crt0.s

开发三星s3c44b0引导程序

@ r0 -> start of flash
@ r1 -> where to load data
@ r2 -> start of program

	.text
	.align
	.global main,_main

main:
_main:
	# light up some LEDs
	ldr r3, =0xff00c000
	ldr r4, =0x000000f0
	str r4, [r3]
	str r4, [r3, #0x34]
	str r4, [r3, #0x10]
	ldr r4, =0x10
	str r4, [r3, #0x30]
	bl delay
	ldr r4, =0x20
	str r4, [r3, #0x30]
	bl delay
	ldr r4, =0x40
	str r4, [r3, #0x30]
	bl delay
	ldr r4, =0x80
	str r4, [r3, #0x30]
	bl delay
	ldr r4, =0x10
	str r4, [r3, #0x34]
	bl delay
	ldr r4, =0x20
	str r4, [r3, #0x34]
	bl delay
	ldr r4, =0x40
	str r4, [r3, #0x34]
	bl delay
	ldr r4, =0x80
	str r4, [r3, #0x34]
	
	# copy .data section
	ldr r3, =_etext
	ldr r4, =_sdata
	ldr r5, =_edata
	subs r5, r5, r4
	bl copydata

	# clear .bss section
	ldr r4, =_sbss
	ldr r5, =_ebss
	subs r5, r5, r4
	bl clearbss
	
	# and jump to the kernel
	b boot

copydata:
	subs r5, r5, #4
	ldr r6, [r3], #4
	str r6, [r4], #4
	bne copydata
	mov pc, lr

clearbss:
	subs r5, r5, #4
	str r0, [r3], #4
	bne clearbss
	mov pc, lr

delay:
	ldr r10, =0x8000
redelay:
	subs r10, r10, #1
	bne redelay
	mov pc, lr