linux-kernel - Re: [PATCH v3 0/5] perf: arm64: Tools support for Dwarf unwinding through SVE functions

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Message-ID: <6f2e16b5-7fec-3d54-21ef-dd42acfab553@arm.com>
Date:   Fri, 23 Sep 2022 11:34:59 +0100
From:   James Clark <james.clark@....com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        broonie@...nel.org, german.gomez@....com, leo.yan@...aro.org,
        mathieu.poirier@...aro.org, john.garry@...wei.com,
        Will Deacon <will@...nel.org>,
        Mike Leach <mike.leach@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 0/5] perf: arm64: Tools support for Dwarf unwinding
 through SVE functions



On 26/05/2022 16:23, Arnaldo Carvalho de Melo wrote:
> Em Wed, May 25, 2022 at 04:41:09PM +0100, James Clark escreveu:
>> Changes since v2:
>>   * Add commit to fix header include path to use Perf's copy
>>   * Apply Leo's review tags
>>
>> When SVE registers are pushed onto the stack the VG register is required to
>> unwind because the stack offsets would vary by the SVE register width at the
>> time when the sample was taken.
>>
>> The patches ("[PATCH v2 0/2] perf: arm64: Kernel support for Dwarf unwinding
>> through SVE functions") add support for sampling the VG register to the kernel
>> and the docs. This is the patchset to add support to userspace perf.
>>
>> A small change is also required to libunwind or libdw depending on which
>> unwinder is used, and these will be published later. Without these changes Perf
>> continues to work with both libraries, although the VG register is still not
>> used for unwinding. 
> 
> Thanks, applied.
> 
> - Arnaldo

Hi Arnaldo,

Will has applied the kernel side here:
https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/commit/?h=for-next/perf&id=cbb0c02caf4bd98b9e0cd6d7420734b8e9a35703

There was a small change in the formatting in perf_regs.h, but the
values are all the same. So in theory it's fine to leave Perf's copy
until the next update, although it is a bit weird.

Thanks
James

> 
>  
>> Thanks
>> James
>>
>> James Clark (5):
>>   perf tools: arm64: Use perf's copy of kernel headers
>>   perf tools: arm64: Copy perf_regs.h from the kernel
>>   perf tools: Use dynamic register set for Dwarf unwind
>>   perf tools: arm64: Decouple Libunwind register names from Perf
>>   perf tools: arm64: Add support for VG register
>>
>>  tools/arch/arm64/include/uapi/asm/perf_regs.h |  7 +-
>>  tools/perf/arch/arm64/util/perf_regs.c        | 34 +++++++++
>>  tools/perf/arch/arm64/util/unwind-libunwind.c | 73 +------------------
>>  tools/perf/util/evsel.c                       |  2 +-
>>  tools/perf/util/libunwind/arm64.c             |  2 +-
>>  tools/perf/util/perf_regs.c                   |  2 +
>>  6 files changed, 46 insertions(+), 74 deletions(-)
>>
>> -- 
>> 2.28.0
>