perf pmus: Add notion of default PMU for JSON events

JSON events created in pmu-events.c by jevents.py may not specify a
PMU they are associated with, in which case it is implied that it is
the first core PMU. Care is needed to select this for regular 'cpu',
s390 'cpum_cf' and ARMs many names as at the point the name is first
needed the core PMUs list hasn't been initialized. Add a helper in
perf_pmus to create this value, in the worst case by scanning sysfs.

v2. Add missing close if fdopendir fails.

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Thomas Richter <tmricht@linux.ibm.com>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: James Clark <james.clark@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Link: https://lore.kernel.org/r/20230623043843.4080180-1-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

tools/perf/util/pmu.c

@@ -741,9 +741,11 @@ static bool pmu_uncore_alias_match(const char *pmu_name, const char *name)
 }
 
 struct pmu_add_cpu_aliases_map_data {
+	/* List being added to. */
 	struct list_head *head;
-	const char *name;
+	/* If a pmu_event lacks a given PMU the default used. */
-	const char *cpu_name;
+	char *default_pmu_name;
+	/* The PMU that we're searching for events for. */
 	struct perf_pmu *pmu;
 };
 
@@ -752,37 +754,32 @@ static int pmu_add_cpu_aliases_map_callback(const struct pmu_event *pe,
 					void *vdata)
 {
 	struct pmu_add_cpu_aliases_map_data *data = vdata;
-	const char *pname = pe->pmu ? pe->pmu : data->cpu_name;
+	const char *pname = pe->pmu ?: data->default_pmu_name;
 
-	if (data->pmu->is_uncore && pmu_uncore_alias_match(pname, data->name))
+	if (!strcmp(pname, data->pmu->name) ||
-		goto new_alias;
+	    (data->pmu->is_uncore && pmu_uncore_alias_match(pname, data->pmu->name))) {
-
+		/* need type casts to override 'const' */
-	if (strcmp(pname, data->name))
+		__perf_pmu__new_alias(data->head, -1, (char *)pe->name, (char *)pe->desc,
-		return 0;
+				      (char *)pe->event, pe);
-
+	}
-new_alias:
-	/* need type casts to override 'const' */
-	__perf_pmu__new_alias(data->head, -1, (char *)pe->name, (char *)pe->desc,
-			      (char *)pe->event, pe);
 	return 0;
 }
 
 /*
- * From the pmu_events_map, find the table of PMU events that corresponds
+ * From the pmu_events_table, find the events that correspond to the given
- * to the current running CPU. Then, add all PMU events from that table
+ * PMU and add them to the list 'head'.
- * as aliases.
  */
 void pmu_add_cpu_aliases_table(struct list_head *head, struct perf_pmu *pmu,
-			       const struct pmu_events_table *table)
+			const struct pmu_events_table *table)
 {
 	struct pmu_add_cpu_aliases_map_data data = {
 		.head = head,
-		.name = pmu->name,
+		.default_pmu_name = perf_pmus__default_pmu_name(),
-		.cpu_name = is_sysfs_pmu_core(pmu->name) ? pmu->name : "cpu",
 		.pmu = pmu,
 	};
 
 	pmu_events_table_for_each_event(table, pmu_add_cpu_aliases_map_callback, &data);
+	free(data.default_pmu_name);
 }
 
 static void pmu_add_cpu_aliases(struct list_head *head, struct perf_pmu *pmu)

tools/perf/util/pmus.c

@@ -137,8 +137,10 @@ static void pmu_read_sysfs(bool core_only)
 		return;
 
 	dir = fdopendir(fd);
-	if (!dir)
+	if (!dir) {
+		close(fd);
 		return;
+	}
 
 	while ((dent = readdir(dir))) {
 		if (!strcmp(dent->d_name, ".") || !strcmp(dent->d_name, ".."))
@@ -524,6 +526,39 @@ bool perf_pmus__supports_extended_type(void)
 	return perf_pmus__do_support_extended_type;
 }
 
+char *perf_pmus__default_pmu_name(void)
+{
+	int fd;
+	DIR *dir;
+	struct dirent *dent;
+	char *result = NULL;
+
+	if (!list_empty(&core_pmus))
+		return strdup(list_first_entry(&core_pmus, struct perf_pmu, list)->name);
+
+	fd = perf_pmu__event_source_devices_fd();
+	if (fd < 0)
+		return strdup("cpu");
+
+	dir = fdopendir(fd);
+	if (!dir) {
+		close(fd);
+		return strdup("cpu");
+	}
+
+	while ((dent = readdir(dir))) {
+		if (!strcmp(dent->d_name, ".") || !strcmp(dent->d_name, ".."))
+			continue;
+		if (is_pmu_core(dent->d_name)) {
+			result = strdup(dent->d_name);
+			break;
+		}
+	}
+
+	closedir(dir);
+	return result ?: strdup("cpu");
+}
+
 struct perf_pmu *evsel__find_pmu(const struct evsel *evsel)
 {
 	struct perf_pmu *pmu = evsel->pmu;

tools/perf/util/pmus.h

@@ -20,5 +20,6 @@ void perf_pmus__print_pmu_events(const struct print_callbacks *print_cb, void *p
 bool perf_pmus__have_event(const char *pname, const char *name);
 int perf_pmus__num_core_pmus(void);
 bool perf_pmus__supports_extended_type(void);
+char *perf_pmus__default_pmu_name(void);
 
 #endif /* __PMUS_H */