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/* $OpenBSD: real_prot.S,v 1.3 1997/03/31 23:06:31 mickey Exp $ */
/*
* Mach Operating System
* Copyright (c) 1992, 1991 Carnegie Mellon University
* All Rights Reserved.
*
* Permission to use, copy, modify and distribute this software and its
* documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
* ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie Mellon
* the rights to redistribute these changes.
*
* from: Mach, Revision 2.2 92/04/04 11:34:13 rpd
*/
/*
Copyright 1988, 1989, 1990, 1991, 1992
by Intel Corporation, Santa Clara, California.
All Rights Reserved
Permission to use, copy, modify, and distribute this software and
its documentation for any purpose and without fee is hereby
granted, provided that the above copyright notice appears in all
copies and that both the copyright notice and this permission notice
appear in supporting documentation, and that the name of Intel
not be used in advertising or publicity pertaining to distribution
of the software without specific, written prior permission.
INTEL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE
INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS,
IN NO EVENT SHALL INTEL BE LIABLE FOR ANY SPECIAL, INDIRECT, OR
CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
LOSS OF USE, DATA OR PROFITS, WHETHER IN ACTION OF CONTRACT,
NEGLIGENCE, OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
.file "real_prot.S"
#include <machine/asm.h>
#include <machine/specialreg.h>
#define addr32 .byte 0x67
#define data32 .byte 0x66
.data
.globl _codeseg
.globl _Gdtr
#ifndef NO_IDTR
.globl _Idtr_prot
.globl _Idtr_real
#endif
.text
/*
*
* real_to_prot()
* transfer from real mode to protected mode.
*/
ENTRY(real_to_prot)
/* guarantee that interrupts are disabled when in prot mode */
cli
/* load the gdtr */
addr32
data32
lgdt _C_LABEL(Gdtr)
/* set the PE bit of CR0 */
movl %cr0, %eax
data32
orl $CR0_PE, %eax
movl %eax, %cr0
/*
* make intrasegment jump to flush the processor pipeline and
* reload CS register
*/
data32
ljmp $0x08, $1f
1: /*
* we are in USE32 mode now
* set up the protected mode segment registers : DS, SS, ES
*/
movl $0x10, %eax
movl %ax, %ds
movl %ax, %ss
movl %ax, %es
movl %ax, %fs
movl %ax, %gs
#ifndef NO_IDTR
/* load idtr so we can debug */
lidt _Idtr_prot
#endif
ret
/*
*
* prot_to_real()
* transfer from protected mode to real mode
*
*/
ENTRY(prot_to_real)
movl _codeseg, %eax
# movw %ax, 2f
/* Change to use16 mode. */
ljmp $0x18, $1f
1:
/* clear the PE bit of CR0 */
movl %cr0, %eax
data32
andl $~CR0_PE, %eax
movl %eax, %cr0
data32
# ljmp _codeseg, $2f
.byte 0xea
.long 3f
2: .word 0
3:
/* setup: %ds, %es, %ss */
movl %cs, %ax
movl %ax, %ds
movl %ax, %ss
movl %ax, %es
movl %ax, %fs
movl %ax, %gs
#ifndef NO_IDTR
/* load idtr so we can debug */
addr32
data32
lidt _Idtr_real
#endif
sti
data32
ret
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