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#
# Copyright (C) 2001-2004 Jakub Jermar
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# - Redistributions of source code must retain the above copyright
#   notice, this list of conditions and the following disclaimer.
# - Redistributions in binary form must reproduce the above copyright
#   notice, this list of conditions and the following disclaimer in the
#   documentation and/or other materials provided with the distribution.
# - The name of the author may not be used to endorse or promote products
#   derived from this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
# IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
# NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
# THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#

.section K_TEXT_START
.global kernel_image_start

.code16
#
# This is where we require any SPARTAN-kernel-compatible boot loader
# to pass control in real mode.
#
# Protected mode tables are statically initialised during compile
# time. So we can just load the respective table registers and
# switch to protected mode.
#
kernel_image_start:
    cli
    xorw %ax,%ax
    movw %ax,%ds
    movw %ax,%ss            # initialize stack segment register
    movl $0x7c00,%esp       # initialize stack pointer
    
    call memmap_arch_init
    
    lgdt gdtr           # initialize Global Descriptor Table register
    lidt idtr           # initialize Interrupt Descriptor Table register
    
    movl %cr0,%eax
    orl $0x1,%eax
    movl %eax,%cr0          # switch to protected mode
    jmpl $8,$meeting_point
meeting_point:
.code32

    movw $16,%ax
    movw %ax,%es
    movw %ax,%gs
    movw %ax,%fs
    movw %ax,%ds            # kernel data + stack
    movw %ax,%ss

    call map_kernel         # map kernel and turn paging on

    movl $_hardcoded_ktext_size, hardcoded_ktext_size
    movl $_hardcoded_kdata_size, hardcoded_kdata_size
    movl $_hardcoded_load_address, hardcoded_load_address

    call main_bsp           # never returns

    cli
    hlt

.global map_kernel
map_kernel:
    #
    # Here we setup mapping for both the unmapped and mapped sections of the kernel.
    # For simplicity, we set only one 4M page for 0x00000000 and one for 0x80000000.
    #
    movl %cr4, %ecx
    orl $(1<<4), %ecx
    movl %ecx, %cr4             # turn PSE on
    
    movl $((1<<7)|(1<<0)), %eax
    movl %eax, page_directory       # mapping 0x00000000 => 0x00000000

    movl $(page_directory+(4096/2)), %edx
    movl %eax, (%edx)           # mapping 0x80000000 => 0x00000000

    leal page_directory, %eax
    movl %eax, %cr3
    
    # turn paging on
    movl %cr0, %ebx
    orl $(1<<31), %ebx
    movl %ebx, %cr0
    ret


.section K_DATA_START

.align 4096
page_directory:
    .space 4096, 0