[PATCH 3/3] selftests: cachestat: test for cachestat availability

From: Andre Przywara
Date: Tue Aug 15 2023 - 11:57:38 EST


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.

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).

Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
---
.../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) {
+ printf("1..0 # Skipped: cachestat syscall not available\n");
+ 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;
+ }

for (int i = 0; i < 5; i++) {
const char *dev_filename = dev_files[i];
--
2.25.1