netdev - Re: [PATCHv2] btf_encoder: Match ftrace addresses within elf functions

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Date:   Wed, 17 Feb 2021 10:54:29 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     sedat.dilek@...il.com, Sedat Dilek <sedat.dilek@...il.com>
CC:     Jiri Olsa <jolsa@...nel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andriin@...com>,
        Andrii Nakryiko <andrii@...nel.org>, dwarves@...r.kernel.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        Yonghong Song <yhs@...com>, Hao Luo <haoluo@...gle.com>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Nathan Chancellor <nathan@...nel.org>
Subject: Re: [PATCHv2] btf_encoder: Match ftrace addresses within elf functions



On February 17, 2021 10:40:43 AM GMT-03:00, Sedat Dilek <sedat.dilek@...il.com> wrote:
>On Wed, Feb 17, 2021 at 1:44 PM Arnaldo Carvalho de Melo
><arnaldo.melo@...il.com> wrote:
>>
>> Em Sat, Feb 13, 2021 at 05:46:48PM +0100, Jiri Olsa escreveu:
>> > Currently when processing DWARF function, we check its entrypoint
>> > against ftrace addresses, assuming that the ftrace address matches
>> > with function's entrypoint.
>> >
>> > This is not the case on some architectures as reported by Nathan
>> > when building kernel on arm [1].
>> >
>> > Fixing the check to take into account the whole function not
>> > just the entrypoint.
>> >
>> > Most of the is_ftrace_func code was contributed by Andrii.
>>
>> Applied locally, will go out after tests,
>>
>
>Hi Arnaldo,
>
>Is it possible to have a pahole version 1.21 with this patch and the
>one from Yonghong Son?
>
>>From my local pahole Git:
>
>$ git log --oneline --no-merges v1.20..
>2f83aefdbddf (for-1.20/btf_encoder-ftrace_elf-clang-jolsa-v2)
>btf_encoder: Match ftrace addresses within elf functions
>f21eafdfc877 (for-1.20/btf_encoder-sanitized_int-clang-yhs-v2)
>btf_encoder: sanitize non-regular int base type
>
>Both patches fixes all issues seen so far with LLVM/Clang >=
>12.0.0-rc1 and DWARF-v5 and BTF (debug-info) and pahole on
>Linux/x86_64 and according to Nathan on Linux/arm64.
>Yesterday, I tried with LLVM/Clang 13-git from <apt.llvm.org>.
>
>BTW, Nick's DWARF-v5 patches are pending in <kbuild.git#kbuild> (see
>[1]).
>
>Personally, I can wait until [1] is in Linus Git.
>
>Please, let me/us know what you are planning.
>( I know it is Linux v5.12 merge-window. )

Sure, next week.

- Arnaldo

>
>Regards,
>- Sedat -
>
>[1]
>https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git/log/?h=kbuild

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