[PATCH v1] perf metrics: Avoid segv with --topdown

[Ian Rogers]

Some metrics may not have a metric_group which can result in segvs
with "perf stat --topdown". Add a condition for the no metric_group
case.

Fixes: 1647cd5b8802 ("perf stat: Implement --topdown using json metrics")
Reported-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
 tools/perf/util/metricgroup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
index 4e7d41d285b4..5e9c657dd3f7 100644
--- a/tools/perf/util/metricgroup.c
+++ b/tools/perf/util/metricgroup.c
@@ -1672,7 +1672,7 @@ static int metricgroup__topdown_max_level_callback(const struct pmu_metric *pm,
 {
 	unsigned int *max_level = data;
 	unsigned int level;
-	const char *p = strstr(pm->metric_group, "TopdownL");
+	const char *p = strstr(pm->metric_group ?: "", "TopdownL");
 
 	if (!p || p[8] == '\0')
 		return 0;
-- 
2.40.1.606.ga4b1b128d6-goog