70 lines
2.7 KiB
ArmAsm
70 lines
2.7 KiB
ArmAsm
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/**
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* \file
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* <!--
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* This file is part of BeRTOS.
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*
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* Bertos is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*
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* As a special exception, you may use this file as part of a free software
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* library without restriction. Specifically, if other files instantiate
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* templates or use macros or inline functions from this file, or you compile
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* this file and link it with other files to produce an executable, this
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* file does not by itself cause the resulting executable to be covered by
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* the GNU General Public License. This exception does not however
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* invalidate any other reasons why the executable file might be covered by
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* the GNU General Public License.
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*
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* Copyright 2004, 2008 Develer S.r.l. (http://www.develer.com/)
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* Copyright 1999, 2000, 2001 Bernie Innocenti <bernie@codewiz.org>
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* -->
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*
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* \author Bernie Innocenti <bernie@codewiz.org>
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*
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* \brief i386 context switch
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*
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* x86 function calling convention:
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* --------------------------------
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* arguments | callee-saved | extra caller-saved | return
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* [callee-clobbered] | | [callee-clobbered] |
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* -------------------------------------------------------------------------
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* eax edx ecx | ebx edi esi ebp [*] | <none> | eax, edx
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*
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* [*] In the frame-pointers case rbp must hold a base address for the
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* current stack frame.
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*
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* asm_switch_context() can be considered as a normal function call, so we need
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* to save all the callee-clobbered registers minus the return registers.
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*/
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#ifdef __APPLE__
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// This workaround is necessary to compile under OS X assembler.
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#define SWITCH_CONTEXT _asm_switch_context
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#else
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#define SWITCH_CONTEXT asm_switch_context
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#endif
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/* void asm_switch_context(void ** new_sp [sp+4], void ** save_sp [sp+8]) */
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.globl SWITCH_CONTEXT
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SWITCH_CONTEXT:
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pushl %ebp
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pushl %ecx
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movl 0x10(%esp),%ebp /* ebp = save_sp */
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movl %esp,(%ebp) /* *save_sp = esp */
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movl 0x0c(%esp),%ebp /* ebp = new_sp */
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movl (%ebp),%esp /* esp = *new_sp */
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popl %ecx
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popl %ebp
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ret
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