Re: [PATCHv2 bpf-next 8/9] selftests/bpf: Add test for recursion counts of perf event link kprobe

[Jiri Olsa <olsajiri@gmail.com>]

On Thu, Sep 07, 2023 at 11:55:27AM -0700, Song Liu wrote:
> On Thu, Sep 7, 2023 at 12:14 AM Jiri Olsa <jolsa@kernel.org> wrote:
> >
> > Adding selftest that puts kprobe.multi on bpf_fentry_test1 that
> > calls bpf_kfunc_common_test kfunc which has 3 perf event kprobes
> > and 1 kprobe.multi attached.
> >
> > Because fprobe (kprobe.multi attach layear) does not have strict
> > recursion check the kprobe's bpf_prog_active check is hit for test2-5.
> >
> > Disabling this test for arm64, because there's no fprobe support yet.
> >
> > Acked-by: Hou Tao <houtao1@huawei.com>
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> 
> Reviewed-and-tested-by: Song Liu <song@kernel.org>
> 
> With on nitpick below.
> 
> > ---
> >  tools/testing/selftests/bpf/DENYLIST.aarch64  |  1 +
> >  .../testing/selftests/bpf/prog_tests/missed.c | 51 +++++++++++++++++++
> >  .../bpf/progs/missed_kprobe_recursion.c       | 48 +++++++++++++++++
> >  3 files changed, 100 insertions(+)
> >  create mode 100644 tools/testing/selftests/bpf/progs/missed_kprobe_recursion.c
> >
> > diff --git a/tools/testing/selftests/bpf/DENYLIST.aarch64 b/tools/testing/selftests/bpf/DENYLIST.aarch64
> > index 7f768d335698..3f2187c049db 100644
> > --- a/tools/testing/selftests/bpf/DENYLIST.aarch64
> > +++ b/tools/testing/selftests/bpf/DENYLIST.aarch64
> > @@ -15,3 +15,4 @@ fexit_test/fexit_many_args                       # fexit_many_args:FAIL:fexit_ma
> >  fill_link_info/kprobe_multi_link_info            # bpf_program__attach_kprobe_multi_opts unexpected error: -95
> >  fill_link_info/kretprobe_multi_link_info         # bpf_program__attach_kprobe_multi_opts unexpected error: -95
> >  fill_link_info/kprobe_multi_invalid_ubuff        # bpf_program__attach_kprobe_multi_opts unexpected error: -95
> > +missed/kprobe_recursion                          # missed_kprobe_recursion__attach unexpected error: -95 (errno 95)
> > diff --git a/tools/testing/selftests/bpf/prog_tests/missed.c b/tools/testing/selftests/bpf/prog_tests/missed.c
> > index fc674258c81f..f10dc9232b3f 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/missed.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/missed.c
> > @@ -1,6 +1,7 @@
> >  // SPDX-License-Identifier: GPL-2.0
> >  #include <test_progs.h>
> >  #include "missed_kprobe.skel.h"
> > +#include "missed_kprobe_recursion.skel.h"
> >
> >  /*
> >   * Putting kprobe on bpf_fentry_test1 that calls bpf_kfunc_common_test
> > @@ -40,8 +41,58 @@ static void test_missed_perf_kprobe(void)
> >         missed_kprobe__destroy(skel);
> >  }
> >
> > +static __u64 get_count(int fd)
> 
> nit: Probably rename it as get_missed_count() or get_missed().

right, I was thinking of that ;-) will change

thanks,
jirka

> 
> > +{
> > +       struct bpf_prog_info info = {};
> > +       __u32 len = sizeof(info);
> > +       int err;
> > +
> > +       err = bpf_prog_get_info_by_fd(fd, &info, &len);
> > +       if (!ASSERT_OK(err, "bpf_prog_get_info_by_fd"))
> > +               return (__u64) -1;
> > +       return info.recursion_misses;
> > +}
> [...]