selftests/bpf: Avoid errno clobbering

mainline inclusion
from mainline-5.11-rc1
commit 5f61b7c6
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5EUVD
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5f61b7c6975b03e6ace2cfb13d415d5f475c8830

-------------------------------------------------

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.
Signed-off-by: NFlorian Lehner <dev@der-flo.net>
Signed-off-by: NAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20201204181828.11974-3-dev@der-flo.net
(cherry picked from commit 5f61b7c6)
Signed-off-by: NWang Yufen <wangyufen@huawei.com>

tools/testing/selftests/bpf/test_verifier.c

@@ -885,19 +885,36 @@ 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;