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

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Date:   Thu, 7 Dec 2023 20:20:16 +0100
From:   Marco Elver <elver@...gle.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Kyle Huey <me@...ehuey.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, 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.