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

[Thomas Falcon <thomas.falcon@intel.com>]

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@intel.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