* The SMP alternatives code breaks exception fixup?
@ 2008-01-21 20:47 Chuck Ebbert
2008-01-21 21:25 ` Chuck Ebbert
2008-01-22 5:26 ` Andi Kleen
0 siblings, 2 replies; 11+ messages in thread
From: Chuck Ebbert @ 2008-01-21 20:47 UTC (permalink / raw)
To: linux-kernel; +Cc: Ingo Molnar, Gerd Hoffmann
Looking at the oops report from this bug:
[bugzilla] https://bugzilla.redhat.com/show_bug.cgi?id=429412
[oops] https://bugzilla.redhat.com/attachment.cgi?id=292260
It was an unhandled page fault (protection violation.)
I tracked it down to the cmpxchg in this code:
include/asm-x86/futex_32.h::futex_atomic_cmpxchg_inatomic()
__asm__ __volatile__(
"1: " LOCK_PREFIX "cmpxchgl %3, %1 \n"
"2: .section .fixup, \"ax\" \n"
"3: mov %2, %0 \n"
" jmp 2b \n"
" .previous \n"
" .section __ex_table, \"a\" \n"
" .align 8 \n"
" .long 1b,3b \n"
" .previous \n"
There is a fixup, so this should never happen. But the lock instruction
was replaced with a nop by the altinstruction code, and that makes the fixup
address wrong. AFAICT we don't fix up the exception table when we replace
a lock with a nop, which makes the fixup table point to the nop instead
of the cmpxchg instruction and causes us to miss the fixup.
^ permalink raw reply [flat|nested] 11+ messages in thread* Re: The SMP alternatives code breaks exception fixup? 2008-01-21 20:47 The SMP alternatives code breaks exception fixup? Chuck Ebbert @ 2008-01-21 21:25 ` Chuck Ebbert 2008-01-22 5:26 ` Andi Kleen 1 sibling, 0 replies; 11+ messages in thread From: Chuck Ebbert @ 2008-01-21 21:25 UTC (permalink / raw) To: Chuck Ebbert; +Cc: linux-kernel, Ingo Molnar, Gerd Hoffmann On 01/21/2008 03:47 PM, Chuck Ebbert wrote: > Looking at the oops report from this bug: > > [bugzilla] https://bugzilla.redhat.com/show_bug.cgi?id=429412 > [oops] https://bugzilla.redhat.com/attachment.cgi?id=292260 > > It was an unhandled page fault (protection violation.) > > I tracked it down to the cmpxchg in this code: > > include/asm-x86/futex_32.h::futex_atomic_cmpxchg_inatomic() > __asm__ __volatile__( > "1: " LOCK_PREFIX "cmpxchgl %3, %1 \n" > "2: .section .fixup, \"ax\" \n" > "3: mov %2, %0 \n" > " jmp 2b \n" > " .previous \n" > " .section __ex_table, \"a\" \n" > " .align 8 \n" > " .long 1b,3b \n" > " .previous \n" > > There is a fixup, so this should never happen. But the lock instruction > was replaced with a nop by the altinstruction code, and that makes the fixup > address wrong. AFAICT we don't fix up the exception table when we replace > a lock with a nop, which makes the fixup table point to the nop instead > of the cmpxchg instruction and causes us to miss the fixup. > The bug reporter has confirmed that booting with "noreplace-smp" prevents the kernel oops. ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: The SMP alternatives code breaks exception fixup? 2008-01-21 20:47 The SMP alternatives code breaks exception fixup? Chuck Ebbert 2008-01-21 21:25 ` Chuck Ebbert @ 2008-01-22 5:26 ` Andi Kleen 2008-01-22 12:35 ` Thomas Gleixner 1 sibling, 1 reply; 11+ messages in thread From: Andi Kleen @ 2008-01-22 5:26 UTC (permalink / raw) To: Chuck Ebbert; +Cc: linux-kernel, Ingo Molnar, Gerd Hoffmann Chuck Ebbert <cebbert@redhat.com> writes: > > There is a fixup, so this should never happen. But the lock instruction > was replaced with a nop by the altinstruction code, and that makes the fixup > address wrong. AFAICT we don't fix up the exception table when we replace > a lock with a nop, which makes the fixup table point to the nop instead > of the cmpxchg instruction and causes us to miss the fixup. Indeed. Nasty issue. A quick fix would be to add another