--- zzzz-none-000/linux-3.10.107/tools/perf/util/pstack.c	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/tools/perf/util/pstack.c	2021-02-04 17:41:59.000000000 +0000
@@ -6,6 +6,7 @@
 
 #include "util.h"
 #include "pstack.h"
+#include "debug.h"
 #include <linux/kernel.h>
 #include <stdlib.h>
 
@@ -73,3 +74,10 @@
 	pstack->entries[pstack->top] = NULL;
 	return ret;
 }
+
+void *pstack__peek(struct pstack *pstack)
+{
+	if (pstack->top == 0)
+		return NULL;
+	return pstack->entries[pstack->top - 1];
+}