syscallcompat: add Fstatat + emulation + test

Fstatat has recently been added to x/sys/unix. Make
it available for use in gocryptfs.

1 files changed, 35 insertions, 0 deletions

diff --git a/internal/syscallcompat/emulate_test.go b/internal/syscallcompat/emulate_test.go
index 9b45672..c259778 100644
--- a/internal/syscallcompat/emulate_test.go
+++ b/internal/syscallcompat/emulate_test.go
@@ -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)
+	}
+}