1 | ; Project name : Assembly Library
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2 | ; Description : DOS Critical Error Handler (24h) replacements.
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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, 2011-2013 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 | ; Note! Only DOS functions 01h - 0Ch, 30h and 59h can be called from a Critical Error Handler.
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21 |
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22 | ; DOS Critical Error Handler return values
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23 | struc CRITICAL_ERROR_ACTION
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24 | .ignoreErrorAndContinueProcessingRequest resb 1
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25 | .retryOperation resb 1
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26 | .terminateProgramAsThoughInt21hAH4ChCalled resb 1
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27 | .failSystemCallInProgress resb 1 ; Needs DOS 3.1+
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28 | endstruc
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29 |
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30 |
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31 | ; Section containing code
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32 | SECTION .text
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33 |
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34 | ;--------------------------------------------------------------------
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35 | ; DosCritical_InstallNewHandlerFromCSDX
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36 | ; Parameters:
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37 | ; CS:DX: New Critical Error Handler
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38 | ; Returns:
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39 | ; Nothing
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40 | ; Corrupts registers:
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41 | ; AX
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42 | ;--------------------------------------------------------------------
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43 | ALIGN JUMP_ALIGN
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44 | DosCritical_InstallNewHandlerFromCSDX:
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45 | push ds
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46 |
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47 | mov al, DOS_CRITICAL_ERROR_HANDLER_24h
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48 | call HookInterruptVectorInALwithHandlerInCSDX
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49 |
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50 | pop ds
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51 | ret
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52 |
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53 |
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54 | ;--------------------------------------------------------------------
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55 | ; DosCritical_RestoreDosHandler
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56 | ; Parameters:
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57 | ; Nothing
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58 | ; Returns:
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59 | ; Nothing
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60 | ; Corrupts registers:
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61 | ; Nothing
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62 | ;--------------------------------------------------------------------
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63 | ALIGN JUMP_ALIGN
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64 | DosCritical_RestoreDosHandler:
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65 | push ds
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66 | push dx
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67 | push ax
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68 |
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69 | lds dx, [cs:PSP.fpInt24hCriticalError]
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70 | mov ax, (SET_INTERRUPT_VECTOR<<8) | DOS_CRITICAL_ERROR_HANDLER_24h
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71 | int DOS_INTERRUPT_21h
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72 |
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73 | pop ax
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74 | pop dx
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75 | pop ds
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76 | ret
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77 |
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78 |
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79 | ;--------------------------------------------------------------------
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80 | ; DosCritical_CustomHandler
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81 | ; Parameters:
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82 | ; Nothing
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83 | ; Returns:
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84 | ; Nothing
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85 | ; Corrupts registers:
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86 | ; Nothing
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87 | ;--------------------------------------------------------------------
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88 | ALIGN JUMP_ALIGN
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89 | DosCritical_CustomHandler:
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90 | add sp, 6 ; Remove the INT 24h return address and flags from stack
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91 |
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92 | mov ah, GET_EXTENDED_ERROR_INFORMATION ; Requires DOS 3.0+
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93 | xor bx, bx
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94 | int DOS_INTERRUPT_21h
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95 | mov [cs:bLastCriticalError], al
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96 |
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97 | pop ax
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98 | pop bx
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99 | pop cx
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100 | pop dx
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101 | pop si
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102 | pop di
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103 | pop bp
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104 | pop ds
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105 | pop es
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106 | iret ; Return from the INT 21h call
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107 |
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108 | bLastCriticalError: db 0
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109 |
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110 |
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111 | ;--------------------------------------------------------------------
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112 | ; DosCritical_HandlerToIgnoreAllErrors
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113 | ; Parameters:
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114 | ; Nothing
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115 | ; Returns:
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116 | ; AL: CRITICAL_ERROR_ACTION
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117 | ; Corrupts registers:
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118 | ; Nothing
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119 | ;--------------------------------------------------------------------
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120 | ALIGN JUMP_ALIGN
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121 | DosCritical_HandlerToIgnoreAllErrors:
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122 | mov al, CRITICAL_ERROR_ACTION.ignoreErrorAndContinueProcessingRequest
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123 | iret
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124 |
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