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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 are through,
; the following work has been accomplished (chronologically):
;
; * BOOT_DRIVE is set
;
; * 50 sectors of our kernel are loaded at KERNEL_OFFSET from floppy
;
; * memoru map is available at MEMMAP_OFFSET
; (look at MEMMEP_SIZE_OFFSET for number of entries)
;
; * the vesa mode specified by VESA_MODE_SELECT is set up
; (at VESA_MODES, and VESA_MODE_INFO additional info structs are available)
;
; * 32-bit protected mode was set up.
;
; * A20 gate is open
;
; * PICs are configured
;
; * we are inside the C kernel!
;
;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;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 and some
;other memory locations
KERNEL_OFFSET equ 0x1000
MEMMAP_SIZE_OFFSET equ 0x7c00+0x600
MEMMAP_OFFSET equ 0x7c00+0x400
VESA_MODES equ 0x8300
VESA_MODE_INFO equ 0x8400
VESA_MODE_SELECT equ 0x4114
;we want 16-bit instructions, before we switch to 32-bit protected mode.
[bits 16]
jmp boot_16 ;start boot process
;SOME Global Data, mainly strings
BOOT_DRIVE:
db 0xff
STR_VERSION:
db "v0.2~",0
VESA_CHECK:
db "vesa check.",0
;lets put our temporary GDT (Global Descriptor Table) here
%include "boot/GDT.asm"
;include 16-bit real mode routines (print_string, disk_load)
%include "boot/disk_load_16.asm"
%include "boot/print_string_16.asm"
;include our routines for switching to 32-bit protected mode
%include "boot/pm.asm"
;pic mapping
%include "boot/pic.asm"
;get memory map
%include "boot/memmap.asm"
;;;;;;;; BOOT 16-bit real ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;lets start
[bits 16]
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
;Load the KERNEL (50 sectors starting at sector 2)
mov bx,KERNEL_OFFSET
mov dh, 50 ;50 sectors!
mov dl, [BOOT_DRIVE]
call disk_load
;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
;VESA: also setup vesa stuff before entering 32 bit protected mode
;VESA: get all available vesa modes!
mov ax,0 ; set target address in es:di (0:offset)
mov es,ax
mov di,VESA_MODES
mov ax,0x4f00 ;vesa function: Get Controller Info
int 0x10 ; call the interrupt to get the data from the bios!
vesa_err:
mov bx, VESA_CHECK
call print_string
cmp ax,0x004f
je vesa_ok
jmp vesa_err
vesa_ok:
;
;VESA: get vesa info on mode of interest
mov ax,0 ; set target address in es:di (0:offset)
mov es,ax
mov di,VESA_MODE_INFO
mov ax,0x4f01 ;vesa function: Get Mode Info
mov cx,VESA_MODE_SELECT
int 0x10 ; call the interrupt to get the data from the bios!
vesa_err2:
mov bx, VESA_CHECK
call print_string
cmp ax,0x004f
je vesa_ok2
jmp vesa_err2
vesa_ok2:
;VESA: finally switch to the mode of choice!
mov ax,0x4f02 ;vesa function: Set Mode
mov bx,VESA_MODE_SELECT
int 0x10
;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!!!!!! TODO
;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!
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;so we get identified as MBR
times 510-($-$$) db 0
dw 0xaa55
|
