linux-kernel - Re: [PATCH v2] perf tools: Fix segfault in 'perf top'

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Message-ID: <20150914181256.GD5250@kernel.org>
Date:	Mon, 14 Sep 2015 15:12:56 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Wang Nan <wangnan0@...wei.com>
Cc:	namhyung@...nel.org, linux-kernel@...r.kernel.org,
	lizefan@...wei.com, pi3orama@....com
Subject: Re: [PATCH v2] perf tools: Fix segfault in 'perf top'

Em Mon, Sep 14, 2015 at 03:07:14PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Mon, Sep 14, 2015 at 10:23:55AM +0000, Wang Nan escreveu:
> > '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:
> 
> So, this happens in perf/urgent, so we need to apply it there first,
> which this patch doesn't.
> 
> I am fixing it up this time, thanks for the patch!

For reference, below is the resulting patch, pushed to acme/perf/urgent,
now checking if there are more patches to go together with this one...

- Arnaldo

diff --git a/tools/perf/ui/browsers/hists.c b/tools/perf/ui/browsers/hists.c
index cf86f2d3a5e7..c04c60d4863c 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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