| #------------------------------------------------------------------------------
|
| #*
|
| #* Copyright 2006 - 2007, Intel Corporation
|
| #* All rights reserved. This program and the accompanying materials
|
| #* are licensed and made available under the terms and conditions of the BSD License
|
| #* which accompanies this distribution. The full text of the license may be found at
|
| #* http://opensource.org/licenses/bsd-license.php
|
| #*
|
| #* THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
|
| #* WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
|
| #*
|
| #* bs32.asm
|
| #*
|
| #* Abstract:
|
| #*
|
| #------------------------------------------------------------------------------
|
|
|
| #.MODEL small
|
| .stack:
|
| .486p:
|
| .code16
|
|
|
| .equ FAT_DIRECTORY_ENTRY_SIZE, 0x0020
|
| .equ FAT_DIRECTORY_ENTRY_SHIFT, 5
|
| .equ BLOCK_SIZE, 0x0200
|
| .equ BLOCK_MASK, 0x01ff
|
| .equ BLOCK_SHIFT, 9
|
| # "EFILDR_____"
|
| .equ LOADER_FILENAME_PART1, 0x4c494645 # "EFIL"
|
| .equ LOADER_FILENAME_PART2, 0x30325244 # "DR20"
|
| .equ LOADER_FILENAME_PART3, 0x20202030 # "0___"
|
|
|
| .org 0x0 |
| .global _start |
| _start:
|
| Ia32Jump:
|
| jmp BootSectorEntryPoint # JMP inst - 3 bytes
|
| nop
|
|
|
| OemId: .ascii "INTEL " # OemId - 8 bytes
|
| # BPB data below will be fixed by tool
|
| SectorSize: .word 0 # Sector Size - 16 bits
|
| SectorsPerCluster: .byte 0 # Sector Per Cluster - 8 bits
|
| ReservedSectors: .word 0 # Reserved Sectors - 16 bits
|
| NoFats: .byte 0 # Number of FATs - 8 bits
|
| RootEntries: .word 0 # Root Entries - 16 bits
|
| Sectors: .word 0 # Number of Sectors - 16 bits
|
| Media: .byte 0 # Media - 8 bits - ignored
|
| SectorsPerFat: .word 0 # Sectors Per FAT - 16 bits
|
| SectorsPerTrack: .word 0 # Sectors Per Track - 16 bits - ignored
|
| Heads: .word 0 # Heads - 16 bits - ignored
|
| HiddenSectors: .long 0 # Hidden Sectors - 32 bits - ignored
|
| LargeSectors: .long 0 # Large Sectors - 32 bits
|
|
|
| #******************************************************************************
|
| #
|
| #The structure for FAT32 starting at offset 36 of the boot sector. (At this point,
|
| #the BPB/boot sector for FAT12 and FAT16 differs from the BPB/boot sector for FAT32.)
|
| #
|
| #******************************************************************************
|
|
|
| SectorsPerFat32: .long 0 # Sectors Per FAT for FAT32 - 4 bytes
|
| ExtFlags: .word 0 # Mirror Flag - 2 bytes
|
| FSVersion: .word 0 # File System Version - 2 bytes
|
| RootCluster: .long 0 # 1st Cluster Number of Root Dir - 4 bytes
|
| FSInfo: .word 0 # Sector Number of FSINFO - 2 bytes
|
| BkBootSector: .word 0 # Sector Number of Bk BootSector - 2 bytes
|
| Reserved: .fill 12, 1, 0 # Reserved Field - 12 bytes
|
| PhysicalDrive: .byte 0 # Physical Drive Number - 1 byte
|
| Reserved1: .byte 0 # Reserved Field - 1 byte
|
| Signature: .byte 0 # Extended Boot Signature - 1 byte
|
| VolId: .ascii " " # Volume Serial Number - 4 bytes
|
| FatLabel: .ascii " " # Volume Label - 11 bytes
|
| FileSystemType: .ascii "FAT32 " # File System Type - 8 bytes
|
| BootSectorEntryPoint:
|
| #ASSUME ds:@code
|
| #ASSUME ss:@code
|
|
|
| # ****************************************************************************
|
| # Start Print
|
| # ****************************************************************************
|
| movw $StartString, %si
|
| call PrintString
|
|
|
| # ****************************************************************************
|
| # Print over
|
| # ****************************************************************************
|
|
|
| movw %cs, %ax # ax = 0
|
| movw %ax, %ss # ss = 0
|
| addw $0x1000, %ax
|
| movw %ax, %ds
|
|
|
| movw $0x7c00, %sp # sp = 0x7c00
|
| movw %sp, %bp # bp = 0x7c00
|
|
|
| movb $8, %ah # ah = 8 - Get Drive Parameters Function
|
| movb %dl, PhysicalDrive(%bp) # BBS defines that BIOS would pass the booting driver number to the loader through DL
|
| int $0x13 # Get Drive Parameters
|
| xorw %ax, %ax # ax = 0
|
| movb %dh, %al # al = dh
|
| incb %al # MaxHead = al + 1
|
| pushw %ax # 0000:7bfe = MaxHead
|
| movb %cl, %al # al = cl
|
| andb $0x3f, %al # MaxSector = al & 0x3f
|
| pushw %ax # 0000:7bfc = MaxSector
|
|
|
| cmpw $0xaa55, SectorSignature(%bp) # Verify Boot Sector Signature
|
| jne BadBootSector
|
| movw RootEntries(%bp), %cx # cx = RootEntries
|
| shlw $FAT_DIRECTORY_ENTRY_SHIFT, %cx # cx = cx * 32 = cx * sizeof(FAT_DIRECTORY_ENTRY) = Size of Root Directory in bytes
|
| movw %cx, %bx # bx = size of the Root Directory in bytes
|
| andw $BLOCK_MASK, %bx # See if it is an even number of sectors long
|
| jne BadBootSector # If is isn't, then the boot sector is bad.
