diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index ce6a722..f89df52 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -1,9 +1,33 @@
+#include <linux/ioport.h>
 #include <linux/swap.h>
+
 #include <asm/cacheflush.h>
 #include <asm/page.h>
+#include <asm/page_types.h>
 #include <asm/sections.h>
 #include <asm/system.h>
 
+/*
+ * devmem_is_allowed() checks to see if /dev/mem access to a certain address
+ * is valid. The argument is a physical page number.
+ *
+ *
+ * On x86, access has to be given to the first megabyte of ram because that area
+ * contains bios code and data regions used by X and dosemu and similar apps.
+ * Access has to be given to non-kernel-ram areas as well, these contain the PCI
+ * mmio resources as well as potential bios/acpi data regions.
+ */
+int devmem_is_allowed(unsigned long pagenr)
+{
+	if (pagenr <= 256)
+		return 1;
+	if (iomem_is_exclusive(pagenr << PAGE_SHIFT))
+		return 0;
+	if (!page_is_ram(pagenr))
+		return 1;
+	return 0;
+}
+
 void free_init_pages(char *what, unsigned long begin, unsigned long end)
 {
 	unsigned long addr = begin;