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;; boot.stage1.asm
[org 0x7c00]
[bits 16]
%include "boot.common.asm"
%define READ_SECTORS_NUM 1
%define BOOT_LOAD_ADDR 0x7c00
%define SECTOR_SIZE 512
global _start
_start:
;; Disable interrupts
cli
;; Setup segment registers
xor ax, ax
mov ds, ax
mov es, ax
mov ss, ax
;; Adjust Stack
mov sp, _start
clc
mov [drive], dl
mov si, disk_addr_packet
mov ah, 0x42 ; BIOS extended read function
mov dl, [drive] ; Drive number
int 0x13 ; BIOS disk services
jc _disk_read_err
mov si, disk_read_success_msg
call _print_string
jmp 0x0000:0x7e00
_disk_read_err:
mov si, disk_read_err_msg
call _print_string
hlt
jmp _disk_read_err
_print_string:
pusha
mov ah, 0x0e
mov bh, 0x00
.print_loop:
lodsb
test al, al
je .print_return
int 0x10
jmp .print_loop
.print_return:
popa
ret
_end:
hlt
jmp _end
drive: db 0
disk_read_err_msg: db "Failed to read disk", 13, 10, 0
disk_read_success_msg: db "Read the disk successfully", 13, 10, 0
disk_addr_packet:
db 0x10
db 0x00
dw READ_SECTORS_NUM
dw 0x7e00
dw 0x0000
dq 1
;; Padding and magic number
times 510 - ($ - $$) db 0
dw 0xaa55
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