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Message-ID: <20250501184143.873536-1-thomas.falcon@intel.com>
Date: Thu, 1 May 2025 13:41:43 -0500
From: Thomas Falcon <thomas.falcon@...el.com>
To: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>,
Ian Rogers <irogers@...gle.com>,
Adrian Hunter <adrian.hunter@...el.com>,
Kan Liang <kan.liang@...ux.intel.com>
Cc: linux-kernel@...r.kernel.org,
linux-perf-users@...r.kernel.org,
Thomas Falcon <thomas.falcon@...el.com>
Subject: [PATCH] perf top: populate PMU capabilities data in perf_env
Calling perf top with brach filters enabled on Intel hybrid CPU's
with branch counter event logging support results in a segfault.
$ ./perf top -e '{cpu_core/cpu-cycles/,cpu_core/event=0xc6,umask=0x3,\
frontend=0x11,name=frontend_retired_dsb_miss/}' -j any,counter
perf: Segmentation fault
-------- backtrace --------
./perf() [0x55f460]
/lib64/libc.so.6(+0x1a050) [0x7fd8be227050]
./perf() [0x57b4a7]
./perf() [0x561e5a]
./perf() [0x604a81]
./perf() [0x4395b5]
./perf() [0x601732]
./perf() [0x439bc1]
./perf() [0x5d35b3]
./perf() [0x43936c]
/lib64/libc.so.6(+0x70ba8) [0x7fd8be27dba8]
/lib64/libc.so.6(+0xf4b8c) [0x7fd8be301b8c]
The cause is that perf_env__find_br_cntr_info tries to access a
null pointer pmu_caps in the perf_env struct. Presumably this would
also be an issue when using the cpu_pmu_caps structure available for
homogeneous core CPU's.
Fix this by populating cpu_pmu_caps and pmu_caps structures with
values from sysfs when calling perf top with branch stack sampling
enabled.
Signed-off-by: Thomas Falcon <thomas.falcon@...el.com>
---
tools/perf/builtin-top.c | 8 +++
tools/perf/util/env.c | 114 +++++++++++++++++++++++++++++++++++++++
tools/perf/util/env.h | 1 +
3 files changed, 123 insertions(+)
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 1061f4eebc3f..c2688e4ef3c4 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -1729,6 +1729,14 @@ int cmd_top(int argc, const char **argv)
if (opts->branch_stack && callchain_param.enabled)
symbol_conf.show_branchflag_count = true;
+ if (opts->branch_stack) {
+ status = perf_env__read_core_pmu_caps(&perf_env);
+ if (status) {
+ pr_err("PMU capability data is not available\n");
+ goto out_delete_evlist;
+ }
+ }
+
sort__mode = SORT_MODE__TOP;
/* display thread wants entries to be collapsed in a different tree */
perf_hpp_list.need_collapse = 1;
diff --git a/tools/perf/util/env.c b/tools/perf/util/env.c
index 36411749e007..37ed6dc52cf3 100644
--- a/tools/perf/util/env.c
+++ b/tools/perf/util/env.c
@@ -416,6 +416,120 @@ static int perf_env__read_nr_cpus_avail(struct perf_env *env)
return env->nr_cpus_avail ? 0 : -ENOENT;
}
+static int __perf_env__read_core_pmu_caps(struct perf_pmu *pmu,
+ int *nr_caps, char ***caps,
+ unsigned int *max_branches,
