perf stat: fix NULL pointer reference bug with event unit

This patch fixes a problem with the handling of the newly introduced
optional event unit. The following cmdline caused a segfault:

 $ perf stat -e cpu/event-0x3c/ ls

This patch fixes the problem with the default setting for alias->unit
which was eventually causing the segfault.

Signed-off-by: Stephane Eranian <eranian@google.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1389972846-6566-2-git-send-email-eranian@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

3 files changed, 22 insertions, 6 deletions

diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index a7f1b6a91fdd..d248fca6d7ed 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -635,7 +635,7 @@ int parse_events_add_pmu(struct list_head *list, int *idx,
         struct perf_event_attr attr;
         struct perf_pmu *pmu;
         struct perf_evsel *evsel;
-        char *unit;
+        const char *unit;
         double scale;
 
         pmu = perf_pmu__find(name);
diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index d9cab4d27192..b752ecb40d86 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -105,7 +105,7 @@ static int perf_pmu__parse_scale(struct perf_pmu_alias *alias, char *dir, char *
         char scale[128];
         int fd, ret = -1;
         char path[PATH_MAX];
-        char *lc;
+        const char *lc;
 
         snprintf(path, PATH_MAX, "%s/%s.scale", dir, name);
 
@@ -609,7 +609,7 @@ static struct perf_pmu_alias *pmu_find_alias(struct perf_pmu *pmu,
 
 
 static int check_unit_scale(struct perf_pmu_alias *alias,
-                            char **unit, double *scale)
+                            const char **unit, double *scale)
 {
         /*
          * Only one term in event definition can
@@ -634,14 +634,18 @@ static int check_unit_scale(struct perf_pmu_alias *alias,
  * defined for the alias
  */
 int perf_pmu__check_alias(struct perf_pmu *pmu, struct list_head *head_terms,
-                          char **unit, double *scale)
+                          const char **unit, double *scale)
 {
         struct parse_events_term *term, *h;
         struct perf_pmu_alias *alias;
         int ret;
 
+        /*
+         * Mark unit and scale as not set
+         * (different from default values, see below)
+         */
         *unit   = NULL;
-        *scale  = 0;
+        *scale  = 0.0;
 
         list_for_each_entry_safe(term, h, head_terms, list) {
                 alias = pmu_find_alias(pmu, term);
@@ -658,6 +662,18 @@ int perf_pmu__check_alias(struct perf_pmu *pmu, struct list_head *head_terms,
                 list_del(&term->list);
                 free(term);
         }
+
+        /*
+         * if no unit or scale foundin aliases, then
+         * set defaults as for evsel
+         * unit cannot left to NULL
+         */
+        if (*unit == NULL)
+                *unit   = "";
+
+        if (*scale == 0.0)
+                *scale  = 1.0;
+
         return 0;
 }
 
diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
index 9183380e2038..8b64125a9281 100644
--- a/tools/perf/util/pmu.h
+++ b/tools/perf/util/pmu.h
@@ -29,7 +29,7 @@ int perf_pmu__config_terms(struct list_head *formats,
                            struct perf_event_attr *attr,
                            struct list_head *head_terms);
 int perf_pmu__check_alias(struct perf_pmu *pmu, struct list_head *head_terms,
-                          char **unit, double *scale);
+                          const char **unit, double *scale);
 struct list_head *perf_pmu__alias(struct perf_pmu *pmu,
                                   struct list_head *head_terms);
 int perf_pmu_wrap(void);