syscallcompat: add Fstatat + emulation + test

Fstatat has recently been added to x/sys/unix. Make
it available for use in gocryptfs.
This commit is contained in:
Jakob Unterwurzacher 2017-12-03 17:53:14 +01:00
parent 441e796e70
commit e33593d30d
4 changed files with 77 additions and 0 deletions

View File

@ -210,3 +210,23 @@ func emulateMkdirat(dirfd int, path string, mode uint32) (err error) {
}
return syscall.Mkdir(path, mode)
}
// emulateFstatat emulates the syscall for platforms that don't have it
// in the kernel (darwin).
func emulateFstatat(dirfd int, path string, stat *unix.Stat_t, flags int) (err error) {
if !filepath.IsAbs(path) {
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 unix.Lstat(path, stat)
}

View File

@ -256,3 +256,38 @@ func TestEmulateMkdirat(t *testing.T) {
t.Fatalf("mkdirat did not create a directory")
}
}
func TestEmulateFstatat(t *testing.T) {
var st unix.Stat_t
// stat a normal file (size 3)
f, err := os.Create(tmpDir + "/fstatat")
if err != nil {
t.Fatal(err)
}
_, err = f.Write([]byte("foo"))
if err != nil {
t.Fatal(err)
}
f.Close()
err = emulateFstatat(tmpDirFd, "fstatat", &st, unix.AT_SYMLINK_NOFOLLOW)
if err != nil {
t.Fatal(err)
}
if st.Size != 3 {
t.Errorf("wrong file size: %d", st.Size)
}
// stat a symlink and check that the size matches the length of the
// symlink target. This proves that we have stat'ed the symlink itself.
err = os.Symlink(tmpDir+"/fstatat", tmpDir+"/fstatatSymlink")
if err != nil {
t.Fatal(err)
}
err = emulateFstatat(tmpDirFd, "fstatatSymlink", &st, unix.AT_SYMLINK_NOFOLLOW)
if err != nil {
t.Fatal(err)
}
expectedSize := int64(len(tmpDir + "/fstatat"))
if st.Size != expectedSize {
t.Errorf("symlink size: expected=%d, got=%d", expectedSize, st.Size)
}
}

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@ -3,6 +3,10 @@ package syscallcompat
import (
"log"
"syscall"
"golang.org/x/sys/unix"
"github.com/hanwen/go-fuse/fuse"
)
// Sorry, fallocate is not available on OSX at all and
@ -60,3 +64,11 @@ func Symlinkat(oldpath string, newdirfd int, newpath string) (err error) {
func Mkdirat(dirfd int, path string, mode uint32) (err error) {
return emulateMkdirat(dirfd, path, mode)
}
func Fstatat(dirfd int, path string, stat *unix.Stat_t, flags int) (err error) {
return emulateFstatat(dirfd, path, stat, flags)
}
func Getdents(fd int) ([]fuse.DirEntry, error) {
return emulateGetdents(fd)
}

View File

@ -105,3 +105,13 @@ func Symlinkat(oldpath string, newdirfd int, newpath string) (err error) {
func Mkdirat(dirfd int, path string, mode uint32) (err error) {
return syscall.Mkdirat(dirfd, path, mode)
}
// Fstatat syscall.
func Fstatat(dirfd int, path string, stat *unix.Stat_t, flags int) (err error) {
// Why would we ever want to call this without AT_SYMLINK_NOFOLLOW?
if flags&unix.AT_SYMLINK_NOFOLLOW == 0 {
tlog.Warn.Printf("Fstatat: adding missing AT_SYMLINK_NOFOLLOW flag")
flags |= unix.AT_SYMLINK_NOFOLLOW
}
return unix.Fstatat(dirfd, path, stat, flags)
}