Add symlinks tree for compatibity with older firmware

A lot of firmware binaries use non-standard paths like `/lib`. Add
the tree of symlinks for compatibility.

Closes #45
Closes #104

generator/generator.go

@@ -8,6 +8,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/cavaliercoder/go-cpio"
 	"gopkg.in/yaml.v3"
 )
 
@@ -93,6 +94,10 @@ func generateInitRamfs(conf *generatorConfig) error {
 	}
 	defer img.Cleanup()
 
+	if err := appendCompatibilitySymlinks(img); err != nil {
+		return err
+	}
+
 	if err := img.appendInitBinary(conf.initBinary); err != nil {
 		return err
 	}
@@ -163,6 +168,30 @@ func generateInitRamfs(conf *generatorConfig) error {
 	return img.Close()
 }
 
+// appendCompatibilitySymlinks appends symlinks for compatibility with older firmware that loads extra files from non-standard locations
+func appendCompatibilitySymlinks(img *Image) error {
+	symlinks := []struct{ src, target string }{
+		{"/lib", "/usr/lib"},
+		{"/usr/local/lib", "/usr/lib"},
+		{"/usr/sbin", "/usr/bin"},
+		{"/bin", "/usr/bin"},
+		{"/sbin", "/usr/bin"},
+		{"/usr/local/bin", "/usr/bin"},
+		{"/usr/local/sbin", "/usr/bin"},
+		{"/var/run", "/run"},
+		{"/usr/lib64", "/usr/lib"},
+		{"/lib64", "/usr/lib"},
+	}
+
+	for _, l := range symlinks {
+		mode := cpio.FileMode(0777) | cpio.ModeSymlink
+		if err := img.AppendEntry(l.src, mode, []byte(l.target)); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 func (img *Image) appendInitBinary(initBinary string) error {
 	content, err := os.ReadFile(initBinary)
 	if err != nil {

generator/image.go

@@ -150,7 +150,7 @@ func stripElf(name string, in []byte, stripAll bool) ([]byte, error) {
 	return os.ReadFile(t.Name())
 }
 
-func (img *Image) AppendContent(content []byte, mode os.FileMode, dest string) error {
+func (img *Image) AppendContent(content []byte, osMode os.FileMode, dest string) error {
 	img.m.Lock()
 	if img.contains[dest] {
 		img.m.Unlock()
@@ -197,19 +197,8 @@ func (img *Image) AppendContent(content []byte, mode os.FileMode, dest string) e
 		}
 	}
 
-	hdr := &cpio.Header{
-		Name: strings.TrimPrefix(dest, "/"),
-		Mode: cpio.FileMode(mode) | cpio.ModeRegular,
-		Size: int64(len(content)),
-	}
-	img.m.Lock()
-	if err := img.out.WriteHeader(hdr); err != nil {
-		img.m.Unlock()
-		return err
-	}
-	_, err := img.out.Write(content)
-	img.m.Unlock()
-	return err
+	mode := cpio.FileMode(osMode) | cpio.ModeRegular
+	return img.AppendEntry(dest, mode, content)
 }
 
 // AppendFile appends the file + its dependencies to the ramfs file
@@ -248,22 +237,10 @@ func (img *Image) AppendFile(fn string) error {
 			return err
 		}
 
-		hdr := &cpio.Header{
-			Name: strings.TrimPrefix(fn, "/"),
-			Mode: cpio.FileMode(fi.Mode().Perm()) | cpio.ModeSymlink,
-			Size: int64(len(linkTarget)),
-		}
-
-		img.m.Lock()
-		if err := img.out.WriteHeader(hdr); err != nil {
-			img.m.Unlock()
-			return err
-		}
-		if _, err := img.out.Write([]byte(linkTarget)); err != nil {
-			img.m.Unlock()
+		mode := cpio.FileMode(fi.Mode().Perm()) | cpio.ModeSymlink
+		if err := img.AppendEntry(fn, mode, []byte(linkTarget)); err != nil {
 			return err
 		}
-		img.m.Unlock()
 
 		// now add the link target as well
 		if !filepath.IsAbs(linkTarget) {
@@ -301,6 +278,36 @@ func (img *Image) AppendFile(fn string) error {
 	return nil
 }
 
+// AppendEntry appends an entry to the archive
+func (img *Image) AppendEntry(dest string, fileMode cpio.FileMode, content []byte) error {
+	img.m.Lock()
+	img.contains[dest] = true
+	img.m.Unlock()
+
+	if err := img.AppendDirEntry(path.Dir(dest)); err != nil {
+		return err
+	}
+
+	hdr := &cpio.Header{
+		Name: strings.TrimPrefix(dest, "/"),
+		Mode: fileMode,
+		Size: int64(len(content)),
+	}
+
+	img.m.Lock()
+	if err := img.out.WriteHeader(hdr); err != nil {
+		img.m.Unlock()
+		return err
+	}
+	if _, err := img.out.Write(content); err != nil {
+		img.m.Unlock()
+		return err
+	}
+	img.m.Unlock()
+
+	return nil
+}
+
 func elfSectionContent(s *elf.Section) (string, error) {
 	b, err := s.Data()
 	if err != nil {