[PATCH 0/2 v3] Improve error handling of verifier tests

[PATCH 0/2 v3] Improve error handling of verifier tests

[Florian Lehner]

These patches improve the error handling for verifier tests. With "Test
the 32bit narrow read" Krzesimir Nowak provided these patches first, but
they were never merged.
The improved error handling helps to implement and test BPF program types
that are not supported yet.

v3:
  - Add explicit fallthrough

v2:
  - Add unpriv check in error validation

Florian Lehner (2):
  selftests/bpf: Print reason when a tester could not run a program
  selftests/bpf: Avoid errno clobbering

 tools/testing/selftests/bpf/test_verifier.c | 31 +++++++++++++++++----
 1 file changed, 25 insertions(+), 6 deletions(-)

-- 
2.28.0

[PATCH 1/2] selftests/bpf: Print reason when a tester could not run a program

[Florian Lehner]

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")
Cc: Stanislav Fomichev <sdf@google.com>
Cc: Krzesimir Nowak <krzesimir@kinvolk.io>
Signed-off-by: Florian Lehner <dev@der-flo.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
---
 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 4bfe3aa2cfc4..ceea9409639e 100644
--- 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
-- 
2.28.0

[PATCH 2/2] selftests/bpf: Avoid errno clobbering

[Florian Lehner]

Print a message when the returned error is about a program type being
not supported or because of permission problems.
These messages are expected if the program to test was actually
executed.

Cc: Krzesimir Nowak <krzesimir@kinvolk.io>
Signed-off-by: Florian Lehner <dev@der-flo.net>
---
 tools/testing/selftests/bpf/test_verifier.c | 27 +++++++++++++++++----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index ceea9409639e..777a81404fdb 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -875,19 +875,36 @@ static int do_prog_test_run(int fd_prog, bool unpriv, uint32_t expected_val,
 	__u8 tmp[TEST_DATA_LEN << 2];
 	__u32 size_tmp = sizeof(tmp);
 	uint32_t retval;
-	int err;
+	int err, saved_errno;
 
 	if (unpriv)
 		set_admin(true);
 	err = bpf_prog_test_run(fd_prog, 1, data, size_data,
 				tmp, &size_tmp, &retval, NULL);
+	saved_errno = errno;
+
 	if (unpriv)
 		set_admin(false);
-	if (err && errno != 524/*ENOTSUPP*/ && errno != EPERM) {
-		printf("Unexpected bpf_prog_test_run error ");
-		return err;
+
+	if (err) {
+		switch (saved_errno) {
+		case 524/*ENOTSUPP*/:
+			printf("Did not run the program (not supported) ");
+			return 0;
+		case EPERM:
+			if (unpriv) {
+				printf("Did not run the program (no permission) ");
+				return 0;
+			}
+			/* fallthrough; */
+		default:
+			printf("FAIL: Unexpected bpf_prog_test_run error (%s) ",
+				strerror(saved_errno));
+			return err;
+		}
 	}
-	if (!err && retval != expected_val &&
+
+	if (retval != expected_val &&
 	    expected_val != POINTER_VALUE) {
 		printf("FAIL retval %d != %d ", retval, expected_val);
 		return 1;
-- 
2.28.0

Re: [PATCH 0/2 v3] Improve error handling of verifier tests

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf-next.git (refs/heads/master):

On Fri,  4 Dec 2020 19:18:26 +0100 you wrote:
> These patches improve the error handling for verifier tests. With "Test
> the 32bit narrow read" Krzesimir Nowak provided these patches first, but
> they were never merged.
> The improved error handling helps to implement and test BPF program types
> that are not supported yet.
> 
> v3:
>   - Add explicit fallthrough
> 
> [...]

Here is the summary with links:
  - [1/2] selftests/bpf: Print reason when a tester could not run a program
    https://git.kernel.org/bpf/bpf-next/c/7d17167244f5
  - [2/2] selftests/bpf: Avoid errno clobbering
    https://git.kernel.org/bpf/bpf-next/c/5f61b7c6975b

You are awesome, thank you!
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