Re: [PATCH bpf-next v3 3/4] selftests/bpf: Add selftest for attaching tracing programs to functions in deny list

[Yonghong Song]

On 7/22/25 8:34 AM, KaFai Wan wrote:

The result:

  $ tools/testing/selftests/bpf/test_progs -t tracing_failure/tracing_deny
  #468/3   tracing_failure/tracing_deny:OK
  #468     tracing_failure:OK
  Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: KaFai Wan <kafai....@linux.dev>

LGTM but see a nit below.

Acked-by: Yonghong Song <yonghong.s...@linux.dev>

---
  .../bpf/prog_tests/tracing_failure.c          | 33 +++++++++++++++++++
  .../selftests/bpf/progs/tracing_failure.c     |  6 ++++
  2 files changed, 39 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/tracing_failure.c 
b/tools/testing/selftests/bpf/prog_tests/tracing_failure.c
index a222df765bc3..140fb0d175cf 100644
--- a/tools/testing/selftests/bpf/prog_tests/tracing_failure.c
+++ b/tools/testing/selftests/bpf/prog_tests/tracing_failure.c
@@ -28,10 +28,43 @@ static void test_bpf_spin_lock(bool is_spin_lock)
        tracing_failure__destroy(skel);
  }

+static void test_tracing_deny(void)

+{
+       struct tracing_failure *skel;
+       char log_buf[256];
+       int btf_id, err;
+
+       /* migrate_disable depends on CONFIG_SMP */
+       btf_id = libbpf_find_vmlinux_btf_id("migrate_disable", 
BPF_TRACE_FENTRY);
+       if (btf_id <= 0) {
+               test__skip();
+               return;
+       }

There is a discussion about inlining migrate_disable(). See
  
https://lore.kernel.org/bpf/CAADnVQ+Afov4E=9t=3M=zZmO9z4ZqT6imWD5xijDHshTf3J=r...@mail.gmail.com/

Maybe trying to find a different function? Otherwise, if migrate_disable
is inlined and this test will become useless.

+
+       skel = tracing_failure__open();
+       if (!ASSERT_OK_PTR(skel, "tracing_failure__open"))
+               return;
+
+       bpf_program__set_autoload(skel->progs.tracing_deny, true);
+       bpf_program__set_log_buf(skel->progs.tracing_deny, log_buf, 
sizeof(log_buf));
+
+       err = tracing_failure__load(skel);
+       if (!ASSERT_ERR(err, "tracing_failure__load"))
+               goto out;
+
+       ASSERT_HAS_SUBSTR(log_buf,
+                         "Attaching tracing programs to function 'migrate_disable' 
is rejected.",
+                         "log_buf");
+out:
+       tracing_failure__destroy(skel);
+}
+
  void test_tracing_failure(void)
  {
        if (test__start_subtest("bpf_spin_lock"))
                test_bpf_spin_lock(true);
        if (test__start_subtest("bpf_spin_unlock"))
                test_bpf_spin_lock(false);
+       if (test__start_subtest("tracing_deny"))
+               test_tracing_deny();
  }
diff --git a/tools/testing/selftests/bpf/progs/tracing_failure.c 
b/tools/testing/selftests/bpf/progs/tracing_failure.c
index d41665d2ec8c..dfa152e8194e 100644
--- a/tools/testing/selftests/bpf/progs/tracing_failure.c
+++ b/tools/testing/selftests/bpf/progs/tracing_failure.c
@@ -18,3 +18,9 @@ int BPF_PROG(test_spin_unlock, struct bpf_spin_lock *lock)
  {
        return 0;
  }
+
+SEC("?fentry/migrate_disable")
+int BPF_PROG(tracing_deny)
+{
+       return 0;
+}