linux-kernel - [PATCH 5/5] perf probe: Fix segfault when probe with lazy

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Date:	Mon, 13 Apr 2015 19:15:02 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	linux-kernel@...r.kernel.org, He Kuang <hekuang@...wei.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Wang Nan <wangnan0@...wei.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 5/5] perf probe: Fix segfault when probe with lazy_line to file

From: He Kuang <hekuang@...wei.com>

The first argument passed to find_probe_point_lazy() should be CU die,
which will be passed to die_walk_lines() when lazy_line matches.
Currently, when we probe with lazy_line pattern to file without function
name, NULL pointer is passed and causes a segment fault.

Can be reproduced as following:

  $ perf probe -k vmlinux --add='fs/super.c;s->s_count=1;'
  [ 1958.984658] perf[1020]: segfault at 10 ip 00007fc6e10d8c71 sp
  00007ffcbfaaf900 error 4 in libdw-0.161.so[7fc6e10ce000+34000]
  Segmentation fault

After this patch:

  $ perf probe -k vmlinux --add='fs/super.c;s->s_count=1;'
  Added new event:
  probe:_stext         (on @fs/super.c)

  You can now use it in all perf tools, such as:
    perf record -e probe:_stext -aR sleep 1

Signed-off-by: He Kuang <hekuang@...wei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Wang Nan <wangnan0@...wei.com>
Link: http://lkml.kernel.org/r/1428925290-5623-3-git-send-email-hekuang@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/probe-finder.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 431c12d299a2..e91101b8f60f 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -1067,7 +1067,7 @@ static int debuginfo__find_probes(struct debuginfo *dbg,
 			if (pp->function)
 				ret = find_probe_point_by_func(pf);
 			else if (pp->lazy_line)
-				ret = find_probe_point_lazy(NULL, pf);
+				ret = find_probe_point_lazy(&pf->cu_die, pf);
 			else {
 				pf->lno = pp->line;
 				ret = find_probe_point_by_line(pf);
-- 
1.9.3

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