linux-kernel - Re: [PATCH v2 3/3] selftest/bpf: Test a perf bpf program that suppresses side effects.

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Message-ID: <CAP045AoeVP=n5K+0jt2ddBspif7kx4hzOdBM86CuxNGRCgx4VA@mail.gmail.com>
Date:   Thu, 7 Dec 2023 14:56:24 -0800
From:   Kyle Huey <me@...ehuey.com>
To:     Marco Elver <elver@...gle.com>
Cc:     Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Kyle Huey <khuey@...ehuey.com>, linux-kernel@...r.kernel.org,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Yonghong Song <yonghong.song@...ux.dev>,
        "Robert O'Callahan" <robert@...llahan.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Mykola Lysenko <mykolal@...com>,
        Shuah Khan <shuah@...nel.org>, bpf@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v2 3/3] selftest/bpf: Test a perf bpf program that
 suppresses side effects.

On Thu, Dec 7, 2023 at 11:20 AM Marco Elver <elver@...gle.com> wrote:
>
> On Thu, 7 Dec 2023 at 20:12, Andrii Nakryiko <andrii.nakryiko@...il.com> wrote:
> >
> > On Thu, Dec 7, 2023 at 8:35 AM Kyle Huey <me@...ehuey.com> wrote:
> > >
> > > The test sets a hardware breakpoint and uses a bpf program to suppress the
> > > side effects of a perf event sample, including I/O availability signals,
> > > SIGTRAPs, and decrementing the event counter limit, if the ip matches the
> > > expected value. Then the function with the breakpoint is executed multiple
> > > times to test that all effects behave as expected.
> > >
> > > Signed-off-by: Kyle Huey <khuey@...ehuey.com>
> > > ---
> > >  .../selftests/bpf/prog_tests/perf_skip.c      | 145 ++++++++++++++++++
> > >  .../selftests/bpf/progs/test_perf_skip.c      |  15 ++
> > >  2 files changed, 160 insertions(+)
> > >  create mode 100644 tools/testing/selftests/bpf/prog_tests/perf_skip.c
> > >  create mode 100644 tools/testing/selftests/bpf/progs/test_perf_skip.c
> > >
> > > diff --git a/tools/testing/selftests/bpf/prog_tests/perf_skip.c b/tools/testing/selftests/bpf/prog_tests/perf_skip.c
> > > new file mode 100644
> > > index 000000000000..f6fa9bfd9efa
> > > --- /dev/null
> > > +++ b/tools/testing/selftests/bpf/prog_tests/perf_skip.c
> > > @@ -0,0 +1,145 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +#define _GNU_SOURCE
> > > +
> > > +/* We need the latest siginfo from the kernel repo. */
> > > +#include <asm/siginfo.h>
> >
> > selftests are built with UAPI headers' copies under tools/include, so
> > CI did catch a real issue, I think. Try copying
> > include/uapi/asm-generic/siginfo.h into
> > tools/include/uapi/asm-generic/siginfo.h ?
>
> I believe parts of this were inspired by
> tools/testing/selftests/perf_events/sigtrap_threads.c - getting the
> kernel headers is allowed, as long as $(KHDR_INCLUDES) is added to
> CFLAGS. See tools/testing/selftests/perf_events/Makefile. Not sure
> it's appropriate for this test though, if you don't want to add
> KHDR_INCLUDES for everything.

Yes, that's right. Namhyung's commit message for 91c97b36bd69 leads me
to believe that I should copy siginfo.h over into tools/include and
fix the perf_events self tests too.

- Kyle