checksum[0].Value(),
@@ -496,23 +673,34 @@ func main() {
 					}
 				} else {
 					log.Println(
-						"stage2 is identical to stage3",
+						"stage3 is identical to stage4",
 						"("+pkg.Encode(checksum[0].Value())+")",
 					)
 				}
 				return
 			},
-		).Flag(
-			&flagGentoo,
-			"gentoo", command.StringFlag(""),
-			"Bootstrap from a Gentoo stage3 tarball",
-		).Flag(
-			&flagChecksum,
-			"checksum", command.StringFlag(""),
-			"Checksum of Gentoo stage3 tarball",
 		)
 	}
 
+	c.NewCommand(
+		"all",
+		command.UsageInternal,
+		func([]string) error {
+			all := rosa.Native().CollectAll()
+			a := make(pkg.Collect, len(all))
+			for i, h := range all {
+				_, a[i] = rosa.Native().Std().Load(h)
+			}
+			return cm.Do(func(cache *pkg.Cache) (err error) {
+				_, _, err = cache.Cure(&a)
+				if pkg.IsCollected(err) {
+					err = nil
+				}
+				return
+			})
+		},
+	)
+
 	{
 		var (
 			flagDump    string
@@ -522,9 +710,13 @@ func main() {
 			flagNoReply bool
 			flagFaults  bool
 			flagPop     bool
+			flagRebuild bool
 
 			flagBoot bool
 			flagStd  bool
+
+			flagGentoo   string
+			flagChecksum string
 		)
 		c.NewCommand(
 			"cure",
@@ -541,6 +733,18 @@ func main() {
 					t -= 1
 				}
 
+				if flagGentoo != "" {
+					var checksum pkg.Checksum
+					if len(flagChecksum) != 0 {
+						if err := pkg.Decode(&checksum, flagChecksum); err != nil {
+							return err
+						}
+					}
+					rosa.Native().SetGentooStage3(flagGentoo, checksum)
+
+					t -= 3 // magic number to discourage misuse
+				}
+
 				_, a := rosa.Native().New(t).Load(rosa.ArtifactH(unique.Make(args[0])))
 				if a == nil {
 					return fmt.Errorf("unknown artifact %q", args[0])
@@ -550,13 +754,17 @@ func main() {
 				default:
 					var pathname *check.Absolute
 					err := cm.Do(func(cache *pkg.Cache) (err error) {
-						pathname, _, err = cache.Cure(a)
+						if flagRebuild {
+							pathname, _, err = cache.CureNew(a)
+						} else {
+							pathname, _, err = cache.Cure(a)
+						}
 						return
 					})
 					if err != nil {
 						return err
 					}
-					log.Println(pathname)
+					fmt.Println(pathname)
 
 					if flagExport != "" {
 						msg.Verbosef("exporting %s to %s...", args[0], flagExport)
@@ -568,7 +776,7 @@ func main() {
 							0400,
 						); err != nil {
 							return err
-						} else if _, err = pkg.Flatten(
+						} else if err = pkg.Write(
 							os.DirFS(pathname.String()),
 							".",
 							f,
@@ -604,8 +812,8 @@ func main() {
 						return cache.EnterExec(
 							ctx,
 							a,
-							true, os.Stdin, os.Stdout, os.Stderr,
-							rosa.AbsSystem.Append("bin", "mksh"),
+							"", true, os.Stdin, os.Stdout, os.Stderr,
+							rosa.AbsSystem.Append("bin", "sh"),
 							"sh",
 						)
 					})
@@ -617,7 +825,7 @@ func main() {
 					}
 					pathname, err := cureRemote(ctx, &addr, a, flags)
 					if !flagNoReply && err == nil {
-						log.Println(pathname)
+						fmt.Println(pathname)
 					}
 
 					if errors.Is(err, context.Canceled) {
@@ -711,11 +919,100 @@ func main() {
 			&flagPop,
 			"pop", command.BoolFlag(false),
 			"Display and destroy the most recent fault entry",
+		).Flag(
+			&flagRebuild,
+			"rebuild", command.BoolFlag(false),
+			"Always enter the artifact implementation",
+		).Flag(
+			&flagGentoo,
+			"gentoo", command.StringFlag(""),
+			"Bootstrap from a Gentoo stage3 tarball",
+		).Flag(
+			&flagChecksum,
+			"checksum", command.StringFlag(""),
+			"Checksum of Gentoo stage3 tarball",
 		)
 	}
 
 	c.NewCommand(
-		"clear",
+		"validate",
+		"Repeatedly cure named artifact to validate determinism",
+		func(args []string) error {
+			stage := rosa.Std
+			if len(args) == 3 {
+				switch args[0] {
+				case "boot":
+					stage -= 2
+				case "std":
+					stage -= 1
+
+				default:
+					return fmt.Errorf("invalid stage %q", args[0])
+				}
+				args = args[1:]
+			}
+
+			if len(args) != 2 {
+				return errors.New("validate requires 2 arguments")
+			}
+
+			n, err := strconv.Atoi(args[0])
+			if err != nil {
+				return fmt.Errorf("invalid passes %q", args[0])
+			}
+
+			if n < 2 {
+				return errors.New("validate must rebuild at least twice")
+			}
+
+			_, a := rosa.Native().New(stage).Load(rosa.ArtifactH(unique.Make(args[1])))
+			if a == nil {
+				return fmt.Errorf("unknown artifact %q", args[1])
+			}
+
+			if !a.IsExclusive() && cm.attr.Jobs < 1 {
+				cm.attr.Jobs = runtime.NumCPU()/n + 1
+			}
+
+			res := make([]unique.Handle[pkg.Checksum], n)
+			if err = cm.Do(func(cache *pkg.Cache) error {
+				errs := make([]error, n)
+				var wg sync.WaitGroup
+				for i := range n {
+					wg.Go(func() {
+						_, res[i], errs[i] = cache.CureNew(a)
+					})
+				}
+				wg.Wait()
+				return errors.Join(errs...)
+			}); err != nil {
+				return err
+			}
+
+			for i := range n - 1 {
+				if res[i] == res[i+1] {
+					continue
+				}
+
+				var buf strings.Builder
+				buf.WriteString("nondeterminism:")
+				for _, o := range res {
+					buf.WriteString("\n\t")
+					buf.WriteString(filepath.Join(
+						cm.base,
+						"checksum",
+						pkg.Encode(o.Value()),
+					))
+				}
+				return errors.New(buf.String())
+			}
+			return nil
+		},
+	)
+
+	cleanC := c.New("clean", "Remove unused entries from the cache")
+	cleanC.NewCommand(
+		"fault",
 		"Remove all fault entries from the cache",
 		func([]string) error {
 			return cm.Do(func(*pkg.Cache) error {
@@ -736,6 +1033,58 @@ func main() {
 			})
 		},
 	)
+	cleanC.NewCommand(
+		"checksum",
+		"Remove unreachable checksum entries",
+		func([]string) error {
+			return cm.Do(func(cache *pkg.Cache) error {
+				_, checksums, err := cache.Clean(flagDry, false)
+				log.Printf("destroyed %d entries", len(checksums))
+				return err
+			})
+		},
+	)
+	{
+		var flagDeep bool
+		cleanC.NewCommand(
+			"all",
+			"Remove identifiers not reachable by loaded packages",
+			func([]string) error {
+				return cm.Do(func(cache *pkg.Cache) error {
+					t := rosa.Native().Clone().Std()
+					handles := t.CollectAll()
+
+					flags := t.Flags()
+					a := t.Append(nil, handles...)
+					for arch := range rosa.Arches(nil) {
+						if arch == runtime.GOARCH {
+							continue
+						}
+
+						t.DropCaches(arch, rosa.OptLLVMNoLTO|rosa.OptSkipCheck)
+						a = t.Append(a, handles...)
+						t.DropCaches(arch, flags)
+						a = t.Append(a, handles...)
+					}
+
+					ids, checksums, err := cache.Clean(
+						flagDry,
+						!flagDeep,
+						a...,
+					)
+					log.Printf(
+						"destroyed %d identifier and %d checksum entries",
+						len(ids), len(checksums),
+					)
+					return err
+				})
+			},
+		).Flag(
+			&flagDeep,
+			"deep", command.BoolFlag(false),
+			"Include transitive inputs",
+		)
+	}
 
 	c.NewCommand(
 		"abort",
@@ -754,6 +1103,17 @@ func main() {
 			"shell",
 			"Interactive shell in the specified Rosa OS environment",
 			func(args []string) error {
+				resolvconf := "nameserver 1.1.1.1\nnameserver 1.0.0.1\n"
+				if p, err := os.ReadFile(fhs.AbsEtc.Append(
+					"resolv.conf",
+				).String()); err != nil {
+					if !errors.Is(err, os.ErrNotExist) {
+						return err
+					}
+				} else {
+					resolvconf = unsafe.String(unsafe.SliceData(p), len(p))
+				}
+
 				handles := make([]rosa.ArtifactH, len(args), len(args)+3)
 				for i, arg := range args {
 					handles[i] = rosa.ArtifactH(unique.Make(arg))
@@ -773,112 +1133,42 @@ func main() {
 				)
 
 				root := make(pkg.Collect, 0, 6+len(args))
+				root = append(root, rosa.NewEtc(false))
 				root = rosa.Native().Std().Append(root, handles...)
 
-				if err := cm.Do(func(cache *pkg.Cache) error {
-					_, _, err := cache.Cure(&root)
-					return err
-				}); err == nil {
-					return errors.New("unreachable")
-				} else if !pkg.IsCollected(err) {
-					return err
-				}
-
-				type cureRes struct {
-					pathname *check.Absolute
-					checksum unique.Handle[pkg.Checksum]
-				}
-				cured := make(map[pkg.Artifact]cureRes)
-				for _, a := range root {
-					if err := cm.Do(func(cache *pkg.Cache) error {
-						pathname, checksum, err := cache.Cure(a)
-						if err == nil {
-							cured[a] = cureRes{pathname, checksum}
-						}
-						return err
-					}); err != nil {
-						return err
-					}
-				}
-
-				// explicitly open for direct error-free use from this point
-				if cm.c == nil {
-					if err := cm.open(); err != nil {
-						return err
-					}
-				}
-
-				layers := pkg.PromoteLayers(root, func(a pkg.Artifact) (
-					*check.Absolute,
-					unique.Handle[pkg.Checksum],
-				) {
-					res := cured[a]
-					return res.pathname, res.checksum
-				}, func(i int, d pkg.Artifact) {
-					r := pkg.Encode(cm.c.Ident(d).Value())
-					if s, ok := d.(fmt.Stringer); ok {
-						if name := s.String(); name != "" {
-							r += "-" + name
-						}
-					}
-					msg.Verbosef("promoted layer %d as %s", i, r)
+				return cm.Do(func(cache *pkg.Cache) error {
+					return cache.EnterExec(
+						ctx,
+						pkg.NewExec(
+							"",
+							rosa.Native().Arch(),
+							new(pkg.Checksum),
+							1,
+							flagNet,
+							false,
+							fhs.AbsRoot,
+							[]string{
+								"SHELL=/system/bin/mksh",
+								"PATH=/system/bin",
+								"HOME=/",
+							},
+							fhs.AbsProc.Append("nonexistent"),
+							nil,
+							pkg.Path(fhs.AbsRoot, true, root...),
+							pkg.Path(
+								fhs.AbsEtc.Append("resolv.conf"), false,
+								pkg.NewFile(
+									"resolv.conf",
+									unsafe.Slice(unsafe.StringData(resolvconf), len(resolvconf)),
+								),
+							),
+						),
+						"localhost",
+						flagSession, os.Stdin, os.Stdout, os.Stderr,
+						rosa.AbsSystem.Append("bin", "mksh"),
+						"sh",
+					)
 				})
-
-				z := container.New(ctx, msg)
-				z.WaitDelay = 3 * time.Second
-				z.SeccompPresets = pkg.SeccompPresets
-				z.SeccompFlags |= seccomp.AllowMultiarch
-				z.ParentPerm = 0700
-				z.HostNet = flagNet
-				z.RetainSession = flagSession
-				z.Hostname = "localhost"
-				z.Uid, z.Gid = (1<<10)-1, (1<<10)-1
-				z.Stdin, z.Stdout, z.Stderr = os.Stdin, os.Stdout, os.Stderr
-				z.Quiet = !cm.verboseInit
-				if s, ok := os.LookupEnv("TERM"); ok {
-					z.Env = append(z.Env, "TERM="+s)
-				}
-
-				var tempdir *check.Absolute
-				if s, err := filepath.Abs(os.TempDir()); err != nil {
-					return err
-				} else if tempdir, err = check.NewAbs(s); err != nil {
-					return err
-				}
-
-				z.Dir = fhs.AbsRoot
-				z.Env = []string{
-					"SHELL=/system/bin/mksh",
-					"PATH=/system/bin",
-					"HOME=/",
-				}
-				z.Path = rosa.AbsSystem.Append("bin", "mksh")
-				z.Args = []string{"mksh"}
-				z.
-					OverlayEphemeral(fhs.AbsRoot, layers...).
-					Place(
-						fhs.AbsEtc.Append("hosts"),
-						[]byte("127.0.0.1 localhost\n"),
-					).
-					Place(
-						fhs.AbsEtc.Append("passwd"),
-						[]byte("media_rw:x:1023:1023::/:/system/bin/sh\n"+
-							"nobody:x:65534:65534::/proc/nonexistent:/system/bin/false\n"),
-					).
-					Place(
-						fhs.AbsEtc.Append("group"),
-						[]byte("media_rw:x:1023:\nnobody:x:65534:\n"),
-					).
-					Bind(tempdir, fhs.AbsTmp, std.BindWritable).
-					Proc(fhs.AbsProc).Dev(fhs.AbsDev, true)
-
-				if err := z.Start(); err != nil {
-					return err
-				}
-				if err := z.Serve(); err != nil {
-					return err
-				}
-				return z.Wait()
 			},
 		).Flag(
 			&flagNet,
@@ -906,6 +1196,10 @@ func main() {
 		if w, ok := err.(interface{ Unwrap() []error }); !ok {
 			log.Fatal(err)
 		} else {
+			if _, ok = w.(pkg.InputError); ok {
+				log.Fatal(w)
+			}
+
 			errs := w.Unwrap()
 			for i, e := range errs {
 				if i == len(errs)-1 {

cmd/sharefs/fuse.go

@@ -508,8 +508,8 @@ func _main(s ...string) (exitCode int) {
 
 		if !z.AllowOrphan {
 			if err := z.Wait(); err != nil {
-				var exitError *exec.ExitError
-				if !errors.As(err, &exitError) || exitError == nil {
+				exitError, ok := errors.AsType[*exec.ExitError](err)
+				if !ok || exitError == nil {
 					log.Println(err)
 					return 5
 				}

command/builder.go

@@ -13,6 +13,7 @@ func New(output io.Writer, logf LogFunc, name string, early HandlerFunc) Command
 	return c
 }
 
+// newNode initialises a subcommand tree and returns its address.
 func newNode(output io.Writer, logf LogFunc, name, usage string) *node {
 	n := &node{
 		name: name, usage: usage,
@@ -22,8 +23,8 @@ func newNode(output io.Writer, logf LogFunc, name, usage string) *node {
 	n.set.SetOutput(output)
 	n.set.Usage = func() {
 		_ = n.writeHelp()
-		if n.suffix.Len() > 0 {
-			_, _ = fmt.Fprintln(output, "Flags:")
+		if len(n.suffix) > 0 {
+			_, _ = fmt.Fprintln(output, "flags:")
 			n.set.PrintDefaults()
 			_, _ = fmt.Fprintln(output)
 		}

command/builder_test.go

@@ -18,8 +18,14 @@ func TestBuild(t *testing.T) {
 
 	t.Run("direct zero length", func(t *testing.T) {
 		wantPanic := "invalid subcommand"
-		t.Run("zero length name", func(t *testing.T) { defer checkRecover(t, "Command", wantPanic); c.Command("", "usage", stubHandler) })
-		t.Run("zero length usage", func(t *testing.T) { defer checkRecover(t, "Command", wantPanic); c.Command("name", "", stubHandler) })
+		t.Run("zero length name", func(t *testing.T) {
+			defer checkRecover(t, "Command", wantPanic)
+			c.Command("", "usage", stubHandler)
+		})
+		t.Run("zero length usage", func(t *testing.T) {
+			defer checkRecover(t, "Command", wantPanic)
+			c.Command("name", "", stubHandler)
+		})
 	})
 
 	t.Run("direct adopt unique names", func(t *testing.T) {
@@ -34,8 +40,14 @@ func TestBuild(t *testing.T) {
 
 	t.Run("zero length", func(t *testing.T) {
 		wantPanic := "invalid subcommand tree"
-		t.Run("zero length name", func(t *testing.T) { defer checkRecover(t, "New", wantPanic); c.New("", "usage") })
-		t.Run("zero length usage", func(t *testing.T) { defer checkRecover(t, "New", wantPanic); c.New("name", "") })
+		t.Run("zero length name", func(t *testing.T) {
+			defer checkRecover(t, "New", wantPanic)
+			c.New("", "usage")
+		})
+		t.Run("zero length usage", func(t *testing.T) {
+			defer checkRecover(t, "New", wantPanic)
+			c.New("name", "")
+		})
 	})
 
 	t.Run("direct adopt unique names", func(t *testing.T) {

command/command.go

@@ -6,36 +6,43 @@ import (
 	"strings"
 )
 
-// UsageInternal causes the command to be hidden from help text when set as the usage string.
-const UsageInternal = "internal"
+// UsageInternal is a special usage string that hides the command from the
+// generated help message.
+const UsageInternal = "\x00"
 
 type (
 	// HandlerFunc is called when matching a directly handled subcommand tree.
 	HandlerFunc = func(args []string) error
 
-	// LogFunc is the function signature of a printf function.
+	// LogFunc is the function signature of a printf function. The zero value
+	// implies [log.Printf].
 	LogFunc = func(format string, a ...any)
 
-	// FlagDefiner is a deferred flag definer value, usually encapsulating the default value.
+	// FlagDefiner is a deferred flag definer value, usually encapsulating the
+	// default value.
 	FlagDefiner interface {
 		// Define defines the flag in set.
 		Define(b *strings.Builder, set *flag.FlagSet, p any, name, usage string)
 	}
 
+	// A Flag is satisfied by command objects capable of receiving flags.
 	Flag[T any] interface {
 		// Flag defines a generic flag type in Node's flag set.
 		Flag(p any, name string, value FlagDefiner, usage string) T
 	}
 
+	// A Command is the root of a command tree.
 	Command interface {
 		Parse(arguments []string) error
 
-		// MustParse determines exit outcomes for Parse errors
-		// and calls handleError if [HandlerFunc] returns a non-nil error.
+		// MustParse determines exit outcomes for Parse errors and calls
+		// handleError if [HandlerFunc] returns a non-nil error.
 		MustParse(arguments []string, handleError func(error))
 
 		baseNode[Command]
 	}
+
+	// A Node is a subcommand under a [Command].
 	Node baseNode[Node]
 
 	baseNode[T any] interface {
@@ -53,3 +60,16 @@ type (
 		Flag[T]
 	}
 )
+
+// rootNode satisfies baseNode for [Command].
+type rootNode struct{ *node }
+
+func (r rootNode) Command(name, usage string, f HandlerFunc) Command {
+	r.node.Command(name, usage, f)
+	return r
+}
+
+func (r rootNode) Flag(p any, name string, value FlagDefiner, usage string) Command {
+	r.node.Flag(p, name, value, usage)
+	return r
+}

command/flag.go

@@ -16,7 +16,13 @@ func (e FlagError) Is(target error) bool {
 }
 
 func (n *node) Flag(p any, name string, value FlagDefiner, usage string) Node {
-	value.Define(&n.suffix, n.set, p, name, usage)
+	var buf strings.Builder
+	value.Define(&buf, n.set, p, name, usage)
+	s := buf.String()
+	if len(s) > 0 && s[0] == ' ' {
+		s = s[1:]
+	}
+	n.suffix = append(n.suffix, s)
 	return n
 }
 

command/help.go

@@ -1,6 +1,7 @@
 package command
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
 	"io"
@@ -13,14 +14,31 @@ var ErrHelp = errors.New("help requested")
 func (n *node) PrintHelp() { _ = n.writeHelp() }
 
 func (n *node) writeHelp() error {
+	prefix := strings.Join(append(n.prefix, n.name), " ")
+	var buf strings.Builder
+	offset := 7 + len(prefix)
+	line := offset + 14
+	w := bytes.Repeat([]byte{' '}, offset+1)
+	w[0] = '\n'
+
+	for _, flag := range n.suffix {
+		line += len(flag) + 1
+		if line >= 80 {
+			line = offset + len(flag) + 1
+			buf.Write(w)
+		}
+		buf.WriteByte(' ')
+		buf.WriteString(flag)
+	}
+
 	if _, err := fmt.Fprintf(n.out,
-		"\nUsage:\t%s [-h | --help]%s COMMAND [OPTIONS]\n",
-		strings.Join(append(n.prefix, n.name), " "), &n.suffix,
+		"usage: %s [-h | --help]%s <command> [<args>]\n",
+		prefix, &buf,
 	); err != nil {
 		return err
 	}
 	if n.child != nil {
-		if _, err := fmt.Fprint(n.out, "\nCommands:\n"); err != nil {
+		if _, err := fmt.Fprint(n.out, "\ncommands:\n"); err != nil {
 			return err
 		}
 	}

command/node.go

@@ -3,9 +3,9 @@ package command
 import (
 	"flag"
 	"io"
-	"strings"
 )
 
+// A node represents a command.
 type node struct {
 	child, next *node
 	name, usage string
@@ -13,13 +13,16 @@ type node struct {
 	out  io.Writer
 	logf LogFunc
 
+	// Names of commands preceding node.
 	prefix []string
-	suffix strings.Builder
+	// Short user-facing representations of flags received by node.
+	suffix []string
 
 	f   HandlerFunc
 	set *flag.FlagSet
 }
 
+// adopt adds v as the last child of n.
 func (n *node) adopt(v *node) bool {
 	if n.child != nil {
 		return n.child.append(v)
@@ -28,6 +31,7 @@ func (n *node) adopt(v *node) bool {
 	return true
 }
 
+// append adds v as the last sibling of n.
 func (n *node) append(v *node) bool {
 	if n.name == v.name {
 		return false

command/parse.go

@@ -91,8 +91,8 @@ func (n *node) MustParse(arguments []string, handleError func(error)) {
 	case ErrEmptyTree:
 		os.Exit(1)
 	default:
-		var flagError FlagError
-		if !errors.As(err, &flagError) { // returned by HandlerFunc
+		flagError, ok := errors.AsType[FlagError](err)
+		if !ok { // returned by HandlerFunc
 			handleError(err)
 			os.Exit(1)
 		}

command/parse_test.go

@@ -70,7 +70,7 @@ func TestParse(t *testing.T) {
 			"d=0 out of order string flag",
 			buildTestCommand,
 			[]string{"string", "--string", "64d3b4b7b21788585845060e2199a78f"},
-			"flag provided but not defined: -string\n\nUsage:\ttest string [-h | --help] COMMAND [OPTIONS]\n\n", "",
+			"flag provided but not defined: -string\nusage: test string [-h | --help] <command> [<args>]\n\n", "",
 			errors.New("flag provided but not defined: -string"),
 		},
 		{
@@ -120,7 +120,7 @@ func TestParse(t *testing.T) {
 			"d=1 empty sub help",
 			buildTestCommand,
 			[]string{"empty", "-h"},
-			"\nUsage:\ttest empty [-h | --help] COMMAND [OPTIONS]\n\n", "", flag.ErrHelp,
+			"usage: test empty [-h | --help] <command> [<args>]\n\n", "", flag.ErrHelp,
 		},
 		{
 			"d=1 no match",
@@ -151,10 +151,10 @@ func TestParse(t *testing.T) {
 			"d=0 help",
 			buildTestCommand,
 			[]string{},
-			`
-Usage:	test [-h | --help] [-v] [--fail] [--string <value>] [--int <int>] [--repeat <value>] COMMAND [OPTIONS]
+			`usage: test [-h | --help] [-v] [--fail] [--string <value>] [--int <int>]
+            [--repeat <value>] <command> [<args>]
 
-Commands:
+commands:
     error      return an error
     print      wraps Fprint
     string     print string passed by flag
@@ -171,10 +171,10 @@ Commands:
 			"d=0 help flag",
 			buildTestCommand,
 			[]string{"-h"},
-			`
-Usage:	test [-h | --help] [-v] [--fail] [--string <value>] [--int <int>] [--repeat <value>] COMMAND [OPTIONS]
+			`usage: test [-h | --help] [-v] [--fail] [--string <value>] [--int <int>]
+            [--repeat <value>] <command> [<args>]
 
-Commands:
+commands:
     error      return an error
     print      wraps Fprint
     string     print string passed by flag
@@ -185,7 +185,7 @@ Commands:
     succeed    this command succeeds
     deep       top level of command tree with various levels
 
-Flags:
+flags:
   -fail
     	fail early
   -int int
@@ -203,10 +203,9 @@ Flags:
 			"d=1 help",
 			buildTestCommand,
 			[]string{"join"},
-			`
-Usage:	test join [-h | --help] COMMAND [OPTIONS]
+			`usage: test join [-h | --help] <command> [<args>]
 
-Commands:
+commands:
     out    write result to wout
     log    log result to wlog
 
@@ -216,10 +215,9 @@ Commands:
 			"d=1 help flag",
 			buildTestCommand,
 			[]string{"join", "-h"},
-			`
-Usage:	test join [-h | --help] COMMAND [OPTIONS]
+			`usage: test join [-h | --help] <command> [<args>]
 
