[PATCH v5] selftests/clone3: Fix broken test under !CONFIG_TIME_NS

[Tiezhu Yang]

When execute the following command to test clone3 on LoongArch:

  # cd tools/testing/selftests/clone3 && make && ./clone3

we can see the following error info:

  # [5719] Trying clone3() with flags 0x80 (size 0)
  # Invalid argument - Failed to create new process
  # [5719] clone3() with flags says: -22 expected 0
  not ok 18 [5719] Result (-22) is different than expected (0)

This is because if CONFIG_TIME_NS is not set, but the flag
CLONE_NEWTIME (0x80) is used to clone a time namespace, it
will return -EINVAL in copy_time_ns().

If kernel does not support CONFIG_TIME_NS, /proc/self/ns/time
will be not exist, and then we should skip clone3() test with
CLONE_NEWTIME.

With this patch under !CONFIG_TIME_NS:

  # cd tools/testing/selftests/clone3 && make && ./clone3
  ...
  # Time namespaces are not supported
  ok 18 # SKIP Skipping clone3() with CLONE_NEWTIME
  # Totals: pass:17 fail:0 xfail:0 xpass:0 skip:1 error:0

Fixes: 515bddf0ec41 ("selftests/clone3: test clone3 with CLONE_NEWTIME")
Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
---

v5:
  -- Rebase on the next branch of shuah/linux-kselftest.git
     to avoid potential merge conflicts due to changes in the link:
     https://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest.git/commit/?h=next&id=f8424c54d041
  -- Update the commit message and send it as a single patch

Here is the v4 patch:
https://lore.kernel.org/loongarch/1685968410-5412-2-git-send-email-yangtiezhu@xxxxxxxxxxx/

 tools/testing/selftests/clone3/clone3.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/clone3/clone3.c b/tools/testing/selftests/clone3/clone3.c
index e60cf4d..1c61e3c 100644
--- a/tools/testing/selftests/clone3/clone3.c
+++ b/tools/testing/selftests/clone3/clone3.c
@@ -196,7 +196,12 @@ int main(int argc, char *argv[])
 			CLONE3_ARGS_NO_TEST);
 
 	/* Do a clone3() in a new time namespace */
-	test_clone3(CLONE_NEWTIME, 0, 0, CLONE3_ARGS_NO_TEST);
+	if (access("/proc/self/ns/time", F_OK) == 0) {
+		test_clone3(CLONE_NEWTIME, 0, 0, CLONE3_ARGS_NO_TEST);
+	} else {
+		ksft_print_msg("Time namespaces are not supported\n");
+		ksft_test_result_skip("Skipping clone3() with CLONE_NEWTIME\n");
+	}
 
 	/* Do a clone3() with exit signal (SIGCHLD) in flags */
 	test_clone3(SIGCHLD, 0, -EINVAL, CLONE3_ARGS_NO_TEST);
-- 
2.1.0