From c72bf82f96019216bb0a291d39c244977603661f Mon Sep 17 00:00:00 2001 From: Thomas Falcon Date: Thu, 12 Jun 2025 11:36:59 -0500 Subject: [PATCH] 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. $ 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 , 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 , 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=) 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 Signed-off-by: Thomas Falcon Link: https://lore.kernel.org/r/20250612163659.1357950-2-thomas.falcon@intel.com Signed-off-by: Namhyung Kim --- 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 051ded5ba9ba..c77e195ea786 100644 --- a/tools/perf/builtin-top.c +++ b/tools/perf/builtin-top.c @@ -1734,6 +1734,14 @@ 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 05a4f2657d72..ee51378fb0d9 100644 --- a/tools/perf/util/env.c +++ b/tools/perf/util/env.c @@ -433,6 +433,116 @@ 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 c90c1d717e73..d8df59072529 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); -- 2.25.1