Re: [PATCH v2 1/2] perf pmu: Add PMU alias support
From: Riccardo Mancini
Date: Thu Jul 29 2021 - 09:13:20 EST
Hi,
On Thu, 2021-07-29 at 15:06 +0800, Jin Yao wrote:
> From: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
>
> A perf uncore PMU may have two PMU names, a real name and an alias. The
> alias is exported at /sys/bus/event_source/devices/uncore_*/alias.
> The perf tool should support the alias as well.
>
> Add alias_name in the struct perf_pmu to store the alias. For the PMU
> which doesn't have an alias. It's NULL.
>
> Introduce two X86 specific functions to retrieve the real name and the
> alias separately.
>
> Only go through the sysfs to retrieve the mapping between the real name
> and the alias once. The result is cached in a list, uncore_pmu_list.
>
> Nothing changed for the other ARCHs.
>
> With the patch, the perf tool can monitor the PMU with either the real
> name or the alias.
>
> Use the real name,
> $ perf stat -e uncore_cha_2/event=1/ -x,
> 4044879584,,uncore_cha_2/event=1/,2528059205,100.00,,
>
> Use the alias,
> $ perf stat -e uncore_type_0_2/event=1/ -x,
> 3659675336,,uncore_type_0_2/event=1/,2287306455,100.00,,
>
> Co-developed-by: Jin Yao <yao.jin@xxxxxxxxxxxxxxx>
> Signed-off-by: Jin Yao <yao.jin@xxxxxxxxxxxxxxx>
> Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> ---
> v2:
> - No change.
>
> tools/perf/arch/x86/util/pmu.c | 109 ++++++++++++++++++++++++++++++++-
> tools/perf/util/parse-events.y | 3 +-
> tools/perf/util/pmu.c | 26 +++++++-
> tools/perf/util/pmu.h | 5 ++
> 4 files changed, 138 insertions(+), 5 deletions(-)
>
> diff --git a/tools/perf/arch/x86/util/pmu.c b/tools/perf/arch/x86/util/pmu.c
> index d48d608517fd..bb79b1d19b96 100644
> --- a/tools/perf/arch/x86/util/pmu.c
> +++ b/tools/perf/arch/x86/util/pmu.c
> @@ -1,12 +1,28 @@
> // SPDX-License-Identifier: GPL-2.0
> #include <string.h>
> -
> +#include <stdio.h>
> +#include <sys/types.h>
> +#include <dirent.h>
> +#include <fcntl.h>
> #include <linux/stddef.h>
> #include <linux/perf_event.h>
> +#include <linux/zalloc.h>
> +#include <api/fs/fs.h>
>
> #include "../../../util/intel-pt.h"
> #include "../../../util/intel-bts.h"
> #include "../../../util/pmu.h"
> +#include "../../../util/fncache.h"
> +
> +#define TEMPLATE_ALIAS "%s/bus/event_source/devices/%s/alias"
> +
> +struct perf_pmu_alias_name {
> + char *name;
> + char *alias;
> + struct list_head list;
> +};
> +
> +static LIST_HEAD(pmu_alias_name_list);
>
> struct perf_event_attr *perf_pmu__get_default_config(struct perf_pmu *pmu
> __maybe_unused)
> {
> @@ -18,3 +34,94 @@ struct perf_event_attr *perf_pmu__get_default_config(struct
> perf_pmu *pmu __mayb
> #endif
> return NULL;
> }
> +
> +static void setup_pmu_alias_list(void)
> +{
> + char path[PATH_MAX];
> + DIR *dir;
> + struct dirent *dent;
> + const char *sysfs = sysfs__mountpoint();
> + struct perf_pmu_alias_name *pmu;
> + char buf[MAX_PMU_NAME_LEN];
> + FILE *file;
> +
> + if (!sysfs)
> + return;
> +
> + snprintf(path, PATH_MAX,
> + "%s" EVENT_SOURCE_DEVICE_PATH, sysfs);
> +
> + dir = opendir(path);
> + if (!dir)
> + return;
> +
> + while ((dent = readdir(dir))) {
> + if (!strcmp(dent->d_name, ".") ||
> + !strcmp(dent->d_name, ".."))
> + continue;
> +
> + snprintf(path, PATH_MAX,
> + TEMPLATE_ALIAS, sysfs, dent->d_name);
> +
> + if (!file_available(path))
> + continue;
> +
> + file = fopen(path, "r");
> + if (!file)
> + continue;
> +
> + if (fscanf(file, "%s", buf) != 1)
> + continue;
Using fscanf with "%s" can lead to a buffer overflow.
It's better to use fgets, if possible, or to specify a maximum length (better if
through a macro, e.g. "%" STR(MAX_PMU_NAME_LEN) "s").
> +
> + pmu = zalloc(sizeof(*pmu));
> + if (!pmu)
> + continue;
> +
> + pmu->alias = strdup(buf);
> + if (!pmu->alias) {
> + free(pmu);
> + continue;
> + }
> + pmu->name = strdup(dent->d_name);
The result of strdup is not checked.
It's also probably better to return an error in case of ENOMEM, instead of
continuing iteration, as also previous checks do.
