From c9d2f441f65d0c3a92938df02a752e6c78de487d Mon Sep 17 00:00:00 2001
From: Ben Pfaff <blp@cs.stanford.edu>
Date: Mon, 20 Sep 2004 22:25:28 +0000
Subject: [PATCH] Make pagedir_destroy(NULL) a no-op.

---
 src/userprog/pagedir.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/userprog/pagedir.c b/src/userprog/pagedir.c
index bfcda45..1edd0ff 100644
--- a/src/userprog/pagedir.c
+++ b/src/userprog/pagedir.c
@@ -19,6 +19,9 @@ pagedir_destroy (uint32_t *pd)
 {
   uint32_t *pde;
 
+  if (pd == NULL)
+    return;
+
   for (pde = pd; pde < pd + pd_no (PHYS_BASE); pde++)
     if (*pde & PG_P) 
       {
-- 
2.30.2