-Commands:
+commands:
     out    write result to wout
     log    log result to wlog
 
@@ -230,10 +228,9 @@ Commands:
 			"d=2 help",
 			buildTestCommand,
 			[]string{"deep", "d=2"},
-			`
-Usage:	test deep d=2 [-h | --help] COMMAND [OPTIONS]
+			`usage: test deep d=2 [-h | --help] <command> [<args>]
 
-Commands:
+commands:
     d=3    relative third level
 
 `, "", command.ErrHelp,
@@ -242,10 +239,9 @@ Commands:
 			"d=2 help flag",
 			buildTestCommand,
 			[]string{"deep", "d=2", "-h"},
-			`
-Usage:	test deep d=2 [-h | --help] COMMAND [OPTIONS]
+			`usage: test deep d=2 [-h | --help] <command> [<args>]
 
-Commands:
+commands:
     d=3    relative third level
 
 `, "", flag.ErrHelp,
@@ -261,7 +257,7 @@ Commands:
 				t.Errorf("Parse: error = %v; wantErr %v", err, tc.wantErr)
 			}
 			if got := wout.String(); got != tc.want {
-				t.Errorf("Parse: %s want %s", got, tc.want)
+				t.Errorf("Parse:\n%s\nwant\n%s", got, tc.want)
 			}
 			if gotLog := wlog.String(); gotLog != tc.wantLog {
 				t.Errorf("Parse: log = %s wantLog %s", gotLog, tc.wantLog)

command/wrap.go

@@ -1,14 +0,0 @@
-package command
-
-// the top level node wants [Command] returned for its builder methods
-type rootNode struct{ *node }
-
-func (r rootNode) Command(name, usage string, f HandlerFunc) Command {
-	r.node.Command(name, usage, f)
-	return r
-}
-
-func (r rootNode) Flag(p any, name string, value FlagDefiner, usage string) Command {
-	r.node.Flag(p, name, value, usage)
-	return r
-}

container/container.go

@@ -154,11 +154,8 @@ func (e *StartError) Error() string {
 		return e.Step
 	}
 
-	{
-		var syscallError *os.SyscallError
-		if errors.As(e.Err, &syscallError) && syscallError != nil {
-			return e.Step + " " + syscallError.Error()
-		}
+	if se, ok := errors.AsType[*os.SyscallError](e.Err); ok && se != nil {
+		return e.Step + " " + se.Error()
 	}
 
 	return e.Step + ": " + e.Err.Error()

container/dispatcher_test.go

@@ -235,8 +235,6 @@ func checkOpBehaviour(t *testing.T, testCases []opBehaviourTestCase) {
 	})
 }
 
-func sliceAddr[S any](s []S) *[]S { return &s }
-
 func newCheckedFile(t *testing.T, name, wantData string, closeErr error) osFile {
 	f := &checkedOsFile{t: t, name: name, want: wantData, closeErr: closeErr}
 	// check happens in Close, and cleanup is not guaranteed to run, so relying

container/errors.go

@@ -46,9 +46,8 @@ func messageFromError(err error) (m string, ok bool) {
 // 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
+	if e, ok := errors.AsType[T](err); ok {
+		return prefix + e.Error(), true
 	}
 	return zeroString, false
 }
@@ -58,9 +57,8 @@ 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
+	if e, ok := errors.AsType[T](err); ok && e != nil {
+		return prefix + e.Error(), true
 	}
 	return zeroString, false
 }
@@ -109,8 +107,8 @@ func optionalErrorUnwrap(err error) 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) {
+	errno, ok := errors.AsType[syscall.Errno](err)
+	if !ok {
 		return 0, &os.PathError{Op: op, Path: path, Err: err}
 	}
 	return errno, nil

container/init_test.go

@@ -95,7 +95,7 @@ func TestInitEntrypoint(t *testing.T) {
 					Uid:            1 << 16,
 					Gid:            1 << 15,
 					Hostname:       "hakurei-check",
-					Ops:            (*Ops)(sliceAddr(make(Ops, 1))),
+					Ops:            new(make(Ops, 1)),
 					SeccompRules:   make([]std.NativeRule, 0),
 					SeccompPresets: std.PresetStrict,
 					RetainSession:  true,
@@ -123,7 +123,7 @@ func TestInitEntrypoint(t *testing.T) {
 					Uid:            1 << 16,
 					Gid:            1 << 15,
 					Hostname:       "hakurei-check",
-					Ops:            (*Ops)(sliceAddr(make(Ops, 1))),
+					Ops:            new(make(Ops, 1)),
 					SeccompRules:   make([]std.NativeRule, 0),
 					SeccompPresets: std.PresetStrict,
 					RetainSession:  true,
@@ -152,7 +152,7 @@ func TestInitEntrypoint(t *testing.T) {
 					Uid:            1 << 16,
 					Gid:            1 << 15,
 					Hostname:       "hakurei-check",
-					Ops:            (*Ops)(sliceAddr(make(Ops, 1))),
+					Ops:            new(make(Ops, 1)),
 					SeccompRules:   make([]std.NativeRule, 0),
 					SeccompPresets: std.PresetStrict,
 					RetainSession:  true,
@@ -182,7 +182,7 @@ func TestInitEntrypoint(t *testing.T) {
 					Uid:            1 << 16,
 					Gid:            1 << 15,
 					Hostname:       "hakurei-check",
-					Ops:            (*Ops)(sliceAddr(make(Ops, 1))),
+					Ops:            new(make(Ops, 1)),
 					SeccompRules:   make([]std.NativeRule, 0),
 					SeccompPresets: std.PresetStrict,
 					RetainSession:  true,
@@ -213,7 +213,7 @@ func TestInitEntrypoint(t *testing.T) {
 					Uid:            1 << 16,
 					Gid:            1 << 15,
 					Hostname:       "hakurei-check",
-					Ops:            (*Ops)(sliceAddr(make(Ops, 1))),
+					Ops:            new(make(Ops, 1)),
 					SeccompRules:   make([]std.NativeRule, 0),
 					SeccompPresets: std.PresetStrict,
 					RetainSession:  true,
@@ -245,7 +245,7 @@ func TestInitEntrypoint(t *testing.T) {
 					Uid:            1 << 16,
 					Gid:            1 << 15,
 					Hostname:       "hakurei-check",
-					Ops:            (*Ops)(sliceAddr(make(Ops, 1))),
+					Ops:            new(make(Ops, 1)),
 					SeccompRules:   make([]std.NativeRule, 0),
 					SeccompPresets: std.PresetStrict,
 					RetainSession:  true,
@@ -279,7 +279,7 @@ func TestInitEntrypoint(t *testing.T) {
 					Uid:            1 << 16,
 					Gid:            1 << 15,
 					Hostname:       "hakurei-check",
-					Ops:            (*Ops)(sliceAddr(make(Ops, 1))),
+					Ops:            new(make(Ops, 1)),
 					SeccompRules:   make([]std.NativeRule, 0),
 					SeccompPresets: std.PresetStrict,
 					RetainSession:  true,
@@ -315,7 +315,7 @@ func TestInitEntrypoint(t *testing.T) {
 					Uid:            1 << 16,
 					Gid:            1 << 15,
 					Hostname:       "hakurei-check",
-					Ops:            (*Ops)(sliceAddr(make(Ops, 1))),
+					Ops:            new(make(Ops, 1)),
 					SeccompRules:   make([]std.NativeRule, 0),
 					SeccompPresets: std.PresetStrict,
 					RetainSession:  true,

ext/ext_test.go

@@ -39,7 +39,7 @@ func TestSyscall(t *testing.T) {
 					t.Errorf("Unmarshal: %v, want %v", got, tc.want)
 				}
 			})
-			if errors.As(tc.err, new(ext.SyscallNameError)) {
+			if _, ok := errors.AsType[ext.SyscallNameError](tc.err); ok {
 				return
 			}
 

go.mod

@@ -1,3 +1,3 @@
 module hakurei.app
 
-go 1.26
+go 1.27

hst/container.go

@@ -2,6 +2,7 @@ package hst
 
 import (
 	"encoding/json"
+	"fmt"
 	"strings"
 	"syscall"
 	"time"
@@ -64,10 +65,14 @@ const (
 	// 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.
 	FMapRealUID
+	// FNoPlace disables placement of /etc/passwd and /etc/group.
+	FNoPlace
 
 	// FDevice mount /dev/ from the init mount namespace as is in the container
 	// mount namespace.
 	FDevice
+	// FCoverRun covers /run/ in the container mount namespace early.
+	FCoverRun
 
 	// FShareRuntime shares XDG_RUNTIME_DIR between containers under the same identity.
 	FShareRuntime
@@ -98,8 +103,12 @@ func (flags Flags) String() string {
 		return "tty"
 	case FMapRealUID:
 		return "mapuid"
+	case FNoPlace:
+		return "noplace"
 	case FDevice:
 		return "device"
+	case FCoverRun:
+		return "cover_run"
 	case FShareRuntime:
 		return "runtime"
 	case FShareTmpdir:
@@ -161,6 +170,10 @@ type ContainerConfig struct {
 	Flags Flags `json:"-"`
 }
 
+func (c *ContainerConfig) GoString() string {
+	return fmt.Sprintf("&%#v", *c)
+}
+
 // ContainerConfigF is [ContainerConfig] stripped of its methods.
 //
 // The [ContainerConfig.Flags] field does not survive a [json] round trip.
@@ -188,9 +201,13 @@ type containerConfigJSON = struct {
 
 	// Corresponds to [FMapRealUID].
 	MapRealUID bool `json:"map_real_uid"`
+	// Corresponds to [FNoPlace].
+	NoPlace bool `json:"noplace,omitempty"`
 
 	// Corresponds to [FDevice].
 	Device bool `json:"device,omitempty"`
+	// Corresponds to [FCoverRun].
+	CoverRun bool `json:"cover_run,omitempty"`
 
 	// Corresponds to [FShareRuntime].
 	ShareRuntime bool `json:"share_runtime,omitempty"`
@@ -213,7 +230,9 @@ func (c *ContainerConfig) MarshalJSON() ([]byte, error) {
 		Tty:           c.Flags&FTty != 0,
 		Multiarch:     c.Flags&FMultiarch != 0,
 		MapRealUID:    c.Flags&FMapRealUID != 0,
+		NoPlace:       c.Flags&FNoPlace != 0,
 		Device:        c.Flags&FDevice != 0,
+		CoverRun:      c.Flags&FCoverRun != 0,
 		ShareRuntime:  c.Flags&FShareRuntime != 0,
 		ShareTmpdir:   c.Flags&FShareTmpdir != 0,
 	})
@@ -254,9 +273,15 @@ func (c *ContainerConfig) UnmarshalJSON(data []byte) error {
 	if v.MapRealUID {
 		c.Flags |= FMapRealUID
 	}
+	if v.NoPlace {
+		c.Flags |= FNoPlace
+	}
 	if v.Device {
 		c.Flags |= FDevice
 	}
+	if v.CoverRun {
+		c.Flags |= FCoverRun
+	}
 	if v.ShareRuntime {
 		c.Flags |= FShareRuntime
 	}

hst/container_test.go

@@ -21,8 +21,8 @@ func TestFlagsString(t *testing.T) {
 	}{
 		{"none", 0, "none"},
 		{"none high", hst.FAll + 1, "none"},
-		{"all", hst.FAll, "multiarch, compat, devel, userns, net, abstract, tty, mapuid, device, runtime, tmpdir"},
-		{"all high", math.MaxUint, "multiarch, compat, devel, userns, net, abstract, tty, mapuid, device, runtime, tmpdir"},
+		{"all", hst.FAll, "multiarch, compat, devel, userns, net, abstract, tty, mapuid, noplace, device, cover_run, runtime, tmpdir"},
+		{"all high", math.MaxUint, "multiarch, compat, devel, userns, net, abstract, tty, mapuid, noplace, device, cover_run, runtime, tmpdir"},
 	}
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
@@ -53,7 +53,7 @@ func TestContainerConfig(t *testing.T) {
 		{"hostnet hostabstract mapuid", &hst.ContainerConfig{Flags: hst.FHostNet | hst.FHostAbstract | hst.FMapRealUID},
 			`{"env":null,"filesystem":null,"shell":null,"home":null,"args":null,"host_net":true,"host_abstract":true,"map_real_uid":true}`},
 		{"all", &hst.ContainerConfig{Flags: hst.FAll},
-			`{"env":null,"filesystem":null,"shell":null,"home":null,"args":null,"seccomp_compat":true,"devel":true,"userns":true,"host_net":true,"host_abstract":true,"tty":true,"multiarch":true,"map_real_uid":true,"device":true,"share_runtime":true,"share_tmpdir":true}`},
+			`{"env":null,"filesystem":null,"shell":null,"home":null,"args":null,"seccomp_compat":true,"devel":true,"userns":true,"host_net":true,"host_abstract":true,"tty":true,"multiarch":true,"map_real_uid":true,"noplace":true,"device":true,"cover_run":true,"share_runtime":true,"share_tmpdir":true}`},
 	}
 
 	for _, tc := range testCases {

hst/dbus.go

@@ -1,6 +1,7 @@
 package hst
 
 import (
+	"fmt"
 	"strconv"
 	"strings"
 )
@@ -61,6 +62,10 @@ type BusConfig struct {
 	Filter bool `json:"filter"`
 }
 
+func (c *BusConfig) GoString() string {
+	return fmt.Sprintf("&%#v", *c)
+}
+
 // Interfaces iterates over all interface strings specified in [BusConfig].
 func (c *BusConfig) Interfaces(yield func(string) bool) {
 	if c == nil {

hst/fs.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"os"
 	"reflect"
+	"strings"
 
 	"hakurei.app/check"
 )
@@ -36,6 +37,8 @@ type Ops interface {
 	Bind(source, target *check.Absolute, flags int) Ops
 	// Overlay appends an op that mounts the overlay pseudo filesystem.
 	Overlay(target, state, work *check.Absolute, layers ...*check.Absolute) Ops
+	// OverlayEphemeral appends a MountOverlayOp with an ephemeral upperdir and workdir.
+	OverlayEphemeral(target *check.Absolute, layers ...*check.Absolute) Ops
 	// OverlayReadonly appends an op that mounts the overlay pseudo filesystem readonly.
 	OverlayReadonly(target *check.Absolute, layers ...*check.Absolute) Ops
 
@@ -78,17 +81,17 @@ type FSImplError struct{ Value FilesystemConfig }
 
 func (f FSImplError) Error() string {
 	implType := reflect.TypeOf(f.Value)
-	var name string
-	for implType != nil && implType.Kind() == reflect.Ptr {
-		name += "*"
+	var buf strings.Builder
+	for implType != nil && implType.Kind() == reflect.Pointer {
+		buf.WriteByte('*')
 		implType = implType.Elem()
 	}
 	if implType != nil {
-		name += implType.Name()
+		buf.WriteString(implType.Name())
 	} else {
-		name += "nil"
+		buf.WriteString("nil")
 	}
-	return fmt.Sprintf("implementation %s not supported", name)
+	return "implementation " + buf.String() + " not supported"
 }
 
 // FilesystemConfigJSON is the [json] adapter for [FilesystemConfig].

hst/fs_test.go

@@ -3,6 +3,7 @@ package hst_test
 import (
 	"encoding/json"
 	"errors"
+	"fmt"
 	"os"
 	"reflect"
 	"strings"
@@ -103,7 +104,7 @@ func TestFilesystemConfigJSON(t *testing.T) {
 			t.Run("marshal", func(t *testing.T) {
 				t.Parallel()
 				wantErr := tc.wantErr
-				if errors.As(wantErr, new(hst.FSTypeError)) {
+				if _, ok := errors.AsType[hst.FSTypeError](wantErr); ok {
 					// for unsupported implementation tc
 					wantErr = hst.FSImplError{Value: stubFS{"cat"}}
 				}
@@ -139,7 +140,7 @@ func TestFilesystemConfigJSON(t *testing.T) {
 			t.Run("unmarshal", func(t *testing.T) {
 				t.Parallel()
 				if tc.data == "\x00" && tc.sData == "\x00" {
-					if errors.As(tc.wantErr, new(hst.FSImplError)) {
+					if _, ok := errors.AsType[hst.FSImplError](tc.wantErr); ok {
 						// this error is only returned on marshal
 						return
 					}
@@ -283,11 +284,11 @@ func checkFs(t *testing.T, testCases []fsTestCase) {
 				if !reflect.DeepEqual(ops, &tc.ops) {
 					gotString := new(strings.Builder)
 					for _, op := range *ops {
-						gotString.WriteString("\n" + op.String())
+						gotString.WriteString("\n" + fmt.Sprintf("%#v", op))
 					}
 					wantString := new(strings.Builder)
 					for _, op := range tc.ops {
-						wantString.WriteString("\n" + op.String())
+						wantString.WriteString("\n" + fmt.Sprintf("%#v", op))
 					}
 					t.Errorf("Apply: %s, want %s", gotString, wantString)
 				}
@@ -339,6 +340,10 @@ func (p opsAdapter) Overlay(target, state, work *check.Absolute, layers ...*chec
 	return opsAdapter{p.Ops.Overlay(target, state, work, layers...)}
 }
 
+func (p opsAdapter) OverlayEphemeral(target *check.Absolute, layers ...*check.Absolute) hst.Ops {
+	return opsAdapter{p.Ops.OverlayEphemeral(target, layers...)}
+}
+
 func (p opsAdapter) OverlayReadonly(target *check.Absolute, layers ...*check.Absolute) hst.Ops {
 	return opsAdapter{p.Ops.OverlayReadonly(target, layers...)}
 }

hst/fsephemeral.go

@@ -43,18 +43,13 @@ func (e *FSEphemeral) Apply(z *ApplyState) {
 		return
 	}
 
-	size := e.Size
-	if size < 0 {
-		size = 0
-	}
-
 	perm := e.Perm
 	if perm == 0 {
 		perm = fsEphemeralDefaultPerm
 	}
 
 	if e.Write {
-		z.Tmpfs(e.Target, size, perm)
+		z.Tmpfs(e.Target, max(e.Size, 0), perm)
 	} else {
 		z.Readonly(e.Target, perm)
 	}

hst/fsoverlay.go

@@ -2,6 +2,7 @@ package hst
 
 import (
 	"encoding/gob"
+	"slices"
 	"strings"
 
 	"hakurei.app/check"
@@ -40,7 +41,7 @@ func (o *FSOverlay) Valid() bool {
 	}
 
 	if o.Upper != nil { // rw
-		return o.Work != nil && len(o.Lower) > 0
+		return o.Work != nil || len(o.Lower) > 0
 	} else { // ro
 		return len(o.Lower) >= 2
 	}
@@ -58,8 +59,11 @@ func (o *FSOverlay) Host() []*check.Absolute {
 		return nil
 	}
 	p := make([]*check.Absolute, 0, 2+len(o.Lower))
-	if o.Upper != nil && o.Work != nil {
-		p = append(p, o.Upper, o.Work)
+	if o.Upper != nil {
+		p = append(p, o.Upper)
+		if o.Work != nil {
+			p = append(p, o.Work)
+		}
 	}
 	p = append(p, o.Lower...)
 	return p
@@ -70,11 +74,18 @@ func (o *FSOverlay) Apply(z *ApplyState) {
 		return
 	}
 
-	if o.Upper != nil && o.Work != nil {
-		z.Overlay(o.Target, o.Upper, o.Work, o.Lower...)
+	if o.Upper != nil {
 		if o.Target.Is(fhs.AbsRoot) {
 			z.NoRemountRoot = true
 		}
+		if o.Work != nil {
+			z.Overlay(o.Target, o.Upper, o.Work, o.Lower...)
+		} else {
+			z.OverlayEphemeral(o.Target, slices.Concat(
+				[]*check.Absolute{o.Upper},
+				o.Lower,
+			)...)
+		}
 	} else {
 		z.OverlayReadonly(o.Target, o.Lower...)
 	}
@@ -90,12 +101,19 @@ func (o *FSOverlay) String() string {
 		lower[i] = check.EscapeOverlayDataSegment(a.String())
 	}
 
-	if o.Upper != nil && o.Work != nil {
-		return "w*" + strings.Join(append([]string{
+	if o.Upper != nil {
+		if o.Work != nil {
+			return "w*" + strings.Join(append([]string{
+				check.EscapeOverlayDataSegment(o.Target.String()),
+				check.EscapeOverlayDataSegment(o.Upper.String()),
+				check.EscapeOverlayDataSegment(o.Work.String())},
+				lower...), check.SpecialOverlayPath)
+		}
+		return "e*" + strings.Join(append([]string{
 			check.EscapeOverlayDataSegment(o.Target.String()),
-			check.EscapeOverlayDataSegment(o.Upper.String()),
-			check.EscapeOverlayDataSegment(o.Work.String())},
+			check.EscapeOverlayDataSegment(o.Upper.String())},
 			lower...), check.SpecialOverlayPath)
+
 	} else {
 		return "*" + strings.Join(append([]string{
 			check.EscapeOverlayDataSegment(o.Target.String())},

hst/fsoverlay_test.go

@@ -5,6 +5,7 @@ import (
 
 	"hakurei.app/check"
 	"hakurei.app/container"
+	"hakurei.app/fhs"
 	"hakurei.app/hst"
 )
 
@@ -14,7 +15,7 @@ func TestFSOverlay(t *testing.T) {
 	checkFs(t, []fsTestCase{
 		{"nil", (*hst.FSOverlay)(nil), false, nil, nil, nil, "<invalid>"},
 		{"nil lower", &hst.FSOverlay{Target: m("/etc"), Lower: []*check.Absolute{nil}}, false, nil, nil, nil, "<invalid>"},
-		{"zero lower", &hst.FSOverlay{Target: m("/etc"), Upper: m("/"), Work: m("/")}, false, nil, nil, nil, "<invalid>"},
+		{"zero lower", &hst.FSOverlay{Target: m("/etc"), Work: m("/")}, false, nil, nil, nil, "<invalid>"},
 		{"zero lower ro", &hst.FSOverlay{Target: m("/etc")}, false, nil, nil, nil, "<invalid>"},
 		{"short lower", &hst.FSOverlay{Target: m("/etc"), Lower: ms("/etc")}, false, nil, nil, nil, "<invalid>"},
 
@@ -62,5 +63,16 @@ func TestFSOverlay(t *testing.T) {
 			Work:   m("/tmp/work"),
 		}}, m("/"), ms("/tmp/upper", "/tmp/work", "/tmp/.src0", "/tmp/.src1"),
 			"w*/:/tmp/upper:/tmp/work:/tmp/.src0:/tmp/.src1"},
+
+		{"ephemeral", &hst.FSOverlay{
+			Target: m("/"),
+			Lower:  ms("/tmp/.src0", "/tmp/.src1"),
+			Upper:  m("/tmp/upper"),
+		}, true, container.Ops{&container.MountOverlayOp{
+			Target: m("/"),
+			Lower:  ms("/tmp/upper", "/tmp/.src0", "/tmp/.src1"),
+			Upper:  fhs.AbsRoot,
+		}}, m("/"), ms("/tmp/upper", "/tmp/.src0", "/tmp/.src1"),
+			"e*/:/tmp/upper:/tmp/.src0:/tmp/.src1"},
 	})
 }

hst/hst_test.go

@@ -244,7 +244,9 @@ func TestTemplate(t *testing.T) {
 		"tty": true,
 		"multiarch": true,
 		"map_real_uid": true,
+		"noplace": true,
 		"device": true,
+		"cover_run": true,
 		"share_runtime": true,
 		"share_tmpdir": true
 	}

internal/dbus/address.go

@@ -80,7 +80,7 @@ func unescapeValue(v []byte) (val []byte, errno ParseError) {
 			continue
 		}
 
-		if ib := bytes.IndexByte([]byte("-_/.\\*"), b); ib != -1 { // - // _/.\*
+		if found := bytes.Contains([]byte("-_/.\\*"), []byte{b}); found { // - // _/.\*
 			goto opt
 		} else if b >= '0' && b <= '9' { // 0-9
 			goto opt
@@ -101,7 +101,7 @@ func unescapeValue(v []byte) (val []byte, errno ParseError) {
 			break
 		}
 		if c, err := hex.Decode(val[i:i+1], v[iu+1:iu+3]); err != nil {
-			if errors.As(err, new(hex.InvalidByteError)) {
+			if _, ok := errors.AsType[hex.InvalidByteError](err); ok {
 				errno = ErrBadValHexByte
 				break
 			}

internal/env/env.go

@@ -1,21 +1,29 @@
-// Package env provides the [Paths] struct for efficiently building paths from the environment.
+// Package env provides the [Paths] struct for efficiently building paths from
+// the environment.
 package env
 
 import (
+	"errors"
+	"io/fs"
 	"log"
 	"os"
 	"strconv"
 
 	"hakurei.app/check"
+	"hakurei.app/fhs"
 	"hakurei.app/hst"
 )
 
+const VarRunNscd = fhs.Var + "run/nscd"
+
 // Paths holds paths copied from the environment and is used to create [hst.Paths].
 type Paths struct {
 	// TempDir is returned by [os.TempDir].
 	TempDir *check.Absolute
 	// RuntimePath is copied from $XDG_RUNTIME_DIR.
 	RuntimePath *check.Absolute
+	// Whether [VarRunNscd] is a directory.
+	HasNscd bool
 }
 
 // Copy expands [Paths] into [hst.Paths].
@@ -37,14 +45,17 @@ func (env *Paths) Copy(v *hst.Paths, userid int) {
 }
 
