diff --git a/include/asm-x86/page_64.h b/include/asm-x86/page_64.h
index 54d5db6..6ea7285 100644
--- a/include/asm-x86/page_64.h
+++ b/include/asm-x86/page_64.h
@@ -80,6 +80,9 @@
 
 #define vmemmap ((struct page *)VMEMMAP_START)
 
+extern unsigned long init_memory_mapping(unsigned long start,
+					 unsigned long end);
+
 #endif	/* !__ASSEMBLY__ */
 
 #ifdef CONFIG_FLATMEM