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;; boot.stage1.asm
[bits 16]
global _start
%include "boot.stage1.print.asm"
%define READ_SECTORS_NUM 64
%define BOOT_LOAD_ADDR 0x7c00
%define STAGE2_ADDR 0x7e00
%define SECTOR_SIZE 512
section .boot_sector
_start:
;; Setup segment registers
xor ax, ax
mov ds, ax
mov es, ax
mov ss, ax
mov gs, ax
mov fs, ax
mov si, DAP
mov ah, 0x42 ; Extended read function
mov dl, 0x80 ; Drive Number (starts at 0x80, thus it is 1)
int 0x13
jc _disk_read_err
_ignore_disk_read_err:
mov si, _jmp_msg
call _print_string
jmp 0x0000:STAGE2_ADDR
_disk_read_err:
cmp word [DAP.num_sectors], READ_SECTORS_NUM
jle _ignore_disk_read_err
mov si, _disk_read_err_msg
call _print_string
.halt: hlt
jmp .halt
align 16
DAP:
db 0x10 ; Size of packet
db 0 ; Zero
.num_sectors:
dw READ_SECTORS_NUM ; Number of sectors to be read
dd (BOOT_LOAD_ADDR + SECTOR_SIZE) ; Destination address
dq 1 ; Which sector to start at
_disk_read_err_msg: db "Disk error", 13, 10, 0
_jmp_msg: db "Jumping to Stage 2", 13, 10, 0
;; Padding and magic number
times 510 - ($ - $$) db 0
dw 0xaa55
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