I know that with a simple kernel this small I don't actually need to boot it with GRUB but I am trying to learn how to do this before my kernel gets big and I need to boot it. I have written a simple kernel with assembly using the real mode assembly tutorials over at OSDev.org. I tried to boot it but GRUB gave me the error that it couldn't find the multi-boot header. I took a look at the assembly code for the C Bare Bones tutorial. Do I just have to put everything in the section .multiboot? Can you please show me how I would boot this code. (This code is not of my creation, I have left my code on my home machine and am at school right now, I just borrowed this code from OSDev so please don't give me any mean comments saying that I stole someone's code. )
; boot.asm
mov ax, 0x07c0
mov ds, ax
mov si, msg
ch_loop:lodsb
or al, al ; zero=end or str
jz hang ; get out
mov ah, 0x0E
int 0x10
jmp ch_loop
hang:
jmp hang
msg db 'Welcome to Macintosh', 13, 10, 0
times 510-($-$$) db 0
db 0x55
db 0xAA
Can I boot and print using the BIOS or do I have o use a stack?
;====================================
[ORG 0x7c00] ; add to offsets
xor ax, ax ; make it zero
mov ds, ax ; DS=0
mov ss, ax ; stack starts at 0
mov sp, 0x9c00 ; 200h past code start
mov ax, 0xb800 ; text video memory
mov es, ax
mov si, msg ; show text string
call sprint
mov ax, 0xb800 ; look at video mem
mov gs, ax
mov bx, 0x0000 ; 'W'=57 attrib=0F
mov ax, [gs:bx]
mov word [reg16], ax ;look at register
call printreg16
hang:
jmp hang
----------------------
dochar: call cprint ; print one character
sprint: lodsb ; string char to AL
cmp al, 0
jne dochar ; else, we're done
add byte [ypos], 1 ;down one row
mov byte [xpos], 0 ;back to left
ret
cprint: mov ah, 0x0F ; attrib = white on black
mov cx, ax ; save char/attribute
movzx ax, byte [ypos]
mov dx, 160 ; 2 bytes (char/attrib)
mul dx ; for 80 columns
movzx bx, byte [xpos]
shl bx, 1 ; times 2 to skip attrib
mov di, 0 ; start of video memory
add di, ax ; add y offset
add di, bx ; add x offset
mov ax, cx ; restore char/attribute
stosw ; write char/attribute
add byte [xpos], 1 ; advance to right
ret
;------------------------------------
printreg16:
mov di, outstr16
mov ax, [reg16]
mov si, hexstr
mov cx, 4 ;four places
hexloop:
rol ax, 4 ;leftmost will
mov bx, ax ; become
and bx, 0x0f ; rightmost
mov bl, [si + bx];index into hexstr
mov [di], bl
inc di
dec cx
jnz hexloop
mov si, outstr16
call sprint
ret
;------------------------------------
xpos db 0
ypos db 0
hexstr db '0123456789ABCDEF'
outstr16 db '0000', 0 ;register value string
reg16 dw 0 ; pass values to printreg16
msg db "What are you doing, Dave?", 0
times 510-($-$$) db 0
db 0x55
db 0xAA
;==================================
Thank you in advance.
