185 lines
4.6 KiB
ArmAsm
185 lines
4.6 KiB
ArmAsm
/*
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* Mach Operating System
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* Copyright (c) 1992, 1991 Carnegie Mellon University
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* All Rights Reserved.
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*
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* Permission to use, copy, modify and distribute this software and its
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* documentation is hereby granted, provided that both the copyright
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* notice and this permission notice appear in all copies of the
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* software, derivative works or modified versions, and any portions
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* thereof, and that both notices appear in supporting documentation.
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*
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* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
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* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
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* ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
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*
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* Carnegie Mellon requests users of this software to return to
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*
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* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
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* School of Computer Science
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* Carnegie Mellon University
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* Pittsburgh PA 15213-3890
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*
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* any improvements or extensions that they make and grant Carnegie Mellon
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* the rights to redistribute these changes.
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*
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* from: Mach, Revision 2.2 92/04/04 11:34:13 rpd
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* $Id: real_prot.S,v 1.5 1997/02/22 09:29:54 peter Exp $
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*/
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/*
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Copyright 1988, 1989, 1990, 1991, 1992
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by Intel Corporation, Santa Clara, California.
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All Rights Reserved
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Permission to use, copy, modify, and distribute this software and
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its documentation for any purpose and without fee is hereby
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granted, provided that the above copyright notice appears in all
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copies and that both the copyright notice and this permission notice
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appear in supporting documentation, and that the name of Intel
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not be used in advertising or publicity pertaining to distribution
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of the software without specific, written prior permission.
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INTEL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE
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INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS,
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IN NO EVENT SHALL INTEL BE LIABLE FOR ANY SPECIAL, INDIRECT, OR
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CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
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LOSS OF USE, DATA OR PROFITS, WHETHER IN ACTION OF CONTRACT,
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NEGLIGENCE, OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
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WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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/*
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* Copyright (C) 1994 by HOSOKAWA, Tatsumi <hosokawa@jp.FreeBSD.org>
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*
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* This software may be used, modified, copied, and distributed, in
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* both source and binary form provided that the above copyright and
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* these terms are retained. Under no circumstances is the author
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* responsible for the proper functioning of this software, nor does
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* the author assume any responsibility for damages incurred with its
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* use.
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*
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* Sep., 1994 Implemented on FreeBSD 1.1.5.1R (Toshiba AVS001WD)
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*/
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/*
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* Modified for APM BIOS initializer by HOSOKAWA Tatsumi
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*
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* See also locore.s.
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* (This file is based directly on /sys/i386/boot/biosboot/asm.S)
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*/
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.file "real_prot.S"
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#include "real_prot.h"
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#include "apm_segments.h"
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#include "apm_bios.h"
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CR0_PE_ON = 0x1
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CR0_PE_OFF = 0xfffffffe
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.text
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/*
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*
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* real_to_prot()
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* transfer from real mode to protected mode.
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*/
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ENTRY(real_to_prot)
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/* guarantee that interrupt is disabled when in prot mode */
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cli
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/*
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* deleted for APM initializer by HOSOKAWA Tatsumi
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* <hosoakwa@jp.FreeBSD.org>
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*/
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#if 0
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/* load the gdtr */
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addr32
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data32
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lgdt EXT(Gdtr)
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#endif
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/* set the PE bit of CR0 */
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mov %cr0, %eax
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data32
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or $CR0_PE_ON, %eax
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mov %eax, %cr0
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/*
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* make intrasegment jump to flush the processor pipeline and
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* reload CS register
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*/
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data32
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ljmp $(APM_INIT_CS_SEL), $xprot
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xprot:
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/*
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* we are in USE32 mode now
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* set up the protected mode segment registers : DS, SS, ES
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*/
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movw $(APM_INIT_DS_SEL), %ax /* data segment */
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mov %ax, %ds /* gas would waste a prefix byte for movw */
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mov %ax, %ss
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mov %ax, %es
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/* load idtr so that we can enable interrupts */
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lidt EXT(Idtr_prot)
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ret
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/*
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*
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* prot_to_real()
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* transfer from protected mode to real mode
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*
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*/
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ENTRY(prot_to_real)
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/* Prepare %ax while we're still in a mode that gas understands. */
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movw $(APM_INIT_DS16_SEL), %ax
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/* Change to use16 mode. */
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ljmp $(APM_INIT_CS16_SEL), $x16
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x16:
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mov %ax, %ds
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mov %ax, %ss
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mov %ax, %es
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/* clear the PE bit of CR0 */
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mov %cr0, %eax
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data32
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and $CR0_PE_OFF, %eax
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mov %eax, %cr0
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/*
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* make intersegment jmp to flush the processor pipeline
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* and reload CS register
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*/
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data32
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ljmp $(APM_OURADDR>>4), $xreal
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xreal:
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/*
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* we are in real mode now
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* set up the real mode segment registers : DS, SS, ES
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*/
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mov %cs, %ax
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mov %ax, %ds
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mov %ax, %ss
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mov %ax, %es
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/* load idtr so that we can enable interrupts */
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addr32
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data32
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lidt EXT(Idtr_real)
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data32
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ret
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