##=============================================================================####      romboot.S####      x86 romboot####=============================================================================#####ECOSGPLCOPYRIGHTBEGIN###### -------------------------------------------## This file is part of eCos, the Embedded Configurable Operating System.## Copyright (C) 1998, 1999, 2000, 2001, 2002 Red Hat, Inc.#### eCos is free software; you can redistribute it and/or modify it under## the terms of the GNU General Public License as published by the Free## Software Foundation; either version 2 or (at your option) any later version.#### eCos is distributed in the hope that it will be useful, but WITHOUT ANY## WARRANTY; without even the implied warranty of MERCHANTABILITY or## FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License## for more details.#### You should have received a copy of the GNU General Public License along## with eCos; if not, write to the Free Software Foundation, Inc.,## 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.#### As a special exception, if other files instantiate templates or use macros## or inline functions from this file, or you compile this file and link it## with other works to produce a work based on this file, this file does not## by itself cause the resulting work to be covered by the GNU General Public## License. However the source code for this file must still be made available## in accordance with section (3) of the GNU General Public License.#### This exception does not invalidate any other reasons why a work based on## this file might be covered by the GNU General Public License.#### Alternative licenses for eCos may be arranged by contacting Red Hat, Inc.## at http://sources.redhat.com/ecos/ecos-license/## -------------------------------------------#####ECOSGPLCOPYRIGHTEND######=============================================================================#######DESCRIPTIONBEGIN######## Author(s):   jskov## Contributors:jskov## Date:        1999-01-07## Purpose:     x86 romboot## Description: When booting from ROM we need to run a short sequence of real##		mode code before jumping into 32 bit protected mode. There are##              problems in GAS with mixing all this code together, and it is##              easier to just move this bit of code out to a separate file.##              ########DESCRIPTIONEND########=============================================================================#include <pkgconf/system.h>#include <pkgconf/hal.h>#include <cyg/hal/arch.inc>#==============================================================================//    .file   "romboot.S"#------------------------------------------------------------------------------	.code16romboot_start:				/* Disable interrupt handling. */	cli	# Set DS == CS	movw	%cs,%ax	movw	%ax,%ds	# set ES == 0	movw	$0,%ax	movw	%ax,%es	# Call video bios to init display  	movw	$0xc000,%bx	movw  	%bx,%ds  	movw  	0x0000,%ax  	movw  	$0x0000,%bx  	movw  	%bx,%ds	cmpw  	$0xAA55,%ax  	jne  	1f	.byte	0x9a		# lcall	.word	0x0003		# offset	.word   0xc000		# segment1:		movw	%cs,%ax	movw	%ax,%ds	# set ES == 0	movw	$0,%ax	movw	%ax,%es	# build a GDT descriptor in memory at location zero	movw	$(gdtEnd - gdtStart),%ax	movw	%ax,%es:0	lea	gdtStart,%ax	addw	$0xFF00,%ax	movw	%ax,%es:2	movw	$0x000F,%ax	movw	%ax,%es:4		# load GDTR	lgdt	%es:0	# Switch to protected mode.	movl	%cr0,%eax	orb	$1, %al	movl	%eax,%cr0	# and do a jump to flush instruction prefetch	jmp	romboot_pm	hlt	.align	4, 0xCCgdtStart:	/* Selector 0x00 == invalid. */	.word	0x0000	.word	0x0000	.byte	0x00	.byte	0x00	.byte	0x00	.byte	0x00	/* Selector 0x08 == code. */	.word	0xFFFF	.word	0x0000	.byte	0x00	.byte	0x9B	.byte	0xCF	.byte	0x00	/* Selector 0x10 == data. */	.word	0xFFFF	.word	0x0000	.byte	0x00	.byte	0x93	.byte	0xCF	.byte	0x00	/* Selector 0x18 == shorter code: faults any code          * access 0xF0000000-0xFFFFFFFF.         */	.word	0xFFFF	.word	0x0000	.byte	0x00	.byte	0x9B	.byte	0xC7	.byte	0x00	/* Selector 0x20 == data; faults any access 0xF0000000-0xFFFFFFFF. */	.word	0xFFFF	.word	0x0000	.byte	0x00	.byte	0x93	.byte	0xC7	.byte	0x00	.align	4, 0xCCgdtEnd:	# We arrive here in protected moderomboot_pm:		# Load data selectors	movw	$0x10, %ax	movw	%ax, %ds	movw	%ax, %es	movw	%ax, %fs	movw	%ax, %gs		# jump to start of ROM, where the PM code starts	#	ljmp	$8,$0xF0000	.byte	0x66,0xea	# opsize + ljmp opcode	.long	0x000F0000	# destination address	.word	0x0008		# code selector	.code16	.org	0xF0romboot_reset:			jmp	romboot_start	.org	0x100	#------------------------------------------------------------------------------# end of romboot.S