Move futex support code from <arch>/support.s into linux compat directory.

Implement all futex atomic operations in assembler to not depend on the
fuword() that does not allow to distinguish between -1 and failure return.
Correctly return 0 from atomic operations on success.

In collaboration with:	rdivacky
Tested by:	Scot Hetzel <swhetzel gmail com>, Milos Vyletel <mvyletel mzm cz>
Sponsored by:	Google SoC 2007

9 files changed, 303 insertions, 166 deletions

diff --git a/sys/amd64/amd64/support.S b/sys/amd64/amd64/support.S
index c828877..782cde9 100644
--- a/sys/amd64/amd64/support.S
+++ b/sys/amd64/amd64/support.S
@@ -671,49 +671,6 @@ ENTRY(longjmp)
 	incl	%eax
 	ret
 
-/*****************************************************************************/
-/* linux_futex support                                                       */
-/*****************************************************************************/
-
-futex_fault:
-	movq	$0,PCB_ONFAULT(%rcx)
-	movq	$-EFAULT,%rax
-	ret
-
-ENTRY(futex_xchgl)
-	movq	PCPU(CURPCB),%rcx
-	movq	$futex_fault,PCB_ONFAULT(%rcx)
-
-	movq	$VM_MAXUSER_ADDRESS-4,%rax
-	cmpq	%rax,%rsi
-	ja	futex_fault
-
-#ifdef SMP
-	lock
-#endif
-	xchgl	%edi,(%rsi)
-	movl	%edi,(%rdx)
-	xorl	%eax,%eax
-	movq	%rax,PCB_ONFAULT(%rcx)
-	ret
-
-ENTRY(futex_addl)
-	movq	PCPU(CURPCB),%rcx
-	movq	$futex_fault,PCB_ONFAULT(%rcx)
-
-	movq	$VM_MAXUSER_ADDRESS-4,%rax
-	cmpq	%rax,%rsi
-	ja	futex_fault
-
-#ifdef SMP
-	lock
-#endif
-	xaddl	%edi,(%rsi)
-	movl	%edi,(%rdx)
-	xorl	%eax,%eax
-	movq	%rax,PCB_ONFAULT(%rcx)
-	ret
-
 /*
  * Support for BB-profiling (gcc -a).  The kernbb program will extract
  * the data from the kernel.
diff --git a/sys/amd64/linux32/linux32_support.s b/sys/amd64/linux32/linux32_support.s
new file mode 100644
index 0000000..42375c3
--- /dev/null
+++ b/sys/amd64/linux32/linux32_support.s
@@ -0,0 +1,124 @@
+/*-
+ * Copyright (c) 2007 Konstantin Belousov
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#include "linux32_assym.h"		/* system definitions */
+#include <machine/asmacros.h>		/* miscellaneous asm macros */
+
+#include "assym.s"
+
+futex_fault:
+	movq	$0,PCB_ONFAULT(%r8)
+	movl	$-EFAULT,%eax
