mini/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 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
*/
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.arm
.extern _main
.extern __got_start
.extern __got_end
.extern __bss_start
.extern __bss_end
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.extern __bss2_start
.extern __bss2_end
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.extern __stack_addr
.globl _start
.globl debug_output
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.extern v_undf
.extern v_swi
.extern v_instr_abrt
.extern v_data_abrt
.extern v_reserved
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.extern v_irq
.extern v_fiq
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.section .init
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_vectors:
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_start:
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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:
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@ Switch to System mode
msr cpsr_c, #0xdf
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@ Get loader base from ELF loader
mov r4, r0
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@ Output 0x42 to the debug port
mov r0, #0x42
bl debug_output
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@ 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:
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@ 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:
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@ 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:
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mov r0, #0x84
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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]
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bx lr
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.pool
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