Index: arch/amd64/include/mm/page.h
===================================================================
--- arch/amd64/include/mm/page.h	(revision e8194664346da297d4362295839ff6b1fb615c0b)
+++ arch/amd64/include/mm/page.h	(revision 9dfc69a964b24b4f3fb953d10cf5dcfcf50f1014)
@@ -107,4 +107,21 @@
 #ifndef __ASM__
 
+/* Page fault error codes. */
+
+/** When bit on this position is 0, the page fault was caused by a not-present page. */
+#define PFERR_CODE_P            (1<<0)  
+
+/** When bit on this position is 1, the page fault was caused by a write. */
+#define PFERR_CODE_RW           (1<<1)
+
+/** When bit on this position is 1, the page fault was caused in user mode. */
+#define PFERR_CODE_US           (1<<2)
+
+/** When bit on this position is 1, a reserved bit was set in page directory. */
+#define PFERR_CODE_RSVD         (1<<3)
+
+/** When bit on this position os 1, the page fault was caused during instruction fecth. */
+#define PFERR_CODE_ID		(1<<4)
+
 /** Page Table Entry. */
 struct page_specifier {