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

[Liang, Kan]

On 3/10/2020 9:06 AM, Arnaldo Carvalho de Melo wrote:
> Em Mon, Mar 09, 2020 at 10:46:31AM -0700, kan.liang@xxxxxxxxxxxxxxx escreveu:
> > From: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> >
> > 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@xxxxxxxxxxxxxxx>
> > Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> > ---
> >   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()?

Right, I should check strdup(), otherwise the capability information may 
be incomplete. I will fix it in V3.

Thanks,
Kan

> > +	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