 // CopyPaths returns a populated [Paths].
-func CopyPaths() *Paths { return CopyPathsFunc(log.Fatalf, os.TempDir, os.Getenv) }
+func CopyPaths() *Paths {
+	return CopyPathsFunc(log.Fatalf, os.TempDir, os.Getenv, os.Stat)
+}
 
-// CopyPathsFunc returns a populated [Paths],
-// using the provided [log.Fatalf], [os.TempDir], [os.Getenv] functions.
+// CopyPathsFunc returns a populated [Paths], using the provided [log.Fatalf],
+// [os.TempDir], [os.Getenv] functions.
 func CopyPathsFunc(
 	fatalf func(format string, v ...any),
 	tempdir func() string,
 	getenv func(key string) string,
+	stat func(name string) (fs.FileInfo, error),
 ) *Paths {
 	const xdgRuntimeDir = "XDG_RUNTIME_DIR"
 
@@ -61,5 +72,14 @@ func CopyPathsFunc(
 		env.RuntimePath = a
 	}
 
+	if fi, err := stat(VarRunNscd); err != nil {
+		if !errors.Is(err, fs.ErrNotExist) {
+			fatalf("%v", err)
+			panic("unreachable")
+		}
+	} else {
+		env.HasNscd = fi.IsDir()
+	}
+
 	return &env
 }

internal/env/env_test.go

@@ -2,6 +2,7 @@ package env_test
 
 import (
 	"fmt"
+	"io/fs"
 	"reflect"
 	"testing"
 
@@ -104,7 +105,9 @@ func TestCopyPaths(t *testing.T) {
 					t.Fatalf("fatalf: %q, want %q", got, tc.fatal)
 				}
 				panic(stub.PanicExit)
-			}, func() string { return tc.tmp }, func(key string) string { return tc.env[key] })
+			}, func() string { return tc.tmp }, func(key string) string { return tc.env[key] }, func(name string) (fs.FileInfo, error) {
+				return nil, fs.ErrNotExist
+			})
 
 			if tc.fatal != "" {
 				t.Fatalf("copyPaths: expected fatal %q", tc.fatal)

internal/kobject/kobject.go

@@ -101,7 +101,7 @@ func (o *Object) update(env map[string]string, strip bool) {
 // A pendingIterator is a callback currently iterating through objects targeted
 // by ongoing events.
 type pendingIterator struct {
-	f    func(o *Object) bool
+	f    func(o *Object, act uevent.KobjectAction) bool
 	done chan<- struct{}
 }
 
@@ -150,12 +150,12 @@ func (s *State) deleteIter(p *pendingIterator) {
 }
 
 // dispatchIter broadcasts an [Object] to all alive iterators.
-func (s *State) dispatchIter(o *Object) {
+func (s *State) dispatchIter(o *Object, act uevent.KobjectAction) {
 	s.iterMu.Lock()
 	defer s.iterMu.Unlock()
 
 	for _, p := range s.iter {
-		if !p.f(o) {
+		if !p.f(o, act) {
 			s.deleteIter(p)
 			close(p.done)
 		}
@@ -165,14 +165,17 @@ func (s *State) dispatchIter(o *Object) {
 // Range calls f on all current and upcoming [Object] values tracked by s until
 // f returns false or the context is cancelled. f must not retain o or modify
 // the value it points to.
-func (s *State) Range(ctx context.Context, f func(o *Object) bool) {
+func (s *State) Range(
+	ctx context.Context,
+	f func(o *Object, act uevent.KobjectAction) bool,
+) {
 	done := make(chan struct{})
 	p := pendingIterator{f, done}
 
 	s.iterMu.Lock()
 	s.ueventMu.RLock()
 	for _, o := range s.uevent {
-		if !f(o) {
+		if !f(o, uevent.KOBJ_ADD) {
 			s.ueventMu.RUnlock()
 			s.iterMu.Unlock()
 			return
@@ -296,13 +299,13 @@ func (s *State) processEvent(e *Event) {
 		return
 	}
 
-	switch e.Action {
+	switch act := e.Action; act {
 	case uevent.KOBJ_ADD:
 		if e.Synth == nil {
 			if o, ok := s.uevent[e.DevPath]; ok {
 				s.reportErr(e.NewError(EDuplicateAdd, o))
 				o.merge(e.Env)
-				s.dispatchIter(o)
+				s.dispatchIter(o, act)
 				return
 			}
 		}
@@ -312,7 +315,7 @@ func (s *State) processEvent(e *Event) {
 		}
 		o.merge(e.Env)
 		s.uevent[e.DevPath] = o
-		s.dispatchIter(o)
+		s.dispatchIter(o, act)
 		return
 
 	case uevent.KOBJ_REMOVE:
@@ -338,14 +341,14 @@ func (s *State) processEvent(e *Event) {
 			o = e.makeColdboot()
 			o.merge(e.Env)
 			s.uevent[e.DevPath] = o
-			s.dispatchIter(o)
+			s.dispatchIter(o, act)
 			return
 		}
 		o.update(e.Env, true)
 		if s.handleChange != nil {
 			s.handleChange(o, e.Env)
 		}
-		s.dispatchIter(o)
+		s.dispatchIter(o, act)
 		return
 
 	case uevent.KOBJ_MOVE:
@@ -368,7 +371,7 @@ func (s *State) processEvent(e *Event) {
 		o.merge(e.Env)
 		s.uevent[e.DevPath] = o
 		o.DevPath = e.DevPath
-		s.dispatchIter(o)
+		s.dispatchIter(o, act)
 		return
 
 	case uevent.KOBJ_ONLINE:
@@ -384,7 +387,7 @@ func (s *State) processEvent(e *Event) {
 			s.reportErr(e.NewError(EUnexpectedOffline, o))
 		}
 		o.Offline = false
-		s.dispatchIter(o)
+		s.dispatchIter(o, act)
 		return
 
 	case uevent.KOBJ_OFFLINE:
@@ -400,7 +403,7 @@ func (s *State) processEvent(e *Event) {
 			s.reportErr(e.NewError(EUnexpectedOffline, o))
 		}
 		o.Offline = true
-		s.dispatchIter(o)
+		s.dispatchIter(o, act)
 		return
 
 	case uevent.KOBJ_BIND:
@@ -416,7 +419,7 @@ func (s *State) processEvent(e *Event) {
 		}
 		o.State = StateBound
 		o.merge(e.Env)
-		s.dispatchIter(o)
+		s.dispatchIter(o, act)
 		return
 
 	case uevent.KOBJ_UNBIND:
@@ -432,7 +435,7 @@ func (s *State) processEvent(e *Event) {
 		}
 		o.State = StateNew
 		o.Driver = ""
-		s.dispatchIter(o)
+		s.dispatchIter(o, act)
 		return
 
 	default: // not reached

internal/kobject/kobject_test.go

@@ -388,7 +388,9 @@ func TestIter(t *testing.T) {
 			"SEQNUM=1",
 		}}
 		synctest.Wait()
-		s.Range(t.Context(), func(o *Object) bool { return false })
+		s.Range(t.Context(), func(*Object, uevent.KobjectAction) bool {
+			return false
+		})
 
 		var got []*Object
 		check := func(want []*Object) {
@@ -405,7 +407,7 @@ func TestIter(t *testing.T) {
 		defer cancel()
 		var done bool
 		wg.Go(func() {
-			s.Range(ctx, func(o *Object) bool {
+			s.Range(ctx, func(o *Object, _ uevent.KobjectAction) bool {
 				got = append(got, o.Clone())
 				return !done
 			})
@@ -437,7 +439,11 @@ func TestIter(t *testing.T) {
 			},
 		})
 
-		wg.Go(func() { s.Range(ctx, func(*Object) bool { return true }) })
+		wg.Go(func() {
+			s.Range(ctx, func(*Object, uevent.KobjectAction) bool {
+				return true
+			})
+		})
 		synctest.Wait()
 
 		iter := reflect.ValueOf(s).Elem().FieldByName("iter")

internal/lockedfile/transform_test.go

@@ -40,7 +40,7 @@ func TestTransform(t *testing.T) {
 
 	const maxChunkWords = 8 << 10
 	buf := make([]byte, 2*maxChunkWords*8)
-	for i := uint64(0); i < 2*maxChunkWords; i++ {
+	for i := range uint64(2 * maxChunkWords) {
 		binary.LittleEndian.PutUint64(buf[i*8:], i)
 	}
 	if err := lockedfile.Write(path, bytes.NewReader(buf[:8]), 0666); err != nil {

internal/outcome/dispatcher_test.go

@@ -23,6 +23,7 @@ import (
 	"hakurei.app/container/seccomp"
 	"hakurei.app/container/std"
 	"hakurei.app/hst"
+	"hakurei.app/internal/env"
 	"hakurei.app/internal/stub"
 	"hakurei.app/internal/system"
 	"hakurei.app/message"
@@ -174,6 +175,7 @@ func checkOpBehaviour(t *testing.T, testCases []opBehaviourTestCase) {
 		call("cmdOutput", stub.ExpectArgs{container.Nonexistent, os.Stderr, []string{}, "/"}, []byte("0"), nil),
 		call("tempdir", stub.ExpectArgs{}, container.Nonexistent+"/tmp", nil),
 		call("lookupEnv", stub.ExpectArgs{"XDG_RUNTIME_DIR"}, wantRuntimePath, nil),
+		call("stat", stub.ExpectArgs{env.VarRunNscd}, stubFileInfoIsDir(true), nil),
 		call("getuid", stub.ExpectArgs{}, 1000, nil),
 		call("getgid", stub.ExpectArgs{}, 100, nil),
 

internal/outcome/finalise.go

@@ -58,8 +58,7 @@ func (k *outcome) finalise(
 	supp := make([]string, len(config.Groups))
 	for i, name := range config.Groups {
 		if gid, err := k.lookupGroupId(name); err != nil {
-			var unknownGroupError user.UnknownGroupError
-			if errors.As(err, &unknownGroupError) {
+			if unknownGroupError, ok := errors.AsType[user.UnknownGroupError](err); ok {
 				return newWithMessageError(fmt.Sprintf("unknown group %q", name), unknownGroupError)
 			} else {
 				return &hst.AppError{Step: "look up group by name", Err: err, Msg: err.Error()}

internal/outcome/hsu.go

@@ -51,18 +51,16 @@ func (h *Hsu) ID() (int, error) {
 		cmd.Stderr = os.Stderr // pass through fatal messages
 		cmd.Env = make([]string, 0)
 		cmd.Dir = fhs.Root
-		var (
-			p         []byte
-			exitError *exec.ExitError
-		)
-
+		var p []byte
 		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 {
+		} else if exitError, ok := errors.AsType[*exec.ExitError](h.idErr); ok &&
+			exitError != nil &&
+			exitError.ExitCode() == 1 {
 			// hsu prints an error message in this case
 			h.idErr = &hst.AppError{Step: step, Err: ErrHsuAccess}
 		} else if errors.Is(h.idErr, os.ErrNotExist) {

internal/outcome/outcome.go

@@ -110,7 +110,7 @@ func newOutcomeState(k syscallDispatcher, msg message.Msg, id *hst.ID, config *h
 		Paths: env.CopyPathsFunc(k.fatalf, k.tempdir, func(key string) string {
 			v, _ := k.lookupEnv(key)
 			return v
-		}),
+		}, k.stat),
 		Container: config.Container,
 	}
 

internal/outcome/process.go

@@ -328,11 +328,11 @@ func (k *outcome) main(msg message.Msg, identifierFd int) {
 				}
 
 				if err := k.sys.Revert((*system.Criteria)(&ec)); err != nil {
-					var joinError interface {
+					joinError, ok := errors.AsType[interface {
 						Unwrap() []error
 						error
-					}
-					if !errors.As(err, &joinError) || joinError == nil {
+					}](err)
+					if !ok || joinError == nil {
 						perror(err, "revert system setup")
 					} else {
 						for _, v := range joinError.Unwrap() {

internal/outcome/run_test.go

@@ -136,16 +136,13 @@ func TestOutcomeRun(t *testing.T) {
 				Tmpfs(fhs.AbsDevShm, 0, 01777).
 
 				// spRuntimeOp
+				Tmpfs(fhs.AbsRun, xdgRuntimeDirSize, 0755).
 				Tmpfs(fhs.AbsRunUser, xdgRuntimeDirSize, 0755).
 				Bind(m("/tmp/hakurei.0/runtime/9"), m("/run/user/1971"), std.BindWritable).
 
 				// spTmpdirOp
 				Bind(m("/tmp/hakurei.0/tmpdir/9"), fhs.AbsTmp, std.BindWritable).
 
-				// spAccountOp
-				Place(m("/etc/passwd"), []byte("chronos:x:1971:100:Hakurei:/data/data/org.chromium.Chromium:/run/current-system/sw/bin/zsh\n")).
-				Place(m("/etc/group"), []byte("hakurei:x:100:\n")).
-
 				// spWaylandOp
 				Bind(m("/tmp/hakurei.0/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/wayland"), m("/run/user/1971/wayland-0"), 0).
 
@@ -452,7 +449,7 @@ func TestOutcomeRun(t *testing.T) {
 
 				Path: m("/nix/store/yqivzpzzn7z5x0lq9hmbzygh45d8rhqd-chromium-start"),
 
-				Flags: hst.FUserns | hst.FHostNet | hst.FMapRealUID | hst.FShareRuntime | hst.FShareTmpdir,
+				Flags: hst.FUserns | hst.FHostNet | hst.FMapRealUID | hst.FNoPlace | hst.FShareRuntime | hst.FShareTmpdir,
 			},
 			SystemBus: &hst.BusConfig{
 				Talk:   []string{"org.bluez", "org.freedesktop.Avahi", "org.freedesktop.UPower"},
@@ -547,8 +544,6 @@ func TestOutcomeRun(t *testing.T) {
 				Tmpfs(m("/run/user/"), xdgRuntimeDirSize, 0755).
 				Bind(m("/tmp/hakurei.0/runtime/1"), m("/run/user/1971"), std.BindWritable).
 				Bind(m("/tmp/hakurei.0/tmpdir/1"), m("/tmp/"), std.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("/tmp/hakurei.0/8e2c76b066dabe574cf073bdb46eb5c1/pipewire"), m("/run/user/1971/pipewire-0"), 0).
 				Bind(m("/tmp/hakurei.0/8e2c76b066dabe574cf073bdb46eb5c1/bus"), m("/run/user/1971/bus"), 0).
@@ -715,7 +710,7 @@ func (k *stubNixOS) lookupEnv(key string) (string, bool) {
 func (k *stubNixOS) stat(name string) (fs.FileInfo, error) {
 	switch name {
 	case "/var/run/nscd":
-		return nil, nil
+		return stubFileInfoIsDir(true), nil
 	case "/run/user/1971/pulse":
 		return nil, nil
 	case "/run/user/1971/pulse/native":

internal/outcome/shim.go

@@ -390,8 +390,8 @@ func shimEntrypoint(k syscallDispatcher) {
 	if err := k.containerWait(z); err != nil {
 		sp.destroy()
 
-		var exitError *exec.ExitError
-		if !errors.As(err, &exitError) {
+		exitError, ok := errors.AsType[*exec.ExitError](err)
+		if !ok {
 			if errors.Is(err, context.Canceled) {
 				k.exit(hst.ExitCancel)
 			}

internal/outcome/shim_test.go

@@ -71,16 +71,13 @@ func TestShimEntrypoint(t *testing.T) {
 			Tmpfs(fhs.AbsDevShm, 0, 01777).
 
 			// spRuntimeOp
+			Tmpfs(fhs.AbsRun, xdgRuntimeDirSize, 0755).
 			Tmpfs(fhs.AbsRunUser, xdgRuntimeDirSize, 0755).
 			Bind(m("/tmp/hakurei.10/runtime/9999"), m("/run/user/1000"), std.BindWritable).
 
 			// spTmpdirOp
 			Bind(m("/tmp/hakurei.10/tmpdir/9999"), fhs.AbsTmp, std.BindWritable).
 
-			// spAccountOp
-			Place(m("/etc/passwd"), []byte("chronos:x:1000:100:Hakurei:/data/data/org.chromium.Chromium:/run/current-system/sw/bin/zsh\n")).
-			Place(m("/etc/group"), []byte("hakurei:x:100:\n")).
-
 			// spWaylandOp
 			Bind(m("/tmp/hakurei.10/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/wayland"), m("/run/user/1000/wayland-0"), 0).
 

internal/outcome/spaccount.go

@@ -6,6 +6,7 @@ import (
 	"syscall"
 
 	"hakurei.app/fhs"
+	"hakurei.app/hst"
 	"hakurei.app/internal/validate"
 )
 
@@ -41,16 +42,18 @@ func (s spAccountOp) toContainer(state *outcomeStateParams) error {
 	state.env["USER"] = username
 	state.env["SHELL"] = state.Container.Shell.String()
 
-	state.params.
-		Place(fhs.AbsEtc.Append("passwd"),
-			[]byte(username+":x:"+
-				state.mapuid.String()+":"+
-				state.mapgid.String()+
-				":Hakurei:"+
-				state.Container.Home.String()+":"+
-				state.Container.Shell.String()+"\n")).
-		Place(fhs.AbsEtc.Append("group"),
-			[]byte("hakurei:x:"+state.mapgid.String()+":\n"))
+	if state.Container.Flags&hst.FNoPlace == 0 {
+		state.params.
+			Place(fhs.AbsEtc.Append("passwd"),
+				[]byte(username+":x:"+
+					state.mapuid.String()+":"+
+					state.mapgid.String()+
+					":Hakurei:"+
+					state.Container.Home.String()+":"+
+					state.Container.Shell.String()+"\n")).
+			Place(fhs.AbsEtc.Append("group"),
+				[]byte("hakurei:x:"+state.mapgid.String()+":\n"))
+	}
 
 	return nil
 }

internal/outcome/spaccount_test.go

@@ -38,6 +38,7 @@ func TestSpAccountOp(t *testing.T) {
 		{"success fallback username", func(bool, bool) outcomeOp { return spAccountOp{} }, func() *hst.Config {
 			c := hst.Template()
 			c.Container.Username = ""
+			c.Container.Flags = hst.FMapRealUID
 			return c
 		}, nil, []stub.Call{
 			// this op performs basic validation and does not make calls during toSystem
@@ -60,9 +61,7 @@ func TestSpAccountOp(t *testing.T) {
 			// this op configures the container state and does not make calls during toContainer
 		}, &container.Params{
 			Dir: config.Container.Home,
-			Ops: new(container.Ops).
-				Place(m("/etc/passwd"), []byte("chronos:x:1000:100:Hakurei:/data/data/org.chromium.Chromium:/run/current-system/sw/bin/zsh\n")).
-				Place(m("/etc/group"), []byte("hakurei:x:100:\n")),
+			Ops: new(container.Ops),
 		}, paramsWantEnv(config, map[string]string{
 			"HOME":  config.Container.Home.String(),
 			"USER":  config.Container.Username,

internal/outcome/spcontainer.go

@@ -18,13 +18,12 @@ import (
 	"hakurei.app/hst"
 	"hakurei.app/internal/acl"
 	"hakurei.app/internal/dbus"
+	"hakurei.app/internal/env"
 	"hakurei.app/internal/system"
 	"hakurei.app/internal/validate"
 	"hakurei.app/message"
 )
 
-const varRunNscd = fhs.Var + "run/nscd"
-
 func init() { gob.Register(new(spParamsOp)) }
 
 // spParamsOp initialises unordered fields of [container.Params] and the
@@ -136,17 +135,23 @@ type spFilesystemOp struct {
 }
 
 func (s *spFilesystemOp) toSystem(state *outcomeStateSys) error {
-	/* 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 */
+	// 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
 	hidePaths := []string{
 		state.sc.RuntimePath.String(),
 		state.sc.SharePath.String(),
+	}
 
-		// this causes emulated passwd database to be bypassed on some /etc/ setups
-		varRunNscd,
+	if state.Paths == nil || state.HasNscd {
+		hidePaths = append(hidePaths,
+			// this causes emulated passwd database to be bypassed on some /etc/
+			// setups, made optional to avoid needlessly creating it on
+			// non-glibc systems when invoking permissive defaults
+			env.VarRunNscd,
+		)
 	}
 
 	// dbus.Address does not go through syscallDispatcher
@@ -382,6 +387,10 @@ func (p opsAdapter) Overlay(target, state, work *check.Absolute, layers ...*chec
 	return opsAdapter{p.Ops.Overlay(target, state, work, layers...)}
 }
 
+func (p opsAdapter) OverlayEphemeral(target *check.Absolute, layers ...*check.Absolute) hst.Ops {
+	return opsAdapter{p.Ops.OverlayEphemeral(target, layers...)}
+}
+
 func (p opsAdapter) OverlayReadonly(target *check.Absolute, layers ...*check.Absolute) hst.Ops {
 	return opsAdapter{p.Ops.OverlayReadonly(target, layers...)}
 }

internal/outcome/spruntime.go

@@ -113,6 +113,9 @@ func (s *spRuntimeOp) toContainer(state *outcomeStateParams) error {
 
 	}
 
+	if state.Container.Flags&hst.FCoverRun != 0 {
+		state.params.Tmpfs(fhs.AbsRun, xdgRuntimeDirSize, 0755)
+	}
 	state.params.Tmpfs(fhs.AbsRunUser, xdgRuntimeDirSize, 0755)
 	if state.Container.Flags&hst.FShareRuntime != 0 {
 		_, runtimeDirInst := s.commonPaths(state.outcomeState)

internal/outcome/spruntime_test.go

@@ -40,6 +40,7 @@ func TestSpRuntimeOp(t *testing.T) {
 			// this op configures the container state and does not make calls during toContainer
 		}, &container.Params{
 			Ops: new(container.Ops).
+				Tmpfs(fhs.AbsRun, xdgRuntimeDirSize, 0755).
 				Tmpfs(fhs.AbsRunUser, xdgRuntimeDirSize, 0755).
 				Bind(m("/proc/nonexistent/tmp/hakurei.0/runtime/9"), m("/run/user/1000"), std.BindWritable),
 		}, paramsWantEnv(config, map[string]string{
@@ -67,6 +68,7 @@ func TestSpRuntimeOp(t *testing.T) {
 			// this op configures the container state and does not make calls during toContainer
 		}, &container.Params{
 			Ops: new(container.Ops).
+				Tmpfs(fhs.AbsRun, xdgRuntimeDirSize, 0755).
 				Tmpfs(fhs.AbsRunUser, xdgRuntimeDirSize, 0755).
 				Bind(m("/proc/nonexistent/tmp/hakurei.0/runtime/9"), m("/run/user/1000"), std.BindWritable),
 		}, paramsWantEnv(config, map[string]string{
@@ -94,6 +96,7 @@ func TestSpRuntimeOp(t *testing.T) {
 			// this op configures the container state and does not make calls during toContainer
 		}, &container.Params{
 			Ops: new(container.Ops).
+				Tmpfs(fhs.AbsRun, xdgRuntimeDirSize, 0755).
 				Tmpfs(fhs.AbsRunUser, xdgRuntimeDirSize, 0755).
 				Bind(m("/proc/nonexistent/tmp/hakurei.0/runtime/9"), m("/run/user/1000"), std.BindWritable),
 		}, paramsWantEnv(config, map[string]string{
@@ -117,6 +120,7 @@ func TestSpRuntimeOp(t *testing.T) {
 			// this op configures the container state and does not make calls during toContainer
 		}, &container.Params{
 			Ops: new(container.Ops).
+				Tmpfs(fhs.AbsRun, xdgRuntimeDirSize, 0755).
 				Tmpfs(fhs.AbsRunUser, xdgRuntimeDirSize, 0755).
 				Bind(m("/proc/nonexistent/tmp/hakurei.0/runtime/9"), m("/run/user/1000"), std.BindWritable),
 		}, paramsWantEnv(config, map[string]string{

internal/pipewire/pod.go

@@ -176,8 +176,8 @@ func marshalValueAppendRaw(data []byte, v reflect.Value) ([]byte, error) {
 	case reflect.Struct:
 		data = SPA_TYPE_Struct.append(data)
 		var err error
-		for i := 0; i < v.NumField(); i++ {
-			data, err = marshalValueAppend(data, v.Field(i))
+		for _, field := range v.Fields() {
+			data, err = marshalValueAppend(data, field)
 			if err != nil {
 				return data, err
 			}
@@ -370,8 +370,8 @@ func unmarshalValue(data []byte, v reflect.Value, wireSizeP *Word) error {
 		}
 
 		var fieldWireSize Word
-		for i := 0; i < v.NumField(); i++ {
-			if err := unmarshalValue(data, v.Field(i), &fieldWireSize); err != nil {
+		for _, field := range v.Fields() {
+			if err := unmarshalValue(data, field, &fieldWireSize); err != nil {
 				return err
 			}
 			// bounds check completed in successful call to unmarshalValue

