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author | Thomas Richter <tmricht@linux.ibm.com> | 2023-09-13 14:51:57 +0200 |
---|---|---|
committer | Namhyung Kim <namhyung@kernel.org> | 2023-09-17 15:51:57 -0700 |
commit | e47749f1796d1df39a7eaae95f2784aaa43df57d (patch) | |
tree | 4e423b7f25d8096f2cee23102ffb2ad8794dc860 /tools | |
parent | eaaebb01a7a6d7d422f80e0dacf9a07fb90f22dc (diff) | |
download | lwn-e47749f1796d1df39a7eaae95f2784aaa43df57d.tar.gz lwn-e47749f1796d1df39a7eaae95f2784aaa43df57d.zip |
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 <other_pmus>, 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':
<not supported> 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 <tmricht@linux.ibm.com>
Reviewed-by: Ian Rogers <irogers@google.com>
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 <namhyung@kernel.org>
Diffstat (limited to 'tools')
-rwxr-xr-x | tools/perf/pmu-events/jevents.py | 2 |
1 files changed, 1 insertions, 1 deletions
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++) { |