perf unwind: Use dynamic register set for DWARF unwind

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!
  $

Reviewed-by: Leo Yan <leo.yan@linaro.org>
Signed-off-by: James Clark <james.clark@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: German Gomez <german.gomez@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.garry@huawei.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Link: https://lore.kernel.org/r/20220525154114.718321-4-james.clark@arm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Author: James-A-Clark

tools/perf/util/evsel.c

@@ -897,7 +897,7 @@ 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;

tools/perf/util/python-ext-sources

@@ -38,5 +38,6 @@ util/units.c
 util/affinity.c
 util/rwsem.c
 util/hashmap.c
+util/perf_regs.c
 util/pmu-hybrid.c
 util/fncache.c