1 | ; Project name : XTIDE Universal BIOS |
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2 | ; Description : Defines for BOOTVARS struct used by boot menu |
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3 | ; and drive initialization. |
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4 | %ifndef BOOTVARS_INC |
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5 | %define BOOTVARS_INC |
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6 | |
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7 | |
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8 | BOOT_READ_RETRY_TIMES EQU 3 |
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9 | |
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10 | |
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11 | |
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12 | ; Pre-boot variables. These do not exist after successful boot to OS. |
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13 | ; Segment is always 0000h, same as BDA segment |
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14 | struc BOOTVARS |
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15 | resb 7C00h |
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16 | .rgbAtaInfo: ; 7C00h, ATA Information for drive detection |
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17 | .rgbBootSect resb 512 ; 7C00h, Boot sector |
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18 | resb 256 ; Boot Menu stack |
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19 | .rgbMnuStack: |
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20 | .dwPostStack resb 4 ; POST stack pointer when entering INT 19h |
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21 | .rgBootNfo: ; Array containing BOOTNFO structs |
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22 | endstruc |
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23 | |
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24 | |
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25 | ;-------------------------------------------------------------------- |
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26 | ; Stores POST stack pointer to BOOTVARS. |
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27 | ; |
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28 | ; STORE_POST_STACK_POINTER |
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29 | ; Parameters: |
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30 | ; ES: BDA and Interrupt Vector segment (zero) |
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31 | ; Returns: |
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32 | ; Nothing |
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33 | ; Corrupts registers: |
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34 | ; Nothing |
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35 | ;-------------------------------------------------------------------- |
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36 | %macro STORE_POST_STACK_POINTER 0 |
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37 | mov [es:BOOTVARS.dwPostStack], sp |
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38 | mov [es:BOOTVARS.dwPostStack+2], ss |
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39 | %endmacro |
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40 | |
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41 | |
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42 | ;-------------------------------------------------------------------- |
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43 | ; Initializes stack for boot menu usage. |
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44 | ; POST stack is not large enough when DPTs are stored to 30:0h. |
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45 | ; |
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46 | ; Note regarding LOAD_BDA_SEGMENT_TO: If you force the use of SP |
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47 | ; then you also have to unconditionally enable the CLI/STI pair. |
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48 | ; The reason for this is that only some buggy 808x CPU:s need the |
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49 | ; CLI/STI instruction pair when changing stacks. Other CPU:s disable |
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50 | ; interrupts automatically when SS is modified for the duration of |
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51 | ; the immediately following instruction to give time to change SP. |
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52 | ; |
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53 | ; SWITCH_TO_BOOT_MENU_STACK |
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54 | ; Parameters: |
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55 | ; Nothing |
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56 | ; Returns: |
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57 | ; SS:SP: Pointer to top of Boot Menu stack |
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58 | ; Corrupts registers: |
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59 | ; Nothing |
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60 | ;-------------------------------------------------------------------- |
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61 | %macro SWITCH_TO_BOOT_MENU_STACK 0 |
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62 | %ifndef USE_186 |
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63 | cli ; Disable interrupts |
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64 | %endif |
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65 | LOAD_BDA_SEGMENT_TO ss, sp |
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66 | mov sp, BOOTVARS.rgbMnuStack ; Load offset to stack |
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67 | %ifndef USE_186 |
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68 | sti ; Enable interrupts |
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69 | %endif |
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70 | %endmacro |
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71 | |
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72 | |
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73 | ;-------------------------------------------------------------------- |
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74 | ; Restores SS and SP to initial boot loader values. |
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75 | ; |
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76 | ; Note! Must return with AX=0 and CF preserved. |
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77 | ; See Int19hMenu_JumpToBootSector_or_RomBoot. |
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78 | ; |
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79 | ; SWITCH_BACK_TO_POST_STACK |
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80 | ; Parameters: |
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81 | ; AX: BDA and Interrupt Vector segment (zero) |
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82 | ; Returns: |
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83 | ; SS:SP: Ptr to POST stack |
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84 | ; Corrupts registers: |
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85 | ; Nothing (not even FLAGS) |
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86 | ;-------------------------------------------------------------------- |
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87 | %macro SWITCH_BACK_TO_POST_STACK 0 |
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88 | %ifndef USE_386 |
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89 | cli |
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90 | mov ss, ax |
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91 | mov sp, [ss:BOOTVARS.dwPostStack] |
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92 | mov ss, [ss:BOOTVARS.dwPostStack+2] |
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93 | sti |
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94 | %else |
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95 | mov ss, ax |
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96 | lss sp, [ss:BOOTVARS.dwPostStack] |
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97 | %endif |
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98 | %endmacro |
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99 | |
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100 | |
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101 | %endif ; BOOTVARS_INC |
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