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;------------------------------------------------------------------------------
;*
;* 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.
;*
;* gpt.asm
;*
;* Abstract:
;*
;------------------------------------------------------------------------------
.model small
; .dosseg
.stack
.486p
.code
BLOCK_SIZE EQU 0200h
BLOCK_MASK EQU 01ffh
BLOCK_SHIFT EQU 9
; ****************************************************************************
; Code loaded by BIOS at 0x0000:0x7C00
; ****************************************************************************
org 0h
Start:
; ****************************************************************************
; Start Print
; ****************************************************************************
mov ax,0b800h
mov es,ax
mov ax, 07c0h
mov ds, ax
lea si, cs:[StartString]
mov cx, 10
mov di, 160
rep movsw
; ****************************************************************************
; Print over
; ****************************************************************************
; ****************************************************************************
; Initialize segment registers and copy code at 0x0000:0x7c00 to 0x0000:0x0600
; ****************************************************************************
xor ax, ax ; AX = 0x0000
mov bx, 07c00h ; BX = 0x7C00
mov bp, 0600h ; BP = 0x0600
mov si, OFFSET RelocatedStart ; SI = Offset(RelocatedStart)
mov cx, 0200h ; CX = 0x0200
sub cx, si ; CS = 0x0200 - Offset(RelocatedStart)
lea di, [bp+si] ; DI = 0x0600 + Offset(RelocatedStart)
lea si, [bx+si] ; BX = 0x7C00 + Offset(RelocatedStart)
mov ss, ax ; SS = 0x0000
mov sp, bx ; SP = 0x7C00
mov es,ax ; ES = 0x0000
mov ds,ax ; DS = 0x0000
push ax ; PUSH 0x0000
push di ; PUSH 0x0600 + Offset(RelocatedStart)
cld ; Clear the direction flag
rep movsb ; Copy 0x0200 bytes from 0x7C00 to 0x0600
retf ; JMP 0x0000:0x0600 + Offset(RelocatedStart)
; ****************************************************************************
; Code relocated to 0x0000:0x0600
; ****************************************************************************
RelocatedStart:
; ****************************************************************************
; Get Driver Parameters to 0x0000:0x7BFC
; ****************************************************************************
xor ax,ax ; ax = 0
mov ss,ax ; ss = 0
add ax,1000h
mov ds,ax
mov sp,07c00h ; sp = 0x7c00
mov bp,sp ; bp = 0x7c00
mov ah,8 ; ah = 8 - Get Drive Parameters Function
mov byte ptr [bp+PhysicalDrive],dl ; BBS defines that BIOS would pass the booting driver number to the loader through DL
int 13h ; Get Drive Parameters
xor ax,ax ; ax = 0
mov al,dh ; al = dh
inc al ; MaxHead = al + 1
push ax ; 0000:7bfe = MaxHead
mov al,cl ; al = cl
and al,03fh ; MaxSector = al & 0x3f
push ax ; 0000:7bfc = MaxSector
; ****************************************************************************
; Read GPT Header from hard disk to 0x0000:0x0800
; ****************************************************************************
xor ax, ax
mov es, ax ; Read to 0x0000:0x0800
mov di, 0800h ; Read to 0x0000:0x0800
mov eax, 1 ; Read LBA #1
mov edx, 0 ; Read LBA #1
mov bx, 1 ; Read 1 Block
push es
call ReadBlocks
pop es
; ****************************************************************************
; Read Target GPT Entry from hard disk to 0x0000:0x0A00
; ****************************************************************************
cmp dword ptr es:[di], 020494645h ; Check for "EFI "
jne BadGpt
cmp dword ptr es:[di + 4], 054524150h ; Check for "PART"
jne BadGpt
cmp dword ptr es:[di + 8], 000010000h ; Check Revision - 0x10000
jne BadGpt
mov eax, dword ptr es:[di + 84] ; EAX = SizeOfPartitionEntry
mul byte ptr [bp+GptPartitionIndicator] ; EAX = SizeOfPartitionEntry * GptPartitionIndicator
mov edx, eax ; EDX = SizeOfPartitionEntry * GptPartitionIndicator
