| [96] | 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 | ; 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 | ; BootSector_TryToLoadFromDriveDL
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| 9 | ; Parameters:
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| 10 | ; DL: Drive to boot from (translated, 00h or 80h)
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| 11 | ; DS: RAMVARS segment
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| 12 | ; Returns:
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| [294] | 13 | ; ES:BX: Ptr to boot sector (if successful)
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| 14 | ; CF: Set if boot sector loaded successfully
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| [96] | 15 | ; Cleared if failed to load boot sector
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| 16 | ; Corrupts registers:
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| [143] | 17 | ; AX, CX, DH, SI, DI, (DL if failed to read boot sector)
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| [96] | 18 | ;--------------------------------------------------------------------
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| 19 | ALIGN JUMP_ALIGN
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| 20 | BootSector_TryToLoadFromDriveDL:
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| 21 | call BootPrint_TryToBootFromDL
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| 22 | call LoadFirstSectorFromDriveDL
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| 23 | jc SHORT .FailedToLoadFirstSector
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| 24 |
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| [128] | 25 | test dl, dl
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| 26 | jns SHORT .AlwaysBootFromFloppyDriveForBooterGames
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| [96] | 27 | cmp WORD [es:bx+510], 0AA55h ; Valid boot sector?
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| 28 | jne SHORT .FirstHardDiskSectorNotBootable
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| 29 | .AlwaysBootFromFloppyDriveForBooterGames:
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| 30 | stc
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| 31 | ret
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| 32 | .FailedToLoadFirstSector:
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| 33 | call BootPrint_FailedToLoadFirstSector
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| 34 | clc
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| 35 | ret
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| 36 | .FirstHardDiskSectorNotBootable:
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| [143] | 37 | mov si, g_szBootSectorNotFound
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| 38 | call BootMenuPrint_NullTerminatedStringFromCSSIandSetCF
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| [96] | 39 | clc
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| 40 | ret
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| 41 |
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| 42 | ;--------------------------------------------------------------------
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| 43 | ; LoadFirstSectorFromDriveDL
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| 44 | ; Parameters:
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| 45 | ; DL: Drive to boot from (translated, 00h or 80h)
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| 46 | ; Returns:
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| 47 | ; AH: INT 13h error code
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| [294] | 48 | ; ES:BX: Ptr to boot sector (if successful)
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| 49 | ; CF: Cleared if read successful
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| [96] | 50 | ; Set if any error
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| 51 | ; Corrupts registers:
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| 52 | ; AL, CX, DH, DI
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| 53 | ;--------------------------------------------------------------------
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| 54 | ALIGN JUMP_ALIGN
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| 55 | LoadFirstSectorFromDriveDL:
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| 56 | LOAD_BDA_SEGMENT_TO es, bx ; ES:BX now points to...
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| 57 | mov bx, BOOTVARS.rgbBootSect ; ...boot sector location
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| 58 | mov di, BOOT_READ_RETRY_TIMES ; Initialize retry counter
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| 59 | ALIGN JUMP_ALIGN
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| 60 | .ReadRetryLoop:
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| 61 | call .ResetBootDriveFromDL
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| 62 | call .LoadFirstSectorFromDLtoESBX
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| 63 | jnc SHORT .Return
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| 64 | dec di ; Decrement retry counter
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| 65 | jnz SHORT .ReadRetryLoop ; Loop while retries left
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| 66 | .Return:
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| 67 | ret
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| 68 |
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| 69 | ;--------------------------------------------------------------------
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| 70 | ; .ResetBootDriveFromDL
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| 71 | ; Parameters:
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| 72 | ; DL: Drive to boot from (translated, 00h or 80h)
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| 73 | ; Returns:
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| 74 | ; AH: INT 13h error code
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| [294] | 75 | ; CF: Cleared if read successful
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| [96] | 76 | ; Set if any error
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| 77 | ; Corrupts registers:
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| 78 | ; AL
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| 79 | ;--------------------------------------------------------------------
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| 80 | ALIGN JUMP_ALIGN
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| 81 | .ResetBootDriveFromDL:
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| 82 | xor ax, ax ; AH=0h, Disk Controller Reset
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| [128] | 83 | test dl, dl ; Floppy drive?
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| 84 | jns SHORT .SkipAltReset
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| 85 | mov ah, 0Dh ; AH=Dh, Reset Hard Disk (Alternate reset)
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| 86 | .SkipAltReset:
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| [148] | 87 | int BIOS_DISK_INTERRUPT_13h
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| [96] | 88 | ret
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| 89 |
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| 90 | ;--------------------------------------------------------------------
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| 91 | ; .LoadFirstSectorFromDLtoESBX
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| 92 | ; Parameters:
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| 93 | ; DL: Drive to boot from (translated, 00h or 80h)
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| 94 | ; ES:BX: Destination buffer for boot sector
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| 95 | ; Returns:
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| 96 | ; AH: INT 13h error code
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| 97 | ; ES:BX: Ptr to boot sector
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| [294] | 98 | ; CF: Cleared if read successful
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| [96] | 99 | ; Set if any error
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| 100 | ; Corrupts registers:
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| 101 | ; AL, CX, DH
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| 102 | ;--------------------------------------------------------------------
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| 103 | ALIGN JUMP_ALIGN
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| 104 | .LoadFirstSectorFromDLtoESBX:
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| 105 | mov ax, 0201h ; Read 1 sector
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| 106 | mov cx, 1 ; Cylinder 0, Sector 1
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| 107 | xor dh, dh ; Head 0
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| [148] | 108 | int BIOS_DISK_INTERRUPT_13h
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| [96] | 109 | ret
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