[PATCH 4.20 011/171] perf script: Fix crash when processing recorded stat data

Greg Kroah-Hartman
2019-03-12T17:11:52Z

[ Upstream commit 8bf8c6da53c2265aea365a1de6038f118f522113 ]

While updating perf to work with Python3 and Python2 I noticed that the
stat-cpi script was dumping core.

$ perf stat -e cycles,instructions record -o /tmp/perf.data /bin/false

Performance counter stats for '/bin/false':

802,148 cycles

604,622 instructions 802,148 cycles
604,622 instructions

0.001445842 seconds time elapsed

$ perf script -i /tmp/perf.data -s scripts/python/stat-cpi.py
Segmentation fault (core dumped)
...
...
rblist=rblist@entry=0xb2a200 <rt_stat>,
new_entry=new_entry@entry=0x7ffcb755c310) at util/rblist.c:33
ctx=<optimized out>, type=<optimized out>, create=<optimized out>,
cpu=<optimized out>, evsel=<optimized out>) at util/stat-shadow.c:118
ctx=<optimized out>, type=<optimized out>, st=<optimized out>)
at util/stat-shadow.c:196
count=count@entry=727442, cpu=cpu@entry=0, st=0xb2a200 <rt_stat>)
at util/stat-shadow.c:239
config=config@entry=0xafeb40 <stat_config>,
counter=counter@entry=0x133c6e0) at util/stat.c:372
...
...

The issue is that since 1fcd03946b52 perf_stat__update_shadow_stats now calls
update_runtime_stat passing rt_stat rather than calling update_stats but
perf_stat__init_shadow_stats has never been called to initialize rt_stat in
the script path processing recorded stat data.

Since I can't see any reason why perf_stat__init_shadow_stats() is presently
initialized like it is in builtin-script.c::perf_sample__fprint_metric()
[4bd1bef8bba2f] I'm proposing it instead be initialized once in __cmd_script

Committer testing:

After applying the patch:

# perf script -i /tmp/perf.data -s tools/perf/scripts/python/stat-cpi.py
0.001970: cpu -1, thread -1 -> cpi 1.709079 (1075684/629394)
#

No segfault.

Signed-off-by: Tony Jones <tonyj@suse.de>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Fixes: 1fcd03946b52 ("perf stat: Update per-thread shadow stats")
Link: http://lkml.kernel.org/r/20190120191414.12925-1-tonyj@suse.de
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/perf/builtin-script.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
index 5c070a600233..d8791e0e5f75 100644
--- a/tools/perf/builtin-script.c
+++ b/tools/perf/builtin-script.c
@@ -1633,13 +1633,8 @@ static void perf_sample__fprint_metric(struct perf_script *script,
.force_header = false,
};
struct perf_evsel *ev2;
- static bool init;
u64 val;

- if (!init) {
- perf_stat__init_shadow_stats();
- init = true;
- }
if (!evsel->stats)
perf_evlist__alloc_stats(script->session->evlist, false);
if (evsel_script(evsel->leader)->gnum++ == 0)
@@ -2305,6 +2300,8 @@ static int __cmd_script(struct perf_script *script)

signal(SIGINT, sig_handler);

+ perf_stat__init_shadow_stats();
+
/* override event processing functions */
if (script->show_task_events) {
script->tool.comm = process_comm_event;
--
2.19.1