Re: [PATCH bpf-next 2/2] selftests: bpf: Add a new test for bare tracepoints

From: Qais Yousef
Date: Tue Jan 12 2021 - 14:28:42 EST

On 01/11/21 23:26, Andrii Nakryiko wrote:
> On Mon, Jan 11, 2021 at 10:20 AM Qais Yousef <qais.yousef@xxxxxxx> wrote:
> >
> > Reuse module_attach infrastructure to add a new bare tracepoint to check
> > we can attach to it as a raw tracepoint.
> >
> > Signed-off-by: Qais Yousef <qais.yousef@xxxxxxx>
> > ---
> >
> > Andrii
> >
> > I was getting the error below when I was trying to run the test.
> > I had to comment out all related fentry* code to be able to test the raw_tp
> > stuff. Not sure something I've done wrong or it's broken for some reason.
> > I was on v5.11-rc2.
>
> Check that you have all the required Kconfig options from
> tools/testing/selftests/bpf/config. And also you will need to build

Yep I have merged this config snippet using merge_config.sh script.

> pahole from master, 1.19 doesn't have some fixes that add kernel
> module support. I think pahole is the reasons why you have the failure
> below.

I am using pahole 1.19. I have built it from tip of master though.

/trying using v1.19 tag

Still fails the same.

>
> >
> > $ sudo ./test_progs -v -t module_attach
>
> use -vv when debugging stuff like that with test_progs, it will output
> libbpf detailed logs, that often are very helpful

I tried that but it didn't help me. Full output is here

https://paste.debian.net/1180846

>
> > bpf_testmod.ko is already unloaded.
> > Loading bpf_testmod.ko...
> > Successfully loaded bpf_testmod.ko.
> > test_module_attach:PASS:skel_open 0 nsec
> > test_module_attach:PASS:set_attach_target 0 nsec
> > test_module_attach:PASS:skel_load 0 nsec
> > libbpf: prog 'handle_fentry': failed to attach: ERROR: strerror_r(-524)=22
> > libbpf: failed to auto-attach program 'handle_fentry': -524
> > test_module_attach:FAIL:skel_attach skeleton attach failed: -524
> > #58 module_attach:FAIL
> > Successfully unloaded bpf_testmod.ko.
> > Summary: 0/0 PASSED, 0 SKIPPED, 1 FAILED
> >
>
> But even apart from test failure, there seems to be kernel build
> failure. See [0] for what fails in kernel-patches CI.
>
> [0] https://travis-ci.com/github/kernel-patches/bpf/builds/212730017

Sorry about that. I did a last minute change because of checkpatch.pl error and
it seems I either forgot to rebuild or missed that the rebuild failed :/

>
>
> >
> > .../selftests/bpf/bpf_testmod/bpf_testmod-events.h | 6 ++++++
> > tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c | 2 ++
> > tools/testing/selftests/bpf/prog_tests/module_attach.c | 1 +
> > tools/testing/selftests/bpf/progs/test_module_attach.c | 10 ++++++++++
> > 4 files changed, 19 insertions(+)
> >
> > diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h
> > index b83ea448bc79..e1ada753f10c 100644
> > --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h
> > +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h
> > @@ -28,6 +28,12 @@ TRACE_EVENT(bpf_testmod_test_read,
> > __entry->pid, __entry->comm, __entry->off, __entry->len)
> > );
> >
> > +/* A bare tracepoint with no event associated with it */
> > +DECLARE_TRACE(bpf_testmod_test_read_bare,
> > + TP_PROTO(struct task_struct *task, struct bpf_testmod_test_read_ctx *ctx),
> > + TP_ARGS(task, ctx)
> > +);
> > +
> > #endif /* _BPF_TESTMOD_EVENTS_H */
> >
> > #undef TRACE_INCLUDE_PATH
> > diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> > index 2df19d73ca49..d63cebdaca44 100644
> > --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> > +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> > @@ -22,6 +22,8 @@ bpf_testmod_test_read(struct file *file, struct kobject *kobj,
> > };
> >
> > trace_bpf_testmod_test_read(current, &ctx);
> > + ctx.len++;
> > + trace_bpf_testmod_test_read_bare(current, &ctx);
>
> It's kind of boring to have two read tracepoints :) Do you mind adding

Hehe boring is good :p

> a write tracepoint and use bare tracepoint there? You won't need this
> ctx.len++ hack as well. Feel free to add identical
> bpf_testmod_test_write_ctx (renaming it is more of a pain).

It was easy to get this done. So I think it should be easy to make it a write
too :)

Thanks

--
Qais Yousef

>
> >
> > return -EIO; /* always fail */
> > }
> > diff --git a/tools/testing/selftests/bpf/prog_tests/module_attach.c b/tools/testing/selftests/bpf/prog_tests/module_attach.c
> > index 50796b651f72..7085a118f38c 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/module_attach.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/module_attach.c
> > @@ -50,6 +50,7 @@ void test_module_attach(void)
> > ASSERT_OK(trigger_module_test_read(READ_SZ), "trigger_read");
> >
> > ASSERT_EQ(bss->raw_tp_read_sz, READ_SZ, "raw_tp");
> > + ASSERT_EQ(bss->raw_tp_bare_read_sz, READ_SZ+1, "raw_tp_bare");
> > ASSERT_EQ(bss->tp_btf_read_sz, READ_SZ, "tp_btf");
> > ASSERT_EQ(bss->fentry_read_sz, READ_SZ, "fentry");
> > ASSERT_EQ(bss->fentry_manual_read_sz, READ_SZ, "fentry_manual");
> > diff --git a/tools/testing/selftests/bpf/progs/test_module_attach.c b/tools/testing/selftests/bpf/progs/test_module_attach.c
> > index efd1e287ac17..08aa157afa1d 100644
> > --- a/tools/testing/selftests/bpf/progs/test_module_attach.c
> > +++ b/tools/testing/selftests/bpf/progs/test_module_attach.c
> > @@ -17,6 +17,16 @@ int BPF_PROG(handle_raw_tp,
> > return 0;
> > }
> >
> > +__u32 raw_tp_bare_read_sz = 0;
> > +
> > +SEC("raw_tp/bpf_testmod_test_read_bare")
> > +int BPF_PROG(handle_raw_tp_bare,
> > + struct task_struct *task, struct bpf_testmod_test_read_ctx *read_ctx)
> > +{
> > + raw_tp_bare_read_sz = BPF_CORE_READ(read_ctx, len);
> > + return 0;
> > +}
> > +
> > __u32 tp_btf_read_sz = 0;
> >
> > SEC("tp_btf/bpf_testmod_test_read")
> > --
> > 2.25.1
> >