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Subject[tip:perf/core] perf top: Fix segfault pressing -> with no hist entries
Commit-ID:  bd315aab8a3ab1bc7074774b89a5d8ec7c1ff7ab
Gitweb: http://git.kernel.org/tip/bd315aab8a3ab1bc7074774b89a5d8ec7c1ff7ab
Author: Wang Nan <wangnan0@huawei.com>
AuthorDate: Mon, 14 Sep 2015 10:23:55 +0000
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Mon, 14 Sep 2015 15:10:41 -0300

perf top: Fix segfault pressing -> with no hist entries

'perf top' segfaults with following operation:

# perf top -e page-faults -p 11400 # 11400 never generates 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 resides 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 checking browser->selection before fetching
browser->selection->map.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1442226235-117265-1-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/ui/browsers/hists.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/tools/perf/ui/browsers/hists.c b/tools/perf/ui/browsers/hists.c
index cf86f2d..c04c60d 100644
--- a/tools/perf/ui/browsers/hists.c
+++ b/tools/perf/ui/browsers/hists.c
@@ -1968,7 +1968,8 @@ 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);

/* perf script support */
if (browser->he_selection) {
@@ -1976,6 +1977,15 @@ skip_annotation:
&actions[nr_options],
&options[nr_options],
thread, NULL);
+ /*
+ * Note that browser->selection != NULL
+ * when browser->he_selection is not NULL,
+ * so we don't need to check browser->selection
+ * before fetching browser->selection->sym like what
+ * we do before fetching browser->selection->map.
+ *
+ * See hist_browser__show_entry.
+ */
nr_options += add_script_opt(browser,
&actions[nr_options],
&options[nr_options],

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