+	ret
+
+ENTRY(futex_xchgl)
+	movq	PCPU(CURPCB),%r8
+	movq	$futex_fault,PCB_ONFAULT(%r8)
+	movq	$VM_MAXUSER_ADDRESS-4,%rax
+	cmpq	%rax,%rsi
+	ja	futex_fault
+	xchgl	%edi,(%rsi)
+	movl	%edi,(%rdx)
+	xorl	%eax,%eax
+	movq	%rax,PCB_ONFAULT(%r8)
+	ret
+
+ENTRY(futex_addl)
+	movq	PCPU(CURPCB),%r8
+	movq	$futex_fault,PCB_ONFAULT(%r8)
+	movq	$VM_MAXUSER_ADDRESS-4,%rax
+	cmpq	%rax,%rsi
+	ja	futex_fault
+#ifdef SMP
+	lock
+#endif
+	xaddl	%edi,(%rsi)
+	movl	%edi,(%rdx)
+	xorl	%eax,%eax
+	movq	%rax,PCB_ONFAULT(%r8)
+	ret
+
+ENTRY(futex_orl)
+	movq	PCPU(CURPCB),%r8
+	movq	$futex_fault,PCB_ONFAULT(%r8)
+	movq	$VM_MAXUSER_ADDRESS-4,%rax
+	cmpq	%rax,%rsi
+	ja	futex_fault
+	movl	(%rsi),%eax
+1:	movl	%eax,%ecx
+	orl	%edi,%ecx
+#ifdef SMP
+	lock
+#endif
+	cmpxchgl %ecx,(%rsi)
+	jnz	1b
+	movl	%eax,(%rdx)
+	xorl	%eax,%eax
+	movq	%rax,PCB_ONFAULT(%r8)
+	ret
+
+ENTRY(futex_andl)
+	movq	PCPU(CURPCB),%r8
+	movq	$futex_fault,PCB_ONFAULT(%r8)
+	movq	$VM_MAXUSER_ADDRESS-4,%rax
+	cmpq	%rax,%rsi
+	ja	futex_fault
+	movl	(%rsi),%eax
+1:	movl	%eax,%ecx
+	andl	%edi,%ecx
+#ifdef SMP
+	lock
+#endif
+	cmpxchgl %ecx,(%rsi)
+	jnz	1b
+	movl	%eax,(%rdx)
+	xorl	%eax,%eax
+	movq	%rax,PCB_ONFAULT(%r8)
+	ret
+
+ENTRY(futex_xorl)
+	movq	PCPU(CURPCB),%r8
+	movq	$futex_fault,PCB_ONFAULT(%r8)
+	movq	$VM_MAXUSER_ADDRESS-4,%rax
+	cmpq	%rax,%rsi
+	ja	futex_fault
+	movl	(%rsi),%eax
+1:	movl	%eax,%ecx
+	xorl	%edi,%ecx
+#ifdef SMP
+	lock
+#endif
+	cmpxchgl %ecx,(%rsi)
+	jnz	1b
+	movl	%eax,(%rdx)
+	xorl	%eax,%eax
+	movq	%rax,PCB_ONFAULT(%r8)
+	ret
diff --git a/sys/compat/linux/linux_futex.c b/sys/compat/linux/linux_futex.c
index f3fe997..be719b8 100644
--- a/sys/compat/linux/linux_futex.c
+++ b/sys/compat/linux/linux_futex.c
@@ -90,13 +90,13 @@ static void futex_put(struct futex *);
 static int futex_sleep(struct futex *, struct thread *, unsigned long);
 static int futex_wake(struct futex *, int, struct futex *, int);
 static int futex_atomic_op(struct thread *td, int encoded_op, caddr_t uaddr);
-static int futex_orl(int oparg, caddr_t uaddr, int *oldval);
-static int futex_andl(int oparg, caddr_t uaddr, int *oldval);
-static int futex_xorl(int oparg, caddr_t uaddr, int *oldval);
 
