[PATCH v4 1/2] perf: move perf_pmus__find_core_pmu() prototype to pmus.h

[PATCH v4 1/2] perf: move perf_pmus__find_core_pmu() prototype to pmus.h

[Thomas Falcon]

perf_pmus__find_core_pmu() is implemented in util/pmus.c but its
prototpye is in util/pmu.h. Move it to util/pmus.h.

Suggested-by: Ian Rogers <irogers@google.com>
Signed-off-by: Thomas Falcon <thomas.falcon@intel.com>
---
 tools/perf/util/pmu.h  | 1 -
 tools/perf/util/pmus.h | 1 +
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
index a1fdd6d50c53..d38a63ba4583 100644
--- a/tools/perf/util/pmu.h
+++ b/tools/perf/util/pmu.h
@@ -298,7 +298,6 @@ struct perf_pmu *perf_pmu__lookup(struct list_head *pmus, int dirfd, const char
 				  bool eager_load);
 struct perf_pmu *perf_pmu__create_placeholder_core_pmu(struct list_head *core_pmus);
 void perf_pmu__delete(struct perf_pmu *pmu);
-struct perf_pmu *perf_pmus__find_core_pmu(void);
 
 const char *perf_pmu__name_from_config(struct perf_pmu *pmu, u64 config);
 bool perf_pmu__is_fake(const struct perf_pmu *pmu);
diff --git a/tools/perf/util/pmus.h b/tools/perf/util/pmus.h
index 8def20e615ad..d6a8d95af376 100644
--- a/tools/perf/util/pmus.h
+++ b/tools/perf/util/pmus.h
@@ -33,5 +33,6 @@ struct perf_pmu *perf_pmus__add_test_hwmon_pmu(int hwmon_dir,
 					       const char *sysfs_name,
 					       const char *name);
 struct perf_pmu *perf_pmus__fake_pmu(void);
+struct perf_pmu *perf_pmus__find_core_pmu(void);
 
 #endif /* __PMUS_H */
-- 
2.48.1

[PATCH v4 2/2] perf top: populate PMU capabilities data in perf_env

[Thomas Falcon]

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.

$ perf top  -e '{cpu_core/cpu-cycles/,cpu_core/event=0xc6,umask=0x3,frontend=0x11,name=frontend_retired_dsb_miss/}' -j any,counter
...
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/

Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Thomas Falcon <thomas.falcon@intel.com>
---
v4: prefer calloc and zfree operations in addition to other
    cleanups suggested by Namhyung and Arnaldo

v3: constify struct perf_pmu *pmu in __perf_env__read_core_pmu_caps()
    use perf_pmus__find_core_pmu() instead of perf_pmus__scan_core(NULL)

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    | 110 +++++++++++++++++++++++++++++++++++++++
 tools/perf/util/env.h    |   1 +
 3 files changed, 119 insertions(+)

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index f9f31391bddb..c9d679410591 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..b053d09438af 100644
--- a/tools/perf/util/env.c
+++ b/tools/perf/util/env.c
@@ -416,6 +416,116 @@ 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(const 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 = calloc(pmu->nr_caps, sizeof(char *));
+	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);
+		else if (!strcmp(pcaps->name, "branch_counter_nr"))
+			*br_cntr_nr = atoi(pcaps->value);
+		else if (!strcmp(pcaps->name, "branch_counter_width"))
+			*br_cntr_width = atoi(pcaps->value);
+	}
+	*nr_caps = pmu->nr_caps;
+	return 0;
+error:
+	while (tmp-- != *caps)
+		zfree(tmp);
+	zfree(caps);
+	*nr_caps = 0;
+	return ret;
+}
+
+int perf_env__read_core_pmu_caps(struct perf_env *env)
+{
+	struct pmu_caps *pmu_caps;
+	struct perf_pmu *pmu = NULL;
+	int nr_pmu, i = 0, j;
+	int ret;
+
+	nr_pmu = perf_pmus__num_core_pmus();
+
+	if (!nr_pmu)
+		return -ENODEV;
+
+	if (nr_pmu == 1) {
+		pmu = perf_pmus__find_core_pmu();
+		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 = calloc(nr_pmu, sizeof(*pmu_caps));
+	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++)
+			zfree(&pmu_caps[i].caps[j]);
+		zfree(&pmu_caps[i].caps);
+		zfree(&pmu_caps[i].pmu_name);
+	}
+	zfree(&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);
-- 
2.48.1

Re: [PATCH v4 2/2] perf top: populate PMU capabilities data in perf_env

[Falcon, Thomas]

Hi, is there anything still needed from me before this can be accepted?

