not_my_default_bootloader/boot.asm

[org 0x7c00]

[bits 16]

pre:
cmp ah, 0x0F
je welcome
mov [bootdev], dl		; Save boot device number
jmp welcome

welcome:
    xor ax,ax      ; We want a segment of 0 for DS for this question
    mov ds,ax      ;     Set AX to appropriate segment value for your situation
    mov es,ax      ; In this case we'll default to ES=DS
    mov bx,0x8000  ; Stack segment can be any usable memory
    mov ss,bx      ; This places it with the top of the stack @ 0x80000.
    mov sp,ax      ; Set SP=0 so the bottom of stack will be @ 0x8FFFF
    cld            ; Set the direction flag to be positive direction



        mov ah, 01h     ;make cursor invisible
        mov cx, 2607h
        int 10h

    mov ah, 06h    ; Scroll up function
    xor al, al     ; Clear entire screen
    xor cx, cx     ; Upper left corner CH=row, CL=column
    mov dx, 184FH  ; lower right corner DH=row, DL=column
    mov bh, 1Eh    ; YellowOnBlue
    int 10H         ; execute interrupt

        mov ah, 02h     ;sets cursor to top to write
        mov bh, 0h
        mov dh, 2h
        mov dl, 2h
        int 10h

    mov si, wolf_wel_msg
    call wolf_print

    mov si, xpub
    call wolf_print

start:
	mov ah, 0x00
        int 0x16
        cmp al, "0"
        je load_it_all_0
        cmp al, "1"
	je load_it_all_1
	jmp over

load_it_all_0:

    mov si, wolf_kernel_load
    call wolf_print

    pushf
    stc

    mov ah,00
    int 13h

.read_sector:
        mov ax, 0x0
        mov es, ax      ; ES = 0
        mov bx, 0x2000  ; BX = 0x1000. ES:BX=0x0:0x1000
                        ; ES:BX = starting address to read sector(s) into
        mov ah, 02      ; Int 13h/AH=2 = Read Sectors From Drive
        mov al, 01      ; Sectors to read = 1
        mov ch, 00      ; CH=Cylinder. Second sector of disk
                        ; is at Cylinder 0 not 1
        mov cl, 03      ; Sector to read = 2
        mov dh, 00      ; Head to read = 0
                        ; DL hasn't been destroyed by our bootloader code and still
                        ;     contains boot drive # passed to our bootloader by the BIOS
	mov dl, [bootdev]
        int 13h

    jc wolf_error
    popf
    jmp 0x0:0x2000
    cli
    hlt


load_it_all_1:

    mov si, wolf_kernel_load
    call wolf_print

    pushf
    stc

    mov ah,00
    int 13h

.read_sector:
        mov ax, 0x0
        mov es, ax      ; ES = 0
        mov bx, 0x1000  ; BX = 0x1000. ES:BX=0x0:0x1000
                        ; ES:BX = starting address to read sector(s) into
        mov ah, 02      ; Int 13h/AH=2 = Read Sectors From Drive
        mov al, 01      ; Sectors to read = 1
        mov ch, 00      ; CH=Cylinder. Second sector of disk
                        ; is at Cylinder 0 not 1
        mov cl, 02      ; Sector to read = 2
        mov dh, 00      ; Head to read = 0
                        ; DL hasn't been destroyed by our bootloader code and still
                        ;     contains boot drive # passed to our bootloader by the BIOS
	mov dl, [bootdev]
	int 13h

    jc wolf_error
    popf
    jmp 0x0:0x1000
    cli
    hlt


wolf_error:
        mov si, wolf_error_msg
        call wolf_print
        mov si, wolf_error_msg1
        call wolf_print
        mov ah,00
        int 16h
        xor ax,ax
        int 19h

wolf_print:
        lodsb
        or al,al
        jz exit
	mov ah,0x0e
        int 10h
        jmp wolf_print
        exit:
        ret



over:
        jmp start

; Moved the data before the boot signature but after the code
wolf_wel_msg db 'Welcome to this publication..., press a key',0x0D,0x0A,0
wolf_kernel_load db 'Loading program',0x0D,0x0A,0
wolf_error_msg db 'Program not found!',0x0D,0x0A,0
wolf_error_msg1 db 'Press any key to restart..',0
xpub db 0x0D, 0x0A, 0x20, 0xB1, 0x20, 0x20, 0x20, 0xB1, 0x20, 0xB1, 0xB1, 0xB1, 0x20, 0x20, 0xB1, 0x20, 0x20, 0x20, 0xB1,0x20,0xB1,0xB1,0xB1, 0x20, 0x0D, 0x0A,0x20,0x20,0xB1,0x20,0xB1,0x20,0x20,0xB1,0x20,0x20,0xB1, 0x20,0xB1,0x20,0x20,0x20,0xB1,0x20,0xB1,0x20,0x20, 0xB1, 0x0D,0x0A,0x20,0x20,0x20,0xB1, 0x20,0x20,0x20,0xB1,0xB1, 0xB1,0x20,0x20,0xB1,0x20,0x20,0x20,0xB1,0x20,0xB1,0xB1,0xB1,0x20,0x0D,0x0A,0x20,0x20,0xB1,0x20,0xB1, 0x20,0x20,0xB1,0x20,0x20,0x20,0x20,0xB1,0x20,0x20,0x20,0xB1,0x20,0xB1,0x20,0x20,0xB1,0x0D,0x0A,0x20,0xB1, 0x20,0x20,0x20,0xB1,0x20,0xB1,0x20,0x20,0x20,0x20,0x20,0xB1,0xB1,0xB1,0x20,0x20,0xB1,0xB1,0xB1, 0x20, 0


bootdev		db 0x80 	; Boot device number

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