 /* support.s */
 int futex_xchgl(int oparg, caddr_t uaddr, int *oldval);
 int futex_addl(int oparg, caddr_t uaddr, int *oldval);
+int futex_orl(int oparg, caddr_t uaddr, int *oldval);
+int futex_andl(int oparg, caddr_t uaddr, int *oldval);
+int futex_xorl(int oparg, caddr_t uaddr, int *oldval);
 
 int
 linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
@@ -114,8 +114,8 @@ linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
 
 #ifdef	DEBUG
 	if (ldebug(sys_futex))
-		printf(ARGS(futex, "%p, %i, %i"), args->uaddr, args->op,
-		    args->val);
+		printf(ARGS(futex, "%p, %i, %i, *, %p, %i"), args->uaddr, args->op,
+		    args->val, args->uaddr2, args->val3);
 #endif
 
 	switch (args->op) {
@@ -274,7 +274,7 @@ linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
 #ifdef DEBUG
 		if (ldebug(sys_futex))
 			printf("FUTEX_WAKE_OP: %d: uaddr = %p, op = %d, "
-			    "val = %d, uaddr2 = %p, val3 = %d\n",
+			    "val = %x, uaddr2 = %p, val3 = %x\n",
 			    td->td_proc->p_pid, args->uaddr, args->op,
 			    args->val, args->uaddr2, args->val3);
 #endif
@@ -286,8 +286,11 @@ linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
 		 * negative as errors
 		 */
 		op_ret = futex_atomic_op(td, args->val3, args->uaddr2);
+#ifdef DEBUG
+		if (ldebug(sys_futex))
+			printf("futex_atomic_op ret %d\n", op_ret);
+#endif
 		if (op_ret < 0) {
-
 			/* XXX: We don't handle the EFAULT yet. */
 			if (op_ret != -EFAULT) {
 				futex_put(f);
@@ -301,7 +304,6 @@ linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
 
 			FUTEX_SYSTEM_UNLOCK;
 			return (EFAULT);
-
 		}
 
 		ret = futex_wake(f, args->val, NULL, 0);
@@ -327,7 +329,7 @@ linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
 		    args->op);
 		break;
 	}
-	return 0;
+	return (0);
 }
 
 static struct futex *
@@ -401,9 +403,12 @@ futex_sleep(struct futex *f, struct thread *td, unsigned long timeout)
 	TAILQ_REMOVE(&f->f_waiting_proc, wp, wp_list);
 	FUTEX_UNLOCK;
 
+	/* if we got woken up in futex_wake */
 	if ((ret == 0) && (wp->wp_new_futex != NULL)) {
+		/* suspend us on the new futex */
 		ret = futex_sleep(wp->wp_new_futex, td, timeout);
-		futex_put(wp->wp_new_futex);	/* futex_get called in wakeup */
+		/* and release the old one */
+		futex_put(wp->wp_new_futex);
 	}
 
 	free(wp, M_LINUX);
@@ -458,8 +463,10 @@ futex_atomic_op(struct thread *td, int encoded_op, caddr_t uaddr)
 		oparg = 1 << oparg;
 
 #ifdef DEBUG
-	printf("futex_atomic_op: op = %d, cmp = %d, oparg = %d, cmparg = %d, "
-	    "uaddr = %p\n", op, cmp, oparg, cmparg, uaddr);
+	if (ldebug(sys_futex))
+		printf("futex_atomic_op: op = %d, cmp = %d, oparg = %x, "
+		       "cmparg = %x, uaddr = %p\n",
+		       op, cmp, oparg, cmparg, uaddr);
 #endif
 	/* XXX: linux verifies access here and returns EFAULT */
 
@@ -481,70 +488,26 @@ futex_atomic_op(struct thread *td, int encoded_op, caddr_t uaddr)
 		break;
 	default:
 		ret = -ENOSYS;
+		break;
 	}
 
