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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: Masami Hiramatsu <mhiramat@redhat.com>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
LKML-Reference: <49B14352.2040705@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Masami Hiramatsu 2009-03-06 10:37:54 -05:00 committed by Ingo Molnar
parent 3945dab45a
commit 78ff7fae04
2 changed files with 17 additions and 9 deletions
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2
arch/x86/include/asm/fixmap.h
View File

@ -111,6 +111,8 @@ enum fixed_addresses {
#ifdef CONFIG_PARAVIRT
FIX_PARAVIRT_BOOTMAP,
#endif
FIX_TEXT_POKE0, /* reserve 2 pages for text_poke() */
FIX_TEXT_POKE1,
__end_of_permanent_fixed_addresses,
#ifdef CONFIG_PROVIDE_OHCI1394_DMA_INIT
FIX_OHCI1394_BASE,

24
arch/x86/kernel/alternative.c
View File

@ -13,7 +13,9 @@
#include <asm/nmi.h>
#include <asm/vsyscall.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>
#include <asm/io.h>
#include <asm/fixmap.h>
#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
* in a way that permits an atomic write. It also makes sure we fit on a single
* page.
*
* Note: Must be called under text_mutex.
*/
void *__kprobes text_poke(void *addr, const void *opcode, size_t len)
{
unsigned long flags;
char *vaddr;
int nr_pages = 2;
struct page *pages[2];
int i;
might_sleep();
if (!core_kernel_text((unsigned long)addr)) {
pages[0] = vmalloc_to_page(addr);
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);
}
BUG_ON(!pages[0]);
if (!pages[1])
nr_pages = 1;
vaddr = vmap(pages, nr_pages, VM_MAP, PAGE_KERNEL);
BUG_ON(!vaddr);
local_irq_disable();
set_fixmap(FIX_TEXT_POKE0, page_to_phys(pages[0]));
if (pages[1])
set_fixmap(FIX_TEXT_POKE1, page_to_phys(pages[1]));
vaddr = (char *)fix_to_virt(FIX_TEXT_POKE0);
local_irq_save(flags);
memcpy(&vaddr[(unsigned long)addr & ~PAGE_MASK], opcode, len);
local_irq_enable();
vunmap(vaddr);
local_irq_restore(flags);
clear_fixmap(FIX_TEXT_POKE0);
if (pages[1])
clear_fixmap(FIX_TEXT_POKE1);
local_flush_tlb();
sync_core();
/* Could also do a CLFLUSH here to speed up CPU recovery; but
that causes hangs on some VIA CPUs. */