On 2015/9/12 0:22, Namhyung Kim wrote:
On Fri, Sep 11, 2015 at 04:59:11AM +0000, Wang Nan wrote:
'perf top' segfaults with following operation:
# perf top -e page-faults -p 15173 # 15173 never generate page-fault
Then on the resulting empty interface, press right key:
# ./perf top -e page-faults -p 11400
perf: Segmentation fault
-------- backtrace --------
./perf[0x535428]
/lib64/libc.so.6(+0x3545f)[0x7f0dd360745f]
./perf[0x531d46]
./perf(perf_evlist__tui_browse_hists+0x96)[0x5340d6]
./perf[0x44ba2f]
/lib64/libpthread.so.0(+0x81d0)[0x7f0dd49dc1d0]
/lib64/libc.so.6(clone+0x6c)[0x7f0dd36b90dc]
The bug reside in perf_evsel__hists_browse() that, in the above circumstance
browser->selection can be NULL, but code after skip_annotation doesn't consider
it.
This patch fix it by checing browser->selection before fetching
browser->selection->map and browser->selection->sym.
I'm ok with this change, just a nitpick below..
Signed-off-by: Wang Nan <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Namhyung Kim <[email protected]>
---
tools/perf/ui/browsers/hists.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/tools/perf/ui/browsers/hists.c b/tools/perf/ui/browsers/hists.c
index e4fd40f..b00fa92 100644
--- a/tools/perf/ui/browsers/hists.c
+++ b/tools/perf/ui/browsers/hists.c
@@ -2017,7 +2017,8 @@ skip_annotation:
&options[nr_options], dso);
nr_options += add_map_opt(browser, &actions[nr_options],
&options[nr_options],
- browser->selection->map);
+ browser->selection ?
+ browser->selection->map : NULL);
nr_options += add_socket_opt(browser, &actions[nr_options],
&options[nr_options],
socket);
@@ -2030,7 +2031,10 @@ skip_annotation:
nr_options += add_script_opt(browser,
&actions[nr_options],
&options[nr_options],
- NULL,
browser->selection->sym);
+ NULL,
+ browser->selection ?
+ browser->selection->sym
:
+ NULL);
Is this really needed? IIUC browser->selection is not NULL if
browser->he_selection is not NULL. Did you see a case it's NULL?
Also passing a NULL thread and a NULL sym is meaningless here since
it's a duplication..
Actually I didn't see the case when browser->he_selection is not NULL but
browser->selection is NULL. I add the testing only for safety reason because
we have
if (browser->selection == NULL)
goto skip_annotation;
So I guess we'd better to check browser->selection in the codeblock
leading by
skip_annotation, so if someone breaks the assumption the code still work.
But yes, we can add the checker back when the assumption *does* be broken.
Currently let's add a comment here for code readers.
Please have a look for v2 patch.
Thank you.
Thanks,
Namhyung
}
nr_options += add_script_opt(browser, &actions[nr_options],
&options[nr_options], NULL, NULL);
--
1.8.3.4
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