1 | ; Project name : XTIDE Universal BIOS |
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2 | ; Description : Int 19h Handler (Boot Loader). |
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3 | |
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4 | ; |
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5 | ; XTIDE Universal BIOS and Associated Tools |
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6 | ; Copyright (C) 2009-2010 by Tomi Tilli, 2011-2012 by XTIDE Universal BIOS Team. |
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7 | ; |
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8 | ; This program is free software; you can redistribute it and/or modify |
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9 | ; it under the terms of the GNU General Public License as published by |
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10 | ; the Free Software Foundation; either version 2 of the License, or |
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11 | ; (at your option) any later version. |
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12 | ; |
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13 | ; This program is distributed in the hope that it will be useful, |
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14 | ; but WITHOUT ANY WARRANTY; without even the implied warranty of |
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15 | ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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16 | ; GNU General Public License for more details. |
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17 | ; Visit http://www.gnu.org/licenses/old-licenses/gpl-2.0.html |
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18 | ; |
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19 | |
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20 | ; Section containing code |
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21 | SECTION .text |
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22 | |
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23 | ;-------------------------------------------------------------------- |
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24 | ; Int19h_BootLoaderHandler |
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25 | ; Parameters: |
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26 | ; Nothing |
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27 | ; Returns: |
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28 | ; Never returns (loads operating system) |
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29 | ;-------------------------------------------------------------------- |
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30 | Int19h_BootLoaderHandler: |
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31 | sti ; Allow timer interrupts |
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32 | LOAD_BDA_SEGMENT_TO es, ax ; Load BDA segment (zero) to ES |
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33 | ; Fall to .PrepareBootLoaderStack |
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34 | |
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35 | |
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36 | ;-------------------------------------------------------------------- |
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37 | ; Drive detection and boot menu use lots of stack so it is |
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38 | ; wise to relocate stack. Otherwise something important from |
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39 | ; interrupt vectors are likely corrupted, likely our own DPTs if |
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40 | ; they are located to 30:0h. |
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41 | ; |
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42 | ; .PrepareBootLoaderStack |
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43 | ; Parameters: |
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44 | ; ES: BDA and interrupt vector segment (zero) |
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45 | ; Returns: |
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46 | ; Never returns (loads operating system) |
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47 | ;-------------------------------------------------------------------- |
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48 | .PrepareBootLoaderStack: |
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49 | STORE_POST_STACK_POINTER |
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50 | SWITCH_TO_BOOT_MENU_STACK |
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51 | ; Fall to .InitializeDisplay |
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52 | |
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53 | |
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54 | ;-------------------------------------------------------------------- |
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55 | ; .InitializeDisplay |
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56 | ; Parameters: |
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57 | ; ES: BDA and interrupt vector segment (zero) |
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58 | ; Returns: |
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59 | ; Never returns (loads operating system) |
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60 | ;-------------------------------------------------------------------- |
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61 | .InitializeDisplay: |
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62 | ; Change display mode if necessary |
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63 | mov ax, [cs:ROMVARS.wDisplayMode] ; AH 00h = Set Video Mode |
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64 | cmp al, DEFAULT_TEXT_MODE |
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65 | je SHORT .InitializeDisplayLibrary |
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66 | int BIOS_VIDEO_INTERRUPT_10h |
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67 | .InitializeDisplayLibrary: |
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68 | call DetectPrint_InitializeDisplayContext |
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69 | ; Fall to .InitializeBiosAndDetectDrives |
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70 | |
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71 | |
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72 | ;-------------------------------------------------------------------- |
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73 | ; .InitializeBiosAndDetectDrives |
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74 | ; Parameters: |
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75 | ; ES: BDA and interrupt vector segment (zero) |
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76 | ; Returns: |
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77 | ; DS: RAMVARS segment |
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78 | ;-------------------------------------------------------------------- |
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79 | call Initialize_AndDetectDrives |
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80 | ; Fall to SelectDriveToBootFrom |
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81 | |
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82 | |
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83 | ;-------------------------------------------------------------------- |
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84 | ; SelectDriveToBootFrom |
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85 | ; Parameters: |
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86 | ; DS: RAMVARS segment |
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87 | ; ES: BDA and interrupt vector segment (zero) |
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88 | ; Returns: |
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89 | ; Never returns (loads operating system) |
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90 | ;-------------------------------------------------------------------- |
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91 | SelectDriveToBootFrom: |
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92 | %ifdef MODULE_HOTKEYS |
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93 | call HotkeyBar_UpdateDuringDriveDetection |
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94 | |
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95 | %ifdef MODULE_BOOT_MENU |
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96 | mov di, BOOTVARS.hotkeyVars+HOTKEYVARS.bScancode |
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97 | cmp BYTE [es:di], BOOT_MENU_HOTKEY_SCANCODE |
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98 | jne SHORT .DoNotDisplayBootMenu |
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99 | |
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100 | ; Stop blinking the Boot Menu hotkey and display menu |
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101 | mov BYTE [es:di], 0 |
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102 | call HotkeyBar_DrawToTopOfScreen |
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103 | call BootMenu_DisplayAndStoreSelectionAsHotkey |
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104 | .DoNotDisplayBootMenu: |
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105 | %endif |
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106 | |
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107 | ; Check if ROM boot (INT 18h) wanted |
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108 | cmp BYTE [es:BOOTVARS.hotkeyVars+HOTKEYVARS.bScancode], ROM_BOOT_HOTKEY_SCANCODE |
