perf cpumap: Use existing allocator to avoid using malloc

Use the existing allocator for perf_cpu_map to avoid use of raw malloc.
This could cause an issue in later commits where the size of
perf_cpu_map is changed.

No functional changes.
Signed-off-by: James Clark <james.clark@arm.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: John Garry <john.garry@huawei.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Link: https://lore.kernel.org/r/20201126141328.6509-3-james.clark@arm.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/cpumap.c

@@ -132,15 +132,16 @@ int cpu_map__build_map(struct perf_cpu_map *cpus, struct perf_cpu_map **res,
 		       int (*f)(struct perf_cpu_map *map, int cpu, void *data),
 		       void *data)
 {
-	struct perf_cpu_map *c;
 	int nr = cpus->nr;
+	struct perf_cpu_map *c = perf_cpu_map__empty_new(nr);
 	int cpu, s1, s2;
 
-	/* allocate as much as possible */
-	c = calloc(1, sizeof(*c) + nr * sizeof(int));
 	if (!c)
 		return -1;
 
+	/* Reset size as it may only be partially filled */
+	c->nr = 0;
+
 	for (cpu = 0; cpu < nr; cpu++) {
 		s1 = f(cpus, cpu, data);
 		for (s2 = 0; s2 < c->nr; s2++) {
@@ -155,7 +156,6 @@ int cpu_map__build_map(struct perf_cpu_map *cpus, struct perf_cpu_map **res,
 	/* ensure we process id in increasing order */
 	qsort(c->map, c->nr, sizeof(int), cmp_ids);
 
-	refcount_set(&c->refcnt, 1);
 	*res = c;
 	return 0;
 }