On Tue, 15 Aug 2023 16:25:54 -0700 Nhat Pham nphamcs@gmail.com wrote:
Hi Nhat,
many thanks for having a look!
On Tue, Aug 15, 2023 at 8:56 AM Andre Przywara andre.przywara@arm.com wrote:
As cachestat is a new syscall, it won't be available on older kernels, for instance those running on a build machine. In this case, a run reports all tests as "not ok" at the moment.
Interesting - I was under the assumption that if you backported the selftests for cachestat, you would also backport the syscall's implementation and wiring.
Well, just running the tests on the kernel you just built is only one use case. I build the tests from latest git HEAD, then copy them to a target system with some kernel running. Or I just build the tests and run them for regression testing on my build system with a distro kernel, which is Ubuntu's 5.15 flavour, in my case. The documentation explicitly mentions that selftests should work on older kernels (copying the normal userland compatibility requirements), check the second paragraph of Documentation/dev-tools/kselftest.rst.
But yeah, I guess if you build with !CONFIG_CACHESTAT_SYSCALL, these tests would fail.
Test for the cachestat syscall availability first, before doing further tests, and bail out early with a TAP SKIP comment.
This also uses the opportunity to add the proper TAP headers, and add one check for the syscall error handling (illegal file descriptor).
Thanks for the addition!
Signed-off-by: Andre Przywara andre.przywara@arm.com
.../selftests/cachestat/test_cachestat.c | 22 ++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/cachestat/test_cachestat.c b/tools/testing/selftests/cachestat/test_cachestat.c index a5a4ac8dcb76c..77620e7ecf562 100644 --- a/tools/testing/selftests/cachestat/test_cachestat.c +++ b/tools/testing/selftests/cachestat/test_cachestat.c @@ -15,6 +15,8 @@
#include "../kselftest.h"
+#define NR_TESTS 8
static const char * const dev_files[] = { "/dev/zero", "/dev/null", "/dev/urandom", "/proc/version", "/proc" @@ -235,7 +237,25 @@ bool test_cachestat_shmem(void)
int main(void) {
int ret = 0;
int ret;ksft_print_header();ret = syscall(__NR_cachestat, -1, NULL, NULL, 0);if (ret == -1 && errno == ENOSYS) {nit: if (ret && errno == ENOSYS) sounds cleaner, but up to you.
Do you ever return a positive value other than 0? I think technically errno is only valid when the return value is -1, so in the error case, which I wanted to test here explicitly. Some syscall selftests (I checked landlock the other day) do very elaborate testing of the error path, trying to carefully cover all corner cases: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tool...
So this test was inspired by that, but I didn't want to go that far here ;-)
printf("1..0 # Skipped: cachestat syscall not available\n");nit: perhaps ksft_print_msg()?
Ah, yes, of course!
return KSFT_SKIP;}ksft_set_plan(NR_TESTS);if (ret == -1 && errno == EBADF) {ksft_test_result_pass("bad file descriptor recognized\n");ret = 0;} else {ksft_test_result_fail("bad file descriptor ignored\n");ret = 1;}Nice!
for (int i = 0; i < 5; i++) { const char *dev_filename = dev_files[i];-- 2.25.1
Nitpicking aside: Acked-by: Nhat Pham nphamcs@gmail.com
Thanks, I will send a v2 later, using ksft_print_msg(). But first I will try if I can detect a tmpfs instance without boiling the ocean.
Cheers, Andre