Re: [PATCH] perf tools: Don't write to evsel if parser doesn't collect evsel

From: Wangnan (F)
Date: Wed Sep 02 2015 - 02:54:40 EST


Sorry, forget to CC kernel mailing list...

On 2015/9/2 14:49, Wang Nan wrote:
If parse_events__scanner() collects no entry, perf_evlist__last(evlist)
is invalid.

Although it shouldn't happen at this point, before calling
perf_evlist__last(), we should ensure the list is not empty for safety
reason.

There are 3 places need this checking:

1. Before setting cmdline_group_boundary;
2. Before __perf_evlist__set_leader();
3. In foreach_evsel_in_last_glob.

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Zefan Li <lizefan@xxxxxxxxxx>
Cc: pi3orama@xxxxxxx
---

Merge all 3 list_empty() test together into one patch.

Add warning messages.

Improve commit message.

---
tools/perf/util/parse-events.c | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index d826e6f..069848d 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -793,6 +793,11 @@ void parse_events__set_leader(char *name, struct list_head *list)
{
struct perf_evsel *leader;
+ if (list_empty(list)) {
+ __WARN_printf("WARNING: failed to set leader: empty list");
+ return;
+ }
+
__perf_evlist__set_leader(list);
leader = list_entry(list->next, struct perf_evsel, node);
leader->group_name = name ? strdup(name) : NULL;
@@ -1143,10 +1148,15 @@ int parse_events(struct perf_evlist *evlist, const char *str,
int entries = data.idx - evlist->nr_entries;
struct perf_evsel *last;
+ if (!list_empty(&data.list)) {
+ last = list_entry(data.list.prev,
+ struct perf_evsel, node);
+ last->cmdline_group_boundary = true;
+ } else
+ __WARN_printf("WARNING: event parser found nothing");
+
perf_evlist__splice_list_tail(evlist, &data.list, entries);
evlist->nr_groups += data.nr_groups;
- last = perf_evlist__last(evlist);
- last->cmdline_group_boundary = true;
return 0;
}
@@ -1252,7 +1262,13 @@ foreach_evsel_in_last_glob(struct perf_evlist *evlist,
struct perf_evsel *last = NULL;
int err;
- if (evlist->nr_entries > 0)
+ /*
+ * Don't return when list_empty, give func a chance to report
+ * error when it found last == NULL.
+ *
+ * So no need to WARN here, let *func do this.
+ */
+ if (!list_empty(&evlist->entries))
last = perf_evlist__last(evlist);
do {


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