mirror of https://github.com/acidanthera/audk.git
292 lines
12 KiB
ArmAsm
292 lines
12 KiB
ArmAsm
#------------------------------------------------------------------------------
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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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.code16:
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.equ FAT_DIRECTORY_ENTRY_SIZE, 0x020
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.equ FAT_DIRECTORY_ENTRY_SHIFT, 5
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.equ BLOCK_SIZE, 0x0200
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.equ BLOCK_MASK, 0x01ff
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.equ BLOCK_SHIFT, 9
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# "EFILDR_____"
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.equ LOADER_FILENAME_PART1, 0x04c494645 # "EFIL"
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.equ LOADER_FILENAME_PART2, 0x020205244 # "DR__"
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.equ LOADER_FILENAME_PART3, 0x020202020 # "____"
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.org 0x0
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.global _start
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_start:
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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: .ascii "INTEL " # OemId - 8 bytes
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# BPB data below will be fixed by tool
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SectorSize: .word 0 # Sector Size - 16 bits
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SectorsPerCluster: .byte 0 # Sector Per Cluster - 8 bits
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ReservedSectors: .word 0 # Reserved Sectors - 16 bits
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NoFats: .byte 0 # Number of FATs - 8 bits
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RootEntries: .word 0 # Root Entries - 16 bits
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Sectors: .word 0 # Number of Sectors - 16 bits
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Media: .byte 0 # Media - 8 bits - ignored
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SectorsPerFat: .word 0 # Sectors Per FAT - 16 bits
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SectorsPerTrack: .word 0 # Sectors Per Track - 16 bits - ignored
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Heads: .word 0 # Heads - 16 bits - ignored
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HiddenSectors: .long 0 # Hidden Sectors - 32 bits - ignored
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LargeSectors: .long 0 # Large Sectors - 32 bits
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PhysicalDrive: .byte 0 # PhysicalDriveNumber - 8 bits - ignored
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CurrentHead: .byte 0 # Current Head - 8 bits
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Signature: .byte 0 # Signature - 8 bits - ignored
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VolId: .ascii " " # Volume Serial Number- 4 bytes
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FatLabel: .ascii " " # Label - 11 bytes
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SystemId: .ascii "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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movw $StartString, %si
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call PrintString
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# ****************************************************************************
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# Print over
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# ****************************************************************************
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movw %cs, %ax # ax = 0
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movw %ax, %ss # ss = 0
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addw $0x1000, %ax
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movw %ax, %ds
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movw $0x7c00, %sp # sp = 0x7c00
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movw %sp, %bp # bp = 0x7c00
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movb $8, %ah # ah = 8 - Get Drive Parameters Function
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movb %dl, PhysicalDrive(%bp) # BBS defines that BIOS would pass the booting driver number to the loader through DL
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int $0x13 # Get Drive Parameters
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xorw %ax, %ax # ax = 0
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movb %dh, %al # al = dh
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incb %al # MaxHead = al + 1
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pushw %ax # 0000:7bfe = MaxHead
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movb %cl, %al # al = cl
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andb $0x3f, %al # MaxSector = al & 0x3f
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pushw %ax # 0000:7bfc = MaxSector
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cmpw $0xaa55, SectorSignature(%bp) # Verify Boot Sector Signature
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jne BadBootSector
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movw RootEntries(%bp), %cx # cx = RootEntries
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shlw $FAT_DIRECTORY_ENTRY_SHIFT, %cx # cx = cx * 32 = cx * sizeof(FAT_DIRECTORY_ENTRY) = Size of Root Directory in bytes
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movw %cx, %bx # bx = size of the Root Directory in bytes
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andw $BLOCK_MASK, %bx # 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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movw %cx, %bx # bx = size of the Root Directory in bytes
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shrw $BLOCK_SHIFT, %bx # bx = size of Root Directory in sectors
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movb NoFats(%bp), %al # al = NoFats
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xorb %ah, %ah # ah = 0 ==> ax = NoFats
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mulw SectorsPerFat(%bp) # ax = NoFats * SectorsPerFat
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addw ReservedSectors(%bp), %ax # ax = NoFats * SectorsPerFat + ReservedSectors = RootLBA
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pushw %ds
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popw %es
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xorw %di, %di # Store directory in es:di = 1000:0000
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call ReadBlocks # Read entire Root Directory
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addw %bx, %ax # ax = NoFats * SectorsPerFat + ReservedSectors + RootDirSectors = FirstClusterLBA (FirstDataSector)
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movw %ax, (%bp) # 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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xorw %dx, %dx
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xorw %bx, %bx
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FindEFILDR:
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cmpl $LOADER_FILENAME_PART1, (%di) # Compare to "EFIL"
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jne FindVARSTORE
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cmpl $LOADER_FILENAME_PART2, 4(%di)
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jne FindVARSTORE
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cmpl $LOADER_FILENAME_PART3, 7(%di)
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jne FindVARSTORE
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movw 26(%di), %bx # bx = Start Cluster for EFILDR <----------------------------------
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testw %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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cmpl $0x56494645, (%di) # Compare to "EFIV"
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jne FindNext
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cmpl $0x20205241, 4(%di) # Compare to "AR "
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jne FindNext
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cmpl $0x4e494220, 7(%di) # Compare to " BIN"
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jne FindNext
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movw %di, %dx # dx = Offset of Start Cluster for Efivar.bin <---------------------
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addw $26, %dx
