netdev - Re: [PATCH v2 bpf-next] libbpf: support .text sub-calls relocations

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Message-ID: <20200115200516.aqfdmzrszevirsfx@ast-mbp.dhcp.thefacebook.com>
Date:   Wed, 15 Jan 2020 12:05:17 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Andrii Nakryiko <andriin@...com>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org, ast@...com,
        daniel@...earbox.net, yhs@...com, andrii.nakryiko@...il.com,
        kernel-team@...com, Alexei Starovoitov <ast@...nel.org>
Subject: Re: [PATCH v2 bpf-next] libbpf: support .text sub-calls relocations

On Wed, Jan 15, 2020 at 11:08:56AM -0800, Andrii Nakryiko wrote:
> The LLVM patch https://reviews.llvm.org/D72197 makes LLVM emit function call
> relocations within the same section. This includes a default .text section,
> which contains any BPF sub-programs. This wasn't the case before and so libbpf
> was able to get a way with slightly simpler handling of subprogram call
> relocations.
> 
> This patch adds support for .text section relocations. It needs to ensure
> correct order of relocations, so does two passes:
> - first, relocate .text instructions, if there are any relocations in it;
> - then process all the other programs and copy over patched .text instructions
> for all sub-program calls.
> 
> v1->v2:
> - break early once .text program is processed.
> 
> Cc: Yonghong Song <yhs@...com>
> Cc: Alexei Starovoitov <ast@...nel.org>
> Signed-off-by: Andrii Nakryiko <andriin@...com>

Tested with the latest llvm trunk (which points to version 11 already)
and all tests pass.
Applied. Thanks