netdev - Re: [PATCH 2/2] bpf_encoder: Translate SHN_XINDEX in symbol's st

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Message-ID: <CAEf4BzaKMb-qxnWAMNL94+tseNaJCh3g1NBU4BTwh9ZQ_JVUjg@mail.gmail.com>
Date:   Mon, 25 Jan 2021 15:51:08 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andriin@...com>, dwarves@...r.kernel.org,
        Networking <netdev@...r.kernel.org>, bpf <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>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Mark Wielaard <mjw@...hat.com>
Subject: Re: [PATCH 2/2] bpf_encoder: Translate SHN_XINDEX in symbol's
 st_shndx values

On Sun, Jan 24, 2021 at 2:18 PM Jiri Olsa <jolsa@...nel.org> wrote:
>
> For very large ELF objects (with many sections), we could
> get special value SHN_XINDEX (65535) for symbol's st_shndx.
>
> This patch is adding code to detect the optional extended
> section index table and use it to resolve symbol's section
> index.
>
> Adding elf_symtab__for_each_symbol_index macro that returns
> symbol's section index and usign it in collect functions.
>
> Tested by running pahole on kernel compiled with:
>   make KCFLAGS="-ffunction-sections -fdata-sections" -j$(nproc) vmlinux
>
> and ensure FUNC records are generated and match normal
> build (without above KCFLAGS).
>
> Also bpf selftest passed and generated kernel BTF,
> is same as without the patch.
>
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---

Acked-by: Andrii Nakryiko <andrii@...nel.org>


>  btf_encoder.c | 33 +++++++++++++++++----------------
>  elf_symtab.c  | 41 +++++++++++++++++++++++++++++++++++++++--
>  elf_symtab.h  | 29 +++++++++++++++++++++++++++++
>  3 files changed, 85 insertions(+), 18 deletions(-)
>

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