perf trace: Free syscall->arg_fmt

ASan reports several memory leaks running:

  # perf test "88: Check open filename arg using perf trace + vfs_getname"

The second of these leaks is caused by the arg_fmt field of syscall not
being deallocated.

This patch adds a new function syscall__exit which is called on all
syscalls.table entries in trace__exit, which will free the arg_fmt
field.

Signed-off-by: Riccardo Mancini <rickyman7@gmail.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/d68f25c043d30464ac9fa79c3399e18f429bca82.1626343282.git.rickyman7@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-trace.c

@@ -2266,6 +2266,14 @@ static void *syscall__augmented_args(struct syscall *sc, struct perf_sample *sam
 	return augmented_args;
 }
 
+static void syscall__exit(struct syscall *sc)
+{
+	if (!sc)
+		return;
+
+	free(sc->arg_fmt);
+}
+
 static int trace__sys_enter(struct trace *trace, struct evsel *evsel,
 			    union perf_event *event __maybe_unused,
 			    struct perf_sample *sample)
@@ -4703,9 +4711,15 @@ out:
 
 static void trace__exit(struct trace *trace)
 {
+	int i;
+
 	strlist__delete(trace->ev_qualifier);
 	free(trace->ev_qualifier_ids.entries);
-	free(trace->syscalls.table);
+	if (trace->syscalls.table) {
+		for (i = 0; i <= trace->sctbl->syscalls.max_id; i++)
+			syscall__exit(&trace->syscalls.table[i]);
+		free(trace->syscalls.table);
+	}
 	syscalltbl__delete(trace->sctbl);
 	zfree(&trace->perfconfig_events);
 }