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From: Chuck Ebbert <cebbert@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Andi Kleen <andi@firstfloor.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Stable Team <stable@kernel.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@elte.hu>, Gerd Hoffmann <kraxel@redhat.com>
Subject: Re: The SMP alternatives code breaks exception fixup?
Date: Tue, 22 Jan 2008 15:19:33 -0500	[thread overview]
Message-ID: <47964FD5.6020801@redhat.com> (raw)
In-Reply-To: <alpine.LFD.1.00.0801221312200.3199@apollo.tec.linutronix.de>

On 01/22/2008 07:35 AM, Thomas Gleixner wrote:
> 
> That's a long standing bug in both the PI futex and the standard futex
> code. Needs to go to stable as well.
> 

Here's the 2.6.23 version:


Subject: x86: fix missing exception entry for SMP alternatives in futex macros
From: Thomas Gleixner <tglx@linutronix.de>

The exception fixup for the futex macros __futex_atomic_op2 and
futex_atomic_cmpxchg_inatomic() is missing an entry when the lock
prefix is replaced by a NOP via SMP alternatives.

Chuck Ebert tracked this down from the information provided in:
https://bugzilla.redhat.com/show_bug.cgi?id=429412

The solution is to add another fixup after the LOCK_PREFIX, so both
the LOCK and NOP case have their own entry in the exception table.

The solution was pointed out by Andi Kleen.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@elte.hu>

---
 include/asm-i386/futex.h |    8 ++++----
 include/asm-x86_64/futex.h |    8 ++++----
 2 files changed, 8 insertions(+), 8 deletions(-)

Index: linux-2.6/include/asm-i386/futex.h
===================================================================
--- linux-2.6.orig/include/asm-i386/futex.h	2008-01-22 13:13:10.000000000 +0100
+++ linux-2.6/include/asm-i386/futex.h	2008-01-22 13:13:49.000000000 +0100
@@ -28,7 +28,7 @@
 "1:	movl	%2, %0\n\
 	movl	%0, %3\n"					\
 	insn "\n"						\
-"2:	" LOCK_PREFIX "cmpxchgl %3, %2\n\
+"2:	" LOCK_PREFIX "\n 5: cmpxchgl %3, %2\n\
 	jnz	1b\n\
 3:	.section .fixup,\"ax\"\n\
 4:	mov	%5, %1\n\
@@ -36,7 +36,7 @@
 	.previous\n\
 	.section __ex_table,\"a\"\n\
 	.align	8\n\
-	.long	1b,4b,2b,4b\n\
+	.long	1b,4b,2b,4b,5b,4b\n\
 	.previous"						\
 	: "=&a" (oldval), "=&r" (ret), "+m" (*uaddr),		\
 	  "=&r" (tem)						\
@@ -111,7 +111,7 @@ futex_atomic_cmpxchg_inatomic(int __user
 		return -EFAULT;
 
 	__asm__ __volatile__(
-		"1:	" LOCK_PREFIX "cmpxchgl %3, %1		\n"
+		"1:	" LOCK_PREFIX "\n 4: cmpxchgl %3, %1	\n"
 
 		"2:	.section .fixup, \"ax\"			\n"
 		"3:	mov     %2, %0				\n"
@@ -120,7 +120,7 @@ futex_atomic_cmpxchg_inatomic(int __user
 
 		"	.section __ex_table, \"a\"		\n"
 		"	.align  8				\n"
-		"	.long   1b,3b				\n"
+		"	.long   1b,3b,4b,3b			\n"
 		"	.previous				\n"
 
 		: "=a" (oldval), "+m" (*uaddr)
Index: linux-2.6/include/asm-x86_64/futex.h
===================================================================
--- linux-2.6.orig/include/asm-x86_64/futex.h	2008-01-22 13:13:10.000000000 +0100
+++ linux-2.6/include/asm-x86_64/futex.h	2008-01-22 13:13:49.000000000 +0100
@@ -27,7 +27,7 @@
 "1:	movl	%2, %0\n\
 	movl	%0, %3\n"					\
 	insn "\n"						\
-"2:	" LOCK_PREFIX "cmpxchgl %3, %2\n\
+"2:	" LOCK_PREFIX "\n 5: cmpxchgl %3, %2\n\
 	jnz	1b\n\
 3:	.section .fixup,\"ax\"\n\
 4:	mov	%5, %1\n\
@@ -35,7 +35,7 @@
 	.previous\n\
 	.section __ex_table,\"a\"\n\
 	.align	8\n\
-	.quad	1b,4b,2b,4b\n\
+	.quad	1b,4b,2b,4b,5b,4b\n\
 	.previous"						\
 	: "=&a" (oldval), "=&r" (ret), "=m" (*uaddr),		\
 	  "=&r" (tem)						\
@@ -101,7 +101,7 @@ futex_atomic_cmpxchg_inatomic(int __user
 		return -EFAULT;
 
 	__asm__ __volatile__(
-		"1:	" LOCK_PREFIX "cmpxchgl %3, %1		\n"
+		"1:	" LOCK_PREFIX "\n 4: cmpxchgl %3, %1	\n"
 
 		"2:	.section .fixup, \"ax\"			\n"
 		"3:	mov     %2, %0				\n"
@@ -110,7 +110,7 @@ futex_atomic_cmpxchg_inatomic(int __user
 
 		"	.section __ex_table, \"a\"		\n"
 		"	.align  8				\n"
-		"	.quad   1b,3b				\n"
+		"	.quad   1b,3b,4b,3b			\n"
 		"	.previous				\n"
 
 		: "=a" (oldval), "=m" (*uaddr)

  reply	other threads:[~2008-01-22 20:20 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-21 20:47 Chuck Ebbert
2008-01-21 21:25 ` Chuck Ebbert
2008-01-22  5:26 ` Andi Kleen
2008-01-22 12:35   ` Thomas Gleixner
2008-01-22 20:19     ` Chuck Ebbert [this message]
2008-02-06 23:10       ` [stable] " Greg KH
2008-02-06 23:36         ` Linus Torvalds
2008-02-06 23:43           ` Ingo Molnar
2008-02-07  0:00             ` Greg KH
2008-02-07  6:55             ` Greg KH
2008-02-07 12:16         ` Thomas Gleixner

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