selftests/bpf: Fix the issue where the error code is 0

The error message printed here only uses the previous err value,
which results in it being printed as 0.
When bpf_map__attach_struct_ops encounters an error,
it uses libbpf_err_ptr(err) to set errno = -err and returns NULL.
Therefore, Using -errno can fix this issue.

Fix before:
run_subtest:FAIL:1019 bpf_map__attach_struct_ops failed for map pro_epilogue: err=0

Fix after:
run_subtest:FAIL:1019 bpf_map__attach_struct_ops failed for map pro_epilogue: err=-9

Signed-off-by: Feng Yang <yangfeng@kylinos.cn>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20250908060810.1054341-1-yangfeng59949@163.com

diff --git a/tools/testing/selftests/bpf/test_loader.c b/tools/testing/selftests/bpf/test_loader.c
index a9388ac88358714f0d914fbaf3adb9fd238e7491..9f684d0dc5b4bad122c1106964ec2db4af690b2b 100644 (file)
--- a/tools/testing/selftests/bpf/test_loader.c
+++ b/tools/testing/selftests/bpf/test_loader.c
@@ -1088,7 +1088,7 @@ void run_subtest(struct test_loader *tester,
                        link = bpf_map__attach_struct_ops(map);
                        if (!link) {
                                PRINT_FAIL("bpf_map__attach_struct_ops failed for map %s: err=%d\n",
-                                          bpf_map__name(map), err);
+                                          bpf_map__name(map), -errno);
                                goto tobj_cleanup;
                        }
                        links[links_cnt++] = link;