[PATCH] x86/x86_64: mark rodata section read-only: x86-64 support

x86-64 specific parts to make the .rodata section read only

Signed-off-by: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 23 insertions, 0 deletions

diff --git a/arch/x86_64/mm/init.c b/arch/x86_64/mm/init.c
index c016dfe84784..1faae5fc1c01 100644
--- a/arch/x86_64/mm/init.c
+++ b/arch/x86_64/mm/init.c
@@ -498,6 +498,29 @@ void free_initmem(void)
         printk ("Freeing unused kernel memory: %luk freed\n", (__init_end - __init_begin) >> 10);
 }
 
+#ifdef CONFIG_DEBUG_RODATA
+
+extern char __start_rodata, __end_rodata;
+void mark_rodata_ro(void)
+{
+        unsigned long addr = (unsigned long)&__start_rodata;
+
+        for (; addr < (unsigned long)&__end_rodata; addr += PAGE_SIZE)
+                change_page_attr_addr(addr, 1, PAGE_KERNEL_RO);
+
+        printk ("Write protecting the kernel read-only data: %luk\n",
+                        (&__end_rodata - &__start_rodata) >> 10);
+
+        /*
+         * change_page_attr_addr() requires a global_flush_tlb() call after it.
+         * We do this after the printk so that if something went wrong in the
+         * change, the printk gets out at least to give a better debug hint
+         * of who is the culprit.
+         */
+        global_flush_tlb();
+}
+#endif
+
 #ifdef CONFIG_BLK_DEV_INITRD
 void free_initrd_mem(unsigned long start, unsigned long end)
 {