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

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Message-ID: <620df220-4b82-4102-ba56-1ed348c2f8cb@linux.dev>
Date:   Thu, 7 Dec 2023 19:46:56 -0800
From:   Yonghong Song <yonghong.song@...ux.dev>
To:     Kyle Huey <me@...ehuey.com>, 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>,
        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 12/7/23 5:08 PM, Kyle Huey wrote:
> On Thu, Dec 7, 2023 at 2:56 PM Kyle Huey <me@...ehuey.com> wrote:
>> 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
> That doesn't really help (though perhaps it should be done anyway so
> the selftests aren't reaching into include/) because the glibc headers
> still redefine a ton of stuff in asm-generic/siginfo.h.

Just for testing purpose, I think you can avoid includeasm/siginfo.h and directly define necessary structures in the C file 
directly, right?

>
> - Kyle