42 lines
1.5 KiB
Diff
42 lines
1.5 KiB
Diff
From: Tony Luck <tony.luck@intel.com>
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Date: Fri Apr 13 11:32:44 2012 -0700
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Subject: [IA64] Fix futex_atomic_cmpxchg_inatomic()
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commit 9d38e66bf07b6e57c8e60767c454e1db9aac4484 upstream.
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Michel Lespinasse cleaned up the futex calling conventions in
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commit 37a9d912b24f96a0591773e6e6c3642991ae5a70
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futex: Sanitize cmpxchg_futex_value_locked API
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But the ia64 implementation was subtly broken. Gcc does not know
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that register "r8" will be updated by the fault handler if the
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cmpxchg instruction takes an exception. So it feels safe in letting
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the initialization of r8 slide to after the cmpxchg. Result: we
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always return 0 whether the user address faulted or not.
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Fix by moving the initialization of r8 into the __asm__ code so
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gcc won't move it.
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Reported-by: <emeric.maschino@gmail.com>
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Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=42757
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Cc: stable@vger.kernel.org # v2.6.39+
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Signed-off-by: Tony Luck <tony.luck@intel.com>
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---
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diff --git a/arch/ia64/include/asm/futex.h b/arch/ia64/include/asm/futex.h
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index 8428525..71949a5 100644
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--- a/arch/ia64/include/asm/futex.h
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+++ b/arch/ia64/include/asm/futex.h
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@@ -107,10 +107,11 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
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return -EFAULT;
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{
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- register unsigned long r8 __asm ("r8") = 0;
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+ register unsigned long r8 __asm ("r8");
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unsigned long prev;
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__asm__ __volatile__(
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" mf;; \n"
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+ " mov r8=r0 \n"
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" mov ar.ccv=%3;; \n"
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"[1:] cmpxchg4.acq %0=[%1],%2,ar.ccv \n"
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" .xdata4 \"__ex_table\", 1b-., 2f-. \n"
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