2008-04-17 07:48:13 +02:00
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;------------------------------------------------------------------------------
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;*
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;* Copyright 2006 - 2007, Intel Corporation
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;* All rights reserved. This program and the accompanying materials
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;* are licensed and made available under the terms and conditions of the BSD License
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;* which accompanies this distribution. The full text of the license may be found at
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;* http://opensource.org/licenses/bsd-license.php
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;*
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;* THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
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;* WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
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;*
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;* bootsect.asm
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;*
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;* Abstract:
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;*
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;------------------------------------------------------------------------------
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.model small
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.stack
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.486p
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.code
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FAT_DIRECTORY_ENTRY_SIZE EQU 020h
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FAT_DIRECTORY_ENTRY_SHIFT EQU 5
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BLOCK_SIZE EQU 0200h
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BLOCK_MASK EQU 01ffh
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BLOCK_SHIFT EQU 9
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; "EFILDR_____"
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LOADER_FILENAME_PART1 EQU 04c494645h ; "EFIL"
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LOADER_FILENAME_PART2 EQU 020205244h ; "DR__"
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LOADER_FILENAME_PART3 EQU 020202020h ; "____"
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org 0h
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Ia32Jump:
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jmp BootSectorEntryPoint ; JMP inst - 3 bytes
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nop
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OemId db "INTEL " ; OemId - 8 bytes
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; BPB data below will be fixed by tool
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SectorSize dw 0 ; Sector Size - 16 bits
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SectorsPerCluster db 0 ; Sector Per Cluster - 8 bits
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ReservedSectors dw 0 ; Reserved Sectors - 16 bits
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NoFats db 0 ; Number of FATs - 8 bits
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RootEntries dw 0 ; Root Entries - 16 bits
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Sectors dw 0 ; Number of Sectors - 16 bits
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Media db 0 ; Media - 8 bits - ignored
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SectorsPerFat dw 0 ; Sectors Per FAT - 16 bits
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SectorsPerTrack dw 0 ; Sectors Per Track - 16 bits - ignored
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Heads dw 0 ; Heads - 16 bits - ignored
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HiddenSectors dd 0 ; Hidden Sectors - 32 bits - ignored
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LargeSectors dd 0 ; Large Sectors - 32 bits
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PhysicalDrive db 0 ; PhysicalDriveNumber - 8 bits - ignored
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CurrentHead db 0 ; Current Head - 8 bits
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Signature db 0 ; Signature - 8 bits - ignored
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Id db " " ; Id - 4 bytes
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FatLabel db " " ; Label - 11 bytes
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SystemId db "FAT12 " ; SystemId - 8 bytes
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BootSectorEntryPoint:
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ASSUME ds:@code
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ASSUME ss:@code
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; ****************************************************************************
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; Start Print
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; ****************************************************************************
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lea si, cs:[StartString]
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call PrintString
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; ****************************************************************************
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; Print over
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; ****************************************************************************
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mov ax,cs ; ax = 0
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mov ss,ax ; ss = 0
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add ax,1000h
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mov ds,ax
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mov sp,07c00h ; sp = 0x7c00
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mov bp,sp ; bp = 0x7c00
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mov ah,8 ; ah = 8 - Get Drive Parameters Function
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mov byte ptr [bp+PhysicalDrive],dl ; BBS defines that BIOS would pass the booting driver number to the loader through DL
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int 13h ; Get Drive Parameters
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2009-03-05 15:13:25 +01:00
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xor ax,ax ; ax = 0
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mov al,dh ; al = dh (number of sides (0 based))
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inc al ; MaxHead = al + 1
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push ax ; 0000:7bfe = MaxHead
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mov al,cl ; al = cl (CL = sectors per track)
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and al,03fh ; MaxSector = al & 0x3f
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push ax ; 0000:7bfc = MaxSector
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2008-04-17 07:48:13 +02:00
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cmp word ptr [bp+SectorSignature],0aa55h ; Verify Boot Sector Signature
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jne BadBootSector
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mov cx,word ptr [bp+RootEntries] ; cx = RootEntries
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shl cx,FAT_DIRECTORY_ENTRY_SHIFT ; cx = cx * 32 = cx * sizeof(FAT_DIRECTORY_ENTRY) = Size of Root Directory in bytes
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mov bx,cx ; bx = size of the Root Directory in bytes
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and bx,BLOCK_MASK ; See if it is an even number of sectors long
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jne BadBootSector ; If is isn't, then the boot sector is bad.
