1 | ; File name : BootVars.asm |
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2 | ; Project name : IDE BIOS |
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3 | ; Created date : 1.4.2010 |
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4 | ; Last update : 12.4.2010 |
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5 | ; Author : Tomi Tilli |
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6 | ; Description : Functions to access BOOTVARS struct. |
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7 | |
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8 | ; Section containing code |
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9 | SECTION .text |
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10 | |
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11 | ;-------------------------------------------------------------------- |
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12 | ; Stores POST stack pointer to BOOTVARS. |
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13 | ; |
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14 | ; BootVars_StorePostStackPointer |
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15 | ; Parameters: |
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16 | ; DS: BDA and Interrupt Vector segment (zero) |
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17 | ; Returns: |
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18 | ; Nothing |
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19 | ; Corrupts registers: |
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20 | ; AX |
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21 | ;-------------------------------------------------------------------- |
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22 | ALIGN JUMP_ALIGN |
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23 | BootVars_StorePostStackPointer: |
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24 | pop ax ; Pop return address |
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25 | mov [BOOTVARS.dwPostStack], sp |
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26 | mov [BOOTVARS.dwPostStack+2], ss |
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27 | jmp ax |
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28 | |
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29 | |
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30 | ;-------------------------------------------------------------------- |
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31 | ; Initializes stack for boot menu usage. |
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32 | ; POST stack is not large enough when DPTs are stored to 30:0h. |
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33 | ; |
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34 | ; BootVars_SwitchToBootMenuStack |
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35 | ; Parameters: |
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36 | ; Nothing |
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37 | ; Returns: |
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38 | ; SS:SP: Pointer to top of Boot Menu stack |
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39 | ; Corrupts registers: |
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40 | ; AX |
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41 | ;-------------------------------------------------------------------- |
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42 | ALIGN JUMP_ALIGN |
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43 | BootVars_SwitchToBootMenuStack: |
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44 | pop ax ; Pop return address |
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45 | cli ; Disable interrupts |
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46 | LOAD_BDA_SEGMENT_TO ss, sp |
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47 | mov sp, BOOTVARS.rgbMnuStack ; Load offset to stack |
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48 | sti ; Enable interrupts |
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49 | jmp ax |
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50 | |
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51 | |
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52 | ;-------------------------------------------------------------------- |
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53 | ; Restores SS and SP to initial boot loader values. |
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54 | ; |
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55 | ; BootVars_SwitchBackToPostStack |
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56 | ; Parameters: |
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57 | ; Nothing |
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58 | ; Returns: |
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59 | ; SS:SP: Ptr to POST stack |
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60 | ; Corrupts registers: |
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61 | ; AX |
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62 | ;-------------------------------------------------------------------- |
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63 | ALIGN JUMP_ALIGN |
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64 | BootVars_SwitchBackToPostStack: |
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65 | pop ax ; Pop return address |
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66 | cli ; Disable interrupts |
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67 | LOAD_BDA_SEGMENT_TO ss, sp |
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68 | eLSS sp, ss:BOOTVARS.dwPostStack |
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69 | sti ; Enable interrupts |
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70 | jmp ax |
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71 | |
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72 | |
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73 | ;-------------------------------------------------------------------- |
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74 | ; Backups system INT 18h ROM Boot / Boot Failure handler and |
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75 | ; installs our own for boot menu INT 18h callbacks. |
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76 | ; |
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77 | ; BootVars_StoreSystemInt18hAndInstallOurs |
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78 | ; Parameters: |
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79 | ; DS: BDA and Interrupt Vector segment (zero) |
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80 | ; Returns: |
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81 | ; Nothing |
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82 | ; Corrupts registers: |
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83 | ; AX, BX, ES |
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84 | ;-------------------------------------------------------------------- |
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85 | ALIGN JUMP_ALIGN |
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86 | BootVars_StoreSystemInt18hAndInstallOurs: |
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87 | mov bx, INTV_BOOT_FAILURE*4 ; Offset to INT 18h vector |
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88 | les ax, [bx] ; Load system INT 18h |
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89 | mov [BOOTVARS.dwSys18h], ax |
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90 | mov [BOOTVARS.dwSys18h+2], es |
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91 | mov WORD [bx], Int18h_BootError ; Install our INT 18h |
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92 | mov WORD [bx+2], cs |
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93 | ret |
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94 | |
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95 | |
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96 | ;-------------------------------------------------------------------- |
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97 | ; Restores system INT 18h ROM Boot or Boot Error handler. |
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98 | ; |
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99 | ; BootVars_RestoreSystemInt18h |
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100 | ; Parameters: |
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101 | ; Nothing |
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102 | ; Returns: |
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103 | ; Nothing |
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104 | ; Corrupts registers: |
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105 | ; AX, DS, ES |
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106 | ;-------------------------------------------------------------------- |
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107 | ALIGN JUMP_ALIGN |
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108 | BootVars_RestoreSystemInt18h: |
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109 | LOAD_BDA_SEGMENT_TO ds, ax |
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110 | les ax, [BOOTVARS.dwSys18h] |
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111 | mov [INTV_BOOT_FAILURE*4], ax |
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112 | mov [INTV_BOOT_FAILURE*4+2], es |
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113 | ret |
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