/*	
	set to 16 bit mode (80x86 begin in real mode) text section to 0 
	original code at http://www.netspace.net.au/~gok/resources/

	Modified by Stellios Keskinidis
	            April 2001

	this is a boot loader that displays hello world at bootup and
	loops until the user presses 'q'

	Makefile
	----------------------------------------------------------
		install: bootsect
			dd if=./bootsect of=/dev/fd0 bs=512 count=1

		bootsect: boot.o
			objcopy -O binary boot.o bootsect

		boot.o: boot.s
			as -o boot.o boot.s 

		clean:
			rm bootsect boot.o
	----------------------------------------------------------
*/

.code16
.text
.org 0x00

.global _start
_start:
	mov $0x07C0,%ax		
	mov %ax,%ds		
	call booting
	xor %dx,%dx		/* test if dx == 0 */
	call working
	call idleloop
	ret

/* display booting message */
booting:
	mov $boot,%si
	call message
	ret

/* display message in %si */
message:
	cld			/* set direction to increment */
	lodsb
	or %al,%al
	jz done
	mov $0xE,%ah 
	mov $7,%bx
	int $0x10
	jmp message
	
done:
	ret

/* display hello world message */
working:
	mov $hellow,%si
	call message
	call waitenter
	jmp working
	ret

/*
    TODO: gracefully exit

    it just disables interrupts and halt the cpu,
    ctrl-alt-del won't even work, you'll have to
    hit the reset button
*/

exit:
	mov $bye,%si
	call message
	int $0x20
	cli
	hlt
	ret

/* get keypress from user, if a 'q' (113) then halt */

waitenter:
	movw $cont,%si 
	call message
	xor %ax,%ax	/* Sets AH=0 and AL=0 */
	int $0x16 	/* Wait for keypress */
	cmp $113,%al 
	je exit
	cmp $13,%al 
	mov %ax,%si
	call message
	jnz working
	ret

/* wait for an interrupt to occur */
idleloop:
	hlt
	jmp idleloop

/* all our messages that get displayed */
boot: 	
	.ascii "Loading           ....."
	.byte 10, 13, 10, 13, 0

hellow:
	.ascii "Hello World " 
	.byte 33, 10, 13, 0
cont: 
	.ascii "press 'q' to quit or any other key to continue"
	.byte 10, 13, 0
bye:
	.ascii "bye."
	.byte 10, 13, 0

/* Fill with zero until boottag */
padlen: 
	.byte boottag - .

.fill 10,1,0	
/*	times 510-($-$$) db 0 */

/* the boot loader */
.org 410
boottag:
	.word 0xAA55