;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;
;   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 to 0x90000
;
;	* 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
;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 0x7e00]

;;define some constants
;;where we will load our kernel into memory and some 
;;other memory locations
;
KERNEL_DATA equ 10	;sector on disk where the kernel starts
KERNEL_SECTOR equ 0x1000
KERNEL_OFFSET equ 0x0000

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
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

;
;;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"
;
;
;;get memory map routine
%include "boot/memmap.asm"
;
;;;;;;;;; BOOT 16-bit real ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;
;;lets start
[bits 16]

boot_16:

    mov [BOOT_DRIVE],dl

;   pr info 
    mov bx, STR_VERSION
    call print_string
    call print_nextline

    mov bx, STR_BOOT
    call print_string
    mov al,dl
    call print_hex_byte
    call print_nextline

    ;show bootdrive

    ;   Load the KERNEL Image
    mov bx, STR_LOAD
    call print_string
    call print_nextline
    call disk_load_16
   
    ; 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

    call VesaSetup
   
    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

    ; call kernel!
    mov eax,0		;tell the kernel 
			; we are the booting processor
    call 0x10000        ;jump into our Kernel!