From e47749f1796d1df39a7eaae95f2784aaa43df57d Mon Sep 17 00:00:00 2001 From: Thomas Richter Date: Wed, 13 Sep 2023 14:51:57 +0200 Subject: perf jevent: fix core dump on software events on s390 Running commands such as # ./perf stat -e cs -- true Segmentation fault (core dumped) # ./perf stat -e cpu-clock-- true Segmentation fault (core dumped) # dump core. This should not happen as these events are defined even when no hardware PMU is available. Debugging this reveals this call chain: perf_pmus__find_by_type(type=1) +--> pmu_read_sysfs(core_only=false) +--> perf_pmu__find2(dirfd=3, name=0x152a113 "software") +--> perf_pmu__lookup(pmus=0x14f0568 , dirfd=3, lookup_name=0x152a113 "software") +--> perf_pmu__find_events_table (pmu=0x1532130) Now the pmu is "software" and it tries to find a proper table generated by the pmu-event generation process for s390: # cd pmu-events/ # ./jevents.py s390 all /root/linux/tools/perf/pmu-events/arch |\ grep -E '^const struct pmu_table_entry' const struct pmu_table_entry pmu_events__cf_z10[] = { const struct pmu_table_entry pmu_events__cf_z13[] = { const struct pmu_table_entry pmu_metrics__cf_z13[] = { const struct pmu_table_entry pmu_events__cf_z14[] = { const struct pmu_table_entry pmu_metrics__cf_z14[] = { const struct pmu_table_entry pmu_events__cf_z15[] = { const struct pmu_table_entry pmu_metrics__cf_z15[] = { const struct pmu_table_entry pmu_events__cf_z16[] = { const struct pmu_table_entry pmu_metrics__cf_z16[] = { const struct pmu_table_entry pmu_events__cf_z196[] = { const struct pmu_table_entry pmu_events__cf_zec12[] = { const struct pmu_table_entry pmu_metrics__cf_zec12[] = { const struct pmu_table_entry pmu_events__test_soc_cpu[] = { const struct pmu_table_entry pmu_metrics__test_soc_cpu[] = { const struct pmu_table_entry pmu_events__test_soc_sys[] = { # However event "software" is not listed, as can be seen in the generated const struct pmu_events_map pmu_events_map[]. So in function perf_pmu__find_events_table(), the variable table is initialized to NULL, but never set to a proper value. The function scans all generated &pmu_events_map[] tables, but no table matches, because the tables are s390 CPU Measurement unit specific: i = 0; for (;;) { const struct pmu_events_map *map = &pmu_events_map[i++]; if (!map->arch) break; --> the maps are there because the build generated them if (!strcmp_cpuid_str(map->cpuid, cpuid)) { table = &map->event_table; break; } --> Since no matching CPU string the table var remains 0x0 } free(cpuid); if (!pmu) return table; --> The pmu is "software" so it exists and no return --> and here perf dies because table is 0x0 for (i = 0; i < table->num_pmus; i++) { ... } return NULL; Fix this and do not access the table variable. Instead return 0x0 which is the same return code when the for-loop was not successful. Output after: # ./perf stat -e cs -- true Performance counter stats for 'true': 0 cs 0.000853105 seconds time elapsed 0.000061000 seconds user 0.000827000 seconds sys # ./perf stat -e cpu-clock -- true Performance counter stats for 'true': 0.25 msec cpu-clock # 0.341 CPUs utilized 0.000728383 seconds time elapsed 0.000055000 seconds user 0.000706000 seconds sys # ./perf stat -e cycles -- true Performance counter stats for 'true': cycles 0.000767298 seconds time elapsed 0.000055000 seconds user 0.000739000 seconds sys # Fixes: 7c52f10c0d4d8 ("perf pmu: Cache JSON events table") Signed-off-by: Thomas Richter Reviewed-by: Ian Rogers Cc: dengler@linux.ibm.com Cc: gor@linux.ibm.com Cc: hca@linux.ibm.com Cc: sumanthk@linux.ibm.com Cc: svens@linux.ibm.com Link: https://lore.kernel.org/r/20230913125157.2790375-1-tmricht@linux.ibm.com Signed-off-by: Namhyung Kim --- tools/perf/pmu-events/jevents.py | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'tools') diff --git a/tools/perf/pmu-events/jevents.py b/tools/perf/pmu-events/jevents.py index a7e88332276d..72ba4a9239c6 100755 --- a/tools/perf/pmu-events/jevents.py +++ b/tools/perf/pmu-events/jevents.py @@ -991,7 +991,7 @@ const struct pmu_events_table *perf_pmu__find_events_table(struct perf_pmu *pmu) } } free(cpuid); - if (!pmu) + if (!pmu || !table) return table; for (i = 0; i < table->num_pmus; i++) { -- cgit v1.2.3