[<prev] [next>] [day] [month] [year] [list]
Message-ID: <20250508163127.726660-1-thomas.falcon@intel.com>
Date: Thu, 8 May 2025 11:31:27 -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 v2] perf top: populate PMU capabilities data in perf_env
Calling perf top with branch filters enabled on Intel CPU's
with branch counters logging (A.K.A LBR event logging [1]) support
results in a segfault.
Thread 27 "perf" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fffafff76c0 (LWP 949003)]
perf_env__find_br_cntr_info (env=0xf66dc0 <perf_env>, nr=0x0, width=0x7fffafff62c0) at util/env.c:653
653 *width = env->cpu_pmu_caps ? env->br_cntr_width :
(gdb) bt
#0 perf_env__find_br_cntr_info (env=0xf66dc0 <perf_env>, nr=0x0, width=0x7fffafff62c0) at util/env.c:653
#1 0x00000000005b1599 in symbol__account_br_cntr (branch=0x7fffcc3db580, evsel=0xfea2d0, offset=12, br_cntr=8) at util/annotate.c:345
#2 0x00000000005b17fb in symbol__account_cycles (addr=5658172, start=5658160, sym=0x7fffcc0ee420, cycles=539, evsel=0xfea2d0, br_cntr=8) at util/annotate.c:389
#3 0x00000000005b1976 in addr_map_symbol__account_cycles (ams=0x7fffcd7b01d0, start=0x7fffcd7b02b0, cycles=539, evsel=0xfea2d0, br_cntr=8) at util/annotate.c:422
#4 0x000000000068d57f in hist__account_cycles (bs=0x110d288, al=0x7fffafff6540, sample=0x7fffafff6760, nonany_branch_mode=false, total_cycles=0x0, evsel=0xfea2d0) at util/hist.c:2850
#5 0x0000000000446216 in hist_iter__top_callback (iter=0x7fffafff6590, al=0x7fffafff6540, single=true, arg=0x7fffffff9e00) at builtin-top.c:737
#6 0x0000000000689787 in hist_entry_iter__add (iter=0x7fffafff6590, al=0x7fffafff6540, max_stack_depth=127, arg=0x7fffffff9e00) at util/hist.c:1359
#7 0x0000000000446710 in perf_event__process_sample (tool=0x7fffffff9e00, event=0x110d250, evsel=0xfea2d0, sample=0x7fffafff6760, machine=0x108c968) at builtin-top.c:845
#8 0x0000000000447735 in deliver_event (qe=0x7fffffffa120, qevent=0x10fc200) at builtin-top.c:1211
#9 0x000000000064ccae in do_flush (oe=0x7fffffffa120, show_progress=false) at util/ordered-events.c:245
#10 0x000000000064d005 in __ordered_events__flush (oe=0x7fffffffa120, how=OE_FLUSH__TOP, timestamp=0) at util/ordered-events.c:324
#11 0x000000000064d0ef in ordered_events__flush (oe=0x7fffffffa120, how=OE_FLUSH__TOP) at util/ordered-events.c:342
#12 0x00000000004472a9 in process_thread (arg=0x7fffffff9e00) at builtin-top.c:1120
#13 0x00007ffff6e7dba8 in start_thread (arg=<optimized out>) at pthread_create.c:448
#14 0x00007ffff6f01b8c in __GI___clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:78
The cause is that perf_env__find_br_cntr_info tries to access a
null pointer pmu_caps in the perf_env struct. A similar issue exists
for homogeneous core systems which use the cpu_pmu_caps structure.
Fix this by populating cpu_pmu_caps and pmu_caps structures with
values from sysfs when calling perf top with branch stack sampling
enabled.
[1], LBR event logging introduced here:
https://lore.kernel.org/all/20231025201626.3000228-5-kan.liang@linux.intel.com/
Signed-off-by: Thomas Falcon <thomas.falcon@...el.com>
---
v2: update commit message with more meaningful stack trace from
gdb and indicate that affected systems are limited to CPU's
with LBR event logging support and that both hybrid and
non-hybrid core systems are affected.
---
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
Powered by blists - more mailing lists