linux-kernel - Re: [PATCH] libbpf: Fix readelf output parsing for Fedora

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Date:   Fri, 13 Dec 2019 09:02:19 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
Cc:     Justin Forbes <jmforbes@...uxtx.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Song Liu <songliubraving@...com>,
        Andrii Nakryiko <andriin@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:BPF (Safe dynamic programs and tools)" 
        <netdev@...r.kernel.org>, Yonghong Song <yhs@...com>,
        "open list:BPF (Safe dynamic programs and tools)" 
        <bpf@...r.kernel.org>, linuxppc-dev@...ts.ozlabs.org,
        Martin KaFai Lau <kafai@...com>,
        Aurelien Jarno <aurelien@...el32.net>,
        debian-kernel@...ts.debian.org
Subject: Re: [PATCH] libbpf: Fix readelf output parsing for Fedora

On Fri, Dec 13, 2019 at 2:11 AM Thadeu Lima de Souza Cascardo
<cascardo@...onical.com> wrote:
>
> Fedora binutils has been patched to show "other info" for a symbol at the
> end of the line. This was done in order to support unmaintained scripts
> that would break with the extra info. [1]
>
> [1] https://src.fedoraproject.org/rpms/binutils/c/b8265c46f7ddae23a792ee8306fbaaeacba83bf8
>
> This in turn has been done to fix the build of ruby, because of checksec.
> [2] Thanks Michael Ellerman for the pointer.
>
> [2] https://bugzilla.redhat.com/show_bug.cgi?id=1479302
>
> As libbpf Makefile is not unmaintained, we can simply deal with either
> output format, by just removing the "other info" field, as it always comes
> inside brackets.
>
> Cc: Aurelien Jarno <aurelien@...el32.net>
> Fixes: 3464afdf11f9 (libbpf: Fix readelf output parsing on powerpc with recent binutils)
> Reported-by: Justin Forbes <jmforbes@...uxtx.org>
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
> ---

I was briefly playing with it and trying to make it use nm to dump
symbols, instead of parsing more human-oriented output of readelf, but
somehow nm doesn't output symbols with @@LIBBPF.* suffix at the end,
so I just gave up. So I think this one is good.

This should go through bpf-next tree.

Acked-by: Andrii Nakryiko <andriin@...com>


>  tools/lib/bpf/Makefile | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
> index defae23a0169..23ae06c43d08 100644
> --- a/tools/lib/bpf/Makefile
> +++ b/tools/lib/bpf/Makefile
> @@ -147,6 +147,7 @@ TAGS_PROG := $(if $(shell which etags 2>/dev/null),etags,ctags)
>
>  GLOBAL_SYM_COUNT = $(shell readelf -s --wide $(BPF_IN_SHARED) | \
>                            cut -d "@" -f1 | sed 's/_v[0-9]_[0-9]_[0-9].*//' | \
> +                          sed 's/\[.*\]//' | \
>                            awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$NF}' | \
>                            sort -u | wc -l)
>  VERSIONED_SYM_COUNT = $(shell readelf -s --wide $(OUTPUT)libbpf.so | \
> @@ -213,6 +214,7 @@ check_abi: $(OUTPUT)libbpf.so
>                      "versioned in $(VERSION_SCRIPT)." >&2;              \
>                 readelf -s --wide $(BPF_IN_SHARED) |                     \
>                     cut -d "@" -f1 | sed 's/_v[0-9]_[0-9]_[0-9].*//' |   \
> +                   sed 's/\[.*\]//' |                                   \
>                     awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$NF}'|  \
>                     sort -u > $(OUTPUT)libbpf_global_syms.tmp;           \
>                 readelf -s --wide $(OUTPUT)libbpf.so |                   \
> --
> 2.24.0
>