mini/start.S

/*
	mini - a Free Software replacement for the Nintendo/BroadOn IOS.

	system startup

Copyright (C) 2008, 2009	Hector Martin "marcan" <marcan@marcansoft.com>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, version 2.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

*/
.arm

.extern _main
.extern __got_start
.extern __got_end
.extern __bss_start
.extern __bss_end
.extern __bss2_start
.extern __bss2_end
.extern __stack_addr
.globl _start
.globl debug_output

.extern v_undf
.extern v_swi
.extern v_instr_abrt
.extern v_data_abrt
.extern v_reserved
.extern v_irq
.extern v_fiq

.section .init

_vectors:
_start:
	ldr	pc, =v_reset
	ldr	pc, =v_undf
	ldr	pc, =v_swi
	ldr	pc, =v_instr_abrt
	ldr	pc, =v_data_abrt
	ldr	pc, =v_reserved
	ldr	pc, =v_irq
	ldr	pc, =v_fiq

.pool

v_reset:
	@ Switch to System mode
	msr cpsr_c, #0xdf

	@ Get loader base from ELF loader
	mov	r4, r0

	@ Output 0x42 to the debug port
	mov	r0, #0x42
	bl	debug_output

	@ Set up a stack
	ldr	sp, =__stack_addr

	@ clear the stack to a marker value
	ldr	r1, =__stack_end
	ldr	r2, =__stack_addr
	ldr	r3, =0xDEADBEEF
stk_loop:
	@ check for the end
	cmp	r1, r2
	beq	done_stk
	@ clear the word and move on
	str	r3, [r1]
	add	r1, r1, #4
	b	stk_loop

done_stk:
	@ clear BSS
	ldr	r1, =__bss_start
	ldr	r2, =__bss_end
	mov	r3, #0
bss_loop:
	@ check for the end
	cmp	r1, r2
	beq	done_bss
	@ clear the word and move on
	str	r3, [r1]
	add	r1, r1, #4
	b	bss_loop

done_bss:
	@ clear BSS2
	ldr	r1, =__bss2_start
	ldr	r2, =__bss2_end
	mov	r3, #0
bss2_loop:
	@ check for the end
	cmp	r1, r2
	beq	done_bss2
	@ clear the word and move on
	str	r3, [r1]
	add	r1, r1, #4
	b	bss2_loop

done_bss2:
	mov	r0, #0x84
	bl	debug_output
	@ take the plunge
	mov	r0, r4
	bl	_main
	@ _main returned! Go to whatever address it returned...
	mov	pc, r0

.pool

debug_output:
	@ load address of port
	mov	r3, #0xd800000
	@ load old value
	ldr	r2, [r3, #0xe0]
	@ clear debug byte
	bic	r2, r2, #0xFF0000
	@ insert new value
	and	r0, r0, #0xFF
	orr	r2, r2, r0, LSL #16
	@ store back
	str	r2, [r3, #0xe0]
	bx	lr

.pool