Re: [PATCH v3 bpf-next 3/3] selftests/bpf: Add test for attaching kprobe with long event names

[Feng Yang]

On Mon, 14 Apr 2025 13:47:55 +0200, Jiri Olsa <olsajiri@xxxxxxxxx> wrote:

> On Mon, Apr 14, 2025 at 05:34:02PM +0800, Feng Yang wrote:
> > From: Feng Yang <yangfeng@xxxxxxxxxx>
> > 
> > This test verifies that attaching kprobe/kretprobe with long event names
> > does not trigger EINVAL errors.
> > 
> > Signed-off-by: Feng Yang <yangfeng@xxxxxxxxxx>
> > ---
> >  .../selftests/bpf/prog_tests/attach_probe.c   | 35 +++++++++++++++++++
> >  .../selftests/bpf/test_kmods/bpf_testmod.c    |  5 +++
> >  .../bpf/test_kmods/bpf_testmod_kfunc.h        |  2 ++
> >  3 files changed, 42 insertions(+)
> > 
> > diff --git a/tools/testing/selftests/bpf/prog_tests/attach_probe.c b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
> > index 9b7f36f39c32..633b5eb4379b 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/attach_probe.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
> > @@ -168,6 +168,39 @@ static void test_attach_uprobe_long_event_name(void)
> >  	test_attach_probe_manual__destroy(skel);
> >  }
> >  
> > +/* attach kprobe/kretprobe long event name testings */
> > +static void test_attach_kprobe_long_event_name(void)
> > +{
> > +	DECLARE_LIBBPF_OPTS(bpf_kprobe_opts, kprobe_opts);
> > +	struct bpf_link *kprobe_link, *kretprobe_link;
> > +	struct test_attach_probe_manual *skel;
> > +
> > +	skel = test_attach_probe_manual__open_and_load();
> > +	if (!ASSERT_OK_PTR(skel, "skel_kprobe_manual_open_and_load"))
> > +		return;
> > +
> > +	/* manual-attach kprobe/kretprobe */
> > +	kprobe_opts.attach_mode = PROBE_ATTACH_MODE_LEGACY;
> > +	kprobe_opts.retprobe = false;
> > +	kprobe_link = bpf_program__attach_kprobe_opts(skel->progs.handle_kprobe,
> > +						      "bpf_kfunc_looooooooooooooooooooooooooooooong_name",
> > +						      &kprobe_opts);
> > +	if (!ASSERT_OK_PTR(kprobe_link, "attach_kprobe_long_event_name"))
> > +		goto cleanup;
> > +	skel->links.handle_kprobe = kprobe_link;
> > +
> > +	kprobe_opts.retprobe = true;
> > +	kretprobe_link = bpf_program__attach_kprobe_opts(skel->progs.handle_kretprobe,
> > +							 "bpf_kfunc_looooooooooooooooooooooooooooooong_name",
> > +							 &kprobe_opts);
> > +	if (!ASSERT_OK_PTR(kretprobe_link, "attach_kretprobe_long_event_name"))
> > +		goto cleanup;
> > +	skel->links.handle_kretprobe = kretprobe_link;
> > +
> > +cleanup:
> > +	test_attach_probe_manual__destroy(skel);
> > +}
> > +
> >  static void test_attach_probe_auto(struct test_attach_probe *skel)
> >  {
> >  	struct bpf_link *uprobe_err_link;
> > @@ -371,6 +404,8 @@ void test_attach_probe(void)
> >  
> >  	if (test__start_subtest("uprobe-long_name"))
> >  		test_attach_uprobe_long_event_name();
> > +	if (test__start_subtest("kprobe-long_name"))
> > +		test_attach_kprobe_long_event_name();
> >  
> >  cleanup:
> >  	test_attach_probe__destroy(skel);
> > diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
> > index f38eaf0d35ef..439f6c2b2456 100644
> > --- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
> > +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
> > @@ -1053,6 +1053,10 @@ __bpf_kfunc int bpf_kfunc_st_ops_inc10(struct st_ops_args *args)
> >  	return args->a;
> >  }
> >  
> > +__bpf_kfunc void bpf_kfunc_looooooooooooooooooooooooooooooong_name(void)
> > +{
> > +}
> 
> does it need to be a kfunc? IIUC it just needs to be a normal kernel/module function
> 
> jirka
> 

Indeed, so is it okay if I make the following modifications:

--- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
@@ -134,6 +134,10 @@ bpf_testmod_test_arg_ptr_to_struct(struct bpf_testmod_struct_arg_1 *a) {
 	return bpf_testmod_test_struct_arg_result;
 }
 
+noinline void bpf_testmod_looooooooooooooooooooooooooooooong_name(void)
+{
+}
+
 __bpf_kfunc void
 bpf_testmod_test_mod_kfunc(int i)

Thanks.

> > +
> >  BTF_KFUNCS_START(bpf_testmod_check_kfunc_ids)
> >  BTF_ID_FLAGS(func, bpf_testmod_test_mod_kfunc)
> >  BTF_ID_FLAGS(func, bpf_kfunc_call_test1)
> > @@ -1093,6 +1097,7 @@ BTF_ID_FLAGS(func, bpf_kfunc_st_ops_test_prologue, KF_TRUSTED_ARGS | KF_SLEEPABL
> >  BTF_ID_FLAGS(func, bpf_kfunc_st_ops_test_epilogue, KF_TRUSTED_ARGS | KF_SLEEPABLE)
> >  BTF_ID_FLAGS(func, bpf_kfunc_st_ops_test_pro_epilogue, KF_TRUSTED_ARGS | KF_SLEEPABLE)
> >  BTF_ID_FLAGS(func, bpf_kfunc_st_ops_inc10, KF_TRUSTED_ARGS)
> > +BTF_ID_FLAGS(func, bpf_kfunc_looooooooooooooooooooooooooooooong_name)
> >  BTF_KFUNCS_END(bpf_testmod_check_kfunc_ids)
> >  
> >  static int bpf_testmod_ops_init(struct btf *btf)
> > diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
> > index b58817938deb..e5b833140418 100644
> > --- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
> > +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
> > @@ -159,4 +159,6 @@ void bpf_kfunc_trusted_task_test(struct task_struct *ptr) __ksym;
> >  void bpf_kfunc_trusted_num_test(int *ptr) __ksym;
> >  void bpf_kfunc_rcu_task_test(struct task_struct *ptr) __ksym;
> >  
> > +void bpf_kfunc_looooooooooooooooooooooooooooooong_name(void) __ksym;
> > +
> >  #endif /* _BPF_TESTMOD_KFUNC_H */
> > -- 
> > 2.43.0
> >