fixup to handle both cases I checked the other LOCK_PREFIX users and they look ok. Does this fix it? -Andi (untested) --- Add exception handlers for both the LOCK and no LOCK prefix case in futex. Hopefully fixes https://bugzilla.redhat.com/show_bug.cgi?id=429412 Signed-off-by: Andi Kleen <ak@suse.de> Index: linux/include/asm-x86/futex.h =================================================================== --- linux.orig/include/asm-x86/futex.h +++ linux/include/asm-x86/futex.h @@ -30,7 +30,7 @@ "1: movl %2, %0\n \ movl %0, %3\n" \ insn "\n" \ -"2: " LOCK_PREFIX "cmpxchgl %3, %2\n \ +"2: " LOCK_PREFIX "\n5: cmpxchgl %3, %2\n \ jnz 1b\n \ 3: .section .fixup,\"ax\"\n \ 4: mov %5, %1\n \ @@ -38,7 +38,7 @@ .previous\n \ .section __ex_table,\"a\"\n \ .align 8\n" \ - _ASM_PTR "1b,4b,2b,4b\n \ + _ASM_PTR "1b,4b,2b,4b,5b,4b\n \ .previous" \ : "=&a" (oldval), "=&r" (ret), "+m" (*uaddr), \ "=&r" (tem) \ ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: The SMP alternatives code breaks exception fixup? 2008-01-22 5:26 ` Andi Kleen @ 2008-01-22 12:35 ` Thomas Gleixner 2008-01-22 20:19 ` Chuck Ebbert 0 siblings, 1 reply; 11+ messages in thread From: Thomas Gleixner @ 2008-01-22 12:35 UTC (permalink / raw) To: Andi Kleen Cc: Andrew Morton, Linus Torvalds, Stable Team, Chuck Ebbert, linux-kernel, Ingo Molnar, Gerd Hoffmann On Tue, 22 Jan 2008, Andi Kleen wrote: > Chuck Ebbert <cebbert@redhat.com> writes: > > > > There is a fixup, so this should never happen. But the lock instruction > > was replaced with a nop by the altinstruction code, and that makes the fixup > > address wrong. AFAICT we don't fix up the exception table when we replace > > a lock with a nop, which makes the fixup table point to the nop instead > > of the cmpxchg instruction and causes us to miss the fixup. > > Indeed. Nasty issue. > > A quick fix would be to add another fixup to handle both cases Agreed. > I checked the other LOCK_PREFIX users and they look ok. Really ? > Does this fix it? No it does not. Chuck tracked it down to include/asm-x86/futex_32.h::futex_atomic_cmpxchg_inatomic() And your patch is changing: __futex_atomic_op2(). That's fine, because we need the fixup for both places. Also your patch is against x86.git and not against mainline. Corrected version below. x86.git needs a different fixup once this hits mainline, as it unifies the 32/64bit versions. That's a long standing bug in both the PI futex and the standard futex code. Needs to go to stable as well. Thanks, tglx -------------> 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-x86/futex_32.h | 8 ++++---- include/asm-x86/futex_64.h | 8 ++++---- 2 files changed, 8 insertions(+), 8 deletions(-) Index: linux-2.6/include/asm-x86/futex_32.h =================================================================== --- linux-2.6.orig/include/asm-x86/futex_32.h 2008-01-22 13:13:10.000000000 +0100 +++ linux-2.6/include/asm-x86/futex_32.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/futex_64.h =================================================================== --- linux-2.6.orig/include/asm-x86/futex_64.h 2008-01-22 13:13:10.000000000 +0100 +++ linux-2.6/include/asm-x86/futex_64.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) ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: The SMP alternatives code breaks exception fixup? 2008-01-22 12:35 ` Thomas Gleixner @ 2008-01-22 20:19 ` Chuck Ebbert 2008-02-06 23:10 ` [stable] " Greg KH 0 siblings, 1 reply; 11+ messages in thread From: Chuck Ebbert @ 2008-01-22 20:19 UTC (permalink / raw) To: Thomas Gleixner Cc: Andi Kleen, Andrew Morton, Linus Torvalds, Stable Team, linux-kernel, Ingo Molnar, Gerd Hoffmann 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) ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [stable] The SMP alternatives code breaks exception fixup? 