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start.S
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start.S
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/*
mini - a Free Software replacement for the Nintendo/BroadOn IOS.
system startup
Copyright (C) 2008, 2009 Hector Martin "marcan" <marcan@marcansoft.com>
# This code is licensed to you under the terms of the GNU GPL, version 2;
# see file COPYING or http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt
*/
.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