internal/pkg/archive.go

@@ -0,0 +1,411 @@
+package pkg
+
+import (
+	"crypto/sha512"
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"io"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"unsafe"
+
+	"hakurei.app/check"
+)
+
+/*
+| mode uint32 | path_sz uint32 |
+|        data_sz uint64        |
+|         path string          |
+|         data []byte          |
+*/
+
+// An ArchiveHeader represents a single header in an archive.
+type ArchiveHeader struct {
+	Mode fs.FileMode // file mode bits
+	Path string      // pathname of the file
+	Size uint64      // size of data segment
+}
+
+// Writer implements sequential writing of an archive. [Writer.WriteHeader]
+// begins a new file with the provided [ArchiveHeader], and then Writer can be
+// treated as an [io.Writer] to supply that file's data.
+//
+// It is the caller's responsibility to write entries in lexical order.
+type Writer struct {
+	// Underlying writer.
+	w io.Writer
+	// Current header.
+	h ArchiveHeader
+	// Fixed-size header segment.
+	buf [wordSize * 2]byte
+	// Current position in data segment.
+	n uint64
+}
+
+// NewWriter returns the address of a new [Writer] writing to w.
+func NewWriter(w io.Writer) *Writer { return &Writer{w: w} }
+
+var zero [wordSize]byte
+
+// padSize returns the padding size for aligning sz.
+func padSize[T int | uint64](sz T) T {
+	return (wordSize - (sz)%wordSize) % wordSize
+}
+
+// flush concludes writing to the current file and writes padding.
+func (aw *Writer) flush() error {
+	if aw.h.Size > aw.n {
+		return fmt.Errorf("missed writing %d bytes", aw.h.Size-aw.n)
+	} else if aw.h.Size < aw.n {
+		return fmt.Errorf("wrote %d bytes beyond end of file", aw.n-aw.h.Size)
+	}
+
+	if psz := padSize(aw.h.Size); psz != 0 {
+		if _, err := aw.w.Write(zero[:psz]); err != nil {
+			return err
+		}
+	}
+
+	aw.n = 0
+	return nil
+}
+
+// WriteHeader writes h and begins accepting its corresponding file.
+func (aw *Writer) WriteHeader(h *ArchiveHeader) error {
+	if err := aw.flush(); err != nil {
+		return err
+	}
+
+	aw.h = *h
+	binary.LittleEndian.PutUint32(aw.buf[:], uint32(aw.h.Mode))
+	binary.LittleEndian.PutUint32(aw.buf[wordSize/2:], uint32(len(aw.h.Path)))
+	binary.LittleEndian.PutUint64(aw.buf[wordSize:], aw.h.Size)
+	if _, err := aw.w.Write(aw.buf[:]); err != nil {
+		return err
+	} else if _, err = aw.w.Write(
+		unsafe.Slice(unsafe.StringData(aw.h.Path), len(aw.h.Path)),
+	); err != nil {
+		return err
+	} else if psz := padSize(len(aw.h.Path)); psz != 0 {
+		if _, err = aw.w.Write(zero[:psz]); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Write writes p to the underlying writer and records the new position. Invalid
+// positions are reported by WriteHeader and Close.
+func (aw *Writer) Write(p []byte) (n int, err error) {
+	n, err = aw.w.Write(p)
+	aw.n += uint64(n)
+	return
+}
+
+// Close concludes writing to the archive stream.
+func (aw *Writer) Close() (err error) {
+	err = aw.flush()
+	aw.w = nil
+	return
+}
+
+// ErrInsecurePath is returned by [FlatEntry.Decode] if validation is requested
+// and a nonlocal path is encountered in the stream.
+var ErrInsecurePath = errors.New("insecure file path")
+
+// Reader implements sequential reading of an archive. [Reader.Next] advances to
+// the next file in the archive (including the first), and then Reader can be
+// treated as an [io.Reader] to access the file's data.
+type Reader struct {
+	// Underlying reader.
+	r io.Reader
+	// Fixed-size header segment.
+	buf [wordSize * 2]byte
+	// Remaining bytes in current data segment.
+	n, pad uint64
+}
+
+// NewReader returns the address of a new [Reader] reading from r.
+func NewReader(r io.Reader) *Reader { return &Reader{r: r} }
+
+// Next advances ar to the next entry. Remaining bytes of the current data
+// segment are discarded. Advancing beyond the final entry returns [io.EOF].
+func (ar *Reader) Next() (*ArchiveHeader, error) {
+	if dsz := int64(ar.n + ar.pad); dsz > 0 {
+		if n, err := io.CopyN(io.Discard, ar.r, dsz); err != nil {
+			if errors.Is(err, io.EOF) && n != dsz {
+				err = io.ErrUnexpectedEOF
+			}
+			return nil, err
+		}
+	}
+
+	if _, err := io.ReadFull(ar.r, ar.buf[:]); err != nil {
+		return nil, err
+	}
+
+	h := ArchiveHeader{
+		Mode: fs.FileMode(binary.LittleEndian.Uint32(ar.buf[:])),
+		Size: binary.LittleEndian.Uint64(ar.buf[wordSize:]),
+	}
+	pathSize := int(binary.LittleEndian.Uint32(ar.buf[wordSize/2:]))
+	pPathSize := alignSize(pathSize)
+
+	buf := make([]byte, pPathSize)
+	if _, err := io.ReadFull(ar.r, buf); err != nil {
+		if errors.Is(err, io.EOF) {
+			err = io.ErrUnexpectedEOF
+		}
+		return nil, err
+	}
+
+	h.Path = unsafe.String(unsafe.SliceData(buf), pathSize)
+	if !filepath.IsLocal(h.Path) {
+		return &h, ErrInsecurePath
+	}
+
+	ar.n = h.Size
+	ar.pad = padSize(h.Size)
+	return &h, nil
+}
+
+// Read implements [io.Reader] for the data segment of the current entry.
+func (ar *Reader) Read(p []byte) (n int, err error) {
+	if uint64(len(p)) > ar.n {
+		p = p[:ar.n]
+	}
+
+	if len(p) > 0 {
+		n, err = ar.r.Read(p)
+		ar.n -= uint64(n)
+	}
+
+	switch err {
+	case io.EOF:
+		if ar.n > 0 {
+			return n, io.ErrUnexpectedEOF
+		}
+
+	case nil:
+		if ar.n == 0 {
+			return n, io.EOF
+		}
+	}
+	return
+}
+
+// Write writes a deterministic representation of the contents of fsys to w.
+// The resulting data can be hashed to produce a deterministic checksum for the
+// directory.
+func Write(fsys fs.FS, root string, w io.Writer) error {
+	aw := NewWriter(w)
+	if err := fs.WalkDir(fsys, root, func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+
+		var fi fs.FileInfo
+		fi, err = d.Info()
+		if err != nil {
+			return err
+		}
+
+		h := ArchiveHeader{
+			Path: path,
+			Mode: fi.Mode(),
+		}
+		if h.Mode.IsRegular() {
+			h.Size = uint64(fi.Size())
+			if err = aw.WriteHeader(&h); err != nil {
+				return err
+			}
+
+			var r fs.File
+			r, err = fsys.Open(path)
+			if err != nil {
+				return err
+			}
+			_, err = io.Copy(aw, r)
+			if _err := r.Close(); err == nil {
+				err = _err
+			}
+			return err
+		} else if h.Mode&fs.ModeSymlink != 0 {
+			var newpath string
+			if newpath, err = fs.ReadLink(fsys, path); err != nil {
+				return err
+			}
+
+			h.Size = uint64(len(newpath))
+			if err = aw.WriteHeader(&h); err != nil {
+				return err
+			}
+
+			_, err = aw.Write(unsafe.Slice(unsafe.StringData(newpath), len(newpath)))
+			return err
+		} else if !h.Mode.IsDir() {
+			return InvalidFileModeError(h.Mode)
+		}
+		return aw.WriteHeader(&h)
+	}); err != nil {
+		return err
+	}
+	return aw.Close()
+}
+
+// SumFS saves checksum of the archive of fsys to the value pointed to by buf.
+func SumFS(buf *Checksum, fsys fs.FS, root string) error {
+	h := sha512.New384()
+	if err := Write(fsys, root, h); err != nil {
+		return err
+	}
+	h.Sum(buf[:0])
+	return nil
+}
+
+// SumDir saves checksum of the archive of directory at pathname to the value
+// pointed to by buf.
+func SumDir(buf *Checksum, pathname *check.Absolute) error {
+	return SumFS(buf, os.DirFS(pathname.String()), ".")
+}
+
+// archiveArtifact is an [Artifact] unpacking an archive supported by [Reader]
+// backed by a [FileArtifact].
+type archiveArtifact struct {
+	// Caller-supplied backing archive.
+	f Artifact
+}
+
+var _ CuresExempt = archiveArtifact{}
+
+// NewArchive returns a new [Artifact] backed by the supplied [Artifact]. The
+// source [Artifact] must be a [FileArtifact] and produce a stream compatible
+// with [Reader].
+func NewArchive(a Artifact) Artifact {
+	return archiveArtifact{a}
+}
+
+// Kind returns the hardcoded [Kind] constant.
+func (archiveArtifact) Kind() Kind { return KindArchive }
+
+// Params is a noop.
+func (archiveArtifact) Params(*IContext) {}
+
+func init() {
+	register(KindArchive, func(r *IRReader) Artifact {
+		a := NewArchive(r.Next())
+		if _, ok := r.Finalise(); ok {
+			panic(ErrUnexpectedChecksum)
+		}
+		return a
+	})
+}
+
+// Inputs returns a slice containing the backing file.
+func (a archiveArtifact) Inputs() []Artifact {
+	return []Artifact{a.f}
+}
+
+// IsExclusive returns false: [Reader] is fully sequential.
+func (archiveArtifact) IsExclusive() bool { return false }
+
+// Cure cures the [Artifact], producing a directory located at work.
+func (a archiveArtifact) Cure(t *TContext) (err error) {
+	var r io.ReadCloser
+	if r, err = t.Open(a.f); err != nil {
+		return
+	}
+
+	defer func() {
+		closeErr := r.Close()
+		if err == nil {
+			err = closeErr
+		}
+	}()
+
+	type dirTargetPerm struct {
+		path string
+		mode fs.FileMode
+	}
+	var madeDirectories []dirTargetPerm
+
+	if err = os.MkdirAll(t.GetWorkDir().String(), 0700); err != nil {
+		return
+	}
+	var root *os.Root
+	if root, err = os.OpenRoot(t.GetWorkDir().String()); err != nil {
+		return
+	}
+	defer func() {
+		closeErr := root.Close()
+		if err == nil {
+			err = closeErr
+		}
+	}()
+
+	var header *ArchiveHeader
+	ar := NewReader(r)
+	for header, err = ar.Next(); err == nil; header, err = ar.Next() {
+		if header.Mode.IsRegular() {
+			var f *os.File
+			if f, err = root.OpenFile(
+				header.Path,
+				os.O_CREATE|os.O_EXCL|os.O_WRONLY,
+				header.Mode.Perm(),
+			); err != nil {
+				return
+			}
+			if _, err = io.Copy(f, ar); err != nil {
+				_ = f.Close()
+				return
+			} else if err = f.Close(); err != nil {
+				return
+			}
+		} else if header.Mode&fs.ModeSymlink != 0 {
+			var p []byte
+			if p, err = io.ReadAll(ar); err != nil {
+				return
+			}
+
+			if err = root.Symlink(
+				unsafe.String(unsafe.SliceData(p), len(p)),
+				header.Path,
+			); err != nil {
+				return
+			}
+		} else if header.Mode.IsDir() {
+			if header.Path == "." {
+				continue
+			}
+
+			madeDirectories = append(madeDirectories, dirTargetPerm{
+				path: header.Path,
+				mode: header.Mode,
+			})
+			if err = root.Mkdir(header.Path, 0700); err != nil {
+				return
+			}
+		} else {
+			return InvalidFileModeError(header.Mode)
+		}
+	}
+	if errors.Is(err, io.EOF) {
+		err = nil
+	}
+	if err == nil {
+		for _, e := range madeDirectories {
+			if err = root.Chmod(e.path, e.mode.Perm()); err != nil {
+				return
+			}
+		}
+	} else {
+		return
+	}
+	return
+}
+
+// CuresExempt exempts the cheap [KindArchive] implementation often found at
+// the end of a [FileArtifact] pipeline.
+func (archiveArtifact) CuresExempt() {}

internal/pkg/archive_test.go

@@ -0,0 +1,240 @@
+package pkg_test
+
+import (
+	"bytes"
+	"io"
+	"io/fs"
+	"maps"
+	"reflect"
+	"testing"
+	"testing/fstest"
+	"unsafe"
+
+	"hakurei.app/check"
+	"hakurei.app/internal/pkg"
+)
+
+func TestArchive(t *testing.T) {
+	t.Parallel()
+
+	type entry struct {
+		path string
+		mode fs.FileMode
+		data string
+	}
+	testCases := []struct {
+		name    string
+		fsys    fs.FS
+		entries []entry
+		sum     pkg.Checksum
+		err     error
+	}{
+		{"bad type", fstest.MapFS{
+			".":       {Mode: fs.ModeDir | 0700},
+			"invalid": {Mode: fs.ModeCharDevice | 0400},
+		}, nil, pkg.Checksum{}, pkg.InvalidFileModeError(
+			fs.ModeCharDevice | 0400,
+		)},
+
+		{"coldboot", fstest.MapFS{
+			".": {Mode: fs.ModeDir | 0700},
+
+			"devices":        {Mode: fs.ModeDir | 0700},
+			"devices/uevent": {Mode: 0600, Data: []byte("add")},
+			"devices/empty":  {Mode: fs.ModeDir | 0700},
+
+			"devices/sub":        {Mode: fs.ModeDir | 0700},
+			"devices/sub/uevent": {Mode: 0600, Data: []byte("add")},
+
+			"block":        {Mode: fs.ModeDir | 0700},
+			"block/uevent": {Mode: 0600},
+		}, []entry{
+			{".", fs.ModeDir | 0700, ""},
+
+			{"block", fs.ModeDir | 0700, ""},
+			{"block/uevent", 0600, ""},
+
+			{"devices", fs.ModeDir | 0700, ""},
+			{"devices/empty", fs.ModeDir | 0700, ""},
+			{"devices/sub", fs.ModeDir | 0700, ""},
+			{"devices/sub/uevent", 0600, "add"},
+			{"devices/uevent", 0600, "add"},
+		}, pkg.MustDecode("mEy_Lf5KotThm7OwMx7yTKZh5HCCyaB41pVAvI9uDMgVQFM91iosBLYsRm8bDsX8"), nil},
+
+		{"empty", fstest.MapFS{
+			".":          {Mode: fs.ModeDir | 0700},
+			"checksum":   {Mode: fs.ModeDir | 0700},
+			"identifier": {Mode: fs.ModeDir | 0700},
+			"work":       {Mode: fs.ModeDir | 0700},
+		}, []entry{
+			{".", fs.ModeDir | 0700, ""},
+			{"checksum", fs.ModeDir | 0700, ""},
+			{"identifier", fs.ModeDir | 0700, ""},
+			{"work", fs.ModeDir | 0700, ""},
+		}, pkg.MustDecode("E4vEZKhCcL2gPZ2Tt59FS3lDng-d_2SKa2i5G_RbDfwGn6EemptFaGLPUDiOa94C"), nil},
+
+		{"sample directory step garbage", fstest.MapFS{
+			".": {Mode: fs.ModeDir | 0500},
+
+			"lib":       {Mode: fs.ModeDir | 0500},
+			"lib/check": {Mode: 0400},
+
+			"lib/pkgconfig": {Mode: fs.ModeDir | 0500},
+		}, []entry{
+			{".", fs.ModeDir | 0500, ""},
+
+			{"lib", fs.ModeDir | 0500, ""},
+			{"lib/check", 0400, ""},
+
+			{"lib/pkgconfig", fs.ModeDir | 0500, ""},
+		}, pkg.MustDecode("CUx-3hSbTWPsbMfDhgalG4Ni_GmR9TnVX8F99tY_P5GtkYvczg9RrF5zO0jX9XYT"), nil},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			t.Run("roundtrip", func(t *testing.T) {
+				t.Parallel()
+
+				var buf bytes.Buffer
+				if err := pkg.Write(
+					tc.fsys,
+					".",
+					&buf,
+				); !reflect.DeepEqual(err, tc.err) {
+					t.Fatalf("Flatten: error = %v, want %v", err, tc.err)
+				} else if tc.err != nil {
+					return
+				}
+
+				r := pkg.NewReader(bytes.NewReader(buf.Bytes()))
+				var got []entry
+				for {
+					h, err := r.Next()
+					if err != nil {
+						if err == io.EOF {
+							break
+						}
+						t.Fatalf("Next: error = %v", err)
+					}
+
+					var data []byte
+					if data, err = io.ReadAll(r); err != nil {
+						t.Fatalf("Read: error = %v", err)
+					}
+
+					got = append(got, entry{
+						path: h.Path,
+						mode: h.Mode,
+						data: unsafe.String(unsafe.SliceData(data), len(data)),
+					})
+				}
+
+				if !reflect.DeepEqual(got, tc.entries) {
+					t.Fatalf("Reader: %#v, want %#v", got, tc.entries)
+				}
+			})
+
+			if tc.err != nil {
+				return
+			}
+
+			t.Run("hash", func(t *testing.T) {
+				t.Parallel()
+
+				var got pkg.Checksum
+				if err := pkg.SumFS(&got, tc.fsys, "."); err != nil {
+					t.Fatalf("SumFS: error = %v", err)
+				} else if got != tc.sum {
+					t.Fatalf("SumFS: %v", &pkg.ChecksumMismatchError{
+						Got:  got,
+						Want: tc.sum,
+					})
+				}
+			})
+		})
+	}
+}
+
+var archiveTestdata = fstest.MapFS{
+	".": {Mode: fs.ModeDir | 0700},
+
+	"devices":        {Mode: fs.ModeDir | 0700},
+	"devices/uevent": {Mode: 0600, Data: []byte("add")},
+	"devices/empty":  {Mode: fs.ModeDir | 0700},
+
+	"devices/sub":        {Mode: fs.ModeDir | 0700},
+	"devices/sub/uevent": {Mode: 0600, Data: []byte("add")},
+
+	"block":        {Mode: fs.ModeDir | 0700},
+	"block/uevent": {Mode: 0600},
+}
+
+func TestArchiveArtifact(t *testing.T) {
+	t.Parallel()
+
+	want := maps.Clone(archiveTestdata)
+	want["."].Mode = fs.ModeDir | 0500
+
+	checkWithCache(t, []cacheTestCase{
+		{"unpack", 0, nil, func(t *testing.T, base *check.Absolute, c *pkg.Cache) {
+			var buf bytes.Buffer
+			if err := pkg.Write(archiveTestdata, ".", &buf); err != nil {
+				t.Fatal(err)
+			}
+
+			cureMany(t, c, []cureStep{
+				{"sample", pkg.NewArchive(
+					pkg.NewFile("", buf.Bytes()),
+				), ignorePathname, expectsFS(want), pkg.WNew, nil},
+			})
+		}, expectsFS{
+			".": {Mode: fs.ModeDir | 0700},
+
+			"checksum": {Mode: fs.ModeDir | 0700},
+			"checksum/CBPcoVHuVUTVRCMbRl8J30RSSzm_tyfuXaZ-HlZsanY1sY50meOVmgaWDrGKbx9F":                    {Mode: fs.ModeDir | 0500},
+			"checksum/CBPcoVHuVUTVRCMbRl8J30RSSzm_tyfuXaZ-HlZsanY1sY50meOVmgaWDrGKbx9F/block":              {Mode: fs.ModeDir | 0700},
+			"checksum/CBPcoVHuVUTVRCMbRl8J30RSSzm_tyfuXaZ-HlZsanY1sY50meOVmgaWDrGKbx9F/block/uevent":       {Mode: 0600},
+			"checksum/CBPcoVHuVUTVRCMbRl8J30RSSzm_tyfuXaZ-HlZsanY1sY50meOVmgaWDrGKbx9F/devices":            {Mode: fs.ModeDir | 0700},
+			"checksum/CBPcoVHuVUTVRCMbRl8J30RSSzm_tyfuXaZ-HlZsanY1sY50meOVmgaWDrGKbx9F/devices/empty":      {Mode: fs.ModeDir | 0700},
+			"checksum/CBPcoVHuVUTVRCMbRl8J30RSSzm_tyfuXaZ-HlZsanY1sY50meOVmgaWDrGKbx9F/devices/sub":        {Mode: fs.ModeDir | 0700},
+			"checksum/CBPcoVHuVUTVRCMbRl8J30RSSzm_tyfuXaZ-HlZsanY1sY50meOVmgaWDrGKbx9F/devices/sub/uevent": {Mode: 0600, Data: []byte("add")},
+			"checksum/CBPcoVHuVUTVRCMbRl8J30RSSzm_tyfuXaZ-HlZsanY1sY50meOVmgaWDrGKbx9F/devices/uevent":     {Mode: 0600, Data: []byte("add")},
+
+			"identifier": {Mode: fs.ModeDir | 0700},
+			"identifier/-zXKfphyWM2Ko7VMVURaEMSuixNokFSe0xFbnwR2RtRtvMrcPGWalV0LIn45PXTY": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/CBPcoVHuVUTVRCMbRl8J30RSSzm_tyfuXaZ-HlZsanY1sY50meOVmgaWDrGKbx9F")},
+
+			"substitute": {Mode: fs.ModeDir | 0700},
+			"work":       {Mode: fs.ModeDir | 0700},
+		}},
+	})
+}
+
+func BenchmarkArchiveRead(b *testing.B) {
+	var buf bytes.Buffer
+	if err := pkg.Write(archiveTestdata, ".", &buf); err != nil {
+		b.Fatal(err)
+	}
+	testdata := buf.Bytes()
+
+	for b.Loop() {
+		r := pkg.NewReader(bytes.NewReader(testdata))
+		for {
+			_, err := r.Next()
+			if err != nil {
+				if err == io.EOF {
+					break
+				}
+				b.Fatal(err)
+			}
+		}
+	}
+}
+
+func BenchmarkArchiveWrite(b *testing.B) {
+	for b.Loop() {
+		if err := pkg.Write(archiveTestdata, ".", io.Discard); err != nil {
+			b.Fatal(err)
+		}
+	}
+}

internal/pkg/clean.go

@@ -0,0 +1,161 @@
+package pkg
+
+import (
+	"errors"
+	"os"
+	"unique"
+)
+
+// Clean destroys checksum backing entries without any identifier or substitute
+// entry referring to it. If at least one keep [Artifact] is specified,
+// identifier and substitute entries not kept alive by them are destroyed first.
+func (c *Cache) Clean(dry, inputs bool, keep ...Artifact) (
+	[]unique.Handle[ID],
+	[]unique.Handle[Checksum],
+	error,
+) {
+	c.identMu.Lock()
+	defer c.identMu.Unlock()
+
+	c.checksumMu.Lock()
+	defer c.checksumMu.Unlock()
+
+	dents, err := os.ReadDir(c.base.Append(dirChecksum).String())
+	if err != nil {
+		return nil, nil, err
+	}
+	checksums := make(map[unique.Handle[Checksum]]string, len(dents))
+	var buf Checksum
+	for _, dent := range dents {
+		name := dent.Name()
+		if err = Decode(&buf, name); err != nil {
+			return nil, nil, err
+		}
+		checksums[unique.Make(buf)] = name
+	}
+
+	type identPair struct {
+		id   unique.Handle[ID]
+		name string
+	}
+	dents, err = os.ReadDir(c.base.Append(dirIdentifier).String())
+	if err != nil {
+		return nil, nil, err
+	}
+
+	keepIdents := make(map[unique.Handle[ID]]struct{})
+	if inputs {
+		for _, id := range Inputs((*Collect)(&keep)) {
+			keepIdents[id] = struct{}{}
+		}
+	} else {
+		for _, a := range keep {
+			keepIdents[c.Ident(a)] = struct{}{}
+		}
+	}
+
+	idents := make([]identPair, 0, len(dents))
+	for _, dent := range dents {
+		name := dent.Name()
+		if err = Decode(&buf, name); err != nil {
+			return nil, nil, err
+		}
+		id := unique.Make(ID(buf))
+
+		if _, ok := keepIdents[id]; len(keep) == 0 || ok {
+			if err = readlinkChecksum(c.base.Append(
+				dirIdentifier,
+				name,
+			), &buf); err != nil {
+				return nil, nil, err
+			}
+			delete(checksums, unique.Make(buf))
+			continue
+		}
+
+		c.msg.Verbosef(
+			"arranging for destruction of %s%s%s...",
+			c.sgrIdent, name, c.sgrRes,
+		)
+		idents = append(idents, identPair{id, name})
+	}
+
+	destroyedIdents := make([]unique.Handle[ID], 0, len(idents))
+	for _, pair := range idents {
+		if !dry {
+			if err = os.Remove(c.base.Append(
+				dirStatus,
+				pair.name,
+			).String()); err != nil && !errors.Is(err, os.ErrNotExist) {
+				return destroyedIdents, nil, err
+			}
+
+			if err = os.Remove(c.base.Append(
+				dirIdentifier,
+				pair.name,
+			).String()); err != nil {
+				return destroyedIdents, nil, err
+			}
+		}
+		destroyedIdents = append(destroyedIdents, pair.id)
+	}
+
+	destroyedChecksums := make([]unique.Handle[Checksum], 0, len(checksums))
+	for checksum, name := range checksums {
+		if err = c.parent.Err(); err != nil {
+			return destroyedIdents, destroyedChecksums, err
+		}
+		c.msg.Verbosef(
+			"destroying checksum %s%s%s...",
+			c.sgrIdent, name, c.sgrRes,
+		)
+		if !dry {
+			if err = errors.Join(removeAll(c.base.Append(
+				dirChecksum,
+				name,
+			))); err != nil {
+				return destroyedIdents, destroyedChecksums, err
+			}
+		}
+		destroyedChecksums = append(destroyedChecksums, checksum)
+	}
+
+	dents, err = os.ReadDir(c.base.Append(dirSubstitute).String())
+	if err != nil {
+		return destroyedIdents, destroyedChecksums, err
+	}
+	for _, dent := range dents {
+		name := dent.Name()
+		if err = readlinkChecksum(c.base.Append(
+			dirSubstitute,
+			name,
+		), &buf); err != nil {
+			return destroyedIdents, destroyedChecksums, err
+		}
+		if _, ok := checksums[unique.Make(buf)]; !ok {
+			continue
+		}
+
+		c.msg.Verbosef(
+			"destroying substitute %s%s%s...",
+			c.sgrIdent, name, c.sgrRes,
+		)
+		if !dry {
+			if err = os.Remove(c.base.Append(
+				dirStatus,
+				name,
+			).String()); err != nil && !errors.Is(err, os.ErrNotExist) {
+				return destroyedIdents, nil, err
+			}
+
+			if err = os.Remove(c.base.Append(
+				dirSubstitute,
+				name,
+			).String()); err != nil {
+				return destroyedIdents, destroyedChecksums, err
+			}
+		}
+	}
+
+	return destroyedIdents, destroyedChecksums, nil
+}

