1 | /** |
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2 | * @file start.S |
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3 | * |
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4 | * RTEMS entry point. |
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5 | */ |
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6 | /* |
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7 | * RTEMS GBA BSP |
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8 | * |
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9 | * Copyright (c) by Jeff Frohwein. |
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10 | * |
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11 | * Copyright (c) 2003, Jason Wilkins. |
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12 | * |
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13 | * Copyright (c) 2004 Markku Puro <markku.puro@kopteri.net> |
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14 | * based on crt0.S v1.28 by Jeff Frohwein |
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15 | * |
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16 | * The license and distribution terms for this file may be |
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17 | * found in the file LICENSE in this distribution or at |
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18 | * |
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19 | * http://www.rtems.com/license/LICENSE. |
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20 | * |
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21 | * $Id$ |
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22 | */ |
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23 | |
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24 | /***************************************************************************** |
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25 | * This source file is based on work by Jeff Frohwein and Jason Wilkins |
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26 | ***************************************************************************** |
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27 | ***************************************************************************** |
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28 | * crt0.S v1.28 by Jeff Frohwein |
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29 | * : |
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30 | * This file is released into the public domain for commercial |
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31 | * or non-commercial usage with no restrictions placed upon it. |
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32 | ***************************************************************************** |
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33 | * Copyright 2003, Jason Wilkins. This source code is free for any use except |
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34 | * that this copyright notice and the following disclaimers remain intact when |
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35 | * the source is distributed. Object code and binary distributions may be made |
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36 | * as if the code were in the public domain. |
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37 | * |
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38 | * THIS CODE WAS NOT MADE IN ASSOCIATION WITH NINTENDO AND DOES NOT MAKE USE |
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39 | * OF ANY INTELLECTUAL PROPERTY CLAIMED BY NINTENDO. |
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40 | * |
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41 | * GAMEBOY ADVANCE IS A TRADEMARK OF NINTENDO. |
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42 | * |
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43 | * THIS CODE HAS BEEN PROVIDED "AS-IS" WITHOUT A WARRANTY OF ANY KIND, EITHER |
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44 | * EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO IMPLIED WARRANTIES OF |
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45 | * MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. THE ENTIRE RISK AS TO THE |
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46 | * QUALITY OR PERFORMANCE OF THE CODE IS WITH YOU. |
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47 | * |
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48 | * IN NO EVENT, UNLESS AGREED TO IN WRITING, WILL ANY COPYRIGHT HOLDER, OR ANY |
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49 | * OTHER PARTY, BE HELD LIABLE FOR ANY DAMAGES RESULTING FROM THE USE OR |
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50 | * INABILITY TO USE THIS CODE. |
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51 | *****************************************************************************/ |
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52 | |
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53 | #define __asm__ |
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54 | #include <rtems/asm.h> |
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55 | #include <asm_macros.h> |
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56 | #include <arm_mode_bits.h> |
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57 | /* @cond INCLUDE_ASM */ |
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58 | |
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59 | #ifndef NINTENDO_LOGO |
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60 | #define NINTENDO_LOGO 1 |
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61 | #endif |
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62 | |
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63 | #ifndef GBA_MULTIBOOT |
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64 | #define GBA_MULTIBOOT 1 |
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65 | #endif |
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66 | |
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67 | #ifndef GAME_TITLE |
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68 | #define GAME_TITLE "RTEMS-RTOS " |
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69 | #endif |
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70 | |
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71 | #ifdef GBA_MULTIBOOT |
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72 | #ifndef GAME_CODE |
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73 | #define GAME_CODE "MB " |
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74 | #endif |
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75 | #ifndef COMPLEMENT_CHECK |
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76 | #define COMPLEMENT_CHECK 0xE2 |
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77 | #endif |
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78 | #else |
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79 | #ifndef GAME_CODE |
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80 | #define GAME_CODE "GBA " |
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81 | #endif |
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82 | #ifndef COMPLEMENT_CHECK |
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83 | #define COMPLEMENT_CHECK 0xC7 |
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84 | #endif |
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85 | #endif |
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86 | |
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87 | #ifndef MAKER_CODE |
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88 | #define MAKER_CODE "00" |
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89 | #endif |
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90 | |
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91 | /** |
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92 | * RTEMS entry point |
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93 | * function void _start(void) |
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94 | * |
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95 | */ |
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96 | /*****************************************************************************\ |
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97 | ROM Header |
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98 | \*****************************************************************************/ |
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99 | |
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100 | .text |
