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

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Message-ID: <ea3953ba-6ee2-d565-c8ed-be3e32c9d70f@fb.com>
Date:   Wed, 15 Jan 2020 19:29:57 +0000
From:   Yonghong Song <yhs@...com>
To:     Andrii Nakryiko <andriin@...com>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        "daniel@...earbox.net" <daniel@...earbox.net>
CC:     "andrii.nakryiko@...il.com" <andrii.nakryiko@...il.com>,
        Kernel Team <Kernel-team@...com>,
        Alexei Starovoitov <ast@...nel.org>
Subject: Re: [PATCH v2 bpf-next] libbpf: support .text sub-calls relocations



On 1/15/20 11:08 AM, Andrii Nakryiko wrote:
> The LLVM patch https://urldefense.proofpoint.com/v2/url?u=https-3A__reviews.llvm.org_D72197&d=DwIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=DA8e1B5r073vIqRrFz7MRA&m=Pw2Bljqg1D5zPVHNmG5W7MTL_jxP_myfOOC4O-YSp_M&s=SUm2Y_ugh5NW-P8Iek263sULvuebiPSzWwtJ9J1Z330&e=  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>

Thanks for the quick fix!
Acked-by: Yonghong Song <yhs@...com>