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diff --git a/kitten/arch/x86_64/lib/thunk.S b/kitten/arch/x86_64/lib/thunk.S
new file mode 100644
index 0000000..802cdff
--- /dev/null
+++ b/kitten/arch/x86_64/lib/thunk.S
@@ -0,0 +1,93 @@
+	/*
+	 * Save registers before calling assembly functions. This avoids
+	 * disturbance of register allocation in some inline assembly constructs.
+	 * Copyright 2001,2002 by Andi Kleen, SuSE Labs.
+	 * Subject to the GNU public license, v.2. No warranty of any kind.
+	 * $Id: thunk.S,v 1.2 2002/03/13 20:06:58 ak Exp $
+	 */
+
+	#include <lwk/linkage.h>
+	#include <arch/dwarf2.h>
+	#include <arch/calling.h>			
+	#include <arch/rwlock.h>
+		
+	/* rdi:	arg1 ... normal C conventions. rax is saved/restored. */ 	
+	.macro thunk name,func
+	.globl \name
+\name:	
+	CFI_STARTPROC
+	SAVE_ARGS
+	call \func
+	jmp  restore
+	CFI_ENDPROC
+	.endm
+
+	/* rdi:	arg1 ... normal C conventions. rax is passed from C. */ 	
+	.macro thunk_retrax name,func
+	.globl \name
+\name:	
+	CFI_STARTPROC
+	SAVE_ARGS
+	call \func
+	jmp  restore_norax
+	CFI_ENDPROC
+	.endm
+	
+
+#if 0
+	.section .sched.text
+#ifdef CONFIG_RWSEM_XCHGADD_ALGORITHM
+	thunk rwsem_down_read_failed_thunk,rwsem_down_read_failed
+	thunk rwsem_down_write_failed_thunk,rwsem_down_write_failed
+	thunk rwsem_wake_thunk,rwsem_wake
+	thunk rwsem_downgrade_thunk,rwsem_downgrade_wake
+#endif	
+	
+	thunk __down_failed,__down
+	thunk_retrax __down_failed_interruptible,__down_interruptible
+	thunk_retrax __down_failed_trylock,__down_trylock
+	thunk __up_wakeup,__up
+#endif
+	
+	/* SAVE_ARGS below is used only for the .cfi directives it contains. */
+	CFI_STARTPROC
+	SAVE_ARGS
+restore:
+	RESTORE_ARGS
+	ret	
+	CFI_ENDPROC
+	
+	CFI_STARTPROC
+	SAVE_ARGS
+restore_norax:	
+	RESTORE_ARGS 1
+	ret
+	CFI_ENDPROC
+
+/* Support for read/write spinlocks. */
+	.text
+/* rax:	pointer to rwlock_t */	
+ENTRY(__write_lock_failed)
+	lock
+	addl $RW_LOCK_BIAS,(%rax)
+1:	rep
+	nop
+	cmpl $RW_LOCK_BIAS,(%rax)
+	jne 1b
+	lock 
+	subl $RW_LOCK_BIAS,(%rax)
+	jnz  __write_lock_failed
+	ret
+
+/* rax:	pointer to rwlock_t */	
+ENTRY(__read_lock_failed)
+	lock
+	incl (%rax)
+1:	rep
+	nop
+	cmpl $1,(%rax)
+	js 1b
+	lock
+	decl (%rax)
+	js __read_lock_failed
+	ret