2008-01-22 20:19 ` Chuck Ebbert @ 2008-02-06 23:10 ` Greg KH 2008-02-06 23:36 ` Linus Torvalds 2008-02-07 12:16 ` Thomas Gleixner 0 siblings, 2 replies; 11+ messages in thread From: Greg KH @ 2008-02-06 23:10 UTC (permalink / raw) To: Chuck Ebbert Cc: Thomas Gleixner, Ingo Molnar, linux-kernel, Andi Kleen, Gerd Hoffmann, Andrew Morton, Linus Torvalds, Stable Team 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? thanks, greg k-h ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [stable] The SMP alternatives code breaks exception fixup? 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 12:16 ` Thomas Gleixner 1 sibling, 1 reply; 11+ messages in thread From: Linus Torvalds @ 2008-02-06 23:36 UTC (permalink / raw) To: Greg KH Cc: Chuck Ebbert, Thomas Gleixner, Ingo Molnar, linux-kernel, Andi Kleen, Gerd Hoffmann, Andrew Morton, Stable Team On Wed, 6 Feb 2008, Greg KH wrote: > > I don't see this in Linus's tree, am I just missing it? Do you have a > git commit id? Isn't this 9d55b9923a1b7ea8193b8875c57ec940dc2ff027 (possibly with 2532ec6d178abc55681d049097d3dc577eaa266c on top)? Linus ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [stable] The SMP alternatives code breaks exception fixup? 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 0 siblings, 2 replies; 11+ messages in thread From: Ingo Molnar @ 2008-02-06 23:43 UTC (permalink / raw) To: Linus Torvalds Cc: Greg KH, Chuck Ebbert, Thomas Gleixner, linux-kernel, Andi Kleen, Gerd Hoffmann, Andrew Morton, Stable Team * Linus Torvalds <torvalds@linux-foundation.org> wrote: > > I don't see this in Linus's tree, am I just missing it? Do you have > > a git commit id? > > Isn't this 9d55b9923a1b7ea8193b8875c57ec940dc2ff027 (possibly with > 2532ec6d178abc55681d049097d3dc577eaa266c on top)? yeah. Greg: note that this is against post-unification asm-x86/futex.h so it wont apply to .24. I've backported the fix to .24 - find it below. (untested but obvious) Ingo -----------------------> Subject: x86: replace LOCK_PREFIX in futex.h From: Thomas Gleixner <tglx@linutronix.de> 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> Signed-off-by: Ingo Molnar <mingo@elte.hu> --- include/asm-x86/futex_32.h | 6 +++--- include/asm-x86/futex_64.h | 6 +++--- 2 files changed, 6 insertions(+), 6 deletions(-) Index: linux-2.6.24/include/asm-x86/futex_32.h =================================================================== --- linux-2.6.24.orig/include/asm-x86/futex_32.h +++ linux-2.6.24/include/asm-x86/futex_32.h @@ -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, oldval, uaddr, oparg); break; case FUTEX_OP_OR: @@ -111,8 +111,8 @@ 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" " jmp 2b \n" Index: linux-2.6.24/include/asm-x86/futex_64.h =================================================================== --- linux-2.6.24.orig/include/asm-x86/futex_64.h +++ linux-2.6.24/include/asm-x86/futex_64.h @@ -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: @@ -101,8 +101,8 @@ 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" " jmp 2b \n" ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [stable] The SMP alternatives code breaks exception fixup? 