-	if (!ret)
-		switch (cmp) {
-		case FUTEX_OP_CMP_EQ:
-			ret = (oldval == cmparg);
-			break;
-		case FUTEX_OP_CMP_NE:
-			ret = (oldval != cmparg);
-			break;
-		case FUTEX_OP_CMP_LT:
-			ret = (oldval < cmparg);
-			break;
-		case FUTEX_OP_CMP_GE:
-			ret = (oldval >= cmparg);
-			break;
-		case FUTEX_OP_CMP_LE:
-			ret = (oldval <= cmparg);
-			break;
-		case FUTEX_OP_CMP_GT:
-			ret = (oldval > cmparg);
-			break;
-		default:
-			ret = -ENOSYS;
-		}
-
-	return (ret);
-}
-
-static int
-futex_orl(int oparg, caddr_t uaddr, int *oldval)
-{
-	uint32_t ua, ua_old;
-
-	for (;;) {
-		ua = ua_old = fuword32(uaddr);
-		ua |= oparg;
-		if (casuword32((void *)uaddr, ua_old, ua) == ua_old)
-			return ua_old;
-	}
-}
-
-static int
-futex_andl(int oparg, caddr_t uaddr, int *oldval)
-{
-	uint32_t ua, ua_old;
-
-	for (;;) {
-		ua = ua_old = fuword32(uaddr);
-		ua &= oparg;
-		if (casuword32((void *)uaddr, ua_old, ua) == ua_old)
-			return ua_old;
-	}
-}
-
-static int
-futex_xorl(int oparg, caddr_t uaddr, int *oldval)
-{
-	uint32_t ua, ua_old;
-
-	for (;;) {
-		ua = ua_old = fuword32(uaddr);
-		ua ^= oparg;
-		if (casuword32((void *)uaddr, ua_old, ua) == ua_old)
-			return ua_old;
+	if (ret)
+		return (ret);
+
+	switch (cmp) {
+	case FUTEX_OP_CMP_EQ:
+		return (oldval == cmparg);
+	case FUTEX_OP_CMP_NE:
+		return (oldval != cmparg);
+	case FUTEX_OP_CMP_LT:
+		return (oldval < cmparg);
+	case FUTEX_OP_CMP_GE:
+		return (oldval >= cmparg);
+	case FUTEX_OP_CMP_LE:
+		return (oldval <= cmparg);
+	case FUTEX_OP_CMP_GT:
+		return (oldval > cmparg);
+	default:
+		return (-ENOSYS);
 	}
 }
diff --git a/sys/conf/files.amd64 b/sys/conf/files.amd64
index 1eaef53..e2a74bd 100644
--- a/sys/conf/files.amd64
+++ b/sys/conf/files.amd64
@@ -231,9 +231,10 @@ amd64/linux32/linux32_dummy.c	optional	compat_linux32
 amd64/linux32/linux32_locore.s	optional	compat_linux32		\
 	dependency 	"linux32_assym.h"
 amd64/linux32/linux32_machdep.c	optional	compat_linux32
+amd64/linux32/linux32_support.s	optional	compat_linux32
 amd64/linux32/linux32_sysent.c	optional	compat_linux32
 amd64/linux32/linux32_sysvec.c	optional	compat_linux32
-compat/linux/linux_emul.c       optional	compat_linux32
+compat/linux/linux_emul.c	optional	compat_linux32
 compat/linux/linux_file.c	optional	compat_linux32
 compat/linux/linux_futex.c	optional	compat_linux32
 compat/linux/linux_getcwd.c	optional	compat_linux32
diff --git a/sys/conf/files.i386 b/sys/conf/files.i386
index d2999a6..15de89a 100644
--- a/sys/conf/files.i386
+++ b/sys/conf/files.i386
@@ -345,6 +345,7 @@ i386/linux/linux_locore.s	optional compat_linux		\
 	dependency 	"linux_assym.h"
 i386/linux/linux_machdep.c	optional compat_linux
 i386/linux/linux_ptrace.c	optional compat_linux
+i386/linux/linux_support.s	optional compat_linux
 i386/linux/linux_sysent.c	optional compat_linux
 i386/linux/linux_sysvec.c	optional compat_linux
 i386/pci/pci_bus.c		optional pci
diff --git a/sys/conf/files.pc98 b/sys/conf/files.pc98
index e1caa4b..ccfe7ba 100644
--- a/sys/conf/files.pc98
+++ b/sys/conf/files.pc98
@@ -221,6 +221,7 @@ i386/linux/linux_locore.s	optional compat_linux		\
 	dependency 	"linux_assym.h"
 i386/linux/linux_machdep.c	optional compat_linux
 i386/linux/linux_ptrace.c	optional compat_linux
+i386/linux/linux_support.s	optional compat_linux
 i386/linux/linux_sysent.c	optional compat_linux
 i386/linux/linux_sysvec.c	optional compat_linux
 i386/pci/pci_bus.c		optional pci
diff --git a/sys/i386/i386/support.s b/sys/i386/i386/support.s
index 7d49f01..0f34525 100644
--- a/sys/i386/i386/support.s
+++ b/sys/i386/i386/support.s
@@ -1513,51 +1513,6 @@ ENTRY(longjmp)
 	incl	%eax
 	ret
 
