linux-kernel - Re: [PATCH] libbpf: fix readelf output parsing on powerpc with recent binutils

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Message-ID: <CAFxkdAqg6RaGbRrNN3e_nHfHFR-xxzZgjhi5AnppTxxwdg0VyQ@mail.gmail.com>
Date:   Tue, 10 Dec 2019 12:58:33 -0600
From:   Justin Forbes <jmforbes@...uxtx.org>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Aurelien Jarno <aurelien@...el32.net>,
        LKML <linux-kernel@...r.kernel.org>,
        linuxppc-dev@...ts.ozlabs.org, debian-kernel@...ts.debian.org,
        Alexei Starovoitov <ast@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        "open list:BPF (Safe dynamic programs and tools)" 
        <netdev@...r.kernel.org>,
        "open list:BPF (Safe dynamic programs and tools)" 
        <bpf@...r.kernel.org>
Subject: Re: [PATCH] libbpf: fix readelf output parsing on powerpc with recent binutils

On Mon, Dec 2, 2019 at 3:37 AM Daniel Borkmann <daniel@...earbox.net> wrote:
>
> On Mon, Dec 02, 2019 at 04:53:26PM +1100, Michael Ellerman wrote:
> > Aurelien Jarno <aurelien@...el32.net> writes:
> > > On powerpc with recent versions of binutils, readelf outputs an extra
> > > field when dumping the symbols of an object file. For example:
> > >
> > >     35: 0000000000000838    96 FUNC    LOCAL  DEFAULT [<localentry>: 8]     1 btf_is_struct
> > >
> > > The extra "[<localentry>: 8]" prevents the GLOBAL_SYM_COUNT variable to
> > > be computed correctly and causes the checkabi target to fail.
> > >
> > > Fix that by looking for the symbol name in the last field instead of the
> > > 8th one. This way it should also cope with future extra fields.
> > >
> > > Signed-off-by: Aurelien Jarno <aurelien@...el32.net>
> > > ---
> > >  tools/lib/bpf/Makefile | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > Thanks for fixing that, it's been on my very long list of test failures
> > for a while.
> >
> > Tested-by: Michael Ellerman <mpe@...erman.id.au>
>
> Looks good & also continues to work on x86. Applied, thanks!

This actually seems to break horribly on PPC64le with binutils 2.33.1
resulting in:
Warning: Num of global symbols in sharedobjs/libbpf-in.o (32) does NOT
match with num of versioned symbols in libbpf.so (184). Please make
sure all LIBBPF_API symbols are versioned in libbpf.map.

This is the only arch that fails, with x86/arm/aarch64/s390 all
building fine.  Reverting this patch allows successful build across
all arches.

Justin