Index: libc/include/sys/mman.h
===================================================================
--- libc/include/sys/mman.h	(revision 860294986ec6e7d55a73d99e924b1b0f7a23bbf6)
+++ libc/include/sys/mman.h	(revision d530237a45d9070488ae250c432a03f5b66278b7)
@@ -32,4 +32,6 @@
 #include <as.h>
 
+#define MAP_FAILED  ((void *) -1)
+
 #define MAP_SHARED       (1 << 0)
 #define MAP_PRIVATE      (1 << 1)