[PATCH] selftests/clone3: Skip new time namespace test when unsupported

[Mark Brown]

Use a filter function to skip the time namespace test on systems with
!CONFIG_TIME_NS. This reworks a fix originally done by Tiezhu Yang prior
to the refactoring in 34dce23f7e40 ("selftests/clone3: Report descriptive
test names"). The changelog from their fix explains the issue very clearly:

When execute the following command to test clone3 under !CONFIG_TIME_NS:

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

we can see the following error info:

  # [7538] Trying clone3() with flags 0x80 (size 0)
  # Invalid argument - Failed to create new process
  # [7538] clone3() with flags says: -22 expected 0
  not ok 18 [7538] Result (-22) is different than expected (0)
  ...
  # Totals: pass:18 fail:1 xfail:0 xpass:0 skip:0 error: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:

  # make headers && cd tools/testing/selftests/clone3 && make && ./clone3
  ...
  # Time namespaces are not supported
  ok 18 # SKIP Skipping clone3() with CLONE_NEWTIME
  ...
  # Totals: pass:18 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>
Original-fix-from: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
---
 tools/testing/selftests/clone3/clone3.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/tools/testing/selftests/clone3/clone3.c b/tools/testing/selftests/clone3/clone3.c
index 9429d361059e..915846bc32cc 100644
--- a/tools/testing/selftests/clone3/clone3.c
+++ b/tools/testing/selftests/clone3/clone3.c
@@ -138,6 +138,16 @@ static bool not_root(void)
 	return false;
 }
 
+static bool timens_unsupported(void)
+{
+	if (access("/proc/self/ns/time", F_OK) == 0) {
+		ksft_print_msg("Time namespaces are not supported\n");
+		return true;
+	}
+
+	return false;
+}
+
 static size_t page_size_plus_8(void)
 {
 	return getpagesize() + 8;
@@ -282,6 +292,7 @@ static const struct test tests[] = {
 		.size = 0,
 		.expected = 0,
 		.test_mode = CLONE3_ARGS_NO_TEST,
+		.filter = timens_unsupported,
 	},
 	{
 		.name = "exit signal (SIGCHLD) in flags",

---
base-commit: 8d4099dd0727acfc8b0f644eacaf852f9d5dc649
change-id: 20231019-kselftest-clone3-time-ns-730b6f4187c7

Best regards,
-- 
Mark Brown <broonie@xxxxxxxxxx>