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-rw-r--r--internal/syscallcompat/emulate.go193
1 files changed, 193 insertions, 0 deletions
diff --git a/internal/syscallcompat/emulate.go b/internal/syscallcompat/emulate.go
new file mode 100644
index 0000000..6cb0ea0
--- /dev/null
+++ b/internal/syscallcompat/emulate.go
@@ -0,0 +1,193 @@
+package syscallcompat
+
+import (
+ "os"
+ "path/filepath"
+ "sync"
+ "syscall"
+
+ "golang.org/x/sys/unix"
+)
+
+var chdirMutex sync.Mutex
+
+// emulateOpenat emulates the syscall for platforms that don't have it
+// in the kernel (darwin).
+func emulateOpenat(dirfd int, path string, flags int, mode uint32) (int, error) {
+ chdirMutex.Lock()
+ defer chdirMutex.Unlock()
+ if !filepath.IsAbs(path) {
+ // Save the old working directory
+ oldWd, err := os.Getwd()
+ if err != nil {
+ return -1, err
+ }
+ // Chdir to target directory
+ err = syscall.Fchdir(dirfd)
+ if err != nil {
+ return -1, err
+ }
+ // Chdir back at the end
+ defer os.Chdir(oldWd)
+ }
+ return syscall.Open(path, flags, mode)
+}
+
+// emulateRenameat emulates the syscall for platforms that don't have it
+// in the kernel (darwin).
+func emulateRenameat(olddirfd int, oldpath string, newdirfd int, newpath string) error {
+ chdirMutex.Lock()
+ defer chdirMutex.Unlock()
+ // Unless both paths are absolute we have to save the old working dir and
+ // Chdir(oldWd) back to it in the end. If we error out before the first
+ // chdir, Chdir(oldWd) is unneccassary but does no harm.
+ if !filepath.IsAbs(oldpath) || !filepath.IsAbs(newpath) {
+ oldWd, err := os.Getwd()
+ if err != nil {
+ return err
+ }
+ defer os.Chdir(oldWd)
+ }
+ // Make oldpath absolute
+ oldpath, err := dirfdAbs(olddirfd, oldpath)
+ if err != nil {
+ return err
+ }
+ // Make newpath absolute
+ newpath, err = dirfdAbs(newdirfd, newpath)
+ if err != nil {
+ return err
+ }
+ return syscall.Rename(oldpath, newpath)
+}
+
+// emulateUnlinkat emulates the syscall for platforms that don't have it
+// in the kernel (darwin).
+func emulateUnlinkat(dirfd int, path string, flags int) (err error) {
+ chdirMutex.Lock()
+ defer chdirMutex.Unlock()
+ cwd, err := syscall.Open(".", syscall.O_RDONLY, 0)
+ if err != nil {
+ return err
+ }
+ defer syscall.Close(cwd)
+ err = syscall.Fchdir(dirfd)
+ if err != nil {
+ return err
+ }
+ defer syscall.Fchdir(cwd)
+ if (flags & unix.AT_REMOVEDIR) != 0 {
+ return syscall.Rmdir(path)
+ } else {
+ return syscall.Unlink(path)
+ }
+}
+
+// emulateMknodat emulates the syscall for platforms that don't have it
+// in the kernel (darwin).
+func emulateMknodat(dirfd int, path string, mode uint32, dev int) error {
+ chdirMutex.Lock()
+ defer chdirMutex.Unlock()
+ if !filepath.IsAbs(path) {
+ oldWd, err := os.Getwd()
+ if err != nil {
+ return err
+ }
+ defer os.Chdir(oldWd)
+ }
+ path, err := dirfdAbs(dirfd, path)
+ if err != nil {
+ return err
+ }
+ return syscall.Mknod(path, mode, dev)
+}
+
+// dirfdAbs transforms the dirfd-relative "path" to an absolute one. If the
+// path is not already absolute, this function will change the working
+// directory. The caller has to chdir back.
+func dirfdAbs(dirfd int, path string) (string, error) {
+ if filepath.IsAbs(path) {
+ return path, nil
+ }
+ err := syscall.Fchdir(dirfd)
+ if err != nil {
+ return "", err
+ }
+ wd, err := os.Getwd()
+ if err != nil {
+ return "", err
+ }
+ return filepath.Join(wd, path), nil
+}
+
+// emulateFchmodat emulates the syscall for platforms that don't have it
+// in the kernel (darwin).
+func emulateFchmodat(dirfd int, path string, mode uint32, flags int) (err error) {
+ chdirMutex.Lock()
+ defer chdirMutex.Unlock()
+ cwd, err := syscall.Open(".", syscall.O_RDONLY, 0)
+ if err != nil {
+ return err
+ }
+ defer syscall.Close(cwd)
+ err = syscall.Fchdir(dirfd)
+ if err != nil {
+ return err
+ }
+ defer syscall.Fchdir(cwd)
+ return syscall.Chmod(path, mode)
+}
+
+// emulateFchownat emulates the syscall for platforms that don't have it
+// in the kernel (darwin).
+func emulateFchownat(dirfd int, path string, uid int, gid int, flags int) (err error) {
+ chdirMutex.Lock()
+ defer chdirMutex.Unlock()
+ cwd, err := syscall.Open(".", syscall.O_RDONLY, 0)
+ if err != nil {
+ return err
+ }
+ defer syscall.Close(cwd)
+ err = syscall.Fchdir(dirfd)
+ if err != nil {
+ return err
+ }
+ defer syscall.Fchdir(cwd)
+ return syscall.Lchown(path, uid, gid)
+}
+
+// emulateSymlinkat emulates the syscall for platforms that don't have it
+// in the kernel (darwin).
+func emulateSymlinkat(oldpath string, newdirfd int, newpath string) (err error) {
+ chdirMutex.Lock()
+ defer chdirMutex.Unlock()
+ cwd, err := syscall.Open(".", syscall.O_RDONLY, 0)
+ if err != nil {
+ return err
+ }
+ defer syscall.Close(cwd)
+ err = syscall.Fchdir(newdirfd)
+ if err != nil {
+ return err
+ }
+ defer syscall.Fchdir(cwd)
+ return syscall.Symlink(oldpath, newpath)
+}
+
+// emulateMkdirat emulates the syscall for platforms that don't have it
+// in the kernel (darwin).
+func emulateMkdirat(dirfd int, path string, mode uint32) (err error) {
+ chdirMutex.Lock()
+ defer chdirMutex.Unlock()
+ cwd, err := syscall.Open(".", syscall.O_RDONLY, 0)
+ if err != nil {
+ return err
+ }
+ defer syscall.Close(cwd)
+ err = syscall.Fchdir(dirfd)
+ if err != nil {
+ return err
+ }
+ defer syscall.Fchdir(cwd)
+ return syscall.Mkdir(path, mode)
+}