Thanks,
Riccardo
> + list_add_tail(&pmu->list, &pmu_alias_name_list);
> + fclose(file);
> + }
> +
> + closedir(dir);
> +}
> +
> +static char *__pmu_find_real_name(const char *name)
> +{
> + struct perf_pmu_alias_name *pmu;
> +
> + list_for_each_entry(pmu, &pmu_alias_name_list, list) {
> + if (!strcmp(name, pmu->alias))
> + return strdup(pmu->name);
> + }
> +
> + return strdup(name);
> +}
> +
> +char *pmu_find_real_name(const char *name)
> +{
> + static bool cached_list;
> +
> + if (cached_list)
> + return __pmu_find_real_name(name);
> +
> + setup_pmu_alias_list();
> + cached_list = true;
> +
> + return __pmu_find_real_name(name);
> +}
> +
> +char *pmu_find_alias_name(const char *name)
> +{
> + struct perf_pmu_alias_name *pmu;
> +
> + list_for_each_entry(pmu, &pmu_alias_name_list, list) {
> + if (!strcmp(name, pmu->name))
> + return strdup(pmu->alias);
> + }
> + return NULL;
> +}
> diff --git a/tools/perf/util/parse-events.y b/tools/perf/util/parse-events.y
> index 9321bd0e2f76..d94e48e1ff9b 100644
> --- a/tools/perf/util/parse-events.y
> +++ b/tools/perf/util/parse-events.y
> @@ -316,7 +316,8 @@ event_pmu_name opt_pmu_config
> if (!strncmp(name, "uncore_", 7) &&
> strncmp($1, "uncore_", 7))
> name += 7;
> - if (!perf_pmu__match(pattern, name, $1)) {
> + if (!perf_pmu__match(pattern, name, $1) ||
> + !perf_pmu__match(pattern, pmu->alias_name, $1)) {
> if (parse_events_copy_term_list(orig_terms,
> &terms))
> CLEANUP_YYABORT;
> if (!parse_events_add_pmu(_parse_state, list,
> pmu->name, terms, true, false))
> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
> index 44b90d638ad5..cc9af7942e7b 100644
> --- a/tools/perf/util/pmu.c
> +++ b/tools/perf/util/pmu.c
> @@ -944,13 +944,28 @@ static int pmu_max_precise(const char *name)
> return max_precise;
> }
>
> -static struct perf_pmu *pmu_lookup(const char *name)
> +char * __weak
> +pmu_find_real_name(const char *name)
> +{
> + return strdup(name);
> +}
> +
> +char * __weak
> +pmu_find_alias_name(const char *name __maybe_unused)
> +{
> + return NULL;
> +}
> +
> +static struct perf_pmu *pmu_lookup(const char *lookup_name)
> {
> struct perf_pmu *pmu;
> + char *name;
> LIST_HEAD(format);
> LIST_HEAD(aliases);
> __u32 type;
>
> + name = pmu_find_real_name(lookup_name);
> +
> /*
> * The pmu data we store & need consists of the pmu
> * type value and format definitions. Load both right
> @@ -973,7 +988,8 @@ static struct perf_pmu *pmu_lookup(const char *name)
> return NULL;
>
> pmu->cpus = pmu_cpumask(name);
> - pmu->name = strdup(name);
> + pmu->name = name;
> + pmu->alias_name = pmu_find_alias_name(name);
> pmu->type = type;
> pmu->is_uncore = pmu_is_uncore(name);
> if (pmu->is_uncore)
> @@ -1003,7 +1019,8 @@ static struct perf_pmu *pmu_find(const char *name)
> struct perf_pmu *pmu;
>
> list_for_each_entry(pmu, &pmus, list)
> - if (!strcmp(pmu->name, name))
> + if (!strcmp(pmu->name, name) ||
> + (pmu->alias_name && !strcmp(pmu->alias_name, name)))
> return pmu;
>
> return NULL;
> @@ -1898,6 +1915,9 @@ bool perf_pmu__has_hybrid(void)
>
> int perf_pmu__match(char *pattern, char *name, char *tok)
> {
> + if (!name)
> + return -1;
> +
> if (fnmatch(pattern, name, 0))
> return -1;
>
> diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
> index 926da483a141..f6ca9f6a06ef 100644
> --- a/tools/perf/util/pmu.h
> +++ b/tools/perf/util/pmu.h
> @@ -21,6 +21,7 @@ enum {
> #define PERF_PMU_FORMAT_BITS 64
> #define EVENT_SOURCE_DEVICE_PATH "/bus/event_source/devices/"
> #define CPUS_TEMPLATE_CPU "%s/bus/event_source/devices/%s/cpus"
> +#define MAX_PMU_NAME_LEN 128
>
> struct perf_event_attr;
>
> @@ -32,6 +33,7 @@ struct perf_pmu_caps {
>
> struct perf_pmu {
> char *name;
> + char *alias_name; /* PMU alias name */
> char *id;
> __u32 type;
> bool selectable;
> @@ -135,4 +137,7 @@ void perf_pmu__warn_invalid_config(struct perf_pmu *pmu,
> __u64 config,
> bool perf_pmu__has_hybrid(void);
> int perf_pmu__match(char *pattern, char *name, char *tok);
>
> +char *pmu_find_real_name(const char *name);
> +char *pmu_find_alias_name(const char *name);
> +
> #endif /* __PMU_H */