Index: arch/amd64/include/mm/as.h
===================================================================
--- arch/amd64/include/mm/as.h	(revision 8a1da55db67387e40c7dd92111ead25c83ea8d9f)
+++ arch/amd64/include/mm/as.h	(revision 40ca40239dd13e9208afb2d4d3539ec93d198a9c)
@@ -35,5 +35,5 @@
 #define KERNEL_ADDRESS_SPACE_END_ARCH		(__address) 0xffffffffffffffff
 #define USER_ADDRESS_SPACE_START_ARCH		(__address) 0x0000000000000000
-#define USER_ADDRESS_SPACE_END_ARCH		(__address) 0x00008fffffffffff
+#define USER_ADDRESS_SPACE_END_ARCH		(__address) 0x00007fffffffffff
 
 #define UTEXT_ADDRESS_ARCH	0x00001000
Index: arch/amd64/src/userspace.c
===================================================================
--- arch/amd64/src/userspace.c	(revision 8a1da55db67387e40c7dd92111ead25c83ea8d9f)
+++ arch/amd64/src/userspace.c	(revision 40ca40239dd13e9208afb2d4d3539ec93d198a9c)
@@ -58,5 +58,9 @@
 			  "pushq %%rsi;"
 			  "iretq;"
-			  : : "i" (gdtselector(UDATA_DES) | PL_USER), "i" (USTACK_ADDRESS+THREAD_STACK_SIZE), "r" (ipl), "i" (gdtselector(UTEXT_DES) | PL_USER), "i" (UTEXT_ADDRESS));
+			  : : "i" (gdtselector(UDATA_DES) | PL_USER), 
+			  "i" (USTACK_ADDRESS+THREAD_STACK_SIZE), 
+			  "r" (ipl), 
+			  "i" (gdtselector(UTEXT_DES) | PL_USER), 
+			  "i" (UTEXT_ADDRESS));
 	
 	/* Unreachable */