aurora-os/bootloader-simple.asm at master · QuirkyCodex/aurora-os · GitHub

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; Aurora OS Bootloader - Simple version
; Loads kernel and jumps to it in real mode

org 0x7C00
bits 16

start:
    jmp main

main:
    ; Setup
    cli
    xor ax, ax
    mov ds, ax
    mov es, ax
    mov ss, ax
    mov sp, 0x7C00
    sti

    mov [boot_drive], dl

    ; Clear screen
    mov ax, 0x0003
    int 0x10
    mov ax, 0x0600
    mov bh, 0x1F
    xor cx, cx
    mov dx, 0x184F
    int 0x10

    ; Loading message
    mov si, loading_msg
    call print_str

    ; Try to load kernel
    mov bx, 0x1000
    mov ah, 0x02
    mov al, 4
    mov ch, 0
    mov cl, 2
    mov dh, 0
    mov dl, [boot_drive]
    int 0x13
    jc disk_error

    ; Success message
    mov si, success_msg
    call print_str

    ; Simple delay
    mov cx, 0xFFFF
.delay:
    dec cx
    jnz .delay

    ; Jump to kernel directly in real mode
    jmp 0x1000

disk_error:
    mov si, error_msg
    call print_str
    call wait_key
    int 0x19

print_str:
    lodsb
    test al, al
    jz .done
    mov ah, 0x0E
    int 0x10
    jmp print_str
.done:
    ret

wait_key:
    mov ah, 0
    int 0x16
    ret

loading_msg: db "Loading Aurora...", 0x0D, 0x0A, 0
success_msg: db "Starting kernel...", 0x0D, 0x0A, 0
error_msg: db "Disk error!", 0x0D, 0x0A, 0

boot_drive: db 0

times 510 - ($ - $$) db 0
dw 0xAA55