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Message-ID: <20191211160036.GV2974@aurel32.net> Date: Wed, 11 Dec 2019 17:00:36 +0100 From: Aurelien Jarno <aurelien@...el32.net> To: Justin Forbes <jmforbes@...uxtx.org> Cc: Thadeu Lima de Souza Cascardo <cascardo@...onical.com>, 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>, debian-kernel@...ts.debian.org Subject: Re: [PATCH] libbpf: fix readelf output parsing on powerpc with recent binutils On 2019-12-11 09:33, Justin Forbes wrote: > On Tue, Dec 10, 2019 at 4:26 PM Thadeu Lima de Souza Cascardo > <cascardo@...onical.com> wrote: > > > > On Tue, Dec 10, 2019 at 12:58:33PM -0600, Justin Forbes wrote: > > > 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 > > > > Well, I ended up debugging this same issue and had the same fix as Jarno's when > > I noticed his fix was already applied. > > > > I just installed a system with the latest binutils, 2.33.1, and it still breaks > > without such fix. Can you tell what is the output of the following command on > > your system? > > > > readelf -s --wide tools/lib/bpf/sharedobjs/libbpf-in.o | cut -d "@" -f1 | sed 's/_v[0-9]_[0-9]_[0-9].*//' | awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $0}' > > > > readelf -s --wide tools/lib/bpf/sharedobjs/libbpf-in.o | cut -d "@" > -f1 | sed 's/_v[0-9]_[0-9]_[0-9].*//' | awk '/GLOBAL/ && /DEFAULT/ && > !/UND/ {print $0}' > 373: 00000000000141bc 1376 FUNC GLOBAL DEFAULT 1 libbpf_num_possible_cpus [<localentry>: 8] > 375: 000000000001869c 176 FUNC GLOBAL DEFAULT 1 btf__free [<localentry>: 8] It seems that in your case the localentry part is added after the symbol name. That doesn't match what is done in upstream binutils: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=blob;f=binutils/readelf.c;hb=refs/heads/master#l11485 Which version of binutils are you using? It looks like your version has been modified to workaround this exact issue. -- Aurelien Jarno GPG: 4096R/1DDD8C9B aurelien@...el32.net http://www.aurel32.net
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