container/inittmpfs: unwrap out of bounds error

This eliminates generic WrapErr from tmpfs.

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

container/errors.go

@@ -24,6 +24,10 @@ func messageFromError(err error) (string, bool) {
 		return m, ok
 	}
 
+	if m, ok := messagePrefix[TmpfsSizeError]("", err); ok {
+		return m, ok
+	}
+
 	return zeroString, false
 }
 

container/errors_test.go

@@ -39,6 +39,9 @@ func TestMessageFromError(t *testing.T) {
 		{"state", OpStateError("overlay"),
 			"impossible overlay state reached", true},
 
+		{"tmpfs", TmpfsSizeError(-1),
+			"tmpfs size -1 out of bounds", true},
+
 		{"unsupported", errUnique, zeroString, false},
 	}
 	for _, tc := range testCases {

container/inittmpfs.go

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

container/inittmpfs_test.go

@@ -1,17 +1,24 @@
 package container
 
 import (
-	"io/fs"
 	"os"
 	"syscall"
 	"testing"
 )
 
 func TestMountTmpfsOp(t *testing.T) {
+	t.Run("size error", func(t *testing.T) {
+		tmpfsSizeError := TmpfsSizeError(-1)
+		want := "tmpfs size -1 out of bounds"
+		if got := tmpfsSizeError.Error(); got != want {
+			t.Errorf("Error: %q, want %q", got, want)
+		}
+	})
+
 	checkOpBehaviour(t, []opBehaviourTestCase{
 		{"size oob", new(Params), &MountTmpfsOp{
 			Size: -1,
-		}, nil, nil, nil, msg.WrapErr(fs.ErrInvalid, "size -1 out of bounds")},
+		}, nil, nil, nil, TmpfsSizeError(-1)},
 
 		{"success", new(Params), &MountTmpfsOp{
 			FSName: "ephemeral",