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authorLuck, Tony <tony.luck@intel.com>2012-04-16 16:28:01 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-04-16 18:30:01 -0700
commitc76f39bddb84f93f70a5520d9253ec0317bec216 (patch)
treea131e6a03bc6eba668966e0795c44ce8fc8c26ca /arch/ia64
parentc06a9ebdb7a4f4823d4225fe789d8c20a1d534eb (diff)
ia64: fix futex_atomic_cmpxchg_inatomic()
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: <emeric.maschino@gmail.com> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=42757 Tested-by: <emeric.maschino@gmail.com> Acked-by: Michel Lespinasse <walken@google.com> Cc: stable@vger.kernel.org # v2.6.39+ Signed-off-by: Tony Luck <tony.luck@intel.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/ia64')
-rw-r--r--arch/ia64/include/asm/futex.h9
1 files changed, 5 insertions, 4 deletions
diff --git a/arch/ia64/include/asm/futex.h b/arch/ia64/include/asm/futex.h
index 0ab82cc2dc8f..d2bf1fd5e44f 100644
--- a/arch/ia64/include/asm/futex.h
+++ b/arch/ia64/include/asm/futex.h
@@ -106,15 +106,16 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
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");