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mov bx,cx ; bx = size of the Root Directory in bytes
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shr bx,BLOCK_SHIFT ; bx = size of Root Directory in sectors
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mov al,byte ptr [bp+NoFats] ; al = NoFats
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xor ah,ah ; ah = 0 ==> ax = NoFats
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mul word ptr [bp+SectorsPerFat] ; ax = NoFats * SectorsPerFat
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add ax,word ptr [bp+ReservedSectors] ; ax = NoFats * SectorsPerFat + ReservedSectors = RootLBA
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push ds
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pop es
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xor di,di ; Store directory in es:di = 1000:0000
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call ReadBlocks ; Read entire Root Directory
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add ax,bx ; ax = NoFats * SectorsPerFat + ReservedSectors + RootDirSectors = FirstClusterLBA (FirstDataSector)
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mov word ptr [bp],ax ; Save FirstClusterLBA (FirstDataSector) for later use
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; dx - variable storage (initial value is 0)
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; bx - loader (initial value is 0)
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xor dx, dx
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xor bx, bx
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FindEFILDR:
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cmp dword ptr [di],LOADER_FILENAME_PART1 ; Compare to "EFIL"
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jne FindVARSTORE
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cmp dword ptr [di+4],LOADER_FILENAME_PART2
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jne FindVARSTORE
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cmp dword ptr [di+7],LOADER_FILENAME_PART3
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jne FindVARSTORE
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mov bx, word ptr [di+26] ; bx = Start Cluster for EFILDR <----------------------------------
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test dx, dx
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je FindNext ; Efivar.bin is not loaded
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jmp FoundAll
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FindVARSTORE:
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; if the file is not loader file, see if it's "EFIVAR BIN"
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cmp dword ptr [di], 056494645h ; Compare to "EFIV"
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jne FindNext
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cmp dword ptr [di+4], 020205241h ; Compare to "AR "
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jne FindNext
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cmp dword ptr [di+7], 04e494220h ; Compare to " BIN"
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jne FindNext
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mov dx, di ; dx = Offset of Start Cluster for Efivar.bin <---------------------
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add dx, 26
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test bx, bx
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je FindNext ; Efildr is not loaded
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jmp FoundAll
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FindNext:
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; go to next find
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add di,FAT_DIRECTORY_ENTRY_SIZE ; Increment di
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sub cx,FAT_DIRECTORY_ENTRY_SIZE ; Decrement cx
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; TODO: jump to FindVarStore if ...
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jne FindEFILDR
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jmp NotFoundAll
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FoundAll:
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2009-03-05 15:13:25 +01:00
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FoundEFILDR: ; 0x7cfe
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2008-04-17 07:48:13 +02:00
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mov cx,bx ; cx = Start Cluster for EFILDR <----------------------------------
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mov ax,cs ; Destination = 2000:0000
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add ax,2000h
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mov es,ax
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xor di,di
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ReadFirstClusterOfEFILDR:
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mov ax,cx ; ax = StartCluster
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sub ax,2 ; ax = StartCluster - 2
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xor bh,bh
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mov bl,byte ptr [bp+SectorsPerCluster] ; bx = SectorsPerCluster
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push dx
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mul bx
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pop dx ; ax = (StartCluster - 2) * SectorsPerCluster
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add ax, word ptr [bp] ; ax = FirstClusterLBA + (StartCluster-2)*SectorsPerCluster
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xor bh,bh
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mov bl,byte ptr [bp+SectorsPerCluster] ; bx = Number of Sectors in a cluster
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push es
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call ReadBlocks
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pop ax
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JumpIntoFirstSectorOfEFILDR:
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2009-03-05 15:13:25 +01:00
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mov word ptr [bp+JumpSegment],ax ; 0x7d26
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JumpFarInstruction: ; 0x7d2a
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2008-04-17 07:48:13 +02:00
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db 0eah
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JumpOffset:
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dw 0000h
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JumpSegment:
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dw 2000h
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PrintString:
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mov ax,0b800h
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mov es,ax
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mov ax, 07c0h
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mov ds, ax
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mov cx, 7
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mov di, 160
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rep movsw
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ret
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; ****************************************************************************