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101 | .align |
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102 | .arm |
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103 | |
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104 | /*---------------------------------------------------------------------------+ |
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105 | | Nintendo Header: |
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106 | | A special header is required or the GBA will refuse to run your code. |
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107 | | |
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108 | | File offsets from 0x0200000 or 0x08000000. |
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109 | +----------------------------------------------------------------------------*/ |
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110 | PUBLIC_ARM_FUNCTION(_start) |
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111 | b SYM(_real_start) /* 0x00 Entry Point */ |
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112 | SYM(_gba_rom_header): |
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113 | #if NINTENDO_LOGO /* 0x04 Nintendo Logo Character Data */ |
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114 | #include "logo.S" |
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115 | #else |
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116 | .fill 156, 1, 0 /* 0x04 Nintendo Logo Character Data */ |
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117 | #endif |
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118 | .ascii GAME_TITLE /* 0xA0 Game Title */ |
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119 | .ascii GAME_CODE /* 0xAC Game Code */ |
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120 | .ascii MAKER_CODE /* 0xB0 Maker Code */ |
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121 | .byte 0x96 /* 0xB2 Fixed Value */ |
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122 | .byte 0 /* 0xB3 Main Unit Code */ |
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123 | .byte 0 /* 0xB4 Device Type */ |
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124 | .byte 0, 0, 0, 0, 0, 0, 0 /* 0xB5 Reserved (7 Bytes) */ |
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125 | .byte 0 /* 0xBC Software Version No. */ |
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126 | .byte COMPLEMENT_CHECK /* 0xBD Complement Check */ |
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127 | .byte 0, 0 /* 0xBE Reserved */ |
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128 | .Lheader_end: |
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129 | |
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130 | |
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131 | #if GBA_MULTIBOOT |
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132 | /*---------------------------------------------------------------------------+ |
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133 | | Multiboot Header: |
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134 | | The following header is required if the code is meant for Multiboot. |
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135 | | |
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136 | | If the code has been downloaded through the serial port, then the GBA BIOS |
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137 | | will set offset 0xC0 depending on the boot method: |
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138 | | 1 = JoyBus, 3 = Multiboot |
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139 | | It remains 0 for cartridges. |
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140 | | |
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141 | | offset 0xC4 will be set to the GBA's assigned slave number 1-3. |
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142 | | This header also defines the symbols _boot_method and _slave_number for |
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143 | | easy reference to these values. Some libraries may depend on them whether |
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144 | | or not the code is meant for Multiboot. |
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145 | | |
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146 | +----------------------------------------------------------------------------*/ |
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147 | SYM(_gba_multiboot_start): |
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148 | b SYM(_real_start) /* 0xC0 Multiboot Entry Point */ |
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149 | OBJECT(_boot_method) |
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150 | .byte 0 /* 0xC4 Boot Method */ |
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151 | OBJECT(_slave_number) |
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152 | .byte 0 /* 0xC5 Slave Number (1-3) */ |
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153 | .align |
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154 | STATIC_OBJECT(_gba_mb_reserved) |
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155 | .word 0, 0, 0, 0, 0, 0 /* 0xC8 Reserved (6 words) */ |
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156 | SYM(_gba_joybus_start): |
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157 | b SYM(_real_start) /* 0xE0 JoyBus Entry Point */ |
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158 | .Lmultiboot_header_end: |
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159 | #endif |
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160 | |
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161 | /*---------------------------------------------------------------------------+ |
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162 | | Restore registers and stack from GBA bios IRQ frame and call ISR_Handler |
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163 | +----------------------------------------------------------------------------*/ |
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164 | EXTERN(_ISR_Handler) |
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165 | .align |
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166 | PUBLIC_ARM_FUNCTION(_gba_ISR_handler) |
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167 | ldmfd r13!,{r0-r3,r12,r14} |
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168 | b arm_exc_interrupt |
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169 | LABEL_END(_gba_ISR_handler) |
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170 | |
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171 | |
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172 | /*---------------------------------------------------------------------------+ |
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173 | | Code to initialize the low-level BSP environment |
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174 | +----------------------------------------------------------------------------*/ |
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175 | SYM(_real_start): |
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176 | /* Initialize IRQ and USR Stack Pointers */ |
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177 | SYM(_gba_init_stacks): |
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178 | mov r0, #(Mode_IRQ | Int_Bits) /* No interrupts */ |
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179 | msr cpsr, r0 /* switch to IRQ mode */ |
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180 | ldr sp, =__sp_irq /* defined in linkcmds */ |
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181 | mov r0, #(ModePriv | Int_Bits) /* No interrupts */ |
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182 | msr cpsr, r0 /* switch to System Mode */ |
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183 | ldr sp, =__sp_usr /* defined in linkcmds */ |
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184 | |
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185 | /* Switch to Thumb Mode */ |
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186 | SYM(_gba_bx_thumb): |
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187 | adr r0, .Lthumb + 1 |
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188 | bx r0 |
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189 | .thumb |
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190 | .Lthumb: |
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191 | /* Reduce gameboy waitstates */ |
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192 | SYM(_reduce_waitstates): |