internal/pkg/clean_test.go

@@ -0,0 +1,293 @@
+package pkg_test
+
+import (
+	"bytes"
+	"crypto/sha512"
+	"io/fs"
+	"log"
+	"os"
+	"slices"
+	"strings"
+	"testing"
+	"unique"
+
+	"hakurei.app/internal/pkg"
+	"hakurei.app/message"
+)
+
+// formatHandles returns a user-facing string representing h.
+func formatHandles[T pkg.ID | pkg.Checksum](handles ...unique.Handle[T]) string {
+	var buf strings.Builder
+	for _, h := range handles {
+		buf.WriteString(pkg.Encode(pkg.Checksum(h.Value())))
+		buf.WriteString(", ")
+	}
+	return strings.TrimSuffix(buf.String(), ", ")
+}
+
+func TestClean(t *testing.T) {
+	t.Parallel()
+	ic := pkg.NewIR()
+
+	testCases := []struct {
+		name   string
+		a      []pkg.Artifact
+		keep   []pkg.Artifact
+		inputs bool
+		want   expectsFS
+
+		wantIdents    []unique.Handle[pkg.ID]
+		wantChecksums []unique.Handle[pkg.Checksum]
+	}{
+		{"simple", []pkg.Artifact{
+			pkg.NewFile("file", nil),
+		}, nil, false, expectsFS{
+			".": {Mode: fs.ModeDir | 0700},
+
+			"checksum": {Mode: fs.ModeDir | 0700},
+			"checksum/OLBgp1GsljhM2TJ-sbHjaiH9txEUvgdDTAzHv2P24donTt6_529l-9Ua0vFImLlb": {Mode: 0400},
+
+			"identifier": {Mode: fs.ModeDir | 0700},
+			"identifier/h6qx7m0vsyhO6oLEJgY2rKa1c6RZuIZ4QXxZSh__NZJ9VU0MIj5bFB-KuaPcsfpE": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/OLBgp1GsljhM2TJ-sbHjaiH9txEUvgdDTAzHv2P24donTt6_529l-9Ua0vFImLlb")},
+
+			"lock":       {Mode: 0644},
+			"variant":    {Mode: 0400},
+			"status":     {Mode: fs.ModeDir | 0700},
+			"substitute": {Mode: fs.ModeDir | 0700},
+			"fault":      {Mode: fs.ModeDir | 0700},
+			"work":       {Mode: fs.ModeDir | 0700},
+		}, nil, nil},
+
+		{"keep", []pkg.Artifact{
+			pkg.NewFile("removed-file", []byte("removed file")),
+		}, []pkg.Artifact{
+			pkg.NewFile("file", []byte("\xfd")),
+		}, false, expectsFS{
+			".": {Mode: fs.ModeDir | 0700},
+
+			"checksum": {Mode: fs.ModeDir | 0700},
+			"checksum/KgZ-FjbGuU-XP2QEHInpgv-2Zn0cTH5NqFMgTU0XrSdKmSwyC-3baVs1BMCP5spk": {Mode: 0400, Data: []byte("\xfd")},
+
+			"identifier": {Mode: fs.ModeDir | 0700},
+			"identifier/tkrOYhQfTRaArk4nNYNjTmHQUmuJMVIoDeAKIQBm3I4uuMimBKXKMIY2gGZqwQg4": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/KgZ-FjbGuU-XP2QEHInpgv-2Zn0cTH5NqFMgTU0XrSdKmSwyC-3baVs1BMCP5spk")},
+
+			"lock":       {Mode: 0644},
+			"variant":    {Mode: 0400},
+			"status":     {Mode: fs.ModeDir | 0700},
+			"substitute": {Mode: fs.ModeDir | 0700},
+			"fault":      {Mode: fs.ModeDir | 0700},
+			"work":       {Mode: fs.ModeDir | 0700},
+		}, []unique.Handle[pkg.ID]{
+			ic.Ident(pkg.NewFile("removed-file", []byte("removed file"))),
+		}, []unique.Handle[pkg.Checksum]{
+			unique.Make(sha512.Sum384([]byte("removed file"))),
+		}},
+
+		{"inputs anchored substitute", []pkg.Artifact{
+			&stubArtifactF{
+				kind:   pkg.KindExec,
+				params: []byte("destroyed"),
+				deps: []pkg.Artifact{
+					pkg.NewFile("destroyed-input", []byte("destroyed")),
+				},
+				cure: func(f *pkg.FContext) error {
+					p := f.GetWorkDir()
+					if err := os.MkdirAll(p.String(), 0755); err != nil {
+						return err
+					}
+					return os.WriteFile(p.Append("result").String(), nil, 0444)
+				},
+			},
+		}, []pkg.Artifact{
+			&stubArtifactF{
+				kind:   pkg.KindExec,
+				params: []byte("kept"),
+				deps: []pkg.Artifact{
+					pkg.NewFile("kept-input", []byte("kept")),
+				},
+				cure: func(f *pkg.FContext) error {
+					p := f.GetWorkDir()
+					if err := os.MkdirAll(p.String(), 0755); err != nil {
+						return err
+					}
+					return os.WriteFile(p.Append("result").String(), nil, 0444)
+				},
+			},
+		}, true, expectsFS{
+			".": {Mode: fs.ModeDir | 0700},
+
+			"checksum": {Mode: fs.ModeDir | 0700},
+			"checksum/H-eSiCo227-xdqyNl2R-5G3eqXPtbb8XegAB70I5OQb2majeZXJoCxTq9wJy5qqv":        {Mode: 0400, Data: []byte("kept")},
+			"checksum/UjZSrgz7_B7XMd9fHU7jM33UZhWlFgX0rz7JZbCBYR28bCS7jr_CAJdcDhi52ruE":        {Mode: fs.ModeDir | 0500},
+			"checksum/UjZSrgz7_B7XMd9fHU7jM33UZhWlFgX0rz7JZbCBYR28bCS7jr_CAJdcDhi52ruE/result": {Mode: 0444},
+
+			"identifier": {Mode: fs.ModeDir | 0700},
+			"identifier/KpxTUsUfGbsX6C6HU2j9cd9He3_tt2o2m2MgH4m0zial8lmoqSWY-Gc3KrS0k-UK": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/H-eSiCo227-xdqyNl2R-5G3eqXPtbb8XegAB70I5OQb2majeZXJoCxTq9wJy5qqv")},
+			"identifier/xxQ43VMIS1WHMSEFnUdBNd6pulbtgiTorP_mtJpEsZENYhGBiDEL6Y2D8yqn0Sra": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/UjZSrgz7_B7XMd9fHU7jM33UZhWlFgX0rz7JZbCBYR28bCS7jr_CAJdcDhi52ruE")},
+
+			"lock":    {Mode: 0644},
+			"variant": {Mode: 0400},
+			"status":  {Mode: fs.ModeDir | 0700},
+
+			"substitute": {Mode: fs.ModeDir | 0700},
+			"substitute/dP-6_wIDRRouOaOF-nkBy-IaUbLdYHbOUTrptu7j_qfW01mnHSjYJ0oykUmvUd2x": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/UjZSrgz7_B7XMd9fHU7jM33UZhWlFgX0rz7JZbCBYR28bCS7jr_CAJdcDhi52ruE")},
+			"substitute/td1tf1kb3z8iUFg2k1xlHeTTEz3xR4e77WSWdv2JhjmZyY6iuvodhdT8BblDOi0E": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/UjZSrgz7_B7XMd9fHU7jM33UZhWlFgX0rz7JZbCBYR28bCS7jr_CAJdcDhi52ruE")},
+
+			"fault": {Mode: fs.ModeDir | 0700},
+			"work":  {Mode: fs.ModeDir | 0700},
+		}, []unique.Handle[pkg.ID]{
+			ic.Ident(pkg.NewFile("destroyed-input", []byte("destroyed"))),
+			ic.Ident(&stubArtifactF{
+				kind:   pkg.KindExec,
+				params: []byte("destroyed"),
+				deps: []pkg.Artifact{
+					pkg.NewFile("destroyed-input", []byte("destroyed")),
+				},
+			}),
+		}, []unique.Handle[pkg.Checksum]{
+			unique.Make(sha512.Sum384([]byte("destroyed"))),
+		}},
+
+		{"inputs", []pkg.Artifact{
+			&stubArtifactF{
+				kind:   pkg.KindExec,
+				params: []byte("destroyed"),
+				deps: []pkg.Artifact{
+					pkg.NewFile("destroyed-input", []byte("destroyed")),
+				},
+				cure: func(f *pkg.FContext) error {
+					if w, err := f.GetStatusWriter(); err != nil {
+						return err
+					} else if _, err = w.Write([]byte("destroyed")); err != nil {
+						return err
+					}
+
+					p := f.GetWorkDir()
+					if err := os.MkdirAll(p.String(), 0755); err != nil {
+						return err
+					}
+					return os.WriteFile(p.Append("result").String(), nil, 0444)
+				},
+			},
+		}, []pkg.Artifact{
+			&stubArtifactF{
+				kind:   pkg.KindExec,
+				params: []byte("kept"),
+				deps: []pkg.Artifact{
+					pkg.NewFile("kept-input", []byte("kept")),
+				},
+				cure: func(f *pkg.FContext) error {
+					if w, err := f.GetStatusWriter(); err != nil {
+						return err
+					} else if _, err = w.Write([]byte("kept")); err != nil {
+						return err
+					}
+
+					p := f.GetWorkDir()
+					if err := os.MkdirAll(p.String(), 0755); err != nil {
+						return err
+					}
+					return os.WriteFile(p.Append("result").String(), []byte{0}, 0444)
+				},
+			},
+		}, true, expectsFS{
+			".": {Mode: fs.ModeDir | 0700},
+
+			"checksum": {Mode: fs.ModeDir | 0700},
+			"checksum/CyDnDvF-LaeGPcSW70tPosNCoclByWkTjznUUF1DcgzlIwkN9yzz1ZFME1TlPj6W":        {Mode: fs.ModeDir | 0500},
+			"checksum/CyDnDvF-LaeGPcSW70tPosNCoclByWkTjznUUF1DcgzlIwkN9yzz1ZFME1TlPj6W/result": {Mode: 0444, Data: []byte("\x00")},
+			"checksum/H-eSiCo227-xdqyNl2R-5G3eqXPtbb8XegAB70I5OQb2majeZXJoCxTq9wJy5qqv":        {Mode: 0400, Data: []byte("kept")},
+
+			"identifier": {Mode: fs.ModeDir | 0700},
+			"identifier/KpxTUsUfGbsX6C6HU2j9cd9He3_tt2o2m2MgH4m0zial8lmoqSWY-Gc3KrS0k-UK": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/H-eSiCo227-xdqyNl2R-5G3eqXPtbb8XegAB70I5OQb2majeZXJoCxTq9wJy5qqv")},
+			"identifier/xxQ43VMIS1WHMSEFnUdBNd6pulbtgiTorP_mtJpEsZENYhGBiDEL6Y2D8yqn0Sra": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/CyDnDvF-LaeGPcSW70tPosNCoclByWkTjznUUF1DcgzlIwkN9yzz1ZFME1TlPj6W")},
+
+			"lock":    {Mode: 0644},
+			"variant": {Mode: 0400},
+
+			"status": {Mode: fs.ModeDir | 0700},
+			"status/xxQ43VMIS1WHMSEFnUdBNd6pulbtgiTorP_mtJpEsZENYhGBiDEL6Y2D8yqn0Sra": {Mode: 0400, Data: []byte(statusHeader + "kept")},
+			"status/td1tf1kb3z8iUFg2k1xlHeTTEz3xR4e77WSWdv2JhjmZyY6iuvodhdT8BblDOi0E": {Mode: 0400, Data: []byte(statusHeader + "kept")},
+
+			"substitute": {Mode: fs.ModeDir | 0700},
+			"substitute/td1tf1kb3z8iUFg2k1xlHeTTEz3xR4e77WSWdv2JhjmZyY6iuvodhdT8BblDOi0E": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/CyDnDvF-LaeGPcSW70tPosNCoclByWkTjznUUF1DcgzlIwkN9yzz1ZFME1TlPj6W")},
+
+			"fault": {Mode: fs.ModeDir | 0700},
+			"work":  {Mode: fs.ModeDir | 0700},
+		}, []unique.Handle[pkg.ID]{
+			ic.Ident(pkg.NewFile("destroyed-input", []byte("destroyed"))),
+			ic.Ident(&stubArtifactF{
+				kind:   pkg.KindExec,
+				params: []byte("destroyed"),
+				deps: []pkg.Artifact{
+					pkg.NewFile("destroyed-input", []byte("destroyed")),
+				},
+			}),
+		}, []unique.Handle[pkg.Checksum]{
+			unique.Make(expectsFS{
+				".":      {Mode: fs.ModeDir | 0500},
+				"result": {Mode: 0444},
+			}.hash()),
+			unique.Make(sha512.Sum384([]byte("destroyed"))),
+		}},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			base := makeBase(t)
+			msg := message.New(log.New(os.Stderr, "clean: ", 0))
+			msg.SwapVerbose(testing.Verbose())
+			c, err := pkg.Open(t.Context(), msg, base, nil)
+			if err != nil {
+				t.Fatal(err)
+			}
+			t.Cleanup(c.Close)
+
+			all := pkg.Collect(slices.Concat(tc.a, tc.keep))
+			if _, _, err = c.Cure(&all); !pkg.IsCollected(err) {
+				t.Fatal(err)
+			}
+
+			var (
+				idents    []unique.Handle[pkg.ID]
+				checksums []unique.Handle[pkg.Checksum]
+			)
+			idents, checksums, err = c.Clean(false, tc.inputs, tc.keep...)
+			if err != nil {
+				t.Fatalf("Clean: error = %v", err)
+			}
+			var buf [2]pkg.Checksum
+
+			slices.SortFunc(idents, func(a, b unique.Handle[pkg.ID]) int {
+				buf[0], buf[1] = a.Value(), b.Value()
+				return bytes.Compare(buf[0][:], buf[1][:])
+			})
+			slices.SortFunc(checksums, func(a, b unique.Handle[pkg.Checksum]) int {
+				buf[0], buf[1] = a.Value(), b.Value()
+				return bytes.Compare(buf[0][:], buf[1][:])
+			})
+
+			if !slices.Equal(idents, tc.wantIdents) {
+				t.Errorf(
+					"Clean: idents = %s, want %s",
+					formatHandles(idents...), formatHandles(tc.wantIdents...),
+				)
+			}
+			if !slices.Equal(checksums, tc.wantChecksums) {
+				t.Errorf(
+					"Clean: checksums = %s, want %s",
+					formatHandles(checksums...), formatHandles(tc.wantChecksums...),
+				)
+			}
+
+			want := tc.want.hash()
+			var checksum pkg.Checksum
+			if err = pkg.SumDir(&checksum, base); err != nil {
+				t.Fatalf("SumDir: error = %v", err)
+			} else if checksum != want {
+				t.Error(expectsFrom(base.String()))
+			}
+		})
+	}
+}

internal/pkg/compress.go

@@ -0,0 +1,151 @@
+package pkg
+
+import (
+	"compress/bzip2"
+	"compress/gzip"
+	"fmt"
+	"io"
+	"os"
+
+	"hakurei.app/internal/xz"
+	"hakurei.app/internal/zstd"
+)
+
+const (
+	// Gzip denotes a stream compressed via [gzip].
+	Gzip = iota
+	// Bzip2 denotes a stream compressed via [bzip2].
+	Bzip2
+	// Zstd denotes a stream compressed via [zstd].
+	Zstd
+	// XZ denotes a stream compressed via [xz].
+	XZ
+)
+
+// A decompressArtifact is a [FileArtifact] decompressing a backing
+// [FileArtifact] stream.
+type decompressArtifact struct {
+	// Caller-supplied backing stream.
+	f Artifact
+	// Compression on top of the stream.
+	compress uint32
+}
+
+var _ FileArtifact = new(decompressArtifact)
+var _ CuresExempt = new(decompressArtifact)
+
+// decompressArtifactNamed embeds decompressArtifact for a [fmt.Stringer] stream.
+type decompressArtifactNamed struct {
+	decompressArtifact
+	// Copied from decompressArtifact.f.
+	name string
+}
+
+var _ fmt.Stringer = new(decompressArtifactNamed)
+
+// NewDecompress returns a [FileArtifact] decompressing the supplied [Artifact].
+func NewDecompress(a Artifact, compress uint32) FileArtifact {
+	da := decompressArtifact{a, compress}
+	if s, ok := a.(fmt.Stringer); ok {
+		if name := s.String(); name != "" {
+			return &decompressArtifactNamed{da, name}
+		}
+	}
+	return &da
+}
+
+// String returns the name of the underlying [Artifact] prefixed with decompress.
+func (a *decompressArtifactNamed) String() string { return "decompress-" + a.name }
+
+// Kind returns the hardcoded [Kind] constant.
+func (a *decompressArtifact) Kind() Kind { return KindDecompress }
+
+// Params writes value of compression enum.
+func (a *decompressArtifact) Params(ctx *IContext) { ctx.WriteUint32(a.compress) }
+
+func init() {
+	register(KindDecompress, func(r *IRReader) Artifact {
+		a := NewDecompress(r.Next(), r.ReadUint32())
+		if _, ok := r.Finalise(); ok {
+			panic(ErrUnexpectedChecksum)
+		}
+		return a
+	})
+}
+
+// Inputs returns a slice containing the backing file.
+func (a *decompressArtifact) Inputs() []Artifact {
+	return []Artifact{a.f}
+}
+
+// IsExclusive returns false: decompressor is fully sequential.
+func (a *decompressArtifact) IsExclusive() bool { return false }
+
+// compoundCloser is an [io.ReadCloser] with an additional [io.Closer] attached.
+type compoundCloser struct {
+	io.ReadCloser
+	c io.Closer
+}
+
+// Close closes [io.ReadCloser] and the additional [io.Closer]. It returns the
+// non-nil error returned by the underlying [io.ReadCloser], otherwise it
+// returns the error returned by the additional [io.Closer].
+func (c compoundCloser) Close() error {
+	err := c.ReadCloser.Close()
+	if _err := c.c.Close(); err == nil {
+		err = _err
+	}
+	return err
+}
+
+// IsExecutable returns false.
+func (*decompressArtifact) IsExecutable() bool { return false }
+
+// Cure returns a decompressor [io.ReadCloser].
+func (a *decompressArtifact) Cure(r *RContext) (io.ReadCloser, error) {
+	sr, err := r.Open(a.f)
+	if err != nil {
+		return nil, err
+	}
+	br := r.cache.getReaderRC(sr)
+
+	var dr io.ReadCloser
+	switch a.compress {
+	case Gzip:
+		if dr, err = gzip.NewReader(br); err != nil {
+			_ = br.Close()
+			return nil, err
+		}
+		return compoundCloser{dr, br}, nil
+
+	case Bzip2:
+		return struct {
+			io.Reader
+			io.Closer
+		}{bzip2.NewReader(br), br}, nil
+
+	case Zstd:
+		return struct {
+			io.Reader
+			io.Closer
+		}{zstd.NewReader(br), br}, nil
+
+	case XZ:
+		var _dr io.Reader
+		if _dr, err = xz.NewReader(br, 0); err != nil {
+			_ = br.Close()
+			return nil, err
+		}
+		return struct {
+			io.Reader
+			io.Closer
+		}{_dr, br}, nil
+
+	default:
+		return nil, os.ErrInvalid
+	}
+}
+
+// CuresExempt exempts the cheap [KindDecompress] implementation often part of
+// a [FileArtifact] pipeline.
+func (*decompressArtifact) CuresExempt() {}

internal/pkg/compress_test.go

@@ -0,0 +1,72 @@
+package pkg_test
+
+import (
+	"bytes"
+	"compress/gzip"
+	"crypto/sha512"
+	"io/fs"
+	"net/http"
+	"testing"
+	"testing/fstest"
+
+	"hakurei.app/check"
+	"hakurei.app/internal/pkg"
+)
+
+func TestDecompress(t *testing.T) {
+	t.Parallel()
+
+	var buf bytes.Buffer
+	gw := gzip.NewWriter(&buf)
+	if _, err := gw.Write([]byte{0}); err != nil {
+		t.Fatal(err)
+	} else if err = gw.Close(); err != nil {
+		t.Fatal(err)
+	}
+	testdata := buf.String()
+
+	var transport http.Transport
+	client := http.Client{Transport: &transport}
+	transport.RegisterProtocol("file", http.NewFileTransportFS(fstest.MapFS{
+		"testdata": {Data: []byte(testdata), Mode: 0400},
+	}))
+	testdataChecksum := func() pkg.Checksum {
+		h := sha512.New384()
+		h.Write([]byte(testdata))
+		return (pkg.Checksum)(h.Sum(nil))
+	}()
+
+	gh := pkg.NewDecompress(pkg.NewHTTPGet(
+		&client,
+		"file:///testdata",
+		testdataChecksum,
+	), pkg.Gzip)
+
+	checkWithCache(t, []cacheTestCase{
+		{"decompress", 0, nil, func(t *testing.T, base *check.Absolute, c *pkg.Cache) {
+			cureMany(t, c, []cureStep{
+				{"close", pkg.NewDecompress(pkg.NewHTTPGet(
+					&client,
+					"file:///testdata",
+					pkg.Checksum{0xfd},
+				), pkg.Gzip), nil, nil, pkg.WNew, &pkg.ChecksumMismatchError{
+					Got:  testdataChecksum,
+					Want: pkg.Checksum{0xfd},
+				}},
+
+				{"gzip", gh, ignorePathname, expectsChecksum(sha512.Sum384([]byte{0})), pkg.WNew, nil},
+			})
+		}, expectsFS{
+			".": {Mode: fs.ModeDir | 0700},
+
+			"checksum": {Mode: fs.ModeDir | 0700},
+			"checksum/" + pkg.Encode(sha512.Sum384([]byte{0})): {Mode: 0400, Data: []byte{0}},
+
+			"identifier": {Mode: fs.ModeDir | 0700},
+			"identifier/" + pkg.Encode(pkg.NewIR().Ident(gh).Value()): {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/vsAhtPNo4waRNOASwrQwcIPTqb3SBuJOXw2G4T1mNmVZM-wrQTRllmgXqcIIoRcX")},
+
+			"substitute": {Mode: fs.ModeDir | 0700},
+			"work":       {Mode: fs.ModeDir | 0700},
+		}},
+	})
+}