|
| movw %cx, %bx # bx = size of the Root Directory in bytes
|
| shrw $BLOCK_SHIFT, %bx # bx = size of Root Directory in sectors
|
| movb NoFats(%bp), %al # al = NoFats
|
| xorb %ah, %ah # ah = 0 ==> ax = NoFats
|
| mulw SectorsPerFat32(%bp) # ax = NoFats * SectorsPerFat
|
| addw ReservedSectors(%bp), %ax # ax = NoFats * SectorsPerFat + ReservedSectors = RootLBA
|
| addw %bx, %ax # ax = NoFats * SectorsPerFat + ReservedSectors + RootDirSectors = FirstClusterLBA
|
| movw %ax, (%bp) # Save FirstClusterLBA for later use
|
|
|
| movw RootCluster(%bp), %ax # ax = StartCluster of Root Directory
|
| subw $2, %ax # ax = StartCluster - 2
|
| xorb %bh, %bh
|
| movb SectorsPerCluster(%bp), %bl # bx = SectorsPerCluster
|
| mulw %bx # ax = (StartCluster - 2) * SectorsPerCluster
|
| addw (%bp), %ax # ax = FirstClusterLBA + (StartCluster-2)*SectorsPerCluster
|
| pushw %ds
|
| popw %es
|
| xorw %di, %di # Store directory in es:di = 1000:0000
|
| call ReadBlocks # Read StartCluster of Root Directory
|
|
|
| # dx - variable storage (initial value is 0)
|
| # bx - loader (initial value is 0)
|
| xorw %dx, %dx
|
| xorw %bx, %bx
|
|
|
| FindEFILDR:
|
| cmpl $LOADER_FILENAME_PART1, (%di)
|
| jne FindVARSTORE
|
| cmpl $LOADER_FILENAME_PART2, 4(%di)
|
| jne FindVARSTORE
|
| cmpl $LOADER_FILENAME_PART3, 7(%di)
|
| jne FindVARSTORE
|
| movw 26(%di), %bx # bx = Start Cluster for EFILDR <----------------------------------
|
| testw %dx, %dx
|
| je FindNext # Efivar.bin is not loaded
|
| jmp FoundAll
|
|
|
| FindVARSTORE:
|
| ## if the file is not loader file, see if it's "EFIVAR BIN"
|
| cmpl $0x56494645, (%di) # Compare to "EFIV"
|
| jne FindNext
|
| cmpl $0x20205241, 4(%di) # Compare to "AR "
|
| jne FindNext
|
| cmpl $0x4e494220, 7(%di) # Compare to " BIN"
|
| jne FindNext
|
| movw %di, %dx # dx = Offset of Start Cluster for Efivar.bin <---------------------
|
| addw $26, %dx
|
| testw %bx, %bx
|
| je FindNext # Efildr is not loaded
|
| jmp FoundAll
|
|
|
| FindNext:
|
| # go to next find
|
| addw $FAT_DIRECTORY_ENTRY_SIZE, %di # Increment di
|
| subw $FAT_DIRECTORY_ENTRY_SIZE, %cx # Decrement cx
|
| # TODO: jump to FindVarStore if ...
