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

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x86 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>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Arjan van de Ven 2006-01-06 00:12:02 -08:00 committed by Linus Torvalds
parent 37b73c8281
commit 63aaf3086b
3 changed files with 38 additions and 0 deletions
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10
arch/i386/Kconfig.debug
View file

@ -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

24
arch/i386/mm/init.c
View file

@ -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)
{

4
include/asm-i386/cacheflush.h
View file

@ -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 */