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193 | ldr r1, =0x4000204 |
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194 | ldrh r0, =0x4490 |
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195 | strh r0, [r1] |
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196 | |
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197 | |
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198 | #if GBA_MULTIBOOT |
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199 | /*---------------------------------------------------------------------------+ |
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200 | | Load Multiboot Image from ROM into RAM: |
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201 | | Check to see if the image is meant for Multiboot or GamePak. If it is for |
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202 | | Multiboot then check if it is currently running from EWRAM or from CARTROM. |
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203 | | If it is running from CARTROM, then it needs to be copied to EWRAM and |
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204 | | re-executed from the beginning. |
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205 | | |
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206 | | The reason for all this is to allow a program to be used "as-is" with a |
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207 | | flash-cart, emulator, or MBV2-style Multiboot cable without rebuilding. |
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208 | | |
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209 | | NOTE: Any branchs used above this code need to be relative. |
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210 | +----------------------------------------------------------------------------*/ |
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211 | STATIC_THUMB_FUNCTION(_gba_load_multiboot) |
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212 | ldr r0, =_start /* 8000000h=GamePak 2000000h=Multiboot*/ |
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213 | ldr r1, =__gba_rom_start /* defined in linkcmds */ |
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214 | cmp r0, r1 |
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215 | beq SYM(_no_load_multiboot)/* skip if GamePak */ |
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216 | mov r3, pc |
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217 | cmp r1, r3 /* check program counter */ |
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218 | bhi SYM(_no_load_multiboot)/* skip if already running from EWRAM */ |
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219 | sub r3, r1, r0 /* diff between _start and CARTROM */ |
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220 | ldr r2, =__load_stop_data /* defined in linkcmds */ |
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221 | add r2, r2, r3 /* adjust pointer into ROM */ |
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222 | bl SYM(gba_move_memory) |
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223 | |
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224 | /* patch multiboot header */ |
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225 | ldr r0, =SYM(_boot_method) |
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226 | mov r1, #3 |
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227 | str r1, [r0] |
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228 | |
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229 | /* remember that multiboot image came from GamePak */ |
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230 | ldr r0, =SYM(_gba_flash_loaded_multiboot) |
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231 | mov r1, #0 |
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232 | str r1, [r0] |
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233 | |
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234 | ldr r0, =SYM(_start) |
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235 | bx r0 /* restart */ |
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236 | LABEL_END(_gba_load_multiboot) |
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237 | |
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238 | .align 4 |
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239 | OBJECT(_gba_flash_loaded_multiboot) |
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240 | .word -1 |
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241 | LABEL_END(_gba_flash_loaded_multiboot) |
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242 | SYM(_no_load_multiboot): |
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243 | #endif |
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244 | |
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245 | /* Initialize Standard Sections */ |
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246 | STATIC_THUMB_FUNCTION(_gba_init_std_sections) |
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247 | /* Copy internal work ram (iwram section ROM to RAM)*/ |
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248 | ldr r0,=__iwram_start |
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249 | ldr r1,=__load_start_iwram |
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250 | ldr r2,=__load_stop_iwram |
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251 | bl SYM(gba_move_memory) |
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252 | |
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253 | /* Copy external work ram (ewram section ROM to RAM) */ |
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254 | ldr r0,=__ewram_start |
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255 | ldr r1,=__load_start_ewram |
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256 | ldr r2,=__load_stop_ewram |
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257 | bl SYM(gba_move_memory) |
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258 | |
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259 | /* load initial values of variables like 'int foo = 42' */ |
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260 | ldr r0, =__data_start /* defined in linkcmds */ |
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261 | ldr r1, =__load_start_data /* defined in linkcmds */ |
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262 | ldr r2, =__load_stop_data /* defined in linkcmds */ |
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263 | bl SYM(gba_move_memory) |
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264 | |
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265 | /* zero the bss */ |
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266 | ldr r0, =__bss_start /* defined in linkcmds */ |
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267 | ldr r1, =__bss_end /* defined in linkcmds */ |
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268 | bl SYM(gba_zero_memory) |
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269 | LABEL_END(_gba_init_std_sections) |
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270 | |
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271 | /* Initialize Interrupt Vector */ |
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272 | STATIC_THUMB_FUNCTION(_gba_init_intr_vect) |
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273 | ldr r1, =__irq_vector /* defined in linkcmds */ |
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274 | ldr r0, =SYM(_gba_ISR_handler) |
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275 | str r0, [r1] |
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276 | LABEL_END(_gba_init_intr_vect) |
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277 | |
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278 | |
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279 | /* Enter the C code. If it returns, then restart */ |
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280 | STATIC_THUMB_FUNCTION(_gba_call_arm_boot_card) |
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281 | adr r1, .Larm |
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282 | bx r1 |
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283 | .arm |
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284 | .Larm: |
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285 | ldr r1, =boot_card |
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286 | mov r0, #0 |
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287 | bl SYM(_gba_call_via_r1) |
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288 | |
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289 | ldr r0, =SYM(_gba_reset) |
