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Date:   Thu, 8 Jun 2023 10:40:15 -0700
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Subject: Re: [PATCH bpf v2 1/2] selftests/bpf: add a test for subprogram
 extables
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To:     Krister Johansen <kjlx@templeofstupid.com>, bpf@vger.kernel.org
Cc:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
        Mykola Lysenko <mykolal@fb.com>, Shuah Khan <shuah@kernel.org>,
        linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
        stable@vger.kernel.org
References: <cover.1686166633.git.kjlx@templeofstupid.com>
 <c3d55cfd8ce7ed989c997d1e3ea2678879227300.1686166633.git.kjlx@templeofstupid.com>
From:   Yonghong Song <yhs@meta.com>
In-Reply-To: <c3d55cfd8ce7ed989c997d1e3ea2678879227300.1686166633.git.kjlx@templeofstupid.com>
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On 6/7/23 2:04 PM, Krister Johansen wrote:
> In certain situations a program with subprograms may have a NULL
> extable entry.  This should not happen, and when it does, it turns a
> single trap into multiple.  Add a test case for further debugging and to
> prevent regressions.  N.b: without any other patches this can panic or
> oops a kernel.

Also, it would be great if you can show the kernel oops stack trace.

> 
> Signed-off-by: Krister Johansen <kjlx@templeofstupid.com>
> ---
>   .../bpf/prog_tests/subprogs_extable.c         | 35 +++++++++
>   .../bpf/progs/test_subprogs_extable.c         | 71 +++++++++++++++++++
>   2 files changed, 106 insertions(+)
>   create mode 100644 tools/testing/selftests/bpf/prog_tests/subprogs_extable.c
>   create mode 100644 tools/testing/selftests/bpf/progs/test_subprogs_extable.c
> 
[...]