Thanks,
Tom


On Thu, 2025-06-12 at 11:36 -0500, Thomas Falcon wrote:
> 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.
> 
> $ perf top  -e '{cpu_core/cpu-cycles/,cpu_core/event=0xc6,umask=0x3,frontend=0x11,name=frontend_retired_dsb_miss/}' -j any,counter
> ...
> 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/
> 
> Reviewed-by: Ian Rogers <irogers@google.com>
> Signed-off-by: Thomas Falcon <thomas.falcon@intel.com>
> ---
> v4: prefer calloc and zfree operations in addition to other
>     cleanups suggested by Namhyung and Arnaldo
> 
> v3: constify struct perf_pmu *pmu in __perf_env__read_core_pmu_caps()
>     use perf_pmus__find_core_pmu() instead of perf_pmus__scan_core(NULL)
> 
> 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    | 110 +++++++++++++++++++++++++++++++++++++++
>  tools/perf/util/env.h    |   1 +
>  3 files changed, 119 insertions(+)
> 
> diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
> index f9f31391bddb..c9d679410591 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..b053d09438af 100644
> --- a/tools/perf/util/env.c
> +++ b/tools/perf/util/env.c
> @@ -416,6 +416,116 @@ 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(const 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 = calloc(pmu->nr_caps, sizeof(char *));
> +	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);
> +		else if (!strcmp(pcaps->name, "branch_counter_nr"))
> +			*br_cntr_nr = atoi(pcaps->value);
> +		else if (!strcmp(pcaps->name, "branch_counter_width"))
> +			*br_cntr_width = atoi(pcaps->value);
> +	}
> +	*nr_caps = pmu->nr_caps;
> +	return 0;
> +error:
> +	while (tmp-- != *caps)
> +		zfree(tmp);
> +	zfree(caps);
> +	*nr_caps = 0;
> +	return ret;
> +}
> +
> +int perf_env__read_core_pmu_caps(struct perf_env *env)
> +{
> +	struct pmu_caps *pmu_caps;
> +	struct perf_pmu *pmu = NULL;
> +	int nr_pmu, i = 0, j;
> +	int ret;
> +
> +	nr_pmu = perf_pmus__num_core_pmus();
> +
> +	if (!nr_pmu)
> +		return -ENODEV;
> +
> +	if (nr_pmu == 1) {
> +		pmu = perf_pmus__find_core_pmu();
> +		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 = calloc(nr_pmu, sizeof(*pmu_caps));
> +	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++)
> +			zfree(&pmu_caps[i].caps[j]);
> +		zfree(&pmu_caps[i].caps);
> +		zfree(&pmu_caps[i].pmu_name);
> +	}
> +	zfree(&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);

Re: [PATCH v4 2/2] perf top: populate PMU capabilities data in perf_env

[Namhyung Kim]

Hello,

On Thu, Jun 26, 2025 at 04:47:18PM +0000, Falcon, Thomas wrote:
> Hi, is there anything still needed from me before this can be accepted?
 
Sorry I just missed it.  I'll add it to the tmp branch for testing.

Thanks,
Namhyung

> 
> On Thu, 2025-06-12 at 11:36 -0500, Thomas Falcon wrote:
> > 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.
> > 
> > $ perf top  -e '{cpu_core/cpu-cycles/,cpu_core/event=0xc6,umask=0x3,frontend=0x11,name=frontend_retired_dsb_miss/}' -j any,counter
> > ...
> > 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/
> > 
> > Reviewed-by: Ian Rogers <irogers@google.com>
> > Signed-off-by: Thomas Falcon <thomas.falcon@intel.com>
> > ---
> > v4: prefer calloc and zfree operations in addition to other
> >     cleanups suggested by Namhyung and Arnaldo
> > 
> > v3: constify struct perf_pmu *pmu in __perf_env__read_core_pmu_caps()
> >     use perf_pmus__find_core_pmu() instead of perf_pmus__scan_core(NULL)
> > 
> > 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.

Re: [PATCH v4 1/2] perf: move perf_pmus__find_core_pmu() prototype to pmus.h

[Namhyung Kim]

On Thu, 12 Jun 2025 11:36:58 -0500, Thomas Falcon wrote:
> perf_pmus__find_core_pmu() is implemented in util/pmus.c but its
> prototpye is in util/pmu.h. Move it to util/pmus.h.
> 
> 
Applied to perf-tools-next, thanks!

Best regards,
Namhyung