[PATCH] perf stat: Fix segfault on armv8_pmu events

From: Namhyung Kim
Date: Wed Oct 07 2020 - 04:13:27 EST


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@entry=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@entry=1, argv=0x30,
argv@entry=0xfffffaea2f90, run_idx=119, run_idx@entry=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@entry=0x9764b8 <commands+288>,
argc=argc@entry=4, argv=argv@entry=0xfffffaea2f90) at perf.c:312
#7 0x00000000004bbb54 in handle_internal_command (argc=argc@entry=4,
argv=argv@entry=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@xxxxxxxxxx>
Tested-by: Barry Song <song.bao.hua@xxxxxxxxxxxxx>
Fixes: 7736627b865d ("perf stat: Use affinity for closing file descriptors")
Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
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