[PATCH 3.16 13/99] perf pmu: Suppress potential format-truncation warning

[Ben Hutchings]

3.16.65-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Ben Hutchings <ben@xxxxxxxxxxxxxxx>

commit 11a64a05dc649815670b1be9fe63d205cb076401 upstream.

Depending on which functions are inlined in util/pmu.c, the snprintf()
calls in perf_pmu__parse_{scale,unit,per_pkg,snapshot}() might trigger a
warning:

  util/pmu.c: In function 'pmu_aliases':
  util/pmu.c:178:31: error: '%s' directive output may be truncated writing up to 255 bytes into a region of size between 0 and 4095 [-Werror=format-truncation=]
    snprintf(path, PATH_MAX, "%s/%s.unit", dir, name);
                               ^~

I found this when trying to build perf from Linux 3.16 with gcc 8.
However I can reproduce the problem in mainline if I force
__perf_pmu__new_alias() to be inlined.

Suppress this by using scnprintf() as has been done elsewhere in perf.

Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20181111184524.fux4taownc6ndbx6@xxxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
[bwh: Dropped the parts that don't apply to 3.16]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 tools/perf/util/pmu.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -107,7 +107,7 @@ static int perf_pmu__parse_scale(struct
 	char path[PATH_MAX];
 	const char *lc;
 
-	snprintf(path, PATH_MAX, "%s/%s.scale", dir, name);
+	scnprintf(path, PATH_MAX, "%s/%s.scale", dir, name);
 
 	fd = open(path, O_RDONLY);
 	if (fd == -1)
@@ -150,7 +150,7 @@ static int perf_pmu__parse_unit(struct p
 	ssize_t sret;
 	int fd;
 
-	snprintf(path, PATH_MAX, "%s/%s.unit", dir, name);
+	scnprintf(path, PATH_MAX, "%s/%s.unit", dir, name);
 
 	fd = open(path, O_RDONLY);
 	if (fd == -1)