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

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Message-ID: <20200310130644.GC15931@kernel.org>
Date:   Tue, 10 Mar 2020 10:06:44 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     kan.liang@...ux.intel.com
Cc:     jolsa@...hat.com, peterz@...radead.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org, namhyung@...nel.org,
        adrian.hunter@...el.com, mathieu.poirier@...aro.org,
        ravi.bangoria@...ux.ibm.com, alexey.budankov@...ux.intel.com,
        vitaly.slobodskoy@...el.com, pavel.gerasimov@...el.com,
        mpe@...erman.id.au, eranian@...gle.com, ak@...ux.intel.com
Subject: Re: [PATCH V2 1/9] perf pmu: Add support for PMU capabilities

Em Mon, Mar 09, 2020 at 10:46:31AM -0700, kan.liang@...ux.intel.com escreveu:
> From: Kan Liang <kan.liang@...ux.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@...ux.intel.com>
> Signed-off-by: Kan Liang <kan.liang@...ux.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