source: mainline/arch/ia32/src/boot/boot.S@ b9e97fb

#
# 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