[PATCH] perf metricgroup: Fix segmentation fault for metrics with no pmu event

[Jin Yao <yao.jin@linux.intel.com>]

Hit a segmentation fault for DRAM_BW_Use on SKL/KBL.

  # perf stat -M DRAM_BW_Use -a -- sleep 1

  Segmentation fault (core dumped)

  (gdb) backtrace
  #0  __strcmp_sse2_unaligned () at ../sysdeps/x86_64/multiarch/strcmp-sse2-unaligned.S:31
  #1  0x0000555c9facd9ce in find_evsel_group (evlist_used=0x555ca16d09c0, metric_events=0x555ca16e9160, has_constraint=false, metric_no_merge=false,
      pctx=0x555ca16c8ff0, perf_evlist=0x555ca16c5340) at util/metricgroup.c:281
  #2  metricgroup__setup_events (metric_events_list=0x555ca0044378 <stat_config+280>, perf_evlist=0x555ca16c5340, metric_no_merge=<optimized out>,
      groups=0x7ffc599193f0) at util/metricgroup.c:323
  #3  parse_groups (perf_evlist=perf_evlist@entry=0x555ca16c5340, str=str@entry=0x7ffc599205f8 "DRAM_BW_Use", metric_no_group=metric_no_group@entry=false,
      metric_no_merge=metric_no_merge@entry=false, fake_pmu=fake_pmu@entry=0x0, metric_events=metric_events@entry=0x555ca0044378 <stat_config+280>,
      map=0x555ca004e780 <pmu_events_map+768>) at util/metricgroup.c:1235
  #4  0x0000555c9face096 in metricgroup__parse_groups (opt=<optimized out>, str=0x7ffc599205f8 "DRAM_BW_Use", metric_no_group=<optimized out>,
      metric_no_merge=<optimized out>, metric_events=0x555ca0044378 <stat_config+280>) at util/metricgroup.c:1253
  #5  0x0000555c9fbd084e in get_value (p=p@entry=0x7ffc599196b0, opt=0x555ca0043f60 <stat_options+4032>, flags=flags@entry=1) at parse-options.c:251
  #6  0x0000555c9fbd1aa2 in parse_short_opt (options=<optimized out>, p=<optimized out>) at parse-options.c:351
  #7  parse_options_step (usagestr=0x7ffc59919830, options=0x555ca0042fa0 <stat_options>, ctx=0x7ffc599196b0) at parse-options.c:539
  #8  parse_options_subcommand (argc=argc@entry=7, argv=argv@entry=0x7ffc5991e6c0, options=options@entry=0x555ca0042fa0 <stat_options>,
      subcommands=subcommands@entry=0x7ffc59919840, usagestr=usagestr@entry=0x7ffc59919830, flags=flags@entry=2) at parse-options.c:654
  #9  0x0000555c9fa15154 in cmd_stat (argc=7, argv=0x7ffc5991e6c0) at builtin-stat.c:2136
  #10 0x0000555c9fa8bafd in run_builtin (p=0x555ca004df20 <commands+288>, argc=7, argv=0x7ffc5991e6c0) at perf.c:312
  #11 0x0000555c9f9f413a in handle_internal_command (argv=0x7ffc5991e6c0, argc=7) at perf.c:364
  #12 run_argv (argcp=<synthetic pointer>, argv=<synthetic pointer>) at perf.c:408
  #13 main (argc=7, argv=0x7ffc5991e6c0) at perf.c:538

DRAM_BW_Use uses an event 'duration_time' but it doesn't have pmu, so
ev->leader->pmu_name is NULL for this case. See following code piece:

!strcmp(ev->leader->pmu_name,
	metric_events[i]->leader->pmu_name)

It causes the segmentation fault. Now check the pmu_name before strcmp.

Fixes: c2337d67199a("perf metricgroup: Fix metrics using aliases covering multiple PMUs")
Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
---
 tools/perf/util/metricgroup.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
index ee94d3e8dd65..a36a1305c506 100644
--- a/tools/perf/util/metricgroup.c
+++ b/tools/perf/util/metricgroup.c
@@ -280,6 +280,7 @@ static struct evsel *find_evsel_group(struct evlist *perf_evlist,
 			 */
 			if (!has_constraint &&
 			    ev->leader != metric_events[i]->leader &&
+			    ev->leader->pmu_name &&
 			    !strcmp(ev->leader->pmu_name,
 				    metric_events[i]->leader->pmu_name))
 				break;
-- 
2.17.1