114 lines
2.2 KiB
ArmAsm
114 lines
2.2 KiB
ArmAsm
/*
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mini - a Free Software replacement for the Nintendo/BroadOn IOS.
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ELF loader: system startup
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Copyright (C) 2008, 2009 Hector Martin "marcan" <marcan@marcansoft.com>
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, version 2.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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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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.extern delay
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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 real address of _start
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sub r4, pc, #8
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@ Subtract offset to get the address that we were loaded at
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ldr r0, =_start
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sub r4, 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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add sp, r4
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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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@ relocate the GOT entries
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ldr r1, =__got_start
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add r1, r4
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ldr r2, =__got_end
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add r2, r4
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got_loop:
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@ check for the end
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cmp r1, r2
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beq done_got
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@ read the GOT entry
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ldr r3, [r1]
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@ add our base address
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add r3, r4
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str r3, [r1]
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@ move on
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add r1, r1, #4
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b got_loop
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done_got:
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@ clear BSS
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ldr r1, =__bss_start
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add r1, r4
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ldr r2, =__bss_end
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add r2, r4
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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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beq 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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bl _main
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@ _main returned! Go to whatever address it returned...
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mov r1, r0
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mov r0, r4
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mov pc, r1
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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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mov pc, lr
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