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      1 /* $NetBSD: swapcontext.S,v 1.4 2018/11/23 12:39:18 skrll Exp $ */
      2 
      3 /*-
      4  * Copyright (c) 2014 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Matt Thomas of 3am Software Foundry.
      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 <machine/asm.h>
     33 #include "assym.h"
     34 
     35 #if defined(LIBC_SCCS) && !defined(lint)
     36         RCSID("$NetBSD: swapcontext.S,v 1.4 2018/11/23 12:39:18 skrll Exp $")
     37 #endif /* LIBC_SCCS && !lint */
     38 
     39 /* LINTSTUB: int swapcontext(ucontext_t * restrict, ucontext_t * restrict); */
     40 
     41 ENTRY(swapcontext)
     42 	sub	sp, sp, #32		/* allocate stack frame */
     43 	stp	x29, x30, [sp, #16]	/* save FP & LR */
     44 	add	x29, sp, #16		/* new FP */
     45 	stp	x0, x1, [sp, #0]	/* save oucp (x0) & ucp (x1) */
     46 
     47 	bl	_C_LABEL(_getcontext)	/* getcontext(oucp) */
     48 	mov	x3, x0			/* save return value */
     49 
     50 	ldp	x2, x0, [sp, #0]	/* load oucp (x2) & ucp (x0) */
     51 	ldp	x29, x30, [sp, #16]	/* restore FP & LR */
     52 	add	sp, sp, #32		/* free stack frame */
     53 
     54 	/*
     55 	 * Assume _getcontext succeeded.
     56 	 */
     57 	mov	x4, sp			/* Get SP */
     58 	str	x4, [x2, #_UC_REGS_SP]	/* Adjust saved SP. */
     59 	str	x30, [x2, #_UC_REGS_PC]	/* Adjust saved PC. */
     60 
     61 	cbnz	x3, 1f
     62 	b	_C_LABEL(setcontext)	/* setcontext if getcontext succeeded */
     63 1:
     64 	mov	x0, x3			/* restore getcontext return value */
     65 	ret				/* return on error from getcontext */
     66 END(swapcontext)
     67