/*      $NetBSD: swapcontext.S,v 1.1 2014/09/03 19:34:25 matt Exp $     */

/*-
 * Copyright (c) 2001 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Klaus Klein.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
 */

#include "SYS.h"
#include "assym.h"

__RCSID("$NetBSD: swapcontext.S,v 1.1 2014/09/03 19:34:25 matt Exp $")

#define CALLFRAME_LR    (-1*4)
#define CALLFRAME_UCP   (-2*4)
#define CALLFRAME_OUCP  (-3*4)
#define CALLFRAME_GP    (-4*4)
#define CALLFRAME_SP    (-5*4)
#define CALLFRAME_LEN   (-CALLFRAME_SP)

ENTRY(swapcontext)
        l.sw    CALLFRAME_LR(r1),lr             # save link register
        l.sw    CALLFRAME_OUCP(r1),r3           # save oucp
        l.sw    CALLFRAME_UCP(r1),r4            # save ucp
        l.sw    CALLFRAME_SP(r1),r1             # set up stack chain
#ifdef __PIC__
        l.sw    CALLFRAME_GP(r1),r16            # save r16
        PIC_GOTSETUP(r16)                       # setup got pointer
#endif
        l.addi  r1,r1,-CALLFRAME_LEN            # adjust stack
        l.jal   PLT(_C_LABEL(_getcontext))      # getcontext(oucp)
        l.nop                                   # -- delay slot --
        l.sfeqi r11,0                           # error?
        l.bnf   1f                              #   yes, cleanup
        l.nop                                   #   -- delay slot --
        l.addi  r5,r1,CALLFRAME_LEN             # adjust stack
        l.lwz   r4,CALLFRAME_OUCP(r5)           # load oucp for adjustment
        l.sw    UC_GREGS_PC(r4),lr              # pc <- lr
        l.sw    UC_GREGS_SP(r4),r1              # adjust sp
        l.lwz   r3,CALLFRAME_UCP(r5)            # load ucp
        # can't do a tail call due to needing r16 for PLT
        l.jal   PLT(_C_LABEL(setcontext))       # setcontext(ucp)
        l.nop                                   # -- delay slot --
1:
        l.addi  r1,r1,CALLFRAME_LEN             # restore stack
#ifdef __PIC__
        l.lwz   r16,CALLFRAME_GP(r1)            # restore r16
#endif
        l.lwz   lr,CALLFRAME_LR(r1)             # refetch lr
        l.jr    lr                              # simply return
        l.nop                                   # -- delay slot --
END(swapcontext)