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

Arnaldo Carvalho de Melo
2020-03-10T13:20:53Z

Em Mon, Mar 09, 2020 at 10:46:31AM -0700, kan.liang@linux.intel.com escreveu:
> From: Kan Liang <kan.liang@linux.intel.com>
>
> 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;
> +

So here you check if zalloc fails and returns a proper error

> + caps->name = strdup(name);
> + caps->value = strndup(value, strlen(value) - 1);

But then you don't check strdup()?

> + 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
>

--

- Arnaldo