-/*****************************************************************************/
-/* linux_futex support                                                       */
-/*****************************************************************************/
-
-futex_fault:
-	movl	$0,PCB_ONFAULT(%ecx)
-	movl	$-EFAULT,%eax
-	ret
-
-ENTRY(futex_xchgl)
-	movl	PCPU(CURPCB),%ecx
-	movl	$futex_fault,PCB_ONFAULT(%ecx)
-	movl	4(%esp),%eax
-	movl	8(%esp),%edx
-	cmpl    $VM_MAXUSER_ADDRESS-4,%edx
-	ja     	futex_fault
-
-#ifdef SMP
-	lock
-#endif
-	xchgl	%eax,(%edx)
-	movl	12(%esp),%edx
-	movl	%eax,(%edx)
-	xorl	%eax,%eax
-	movl	$0,PCB_ONFAULT(%ecx)
-	ret
-
-ENTRY(futex_addl)
-	movl	PCPU(CURPCB),%ecx
-	movl	$futex_fault,PCB_ONFAULT(%ecx)
-	movl	4(%esp),%eax
-	movl	8(%esp),%edx
-	cmpl    $VM_MAXUSER_ADDRESS-4,%edx
-	ja     	futex_fault
-
-#ifdef SMP
-	lock
-#endif
-	xaddl	%eax,(%edx)
-	movl	12(%esp),%edx
-	movl	%eax,(%edx)
-	xorl	%eax,%eax
-	movl	$0,PCB_ONFAULT(%ecx)
-	ret
-
 /*
  * Support for BB-profiling (gcc -a).  The kernbb program will extract
  * the data from the kernel.
diff --git a/sys/i386/linux/linux_support.s b/sys/i386/linux/linux_support.s
new file mode 100644
index 0000000..171d6e7
--- /dev/null
+++ b/sys/i386/linux/linux_support.s
@@ -0,0 +1,127 @@
+/*-
+ * Copyright (c) 2006,2007 Konstantin Belousov
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#include "linux_assym.h"		/* system definitions */
+#include <machine/asmacros.h>		/* miscellaneous asm macros */
+
+#include "assym.s"
+
+futex_fault_decx:
+	movl	PCPU(CURPCB),%ecx
+futex_fault:
+	movl	$0,PCB_ONFAULT(%ecx)
+	movl	$-EFAULT,%eax
+	ret
+
+ENTRY(futex_xchgl)
+	movl	PCPU(CURPCB),%ecx
+	movl	$futex_fault,PCB_ONFAULT(%ecx)
+	movl	4(%esp),%eax
+	movl	8(%esp),%edx
+	cmpl    $VM_MAXUSER_ADDRESS-4,%edx
+	ja     	futex_fault
+	xchgl	%eax,(%edx)
+	movl	12(%esp),%edx
+	movl	%eax,(%edx)
+	xorl	%eax,%eax
+	movl	%eax,PCB_ONFAULT(%ecx)
+	ret
+
+ENTRY(futex_addl)
+	movl	PCPU(CURPCB),%ecx
+	movl	$futex_fault,PCB_ONFAULT(%ecx)
+	movl	4(%esp),%eax
+	movl	8(%esp),%edx
+	cmpl    $VM_MAXUSER_ADDRESS-4,%edx
+	ja     	futex_fault
+#ifdef SMP
+	lock
+#endif
+	xaddl	%eax,(%edx)
+	movl	12(%esp),%edx
+	movl	%eax,(%edx)
+	xorl	%eax,%eax
