Symlinks

dependencies.go

@@ -1,6 +1,6 @@
 //go:build tools
 
-package vmtest
+package mkuimage
 
 // List u-root commands that need to be in go.mod & go.sum to be buildable as
 // dependencies. This way, they aren't eliminated by `go mod tidy`.

uimage/uimage.go

@@ -176,6 +176,11 @@ type Opts struct {
 	//   - "/home/foo" is equivalent to "/home/foo:home/foo".
 	ExtraFiles []string
 
+	// Symlinks to create in the archive. File path in archive -> target
+	//
+	// Target can be the name of a command. If not, it will be created as given.
+	Symlinks map[string]string
+
 	// If true, do not use ldd to pick up dependencies from local machine for
 	// ExtraFiles. Useful if you have all deps revision controlled and wish to
 	// ensure builds are repeatable, and/or if the local machine's binaries use
@@ -293,6 +298,22 @@ func WithEnv(gopts ...golang.Opt) Modifier {
 	}
 }
 
+// WithSymlink adds a symlink to the archive.
+//
+// Target can be the name of a command. If not, it will be created as given.
+func WithSymlink(file string, target string) Modifier {
+	return func(o *Opts) error {
+		if o.Symlinks == nil {
+			o.Symlinks = make(map[string]string)
+		}
+		if other, ok := o.Symlinks[file]; ok {
+			return fmt.Errorf("%w: cannot add symlink for %q as %q, already points to %q", os.ErrExist, file, target, other)
+		}
+		o.Symlinks[file] = target
+		return nil
+	}
+}
+
 // WithFiles adds files to the archive.
 //
 // Shared library dependencies will automatically also be added to the archive
@@ -563,6 +584,15 @@ func CreateInitramfs(l *llog.Logger, opts Opts) error {
 	if err := opts.addSymlinkTo(l, archive, opts.DefaultShell, "bin/defaultsh"); err != nil {
 		return fmt.Errorf("%w: %w", err, errDefaultshSymlink)
 	}
+	for p, target := range opts.Symlinks {
+		p = path.Clean(p)
+		if len(p) >= 1 && p[0] == '/' {
+			p = p[1:]
+		}
+		if err := opts.addSymlinkTo(l, archive, target, p); err != nil {
+			return fmt.Errorf("%w: could not add additional symlink", err)
+		}
+	}
 
 	// Finally, write the archive.
 	if err := initramfs.Write(archive); err != nil {

uimage/uimage_test.go

@@ -459,6 +459,52 @@ func TestCreateInitramfs(t *testing.T) {
 			},
 			errs: []error{initramfs.ErrNoPath},
 		},
+		{
+			name: "symlinks",
+			opts: Opts{
+				Env:          golang.Default(golang.DisableCGO()),
+				TempDir:      dir,
+				InitCmd:      "init",
+				DefaultShell: "ls",
+				Symlinks: map[string]string{
+					"ubin/foo":  "ls",
+					"ubin/fooa": "/bin/systemd",
+				},
+				Commands: BusyboxCmds(
+					"github.com/u-root/u-root/cmds/core/init",
+					"github.com/u-root/u-root/cmds/core/ls",
+				),
+			},
+			validators: []itest.ArchiveValidator{
+				itest.HasFile{Path: "bbin/bb"},
+				itest.HasRecord{R: cpio.Symlink("bbin/init", "bb")},
+				itest.HasRecord{R: cpio.Symlink("bbin/ls", "bb")},
+				itest.HasRecord{R: cpio.Symlink("bin/defaultsh", "../bbin/ls")},
+				itest.HasRecord{R: cpio.Symlink("bin/sh", "../bbin/ls")},
+				itest.HasRecord{R: cpio.Symlink("ubin/foo", "../bbin/ls")},
+				itest.HasRecord{R: cpio.Symlink("ubin/fooa", "../bin/systemd")},
+			},
+		},
+		{
+			name: "dup symlinks",
+			opts: Opts{
+				Env:          golang.Default(golang.DisableCGO()),
+				TempDir:      dir,
+				InitCmd:      "init",
+				DefaultShell: "ls",
+				Symlinks: map[string]string{
+					"/bbin/ls": "init",
+				},
+				Commands: BusyboxCmds(
+					"github.com/u-root/u-root/cmds/core/init",
+					"github.com/u-root/u-root/cmds/core/ls",
+				),
+			},
+			errs: []error{os.ErrExist},
+			validators: []itest.ArchiveValidator{
+				itest.IsEmpty{},
+			},
+		},
 	} {
 		t.Run(fmt.Sprintf("Test %d [%s]", i, tt.name), func(t *testing.T) {
 			archive := cpio.InMemArchive()
@@ -892,6 +938,60 @@ func TestCreateInitramfsWithAPI(t *testing.T) {
 				itest.HasContent{Path: "etc/foo", Content: "bar"},
 			},
 		},
+		{
+			name: "symlinks",
+			opts: []Modifier{
+				WithTempDir(dir),
+				WithEnv(golang.DisableCGO()),
+				WithInit("init"),
+				WithShell("ls"),
+				WithBusyboxCommands(
+					"github.com/u-root/u-root/cmds/core/init",
+					"github.com/u-root/u-root/cmds/core/ls",
+				),
+				WithSymlink("ubin/foo", "ls"),
+				WithSymlink("ubin/fooa", "/bin/systemd"),
+			},
+			validators: []itest.ArchiveValidator{
+				itest.HasFile{Path: "bbin/bb"},
+				itest.HasRecord{R: cpio.Symlink("bbin/init", "bb")},
+				itest.HasRecord{R: cpio.Symlink("bbin/ls", "bb")},
+				itest.HasRecord{R: cpio.Symlink("bin/defaultsh", "../bbin/ls")},
+				itest.HasRecord{R: cpio.Symlink("bin/sh", "../bbin/ls")},
+				itest.HasRecord{R: cpio.Symlink("ubin/foo", "../bbin/ls")},
+				itest.HasRecord{R: cpio.Symlink("ubin/fooa", "../bin/systemd")},
+			},
+		},
+		{
+			name: "dup symlinks",
+			opts: []Modifier{
+				WithTempDir(dir),
+				WithEnv(golang.DisableCGO()),
+				WithInit("init"),
+				WithShell("ls"),
+				WithBusyboxCommands(
+					"github.com/u-root/u-root/cmds/core/init",
+					"github.com/u-root/u-root/cmds/core/ls",
+				),
+				WithSymlink("/bbin/ls", "init"),
+			},
+			errs: []error{os.ErrExist},
+			validators: []itest.ArchiveValidator{
+				itest.IsEmpty{},
+			},
+		},
+		{
+			name: "dup with symlinks",
+			opts: []Modifier{
+				WithTempDir(dir),
+				WithSymlink("ubin/ls", "/bin/foo"),
+				WithSymlink("ubin/ls", "../bbin/ls"),
+			},
+			errs: []error{os.ErrExist},
+			validators: []itest.ArchiveValidator{
+				itest.IsEmpty{},
+			},
+		},
 	} {
 		t.Run(fmt.Sprintf("Test %d [%s]", i, tt.name), func(t *testing.T) {
 			archive := cpio.InMemArchive()