| 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 | LOAD_BDA_SEGMENT_TO ds, ax
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| 21 | call BootVars_StorePostStackPointer
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| 22 |
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| 23 | ; Install new INT 19h handler now that BOOTVARS has been initialized
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| 24 | mov WORD [INTV_BOOTSTRAP*4], DisplayBootMenu
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| 25 | mov WORD [INTV_BOOTSTRAP*4+2], cs
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| 26 | ; Fall to DisplayBootMenu
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| 27 |
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| 28 | ;--------------------------------------------------------------------
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| 29 | ; DisplayBootMenu
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| 30 | ; Parameters:
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| 31 | ; Nothing
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| 32 | ; Returns:
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| 33 | ; Never returns
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| 34 | ;--------------------------------------------------------------------
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| 35 | ALIGN JUMP_ALIGN
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| 36 | DisplayBootMenu:
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| 37 | call BootVars_SwitchToBootMenuStack
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| 38 | call RamVars_GetSegmentToDS
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| 39 | ; Fall to .ProcessMenuSelectionsUntilBootable
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| 40 |
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| 41 | ;--------------------------------------------------------------------
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| 42 | ; .ProcessMenuSelectionsUntilBootable
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| 43 | ; Parameters:
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| 44 | ; DS: RAMVARS segment
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| 45 | ; Returns:
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| 46 | ; Never returns
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| 47 | ;--------------------------------------------------------------------
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| 48 | ALIGN JUMP_ALIGN
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| 49 | .ProcessMenuSelectionsUntilBootable:
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| 50 | call BootMenu_DisplayAndReturnSelection
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| 51 | call DriveXlate_ToOrBack ; Translate drive number
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| 52 | call BootSector_TryToLoadFromDriveDL
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| 53 | jnc SHORT .ProcessMenuSelectionsUntilBootable ; Boot failure, show menu again
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| 54 | call BootVars_SwitchBackToPostStack
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| 55 | ; Fall to JumpToBootSector
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| 56 |
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| 57 | ;--------------------------------------------------------------------
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| 58 | ; JumpToBootSector
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| 59 | ; Parameters:
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| 60 | ; DL: Drive to boot from (translated, 00h or 80h)
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| 61 | ; ES:BX: Ptr to boot sector
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| 62 | ; Returns:
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| 63 | ; Never returns
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| 64 | ;--------------------------------------------------------------------
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| 65 | ALIGN JUMP_ALIGN
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| 66 | JumpToBootSector:
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| 67 | push es ; Push boot sector segment
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| 68 | push bx ; Push boot sector offset
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| 69 | call ClearSegmentsForBoot
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| 70 | xor dh, dh ; Device supported by INT 13h
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| 71 | retf
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| 72 |
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| 73 |
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| 74 | ;--------------------------------------------------------------------
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| 75 | ; Int19hMenu_RomBoot
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| 76 | ; Parameters:
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| 77 | ; DS: RAMVARS segment
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| 78 | ; Returns:
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| 79 | ; Never returns
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| 80 | ;--------------------------------------------------------------------
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| 81 | ALIGN JUMP_ALIGN
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| 82 | Int19hMenu_RomBoot:
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| 83 | call BootVars_SwitchBackToPostStack
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| 84 | call ClearSegmentsForBoot
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| 85 | int INTV_BOOT_FAILURE ; Never returns
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| 86 |
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| 87 |
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| 88 | ;--------------------------------------------------------------------
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| 89 | ; ClearSegmentsForBoot
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| 90 | ; Parameters:
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| 91 | ; Nothing
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| 92 | ; Returns:
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| 93 | ; DS=ES: Zero
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| 94 | ; Corrupts registers:
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| 95 | ; AX
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| 96 | ;--------------------------------------------------------------------
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| 97 | ALIGN JUMP_ALIGN
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| 98 | ClearSegmentsForBoot:
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| 99 | xor ax, ax
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| 100 | mov ds, ax
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| 101 | mov es, ax
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| 102 | ret
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