| 1 | ; Project name : XTIDE Universal BIOS
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| 2 | ; Description : Reading and jumping to boot sector.
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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, 2011-2012 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 | ; Section containing code
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| 21 | SECTION .text
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| 22 |
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| 23 | ;--------------------------------------------------------------------
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| 24 | ; BootSector_TryToLoadFromDriveDL
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| 25 | ; Parameters:
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| 26 | ; DL: Drive to boot from (translated, 00h or 80h)
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| 27 | ; DS: RAMVARS segment
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| 28 | ; Returns:
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| 29 | ; ES:BX: Ptr to boot sector (if successful)
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| 30 | ; CF: Set if boot sector loaded successfully
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| 31 | ; Cleared if failed to load boot sector
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| 32 | ; Corrupts registers:
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| 33 | ; AX, CX, DH, SI, DI, (DL if failed to read boot sector)
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| 34 | ;--------------------------------------------------------------------
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| 35 | BootSector_TryToLoadFromDriveDL:
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| 36 | call DetectPrint_TryToBootFromDL
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| 37 | call LoadFirstSectorFromDriveDL
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| 38 | jc SHORT .FailedToLoadFirstSector
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| 39 |
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| 40 | test dl, dl
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| 41 | jns SHORT .AlwaysBootFromFloppyDriveForBooterGames
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| 42 | cmp WORD [es:bx+510], 0AA55h ; Valid boot sector?
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| 43 | jne SHORT .FirstHardDiskSectorNotBootable
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| 44 | .AlwaysBootFromFloppyDriveForBooterGames:
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| 45 | stc
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| 46 | ret
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| 47 | .FailedToLoadFirstSector:
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| 48 | call DetectPrint_FailedToLoadFirstSector
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| 49 | clc
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| 50 | ret
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| 51 | .FirstHardDiskSectorNotBootable:
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| 52 | mov si, g_szBootSectorNotFound
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| 53 | call DetectPrint_NullTerminatedStringFromCSSIandSetCF
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| 54 | clc
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| 55 | ret
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| 56 |
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| 57 | ;--------------------------------------------------------------------
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| 58 | ; LoadFirstSectorFromDriveDL
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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 | ; Returns:
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| 62 | ; AH: INT 13h error code
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| 63 | ; ES:BX: Ptr to boot sector (if successful)
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| 64 | ; CF: Cleared if read successful
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| 65 | ; Set if any error
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| 66 | ; Corrupts registers:
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| 67 | ; AL, CX, DH, DI
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| 68 | ;--------------------------------------------------------------------
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| 69 | LoadFirstSectorFromDriveDL:
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| 70 | LOAD_BDA_SEGMENT_TO es, bx ; ES:BX now points to...
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| 71 | mov bx, BOOTVARS.rgbBootSect ; ...boot sector location
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| 72 | mov di, BOOT_READ_RETRY_TIMES ; Initialize retry counter
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| 73 |
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| 74 | .ReadRetryLoop:
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| 75 | call .ResetBootDriveFromDL
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| 76 | call .LoadFirstSectorFromDLtoESBX
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| 77 | jnc SHORT .Return
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| 78 | dec di ; Decrement retry counter
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| 79 | jnz SHORT .ReadRetryLoop ; Loop while retries left
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| 80 | .Return:
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| 81 | ret
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| 82 |
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| 83 | ;--------------------------------------------------------------------
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| 84 | ; .ResetBootDriveFromDL
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| 85 | ; Parameters:
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| 86 | ; DL: Drive to boot from (translated, 00h or 80h)
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| 87 | ; Returns:
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| 88 | ; AH: INT 13h error code
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| 89 | ; CF: Cleared if read successful
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| 90 | ; Set if any error
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| 91 | ; Corrupts registers:
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| 92 | ; AL
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| 93 | ;--------------------------------------------------------------------
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| 94 | .ResetBootDriveFromDL:
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| 95 | xor ax, ax ; AH=0h, Disk Controller Reset
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| 96 | test dl, dl ; Floppy drive?
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| 97 | jns SHORT .SkipAltReset
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| 98 | mov ah, 0Dh ; AH=Dh, Reset Hard Disk (Alternate reset)
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| 99 | .SkipAltReset:
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| 100 | int BIOS_DISK_INTERRUPT_13h
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| 101 | ret
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| 102 |
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| 103 | ;--------------------------------------------------------------------
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| 104 | ; .LoadFirstSectorFromDLtoESBX
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| 105 | ; Parameters:
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| 106 | ; DL: Drive to boot from (translated, 00h or 80h)
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| 107 | ; ES:BX: Destination buffer for boot sector
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| 108 | ; Returns:
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| 109 | ; AH: INT 13h error code
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| 110 | ; ES:BX: Ptr to boot sector
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| 111 | ; CF: Cleared if read successful
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| 112 | ; Set if any error
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| 113 | ; Corrupts registers:
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| 114 | ; AL, CX, DH
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| 115 | ;--------------------------------------------------------------------
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| 116 | .LoadFirstSectorFromDLtoESBX:
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| 117 | mov ax, 0201h ; Read 1 sector
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| 118 | mov cx, 1 ; Cylinder 0, Sector 1
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| 119 | xor dh, dh ; Head 0
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| 120 | int BIOS_DISK_INTERRUPT_13h
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| 121 | ret
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