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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.
#

#include <arch/boot/boot.h>
#include <arch/boot/memmapasm.h>

.section K_TEXT_START
.global kernel_image_start

KTEXT=8
KDATA=16

.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 $BOOTSTRAP_OFFSET - 0x400, %esp    # initialize stack pointer
    
    call memmap_arch_init
    
    lgdt real_bootstrap_gdtr                # initialize Global Descriptor Table register
    
    movl %cr0, %eax
    orl $0x1, %eax
    movl %eax, %cr0                         # switch to protected mode
    
    jmpl $KTEXT, $boot_image_start
    
.code32
.align 4
multiboot_header:
    .long MULTIBOOT_HEADER_MAGIC
    .long MULTIBOOT_HEADER_FLAGS
    .long -(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS)    # checksum
    .long multiboot_header + BOOT_OFFSET
    .long unmapped_ktext_start + BOOT_OFFSET
    .long 0
    .long 0
    .long multiboot_image_start + BOOT_OFFSET
    
boot_image_start:
    movw $KDATA, %ax
    movw %ax, %es
    movw %ax, %gs
    movw %ax, %fs
    movw %ax, %ds           # kernel data + stack
    movw %ax, %ss
    
    movb $0xd1, %al         # enable A20 using the keyboard controller
    outb %al, $0x64
    movb $0xdf, %al
    outb %al, $0x60
    
    movl $BOOTSTRAP_OFFSET, %esi
    movl $BOOTSTRAP_OFFSET + BOOT_OFFSET, %edi
    movl $_hardcoded_kernel_size, %ecx
    cld
    rep movsb
    
    call map_kernel         # map kernel and turn paging on
    
    call main_bsp           # never returns

    cli
    hlt
    
multiboot_image_start:
    movl $BOOTSTRAP_OFFSET - 0x400, %esp            # initialize stack pointer
    
    lgdt protected_bootstrap_gdtr - 0x80000000      # initialize Global Descriptor Table register

    movw $KDATA, %cx
    movw %cx, %es
    movw %cx, %gs
    movw %cx, %fs
    movw %cx, %ds                                   # kernel data + stack
    movw %cx, %ss
    
    jmpl $KTEXT, $multiboot_meeting_point + BOOT_OFFSET
    multiboot_meeting_point:
    
    pushl %ebx                                      # save parameters from GRUB
    pushl %eax
    
    movl $BOOTSTRAP_OFFSET + BOOT_OFFSET, %esi
    movl $BOOTSTRAP_OFFSET, %edi
    movl $_hardcoded_unmapped_size, %ecx
    cld
    rep movsb
    
    call map_kernel                                 # map kernel and turn paging on
    
    popl %eax
    popl %ebx
    cmpl $MULTIBOOT_LOADER_MAGIC, %eax          # compare GRUB signature
    je valid_boot
        
        xorl %ecx, %ecx                         # no memory size or map available
        movl %ecx, e801memorysize
        movl %ecx, e820counter
        
        jmp invalid_boot
        
    valid_boot:
        
        movl (%ebx), %eax                       # ebx = physical address of struct multiboot_info
        
        bt $0, %eax                             # mbi->flags[0] (mem_lower, mem_upper valid)
        jc mem_valid
            
            xorl %ecx, %ecx
            jmp mem_invalid
            
        mem_valid:
        movl 4(%ebx), %ecx                      # mbi->mem_lower
        addl 8(%ebx), %ecx                      # mbi->mem_upper
        
        mem_invalid:
        movl %ecx, e801memorysize
        
        bt $6, %eax                             # mbi->flags[6] (mmap_length, mmap_addr valid)  
        jc mmap_valid
            
            xorl %edx, %edx
            jmp mmap_invalid
            
        mmap_valid:
        movl 44(%ebx), %ecx                     # mbi->mmap_length
        movl 48(%ebx), %esi                     # mbi->mmap_addr
        movl $e820table, %edi
        xorl %edx, %edx
        
        mmap_loop:
            cmpl $0, %ecx
            jle mmap_end
            
            movl 4(%esi), %eax                  # mmap->base_addr_low
            movl %eax, (%edi)
            
            movl 8(%esi), %eax                  # mmap->base_addr_high
            movl %eax, 4(%edi)
            
            movl 12(%esi), %eax                 # mmap->length_low
            movl %eax, 8(%edi)
            
            movl 16(%esi), %eax                 # mmap->length_high
            movl %eax, 12(%edi)
            
            movl 20(%esi), %eax                 # mmap->type
            movl %eax, 16(%edi)
            
            movl (%esi), %eax                   # mmap->size
            addl $0x4, %eax
            addl %eax, %esi
            subl %eax, %ecx
            addl $MEMMAP_E820_RECORD_SIZE, %edi
            incl %edx
            jmp mmap_loop
        
        mmap_end:
        
        mmap_invalid:
        movl %edx, e820counter
        
    invalid_boot:
    
    call main_bsp - BOOT_OFFSET                     # 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