|
| jne FindEFILDR
|
| jmp NotFoundAll
|
|
|
| FoundAll:
|
| FoundEFILDR:
|
| movw %bx, %cx # cx = Start Cluster for EFILDR <----------------------------------
|
| movw %cs, %ax # Destination = 2000:0000
|
| addw $0x2000, %ax
|
| movw %ax, %es
|
| xorw %di, %di
|
| ReadFirstClusterOfEFILDR:
|
| movw %cx, %ax # ax = StartCluster
|
| subw $2, %ax # ax = StartCluster - 2
|
| xorb %bh, %bh
|
| movb SectorsPerCluster(%bp), %bl # bx = SectorsPerCluster
|
| pushw %dx
|
| mulw %bx
|
| popw %dx # ax = (StartCluster - 2) * SectorsPerCluster
|
| addw (%bp), %ax # ax = FirstClusterLBA + (StartCluster-2)*SectorsPerCluster
|
| xorb %bh, %bh
|
| movb SectorsPerCluster(%bp), %bl # bx = Number of Sectors in a cluster
|
| pushw %es
|
| call ReadBlocks
|
| popw %ax
|
| JumpIntoFirstSectorOfEFILDR:
|
| movw %ax, JumpSegment(%bp)
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| JumpFarInstruction:
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| .byte 0xea
|
| JumpOffset:
|
| .word 0x000
|
| JumpSegment:
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| .word 0x2000
|
|
|
|
|
| PrintString:
|
| movw $0xb800, %ax
|
| movw %ax, %es
|
| movw $0x7c0, %ax
|
| movw %ax, %ds
|
| movw $7, %cx
|
| movw $160, %di
|
| rep
|
| movsw
|
| ret
|
| # ****************************************************************************
|
| # ReadBlocks - Reads a set of blocks from a block device
|
| #
|
| # AX = Start LBA
|
| # BX = Number of Blocks to Read
|
| # ES:DI = Buffer to store sectors read from disk
|
| # ****************************************************************************
|
|
|
| # cx = Blocks
|
| # bx = NumberOfBlocks
|
| # si = StartLBA
|
|
|
| ReadBlocks:
|
| pusha
|
| addl LBAOffsetForBootSector(%bp), %eax # Add LBAOffsetForBootSector to Start LBA
|
| addl HiddenSectors(%bp), %eax # Add HiddenSectors to Start LBA
|
| movl %eax, %esi # esi = Start LBA
|
| movw %bx, %cx # cx = Number of blocks to read
|
| ReadCylinderLoop:
|
| movw $0x7bfc, %bp # bp = 0x7bfc
|
| movl %esi, %eax # eax = Start LBA
|
| xorl %edx, %edx # edx = 0
|
| movzwl (%bp), %ebx # bx = MaxSector
|
| divl %ebx # ax = StartLBA / MaxSector
|
| incw %dx # dx = (StartLBA % MaxSector) + 1
|
| subw %dx, %bx # bx = MaxSector - Sector
|
| incw %bx # bx = MaxSector - Sector + 1
|
| cmpw %bx, %cx # Compare (Blocks) to (MaxSector - Sector + 1)
|
| jg LimitTransfer
|
| movw %cx, %bx # bx = Blocks
|
| LimitTransfer:
|
| pushw %cx
|
| movb %dl, %cl # cl = (StartLBA % MaxSector) + 1 = Sector
|
| xorw %dx, %dx # dx = 0
|
| divw 2(%bp) # ax = ax / (MaxHead + 1) = Cylinder
|
| # dx = ax % (MaxHead + 1) = Head
|
|
|
| pushw %bx # Save number of blocks to transfer
|
| movb %dl, %dh # dh = Head
|
| movw $0x7c00, %bp # bp = 0x7c00
|
| movb PhysicalDrive(%bp), %dl # dl = Drive Number
|
| movb %al, %ch # ch = Cylinder
|
| movb %bl, %al # al = Blocks
|
| movb $2, %ah # ah = Function 2
|
| movw %di, %bx # es:bx = Buffer address
|
| int $0x13
|
| jc DiskError
|
| popw %bx
|
| popw %cx
|
| movzwl %bx, %ebx
|
| addl %ebx, %esi # StartLBA = StartLBA + NumberOfBlocks
|
| subw %bx, %cx # Blocks = Blocks - NumberOfBlocks
|
| movw %es, %ax
|
| shlw $(BLOCK_SHIFT-4), %bx
|
| addw %bx, %ax
|
| movw %ax, %es # es:di = es:di + NumberOfBlocks*BLOCK_SIZE
|
| cmpw $0, %cx
|
| jne ReadCylinderLoop
|
| popa
|
| ret
|
|
|
| # ****************************************************************************
|
| # ERROR Condition:
|
| # ****************************************************************************
|
| NotFoundAll:
|
| ## if we found EFILDR, continue
|
| testw %bx, %bx
|
| jne FoundEFILDR
|
| BadBootSector:
|
| DiskError:
|
| movw $ErrorString, %si
|
| call PrintString
|
| Halt:
|
| jmp Halt
|
|
|
| StartString:
|
| .byte 'B', 0x0c, 'S', 0x0c, 't', 0x0c, 'a', 0x0c, 'r', 0x0c, 't', 0x0c, '!', 0x0c
|
| ErrorString:
|
| .byte 'B', 0x0c, 'E', 0x0c, 'r', 0x0c, 'r', 0x0c, 'o', 0x0c, 'r', 0x0c, '!', 0x0c
|
|
|
| # ****************************************************************************
|
| # LBA Offset for BootSector, need patched by tool for HD boot.
|
| # ****************************************************************************
|
|
|
| #.org 0x01fa
|
| LBAOffsetForBootSector:
|
| .long 0x0
|
|
|
| # ****************************************************************************
|
| # Sector Signature
|
| # ****************************************************************************
|
|
|
| #.org 0x01fe
|
| SectorSignature:
|
| .word 0xaa55 # Boot Sector Signature
|
|
|
|
|
|
|