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Message-ID: <49B16C69.6060203@redhat.com>
Date: Fri, 06 Mar 2009 13:33:13 -0500
From: Masami Hiramatsu <mhiramat@...hat.com>
To: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
CC: Ingo Molnar <mingo@...e.hu>,
Andrew Morton <akpm@...ux-foundation.org>,
Nick Piggin <npiggin@...e.de>,
Steven Rostedt <rostedt@...dmis.org>,
Andi Kleen <andi@...stfloor.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Peter Zijlstra <peterz@...radead.org>,
Frederic Weisbecker <fweisbec@...il.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Arjan van de Ven <arjan@...radead.org>,
Rusty Russell <rusty@...tcorp.com.au>,
"H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH -tip 4/4] Atomic text_poke() with fixmap take2
Mathieu Desnoyers wrote:
>> @@ -523,14 +526,17 @@ void *__kprobes text_poke(void *addr, co
>> 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]));
>
> Can the set_fixmap/clear_fixmap/local_flush_tlb be called within
> local_irq_save ? If yes, that would be better, especially for the SMP
> alternatives code, which would rely on interrupt disabling in text_poke
> for consistency (the mutex is not needed there).
Yes, that just changes pte.
---
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@...hat.com>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc: Ingo Molnar <mingo@...e.hu>
---
arch/x86/include/asm/fixmap.h | 2 ++
arch/x86/kernel/alternative.c | 24 +++++++++++++++---------
2 files changed, 17 insertions(+), 9 deletions(-)
Index: linux-2.6-tip/arch/x86/kernel/alternative.c
===================================================================
--- linux-2.6-tip.orig/arch/x86/kernel/alternative.c
+++ linux-2.6-tip/arch/x86/kernel/alternative.c
@@ -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
* 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, co
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();
+ local_irq_save(flags);
+ 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);
memcpy(&vaddr[(unsigned long)addr & ~PAGE_MASK], opcode, len);
- local_irq_enable();
- vunmap(vaddr);
+ clear_fixmap(FIX_TEXT_POKE0);
+ if (pages[1])
+ clear_fixmap(FIX_TEXT_POKE1);
+ local_flush_tlb();
+ local_irq_restore(flags);
sync_core();
/* Could also do a CLFLUSH here to speed up CPU recovery; but
that causes hangs on some VIA CPUs. */
Index: linux-2.6-tip/arch/x86/include/asm/fixmap.h
===================================================================
--- linux-2.6-tip.orig/arch/x86/include/asm/fixmap.h
+++ linux-2.6-tip/arch/x86/include/asm/fixmap.h
@@ -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,
--
Masami Hiramatsu
Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division
e-mail: mhiramat@...hat.com
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