[PATCH] x86/x86_64: mark rodata section read only: generic infrastructure

Generic prep-work for marking the .rodata section readonly:
* Align the rodata section at 4Kb boundary
* call the mark_rodata_ro() function when available

Signed-off-by: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/asm-generic/vmlinux.lds.h

@@ -10,6 +10,8 @@
 #define ALIGN_FUNCTION()  . = ALIGN(8)
 
 #define RODATA								\
+	. = ALIGN(4096);						\
+	__start_rodata = .;						\
 	.rodata           : AT(ADDR(.rodata) - LOAD_OFFSET) {		\
 		*(.rodata) *(.rodata.*)					\
 		*(__vermagic)		/* Kernel version magic */	\
@@ -74,6 +76,8 @@
         __ksymtab_strings : AT(ADDR(__ksymtab_strings) - LOAD_OFFSET) {	\
 		*(__ksymtab_strings)					\
 	}								\
+	__end_rodata = .;						\
+	. = ALIGN(4096);						\
 									\
 	/* Built-in module parameters. */				\
 	__param : AT(ADDR(__param) - LOAD_OFFSET) {			\

init/main.c

@@ -52,6 +52,7 @@
 #include <asm/bugs.h>
 #include <asm/setup.h>
 #include <asm/sections.h>
+#include <asm/cacheflush.h>
 
 /*
  * This is one of the first .c files built. Error out early
@@ -99,6 +100,9 @@ extern void acpi_early_init(void);
 #else
 static inline void acpi_early_init(void) { }
 #endif
+#ifndef CONFIG_DEBUG_RODATA
+static inline void mark_rodata_ro(void) { }
+#endif
 
 #ifdef CONFIG_TC
 extern void tc_init(void);
@@ -708,6 +712,7 @@ static int init(void * unused)
 	 */
 	free_initmem();
 	unlock_kernel();
+	mark_rodata_ro();
 	system_state = SYSTEM_RUNNING;
 	numa_default_policy();