selftests/bpf: Print reason when a tester could not run a program

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

diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index 4bfe3aa..ceea940 100644 (file)
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -936,6 +936,7 @@ 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;
@@ -997,6 +998,7 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
        }
 
        fd_prog = bpf_load_program_xattr(&attr, bpf_vlog, sizeof(bpf_vlog));
+       saved_errno = errno;
 
        /* BPF_PROG_TYPE_TRACING requires more setup and
         * bpf_probe_prog_type won't give correct answer
@@ -1013,7 +1015,7 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
        if (expected_ret == ACCEPT || expected_ret == VERBOSE_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