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Date:   Thu, 20 Aug 2020 10:54:29 -0700
From:   Yonghong Song <>
To:     Mark Wielaard <>,
        Fāng-ruì Sòng <>,
        Jiri Olsa <>
CC:     Nick Desaulniers <>,
        Alexei Starovoitov <>,
        Daniel Borkmann <>,
        Nick Clifton <>,
        Jesper Dangaard Brouer <>,
        Network Development <>,
        bpf <>, Martin KaFai Lau <>,
        Song Liu <>,
        Andrii Nakryiko <>,
        John Fastabend <>,
        KP Singh <>,
        clang-built-linux <>
Subject: Re: [PATCH bpf-next] tools/resolve_btfids: Fix sections with wrong

On 8/20/20 10:36 AM, Mark Wielaard wrote:
> Hi
> On Thu, 2020-08-20 at 08:51 -0700, Yonghong Song wrote:
>>>> Do you think we could skip these .debug_* sections somehow in elf
>>>> parsing in resolve_btfids? resolve_btfids does not need to read
>>>> these sections. This way, no need to change their alignment
>>>> either.
>>> The issue is that elfutils libelf will not allow writing out the
>>> section when it notices the sh_addralign field is setup wrongly.
>> Maybe resolve_btfids can temporarily change sh_addralign to 4/8
>> before elf manipulation (elf_write) to make libelf happy.
>> After all elf_write is done, change back to whatever the
>> original value (1). Does this work?
> Unfortunately no, because there is no elf_write, elf_update is how you
> write out the ELF image to disc.
> Since the code is using ELF_F_LAYOUT this will not change the actual
> layout of the ELF image if that is what you are worried about.
> And the workaround to set sh_addralign correctly before calling
> elf_update is precisely what the fix in elfutils libelf will do itself
> in the next release. Also binutils ld has been fixed to setup
> sh_addralign to 4/8 as appropriate now (in git).

Sounds good then.
Thanks for fixing the issue in upstream, both libelf and binutils!

> Cheers,
> Mark

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