internal/pkg/dir.go

@@ -1,203 +0,0 @@
-package pkg
-
-import (
-	"crypto/sha512"
-	"encoding/binary"
-	"errors"
-	"io"
-	"io/fs"
-	"math"
-	"os"
-	"path/filepath"
-	"syscall"
-
-	"hakurei.app/check"
-)
-
-// FlatEntry is a directory entry to be encoded for [Flatten].
-type FlatEntry struct {
-	Mode fs.FileMode // file mode bits
-	Path string      // pathname of the file
-	Data []byte      // file content or symlink destination
-}
-
-/*
-| mode uint32 | path_sz uint32 |
-|        data_sz uint64        |
-|         path string          |
-|         data []byte          |
-*/
-
-// Encode encodes the entry for transmission or hashing.
-func (ent *FlatEntry) Encode(w io.Writer) (n int, err error) {
-	pPathSize := alignSize(len(ent.Path))
-	if pPathSize > math.MaxUint32 {
-		return 0, syscall.E2BIG
-	}
-	pDataSize := alignSize(len(ent.Data))
-
-	payload := make([]byte, wordSize*2+pPathSize+pDataSize)
-	binary.LittleEndian.PutUint32(payload, uint32(ent.Mode))
-	binary.LittleEndian.PutUint32(payload[wordSize/2:], uint32(len(ent.Path)))
-	binary.LittleEndian.PutUint64(payload[wordSize:], uint64(len(ent.Data)))
-	copy(payload[wordSize*2:], ent.Path)
-	copy(payload[wordSize*2+pPathSize:], ent.Data)
-	return w.Write(payload)
-}
-
-// ErrInsecurePath is returned by [FlatEntry.Decode] if validation is requested
-// and a nonlocal path is encountered in the stream.
-var ErrInsecurePath = errors.New("insecure file path")
-
-// Decode decodes the entry from its representation produced by Encode.
-func (ent *FlatEntry) Decode(r io.Reader, validate bool) (n int, err error) {
-	var nr int
-
-	header := make([]byte, wordSize*2)
-	nr, err = r.Read(header)
-	n += nr
-	if err != nil {
-		if errors.Is(err, io.EOF) && n != 0 {
-			err = io.ErrUnexpectedEOF
-		}
-		return
-	}
-
-	ent.Mode = fs.FileMode(binary.LittleEndian.Uint32(header))
-	pathSize := int(binary.LittleEndian.Uint32(header[wordSize/2:]))
-	pPathSize := alignSize(pathSize)
-	dataSize := int(binary.LittleEndian.Uint64(header[wordSize:]))
-	pDataSize := alignSize(dataSize)
-
-	buf := make([]byte, pPathSize+pDataSize)
-	nr, err = r.Read(buf)
-	n += nr
-	if err != nil {
-		if errors.Is(err, io.EOF) {
-			if nr != len(buf) {
-				err = io.ErrUnexpectedEOF
-				return
-			}
-		} else {
-			return
-		}
-	}
-
-	ent.Path = string(buf[:pathSize])
-	if ent.Mode.IsDir() {
-		ent.Data = nil
-	} else {
-		ent.Data = buf[pPathSize : pPathSize+dataSize]
-	}
-
-	if validate && !filepath.IsLocal(ent.Path) {
-		err = ErrInsecurePath
-	}
-
-	return
-}
-
-// DirScanner provides an efficient interface for reading a stream of encoded
-// [FlatEntry]. Successive calls to the Scan method will step through the
-// entries in the stream.
-type DirScanner struct {
-	// Underlying reader to scan [FlatEntry] representations from.
-	r io.Reader
-
-	// First non-EOF I/O error, returned by the Err method.
-	err error
-
-	// Entry to store results in. Its address is returned by the Entry method
-	// and is updated on every call to Scan.
-	ent FlatEntry
-
-	// Validate pathnames during decoding.
-	validate bool
-}
-
-// NewDirScanner returns the address of a new instance of [DirScanner] reading
-// from r. The caller must no longer read from r after this function returns.
-func NewDirScanner(r io.Reader, validate bool) *DirScanner {
-	return &DirScanner{r: r, validate: validate}
-}
-
-// Err returns the first non-EOF I/O error.
-func (s *DirScanner) Err() error {
-	if errors.Is(s.err, io.EOF) {
-		return nil
-	}
-	return s.err
-}
-
-// Entry returns the address to the [FlatEntry] value storing the last result.
-func (s *DirScanner) Entry() *FlatEntry { return &s.ent }
-
-// Scan advances to the next [FlatEntry].
-func (s *DirScanner) Scan() bool {
-	if s.err != nil {
-		return false
-	}
-
-	var n int
-	n, s.err = s.ent.Decode(s.r, s.validate)
-	if errors.Is(s.err, io.EOF) {
-		return n != 0
-	}
-	return s.err == nil
-}
-
-// Flatten writes a deterministic representation of the contents of fsys to w.
-// The resulting data can be hashed to produce a deterministic checksum for the
-// directory.
-func Flatten(fsys fs.FS, root string, w io.Writer) (n int, err error) {
-	var nr int
-	err = fs.WalkDir(fsys, root, func(path string, d fs.DirEntry, err error) error {
-		if err != nil {
-			return err
-		}
-
-		var fi fs.FileInfo
-		fi, err = d.Info()
-		if err != nil {
-			return err
-		}
-
-		ent := FlatEntry{
-			Path: path,
-			Mode: fi.Mode(),
-		}
-		if ent.Mode.IsRegular() {
-			if ent.Data, err = fs.ReadFile(fsys, path); err != nil {
-				return err
-			}
-		} else if ent.Mode&fs.ModeSymlink != 0 {
-			var newpath string
-			if newpath, err = fs.ReadLink(fsys, path); err != nil {
-				return err
-			}
-			ent.Data = []byte(newpath)
-		} else if !ent.Mode.IsDir() {
-			return InvalidFileModeError(ent.Mode)
-		}
-
-		nr, err = ent.Encode(w)
-		n += nr
-		return err
-	})
-	return
-}
-
-// HashFS returns a checksum produced by hashing the result of [Flatten].
-func HashFS(buf *Checksum, fsys fs.FS, root string) error {
-	h := sha512.New384()
-	if _, err := Flatten(fsys, root, h); err != nil {
-		return err
-	}
-	h.Sum(buf[:0])
-	return nil
-}
-
-// HashDir returns a checksum produced by hashing the result of [Flatten].
-func HashDir(buf *Checksum, pathname *check.Absolute) error {
-	return HashFS(buf, os.DirFS(pathname.String()), ".")
-}

internal/pkg/dir_test.go

@@ -1,134 +0,0 @@
-package pkg_test
-
-import (
-	"bytes"
-	"io/fs"
-	"reflect"
-	"testing"
-	"testing/fstest"
-
-	"hakurei.app/internal/pkg"
-)
-
-func TestFlatten(t *testing.T) {
-	t.Parallel()
-
-	testCases := []struct {
-		name    string
-		fsys    fs.FS
-		entries []pkg.FlatEntry
-		sum     pkg.Checksum
-		err     error
-	}{
-		{"bad type", fstest.MapFS{
-			".":       {Mode: fs.ModeDir | 0700},
-			"invalid": {Mode: fs.ModeCharDevice | 0400},
-		}, nil, pkg.Checksum{}, pkg.InvalidFileModeError(
-			fs.ModeCharDevice | 0400,
-		)},
-
-		{"coldboot", fstest.MapFS{
-			".": {Mode: fs.ModeDir | 0700},
-
-			"devices":        {Mode: fs.ModeDir | 0700},
-			"devices/uevent": {Mode: 0600, Data: []byte("add")},
-			"devices/empty":  {Mode: fs.ModeDir | 0700},
-
-			"devices/sub":        {Mode: fs.ModeDir | 0700},
-			"devices/sub/uevent": {Mode: 0600, Data: []byte("add")},
-
-			"block":        {Mode: fs.ModeDir | 0700},
-			"block/uevent": {Mode: 0600, Data: []byte{}},
-		}, []pkg.FlatEntry{
-			{Mode: fs.ModeDir | 0700, Path: "."},
-
-			{Mode: fs.ModeDir | 0700, Path: "block"},
-			{Mode: 0600, Path: "block/uevent", Data: []byte{}},
-
-			{Mode: fs.ModeDir | 0700, Path: "devices"},
-			{Mode: fs.ModeDir | 0700, Path: "devices/empty"},
-			{Mode: fs.ModeDir | 0700, Path: "devices/sub"},
-			{Mode: 0600, Path: "devices/sub/uevent", Data: []byte("add")},
-			{Mode: 0600, Path: "devices/uevent", Data: []byte("add")},
-		}, pkg.MustDecode("mEy_Lf5KotThm7OwMx7yTKZh5HCCyaB41pVAvI9uDMgVQFM91iosBLYsRm8bDsX8"), nil},
-
-		{"empty", fstest.MapFS{
-			".":          {Mode: fs.ModeDir | 0700},
-			"checksum":   {Mode: fs.ModeDir | 0700},
-			"identifier": {Mode: fs.ModeDir | 0700},
-			"work":       {Mode: fs.ModeDir | 0700},
-		}, []pkg.FlatEntry{
-			{Mode: fs.ModeDir | 0700, Path: "."},
-			{Mode: fs.ModeDir | 0700, Path: "checksum"},
-			{Mode: fs.ModeDir | 0700, Path: "identifier"},
-			{Mode: fs.ModeDir | 0700, Path: "work"},
-		}, pkg.MustDecode("E4vEZKhCcL2gPZ2Tt59FS3lDng-d_2SKa2i5G_RbDfwGn6EemptFaGLPUDiOa94C"), nil},
-
-		{"sample directory step garbage", fstest.MapFS{
-			".": {Mode: fs.ModeDir | 0500},
-
-			"lib":       {Mode: fs.ModeDir | 0500},
-			"lib/check": {Mode: 0400, Data: []byte{}},
-
-			"lib/pkgconfig": {Mode: fs.ModeDir | 0500},
-		}, []pkg.FlatEntry{
-			{Mode: fs.ModeDir | 0500, Path: "."},
-
-			{Mode: fs.ModeDir | 0500, Path: "lib"},
-			{Mode: 0400, Path: "lib/check", Data: []byte{}},
-
-			{Mode: fs.ModeDir | 0500, Path: "lib/pkgconfig"},
-		}, pkg.MustDecode("CUx-3hSbTWPsbMfDhgalG4Ni_GmR9TnVX8F99tY_P5GtkYvczg9RrF5zO0jX9XYT"), nil},
-	}
-	for _, tc := range testCases {
-		t.Run(tc.name, func(t *testing.T) {
-			t.Parallel()
-
-			t.Run("roundtrip", func(t *testing.T) {
-				t.Parallel()
-
-				var buf bytes.Buffer
-				if _, err := pkg.Flatten(
-					tc.fsys,
-					".",
-					&buf,
-				); !reflect.DeepEqual(err, tc.err) {
-					t.Fatalf("Flatten: error = %v, want %v", err, tc.err)
-				} else if tc.err != nil {
-					return
-				}
-
-				s := pkg.NewDirScanner(bytes.NewReader(buf.Bytes()), true)
-				var got []pkg.FlatEntry
-				for s.Scan() {
-					got = append(got, *s.Entry())
-				}
-				if err := s.Err(); err != nil {
-					t.Fatalf("Err: error = %v", err)
-				}
-
-				if !reflect.DeepEqual(got, tc.entries) {
-					t.Fatalf("Scan: %#v, want %#v", got, tc.entries)
-				}
-			})
-
-			if tc.err != nil {
-				return
-			}
-
-			t.Run("hash", func(t *testing.T) {
-				t.Parallel()
-
-				var got pkg.Checksum
-				if err := pkg.HashFS(&got, tc.fsys, "."); err != nil {
-					t.Fatalf("HashFS: error = %v", err)
-				} else if got != tc.sum {
-					t.Fatalf("HashFS: %v", &pkg.ChecksumMismatchError{
-						Got:  got,
-						Want: tc.sum,
-					})
-				}
-			})
-		})
-	}
-}

internal/pkg/exec.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"maps"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -29,10 +30,16 @@ import (
 // AbsWork is the container pathname [TContext.GetWorkDir] is mounted on.
 var AbsWork = fhs.AbsRoot.Append("work/")
 
-// EnvJobs is the name of the environment variable holding a decimal
-// representation of the preferred job count. Its value must not affect cure
-// outcome.
-const EnvJobs = "CURE_JOBS"
+const (
+	// EnvJobs is the name of the environment variable holding a decimal
+	// representation of the preferred job count. Its value must not affect cure
+	// outcome.
+	EnvJobs = "CURE_JOBS"
+	// EnvLoad is the name of the environment variable holding a decimal
+	// representation of the preferred loadavg target. Its value must not affect
+	// cure outcome.
+	EnvLoad = "CURE_LOAD"
+)
 
 // ExecPath is a slice of [Artifact] and the [check.Absolute] pathname to make
 // it available at under in the container.
@@ -122,6 +129,15 @@ func RegisterArch(arch string, e container.BinfmtEntry) {
 	binfmt[arch] = e
 }
 
+// Arch returns a snapshot of currently registered [KindExec] and [KindExecNet]
+// binfmt entries.
+func Arch() map[string]container.BinfmtEntry {
+	binfmtMu.RLock()
+	r := maps.Clone(binfmt)
+	binfmtMu.RUnlock()
+	return r
+}
+
 const (
 	// ExecTimeoutDefault replaces out of range [NewExec] timeout values.
 	ExecTimeoutDefault = 15 * time.Minute
@@ -397,9 +413,9 @@ func init() {
 		func(r *IRReader) Artifact { return readExecArtifact(r, true) })
 }
 
-// Dependencies returns a slice of all artifacts collected from caller-supplied
+// Inputs returns a slice of all artifacts collected from caller-supplied
 // [ExecPath].
-func (a *execArtifact) Dependencies() []Artifact {
+func (a *execArtifact) Inputs() []Artifact {
 	artifacts := make([][]Artifact, 0, len(a.paths))
 	for _, p := range a.paths {
 		artifacts = append(artifacts, p.A)
@@ -428,7 +444,7 @@ func scanVerbose(
 	msg message.Msg,
 	cancel context.CancelFunc,
 	done chan<- struct{},
-	prefix string,
+	prefix, suffix string,
 	r io.Reader,
 ) {
 	defer close(done)
@@ -438,7 +454,7 @@ func scanVerbose(
 		bufio.MaxScanTokenSize<<12,
 	)
 	for s.Scan() {
-		msg.Verbose(prefix, s.Text())
+		msg.Verbose(prefix, s.Text()+suffix)
 	}
 	if err := s.Err(); err != nil && !errors.Is(err, os.ErrClosed) {
 		cancel()
@@ -461,7 +477,7 @@ const SeccompPresets = std.PresetStrict &
 func (a *execArtifact) makeContainer(
 	ctx context.Context,
 	msg message.Msg,
-	flags, jobs int,
+	flags, jobs, load int,
 	hostNet bool,
 	temp, work *check.Absolute,
 	getArtifact GetArtifactFunc,
@@ -498,7 +514,10 @@ func (a *execArtifact) makeContainer(
 	z.Quiet = flags&CSuppressInit != 0
 	z.Uid, z.Gid = (1<<10)-1, (1<<10)-1
 	z.Dir, z.Path, z.Args = a.dir, a.path, a.args
-	z.Env = slices.Concat(a.env, []string{EnvJobs + "=" + strconv.Itoa(jobs)})
+	z.Env = slices.Concat(a.env, []string{
+		EnvJobs + "=" + strconv.Itoa(jobs),
+		EnvLoad + "=" + strconv.Itoa(load),
+	})
 	z.Grow(len(a.paths) + 4)
 
 	if a.arch != runtime.GOARCH {
@@ -581,6 +600,7 @@ var (
 func (c *Cache) EnterExec(
 	ctx context.Context,
 	a Artifact,
+	hostname string,
 	retainSession bool,
 	stdin io.Reader,
 	stdout, stderr io.Writer,
@@ -606,7 +626,7 @@ func (c *Cache) EnterExec(
 		return ErrNotExec
 	}
 
-	deps := Collect(a.Dependencies())
+	deps := Collect(a.Inputs())
 	if _, _, err = c.Cure(&deps); err == nil {
 		return errors.New("unreachable")
 	} else if !IsCollected(err) {
@@ -638,8 +658,9 @@ func (c *Cache) EnterExec(
 	var z *container.Container
 	z, err = e.makeContainer(
 		ctx, c.msg,
-		c.flags,
-		c.jobs,
+		c.attr.Flags,
+		c.attr.Jobs,
+		c.attr.Load,
 		hostNet,
 		temp, work,
 		func(a Artifact) (*check.Absolute, unique.Handle[Checksum]) {
@@ -661,6 +682,9 @@ func (c *Cache) EnterExec(
 			z.Env = append(z.Env, "TERM="+s)
 		}
 	}
+	if hostname != "" {
+		z.Hostname = hostname
+	}
 
 	if err = z.Start(); err != nil {
 		return
@@ -679,7 +703,7 @@ func (a *execArtifact) cure(f *FContext, hostNet bool) (err error) {
 	msg := f.GetMessage()
 	var z *container.Container
 	if z, err = a.makeContainer(
-		ctx, msg, f.cache.flags, f.GetJobs(), hostNet,
+		ctx, msg, f.cache.attr.Flags, f.GetJobs(), f.GetLoad(), hostNet,
 		f.GetTempDir(), f.GetWorkDir(),
 		f.GetArtifact,
 		f.cache.Ident,
@@ -704,14 +728,25 @@ func (a *execArtifact) cure(f *FContext, hostNet bool) (err error) {
 
 		brStdout, brStderr := f.cache.getReader(stdout), f.cache.getReader(stderr)
 		stdoutDone, stderrDone := make(chan struct{}), make(chan struct{})
+
+		var suffix, prefixO, prefixE string
+		if f.cache.attr.Flags&CColourOutput != 0 {
+			suffix = "\x1b[0m"
+			prefixO = "\x1b[1;37m(" + a.name + ")\x1b[0m"
+			prefixE = "\x1b[1;97m(" + a.name + ")\x1b[0m"
+		} else {
+			prefixO = "(" + a.name + ":1)"
+			prefixE = "(" + a.name + ":2)"
+		}
+
 		go scanVerbose(
 			msg, cancel, stdoutDone,
-			"("+a.name+":1)",
+			prefixO, suffix,
 			io.TeeReader(brStdout, status),
 		)
 		go scanVerbose(
 			msg, cancel, stderrDone,
-			"("+a.name+":2)",
+			prefixE, suffix,
 			io.TeeReader(brStderr, status),
 		)
 		defer func() {

internal/pkg/exec_test.go

@@ -84,7 +84,7 @@ func TestExec(t *testing.T) {
 						},
 					}),
 					pkg.MustPath("/opt", false, testtool),
-				), ignorePathname, wantOffline, nil},
+				), ignorePathname, wantOffline, pkg.WNew, nil},
 
 				{"substitution", pkg.NewExec(
 					"exec-offline", "", new(wantOffline.hash()), 0, false, false,
@@ -108,7 +108,7 @@ func TestExec(t *testing.T) {
 						},
 					}),
 					pkg.MustPath("/opt", false, testtool),
-				), ignorePathname, wantOffline, nil},
+				), ignorePathname, wantOffline, pkg.WSubstitute, nil},
 
 				{"error passthrough", pkg.NewExec(
 					"", "", nil, 0, false, true,
@@ -118,11 +118,8 @@ func TestExec(t *testing.T) {
 					[]string{"testtool"},
 
 					pkg.MustPath("/proc/nonexistent", false, failingArtifact),
-				), nil, nil, &pkg.DependencyCureError{
-					{
-						A:   failingArtifact,
-						Err: stub.UniqueError(0xcafe),
-					},
+				), nil, nil, pkg.WNew, pkg.InputError{
+					failingArtifact: stub.UniqueError(0xcafe),
 				}},
 
 				{"invalid paths", pkg.NewExec(
@@ -133,7 +130,7 @@ func TestExec(t *testing.T) {
 					[]string{"testtool"},
 
 					pkg.ExecPath{},
-				), nil, nil, pkg.ErrInvalidPaths},
+				), nil, nil, pkg.WNew, pkg.ErrInvalidPaths},
 			})
 
 			// check init failure passthrough
@@ -183,11 +180,11 @@ func TestExec(t *testing.T) {
 			"checksum/OLBgp1GsljhM2TJ-sbHjaiH9txEUvgdDTAzHv2P24donTt6_529l-9Ua0vFImLlb": {Mode: 0400, Data: []byte{}},
 
 			"identifier": {Mode: fs.ModeDir | 0700},
-			"identifier/QwS7SmiatdqryQYgESdGw7Yw2PcpNf0vNfpvUA0t92BTlKiUjfCrXyMW17G2X77X": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/MGWmEfjut2QE2xPJwTsmUzpff4BN_FEnQ7T0j7gvUCCiugJQNwqt9m151fm9D1yU")},
+			"identifier/MEaM1v6MLRQ60JQOOKbfDzfJOdC3L8i30IgOpYbQdX68enwF0FN-P36_M4RX_0Vd": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/MGWmEfjut2QE2xPJwTsmUzpff4BN_FEnQ7T0j7gvUCCiugJQNwqt9m151fm9D1yU")},
 			"identifier/_gAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/OLBgp1GsljhM2TJ-sbHjaiH9txEUvgdDTAzHv2P24donTt6_529l-9Ua0vFImLlb")},
 			"identifier/" + expected.Offline:                                              {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/" + wantOfflineEncode)},
 			"identifier/" + expected.OfflineS:                                             {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/" + wantOfflineEncode)},
-			"identifier/vjz1MHPcGBKV7sjcs8jQP3cqxJ1hgPTiQBMCEHP9BGXjGxd-tJmEmXKaStObo5gK": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/MGWmEfjut2QE2xPJwTsmUzpff4BN_FEnQ7T0j7gvUCCiugJQNwqt9m151fm9D1yU")},
+			"identifier/_OHzj_xdmfpaWfFN-_D9JpGpPlIjh84873E3Ui9xwv9PPPIt0BlzvH-cnPNeRsTl": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/MGWmEfjut2QE2xPJwTsmUzpff4BN_FEnQ7T0j7gvUCCiugJQNwqt9m151fm9D1yU")},
 
 			"substitute": {Mode: fs.ModeDir | 0700},
 
@@ -225,7 +222,7 @@ func TestExec(t *testing.T) {
 						},
 					}),
 					pkg.MustPath("/opt", false, testtool),
-				), ignorePathname, wantNet, nil},
+				), ignorePathname, wantNet, pkg.WNew, nil},
 			})
 
 			destroyStatus(t, base, 2, 0)
@@ -242,7 +239,7 @@ func TestExec(t *testing.T) {
 			"identifier":                 {Mode: fs.ModeDir | 0700},
 			"identifier/" + expected.Net: {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/a1F_i9PVQI4qMcoHgTQkORuyWLkC1GLIxOhDt2JpU1NGAxWc5VJzdlfRK-PYBh3W")},
 			"identifier/_gAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/OLBgp1GsljhM2TJ-sbHjaiH9txEUvgdDTAzHv2P24donTt6_529l-9Ua0vFImLlb")},
-			"identifier/vjz1MHPcGBKV7sjcs8jQP3cqxJ1hgPTiQBMCEHP9BGXjGxd-tJmEmXKaStObo5gK": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/MGWmEfjut2QE2xPJwTsmUzpff4BN_FEnQ7T0j7gvUCCiugJQNwqt9m151fm9D1yU")},
+			"identifier/MEaM1v6MLRQ60JQOOKbfDzfJOdC3L8i30IgOpYbQdX68enwF0FN-P36_M4RX_0Vd": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/MGWmEfjut2QE2xPJwTsmUzpff4BN_FEnQ7T0j7gvUCCiugJQNwqt9m151fm9D1yU")},
 
 			"substitute": {Mode: fs.ModeDir | 0700},
 
@@ -269,7 +266,7 @@ func TestExec(t *testing.T) {
 						},
 					}),
 					pkg.MustPath("/opt", false, testtool),
-				), ignorePathname, wantOffline, nil},
+				), ignorePathname, wantOffline, pkg.WNew, nil},
 			})
 
 			destroyStatus(t, base, 2, 0)
@@ -284,7 +281,7 @@ func TestExec(t *testing.T) {
 
 			"identifier":                     {Mode: fs.ModeDir | 0700},
 			"identifier/" + expected.OvlRoot: {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/" + wantOfflineEncode)},
-			"identifier/vjz1MHPcGBKV7sjcs8jQP3cqxJ1hgPTiQBMCEHP9BGXjGxd-tJmEmXKaStObo5gK": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/MGWmEfjut2QE2xPJwTsmUzpff4BN_FEnQ7T0j7gvUCCiugJQNwqt9m151fm9D1yU")},
+			"identifier/MEaM1v6MLRQ60JQOOKbfDzfJOdC3L8i30IgOpYbQdX68enwF0FN-P36_M4RX_0Vd": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/MGWmEfjut2QE2xPJwTsmUzpff4BN_FEnQ7T0j7gvUCCiugJQNwqt9m151fm9D1yU")},
 
 			"substitute": {Mode: fs.ModeDir | 0700},
 
@@ -316,7 +313,7 @@ func TestExec(t *testing.T) {
 							return os.MkdirAll(t.GetWorkDir().String(), 0700)
 						},
 					}), pkg.Path(pkg.AbsWork, false /* ignored */, testtool),
-				), ignorePathname, wantOffline, nil},
+				), ignorePathname, wantOffline, pkg.WNew, nil},
 			})
 
 			destroyStatus(t, base, 2, 0)
@@ -331,7 +328,7 @@ func TestExec(t *testing.T) {
 
 			"identifier":                  {Mode: fs.ModeDir | 0700},
 			"identifier/" + expected.Work: {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/" + wantOfflineEncode)},
-			"identifier/vjz1MHPcGBKV7sjcs8jQP3cqxJ1hgPTiQBMCEHP9BGXjGxd-tJmEmXKaStObo5gK": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/MGWmEfjut2QE2xPJwTsmUzpff4BN_FEnQ7T0j7gvUCCiugJQNwqt9m151fm9D1yU")},
+			"identifier/MEaM1v6MLRQ60JQOOKbfDzfJOdC3L8i30IgOpYbQdX68enwF0FN-P36_M4RX_0Vd": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/MGWmEfjut2QE2xPJwTsmUzpff4BN_FEnQ7T0j7gvUCCiugJQNwqt9m151fm9D1yU")},
 
 			"substitute": {Mode: fs.ModeDir | 0700},
 
@@ -385,7 +382,7 @@ func TestExec(t *testing.T) {
 						},
 					}),
 					pkg.MustPath("/opt", false, testtool),
-				), ignorePathname, wantOffline, nil},
+				), ignorePathname, wantOffline, pkg.WNew, nil},
 			})
 
 			destroyStatus(t, base, 2, 0)
@@ -403,9 +400,9 @@ func TestExec(t *testing.T) {
 
 			"identifier": {Mode: fs.ModeDir | 0700},
 			"identifier/_gAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/OLBgp1GsljhM2TJ-sbHjaiH9txEUvgdDTAzHv2P24donTt6_529l-9Ua0vFImLlb")},
-			"identifier/B-kc5iJMx8GtlCua4dz6BiJHnDAOUfPjgpbKq4e-QEn0_CZkSYs3fOA1ve06qMs2": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/nY_CUdiaUM1OL4cPr5TS92FCJ3rCRV7Hm5oVTzAvMXwC03_QnTRfQ5PPs7mOU9fK")},
+			"identifier/2uIvmnqtzAx4Ed4PWV8xjZCWeJCwfE2IcCc0evM-Nd8mDUlgSU6nLtPLcpPUcMlG": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/nY_CUdiaUM1OL4cPr5TS92FCJ3rCRV7Hm5oVTzAvMXwC03_QnTRfQ5PPs7mOU9fK")},
 			"identifier/" + expected.Layers:                                               {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/" + wantOfflineEncode)},
-			"identifier/vjz1MHPcGBKV7sjcs8jQP3cqxJ1hgPTiQBMCEHP9BGXjGxd-tJmEmXKaStObo5gK": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/MGWmEfjut2QE2xPJwTsmUzpff4BN_FEnQ7T0j7gvUCCiugJQNwqt9m151fm9D1yU")},
+			"identifier/MEaM1v6MLRQ60JQOOKbfDzfJOdC3L8i30IgOpYbQdX68enwF0FN-P36_M4RX_0Vd": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/MGWmEfjut2QE2xPJwTsmUzpff4BN_FEnQ7T0j7gvUCCiugJQNwqt9m151fm9D1yU")},
 
