[PATCH 3/3] perf probe: Fix segfault when probe with lazy_line to file

From: He Kuang
Date: Mon Apr 13 2015 - 07:46:58 EST

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 repoduced 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@xxxxxxxxxx>
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 431c12d..e91101b 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);

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