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290 | SYM(_gba_call_via_r1): |
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291 | bx r1 |
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292 | |
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293 | /* GBA Reset */ |
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294 | PUBLIC_ARM_FUNCTION(_gba_reset) |
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295 | adr r0, .Lthumb2 + 1 |
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296 | bx r0 |
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297 | .thumb |
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298 | .Lthumb2: |
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299 | /* disable interrupts */ |
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300 | ldr r0, =0x04000208 |
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301 | mov r1, #0 |
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302 | strb r1, [r0] |
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303 | |
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304 | /* reset stack, default free area */ |
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305 | ldr r0, =0x03007F00 |
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306 | mov sp, r0 |
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307 | |
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308 | #if GBA_MULTIBOOT |
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309 | ldr r0, =SYM(_gba_flash_loaded_multiboot) |
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310 | ldr r0, [r0] |
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311 | cmp r0, #0 |
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312 | beq SYM(_reset) |
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313 | #endif |
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314 | |
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315 | ldr r0, =_start /* defined in linkcmds */ |
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316 | ldr r1, =__gba_rom_start /* defined in linkcmds */ |
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317 | sub r0, r0, r1 |
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318 | lsr r0, r0, #24 |
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319 | |
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320 | SYM(_reset): |
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321 | /* soft reset (swi 0) parameter: where is _start */ |
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322 | ldr r1, =0x03007FFA |
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323 | strb r0, [r1] |
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324 | mov r0, #0xFE /* clear all but EWRAM */ |
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325 | swi 1 |
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326 | swi 0 |
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327 | LABEL_END(_gba_reset) |
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328 | |
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329 | |
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330 | /*---------------------------------------------------------------------------+ |
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331 | | Library Functions |
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332 | +----------------------------------------------------------------------------*/ |
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333 | |
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334 | /* gba_zero_memory */ |
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335 | PUBLIC_THUMB_FUNCTION(gba_zero_memory) |
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336 | mov r2, #0 |
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337 | nop |
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338 | LABEL_END(gba_zero_memory) |
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339 | |
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340 | /* gba_set_memory */ |
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341 | PUBLIC_THUMB_FUNCTION(gba_set_memory) |
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342 | cmp r0, r1 |
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343 | bcs .Lset_memory_return |
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344 | |
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345 | .Lset_memory_loop: |
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346 | stmia r0!, {r2} |
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347 | cmp r0, r1 |
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348 | bcc .Lset_memory_loop |
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349 | |
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350 | .Lset_memory_return: |
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351 | bx lr |
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352 | LABEL_END(gba_set_memory) |
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353 | |
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354 | /* gba_move_memory */ |
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355 | .align |
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356 | PUBLIC_THUMB_FUNCTION(gba_move_memory) |
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357 | cmp r0, r1 |
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358 | bcc .Lforward_move /* if dst < src then forward copy */ |
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359 | bhi .Lreverse_move /* if dst > src then reverse copy */ |
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360 | bx lr /* else dst == src, nothing to do */ |
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361 | |
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362 | .Lforward_move: |
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363 | cmp r1, r2 |
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364 | bcs .Lmove_memory_return |
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365 | |
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366 | .Lforward_move_loop: |
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367 | ldmia r1!, {r3} |
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368 | stmia r0!, {r3} |
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369 | cmp r1, r2 |
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370 | bcc .Lforward_move_loop |
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371 | bx lr |
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372 | |
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373 | .Lreverse_move: |
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374 | cmp r2, r1 |
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375 | bls .Lmove_memory_return |
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376 | sub r3, r2, r1 |
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377 | add r0, r0, r3 |
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378 | |
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379 | .Lreverse_move_loop: |
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380 | sub r2, r2, #4 |
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381 | ldr r3, [r2] |
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382 | sub r0, r0, #4 |
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383 | str r3, [r0] |
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384 | cmp r2, r1 |
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385 | bhi .Lreverse_move_loop |
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386 | |
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387 | .Lmove_memory_return: |
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388 | bx lr |
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389 | LABEL_END(gba_move_memory) |
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390 | |
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391 | |
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392 | /* @todo FIXME: Remove unused handler needed by ../score/cpu_asm.S |
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393 | *****************************************************************************/ |
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394 | .arm |
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395 | .global SWI_Handler |
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396 | SWI_Handler: |
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397 | mov pc, lr |
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398 | /* @endcond */ |
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399 | |
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