+ unsigned int *br_cntr_nr,
+ unsigned int *br_cntr_width)
+{
+ struct perf_pmu_caps *pcaps = NULL;
+ char *ptr, **tmp;
+ int ret = 0;
+
+ *nr_caps = 0;
+ *caps = NULL;
+
+ if (!pmu->nr_caps)
+ return 0;
+
+ *caps = zalloc(sizeof(char *) * pmu->nr_caps);
+ if (!*caps)
+ return -ENOMEM;
+
+ tmp = *caps;
+ list_for_each_entry(pcaps, &pmu->caps, list) {
+
+ if (asprintf(&ptr, "%s=%s", pcaps->name, pcaps->value) < 0) {
+ ret = -ENOMEM;
+ goto error;
+ }
+
+ *tmp++ = ptr;
+
+ if (!strcmp(pcaps->name, "branches"))
+ *max_branches = atoi(pcaps->value);
+
+ if (!strcmp(pcaps->name, "branch_counter_nr"))
+ *br_cntr_nr = atoi(pcaps->value);
+
+ if (!strcmp(pcaps->name, "branch_counter_width"))
+ *br_cntr_width = atoi(pcaps->value);
+ }
+ *nr_caps = pmu->nr_caps;
+ return 0;
+error:
+ while (tmp-- != *caps)
+ free(*tmp);
+ free(*caps);
+ *caps = NULL;
+ *nr_caps = 0;
+ return ret;
+}
+
+int perf_env__read_core_pmu_caps(struct perf_env *env)
+{
+ struct perf_pmu *pmu = NULL;
+ struct pmu_caps *pmu_caps;
+ int nr_pmu = 0, i = 0, j;
+ int ret;
+
+ nr_pmu = perf_pmus__num_core_pmus();
+
+ if (!nr_pmu)
+ return -ENODEV;
+
+ if (nr_pmu == 1) {
+ pmu = perf_pmus__scan_core(NULL);
+ if (!pmu)
+ return -ENODEV;
+ ret = perf_pmu__caps_parse(pmu);
+ if (ret < 0)
+ return ret;
+ return __perf_env__read_core_pmu_caps(pmu, &env->nr_cpu_pmu_caps,
+ &env->cpu_pmu_caps,
+ &env->max_branches,
+ &env->br_cntr_nr,
+ &env->br_cntr_width);
+ }
+
+ pmu_caps = zalloc(sizeof(*pmu_caps) * nr_pmu);
+ if (!pmu_caps)
+ return -ENOMEM;
+
+ while ((pmu = perf_pmus__scan_core(pmu)) != NULL) {
+ if (perf_pmu__caps_parse(pmu) <= 0)
+ continue;
+ ret = __perf_env__read_core_pmu_caps(pmu, &pmu_caps[i].nr_caps,
+ &pmu_caps[i].caps,
+ &pmu_caps[i].max_branches,
+ &pmu_caps[i].br_cntr_nr,
+ &pmu_caps[i].br_cntr_width);
+ if (ret)
+ goto error;
+
+ pmu_caps[i].pmu_name = strdup(pmu->name);
+ if (!pmu_caps[i].pmu_name) {
+ ret = -ENOMEM;
+ goto error;
+ }
+ i++;
+ }
+
+ env->nr_pmus_with_caps = nr_pmu;
+ env->pmu_caps = pmu_caps;
+
+ return 0;
+error:
+ for (i = 0; i < nr_pmu; i++) {
+ for (j = 0; j < pmu_caps[i].nr_caps; j++)
+ free(pmu_caps[i].caps[j]);
+ free(pmu_caps[i].caps);
+ free(pmu_caps[i].pmu_name);
+ }
+ free(pmu_caps);
+ return ret;
+}
+
const char *perf_env__raw_arch(struct perf_env *env)
{
return env && !perf_env__read_arch(env) ? env->arch : "unknown";
diff --git a/tools/perf/util/env.h b/tools/perf/util/env.h
index d90e343cf1fa..135a1f714905 100644
--- a/tools/perf/util/env.h
+++ b/tools/perf/util/env.h
@@ -152,6 +152,7 @@ struct btf_node;
extern struct perf_env perf_env;
+int perf_env__read_core_pmu_caps(struct perf_env *env);
void perf_env__exit(struct perf_env *env);
int perf_env__kernel_is_64_bit(struct perf_env *env);
--
2.49.0
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