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109 | je SHORT JumpToBootSector_or_RomBoot ; CF clear so ROM boot |
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110 | |
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111 | ; Get Primary boot drive number to DL |
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112 | call HotkeyBar_GetPrimaryBootDriveNumberToDL |
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113 | %else |
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114 | call GetPrimaryBootDriveToDLwhenNotUsingModuleHotkeys |
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115 | %endif ; MODULE_HOTKEYS |
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116 | |
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117 | ; Try to boot from Primary boot drive (00h by default) |
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118 | call TryToBootFromPrimaryOrSecondaryBootDevice |
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119 | jc SHORT JumpToBootSector_or_RomBoot |
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120 | |
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121 | ; Try to boot from Secondary boot device (80h by default) |
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122 | %ifdef MODULE_HOTKEYS |
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123 | call HotkeyBar_GetSecondaryBootDriveNumberToDL |
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124 | %else |
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125 | call GetPrimaryBootDriveToDLwhenNotUsingModuleHotkeys |
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126 | xor dl, 80h |
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127 | %endif |
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128 | call TryToBootFromPrimaryOrSecondaryBootDevice |
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129 | |
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130 | %ifdef MODULE_BOOT_MENU |
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131 | ; Force Boot Menu hotkey to display boot menu |
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132 | mov BYTE [es:BOOTVARS.hotkeyVars+HOTKEYVARS.bScancode], BOOT_MENU_HOTKEY_SCANCODE |
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133 | jnc SHORT SelectDriveToBootFrom |
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134 | %endif |
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135 | ; Fall to JumpToBootSector_or_RomBoot |
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136 | |
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137 | |
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138 | ;-------------------------------------------------------------------- |
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139 | ; JumpToBootSector_or_RomBoot |
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140 | ; |
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141 | ; Switches back to the POST stack, clears the DS and ES registers, |
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142 | ; and either jumps to the MBR (Master Boot Record) that was just read, |
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143 | ; or calls the ROM's boot routine on interrupt 18. |
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144 | ; |
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145 | ; Parameters: |
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146 | ; DL: Drive to boot from (translated, 00h or 80h) |
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147 | ; CF: Set for Boot Sector Boot |
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148 | ; Clear for ROM Boot |
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149 | ; ES:BX: (if CF set) Ptr to boot sector |
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150 | ; |
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151 | ; Returns: |
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152 | ; Never returns |
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153 | ;-------------------------------------------------------------------- |
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154 | JumpToBootSector_or_RomBoot: |
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155 | mov cx, es ; Preserve MBR segment (can't push because of stack change) |
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156 | mov ax, 0 ; NOTE: can't use XOR (LOAD_BDA_SEGMENT_TO) as it impacts CF |
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157 | SWITCH_BACK_TO_POST_STACK |
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158 | |
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159 | ; clear segment registers before boot sector or rom call |
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160 | mov ds, ax |
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161 | mov es, ax |
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162 | %ifdef USE_386 |
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163 | mov fs, ax |
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164 | mov gs, ax |
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165 | %endif |
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166 | jnc SHORT .romboot |
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167 | |
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168 | ; jump to boot sector |
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169 | push cx ; sgment address for MBR |
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170 | push bx ; offset address for MBR |
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171 | retf ; NOTE: DL is set to the drive number |
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172 | |
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173 | ; Boot by calling INT 18h (ROM Basic of ROM DOS) |
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174 | .romboot: |
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175 | int BIOS_BOOT_FAILURE_INTERRUPT_18h ; Never returns |
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176 | |
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177 | |
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178 | ;-------------------------------------------------------------------- |
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179 | ; TryToBootFromPrimaryOrSecondaryBootDevice |
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180 | ; Parameters |
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181 | ; DL: Drive selected as boot device |
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182 | ; DS: RAMVARS segment |
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183 | ; ES: BDA and interrupt vector segment (zero) |
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184 | ; Returns: |
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185 | ; DL: Drive to boot from (translated, 00h or 80h) |
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186 | ; CF: Set for Boot Sector Boot |
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187 | ; Clear for ROM Boot |
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188 | ; ES:BX: (if CF set) Ptr to boot sector |
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189 | ; Corrupts registers: |
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190 | ; AX, CX, DH, SI, DI, (DL if failed to read boot sector) |
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191 | ;-------------------------------------------------------------------- |
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192 | %ifndef MODULE_HOTKEYS |
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193 | TryToBootFromPrimaryOrSecondaryBootDevice EQU BootSector_TryToLoadFromDriveDL |
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194 | |
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195 | %else |
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196 | TryToBootFromPrimaryOrSecondaryBootDevice: |
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197 | call DriveXlate_SetDriveToSwap |
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198 | call DriveXlate_ToOrBack |
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199 | jmp BootSector_TryToLoadFromDriveDL |
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200 | %endif |
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201 | |
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202 | |
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203 | ;-------------------------------------------------------------------- |
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204 | ; GetPrimaryBootDriveToDLwhenNotUsingModuleHotkeys |
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205 | ; Parameters |
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206 | ; Nothing |
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207 | ; Returns: |
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208 | ; DL: Drive to boot from (00h or 80h) |
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209 | ; Corrupts registers: |
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210 | ; Nothing |
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211 | ;-------------------------------------------------------------------- |
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212 | %ifndef MODULE_HOTKEYS |
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213 | GetPrimaryBootDriveToDLwhenNotUsingModuleHotkeys: |
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214 | mov dl, [cs:ROMVARS.bBootDrv] |
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215 | and dl, 80h ; Only 00h and 80h allowed when not using MODULE_HOTKEYS |
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216 | ret |
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217 | %endif |
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