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|
;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;
;
; FoolOS Boot Loader
;
; Copyright 2014 M.Idziorek <m.i@gmx.at>
;
; we have just been loaded by the BIOS and are in 16-bits real mode!
;
; THIS IS THE CENTRAL FILE OF THE BOOTLOADER, after we finished we
; are inside the C kernel!
;
;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;we want 16-bit instructions, before we switch to 32-bit protected mode.
;define origin of boot record in memory: 0x7c00
;this is where the BIOS per definition will put the first
;512 bytes of data from the boot device
;The Boot record is identified by the last 2 magic bytes: 0xaa55 (?)
[org 0x7c00]
;define where we will load our kernel into memory
KERNEL_OFFSET equ 0x1000
[bits 16]
jmp boot_16 ;start boot process
BOOT_DRIVE:
db 0
;SOME Global Data, mainly strings
STR_VERSION:
db "v0.2~",0
;STR_PROT:
; db "32-bit PM",0
;STR_LOADED:
; db "loaded",0
;lets put our temporary GDT (Global Descriptor Table) here
%include "boot/GDT.asm"
;include 16-bit real mode routines (print_string, print_hex, disk_load)
%include "boot/common.asm"
;include 32-bit Protected Mode routines (print_string_pm,print_hex_pm)
;%include "boot/common_pm.asm"
;include our routines for switching to 32-bit protected mode
%include "boot/pm.asm"
;pic mapping
%include "boot/pic.asm"
;memory map
%include "boot/memmap.asm"
;;;;;;;; BOOT 16-bit real ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;lets start
[bits 16]
;print_string routine ([bx])
;this routine will print a null terminated string at [bx] to the screen.
print_string:
pusha ;push all registers
mov ah,0x0e
print_string_loop:
;check if value at [bx] is "\0" (end of string)
mov cl,[bx]
cmp cl,0
je print_string_finish
;otherwise instruct BIOS to print the current char
mov al,cl
int 0x10
;proceed with next char
inc bx
jmp print_string_loop
print_string_finish:
popa ;pop all registers
ret ;return to caller
boot_16:
mov bx, STR_VERSION
call print_string
;setup the stack
mov bp,0x8000
mov sp,bp
;remember BOOT_DRIVE (as was set by BIOS)
mov [BOOT_DRIVE],dl
;print FoolOS version info
; mov bx, STR_VERSION
; call print_string
;Load the KERNEL
mov bx,KERNEL_OFFSET
mov dh, 50
mov dl, [BOOT_DRIVE]
call disk_load
;print info message that kernel was loaded
; mov bx, STR_LOADED
; call print_string
;get memory map from biso before we enter 32 bit protected mode
; todo: how to set es!?!?
;mov es,0
mov di,MEMMAP
call BiosGetMemoryMap
;finally lets enter Protected mode!!!
call switch_to_pm
;;;;;;;; BOOT 32-bit protected mode;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
[bits 32]
boot_32_pm:
; we could do ALL This inside the kernel!!!
;print info message that we are in protected mode!
; mov ecx,160
; mov ebx,STR_PROT
; call print_string_pm
;enable A20
;http://www.brokenthorn.com/Resources/OSDev9.html
;Method 3.1: Enables A20 through keyboard controller
mov al, 0xdd ; command 0xdd: enable a20
out 0x64, al ; send command to controller
;pic setup
call pic_setup
call KERNEL_OFFSET ;jump into our Kernel it
db 'X'
db 'X'
MEMMAP:
;idt_descriptor:
; dw idt_end-idt_start-1
; dd KERNEL_OFFSET
;;;; DEBUGGING STUFF
;times 8 db '@'
;dw interrupt
;times 8 db '@'
;dw interrupt2
;times 8 db '@'
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;so we get identified as MBR
times 510-($-$$) db 0
dw 0xaa55
;interrupt descriptor table (hardcoded address of interrupts:)
;idt_start:
;times 33 db 0x50,0x7c,0x08,0x00,0x00,10001110b,0x0,0x0
;db 0x59,0x7c,0x08,0x00,0x00,10001110b,0x0,0x0
;times 253 db 0x50,0x7c,0x08,0x00,0x00,10001110b,0x0,0x0
;idt_end:
|