2008-02-06 23:43 ` Ingo Molnar @ 2008-02-07 0:00 ` Greg KH 2008-02-07 6:55 ` Greg KH 1 sibling, 0 replies; 11+ messages in thread From: Greg KH @ 2008-02-07 0:00 UTC (permalink / raw) To: Ingo Molnar Cc: Linus Torvalds, Chuck Ebbert, Thomas Gleixner, linux-kernel, Andi Kleen, Gerd Hoffmann, Andrew Morton, Stable Team On Thu, Feb 07, 2008 at 12:43:09AM +0100, Ingo Molnar wrote: > > * Linus Torvalds <torvalds@linux-foundation.org> wrote: > > > > I don't see this in Linus's tree, am I just missing it? Do you have > > > a git commit id? > > > > Isn't this 9d55b9923a1b7ea8193b8875c57ec940dc2ff027 (possibly with > > 2532ec6d178abc55681d049097d3dc577eaa266c on top)? > > yeah. > > Greg: note that this is against post-unification asm-x86/futex.h so it > wont apply to .24. > > I've backported the fix to .24 - find it below. (untested but obvious) Thanks for the fix, I'm guessing that this should only go into .24-stable and nothing prior? thanks, greg k-h ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [stable] The SMP alternatives code breaks exception fixup? 2008-02-06 23:43 ` Ingo Molnar 2008-02-07 0:00 ` Greg KH @ 2008-02-07 6:55 ` Greg KH 1 sibling, 0 replies; 11+ messages in thread From: Greg KH @ 2008-02-07 6:55 UTC (permalink / raw) To: Ingo Molnar Cc: Linus Torvalds, Chuck Ebbert, Thomas Gleixner, linux-kernel, Andi Kleen, Gerd Hoffmann, Andrew Morton, Stable Team On Thu, Feb 07, 2008 at 12:43:09AM +0100, Ingo Molnar wrote: > > * Linus Torvalds <torvalds@linux-foundation.org> wrote: > > > > I don't see this in Linus's tree, am I just missing it? Do you have > > > a git commit id? > > > > Isn't this 9d55b9923a1b7ea8193b8875c57ec940dc2ff027 (possibly with > > 2532ec6d178abc55681d049097d3dc577eaa266c on top)? > > yeah. > > Greg: note that this is against post-unification asm-x86/futex.h so it > wont apply to .24. > > I've backported the fix to .24 - find it below. (untested but obvious) unfortunatly it doesn't even compile: distcc[30740] ERROR: compile (null) on localhost failed In file included from include/asm/futex.h:2, from kernel/futex.c:59: include/asm/futex_32.h:72:29: error: macro "__futex_atomic_op1" passed 6 arguments, but takes just 5 In file included from include/asm/futex.h:2, from kernel/futex.c:59: include/asm/futex_32.h: In function 'futex_atomic_op_inuser': include/asm/futex_32.h:71: error: '__futex_atomic_op1' undeclared (first use in this function) include/asm/futex_32.h:71: error: (Each undeclared identifier is reported only once include/asm/futex_32.h:71: error: for each function it appears in.) distcc[30739] ERROR: compile kernel/futex.c on localhost failed make[1]: *** [kernel/futex.o] Error 1 Care to try again? :) thanks, greg k-h ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [stable] The SMP alternatives code breaks exception fixup? 2008-02-06 23:10 ` [stable] " Greg KH 2008-02-06 23:36 ` Linus Torvalds @ 2008-02-07 12:16 ` Thomas Gleixner 1 sibling, 0 replies; 11+ messages in thread From: Thomas Gleixner @ 2008-02-07 12:16 UTC (permalink / raw) To: Greg KH Cc: Chuck Ebbert, Ingo Molnar, linux-kernel, Andi Kleen, Gerd Hoffmann, Andrew Morton, Linus Torvalds, Stable Team [-- Attachment #1: Type: TEXT/PLAIN, Size: 1017 bytes --] 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, tglx [-- Attachment #2: Type: TEXT/PLAIN, Size: 2973 bytes --] Subject: 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" [-- Attachment #3: Type: TEXT/PLAIN, Size: 2913 bytes --] 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" ^ permalink raw reply [flat|nested] 11+ messages in thread
end of thread, other threads:[~2008-02-07 12:17 UTC | newest] Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2008-01-21 20:47 The SMP alternatives code breaks exception fixup? 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 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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