linux-kernel - [PATCH] perf stat: Fix segfault on armv8

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Message-Id: <20201007081311.1831003-1-namhyung@kernel.org>
Date:   Wed,  7 Oct 2020 17:13:11 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Wei Li <liwei391@...wei.com>,
        Barry Song <song.bao.hua@...ilicon.com>
Subject: [PATCH] perf stat: Fix segfault on armv8_pmu events

It was reported that perf stat crashed when using with armv8_pmu (cpu)
events with the task mode.  As perf stat uses an empty cpu map for
task mode but armv8_pmu has its own cpu mask, it confused which map
should use when accessing file descriptors and caused segfaults:

  (gdb) bt
  #0  0x0000000000603fc8 in perf_evsel__close_fd_cpu (evsel=<optimized out>,
      cpu=<optimized out>) at evsel.c:122
  #1  perf_evsel__close_cpu (evsel=evsel@...ry=0x716e950, cpu=7) at evsel.c:156
  #2  0x00000000004d4718 in evlist__close (evlist=0x70a7cb0) at util/evlist.c:1242
  #3  0x0000000000453404 in __run_perf_stat (argc=3, argc@...ry=1, argv=0x30,
      argv@...ry=0xfffffaea2f90, run_idx=119, run_idx@...ry=1701998435)
      at builtin-stat.c:929
  #4  0x0000000000455058 in run_perf_stat (run_idx=1701998435, argv=0xfffffaea2f90,
      argc=1) at builtin-stat.c:947
  #5  cmd_stat (argc=1, argv=0xfffffaea2f90) at builtin-stat.c:2357
  #6  0x00000000004bb888 in run_builtin (p=p@...ry=0x9764b8 <commands+288>,
      argc=argc@...ry=4, argv=argv@...ry=0xfffffaea2f90) at perf.c:312
  #7  0x00000000004bbb54 in handle_internal_command (argc=argc@...ry=4,
      argv=argv@...ry=0xfffffaea2f90) at perf.c:364
  #8  0x0000000000435378 in run_argv (argcp=<synthetic pointer>,
      argv=<synthetic pointer>) at perf.c:408
  #9  main (argc=4, argv=0xfffffaea2f90) at perf.c:538

To fix this, I simply used the given cpu map unless the evsel actually
is not a system-wide event (like uncore events).

Reported-by: Wei Li <liwei391@...wei.com>
Tested-by: Barry Song <song.bao.hua@...ilicon.com>
Fixes: 7736627b865d ("perf stat: Use affinity for closing file descriptors")
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/lib/perf/evlist.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/lib/perf/evlist.c b/tools/lib/perf/evlist.c
index 2208444ecb44..cfcdbd7be066 100644
--- a/tools/lib/perf/evlist.c
+++ b/tools/lib/perf/evlist.c
@@ -45,6 +45,9 @@ static void __perf_evlist__propagate_maps(struct perf_evlist *evlist,
 	if (!evsel->own_cpus || evlist->has_user_cpus) {
 		perf_cpu_map__put(evsel->cpus);
 		evsel->cpus = perf_cpu_map__get(evlist->cpus);
+	} else if (!evsel->system_wide && perf_cpu_map__empty(evlist->cpus)) {
+		perf_cpu_map__put(evsel->cpus);
+		evsel->cpus = perf_cpu_map__get(evlist->cpus);
 	} else if (evsel->cpus != evsel->own_cpus) {
 		perf_cpu_map__put(evsel->cpus);
 		evsel->cpus = perf_cpu_map__get(evsel->own_cpus);
-- 
2.28.0.806.g8561365e88-goog