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|
;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;
;
; FoolOS Boot Loader for 16bit entry in C
;
; 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 16bit BOOTLOADER, after we finished we
; are inside 16bit C code!
;
;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;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 "C binary"
BOOT_OFFSET equ 0x1000
[bits 16]
jmp boot_16 ;start boot process
BOOT_DRIVE:
db 0xff
;SOME Global Data, mainly strings
STR_VERSION:
db "~ Fool Loader 16-bit, v0.1 ~",0
;include 16-bit real mode routines (print_string, print_hex, disk_load)
%include "boot/common.asm"
%include "boot/print16.asm"
;;;;;;;; BOOT 16-bit real ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;lets start
boot_16:
;print version info
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 BOOT LOADER from second sector (max 50 sectors)
mov bx,BOOT_OFFSET ;destination in ram
mov dh, 50 ;50 sectors
mov dl, [BOOT_DRIVE] ;source drive
call disk_load
call BOOT_OFFSET ;jump into our C code
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;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:
|
