[bpf-next v3 03/12] selftests/bpf: Avoid another case of errno clobbering

[Krzesimir Nowak]

Commit 8184d44c9a57 ("selftests/bpf: skip verifier tests for
unsupported program types") added a check for an unsupported program
type. The function doing it changes errno, so test_verifier should
save it before calling it if test_verifier wants to print a reason why
verifying a BPF program of a supported type failed.

Changes since v2:
- Move the declaration to fit the reverse christmas tree style.

Fixes: 8184d44c9a57 ("selftests/bpf: skip verifier tests for unsupported 
program types")
Cc: Stanislav Fomichev <s...@google.com>
Signed-off-by: Krzesimir Nowak <krzesi...@kinvolk.io>
---
 tools/testing/selftests/bpf/test_verifier.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/test_verifier.c 
b/tools/testing/selftests/bpf/test_verifier.c
index 3fe126e0083b..c7541f572932 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -864,6 +864,7 @@ static void do_test_single(struct bpf_test *test, bool 
unpriv,
        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;
@@ -894,6 +895,7 @@ static void do_test_single(struct bpf_test *test, bool 
unpriv,
                pflags |= BPF_F_ANY_ALIGNMENT;
        fd_prog = bpf_verify_program(prog_type, prog, prog_len, pflags,
                                     "GPL", 0, bpf_vlog, sizeof(bpf_vlog), 4);
+       saved_errno = errno;
        if (fd_prog < 0 && !bpf_probe_prog_type(prog_type, 0)) {
                printf("SKIP (unsupported program type %d)\n", prog_type);
                skips++;
@@ -910,7 +912,7 @@ static void do_test_single(struct bpf_test *test, bool 
unpriv,
        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
-- 
2.20.1