perf tools: Add/use PMU reverse lookup from config to name

Add perf_pmu__name_from_config that does a reverse lookup from a
config number to an alias name. The lookup is expensive as the config
is computed for every alias by filling in a perf_event_attr, but this
is only done when verbose output is enabled. The lookup also only
considers config, and not config1, config2 or config3.

An example of the output:

$ perf stat -vv -e data_read true
...
perf_event_attr:
type 24 (uncore_imc_free_running_0)
size 136
config 0x20ff (data_read)
sample_type IDENTIFIER
read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
disabled 1
inherit 1
exclude_guest 1
...

Committer notes:

Fix the python binding build by adding dummies for not strictly
needed perf_pmu__name_from_config() and perf_pmus__find_by_type().

Signed-off-by: Ian Rogers <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Tested-by: Kan Liang <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: James Clark <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Ravi Bangoria <[e-mail]>
Cc: Yang Jihong <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/perf_event_attr_fprintf.c

···
 }
 #endif
 
-static void __p_config_id(char *buf, size_t size, u32 type, u64 value)
+static void __p_config_id(struct perf_pmu *pmu, char *buf, size_t size, u32 type, u64 value)
 {
+	const char *name = perf_pmu__name_from_config(pmu, value);
+
+	if (name) {
+		print_id_hex(name);
+		return;
+	}
 	switch (type) {
 	case PERF_TYPE_HARDWARE:
 		return __p_config_hw_id(buf, size, value);
···
 #define p_branch_sample_type(val) __p_branch_sample_type(buf, BUF_SIZE, val)
 #define p_read_format(val)	__p_read_format(buf, BUF_SIZE, val)
 #define p_type_id(val)		__p_type_id(pmu, buf, BUF_SIZE, val)
-#define p_config_id(val)	__p_config_id(buf, BUF_SIZE, attr->type, val)
+#define p_config_id(val)	__p_config_id(pmu, buf, BUF_SIZE, attr->type, val)
 
 #define PRINT_ATTRn(_n, _f, _p, _a)			\
 do {							\

tools/perf/util/pmu.c

···
 	zfree(&pmu->id);
 	free(pmu);
 }
+
+const char *perf_pmu__name_from_config(struct perf_pmu *pmu, u64 config)
+{
+	struct perf_pmu_alias *event;
+
+	if (!pmu)
+		return NULL;
+
+	pmu_add_cpu_aliases(pmu);
+	list_for_each_entry(event, &pmu->aliases, list) {
+		struct perf_event_attr attr = {.config = 0,};
+		int ret = perf_pmu__config(pmu, &attr, &event->terms, NULL);
+
+		if (ret == 0 && config == attr.config)
+			return event->name;
+	}
+	return NULL;
+}

tools/perf/util/pmu.h

···
 struct perf_pmu *perf_pmu__create_placeholder_core_pmu(struct list_head *core_pmus);
 void perf_pmu__delete(struct perf_pmu *pmu);
 struct perf_pmu *perf_pmus__find_core_pmu(void);
+const char *perf_pmu__name_from_config(struct perf_pmu *pmu, u64 config);
 
 #endif /* __PMU_H */

tools/perf/util/python.c

···
 	return EOF;
 }
 
+const char *perf_pmu__name_from_config(struct perf_pmu *pmu __maybe_unused, u64 config __maybe_unused)
+{
+	return NULL;
+}
+
+struct perf_pmu *perf_pmus__find_by_type(unsigned int type __maybe_unused)
+{
+	return NULL;
+}
+
 int perf_pmus__num_core_pmus(void)
 {
 	return 1;