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Commit 78ff7fae authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Ingo Molnar
Browse files

x86: implement atomic text_poke() via fixmap 



Use fixmaps instead of vmap/vunmap in text_poke() for avoiding
page allocation and delayed unmapping.

At the result of above change, text_poke() becomes atomic and can be called
from stop_machine() etc.

Signed-off-by: default avatarMasami Hiramatsu <mhiramat@redhat.com>
Acked-by: default avatarMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
LKML-Reference: <49B14352.2040705@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 3945dab4

arch/x86/include/asm/fixmap.h

+2 −0
Original line number Original line Diff line number Diff line
@@ -111,6 +111,8 @@ enum fixed_addresses { 
#ifdef CONFIG_PARAVIRT

#ifdef CONFIG_PARAVIRT

	FIX_PARAVIRT_BOOTMAP,

	FIX_PARAVIRT_BOOTMAP,

#endif

#endif

	FIX_TEXT_POKE0,	/* reserve 2 pages for text_poke() */

	FIX_TEXT_POKE1,

	__end_of_permanent_fixed_addresses,

	__end_of_permanent_fixed_addresses,

#ifdef CONFIG_PROVIDE_OHCI1394_DMA_INIT

#ifdef CONFIG_PROVIDE_OHCI1394_DMA_INIT

	FIX_OHCI1394_BASE,

	FIX_OHCI1394_BASE,

arch/x86/kernel/alternative.c

+15 −9
Original line number Original line Diff line number Diff line
@@ -13,7 +13,9 @@ 
#include <asm/nmi.h>

#include <asm/nmi.h>

#include <asm/vsyscall.h>

#include <asm/vsyscall.h>

#include <asm/cacheflush.h>

#include <asm/cacheflush.h>

#include <asm/tlbflush.h>

#include <asm/io.h>

#include <asm/io.h>

#include <asm/fixmap.h>





#define MAX_PATCH_LEN (255-1)

#define MAX_PATCH_LEN (255-1)
@@ -505,15 +507,16 @@ void *text_poke_early(void *addr, const void *opcode, size_t len) 
 * It means the size must be writable atomically and the address must be aligned

 * It means the size must be writable atomically and the address must be aligned

 * in a way that permits an atomic write. It also makes sure we fit on a single

 * in a way that permits an atomic write. It also makes sure we fit on a single

 * page.

 * page.

 *

 * Note: Must be called under text_mutex.

 */

 */

void *__kprobes text_poke(void *addr, const void *opcode, size_t len)

void *__kprobes text_poke(void *addr, const void *opcode, size_t len)

{

{

	unsigned long flags;

	char *vaddr;

	char *vaddr;

	int nr_pages = 2;

	struct page *pages[2];

	struct page *pages[2];

	int i;

	int i;





	might_sleep();

	if (!core_kernel_text((unsigned long)addr)) {

	if (!core_kernel_text((unsigned long)addr)) {

		pages[0] = vmalloc_to_page(addr);

		pages[0] = vmalloc_to_page(addr);

		pages[1] = vmalloc_to_page(addr + PAGE_SIZE);

		pages[1] = vmalloc_to_page(addr + PAGE_SIZE);
@@ -523,14 +526,17 @@ void *__kprobes text_poke(void *addr, const void *opcode, size_t len) 
		pages[1] = virt_to_page(addr + PAGE_SIZE);

		pages[1] = virt_to_page(addr + PAGE_SIZE);

	}

	}

	BUG_ON(!pages[0]);

	BUG_ON(!pages[0]);

	if (!pages[1])

	set_fixmap(FIX_TEXT_POKE0, page_to_phys(pages[0]));

		nr_pages = 1;

	if (pages[1])

	vaddr = vmap(pages, nr_pages, VM_MAP, PAGE_KERNEL);

		set_fixmap(FIX_TEXT_POKE1, page_to_phys(pages[1]));

	BUG_ON(!vaddr);

	vaddr = (char *)fix_to_virt(FIX_TEXT_POKE0);

	local_irq_disable();

	local_irq_save(flags);

	memcpy(&vaddr[(unsigned long)addr & ~PAGE_MASK], opcode, len);

	memcpy(&vaddr[(unsigned long)addr & ~PAGE_MASK], opcode, len);

	local_irq_enable();

	local_irq_restore(flags);

	vunmap(vaddr);

	clear_fixmap(FIX_TEXT_POKE0);

	if (pages[1])

		clear_fixmap(FIX_TEXT_POKE1);

	local_flush_tlb();

	sync_core();

	sync_core();

	/* Could also do a CLFLUSH here to speed up CPU recovery; but

	/* Could also do a CLFLUSH here to speed up CPU recovery; but

	   that causes hangs on some VIA CPUs. */

	   that causes hangs on some VIA CPUs. */