This is a note to let you know that I've just added the patch titled
ia64: fix futex_atomic_cmpxchg_inatomic()
to the 3.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ia64-fix-futex_atomic_cmpxchg_inatomic.patch
and it can be found in the queue-3.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From c76f39bddb84f93f70a5520d9253ec0317bec216 Mon Sep 17 00:00:00 2001
From: "Luck, Tony" <[email protected]>
Date: Mon, 16 Apr 2012 16:28:01 -0700
Subject: ia64: fix futex_atomic_cmpxchg_inatomic()
From: "Luck, Tony" <[email protected]>
commit c76f39bddb84f93f70a5520d9253ec0317bec216 upstream.
Michel Lespinasse cleaned up the futex calling conventions in commit
37a9d912b24f ("futex: Sanitize cmpxchg_futex_value_locked API").
But the ia64 implementation was subtly broken. Gcc does not know that
register "r8" will be updated by the fault handler if the cmpxchg
instruction takes an exception. So it feels safe in letting the
initialization of r8 slide to after the cmpxchg. Result: we always
return 0 whether the user address faulted or not.
Fix by moving the initialization of r8 into the __asm__ code so gcc
won't move it.
Reported-by: <[email protected]>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=42757
Tested-by: <[email protected]>
Acked-by: Michel Lespinasse <[email protected]>
Signed-off-by: Tony Luck <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
arch/ia64/include/asm/futex.h | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
--- a/arch/ia64/include/asm/futex.h
+++ b/arch/ia64/include/asm/futex.h
@@ -107,15 +107,16 @@ futex_atomic_cmpxchg_inatomic(u32 *uval,
return -EFAULT;
{
- register unsigned long r8 __asm ("r8") = 0;
+ register unsigned long r8 __asm ("r8");
unsigned long prev;
__asm__ __volatile__(
" mf;; \n"
- " mov ar.ccv=%3;; \n"
- "[1:] cmpxchg4.acq %0=[%1],%2,ar.ccv \n"
+ " mov %0=r0 \n"
+ " mov ar.ccv=%4;; \n"
+ "[1:] cmpxchg4.acq %1=[%2],%3,ar.ccv \n"
" .xdata4 \"__ex_table\", 1b-., 2f-. \n"
"[2:]"
- : "=r" (prev)
+ : "=r" (r8), "=r" (prev)
: "r" (uaddr), "r" (newval),
"rO" ((long) (unsigned) oldval)
: "memory");
Patches currently in stable-queue which might be from [email protected] are
queue-3.2/ia64-fix-futex_atomic_cmpxchg_inatomic.patch
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