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testw %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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addw $FAT_DIRECTORY_ENTRY_SIZE, %di # Increment di
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subw $FAT_DIRECTORY_ENTRY_SIZE, %cx # 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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FoundEFILDR:
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movw %bx, %cx # cx = Start Cluster for EFILDR <----------------------------------
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movw %cs, %ax # Destination = 2000:0000
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addw $0x2000, %ax
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movw %ax, %es
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xorw %di, %di
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ReadFirstClusterOfEFILDR:
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movw %cx, %ax # ax = StartCluster
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subw $2, %ax # ax = StartCluster - 2
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xorb %bh, %bh
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movb SectorsPerCluster(%bp), %bl # bx = SectorsPerCluster
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pushw %dx
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mulw %bx
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popw %dx # ax = (StartCluster - 2) * SectorsPerCluster
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addw (%bp), %ax # ax = FirstClusterLBA + (StartCluster-2)*SectorsPerCluster
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xorb %bh, %bh
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movb SectorsPerCluster(%bp), %bl # bx = Number of Sectors in a cluster
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pushw %es
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call ReadBlocks
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popw %ax
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JumpIntoFirstSectorOfEFILDR:
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movw %ax, JumpSegment(%bp)
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JumpFarInstruction:
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.byte 0xea
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JumpOffset:
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.word 0x000
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JumpSegment:
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.word 0x2000
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PrintString:
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movw $0xb800, %ax
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movw %ax, %es
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movw $0x7c0, %ax
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movw %ax, %ds
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movw $7, %cx
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movw $160, %di
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rep
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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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addl LBAOffsetForBootSector(%bp), %eax # Add LBAOffsetForBootSector to Start LBA
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addl HiddenSectors(%bp), %eax # Add HiddenSectors to Start LBA
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movl %eax, %esi # esi = Start LBA
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movw %bx, %cx # cx = Number of blocks to read
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ReadCylinderLoop:
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movw $0x7bfc, %bp # bp = 0x7bfc
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movl %esi, %eax # eax = Start LBA
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xorl %edx, %edx # edx = 0
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movzwl (%bp), %ebx # bx = MaxSector
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divl %ebx # ax = StartLBA / MaxSector
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incw %dx # dx = (StartLBA % MaxSector) + 1
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subw %dx, %bx # bx = MaxSector - Sector
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incw %bx # bx = MaxSector - Sector + 1
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cmpw %bx, %cx # Compare (Blocks) to (MaxSector - Sector + 1)
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jg LimitTransfer
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movw %cx, %bx # bx = Blocks
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LimitTransfer:
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pushw %cx
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movb %dl, %cl # cl = (StartLBA % MaxSector) + 1 = Sector
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xorw %dx, %dx # dx = 0
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divw 2(%bp) # ax = ax / (MaxHead + 1) = Cylinder
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# dx = ax % (MaxHead + 1) = Head
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pushw %bx # Save number of blocks to transfer
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movb %dl, %dh # dh = Head
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movw $0x7c00, %bp # bp = 0x7c00
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movb PhysicalDrive(%bp), %dl # dl = Drive Number
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movb %al, %ch # ch = Cylinder
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movb %bl, %al # al = Blocks
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movb $2, %ah # ah = Function 2
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movw %di, %bx # es:bx = Buffer address
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int $0x13
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jc DiskError
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popw %bx
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popw %cx
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movzwl %bx, %ebx
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addl %ebx, %esi # StartLBA = StartLBA + NumberOfBlocks
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subw %bx, %cx # Blocks = Blocks - NumberOfBlocks
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movw %es, %ax
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shlw $(BLOCK_SHIFT-4), %bx
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addw %bx, %ax
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movw %ax, %es # es:di = es:di + NumberOfBlocks*BLOCK_SIZE
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cmpw $0, %cx
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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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NotFoundAll:
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## if we found EFILDR, continue
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testw %bx, %bx
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jne FoundEFILDR
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BadBootSector:
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DiskError:
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movw $ErrorString, %si
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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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.byte 'B', 0x0c, 'S', 0x0c, 't', 0x0c, 'a', 0x0c, 'r', 0x0c, 't', 0x0c, '!', 0x0c
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ErrorString:
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.byte 'B', 0x0c, 'E', 0x0c, 'r', 0x0c, 'r', 0x0c, 'o', 0x0c, 'r', 0x0c, '!', 0x0c
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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 0x01fa # Comment it for pass build. Should optimise code size.
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LBAOffsetForBootSector:
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.long 0x0
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# ****************************************************************************
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# Sector Signature
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# ****************************************************************************
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# .org 0x01fe # Comment it for pass build.
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SectorSignature:
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.word 0xaa55 # Boot Sector Signature
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