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[ORG 0]
	
            jmp 07C0h:start     ; Goto segment 07C0
	
    start:
            ; Update the segment registers
            mov ax, cs
            mov ds, ax
            mov es, ax

    reset:                      ; Reset the floppy drive
            mov ax, 0           ;
            mov dl, 0           ; Drive=0 (=A)
            int 13h             ;
            jc reset            ; ERROR => reset again

    read:
            mov ax, 1000h       ; ES:BX = 1000:0000
            mov es, ax          ;
            mov bx, 0           ;

            mov ah, 2           ; Load disk data to ES:BX
			mov dl, 0           ; Drive=0
			mov dh, 0           ; Head=0
			mov ch, 0           ; Cylinder=0
			mov cl, 2           ; Sector=2
            mov al, 5           ; Load 5 sectors
            
            int 13h             ; Read!

            jc read             ; ERROR => Try again

	program:
            jmp 1000h:0000      ; Jump to the program

    times 510-($-$$) db 0
    dw 0AA55h

Code: Select all

global loader           
extern _kmain            ; kmain from kernel.c
 
section .text
align 4
 
	; reserve initial kernel stack space
	STACKSIZE equ 0x4000                  ; that's 16k.
		
	loader:
			mov esp, stack+STACKSIZE           ; set up the stack
			
			mov al, 'R'
            mov ah, 0Eh     ; Print AL
            mov bx, 7
            int 10h
			
			push eax                           ; pass Multiboot magic number
			push ebx                           ; pass Multiboot info structure
			call  _kmain                       ; call kernel proper
			   
			cli
	hang:
			hlt                                ; halt machine should kernel return
			jmp   hang
 
section .bss
align 4
stack:
resb STACKSIZE                     ; reserve 16k stack on a doubleword boundary

Code: Select all

void kmain( void* mbd, unsigned int magic )
{
   unsigned char *videoram = (unsigned char *) 0xb8000;
   videoram[0] = 65;
   videoram[1] = 0x07;
}