[PATCH bpf-next] selftests/bpf: Report a failure to register the session key in test_progs

[Qiliang Yuan <odys.yuan@gmail.com>]

test_progs adds the key that verifies signed programs to the session
keyring before it runs any test, and exits when that fails.

It exits with 255 without printing anything. pam_keyinit revokes the
session keyring on logout, so a test_progs started in the background
from an ssh session that has been closed since leaves nothing but an
empty log behind, with no hint of what went wrong.

Print the error before exiting.

Fixes: b720903e2b14 ("selftests/bpf: Enable signature verification for some lskel tests")
Signed-off-by: Qiliang Yuan <odys.yuan@gmail.com>
---
 tools/testing/selftests/bpf/test_progs.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
index 46eb201b96a38..168d84cf4eb76 100644
--- a/tools/testing/selftests/bpf/test_progs.c
+++ b/tools/testing/selftests/bpf/test_progs.c
@@ -2065,8 +2065,11 @@ int main(int argc, char **argv)
 	libbpf_set_print(libbpf_print_fn);
 	err = register_session_key((const char *)test_progs_verification_cert,
 				   test_progs_verification_cert_len);
-	if (err < 0)
+	if (err < 0) {
+		fprintf(stderr, "Failed to add libbpf_session_key to the session keyring: %s\n",
+			strerror(errno));
 		return err;
+	}
 
 	traffic_monitor_set_print(traffic_monitor_print_fn);
 

---
base-commit: e1d84a37cba984388988d2f1ddc84561413f0db2
change-id: 20261008-selftests-bpf-test-progs-session-key-1c0a8570c051

Best regards,
-- 
Qiliang Yuan <odys.yuan@gmail.com>