[PATCH] perf callchain: Fix segfault in thread__resolve_callchain_sample()

[Adrian Hunter]

Do not dereference 'chain' when it is NULL.

  $ perf record -e intel_pt//u -e branch-misses:u uname
  $ perf report --itrace=l --branch-history
  perf: Segmentation fault

Fixes: e9024d519d89 ("perf callchain: Honour the ordering of PERF_CONTEXT_{USER,KERNEL,etc}")
Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
---
 tools/perf/util/machine.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 6a0f5c25ce3e..0a21ab69a247 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -2414,7 +2414,7 @@ static int thread__resolve_callchain_sample(struct thread *thread,
 	}
 
 check_calls:
-	if (callchain_param.order != ORDER_CALLEE) {
+	if (chain && callchain_param.order != ORDER_CALLEE) {
 		err = find_prev_cpumode(chain, thread, cursor, parent, root_al,
 					&cpumode, chain->nr - first_call);
 		if (err)
-- 
2.17.1