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; ReadBlocks - Reads a set of blocks from a block device
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;
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; AX = Start LBA
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; BX = Number of Blocks to Read
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; ES:DI = Buffer to store sectors read from disk
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; ****************************************************************************
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; cx = Blocks
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; bx = NumberOfBlocks
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; si = StartLBA
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ReadBlocks:
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pusha
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add eax,dword ptr [bp+LBAOffsetForBootSector] ; Add LBAOffsetForBootSector to Start LBA
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add eax,dword ptr [bp+HiddenSectors] ; Add HiddenSectors to Start LBA
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mov esi,eax ; esi = Start LBA
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mov cx,bx ; cx = Number of blocks to read
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ReadCylinderLoop:
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mov bp,07bfch ; bp = 0x7bfc
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mov eax,esi ; eax = Start LBA
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xor edx,edx ; edx = 0
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movzx ebx,word ptr [bp] ; bx = MaxSector
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div ebx ; ax = StartLBA / MaxSector
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inc dx ; dx = (StartLBA % MaxSector) + 1
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sub bx,dx ; bx = MaxSector - Sector
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inc bx ; bx = MaxSector - Sector + 1
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cmp cx,bx ; Compare (Blocks) to (MaxSector - Sector + 1)
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jg LimitTransfer
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mov bx,cx ; bx = Blocks
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LimitTransfer:
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push cx
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mov cl,dl ; cl = (StartLBA % MaxSector) + 1 = Sector
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xor dx,dx ; dx = 0
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div word ptr [bp+2] ; ax = ax / (MaxHead + 1) = Cylinder
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; dx = ax % (MaxHead + 1) = Head
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push bx ; Save number of blocks to transfer
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mov dh,dl ; dh = Head
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mov bp,07c00h ; bp = 0x7c00
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mov dl,byte ptr [bp+PhysicalDrive] ; dl = Drive Number
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mov ch,al ; ch = Cylinder
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mov al,bl ; al = Blocks
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mov ah,2 ; ah = Function 2
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mov bx,di ; es:bx = Buffer address
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int 013h
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jc DiskError
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pop bx
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pop cx
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movzx ebx,bx
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add esi,ebx ; StartLBA = StartLBA + NumberOfBlocks
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sub cx,bx ; Blocks = Blocks - NumberOfBlocks
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mov ax,es
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shl bx,(BLOCK_SHIFT-4)
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add ax,bx
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mov es,ax ; es:di = es:di + NumberOfBlocks*BLOCK_SIZE
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cmp cx,0
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jne ReadCylinderLoop
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popa
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ret
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; ****************************************************************************
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; ERROR Condition:
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; ****************************************************************************
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2009-03-05 15:13:25 +01:00
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NotFoundAll: ; 0x7da6
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2008-04-17 07:48:13 +02:00
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; if we found EFILDR, continue
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test bx,bx
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jne FoundEFILDR
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BadBootSector:
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DiskError:
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lea si, cs:[ErrorString]
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call PrintString
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Halt:
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jmp Halt
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StartString:
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db 'B', 0ch, 'S', 0ch, 't', 0ch, 'a', 0ch, 'r', 0ch, 't', 0ch, '!', 0ch
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ErrorString:
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db 'B', 0ch, 'E', 0ch, 'r', 0ch, 'r', 0ch, 'o', 0ch, 'r', 0ch, '!', 0ch
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; ****************************************************************************
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; LBA Offset for BootSector, need patched by tool for HD boot.
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; ****************************************************************************
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org 01fah
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LBAOffsetForBootSector:
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dd 0h
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; ****************************************************************************
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; Sector Signature
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; ****************************************************************************
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org 01feh
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SectorSignature:
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dw 0aa55h ; Boot Sector Signature
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end
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