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1 jermar 1
#
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# Copyright (C) 2001-2004 Jakub Jermar
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions
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# are met:
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#
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# - Redistributions of source code must retain the above copyright
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#   notice, this list of conditions and the following disclaimer.
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# - Redistributions in binary form must reproduce the above copyright
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#   notice, this list of conditions and the following disclaimer in the
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#   documentation and/or other materials provided with the distribution.
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# - The name of the author may not be used to endorse or promote products
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#   derived from this software without specific prior written permission.
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#
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# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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# IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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# NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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# THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#
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.section K_TEXT_START
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.global kernel_image_start
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.code16
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#
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# This is where we require any SPARTAN-kernel-compatible boot loader
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# to pass control in real mode.
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#
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# Protected mode tables are statically initialised during compile
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# time. So we can just load the respective table registers and
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# switch to protected mode.
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#
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kernel_image_start:
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	cli
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	xorw %ax,%ax
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	movw %ax,%ds
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	movw %ax,%ss			# initialize stack segment register
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	movl $0x7c00,%esp		# initialize stack pointer
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	call memmap_arch_init
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	lgdt gdtr			# initialize Global Descriptor Table register
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	lidt idtr			# initialize Interrupt Descriptor Table register
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	movl %cr0,%eax
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	orl $0x1,%eax
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	movl %eax,%cr0			# switch to protected mode
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	jmpl $8,$meeting_point
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meeting_point:
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.code32
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	movw $16,%ax
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	movw %ax,%es
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	movw %ax,%gs
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	movw %ax,%fs
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	movw %ax,%ds			# kernel data + stack
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	movw %ax,%ss
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	call map_kernel			# map kernel and turn paging on
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	call main_bsp			# never returns
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	cli
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	hlt
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.global map_kernel
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map_kernel:
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	#
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	# Here we setup mapping for both the unmapped and mapped sections of the kernel.
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	# For simplicity, we set only one 4M page for 0x00000000 and one for 0x80000000.
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	#
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	movl %cr4, %ecx
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	orl $(1<<4), %ecx
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	movl %ecx, %cr4				# turn PSE on
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	movl $((1<<7)|(1<<0)), %eax
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	movl %eax, page_directory		# mapping 0x00000000 => 0x00000000
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	movl $(page_directory+(4096/2)), %edx
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	movl %eax, (%edx)			# mapping 0x80000000 => 0x00000000
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	leal page_directory, %eax
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	movl %eax, %cr3
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	# turn paging on
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	movl %cr0, %ebx
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	orl $(1<<31), %ebx
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	movl %ebx, %cr0
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	ret
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.section K_DATA_START
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.align 4096
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page_directory:
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	.space 4096, 0