From e587cadd8f47e202a30712e2906a65a0606d5865 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Thu, 6 Mar 2008 08:48:49 -0500 Subject: x86: enhance DEBUG_RODATA support - alternatives Fix a memcpy that should be a text_poke (in apply_alternatives). Use kernel_wp_save/kernel_wp_restore in text_poke to support DEBUG_RODATA correctly and so the CPU HOTPLUG special case can be removed. Add text_poke_early, for alternatives and paravirt boot-time and module load time patching. Changelog: - Fix text_set and text_poke alignment check (mixed up bitwise and and or) - Remove text_set - Export add_nops, so it can be used by others. - Document text_poke_early. - Remove clflush, since it breaks some VIA architectures and is not strictly necessary. - Add kerneldoc to text_poke and text_poke_early. - Create a second vmap instead of using the WP bit to support Xen and VMI. - Move local_irq disable within text_poke and text_poke_early to be able to be sleepable in these functions. Signed-off-by: Mathieu Desnoyers CC: Andi Kleen CC: pageexec@freemail.hu CC: H. Peter Anvin CC: Jeremy Fitzhardinge Signed-off-by: Ingo Molnar --- include/asm-x86/alternative.h | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/asm-x86/alternative.h b/include/asm-x86/alternative.h index d8bacf3c4b0..d26416b5722 100644 --- a/include/asm-x86/alternative.h +++ b/include/asm-x86/alternative.h @@ -156,6 +156,27 @@ apply_paravirt(struct paravirt_patch_site *start, #define __parainstructions_end NULL #endif -extern void text_poke(void *addr, unsigned char *opcode, int len); +extern void add_nops(void *insns, unsigned int len); + +/* + * Clear and restore the kernel write-protection flag on the local CPU. + * Allows the kernel to edit read-only pages. + * Side-effect: any interrupt handler running between save and restore will have + * the ability to write to read-only pages. + * + * Warning: + * Code patching in the UP case is safe if NMIs and MCE handlers are stopped and + * no thread can be preempted in the instructions being modified (no iret to an + * invalid instruction possible) or if the instructions are changed from a + * consistent state to another consistent state atomically. + * More care must be taken when modifying code in the SMP case because of + * Intel's errata. + * On the local CPU you need to be protected again NMI or MCE handlers seeing an + * inconsistent instruction while you patch. + * The _early version expects the memory to already be RW. + */ + +extern void *text_poke(void *addr, const void *opcode, size_t len); +extern void *text_poke_early(void *addr, const void *opcode, size_t len); #endif /* _ASM_X86_ALTERNATIVE_H */ -- cgit v1.2.3