syscallcompat: add tests for emulated syscalls

Also fix the bug in emulateFchmodat that was found by the tests.

1 files changed, 10 insertions, 0 deletions

diff --git a/internal/syscallcompat/emulate.go b/internal/syscallcompat/emulate.go
index 6cb0ea0..59d0ea5 100644
--- a/internal/syscallcompat/emulate.go
+++ b/internal/syscallcompat/emulate.go
@@ -135,6 +135,16 @@ func emulateFchmodat(dirfd int, path string, mode uint32, flags int) (err error)
 		return err
 	}
 	defer syscall.Fchdir(cwd)
+	// We also don't have Lchmod, so emulate it (poorly).
+	if flags&unix.AT_SYMLINK_NOFOLLOW > 0 {
+		fi, err := os.Lstat(path)
+		if err != nil {
+			return err
+		}
+		if fi.Mode()&os.ModeSymlink > 0 {
+			return nil
+		}
+	}
 	return syscall.Chmod(path, mode)
 }