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Commit 63aaf308 authored by Arjan van de Ven's avatar Arjan van de Ven Committed by Linus Torvalds
Browse files

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



x86 specific parts to make the .rodata section read only

Signed-off-by: default avatarArjan van de Ven <arjan@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAdrian Bunk <bunk@stusta.de>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 37b73c82

arch/i386/Kconfig.debug

+10 −0
Original line number Diff line number Diff line
@@ -42,6 +42,16 @@ config DEBUG_PAGEALLOC 
	  This results in a large slowdown, but helps to find certain types

	  of memory corruptions.



config DEBUG_RODATA

	bool "Write protect kernel read-only data structures"

	depends on DEBUG_KERNEL

	help

	  Mark the kernel read-only data as write-protected in the pagetables,

	  in order to catch accidental (and incorrect) writes to such const

	  data. This option may have a slight performance impact because a

	  portion of the kernel code won't be covered by a 2MB TLB anymore.

	  If in doubt, say "N".



config 4KSTACKS

	bool "Use 4Kb for kernel stacks instead of 8Kb"

	depends on DEBUG_KERNEL

arch/i386/mm/init.c

+24 −0
Original line number Diff line number Diff line
@@ -735,6 +735,30 @@ void free_initmem(void) 
	printk (KERN_INFO "Freeing unused kernel memory: %dk 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(virt_to_page(addr), 1, PAGE_KERNEL_RO);



	printk ("Write protecting the kernel read-only data: %luk\n",

			(unsigned long)(&__end_rodata - &__start_rodata) >> 10);



	/*

	 * change_page_attr() 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)

{

include/asm-i386/cacheflush.h

+4 −0
Original line number Diff line number Diff line
@@ -31,4 +31,8 @@ int change_page_attr(struct page *page, int numpages, pgprot_t prot); 
void kernel_map_pages(struct page *page, int numpages, int enable);

#endif



#ifdef CONFIG_DEBUG_RODATA

void mark_rodata_ro(void);

#endif



#endif /* _I386_CACHEFLUSH_H */