Re: [PATCH bpf-next v2 2/2] selftests/bpf: Test fentry link after tracing_multi link

[Jiri Olsa]

On Sat, Jul 11, 2026 at 08:48:22PM +0800, Leon Hwang wrote:
> Verify that there's no any issue to attach tracing_multi link, then attach
> fentry link.
> 
> Assisted-by: Codex:gpt-5.6-sol
> Signed-off-by: Leon Hwang <leon.hwang@xxxxxxxxx>

Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>

thanks,
jirka


> ---
>  .../selftests/bpf/prog_tests/tracing_multi.c  | 69 +++++++++++++++++++
>  .../progs/tracing_multi_intersect_attach.c    |  8 +++
>  2 files changed, 77 insertions(+)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/tracing_multi.c b/tools/testing/selftests/bpf/prog_tests/tracing_multi.c
> index f02ffc7f41d7..0aa9532a05cf 100644
> --- a/tools/testing/selftests/bpf/prog_tests/tracing_multi.c
> +++ b/tools/testing/selftests/bpf/prog_tests/tracing_multi.c
> @@ -460,6 +460,73 @@ static void test_intersect(void)
>  	tracing_multi_intersect__destroy(skel);
>  }
>  
> +static void test_fentry_after_multi(void)
> +{
> +	static const char * const funcs[] = {
> +		"bpf_fentry_test1",
> +	};
> +	struct bpf_link *fentry_link = NULL, *multi_link = NULL;
> +	struct tracing_multi_intersect *skel = NULL;
> +	LIBBPF_OPTS(bpf_tracing_multi_opts, opts);
> +	LIBBPF_OPTS(bpf_test_run_opts, topts);
> +	__u32 *ids = NULL;
> +	int err;
> +
> +	skel = tracing_multi_intersect__open_and_load();
> +	if (!ASSERT_OK_PTR(skel, "tracing_multi_intersect__open_and_load"))
> +		return;
> +
> +	skel->bss->pid = getpid();
> +
> +	ids = get_ids(funcs, ARRAY_SIZE(funcs), NULL);
> +	if (!ASSERT_OK_PTR(ids, "get_ids"))
> +		goto cleanup;
> +
> +	opts.ids = ids;
> +	opts.cnt = ARRAY_SIZE(funcs);
> +	multi_link = bpf_program__attach_tracing_multi(skel->progs.fentry_1, NULL, &opts);
> +	if (!ASSERT_OK_PTR(multi_link, "attach_multi"))
> +		goto cleanup;
> +
> +	fentry_link = bpf_program__attach(skel->progs.fentry);
> +	if (!ASSERT_OK_PTR(fentry_link, "attach_fentry"))
> +		goto cleanup;
> +
> +	err = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.fentry_1), &topts);
> +	if (!ASSERT_OK(err, "test_run"))
> +		goto cleanup;
> +	ASSERT_EQ(skel->bss->test_result_fentry_1, 1, "multi_fentry");
> +	ASSERT_EQ(skel->bss->test_result_fentry, 1, "fentry");
> +
> +	err = bpf_link__destroy(fentry_link);
> +	fentry_link = NULL;
> +	if (!ASSERT_OK(err, "destroy_fentry"))
> +		goto cleanup;
> +
> +	err = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.fentry_1), &topts);
> +	if (!ASSERT_OK(err, "test_run_multi"))
> +		goto cleanup;
> +	ASSERT_EQ(skel->bss->test_result_fentry_1, 2, "multi_fentry_only");
> +	ASSERT_EQ(skel->bss->test_result_fentry, 1, "fentry_detached");
> +
> +	err = bpf_link__destroy(multi_link);
> +	multi_link = NULL;
> +	if (!ASSERT_OK(err, "destroy_multi"))
> +		goto cleanup;
> +
> +	err = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.fentry_1), &topts);
> +	if (!ASSERT_OK(err, "test_run_detached"))
> +		goto cleanup;
> +	ASSERT_EQ(skel->bss->test_result_fentry_1, 2, "multi_fentry_detached");
> +	ASSERT_EQ(skel->bss->test_result_fentry, 1, "fentry_still_detached");
> +
> +cleanup:
> +	bpf_link__destroy(fentry_link);
> +	bpf_link__destroy(multi_link);
> +	free(ids);
> +	tracing_multi_intersect__destroy(skel);
> +}
> +
>  static void test_session(void)
>  {
>  	LIBBPF_OPTS(bpf_test_run_opts, topts);
> @@ -957,4 +1024,6 @@ void test_tracing_multi_test(void)
>  	if (test__start_subtest("attach_api_fails"))
>  		test_attach_api_fails();
>  	RUN_TESTS(tracing_multi_verifier);
> +	if (test__start_subtest("fentry_after_multi"))
> +		test_fentry_after_multi();
>  }
> diff --git a/tools/testing/selftests/bpf/progs/tracing_multi_intersect_attach.c b/tools/testing/selftests/bpf/progs/tracing_multi_intersect_attach.c
> index cd5be0bb6ffd..5b0af8f4c62f 100644
> --- a/tools/testing/selftests/bpf/progs/tracing_multi_intersect_attach.c
> +++ b/tools/testing/selftests/bpf/progs/tracing_multi_intersect_attach.c
> @@ -11,6 +11,14 @@ __u64 test_result_fentry_1 = 0;
>  __u64 test_result_fentry_2 = 0;
>  __u64 test_result_fexit_1 = 0;
>  __u64 test_result_fexit_2 = 0;
> +__u64 test_result_fentry = 0;
> +
> +SEC("fentry/bpf_fentry_test1")
> +int BPF_PROG(fentry)
> +{
> +	tracing_multi_arg_check(ctx, &test_result_fentry, false);
> +	return 0;
> +}
>  
>  SEC("fentry.multi")
>  int BPF_PROG(fentry_1)
> -- 
> 2.55.0
>