+	movl	%eax,PCB_ONFAULT(%ecx)
+	ret
+
+ENTRY(futex_orl)
+	movl	PCPU(CURPCB),%ecx
+	movl	$futex_fault_decx,PCB_ONFAULT(%ecx)
+	movl	8(%esp),%edx
+	cmpl    $VM_MAXUSER_ADDRESS-4,%edx
+	ja     	futex_fault
+	movl	(%edx),%eax
+1:	movl	%eax,%ecx
+	orl	4(%esp),%ecx
+#ifdef SMP
+	lock
+#endif
+	cmpxchgl %ecx,(%edx)
+	jnz	1b
+futex_tail:	
+	movl	12(%esp),%edx
+	movl	%eax,(%edx)
+	xorl	%eax,%eax
+	movl	PCPU(CURPCB),%ecx
+	movl	%eax,PCB_ONFAULT(%ecx)
+	ret
+
+ENTRY(futex_andl)
+	movl	PCPU(CURPCB),%ecx
+	movl	$futex_fault_decx,PCB_ONFAULT(%ecx)
+	movl	8(%esp),%edx
+	cmpl    $VM_MAXUSER_ADDRESS-4,%edx
+	ja     	futex_fault
+	movl	(%edx),%eax
+1:	movl	%eax,%ecx
+	andl	4(%esp),%ecx
+#ifdef SMP
+	lock
+#endif
+	cmpxchgl %ecx,(%edx)
+	jnz	1b
+	jmp	futex_tail
+
+ENTRY(futex_xorl)
+	movl	PCPU(CURPCB),%ecx
+	movl	$futex_fault_decx,PCB_ONFAULT(%ecx)
+	movl	8(%esp),%edx
+	cmpl    $VM_MAXUSER_ADDRESS-4,%edx
+	ja     	futex_fault
+	movl	(%edx),%eax
+1:	movl	%eax,%ecx
+	xorl	4(%esp),%ecx
+#ifdef SMP
+	lock
+#endif
+	cmpxchgl %ecx,(%edx)
+	jnz	1b
+	jmp	futex_tail
diff --git a/sys/modules/linux/Makefile b/sys/modules/linux/Makefile
index 1230470..5d956d9 100644
--- a/sys/modules/linux/Makefile
+++ b/sys/modules/linux/Makefile
@@ -14,8 +14,12 @@ SRCS=	linux${SFX}_dummy.c linux_emul.c linux_file.c \
 	linux_socket.c linux_stats.c linux_sysctl.c linux${SFX}_sysent.c \
 	linux${SFX}_sysvec.c linux_uid16.c linux_util.c linux_time.c \
 	opt_inet6.h opt_mac.h opt_compat.h opt_posix.h vnode_if.h \
-	device_if.h bus_if.h
-OBJS=	linux${SFX}_locore.o
+	device_if.h bus_if.h assym.s
+
+# XXX: for assym.s
+SRCS+=  opt_kstack_pages.h opt_nfs.h opt_apic.h opt_compat.h
+
+OBJS=	linux${SFX}_locore.o linux${SFX}_support.o
 
 .if ${MACHINE_ARCH} == "i386"
 SRCS+=	linux_ptrace.c imgact_linux.c opt_cpu.h
@@ -41,6 +45,10 @@ linux${SFX}_locore.o: linux${SFX}_locore.s linux${SFX}_assym.h
 	${CC} -c -x assembler-with-cpp -DLOCORE ${CFLAGS} \
 	    ${.IMPSRC} -o ${.TARGET}
 
+linux${SFX}_support.o: linux${SFX}_support.s assym.s
+	${CC} -c -x assembler-with-cpp -DLOCORE ${CFLAGS} \
+	    ${.IMPSRC} -o ${.TARGET}
+
 linux${SFX}_genassym.o: linux${SFX}_genassym.c linux.h @ machine
 	${CC} -c ${CFLAGS:N-fno-common} ${.IMPSRC}