linux-kernel - Re: [PATCH v2 0/2] perf: arm64: Tools support for Dwarf unwinding through SVE functions

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Date:   Tue, 17 May 2022 11:58:38 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     James Clark <james.clark@....com>
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 v2 0/2] perf: arm64: Tools support for Dwarf unwinding
 through SVE functions

Em Tue, May 17, 2022 at 11:20:01AM +0100, James Clark escreveu:
> Changes since v1:
> 
>   * Split patchset into kernel side and Perf tool changes

Thanks, now I'll wait for the kernel side to be merged.

- Arnaldo
 
> 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
> James
> 
> James Clark (4):
>   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/perf_regs.c                   |  2 +
>  5 files changed, 45 insertions(+), 73 deletions(-)
> 
> -- 
> 2.28.0

-- 

- Arnaldo