/*-----------------------------------------------------------------

 Copyright (C) 2005  Michael "Chishm" Chisholm

 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; either version 2
 of the License, or (at your option) any later version.

 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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

 If you use this code, please give due credit and email me about your
 project at chishm@hotmail.com
------------------------------------------------------------------*/

@---------------------------------------------------------------------------------
	.section ".init"
	.global _start
	.global argStart
	.global argSize
@---------------------------------------------------------------------------------
	.align	4
	.arm
@---------------------------------------------------------------------------------
_start:
@---------------------------------------------------------------------------------
	b	startUp

@ Used for passing arguments to the loaded app
argStart:
	.word	_end - _start
argSize:
	.word	0x00000000

startUp:
	mov	r0, #0x04000000
	mov	r1, #0
	str	r1, [r0,#0x208]		@ REG_IME
	str	r1, [r0,#0x210]		@ REG_IE
	str	r1, [r0,#0x218]		@ REG_AUXIE

	ldr	r0, =0x02FFFDFB
	mov	r1, #42
	strb	r1, [r0]

	mov	r0, #0x12		@ Switch to IRQ Mode
	msr	cpsr, r0
	ldr	sp, =__sp_irq		@ Set IRQ stack

	mov	r0, #0x13		@ Switch to SVC Mode
	msr	cpsr, r0
	ldr	sp, =__sp_svc		@ Set SVC stack

	mov	r0, #0x1F		@ Switch to System Mode
	msr	cpsr, r0
	ldr	sp, =__sp_usr		@ Set user stack

	ldr	r0, =__bss_start	@ Clear BSS section to 0x00
	ldr	r1, =__bss_end
	sub	r1, r1, r0
	bl	ClearMem

	mov	r0, #0			@ int argc
	mov	r1, #0			@ char *argv[]
	ldr	r3, =main
	bl	_blx_r3_stub		@ jump to user code
	1:	b 1b

@---------------------------------------------------------------------------------
_blx_r3_stub:
@---------------------------------------------------------------------------------
	bx	r3

@---------------------------------------------------------------------------------
@ Clear memory to 0x00 if length != 0
@  r0 = Start Address
@  r1 = Length
@---------------------------------------------------------------------------------
ClearMem:
@---------------------------------------------------------------------------------
	mov	r2, #3			@ Round down to nearest word boundary
	add	r1, r1, r2		@ Shouldn't be needed
	bics	r1, r1, r2		@ Clear 2 LSB (and set Z)
	bxeq	lr			@ Quit if copy size is 0

	mov	r2, #0
ClrLoop:
	stmia	r0!, {r2}
	subs	r1, r1, #4
	bne	ClrLoop
	bx	lr

@---------------------------------------------------------------------------------
@ Copy memory if length	!= 0
@  r1 = Source Address
@  r2 = Dest Address
@  r4 = Dest Address + Length
@---------------------------------------------------------------------------------
CopyMemCheck:
@---------------------------------------------------------------------------------
	sub	r3, r4, r2		@ Is there any data to copy?
@---------------------------------------------------------------------------------
@ Copy memory
@  r1 = Source Address
@  r2 = Dest Address
@  r3 = Length
@---------------------------------------------------------------------------------
CopyMem:
@---------------------------------------------------------------------------------
	mov	r0, #3			@ These commands are used in cases where
	add	r3, r3, r0		@ the length is not a multiple of 4,
	bics	r3, r3, r0		@ even though it should be.
	bxeq	lr			@ Length is zero, so exit
CIDLoop:
	ldmia	r1!, {r0}
	stmia	r2!, {r0}
	subs	r3, r3, #4
	bne	CIDLoop
	bx	lr

@---------------------------------------------------------------------------------
	.align
	.pool
	.end
@---------------------------------------------------------------------------------