 			"substitute": {Mode: fs.ModeDir | 0700},
 
@@ -438,7 +435,7 @@ func TestExec(t *testing.T) {
 						},
 					}),
 					pkg.MustPath("/opt", false, testtool),
-				), ignorePathname, wantOffline, nil},
+				), ignorePathname, wantOffline, pkg.WNew, nil},
 			})
 
 			destroyStatus(t, base, 2, 0)
@@ -452,8 +449,8 @@ func TestExec(t *testing.T) {
 			"checksum/MGWmEfjut2QE2xPJwTsmUzpff4BN_FEnQ7T0j7gvUCCiugJQNwqt9m151fm9D1yU": {Mode: fs.ModeDir | 0500},
 
 			"identifier": {Mode: fs.ModeDir | 0700},
-			"identifier/kvJIqZo5DKFOxC2ZQ-8_nPaQzEAz9cIm3p6guO-uLqm-xaiPu7oRkSnsu411jd_U": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/MGWmEfjut2QE2xPJwTsmUzpff4BN_FEnQ7T0j7gvUCCiugJQNwqt9m151fm9D1yU")},
-			"identifier/vjz1MHPcGBKV7sjcs8jQP3cqxJ1hgPTiQBMCEHP9BGXjGxd-tJmEmXKaStObo5gK": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/MGWmEfjut2QE2xPJwTsmUzpff4BN_FEnQ7T0j7gvUCCiugJQNwqt9m151fm9D1yU")},
+			"identifier/Vzj9qaSVBtNyBQv_PW6uojFOWTwraHoaC0C6xdaGG1q_HTvSh4KLVxRcEQU1jd2Y": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/MGWmEfjut2QE2xPJwTsmUzpff4BN_FEnQ7T0j7gvUCCiugJQNwqt9m151fm9D1yU")},
+			"identifier/MEaM1v6MLRQ60JQOOKbfDzfJOdC3L8i30IgOpYbQdX68enwF0FN-P36_M4RX_0Vd": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/MGWmEfjut2QE2xPJwTsmUzpff4BN_FEnQ7T0j7gvUCCiugJQNwqt9m151fm9D1yU")},
 			"identifier/" + expected.Promote:                                              {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/" + wantOfflineEncode)},
 
 			"substitute": {Mode: fs.ModeDir | 0700},
@@ -503,7 +500,7 @@ func TestExec(t *testing.T) {
 					".": {Mode: fs.ModeDir | 0500},
 
 					"check": {Mode: 0400, Data: []byte("binfmt")},
-				}, nil},
+				}, pkg.WNew, nil},
 			})
 
 			destroyStatus(t, base, 2, 0)
@@ -519,9 +516,9 @@ func TestExec(t *testing.T) {
 			"checksum/UnDo4B5KneEUY5b4vRUk_y9MWgkWuw2N8f8a2XayO686xXur-aZmX2-7n_8tKMe3/check":      {Mode: 0400, Data: []byte("binfmt")},
 
 			"identifier": {Mode: fs.ModeDir | 0700},
-			"identifier/6VQTJ1lI5BmVuI1YFYJ8ClO3MRORvTTrcWFDcUU-l5Ga8EofxCxGlSTYN-u8dKj_": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/UnDo4B5KneEUY5b4vRUk_y9MWgkWuw2N8f8a2XayO686xXur-aZmX2-7n_8tKMe3")},
+			"identifier/c-HodmoEG0f_WGdst9aN-duLMH7QDDXOUi7UcyArXMeM1fc9lYKKQlTCW8ktaK8X": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/UnDo4B5KneEUY5b4vRUk_y9MWgkWuw2N8f8a2XayO686xXur-aZmX2-7n_8tKMe3")},
 			"identifier/_v8AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/5aevg3YpDxjqQZ-pdvXK7YqgkL5JKqcoStYQxeD96kuYar6K2mRQWMHib6NQRnpV")},
-			"identifier/vjz1MHPcGBKV7sjcs8jQP3cqxJ1hgPTiQBMCEHP9BGXjGxd-tJmEmXKaStObo5gK": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/MGWmEfjut2QE2xPJwTsmUzpff4BN_FEnQ7T0j7gvUCCiugJQNwqt9m151fm9D1yU")},
+			"identifier/MEaM1v6MLRQ60JQOOKbfDzfJOdC3L8i30IgOpYbQdX68enwF0FN-P36_M4RX_0Vd": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/MGWmEfjut2QE2xPJwTsmUzpff4BN_FEnQ7T0j7gvUCCiugJQNwqt9m151fm9D1yU")},
 
 			"substitute": {Mode: fs.ModeDir | 0700},
 

internal/pkg/file.go

@@ -11,6 +11,8 @@ import (
 type fileArtifact []byte
 
 var _ KnownChecksum = new(fileArtifact)
+var _ CuresExempt = new(fileArtifact)
+var _ RevisionArtifact = new(fileArtifact)
 
 // fileArtifactNamed embeds fileArtifact alongside a caller-supplied name.
 type fileArtifactNamed struct {
@@ -62,8 +64,8 @@ func init() {
 	})
 }
 
-// Dependencies returns a nil slice.
-func (*fileArtifact) Dependencies() []Artifact { return nil }
+// Inputs returns a nil slice.
+func (*fileArtifact) Inputs() []Artifact { return nil }
 
 // IsExclusive returns false: Cure returns a prepopulated buffer.
 func (*fileArtifact) IsExclusive() bool { return false }
@@ -75,7 +77,24 @@ func (a *fileArtifact) Checksum() Checksum {
 	return Checksum(h.Sum(nil))
 }
 
+// Revision satisfies [RevisionArtifact] for incompatible IsExecutable behaviour.
+func (*fileArtifact) Revision() uint64 { return 0 }
+
+// IsExecutable returns whether the contents begin with shebang or the ELF
+// magic number.
+func (a *fileArtifact) IsExecutable() bool {
+	return a != nil &&
+		(bytes.HasPrefix(
+			*a, []byte{'#', '!'},
+		) || bytes.HasPrefix(
+			*a, []byte{0x7f, 'E', 'L', 'F'},
+		))
+}
+
 // Cure returns the caller-supplied data.
 func (a *fileArtifact) Cure(*RContext) (io.ReadCloser, error) {
 	return io.NopCloser(bytes.NewReader(*a)), nil
 }
+
+// CuresExempt exempts the cheap [KindFile] implementation.
+func (*fileArtifact) CuresExempt() {}

internal/pkg/file_test.go

@@ -12,22 +12,41 @@ func TestFile(t *testing.T) {
 	t.Parallel()
 
 	want := expectsFile{0}
+	const ident = "N7M6W8-e55Wky_1q1a6qRKFVDw1S5XtPdB4HE2YZObG8OFum8HittyJgZUG5Ru2u"
+	wantShebang := expectsFile("#!/bin/sh\n")
+	const identShebang = "oKTGZb_TRtJf5G1iGGj4SOx1WUbI6YhmsUeEsCNvmK9tZYRwdwQf-DLFUxRPx5qm"
+	wantELF := expectsFile("\x7fELF\xde\xad\xbe\xef")
+	const identELF = "LjeHmIJgD1SiXIH8ewpGRed2_LU84NLapstnOAa_0hxLd8YY7x4KM0aApsj-RwCh"
 	checkWithCache(t, []cacheTestCase{
 		{"file", pkg.CValidateKnown, nil, func(t *testing.T, base *check.Absolute, c *pkg.Cache) {
 			cureMany(t, c, []cureStep{
-				{"short", pkg.NewFile("null", []byte{0}), base.Append(
+				{"short", pkg.NewFile("null", want), base.Append(
 					"identifier",
-					"3376ALA7hIUm2LbzH2fDvRezgzod1eTK_G6XjyOgbM2u-6swvkFaF0BOwSl_juBi",
-				), want, nil},
+					ident,
+				), want, pkg.WNew, nil},
+
+				{"shebang", pkg.NewFile("shebang", wantShebang), base.Append(
+					"identifier",
+					identShebang,
+				), wantShebang, pkg.WNew, nil},
+
+				{"elf", pkg.NewFile("ELF", wantELF), base.Append(
+					"identifier",
+					identELF,
+				), wantELF, pkg.WNew, nil},
 			})
 		}, expectsFS{
 			".": {Mode: fs.ModeDir | 0700},
 
-			"checksum":                            {Mode: fs.ModeDir | 0700},
-			"checksum/" + pkg.Encode(want.hash()): {Mode: 0400, Data: []byte{0}},
+			"checksum":                                   {Mode: fs.ModeDir | 0700},
+			"checksum/" + pkg.Encode(want.hash()):        {Mode: 0400, Data: want},
+			"checksum/" + pkg.Encode(wantShebang.hash()): {Mode: 0500, Data: wantShebang},
+			"checksum/" + pkg.Encode(wantELF.hash()):     {Mode: 0500, Data: wantELF},
 
-			"identifier": {Mode: fs.ModeDir | 0700},
-			"identifier/3376ALA7hIUm2LbzH2fDvRezgzod1eTK_G6XjyOgbM2u-6swvkFaF0BOwSl_juBi": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/vsAhtPNo4waRNOASwrQwcIPTqb3SBuJOXw2G4T1mNmVZM-wrQTRllmgXqcIIoRcX")},
+			"identifier":                 {Mode: fs.ModeDir | 0700},
+			"identifier/" + ident:        {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/" + pkg.Encode(want.hash()))},
+			"identifier/" + identShebang: {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/" + pkg.Encode(wantShebang.hash()))},
+			"identifier/" + identELF:     {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/" + pkg.Encode(wantELF.hash()))},
 
 			"substitute": {Mode: fs.ModeDir | 0700},
 

internal/pkg/internal/testtool/expected/sum_amd64.go

@@ -1,11 +1,11 @@
 package expected
 
 const (
-	Offline  = "q5ktDTq0miP-VvB2blxqXQeaRXCUWgP_KbC18KNtUDtyoaI_h5mHmGuPMArVEBDs"
-	OfflineS = "IY91PCtOpCYy21AaIK0c9f8-Z6fb2_2ewoHWkt4dxoLf0GOrWqS8yAGFLV84b1Dw"
-	OvlRoot  = "NacZGXwuRkTvcHaG08a22ujJ8qCWN0RSoFlRSR5FSt0ZcBbJ28FRvkYsHEtX7G8i"
-	Layers   = "WBJDrATtX6rIE5yAu8ePX3WmDF0Tt9kFiue0m3cRnyRoVx1my8a67fh3CAW486oP"
-	Net      = "CmYtj2sNB3LHtqiDuck_Lz3MjLLIiwyP8N4NDitQ1Icvv__LVP9p8tm-sHeQaKKp"
-	Promote  = "TX3eCloaQFkV-SZIH6Jg6E5WKH--rcXY1P0jnZKmLFKWrNqnOzd4G9eIBh6i5ywN"
-	Work     = "OuNiLSC68pZhAOr1YQ4WbV1tzASA0nxLEBcK7lO7MqxDY_j8dmP_C612RTuF23Lu"
+	Offline  = "IKmVhALejtYA3JhN1PCfjKF-Dio1XVcOeMWDHhfSHCbb4iBNhGjFy2UspZveZvb8"
+	OfflineS = "6ZubjSyCnz4-TKgQZi_BbY-JUwsStYCtD_f-BTDOOotfEbqkm47W20AazHRaLviz"
+	OvlRoot  = "Yox7WpG8B_OqIXWF4HWFZkUfsEl7DGzpFyZM0qtd9T8nQ-7SAkEUurlAe6_DJ6Iu"
+	Layers   = "aAwfxDB-efVo379FNl178jK7HEKU3LEjHbZdaVVjk7GnXGZGEANNsXnB3SCUxM9A"
+	Net      = "IU3GwU2jTBd7HjotvFo2wsDWBQGVGpamwiSKdc2G1EnhM-ZaacxAuK6q0wbTVxra"
+	Promote  = "rOjetGHzT_jPErrBR24IAZKDj8Q9dLLqxFQqloMgjsULss0VXDI--n6LxuMBHvmZ"
+	Work     = "7f9XDeREfvJIjCe0qesND0s0tasExAIcc-OH33-eq9tsrQPUXhJp4KEkpsYH4hCD"
 )

internal/pkg/internal/testtool/expected/sum_arm64.go

@@ -1,11 +1,11 @@
 package expected
 
 const (
-	Offline  = "WapqyoPxbWSnq07dWHt71mHaJXq99pAjJfFlELlJljSiZMhTFqqlzU1_mN86shSj"
-	OfflineS = "ibQZHcdXgNQ1OiMX1FrburBbGPVvKEHvPilbQCkm_0oV0BQCHomyyTbYNrFMGIwl"
-	OvlRoot  = "V9anFOiRvjGfAeBhLl14AL8TKdWZyD0WTPYe4fS9mOBw8iW5Lmarvt6TG6MV8uWm"
-	Layers   = "tKx7JNRoSBdK_7MdzI-nwTNV2wmiPzwYdcd17oLmXKL_iLmUzUiA79qTqdrTasrv"
-	Net      = "aXyDLzBCJ9XltXZIfetEVsEkrqHfcXuD5XE_FcUnYbN3emwL55N6P8LlHzNfGnM5"
-	Promote  = "3k4V16n96Lq04gjFSKmm4sFjyQ883FFBNXgTy9s_DjeTwxT3pg_iacEh8yMb_S4m"
-	Work     = "6Q49MhFWRE3Ne6MycwAotgl1GtoU5WCHqJNWG2byYZCY-zX-IxPrWiKk7bKkNzhE"
+	Offline  = "MTgCSzwPrzGigp9phvDPRwUTNGLm1KM2EsEtbz-l2cNieqjaGtnzm65CDXlSxXrl"
+	OfflineS = "p89bQg7_jR4nwaSbpEd08ne1jHOEw7Wlnlyv5FHq7ba1Kml3HSBZwEKRzu0gCqEb"
+	OvlRoot  = "9ifwO6MAaV9kTqRR2O5PJzm8XhfXbr50mFLWyEHQm8OHHcJtAEUgXZzJYoZt9YVV"
+	Layers   = "INuGActFPwJtS7mAR9Bkt7FD4yoHlXHSJ9CaSAQJrpkUBL_k815Cs_jvRfxy5-a7"
+	Net      = "kJvy24uk4ePvHoxSKf4vMOhR4NxLbmyWlA9bTS7d3z3fE9WF1Tvpao9g-QuYU4vm"
+	Promote  = "lYqyYrfjPawIbld5Qz0NbKvd_bmI3nJC1eEnlIQWzsjWE9uA1HuKPAaClnDeyG6L"
+	Work     = "V6k4FqOBMRCmHiqchs5-joVGZ_MhNWZyXm3gdbU0S7S5eMze7G4SwYMTf66ojKQL"
 )

internal/pkg/internal/testtool/expected/sum_riscv64.go

@@ -1,11 +1,11 @@
 package expected
 
 const (
-	Offline  = "Z6yXE5gOJScL3srmnVMWgCXccDiUNZ5snSrf6RkXuU1_U0rX_kGVwsfHUgNG_awd"
-	OfflineS = "zN16xv6LKRJRipUJwupyxg2rZcvf-qpsMn_qCxUmgxlTSuNwYI70ZEb7dHW5k0gO"
-	OvlRoot  = "zYXJHFRLuxvUhuisZEXgGgVvdQd6piMfp5jmtT6jdVjvC2gICXquOq-UTwlrSD5I"
-	Layers   = "_F8EDazHbcLeT0sVSQXRN_kn9IjduqJcDYgzXpsT-hpKU4EBcZ0PISN2zchpqMbm"
-	Net      = "CA_FAaSIYJgapBEHV40doxpH23PdUEy_6s1TZc7wfSPN0XYqwGpMceXXDSabGveO"
-	Promote  = "_3LPrLp--4h9k4GsNNApu9hHtAafq-GUhfU6d4hJKBDKT3bz_szOsvkXxc5sK53d"
-	Work     = "FEgHeiCD_WT4wsfB-9kDH5n6cRWCEYtJmXdKZgmUUukAOoXumH_hLlosXREC-tqq"
+	Offline  = "LlieSHVDe1lnKvfI8t4oGRg_2hPxwyy1drmaqc-EKCOENuS9C2YHrp2VY5pSyhbg"
+	OfflineS = "qccjM8oYjUuEYPKFFzAxDFVzMerSUKUZc18NdVQoiPWf-70XOsNK8NaUQqjTgTAD"
+	OvlRoot  = "lpV2bb_KGYFHPiOn-jtGop8K_ew0y1p3BezRp0ebM93_a-T9J-vkqGD5uokda1aN"
+	Layers   = "sM3DJm210CHPGHkAquIbrXhspB81FpVC60ApQrvJGD5El2i7cSONj7LWf7EWqKpT"
+	Net      = "JihQUwsVETRYjb2-yIXLYZ6WVsaFebwl8btSYAsNQ2QapS5MZVaI-dYwrVoySycR"
+	Promote  = "lGqwR4W2OjylSVitMQP1lc6wApOBkbMjsmIqkxQbfEZ3DHEQBbJr84ErW6Xb54zo"
+	Work     = "aZgtyv6aMtoHFkHAaJr6nLaA7N_SHjShgWPyQ5UdzaIqYSiVqvCrZqSokGTCcTii"
 )

internal/pkg/internal/testtool/main.go

@@ -38,7 +38,15 @@ func main() {
 	}
 
 	environ := slices.DeleteFunc(slices.Clone(os.Environ()), func(s string) bool {
-		return s == "CURE_JOBS="+strconv.Itoa(runtime.NumCPU())
+		for _, t := range []string{
+			"CURE_JOBS=" + strconv.Itoa(runtime.NumCPU()),
+			"CURE_LOAD=" + strconv.Itoa(runtime.NumCPU()+2),
+		} {
+			if s == t {
+				return true
+			}
+		}
+		return false
 	})
 
 	var hostNet, layers, promote bool

internal/pkg/ir.go

@@ -8,6 +8,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"iter"
 	"slices"
 	"strconv"
 	"sync"
@@ -20,7 +21,7 @@ import (
 const wordSize = 8
 
 // alignSize returns the padded size for aligning sz.
-func alignSize(sz int) int {
+func alignSize[T int | uint64](sz T) T {
 	return sz + (wordSize-(sz)%wordSize)%wordSize
 }
 
@@ -65,6 +66,18 @@ func NewIR() *IRCache {
 	return &IRCache{zeroIRCache()}
 }
 
+// Inputs returns an iterator over direct and transitive inputs of an [Artifact]
+// in randomised order.
+func Inputs(a Artifact) iter.Seq2[Artifact, unique.Handle[ID]] {
+	ic := NewIR()
+	ic.Ident(a)
+	return func(yield func(Artifact, unique.Handle[ID]) bool) {
+		ic.artifact.Range(func(key, value any) bool {
+			return yield(key.(Artifact), value.(unique.Handle[ID]))
+		})
+	}
+}
+
 // IContext is passed to [Artifact.Params] and provides methods for writing
 // values to the IR writer. It does not expose the underlying [io.Writer].
 //
@@ -77,7 +90,7 @@ type IContext struct {
 	// returns and must not be exposed directly.
 	w io.Writer
 	// Optional [Artifact] to cureRes cache, replaces [IRKindIdent] with
-	// checksum values if non-nil.
+	// checksum values if non-nil. The pathname field may not be populated.
 	inputs map[Artifact]cureRes
 }
 
@@ -160,7 +173,7 @@ func (i *IContext) mustWrite(p []byte) {
 
 // WriteIdent writes the identifier of [Artifact] to the IR. The behaviour of
 // WriteIdent is not defined for an [Artifact] not part of the slice returned by
-// [Artifact.Dependencies].
+// [Artifact.Inputs].
 func (i *IContext) WriteIdent(a Artifact) {
 	buf := i.ic.getIdentBuf()
 	defer i.ic.putIdentBuf(buf)
@@ -222,13 +235,14 @@ func (ic *irCache) Encode(w io.Writer, a Artifact) (err error) {
 }
 
 // encode implements Encode but replaces identifiers with their cured checksums
-// for a non-nil ident. Caller must acquire Cache.identMu.
+// for a non-nil ident. The pathname field is unused. Caller must acquire
+// Cache.identMu.
 func (ic *irCache) encode(
 	w io.Writer,
 	a Artifact,
 	inputs map[Artifact]cureRes,
 ) (err error) {
-	deps := a.Dependencies()
+	deps := a.Inputs()
 	idents := make([]*extIdent, len(deps))
 	if inputs == nil {
 		for i, d := range deps {
@@ -264,10 +278,11 @@ func (ic *irCache) encode(
 		return *a == *b
 	})
 
-	// kind uint64 | deps_sz uint64
-	var buf [wordSize * 2]byte
+	// kind uint64 | rev uint64 | deps_sz uint64
+	var buf [wordSize * 3]byte
 	binary.LittleEndian.PutUint64(buf[:], uint64(a.Kind()))
-	binary.LittleEndian.PutUint64(buf[wordSize:], uint64(len(idents)))
+	binary.LittleEndian.PutUint64(buf[wordSize:], GetRevision(a))
+	binary.LittleEndian.PutUint64(buf[wordSize*2:], uint64(len(idents)))
 	if _, err = w.Write(buf[:]); err != nil {
 		return
 	}
@@ -317,7 +332,7 @@ func (ic *irCache) encodeAll(
 		return
 	}
 
-	for _, d := range a.Dependencies() {
+	for _, d := range a.Inputs() {
 		if err = ic.encodeAll(w, d, encoded); err != nil {
 			return
 		}
@@ -419,9 +434,9 @@ type (
 		// Common buffer for word-sized reads.
 		buf [wordSize]byte
 
-		// Dependencies sent before params, sorted by identifier. Resliced on
+		// Inputs sent before params, sorted by identifier. Resliced on
 		// each call to Next and checked to be depleted during Finalise.
-		deps []*extIdent
+		inputs []*extIdent
 
 		// Number of values already read, -1 denotes a finalised IRReader.
 		count int
@@ -505,7 +520,7 @@ const (
 	irMaxValues = 1 << 12
 
 	// irMaxDeps is the arbitrary maximum number of direct dependencies allowed
-	// to be returned by [Artifact.Dependencies] and subsequently decoded by
+	// to be returned by [Artifact.Inputs] and subsequently decoded by
 	// [IRDecoder].
 	irMaxDeps = 1 << 10
 )
@@ -590,17 +605,17 @@ func (ir *IRReader) mustReadHeader(k IRValueKind) {
 
 // putAll returns all dependency buffers to the underlying [Cache].
 func (ir *IRReader) putAll() {
-	for _, buf := range ir.deps {
+	for _, buf := range ir.inputs {
 		ir.d.c.putIdentBuf(buf)
 	}
-	ir.deps = nil
+	ir.inputs = nil
 }
 
 // DiscardAll discards all unstructured dependencies. This is useful to
 // implementations that encode dependencies as [IRKindIdent] which are read back
 // via ReadIdent.
 func (ir *IRReader) DiscardAll() {
-	if ir.deps == nil {
+	if ir.inputs == nil {
 		panic("attempting to discard dependencies twice")
 	}
 	ir.putAll()
@@ -612,13 +627,13 @@ var ErrDependencyDepleted = errors.New("reading past end of dependencies")
 
 // Next returns the next unstructured dependency.
 func (ir *IRReader) Next() Artifact {
-	if len(ir.deps) == 0 {
+	if len(ir.inputs) == 0 {
 		panic(ErrDependencyDepleted)
 	}
 
-	id := unique.Make(ID(ir.deps[0][wordSize:]))
-	ir.d.c.putIdentBuf(ir.deps[0])
-	ir.deps = ir.deps[1:]
+	id := unique.Make(ID(ir.inputs[0][wordSize:]))
+	ir.d.c.putIdentBuf(ir.inputs[0])
+	ir.inputs = ir.inputs[1:]
 
 	if a, ok := ir.d.ident[id]; !ok {
 		ir.putAll()
@@ -671,8 +686,8 @@ func (ir *IRReader) Finalise() (checksum unique.Handle[Checksum], ok bool) {
 	}
 	ir.r, ir.ibw = nil, nil
 
-	if len(ir.deps) != 0 {
-		panic(MissedDependencyError(len(ir.deps)))
+	if len(ir.inputs) != 0 {
+		panic(MissedDependencyError(len(ir.inputs)))
 	}
 
 	return
@@ -726,6 +741,15 @@ func (ir *IRReader) ReadString() string {
 	return unsafe.String(unsafe.SliceData(p), len(p))
 }
 
+// A RevisionError describes the first [Artifact] in an IR stream claiming a
+// revision not supported by the registered implementation.
+type RevisionError [2]uint64
+
+func (e RevisionError) Error() string {
+	return "claimed revision " + strconv.FormatUint(e[0], 10) +
+		" differs from implementation value " + strconv.FormatUint(e[1], 10)
+}
+
 // decode decodes the next [Artifact] in the IR stream and returns any buffer
 // originating from [Cache] before returning. decode returns [io.EOF] if and
 // only if the underlying [io.Reader] is already read to EOF.
@@ -758,6 +782,9 @@ func (d *IRDecoder) decode() (a Artifact, err error) {
 		return
 	}
 
