[PATCH V2 1/9] perf pmu: Add support for PMU capabilities

kan.liang
2020-03-09T17:47:38Z

The PMU capabilities information, which is located at
/sys/bus/event_source/devices/<dev>/caps, is required by perf tool.
For example, the max LBR information is required to stitch LBR call
stack.

Add perf_pmu__caps_parse() to parse the PMU capabilities information.
The information is stored in a list.

Add perf_pmu__scan_caps() to scan the capabilities one by one.

The following patch will store the capabilities information in perf
header.

Reviewed-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
---
tools/perf/util/pmu.c | 87 +++++++++++++++++++++++++++++++++++++++++++
tools/perf/util/pmu.h | 12 ++++++
2 files changed, 99 insertions(+)

diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index 8b99fd312aae..13634ca09096 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -844,6 +844,7 @@ static struct perf_pmu *pmu_lookup(const char *name)

INIT_LIST_HEAD(&pmu->format);
INIT_LIST_HEAD(&pmu->aliases);
+ INIT_LIST_HEAD(&pmu->caps);
list_splice(&format, &pmu->format);
list_splice(&aliases, &pmu->aliases);
list_add_tail(&pmu->list, &pmus);
@@ -1565,3 +1566,89 @@ int perf_pmu__scan_file(struct perf_pmu *pmu, const char *name, const char *fmt,
va_end(args);
return ret;
}
+
+static int perf_pmu__new_caps(struct list_head *list, char *name, char *value)
+{
+ struct perf_pmu_caps *caps;
+
+ caps = zalloc(sizeof(*caps));
+ if (!caps)
+ return -ENOMEM;
+
+ caps->name = strdup(name);
+ caps->value = strndup(value, strlen(value) - 1);
+ list_add_tail(&caps->list, list);
+ return 0;
+}
+
+/*
+ * Reading/parsing the given pmu capabilities, which should be located at:
+ * /sys/bus/event_source/devices/<dev>/caps as sysfs group attributes.
+ * Return the number of capabilities
+ */
+int perf_pmu__caps_parse(struct perf_pmu *pmu)
+{
+ struct stat st;
+ char caps_path[PATH_MAX];
+ const char *sysfs = sysfs__mountpoint();
+ DIR *caps_dir;
+ struct dirent *evt_ent;
+ int nr_caps = 0;
+
+ if (!sysfs)
+ return -1;
+
+ snprintf(caps_path, PATH_MAX,
+ "%s" EVENT_SOURCE_DEVICE_PATH "%s/caps", sysfs, pmu->name);
+
+ if (stat(caps_path, &st) < 0)
+ return 0; /* no error if caps does not exist */
+
+ caps_dir = opendir(caps_path);
+ if (!caps_dir)
+ return -EINVAL;
+
+ while ((evt_ent = readdir(caps_dir)) != NULL) {
+ char path[PATH_MAX + NAME_MAX + 1];
+ char *name = evt_ent->d_name;
+ char value[128];
+ FILE *file;
+
+ if (!strcmp(name, ".") || !strcmp(name, ".."))
+ continue;
+
+ snprintf(path, sizeof(path), "%s/%s", caps_path, name);
+
+ file = fopen(path, "r");
+ if (!file)
+ break;
+
+ if (!fgets(value, sizeof(value), file) ||
+ (perf_pmu__new_caps(&pmu->caps, name, value) < 0)) {
+ fclose(file);
+ break;
+ }
+
+ nr_caps++;
+ fclose(file);
+ }
+
+ closedir(caps_dir);
+
+ return nr_caps;
+}
+
+struct perf_pmu_caps *perf_pmu__scan_caps(struct perf_pmu *pmu,
+ struct perf_pmu_caps *caps)
+{
+ if (!pmu)
+ return NULL;
+
+ if (!caps)
+ caps = list_prepare_entry(caps, &pmu->caps, list);
+
+ list_for_each_entry_continue(caps, &pmu->caps, list)
+ return caps;
+
+ return NULL;
+}
diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
index 6737e3d5d568..a228e27ae462 100644
--- a/tools/perf/util/pmu.h
+++ b/tools/perf/util/pmu.h
@@ -21,6 +21,12 @@ enum {

struct perf_event_attr;

+struct perf_pmu_caps {
+ char *name;
+ char *value;
+ struct list_head list;
+};
+
struct perf_pmu {
char *name;
__u32 type;
@@ -32,6 +38,7 @@ struct perf_pmu {
struct perf_cpu_map *cpus;
struct list_head format; /* HEAD struct perf_pmu_format -> list */
struct list_head aliases; /* HEAD struct perf_pmu_alias -> list */
+ struct list_head caps; /* HEAD struct perf_pmu_caps -> list */
struct list_head list; /* ELEM */
};

@@ -102,4 +109,9 @@ struct pmu_events_map *perf_pmu__find_map(struct perf_pmu *pmu);

int perf_pmu__convert_scale(const char *scale, char **end, double *sval);

+int perf_pmu__caps_parse(struct perf_pmu *pmu);
+
+struct perf_pmu_caps *perf_pmu__scan_caps(struct perf_pmu *pmu,
+ struct perf_pmu_caps *caps);
+
#endif /* __PMU_H */
--
2.17.1