[tip:perf/urgent] perf hists browser: Fix segfault when showing callchain

From: tip-bot for Namhyung Kim
Date: Fri Jan 09 2015 - 07:32:15 EST


Commit-ID: c09e31cc128cf1aec3a6cd47203508fbf0082873
Gitweb: http://git.kernel.org/tip/c09e31cc128cf1aec3a6cd47203508fbf0082873
Author: Namhyung Kim <namhyung@xxxxxxxxxx>
AuthorDate: Wed, 24 Dec 2014 15:04:36 +0900
Committer: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Thu, 8 Jan 2015 11:59:16 -0300

perf hists browser: Fix segfault when showing callchain

When perf report on TUI shows callchain it checks first node has
siblings to determine whether it needs to print percentage value.

But it missed a case that first node is NULL. So sometimes it segfaults
like below:

$ perf top -g
perf: Segmentation fault
-------- backtrace --------
perf[0x4fcefb]
/usr/lib/libc.so.6(+0x33b20)[0x7f2a35839b20]
perf(rb_next+0x8)[0x47d3d8]
perf[0x4f6058]
perf[0x4f833b]
perf[0x4f8610]
perf[0x4f209e]
perf(ui_browser__run+0x3a)[0x4f2e6a]
perf[0x4f94ee]
perf(perf_evlist__tui_browse_hists+0x94)[0x4fbbf4]
perf[0x444d10]
/usr/lib/libpthread.so.0(+0x7314)[0x7f2a37070314]
/usr/lib/libc.so.6(clone+0x6d)[0x7f2a358ee5bd]

$ addr2line -e `which perf` 0x4f6058
/home/namhyung/project/linux/tools/perf/ui/browsers/hists.c:553

I don't know why the backtrace didn't print some symbols..

Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
Fixes: 4087d11cd945 ("perf hists browser: Print overhead percent value for first-level callchain")
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/1419401076-21700-1-git-send-email-namhyung@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
tools/perf/ui/browsers/hists.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/ui/browsers/hists.c b/tools/perf/ui/browsers/hists.c
index e6bb04b..788506e 100644
--- a/tools/perf/ui/browsers/hists.c
+++ b/tools/perf/ui/browsers/hists.c
@@ -550,7 +550,7 @@ static int hist_browser__show_callchain(struct hist_browser *browser,
bool need_percent;

node = rb_first(root);
- need_percent = !!rb_next(node);
+ need_percent = node && rb_next(node);

while (node) {
struct callchain_node *child = rb_entry(node, struct callchain_node, rb_node);
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/