Re: [PATCH v1 4/6] perf tools: Use dynamic register set for Dwarf unwind

From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: James Clark <james.clark@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
	broonie@kernel.org, german.gomez@arm.com,
	John Garry <john.garry@huawei.com>, Will Deacon <will@kernel.org>,
	Mathieu Poirier <mathieu.poirier@linaro.org>,
	Leo Yan <leo.yan@linaro.org>, Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@kernel.org>, Namhyung Kim <namhyung@kernel.org>,
	linux-doc@vger.kernel.org
Subject: Re: [PATCH v1 4/6] perf tools: Use dynamic register set for Dwarf unwind
Date: Thu, 26 May 2022 12:44:33 -0300	[thread overview]
Message-ID: <Yo+gYbLNnYGOPzGs@kernel.org> (raw)
In-Reply-To: <20220509144257.1623063-5-james.clark@arm.com>

Em Mon, May 09, 2022 at 03:42:52PM +0100, James Clark escreveu:
> Architectures can detect availability of extra registers at
> runtime so use this more complete set for unwinding. This
> will include the VG register on arm64 in a later commit.
> 
> If the function isn't implemented then PERF_REGS_MASK is
> returned and there is no change.

Committer notes:

Added util/perf_regs.c to tools/perf/util/python-ext-sources so that
'perf test python' passes, i.e. the perf python binding has all the
symbols it needs, addressing:

  $ perf test -v python
   19: 'import perf' in python                                         :
  --- start ---
  test child forked, pid 2037817
  python usage test: "echo "import sys ; sys.path.append('/tmp/build/perf/python'); import perf" | '/usr/bin/python3' "
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  ImportError: /tmp/build/perf/python/perf.cpython-310-x86_64-linux-gnu.so: undefined symbol: arch__user_reg_mask
  test child finished with -1
  ---- end ----
  'import perf' in python: FAILED!
  $

> Signed-off-by: James Clark <james.clark@arm.com>
> ---
>  tools/perf/util/evsel.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index d38722560e80..a881784da966 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -875,7 +875,7 @@ static void __evsel__config_callchain(struct evsel *evsel, struct record_opts *o
>  					   "specifying a subset with --user-regs may render DWARF unwinding unreliable, "
>  					   "so the minimal registers set (IP, SP) is explicitly forced.\n");
>  			} else {
> -				attr->sample_regs_user |= PERF_REGS_MASK;
> +				attr->sample_regs_user |= arch__user_reg_mask();
>  			}
>  			attr->sample_stack_user = param->dump_size;
>  			attr->exclude_callchain_user = 1;
> -- 
> 2.28.0

-- 

- Arnaldo

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