1 | ; Project name : XTIDE Universal BIOS |
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2 | ; Description : Int 19h BIOS functions for Boot Menu. |
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3 | |
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4 | ; Section containing code |
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5 | SECTION .text |
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6 | |
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7 | ;-------------------------------------------------------------------- |
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8 | ; Initial Boot Menu Loader. |
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9 | ; Prepares BOOTVARS for displaying Boot Menu and accepting |
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10 | ; callbacks from INT 18h and 19h. |
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11 | ; |
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12 | ; Int19hMenu_BootLoader |
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13 | ; Parameters: |
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14 | ; Nothing |
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15 | ; Returns: |
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16 | ; Jumps to Int19hMenu_Display, then never returns |
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17 | ;-------------------------------------------------------------------- |
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18 | ALIGN JUMP_ALIGN |
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19 | Int19hMenu_BootLoader: |
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20 | ; Store POST stack pointer |
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21 | LOAD_BDA_SEGMENT_TO ds, ax |
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22 | STORE_POST_STACK_POINTER |
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23 | |
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24 | ; Install new INT 19h handler now that BOOTVARS has been initialized |
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25 | mov WORD [INTV_BOOTSTRAP*4], DisplayBootMenu |
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26 | mov WORD [INTV_BOOTSTRAP*4+2], cs |
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27 | ; Fall to DisplayBootMenu |
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28 | |
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29 | ;-------------------------------------------------------------------- |
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30 | ; DisplayBootMenu |
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31 | ; Parameters: |
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32 | ; Nothing |
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33 | ; Returns: |
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34 | ; Never returns |
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35 | ;-------------------------------------------------------------------- |
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36 | ALIGN JUMP_ALIGN |
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37 | DisplayBootMenu: |
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38 | SWITCH_TO_BOOT_MENU_STACK |
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39 | CALL_DISPLAY_LIBRARY InitializeDisplayContext |
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40 | call RamVars_GetSegmentToDS |
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41 | ; Fall to .ProcessMenuSelectionsUntilBootable |
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42 | |
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43 | ;-------------------------------------------------------------------- |
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44 | ; .ProcessMenuSelectionsUntilBootable |
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45 | ; Parameters: |
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46 | ; DS: RAMVARS segment |
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47 | ; Returns: |
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48 | ; Never returns |
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49 | ;-------------------------------------------------------------------- |
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50 | ALIGN JUMP_ALIGN |
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51 | .ProcessMenuSelectionsUntilBootable: |
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52 | call BootMenu_DisplayAndReturnSelection |
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53 | call DriveXlate_ToOrBack ; Translate drive number |
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54 | call BootSector_TryToLoadFromDriveDL |
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55 | jnc SHORT .ProcessMenuSelectionsUntilBootable ; Boot failure, show menu again |
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56 | SWITCH_BACK_TO_POST_STACK |
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57 | ; Fall to JumpToBootSector |
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58 | |
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59 | ;-------------------------------------------------------------------- |
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60 | ; JumpToBootSector |
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61 | ; Parameters: |
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62 | ; DL: Drive to boot from (translated, 00h or 80h) |
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63 | ; ES:BX: Ptr to boot sector |
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64 | ; Returns: |
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65 | ; Never returns |
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66 | ;-------------------------------------------------------------------- |
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67 | ALIGN JUMP_ALIGN |
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68 | JumpToBootSector: |
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69 | push es ; Push boot sector segment |
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70 | push bx ; Push boot sector offset |
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71 | call ClearSegmentsForBoot |
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72 | retf |
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73 | |
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74 | |
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75 | ;-------------------------------------------------------------------- |
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76 | ; Int19hMenu_RomBoot |
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77 | ; Parameters: |
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78 | ; DS: RAMVARS segment |
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79 | ; Returns: |
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80 | ; Never returns |
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81 | ;-------------------------------------------------------------------- |
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82 | ALIGN JUMP_ALIGN |
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83 | Int19hMenu_RomBoot: |
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84 | SWITCH_BACK_TO_POST_STACK |
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85 | call ClearSegmentsForBoot |
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86 | int INTV_BOOT_FAILURE ; Never returns |
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87 | |
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88 | |
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89 | ;-------------------------------------------------------------------- |
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90 | ; ClearSegmentsForBoot |
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91 | ; Parameters: |
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92 | ; Nothing |
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93 | ; Returns: |
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94 | ; DX: Zero |
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95 | ; DS=ES: Zero |
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96 | ; Corrupts registers: |
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97 | ; Nothing |
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98 | ;-------------------------------------------------------------------- |
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99 | ALIGN JUMP_ALIGN |
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100 | ClearSegmentsForBoot: |
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101 | xor dx, dx ; Device supported by INT 13h |
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102 | mov ds, dx |
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103 | mov es, dx |
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104 | ret |
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