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

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Date:   Mon, 02 Dec 2019 16:53:26 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Aurelien Jarno <aurelien@...el32.net>, linux-kernel@...r.kernel.org
Cc:     linuxppc-dev@...ts.ozlabs.org, debian-kernel@...ts.debian.org,
        Aurelien Jarno <aurelien@...el32.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        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

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>

cheers

> diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
> index 99425d0be6ff..333900cf3f4f 100644
> --- a/tools/lib/bpf/Makefile
> +++ b/tools/lib/bpf/Makefile
> @@ -147,7 +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].*//' | \
> -			   awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$8}' | \
> +			   awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$NF}' | \
>  			   sort -u | wc -l)
>  VERSIONED_SYM_COUNT = $(shell readelf -s --wide $(OUTPUT)libbpf.so | \
>  			      grep -Eo '[^ ]+@...BPF_' | cut -d@ -f1 | sort -u | wc -l)
> @@ -216,7 +216,7 @@ check_abi: $(OUTPUT)libbpf.so
>  		     "versioned in $(VERSION_SCRIPT)." >&2;		 \
>  		readelf -s --wide $(OUTPUT)libbpf-in.o |		 \
>  		    cut -d "@" -f1 | sed 's/_v[0-9]_[0-9]_[0-9].*//' |	 \
> -		    awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$8}'|   \
> +		    awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$NF}'|  \
>  		    sort -u > $(OUTPUT)libbpf_global_syms.tmp;		 \
>  		readelf -s --wide $(OUTPUT)libbpf.so |			 \
>  		    grep -Eo '[^ ]+@...BPF_' | cut -d@ -f1 |		 \
> -- 
> 2.24.0