+	ir.mustRead(ir.buf[:])
+	rev := binary.LittleEndian.Uint64(ir.buf[:])
+
 	defer ir.putAll()
 	ir.mustRead(ir.buf[:])
 	sz := binary.LittleEndian.Uint64(ir.buf[:])
@@ -765,11 +792,11 @@ func (d *IRDecoder) decode() (a Artifact, err error) {
 		err = ErrIRDepend
 		return
 	}
-	ir.deps = make([]*extIdent, sz)
-	for i := range ir.deps {
-		ir.deps[i] = d.c.getIdentBuf()
+	ir.inputs = make([]*extIdent, sz)
+	for i := range ir.inputs {
+		ir.inputs[i] = d.c.getIdentBuf()
 	}
-	for _, buf := range ir.deps {
+	for _, buf := range ir.inputs {
 		ir.mustRead(buf[:])
 	}
 
@@ -778,6 +805,10 @@ func (d *IRDecoder) decode() (a Artifact, err error) {
 		err = syscall.ENOTRECOVERABLE
 		return
 	}
+	if _rev := GetRevision(a); _rev != rev {
+		err = RevisionError{rev, _rev}
+		return
+	}
 
 	if ir.count != -1 {
 		err = ErrRemainingIR
@@ -792,8 +823,8 @@ func (d *IRDecoder) decode() (a Artifact, err error) {
 		d.ident[id] = a
 	} else {
 		d.c.msg.Verbosef(
-			"artifact %s appeared more than once in IR stream",
-			Encode(id.Value()),
+			"artifact %s%s%s appeared more than once in IR stream",
+			d.c.sgrIdent, Encode(id.Value()), d.c.sgrRes,
 		)
 	}
 

internal/pkg/ir_test.go

@@ -27,16 +27,14 @@ func TestIRRoundtrip(t *testing.T) {
 			pkg.Checksum(bytes.Repeat([]byte{0xfc}, len(pkg.Checksum{}))),
 		)},
 
-		{"http get tar", pkg.NewHTTPGetTar(
+		{"http get tar", pkg.NewTar(pkg.NewDecompress(pkg.NewHTTPGet(
 			nil, "file:///testdata",
 			pkg.Checksum(bytes.Repeat([]byte{0xff}, len(pkg.Checksum{}))),
-			pkg.TarBzip2,
-		)},
-		{"http get tar unaligned", pkg.NewHTTPGetTar(
+		), pkg.Bzip2))},
+		{"http get tar unaligned", pkg.NewTar(pkg.NewHTTPGet(
 			nil, "https://hakurei.app",
 			pkg.Checksum(bytes.Repeat([]byte{0xfe}, len(pkg.Checksum{}))),
-			pkg.TarUncompressed,
-		)},
+		))},
 
 		{"exec offline", pkg.NewExec(
 			"exec-offline", "", nil, 0, false, false,
@@ -47,15 +45,13 @@ func TestIRRoundtrip(t *testing.T) {
 
 			pkg.MustPath("/file", false, pkg.NewFile("file", []byte(
 				"stub file",
-			))), pkg.MustPath("/.hakurei", false, pkg.NewHTTPGetTar(
+			))), pkg.MustPath("/.hakurei", false, pkg.NewTar(pkg.NewHTTPGet(
 				nil, "file:///hakurei.tar",
 				pkg.Checksum(bytes.Repeat([]byte{0xfc}, len(pkg.Checksum{}))),
-				pkg.TarUncompressed,
-			)), pkg.MustPath("/opt", false, pkg.NewHTTPGetTar(
+			))), pkg.MustPath("/opt", false, pkg.NewTar(pkg.NewDecompress(pkg.NewHTTPGet(
 				nil, "file:///testtool.tar.gz",
 				pkg.Checksum(bytes.Repeat([]byte{0xfc}, len(pkg.Checksum{}))),
-				pkg.TarGzip,
-			)),
+			), pkg.Gzip))),
 		)},
 
 		{"exec net", pkg.NewExec(
@@ -69,15 +65,13 @@ func TestIRRoundtrip(t *testing.T) {
 
 			pkg.MustPath("/file", false, pkg.NewFile("file", []byte(
 				"stub file",
-			))), pkg.MustPath("/.hakurei", false, pkg.NewHTTPGetTar(
+			))), pkg.MustPath("/.hakurei", false, pkg.NewTar(pkg.NewHTTPGet(
 				nil, "file:///hakurei.tar",
 				pkg.Checksum(bytes.Repeat([]byte{0xfc}, len(pkg.Checksum{}))),
-				pkg.TarUncompressed,
-			)), pkg.MustPath("/opt", false, pkg.NewHTTPGetTar(
+			))), pkg.MustPath("/opt", false, pkg.NewTar(pkg.NewDecompress(pkg.NewHTTPGet(
 				nil, "file:///testtool.tar.gz",
 				pkg.Checksum(bytes.Repeat([]byte{0xfc}, len(pkg.Checksum{}))),
-				pkg.TarGzip,
-			)),
+			), pkg.Gzip))),
 		)},
 
 		{"exec measured", pkg.NewExec(
@@ -91,19 +85,21 @@ func TestIRRoundtrip(t *testing.T) {
 
 			pkg.MustPath("/file", false, pkg.NewFile("file", []byte(
 				"stub file",
-			))), pkg.MustPath("/.hakurei", false, pkg.NewHTTPGetTar(
+			))), pkg.MustPath("/.hakurei", false, pkg.NewTar(pkg.NewHTTPGet(
 				nil, "file:///hakurei.tar",
 				pkg.Checksum(bytes.Repeat([]byte{0xfd}, len(pkg.Checksum{}))),
-				pkg.TarUncompressed,
-			)), pkg.MustPath("/opt", false, pkg.NewHTTPGetTar(
+			))), pkg.MustPath("/opt", false, pkg.NewTar(pkg.NewDecompress(pkg.NewHTTPGet(
 				nil, "file:///testtool.tar.gz",
 				pkg.Checksum(bytes.Repeat([]byte{0xfd}, len(pkg.Checksum{}))),
-				pkg.TarGzip,
-			)),
+			), pkg.Gzip))),
 		)},
 
 		{"file anonymous", pkg.NewFile("", []byte{0})},
 		{"file", pkg.NewFile("stub", []byte("stub"))},
+
+		{"decompress", pkg.NewDecompress(pkg.NewFile("", []byte{0}), pkg.Bzip2)},
+
+		{"archive", pkg.NewArchive(pkg.NewFile("", []byte{0}))},
 	}
 	testCasesCache := make([]cacheTestCase, len(testCases))
 	for i, tc := range testCases {
@@ -139,3 +135,36 @@ func TestIRRoundtrip(t *testing.T) {
 	}
 	checkWithCache(t, testCasesCache)
 }
+
+func TestRevision(t *testing.T) {
+	checkWithCache(t, []cacheTestCase{{"revision", 0, nil,
+		func(t *testing.T, base *check.Absolute, c *pkg.Cache) {
+			a := pkg.NewFile("", nil)
+			var buf bytes.Buffer
+			if err := c.EncodeAll(&buf, a); err != nil {
+				t.Fatal(err)
+			}
+
+			if _, err := c.NewDecoder(
+				bytes.NewReader(buf.Bytes()),
+			).Decode(); err != nil {
+				t.Fatalf("Decode: error = %v", err)
+			}
+
+			p := buf.Bytes()
+			p[8] = 0xfd
+			wantErr := pkg.RevisionError{0xfd, 0}
+			if _, err := c.NewDecoder(
+				bytes.NewReader(p),
+			).Decode(); !reflect.DeepEqual(err, wantErr) {
+				t.Fatalf("Decode: error = %v, want %v", err, wantErr)
+			}
+		}, expectsFS{
+			".":          {Mode: fs.ModeDir | 0700},
+			"checksum":   {Mode: fs.ModeDir | 0700},
+			"identifier": {Mode: fs.ModeDir | 0700},
+			"substitute": {Mode: fs.ModeDir | 0700},
+			"work":       {Mode: fs.ModeDir | 0700},
+		},
+	}})
+}

internal/pkg/net.go

@@ -54,8 +54,8 @@ func init() {
 	})
 }
 
-// Dependencies returns a nil slice.
-func (*httpArtifact) Dependencies() []Artifact { return nil }
+// Inputs returns a nil slice.
+func (*httpArtifact) Inputs() []Artifact { return nil }
 
 // IsExclusive returns false: Cure returns as soon as a response is received.
 func (*httpArtifact) IsExclusive() bool { return false }
@@ -74,6 +74,9 @@ func (e ResponseStatusError) Error() string {
 	return "the requested URL returned non-OK status: " + http.StatusText(int(e))
 }
 
+// IsExecutable returns false.
+func (*httpArtifact) IsExecutable() bool { return false }
+
 // Cure sends the http request and returns the resulting response body reader
 // wrapped to perform checksum validation. It is valid but not encouraged to
 // close the resulting [io.ReadCloser] before it is read to EOF, as that causes

internal/pkg/net_test.go

@@ -104,7 +104,7 @@ func TestHTTPGet(t *testing.T) {
 			)
 			wantPathname := base.Append(
 				"identifier",
-				"oM-2pUlk-mOxK1t3aMWZer69UdOQlAXiAgMrpZ1476VoOqpYVP1aGFS9_HYy-D8_",
+				"COBRUwkxpIvZWJggpRxn7HVXiw6epXZOex8jGRJKpowpwukV7GRBY_LBvOJNQHue",
 			)
 			if pathname, checksum, err := c.Cure(f); err != nil {
 				t.Fatalf("Cure: error = %v", err)
@@ -158,7 +158,7 @@ func TestHTTPGet(t *testing.T) {
 			"checksum/fLYGIMHgN1louE-JzITJZJo2SDniPu-IHBXubtvQWFO-hXnDVKNuscV7-zlyr5fU": {Mode: 0400, Data: []byte("\x7f\xe1\x69\xa2\xdd\x63\x96\x26\x83\x79\x61\x8b\xf0\x3f\xd5\x16\x9a\x39\x3a\xdb\xcf\xb1\xbc\x8d\x33\xff\x75\xee\x62\x56\xa9\xf0\x27\xac\x13\x94\x69")},
 
 			"identifier": {Mode: fs.ModeDir | 0700},
-			"identifier/oM-2pUlk-mOxK1t3aMWZer69UdOQlAXiAgMrpZ1476VoOqpYVP1aGFS9_HYy-D8_": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/fLYGIMHgN1louE-JzITJZJo2SDniPu-IHBXubtvQWFO-hXnDVKNuscV7-zlyr5fU")},
+			"identifier/COBRUwkxpIvZWJggpRxn7HVXiw6epXZOex8jGRJKpowpwukV7GRBY_LBvOJNQHue": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/fLYGIMHgN1louE-JzITJZJo2SDniPu-IHBXubtvQWFO-hXnDVKNuscV7-zlyr5fU")},
 
 			"substitute": {Mode: fs.ModeDir | 0700},
 

internal/pkg/tar.go

@@ -2,34 +2,22 @@ package pkg
 
 import (
 	"archive/tar"
-	"compress/bzip2"
-	"compress/gzip"
 	"errors"
 	"fmt"
 	"io"
 	"io/fs"
-	"net/http"
 	"os"
 	"path/filepath"
 )
 
-const (
-	// TarUncompressed denotes an uncompressed tarball.
-	TarUncompressed = iota
-	// TarGzip denotes a tarball compressed via [gzip].
-	TarGzip
-	// TarBzip2 denotes a tarball compressed via [bzip2].
-	TarBzip2
-)
-
 // A tarArtifact is an [Artifact] unpacking a tarball backed by a [FileArtifact].
 type tarArtifact struct {
 	// Caller-supplied backing tarball.
 	f Artifact
-	// Compression on top of the tarball.
-	compression uint32
 }
 
+var _ CuresExempt = new(tarArtifact)
+
 // tarArtifactNamed embeds tarArtifact for a [fmt.Stringer] tarball.
 type tarArtifactNamed struct {
 	tarArtifact
@@ -39,13 +27,13 @@ type tarArtifactNamed struct {
 
 var _ fmt.Stringer = new(tarArtifactNamed)
 
-// String returns the name of the underlying [Artifact] suffixed with unpack.
-func (a *tarArtifactNamed) String() string { return a.name + "-unpack" }
+// String returns the name of the underlying [Artifact] prefixed with unpack.
+func (a *tarArtifactNamed) String() string { return "unpack-" + a.name }
 
-// NewTar returns a new [Artifact] backed by the supplied [Artifact] and
-// compression method. The source [Artifact] must be a [FileArtifact].
-func NewTar(a Artifact, compression uint32) Artifact {
-	ta := tarArtifact{a, compression}
+// NewTar returns a new [Artifact] unpacking the tar stream produced by the
+// backing [Artifact]. The source [Artifact] must be a [FileArtifact].
+func NewTar(a Artifact) Artifact {
+	ta := tarArtifact{a}
 	if s, ok := a.(fmt.Stringer); ok {
 		if name := s.String(); name != "" {
 			return &tarArtifactNamed{ta, name}
@@ -54,25 +42,15 @@ func NewTar(a Artifact, compression uint32) Artifact {
 	return &ta
 }
 
-// NewHTTPGetTar is abbreviation for NewHTTPGet passed to NewTar.
-func NewHTTPGetTar(
-	hc *http.Client,
-	url string,
-	checksum Checksum,
-	compression uint32,
-) Artifact {
-	return NewTar(NewHTTPGet(hc, url, checksum), compression)
-}
-
 // Kind returns the hardcoded [Kind] constant.
 func (a *tarArtifact) Kind() Kind { return KindTar }
 
-// Params writes compression encoded in little endian.
-func (a *tarArtifact) Params(ctx *IContext) { ctx.WriteUint32(a.compression) }
+// Params is a noop.
+func (a *tarArtifact) Params(*IContext) {}
 
 func init() {
 	register(KindTar, func(r *IRReader) Artifact {
-		a := NewTar(r.Next(), r.ReadUint32())
+		a := NewTar(r.Next())
 		if _, ok := r.Finalise(); ok {
 			panic(ErrUnexpectedChecksum)
 		}
@@ -80,8 +58,8 @@ func init() {
 	})
 }
 
-// Dependencies returns a slice containing the backing file.
-func (a *tarArtifact) Dependencies() []Artifact {
+// Inputs returns a slice containing the backing file.
+func (a *tarArtifact) Inputs() []Artifact {
 	return []Artifact{a.f}
 }
 
@@ -98,42 +76,17 @@ func (e DisallowedTypeflagError) Error() string {
 
 // Cure cures the [Artifact], producing a directory located at work.
 func (a *tarArtifact) Cure(t *TContext) (err error) {
-	var tr io.ReadCloser
-	if tr, err = t.Open(a.f); err != nil {
+	var r io.ReadCloser
+	if r, err = t.Open(a.f); err != nil {
 		return
 	}
 
-	defer func(f io.ReadCloser) {
-		if err == nil {
-			err = tr.Close()
-		}
-
-		closeErr := f.Close()
+	defer func() {
+		closeErr := r.Close()
 		if err == nil {
 			err = closeErr
 		}
-	}(tr)
-	br := t.cache.getReader(tr)
-	defer t.cache.putReader(br)
-	tr = io.NopCloser(br)
-
-	switch a.compression {
-	case TarUncompressed:
-		break
-
-	case TarGzip:
-		if tr, err = gzip.NewReader(tr); err != nil {
-			return
-		}
-		break
-
-	case TarBzip2:
-		tr = io.NopCloser(bzip2.NewReader(tr))
-		break
-
-	default:
-		return os.ErrInvalid
-	}
+	}()
 
 	type dirTargetPerm struct {
 		path string
@@ -156,8 +109,8 @@ func (a *tarArtifact) Cure(t *TContext) (err error) {
 	}()
 
 	var header *tar.Header
-	r := tar.NewReader(tr)
-	for header, err = r.Next(); err == nil; header, err = r.Next() {
+	tr := tar.NewReader(r)
+	for header, err = tr.Next(); err == nil; header, err = tr.Next() {
 		typeflag := header.Typeflag
 		if typeflag == 0 {
 			if len(header.Name) > 0 && header.Name[len(header.Name)-1] == '/' {
@@ -183,7 +136,7 @@ func (a *tarArtifact) Cure(t *TContext) (err error) {
 			); err != nil {
 				return
 			}
-			if _, err = io.Copy(f, r); err != nil {
+			if _, err = io.Copy(f, tr); err != nil {
 				_ = f.Close()
 				return
 			} else if err = f.Close(); err != nil {
@@ -219,6 +172,13 @@ func (a *tarArtifact) Cure(t *TContext) (err error) {
 			}
 			break
 
+		case tar.TypeChar:
+			t.GetMessage().Verbosef(
+				"%sskipping character device %d, %d %q%s",
+				t.cache.sgrWarn, header.Devmajor, header.Devminor, header.Name, t.cache.sgrRes,
+			)
+			continue
+
 		case tar.TypeXGlobalHeader:
 			continue // ignore
 
@@ -260,3 +220,7 @@ func (a *tarArtifact) Cure(t *TContext) (err error) {
 	}
 	return
 }
+
+// CuresExempt exempts the cheap [KindTar] implementation often at the end of a
+// [FileArtifact] pipeline.
+func (*tarArtifact) CuresExempt() {}

internal/pkg/tar_test.go

@@ -3,7 +3,6 @@ package pkg_test
 import (
 	"archive/tar"
 	"bytes"
-	"compress/gzip"
 	"crypto/sha512"
 	"errors"
 	"io/fs"
@@ -80,8 +79,8 @@ func TestTar(t *testing.T) {
 			"checksum/" + wantEncode + "/work": {Mode: fs.ModeDir | 0500},
 
 			"identifier": {Mode: fs.ModeDir | 0700},
-			"identifier/W5S65DEhawz_WKaok5NjUKLmnD9dNl5RPauNJjcOVcB3VM4eGhSaLGmXbL8vZpiw": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/" + wantEncode)},
-			"identifier/rg7F1D5hwv6o4xctjD5zDq4i5MD0mArTsUIWfhUbik8xC6Bsyt3mjXXOm3goojTz": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/" + wantEncode)},
+			"identifier/snWp53xxNdx6cV5KSJqzyVWzLlTsFd8udOisIu8Rgxly09mGcxufYCoQ5CQrHDyZ": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/" + wantEncode)},
+			"identifier/v9DUj2R4YK_3ae0m9VuUYI-HJysDDCENu1k10thxioycRzFH1Qejw5bBGukm4IdL": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/" + wantEncode)},
 
 			"substitute": {Mode: fs.ModeDir | 0700},
 
@@ -104,8 +103,8 @@ func TestTar(t *testing.T) {
 			"checksum/" + wantExpandEncode + "/libedac.so": {Mode: fs.ModeSymlink | 0777, Data: []byte("/proc/nonexistent/libedac.so")},
 
 			"identifier": {Mode: fs.ModeDir | 0700},
-			"identifier/W5S65DEhawz_WKaok5NjUKLmnD9dNl5RPauNJjcOVcB3VM4eGhSaLGmXbL8vZpiw": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/" + wantExpandEncode)},
-			"identifier/_v1blm2h-_KA-dVaawdpLas6MjHc6rbhhFS8JWwx8iJxZGUu8EBbRrhr5AaZ9PJL": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/" + wantExpandEncode)},
+			"identifier/1SuvgGltcsgqps9tWqjULG8RCdpx_6KVWXdsMd5xPKvdtysOxqpE-3bLu4j0WpGk": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/" + wantExpandEncode)},
+			"identifier/snWp53xxNdx6cV5KSJqzyVWzLlTsFd8udOisIu8Rgxly09mGcxufYCoQ5CQrHDyZ": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/" + wantExpandEncode)},
 
 			"substitute": {Mode: fs.ModeDir | 0700},
 
@@ -132,16 +131,7 @@ func checkTarHTTP(
 		if err := w.Close(); err != nil {
 			t.Fatalf("Close: error = %v", err)
 		}
-
-		var zbuf bytes.Buffer
-		gw := gzip.NewWriter(&zbuf)
-		if _, err := gw.Write(buf.Bytes()); err != nil {
-			t.Fatalf("Write: error = %v", err)
-		}
-		if err := gw.Close(); err != nil {
-			t.Fatalf("Close: error = %v", err)
-		}
-		testdata = zbuf.String()
+		testdata = buf.String()
 	}
 
 	testdataChecksum := func() pkg.Checksum {
@@ -156,49 +146,6 @@ func checkTarHTTP(
 		"testdata": {Data: []byte(testdata), Mode: 0400},
 	}))
 
-	wantIdent := func() pkg.ID {
-		h := sha512.New384()
-
-		// kind uint64
-		h.Write([]byte{byte(pkg.KindTar), 0, 0, 0, 0, 0, 0, 0})
-		// deps_sz uint64
-		h.Write([]byte{1, 0, 0, 0, 0, 0, 0, 0})
-
-		// kind uint64
-		h.Write([]byte{byte(pkg.KindHTTPGet), 0, 0, 0, 0, 0, 0, 0})
-		// ident ID
-		h0 := sha512.New384()
-		// kind uint64
-		h0.Write([]byte{byte(pkg.KindHTTPGet), 0, 0, 0, 0, 0, 0, 0})
-		// deps_sz uint64
-		h0.Write([]byte{0, 0, 0, 0, 0, 0, 0, 0})
-		// url string
-		h0.Write([]byte{byte(pkg.IRKindString), 0, 0, 0})
-		h0.Write([]byte{0x10, 0, 0, 0})
-		h0.Write([]byte("file:///testdata"))
-		// end(KnownChecksum)
-		h0.Write([]byte{byte(pkg.IRKindEnd), 0, 0, 0})
-		h0.Write([]byte{byte(pkg.IREndKnownChecksum), 0, 0, 0})
-		// checksum Checksum
-		h0.Write(testdataChecksum[:])
-		h.Write(h0.Sum(nil))
-		// compression uint32
-		h.Write([]byte{byte(pkg.IRKindUint32), 0, 0, 0})
-		h.Write([]byte{pkg.TarGzip, 0, 0, 0})
-		// end
-		h.Write([]byte{byte(pkg.IRKindEnd), 0, 0, 0})
-		h.Write([]byte{0, 0, 0, 0})
-
-		return pkg.ID(h.Sum(nil))
-	}()
-
-	a := pkg.NewHTTPGetTar(
-		&client,
-		"file:///testdata",
-		testdataChecksum,
-		pkg.TarGzip,
-	)
-
 	tarDir := stubArtifact{
 		kind:   pkg.KindExec,
 		params: []byte("directory containing a single regular file"),
@@ -251,27 +198,19 @@ func checkTarHTTP(
 	defer newDestroyArtifactFunc(&tarDirType)(t, base, c)
 
 	cureMany(t, c, []cureStep{
-		{"file", a, base.Append(
-			"identifier",
-			pkg.Encode(wantIdent),
-		), want, nil},
+		{"file", pkg.NewTar(pkg.NewHTTPGet(
+			&client,
+			"file:///testdata",
+			testdataChecksum,
+		)), ignorePathname, want, pkg.WNew, nil},
 
-		{"directory", pkg.NewTar(
-			&tarDir,
-			pkg.TarGzip,
-		), ignorePathname, want, nil},
+		{"directory", pkg.NewTar(&tarDir), ignorePathname, want, pkg.WNew, nil},
 
-		{"multiple entries", pkg.NewTar(
-			&tarDirMulti,
-			pkg.TarGzip,
-		), nil, nil, errors.New(
+		{"multiple entries", pkg.NewTar(&tarDirMulti), nil, nil, pkg.WNew, errors.New(
 			"input directory does not contain a single regular file",
 		)},
 
-		{"bad type", pkg.NewTar(
-			&tarDirType,
-			pkg.TarGzip,
-		), nil, nil, errors.New(
+		{"bad type", pkg.NewTar(&tarDirType), nil, nil, pkg.WNew, errors.New(
 			"input directory does not contain a single regular file",
 		)},
 
@@ -281,6 +220,6 @@ func checkTarHTTP(
 			cure: func(t *pkg.TContext) error {
 				return stub.UniqueError(0xcafe)
 			},
-		}, pkg.TarGzip), nil, nil, stub.UniqueError(0xcafe)},
+		}), nil, nil, pkg.WNew, stub.UniqueError(0xcafe)},
 	})
 }

internal/report/report.go

@@ -15,8 +15,10 @@ import (
 )
 
 const (
+	// Trivial denotes an error that may happen frequently under normal operation.
+	Trivial = iota
 	// Inconsistent denotes an error diagnosed due to inconsistent state.
-	Inconsistent = iota
+	Inconsistent
 	// Degraded denotes an error condition causing a degraded state.
 	Degraded
 	// Fatal denotes an unrecoverable error. This is generally followed by
@@ -88,6 +90,8 @@ func (e Error) MarshalJSON() (data []byte, err error) {
 	}{Message: e.Message}
 
 	switch e.Severity {
+	case Trivial:
+		v.Severity = "trivial"
 	case Inconsistent:
 		v.Severity = "inconsistent"
 	case Degraded:
@@ -98,8 +102,7 @@ func (e Error) MarshalJSON() (data []byte, err error) {
 		v.Severity = e.Severity
 	}
 
-	var re RepresentableError
-	if errors.As(e.Err, &re) {
+	if re, ok := errors.AsType[RepresentableError](e.Err); ok {
 		v.Err, err = json.Marshal(re)
 	} else {
 		v.Err, err = json.Marshal(e.Err.Error())
@@ -162,11 +165,11 @@ func (r *Reporter) dispatch(severity int, message string, e error) (err error) {
 			err = _err
 		}
 		r.mu.Unlock()
-	} else if flag&DBypassEarly == 0 {
+	} else if flag&DBypassEarly == 0 && severity != Trivial {
 		panic(p)
 	}
 
-	if flag&DStrict != 0 {
+	if flag&DStrict != 0 && severity != Trivial {
 		panic(p)
 	}