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|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;
; THE FOOL-BOOT-LOADER
;
; * X sectors of our kernel loaded at KERNEL_OFFSET from floppy
;
; * memory map made available at MEMMAP_OFFSET
; (check at MEMMEP_SIZE_OFFSET for number of entries)
;
; * the VESA mode specified by VESA_MODE_SELECT will be set up
; (check at VESA_MODES, and VESA_MODE_INFO
; for additional information)
;
; * interrupts disabled
;
; * 32-bit protected mode set up.
;
; * esp set under MBR
;
; * A20 gate opened
;
; * and finally we will jump into the C world to kernel_main() !
;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;we want 16-bit instructions, before we switch to 32-bit protected mode.
[bits 16]
;define origin of boot record in memory: 0x7c00 was bootloader0
;this is where the BIOS per definition will put the first
;512 bytes of data from the boot device
;wer are one sector after that.
[org 0x7e00]
;;define some constants
;;where we will load our kernel into memory and some
;;other memory locations
;
MEMMAP_SIZE_OFFSET equ 0x7c00
MEMMAP_OFFSET equ 0x7c01
VESA_MODES equ 0x8300
VESA_MODE_INFO equ 0x8400
VESA_MODE_SELECT equ 0x4114
;
jmp boot_16 ;start boot process
;;SOME Global Data, mainly info/error strings
BOOT_DRIVE:
db 0xff
KERNEL_CHUNK:
dw 0x1
STR_VERSION:
db "Fool Loader Stage 2 v0.5",0
STR_LOAD:
db "Loading Kernel...",0
STR_BOOT:
db "Boot Drive: ",0
MEMMAP_INFO:
db "Getting Memory Map from BIOS.",0
STR_PM:
db "PROTECTED MODE",0
;
;;lets put our temporary GDT (Global Descriptor Table) here
;;kernel should move this away
%include "boot/GDT.asm"
;
;;include 16-bit real mode routines (print_string, disk_load, vesa_setup,check_a20)
%include "boot/disk_load_16.asm"
;%include "boot/check_a20_16.asm"
%include "boot/print_string_16.asm"
%include "boot/vesa_setup_16.asm"
;
;;include our routines for switching to 32-bit protected mode
%include "boot/pm.asm"
;include some pm mode helpers
%include "boot/common_pm.asm"
;
;
;
;;get memory map routine
%include "boot/memmap.asm"
;
;;;;;;;;; BOOT 16-bit real ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;
;;lets start
[bits 16]
idt_real:
dw 0x3ff ; 256 entries, 4b each = 1K
dd 0 ; Real Mode IVT @ 0x0000
boot_16:
mov [BOOT_DRIVE],dl
;pr info
mov bx, STR_VERSION
call print_string
call print_nextline
;show bootdrive
mov bx, STR_BOOT
call print_string
mov al,dl
call print_hex_byte
call print_nextline
; memmap message
mov bx,MEMMAP_INFO
call print_string
call print_nextline
;get memory map from bios before we enter 32 bit protected mode
mov ax,0 ; set target address in es:di (0:offset)
mov es,ax
mov di,MEMMAP_OFFSET
call BiosGetMemoryMap ; this will also put the number of entries
; of the memory map at MEMMAP_SIZE_OFFSET
kernel_load:
; Load the KERNEL Image
mov bx, STR_LOAD
call print_string
call print_nextline
call disk_load_16
call switch_to_pm
;
;;;;;;;;; BOOT 32-bit protected mode;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
[bits 32]
boot_32_pm:
;Fast A20 Gate:
;http://wiki.osdev.org/A20_Line
in al, 0x92
or al, 2
out 0x92, al
; tell the world we are protected
mov ebx,STR_PM
mov ecx,2*23*80
call print_string_pm
push edx ; persist edx for some reason!?
mov edx,0
mov dx,[KERNEL_CHUNK]
mov ecx,2*24*80
call print_hex_pm
; here we should move the chunk away or stop the loop if everything loaded.
mov ax,[KERNEL_CHUNK]
add ax,1
mov [KERNEL_CHUNK],ax
; here we should copy the chunk into ext mem!
; and now go back to real! (first 16bit protected!)
cmp edx,0x20
je finish_load
pop edx
jmp CODE16_SEG:reinit_16
finish_load:
;
call VesaSetup
; call kernel!
mov eax,0 ;tell the kernel
; we are the booting processor
call 0x18000 ;jump into our Kernel!
[bits 16]
reinit_16: ;16 bit protected mode
mov eax,DATA16_SEG
mov ds,eax
mov es,eax
mov fs,eax
mov gs,eax
mov ss,eax
mov eax,cr0
and eax,!0x1 ; Disable protected mode
mov cr0, eax
jmp 0:realmode
realmode:
mov sp,0x07bff
mov bp,sp
mov ax,0
mov ds,ax
mov es,ax
mov fs,ax
mov gs,ax
mov ss,ax
lidt [idt_real]
sti
jmp kernel_load
|
