perf events: Prefer union over variable length array

It is possible for casts to introduce alignment issues, prefer a union
for perf_record_event_update.

Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Bayduraev <alexey.v.bayduraev@linux.intel.com>
Cc: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Cc: Colin Ian King <colin.king@intel.com>
Cc: Dave Marchevsky <davemarchevsky@fb.com>
Cc: German Gomez <german.gomez@arm.com>
Cc: Gustavo A. R. Silva <gustavoars@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Kees Kook <keescook@chromium.org>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Riccardo Mancini <rickyman7@gmail.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20220614143353.1559597-6-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 13 insertions, 23 deletions

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index c30c29c51410..98dfaf84bd13 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -4295,8 +4295,6 @@ out:
 size_t perf_event__fprintf_event_update(union perf_event *event, FILE *fp)
 {
 	struct perf_record_event_update *ev = &event->event_update;
-	struct perf_record_event_update_scale *ev_scale;
-	struct perf_record_event_update_cpus *ev_cpus;
 	struct perf_cpu_map *map;
 	size_t ret;
 
@@ -4304,20 +4302,18 @@ size_t perf_event__fprintf_event_update(union perf_event *event, FILE *fp)
 
 	switch (ev->type) {
 	case PERF_EVENT_UPDATE__SCALE:
-		ev_scale = (struct perf_record_event_update_scale *)ev->data;
-		ret += fprintf(fp, "... scale: %f\n", ev_scale->scale);
+		ret += fprintf(fp, "... scale: %f\n", ev->scale.scale);
 		break;
 	case PERF_EVENT_UPDATE__UNIT:
-		ret += fprintf(fp, "... unit:  %s\n", ev->data);
+		ret += fprintf(fp, "... unit:  %s\n", ev->unit);
 		break;
 	case PERF_EVENT_UPDATE__NAME:
-		ret += fprintf(fp, "... name:  %s\n", ev->data);
+		ret += fprintf(fp, "... name:  %s\n", ev->name);
 		break;
 	case PERF_EVENT_UPDATE__CPUS:
-		ev_cpus = (struct perf_record_event_update_cpus *)ev->data;
 		ret += fprintf(fp, "... ");
 
-		map = cpu_map__new_data(&ev_cpus->cpus);
+		map = cpu_map__new_data(&ev->cpus.cpus);
 		if (map)
 			ret += cpu_map__fprintf(map, fp);
 		else
@@ -4374,8 +4370,6 @@ int perf_event__process_event_update(struct perf_tool *tool __maybe_unused,
 				     struct evlist **pevlist)
 {
 	struct perf_record_event_update *ev = &event->event_update;
-	struct perf_record_event_update_scale *ev_scale;
-	struct perf_record_event_update_cpus *ev_cpus;
 	struct evlist *evlist;
 	struct evsel *evsel;
 	struct perf_cpu_map *map;
@@ -4395,19 +4389,17 @@ int perf_event__process_event_update(struct perf_tool *tool __maybe_unused,
 	switch (ev->type) {
 	case PERF_EVENT_UPDATE__UNIT:
 		free((char *)evsel->unit);
-		evsel->unit = strdup(ev->data);
+		evsel->unit = strdup(ev->unit);
 		break;
 	case PERF_EVENT_UPDATE__NAME:
 		free(evsel->name);
-		evsel->name = strdup(ev->data);
+		evsel->name = strdup(ev->name);
 		break;
 	case PERF_EVENT_UPDATE__SCALE:
-		ev_scale = (struct perf_record_event_update_scale *)ev->data;
-		evsel->scale = ev_scale->scale;
+		evsel->scale = ev->scale.scale;
 		break;
 	case PERF_EVENT_UPDATE__CPUS:
-		ev_cpus = (struct perf_record_event_update_cpus *)ev->data;
-		map = cpu_map__new_data(&ev_cpus->cpus);
+		map = cpu_map__new_data(&ev->cpus.cpus);
 		if (map) {
 			perf_cpu_map__put(evsel->core.own_cpus);
 			evsel->core.own_cpus = map;
diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
index 538790758e24..851d11a64b0d 100644
--- a/tools/perf/util/synthetic-events.c
+++ b/tools/perf/util/synthetic-events.c
@@ -1955,7 +1955,7 @@ int perf_event__synthesize_event_update_unit(struct perf_tool *tool, struct evse
 	if (ev == NULL)
 		return -ENOMEM;
 
-	strlcpy(ev->data, evsel->unit, size + 1);
+	strlcpy(ev->unit, evsel->unit, size + 1);
 	err = process(tool, (union perf_event *)ev, NULL, NULL);
 	free(ev);
 	return err;
@@ -1972,8 +1972,7 @@ int perf_event__synthesize_event_update_scale(struct perf_tool *tool, struct evs
 	if (ev == NULL)
 		return -ENOMEM;
 
-	ev_data = (struct perf_record_event_update_scale *)ev->data;
-	ev_data->scale = evsel->scale;
+	ev->scale.scale = evsel->scale;
 	err = process(tool, (union perf_event *)ev, NULL, NULL);
 	free(ev);
 	return err;
@@ -1990,7 +1989,7 @@ int perf_event__synthesize_event_update_name(struct perf_tool *tool, struct evse
 	if (ev == NULL)
 		return -ENOMEM;
 
-	strlcpy(ev->data, evsel->name, len + 1);
+	strlcpy(ev->name, evsel->name, len + 1);
 	err = process(tool, (union perf_event *)ev, NULL, NULL);
 	free(ev);
 	return err;
@@ -1999,7 +1998,7 @@ int perf_event__synthesize_event_update_name(struct perf_tool *tool, struct evse
 int perf_event__synthesize_event_update_cpus(struct perf_tool *tool, struct evsel *evsel,
 					     perf_event__handler_t process)
 {
-	size_t size = sizeof(struct perf_record_event_update);
+	size_t size = sizeof(struct perf_event_header) + sizeof(u64) + sizeof(u64);
 	struct perf_record_event_update *ev;
 	int max, err;
 	u16 type;
@@ -2016,8 +2015,7 @@ int perf_event__synthesize_event_update_cpus(struct perf_tool *tool, struct evse
 	ev->type	= PERF_EVENT_UPDATE__CPUS;
 	ev->id		= evsel->core.id[0];
 
-	cpu_map_data__synthesize((struct perf_record_cpu_map_data *)ev->data,
-				 evsel->core.own_cpus, type, max);
+	cpu_map_data__synthesize(&ev->cpus.cpus, evsel->core.own_cpus, type, max);
 
 	err = process(tool, (union perf_event *)ev, NULL, NULL);
 	free(ev);