/*      $NetBSD: swapcontext.S,v 1.8 2018/02/28 20:51:58 uwe 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 1.8 2018/02/28 20:51:58 uwe Exp $")

#define XCALLFRAMELEN   (((2+3)*SZREG + CALLFRAMELEN - 1) & -CALLFRAMELEN)
#define XCALLFRAME_R30  (XCALLFRAMELEN-1*SZREG)
#define XCALLFRAME_UCP  (XCALLFRAMELEN-2*SZREG)
#define XCALLFRAME_OUCP (XCALLFRAMELEN-3*SZREG)

ENTRY(swapcontext)
        stwu    %r1,-XCALLFRAMELEN(%r1)         # set up new stack frame
        mflr    %r0
        stw     %r0,XCALLFRAMELEN+CALLFRAME_LR(%r1)     # save link register
        stw     %r3,XCALLFRAME_OUCP(%r1)        # must save oucp
        stw     %r4,XCALLFRAME_UCP(%r1)         # must save ucp
#ifdef __PIC__
        stw     %r30,XCALLFRAME_R30(%r1)        # must save r30
        PIC_TOCSETUP(swapcontext,%r30)          # setup toc pointer
#endif
        bl      PIC_PLT(_C_LABEL(_getcontext))  # getcontext(oucp)
        cmpwi   %r3,0
        bne     1f
        lwz     %r11,XCALLFRAME_OUCP(%r1)       # load oucp for adjustment
        lwz     %r0,XCALLFRAMELEN+CALLFRAME_LR(%r1)
        stw     %r0,UC_GREGS_PC(%r11)           # pc <- lr
        addi    %r0,%r1,XCALLFRAMELEN
        stw     %r0,UC_GREGS_R1(%r11)           # adjust sp
#ifdef __PIC__
        lwz     %r0,XCALLFRAME_R30(%r1)
        stw     %r0,UC_GREGS_R30(%r11)          # caller's r30
#endif
        lwz     %r3,XCALLFRAME_UCP(%r1)         # load ucp
        bl      PIC_PLT(_C_LABEL(setcontext))   # setcontext(ucp)
1:
        lwz     %r0,XCALLFRAMELEN+CALLFRAME_LR(%r1)
#ifdef __PIC__
        lwz     %r30,XCALLFRAME_R30(%r1)
#endif
        mtlr    %r0
        addi    %r1,%r1,XCALLFRAMELEN
        blr
END(swapcontext)