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      1 /*	$NetBSD: swapcontext.S,v 1.1 2014/09/03 19:34:25 matt Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2001 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Klaus Klein.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #include "SYS.h"
     33 #include "assym.h"
     34 
     35 __RCSID("$NetBSD: swapcontext.S,v 1.1 2014/09/03 19:34:25 matt Exp $")
     36 
     37 #define	CALLFRAME_LR	(-1*4)
     38 #define	CALLFRAME_UCP	(-2*4)
     39 #define	CALLFRAME_OUCP	(-3*4)
     40 #define	CALLFRAME_GP	(-4*4)
     41 #define	CALLFRAME_SP	(-5*4)
     42 #define	CALLFRAME_LEN	(-CALLFRAME_SP)
     43 
     44 ENTRY(swapcontext)
     45 	l.sw	CALLFRAME_LR(r1),lr		# save link register
     46 	l.sw	CALLFRAME_OUCP(r1),r3		# save oucp
     47 	l.sw	CALLFRAME_UCP(r1),r4		# save ucp
     48 	l.sw	CALLFRAME_SP(r1),r1		# set up stack chain
     49 #ifdef __PIC__
     50 	l.sw	CALLFRAME_GP(r1),r16		# save r16
     51 	PIC_GOTSETUP(r16)			# setup got pointer
     52 #endif
     53 	l.addi	r1,r1,-CALLFRAME_LEN		# adjust stack
     54 	l.jal	PLT(_C_LABEL(_getcontext))	# getcontext(oucp)
     55 	l.nop					# -- delay slot --
     56 	l.sfeqi	r11,0				# error?
     57 	l.bnf	1f				#   yes, cleanup
     58 	l.nop					#   -- delay slot --
     59 	l.addi	r5,r1,CALLFRAME_LEN		# adjust stack
     60 	l.lwz	r4,CALLFRAME_OUCP(r5)		# load oucp for adjustment
     61 	l.sw	UC_GREGS_PC(r4),lr		# pc <- lr
     62 	l.sw	UC_GREGS_SP(r4),r1		# adjust sp
     63 	l.lwz	r3,CALLFRAME_UCP(r5)		# load ucp
     64 	# can't do a tail call due to needing r16 for PLT
     65 	l.jal	PLT(_C_LABEL(setcontext))	# setcontext(ucp)
     66 	l.nop					# -- delay slot --
     67 1:
     68 	l.addi	r1,r1,CALLFRAME_LEN		# restore stack
     69 #ifdef __PIC__
     70 	l.lwz	r16,CALLFRAME_GP(r1)		# restore r16
     71 #endif
     72 	l.lwz	lr,CALLFRAME_LR(r1)		# refetch lr
     73 	l.jr	lr				# simply return
     74 	l.nop					# -- delay slot --
     75 END(swapcontext)
     76