mirror of
https://github.com/fail0verflow/bootmii.git
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79 lines
1.3 KiB
ArmAsm
79 lines
1.3 KiB
ArmAsm
/*
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bootmii - a Free Software replacement for the Nintendo/BroadOn boot2.
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system startup
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Copyright (C) 2008, 2009 Hector Martin "marcan" <marcan@marcan.st>
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# This code is licensed to you under the terms of the GNU GPL, version 2;
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# see file COPYING or http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt
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*/
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.arm
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.extern _main
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.extern __got_start
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.extern __got_end
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.extern __bss_start
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.extern __bss_end
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.extern __stack_addr
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.globl _start
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.globl debug_output
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.section .init
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_start:
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@ Get loader base from parent
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mov r4, r0
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@ Output 0x42 to the debug port
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mov r0, #0x42
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bl debug_output
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@ Set up a stack
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ldr sp, =__stack_addr
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@ Output 0x43 to the debug port
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mov r0, #0x43
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bl debug_output
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@ clear BSS
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ldr r1, =__bss_start
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ldr r2, =__bss_end
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mov r3, #0
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bss_loop:
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@ check for the end
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cmp r1, r2
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bge done_bss
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@ clear the word and move on
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str r3, [r1]
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add r1, r1, #4
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b bss_loop
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done_bss:
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mov r0, #0x44
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bl debug_output
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@ take the plunge
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mov r0, r4
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ldr r1, =_main+1
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mov lr, pc
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bx r1
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@ _main returned! Go to whatever address it returned...
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mov pc, r0
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.pool
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debug_output:
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@ load address of port
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mov r3, #0xd800000
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@ load old value
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ldr r2, [r3, #0xe0]
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@ clear debug byte
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bic r2, r2, #0xFF0000
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@ insert new value
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and r0, r0, #0xFF
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orr r2, r2, r0, LSL #16
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@ store back
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str r2, [r3, #0xe0]
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bx lr
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