Messages in this thread Patches in this message | | | Date | Thu, 7 Feb 2008 13:16:04 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [stable] The SMP alternatives code breaks exception fixup? |
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On Wed, 6 Feb 2008, Greg KH wrote:
> On Tue, Jan 22, 2008 at 03:19:33PM -0500, Chuck Ebbert wrote: > > 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> > > I don't see this in Linus's tree, am I just missing it? Do you have a > git commit id?
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=9d55b9923a1b7ea8193b8875c57ec940dc2ff027
I did a simpler version by just replacing LOCK_PREFIX with lock. The reason is, that we would need a separate implementation for __futex_atomic_op1() as well, due to:
case FUTEX_OP_ADD: __futex_atomic_op1(LOCK_PREFIX "xaddl %0, %2", ret, oldval,
And it's not really worth the trouble.
Backport to 2.6.24 and 2.6.23 attached.
Thanks, tglxSubject: x86: replace LOCK_PREFIX in futex.h From: Thomas Gleixner <tglx@linutronix.de> Date: Thu, 07 Feb 2008 13:05:19 +0100
The exception fixup for the futex macros __futex_atomic_op1/2 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
A possible solution would be to add another fixup after the LOCK_PREFIX, so both the LOCK and NOP case have their own entry in the exception table, but it's not really worth the trouble.
Simply replace LOCK_PREFIX with lock and keep those untouched by SMP alternatives.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Index: linux-2.6.23/include/asm-i386/futex.h =================================================================== --- linux-2.6.23.orig/include/asm-i386/futex.h 2008-02-07 13:08:03.000000000 +0100 +++ linux-2.6.23/include/asm-i386/futex.h 2008-02-07 13:09:39.000000000 +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 cmpxchgl %3, %2\n\ jnz 1b\n\ 3: .section .fixup,\"ax\"\n\ 4: mov %5, %1\n\ @@ -68,7 +68,7 @@ futex_atomic_op_inuser (int encoded_op, #endif switch (op) { case FUTEX_OP_ADD: - __futex_atomic_op1(LOCK_PREFIX "xaddl %0, %2", ret, + __futex_atomic_op1("lock xaddl %0, %2", ret, oldval, uaddr, oparg); break; case FUTEX_OP_OR: @@ -111,7 +111,7 @@ futex_atomic_cmpxchg_inatomic(int __user return -EFAULT; __asm__ __volatile__( - "1: " LOCK_PREFIX "cmpxchgl %3, %1 \n" + "1: lock cmpxchgl %3, %1 \n" "2: .section .fixup, \"ax\" \n" "3: mov %2, %0 \n" Index: linux-2.6.23/include/asm-x86_64/futex.h =================================================================== --- linux-2.6.23.orig/include/asm-x86_64/futex.h 2008-02-07 13:08:03.000000000 +0100 +++ linux-2.6.23/include/asm-x86_64/futex.h 2008-02-07 13:09:39.000000000 +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 cmpxchgl %3, %2\n\ jnz 1b\n\ 3: .section .fixup,\"ax\"\n\ 4: mov %5, %1\n\ @@ -62,7 +62,7 @@ futex_atomic_op_inuser (int encoded_op, __futex_atomic_op1("xchgl %0, %2", ret, oldval, uaddr, oparg); break; case FUTEX_OP_ADD: - __futex_atomic_op1(LOCK_PREFIX "xaddl %0, %2", ret, oldval, + __futex_atomic_op1("lock xaddl %0, %2", ret, oldval, uaddr, oparg); break; case FUTEX_OP_OR: @@ -101,7 +101,7 @@ futex_atomic_cmpxchg_inatomic(int __user return -EFAULT; __asm__ __volatile__( - "1: " LOCK_PREFIX "cmpxchgl %3, %1 \n" + "1: lock cmpxchgl %3, %1 \n" "2: .section .fixup, \"ax\" \n" "3: mov %2, %0 \n"Subject: x86: replace LOCK_PREFIX in futex.h From: Thomas Gleixner <tglx@linutronix.de> Date: Thu, 07 Feb 2008 13:06:02 +0100
The exception fixup for the futex macros __futex_atomic_op1/2 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
A possible solution would be to add another fixup after the LOCK_PREFIX, so both the LOCK and NOP case have their own entry in the exception table, but it's not really worth the trouble.
Simply replace LOCK_PREFIX with lock and keep those untouched by SMP alternatives.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Index: linux-2.6.24/include/asm-x86/futex_32.h =================================================================== --- linux-2.6.24.orig/include/asm-x86/futex_32.h 2008-02-07 13:05:39.000000000 +0100 +++ linux-2.6.24/include/asm-x86/futex_32.h 2008-02-07 13:07:20.000000000 +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 cmpxchgl %3, %2\n\ jnz 1b\n\ 3: .section .fixup,\"ax\"\n\ 4: mov %5, %1\n\ @@ -68,7 +68,7 @@ futex_atomic_op_inuser (int encoded_op, #endif switch (op) { case FUTEX_OP_ADD: - __futex_atomic_op1(LOCK_PREFIX "xaddl %0, %2", ret, + __futex_atomic_op1("lock xaddl %0, %2", ret, oldval, uaddr, oparg); break; case FUTEX_OP_OR: @@ -111,7 +111,7 @@ futex_atomic_cmpxchg_inatomic(int __user return -EFAULT; __asm__ __volatile__( - "1: " LOCK_PREFIX "cmpxchgl %3, %1 \n" + "1: lock cmpxchgl %3, %1 \n" "2: .section .fixup, \"ax\" \n" "3: mov %2, %0 \n" Index: linux-2.6.24/include/asm-x86/futex_64.h =================================================================== --- linux-2.6.24.orig/include/asm-x86/futex_64.h 2008-02-07 13:05:39.000000000 +0100 +++ linux-2.6.24/include/asm-x86/futex_64.h 2008-02-07 13:06:45.000000000 +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 cmpxchgl %3, %2\n\ jnz 1b\n\ 3: .section .fixup,\"ax\"\n\ 4: mov %5, %1\n\ @@ -62,7 +62,7 @@ futex_atomic_op_inuser (int encoded_op, __futex_atomic_op1("xchgl %0, %2", ret, oldval, uaddr, oparg); break; case FUTEX_OP_ADD: - __futex_atomic_op1(LOCK_PREFIX "xaddl %0, %2", ret, oldval, + __futex_atomic_op1("lock xaddl %0, %2", ret, oldval, uaddr, oparg); break; case FUTEX_OP_OR: @@ -101,7 +101,7 @@ futex_atomic_cmpxchg_inatomic(int __user return -EFAULT; __asm__ __volatile__( - "1: " LOCK_PREFIX "cmpxchgl %3, %1 \n" + "1: lock cmpxchgl %3, %1 \n" "2: .section .fixup, \"ax\" \n" "3: mov %2, %0 \n" | |