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

From: Justin Forbes <jmforbes@linuxtx.org>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>,
	Aurelien Jarno <aurelien@aurel32.net>,
	LKML <linux-kernel@vger.kernel.org>,
	linuxppc-dev@lists.ozlabs.org, debian-kernel@lists.debian.org,
	Alexei Starovoitov <ast@kernel.org>,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Yonghong Song <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>,
	"open list:BPF (Safe dynamic programs and tools)" 
	<netdev@vger.kernel.org>,
	"open list:BPF (Safe dynamic programs and tools)" 
	<bpf@vger.kernel.org>
Subject: Re: [PATCH] libbpf: fix readelf output parsing on powerpc with recent binutils
Date: Tue, 10 Dec 2019 12:58:33 -0600	[thread overview]
Message-ID: <CAFxkdAqg6RaGbRrNN3e_nHfHFR-xxzZgjhi5AnppTxxwdg0VyQ@mail.gmail.com> (raw)
In-Reply-To: <20191202093752.GA1535@localhost.localdomain>

On Mon, Dec 2, 2019 at 3:37 AM Daniel Borkmann <daniel@iogearbox.net> wrote:
>
> On Mon, Dec 02, 2019 at 04:53:26PM +1100, Michael Ellerman wrote:
> > Aurelien Jarno <aurelien@aurel32.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@aurel32.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@ellerman.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