linux-kernel - Re: [PATCH] scripts/faddr2line: Fix regression in name resolution on ppc64le

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Message-ID: <0f4decac-1349-3ceb-246c-e648364d797f@csgroup.eu>
Date:   Mon, 14 Nov 2022 12:21:33 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Ingo Molnar <mingo@...hat.com>
CC:     Peter Zijlstra <peterz@...radead.org>,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
Subject: Re: [PATCH] scripts/faddr2line: Fix regression in name resolution on
 ppc64le

Gentle ping ... Can this fix be merged ?

Thanks

Le 30/09/2022 à 12:09, Naveen N. Rao a écrit :
> Thadeu Lima de Souza Cascardo wrote:
>> On Tue, Sep 27, 2022 at 01:22:11PM +0530, Srikar Dronamraju wrote:
>>> Commit 1d1a0e7c5100 ("scripts/faddr2line: Fix overlapping text 
>>> section failures")
>>> can cause scripts/faddr2line to fail on ppc64le machines on few
>>> distributions, while working on other distributions. The failure can be
>>> attributed to difference in readelf output on various distributions.
>>>
>>> $ ./scripts/faddr2line vmlinux find_busiest_group+0x00
>>> no match for find_busiest_group+0x00
>>>
>>> Expected output was:
>>> $ ./scripts/faddr2line vmlinux find_busiest_group+0x00
>>> find_busiest_group+0x00/0x3d0:
>>> find_busiest_group at kernel/sched/fair.c:9595
>>>
>>> On ppc64le, readelf adds localentry tag before the symbol name on few
>>> distributions and adds the localentry tag after the symbol name on few
>>> other distributions. This problem has been discussed in the reference
>>> URL given below. This problem can be overcome by filtering out
>>> localentry tags in readelf output. Similar fixes are already present in
>>> kernel by way of commits:
>>>
>>> 1fd6cee127e2 ("libbpf: Fix VERSIONED_SYM_COUNT number parsing")
>>> aa915931ac3e ("libbpf: Fix readelf output parsing for Fedora")
>>>
>>> Fixes: 1d1a0e7c5100 ("scripts/faddr2line: Fix overlapping text 
>>> section failures")
>>> Reference: https://lore.kernel.org/bpf/20191211160133.GB4580@calabresa/
>>> Cc: "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
>>> Cc: Jiri Olsa <jolsa@...nel.org>
>>> Cc: Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
>>
>> Reviewed-by: Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
>>
>> The other instances of readelf --wide on faddr2line use 
>> --section-headers and
>> should not required the same mangling.
> 
> There's one usage of readelf with --file-header in faddr2line which also 
> doesn't need this. The extra information being printed is from st_other 
> and is very specific to the symbol table.
> 
> Acked-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
> 
> 
> - Naveen
>