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Date: Fri, 30 Jul 2021 09:43:09 +0800
From: "Jin, Yao" <yao.jin@...ux.intel.com>
To: Riccardo Mancini <rickyman7@...il.com>
Cc: acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
mingo@...hat.com, alexander.shishkin@...ux.intel.com,
Linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
ak@...ux.intel.com, Kan Liang <kan.liang@...ux.intel.com>
Subject: Re: [PATCH v2 1/2] perf pmu: Add PMU alias support
Hi Riccardo,
On 7/29/2021 9:13 PM, Riccardo Mancini wrote:
> Hi,
>
> On Thu, 2021-07-29 at 15:06 +0800, Jin Yao wrote:
>> From: Kan Liang <kan.liang@...ux.intel.com>
>>
>> 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@...ux.intel.com>
>> Signed-off-by: Jin Yao <yao.jin@...ux.intel.com>
>> Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
>> ---
>> 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").
>
Yes, fgets should be better. I will use 'fgets(buf, sizeof(buf), file)' instead in v3.
>> +
>> + 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.
>
Yes, strictly we should check the return value, I will fix that.
Thanks
Jin Yao
> 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 */
>
>
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