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m68k: add swapcontext

pull/21/head
Ariadne Conill 2020-12-06 00:04:50 -06:00
parent c462af8a3c
commit 89536b198d
1 changed files with 39 additions and 0 deletions
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arch/m68k/swapcontext.S Normal file
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/*
* Copyright (c) 2020 Ariadne Conill <ariadne@dereferenced.org>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* This software is provided 'as is' and without any warranty, express or
* implied. In no event shall the authors be liable for any damages arising
* from the use of this software.
*/
#include "defs.h"
ALIAS(swapcontext, __swapcontext)
FUNC(__swapcontext)
move.l 4(%sp), %a0 /* load save ucontext_t pointer from stack */
movem.l %d2-%d7, REG_OFFSET(REG_D2)(%a0) /* preserve $d2 through $d7 */
movem.l %a2-%a6, REG_OFFSET(REG_A2)(%a0) /* preserve $a2 through $a6 */
lea 4(%sp), %a1 /* load stack pointer into $a1 */
move.l %a1, REG_OFFSET(REG_SP)(%a0) /* store $a1 in ucontext */
move.l (%sp), REG_OFFSET(REG_PC)(%a0) /* store return address in ucontext's PC register */
move.l 8(%sp), %a0 /* load new ucontext_t pointer from stack */
move.l REG_OFFSET(REG_SP)(%a0), %sp /* load new stack pointer */
movem.l REG_OFFSET(REG_D2)(%a0), %d2-%d7 /* load $d2 through $d7 */
movem.l REG_OFFSET(REG_A2)(%a0), %a2-%a6 /* load $a2 through $a6 */
clr.l %d0 /* clear $d0 */
move.l REG_OFFSET(REG_PC)(%a0), %a1 /* load jump target */
jmp (%a1) /* jump to *$a1 */
END(__swapcontext)