From: Florian Lehner <dev@der-flo.net>
Date: Fri, 4 Dec 2020 19:18:27 +0100
Subject: selftests/bpf: Print reason when a tester could not run a program
Patch-mainline: v5.11-rc1
Git-commit: 7d17167244f5415bc6bc90f5bb0074b6d79676b4
References: bsc#1155518

Commit 8184d44c9a57 ("selftests/bpf: skip verifier tests for unsupported
program types") added a check to skip unsupported program types. As
bpf_probe_prog_type can change errno, do_single_test should save it before
printing a reason why a supported BPF program type failed to load.

Fixes: 8184d44c9a57 ("selftests/bpf: skip verifier tests for unsupported program types")
Signed-off-by: Florian Lehner <dev@der-flo.net>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20201204181828.11974-2-dev@der-flo.net
Acked-by: Gary Lin <glin@suse.com>
---
 tools/testing/selftests/bpf/test_verifier.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -869,6 +869,7 @@ static void do_test_single(struct bpf_te
 	int run_errs, run_successes;
 	int map_fds[MAX_NR_MAPS];
 	const char *expected_err;
+	int saved_errno;
 	int fixup_skips;
 	__u32 pflags;
 	int i, err;
@@ -908,6 +909,7 @@ static void do_test_single(struct bpf_te
 	attr.prog_flags = pflags;
 
 	fd_prog = bpf_load_program_xattr(&attr, bpf_vlog, sizeof(bpf_vlog));
+	saved_errno = errno;
 	if (fd_prog < 0 && !bpf_probe_prog_type(prog_type, 0)) {
 		printf("SKIP (unsupported program type %d)\n", prog_type);
 		skips++;
@@ -924,7 +926,7 @@ static void do_test_single(struct bpf_te
 	if (expected_ret == ACCEPT) {
 		if (fd_prog < 0) {
 			printf("FAIL\nFailed to load prog '%s'!\n",
-			       strerror(errno));
+			       strerror(saved_errno));
 			goto fail_log;
 		}
 #ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS