===== page_alloc.c 1.66 vs edited =====
--- 1.66/xen/common/page_alloc.c	Tue May 10 16:28:45 2005
+++ edited/page_alloc.c	Wed May 18 15:47:46 2005
@@ -156,6 +156,8 @@
 
     ps = round_pgup(ps);
     pe = round_pgdown(pe);
+    if (pe <= ps) /* no full pages in range */
+	return;
 
     map_free(ps >> PAGE_SHIFT, (pe - ps) >> PAGE_SHIFT);