x86: introduce /dev/mem restrictions with a config option

[linux-2.6-omap-h63xx.git] / arch / x86 / mm / init_32.c

diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index 1500dc8d63e4676586470d458722b71cad63ace1..39852d539018cf24c84f9835ec10244cee89499e 100644 (file)
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -1,5 +1,4 @@
 /*
- *  linux/arch/i386/mm/init.c
  *
  *  Copyright (C) 1995  Linus Torvalds
  *
@@ -228,6 +227,25 @@ static inline int page_kills_ppro(unsigned long pagenr)
        return 0;
 }
 
+/*
+ * 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 (!page_is_ram(pagenr))
+               return 1;
+       return 0;
+}
+
 #ifdef CONFIG_HIGHMEM
 pte_t *kmap_pte;
 pgprot_t kmap_prot;