shr eax, BLOCK_SHIFT ; EAX = (SizeOfPartitionEntry * GptPartitionIndicator) / BLOCK_SIZE
and edx, BLOCK_MASK ; EDX = Targer PartitionEntryLBA Offset
; = (SizeOfPartitionEntry * GptPartitionIndicator) % BLOCK_SIZE
push edx
mov ecx, dword ptr es:[di + 72] ; ECX = PartitionEntryLBA (Low)
mov ebx, dword ptr es:[di + 76] ; EBX = PartitionEntryLBA (High)
add eax, ecx ; EAX = Target PartitionEntryLBA (Low)
; = (PartitionEntryLBA +
; (SizeOfPartitionEntry * GptPartitionIndicator) / BLOCK_SIZE)
adc edx, ebx ; EDX = Target PartitionEntryLBA (High)
mov di, 0A00h ; Read to 0x0000:0x0A00
mov bx, 1 ; Read 1 Block
push es
call ReadBlocks
pop es
; ****************************************************************************
; Read Target DBR from hard disk to 0x0000:0x7C00
; ****************************************************************************
pop edx ; EDX = (SizeOfPartitionEntry * GptPartitionIndicator) % BLOCK_SIZE
add di, dx ; DI = Targer PartitionEntryLBA Offset
cmp dword ptr es:[di], 0C12A7328h ; Check for EFI System Partition "C12A7328-F81F-11d2-BA4B-00A0C93EC93B"
jne BadGpt
cmp dword ptr es:[di + 4], 011d2F81Fh ;
jne BadGpt
cmp dword ptr es:[di + 8], 0A0004BBAh ;
jne BadGpt
cmp dword ptr es:[di + 0ch], 03BC93EC9h ;
jne BadGpt
mov eax, dword ptr es:[di + 32] ; EAX = StartingLBA (Low)
mov edx, dword ptr es:[di + 36] ; EDX = StartingLBA (High)
mov di, 07C00h ; Read to 0x0000:0x7C00
mov bx, 1 ; Read 1 Block
call ReadBlocks
; ****************************************************************************
; Transfer control to BootSector - Jump to 0x0000:0x7C00
; ****************************************************************************
xor ax, ax
push ax ; PUSH 0x0000
mov di, 07c00h
push di ; PUSH 0x7C00
retf ; JMP 0x0000:0x7C00
; ****************************************************************************
; ReadBlocks - Reads a set of blocks from a block device
;
; EDX:EAX = Start LBA
; BX = Number of Blocks to Read (must < 127)
; ES:DI = Buffer to store sectors read from disk
; ****************************************************************************
; si = DiskAddressPacket
ReadBlocks:
pushad
push ds
xor cx, cx
mov ds, cx
mov bp, 0600h ; bp = 0x600
lea si, [bp + OFFSET AddressPacket] ; DS:SI = Disk Address Packet
mov BYTE PTR ds:[si+2],bl ; 02 = Number Of Block transfered
mov WORD PTR ds:[si+4],di ; 04 = Transfer Buffer Offset
mov WORD PTR ds:[si+6],es ; 06 = Transfer Buffer Segment
mov DWORD PTR ds:[si+8],eax ; 08 = Starting LBA (Low)
mov DWORD PTR ds:[si+0ch],edx ; 0C = Starting LBA (High)
mov ah, 42h ; ah = Function 42
mov dl,byte ptr [bp+PhysicalDrive] ; dl = Drive Number
int 13h
jc BadGpt
pop ds
popad
ret
; ****************************************************************************
; Address Packet used by ReadBlocks
; ****************************************************************************
AddressPacket:
db 10h ; Size of address packet
db 00h ; Reserved. Must be 0
db 01h ; Read blocks at a time (To be fixed each times)
db 00h ; Reserved. Must be 0
dw 0000h ; Destination Address offset (To be fixed each times)
dw 0000h ; Destination Address segment (To be fixed each times)
AddressPacketLba:
dd 0h, 0h ; Start LBA (To be fixed each times)
AddressPacketEnd:
; ****************************************************************************
; ERROR Condition:
; ****************************************************************************
BadGpt:
mov ax,0b800h
mov es,ax
mov ax, 060h
mov ds, ax
lea si, cs:[ErrorString]
mov cx, 10
mov di, 320
rep movsw
Halt:
jmp Halt
StartString:
db 'G', 0ch, 'P', 0ch, 'T', 0ch, ' ', 0ch, 'S', 0ch, 't', 0ch, 'a', 0ch, 'r', 0ch, 't', 0ch, '!', 0ch
ErrorString:
db 'G', 0ch, 'P', 0ch, 'T', 0ch, ' ', 0ch, 'E', 0ch, 'r', 0ch, 'r', 0ch, 'o', 0ch, 'r', 0ch, '!', 0ch
; ****************************************************************************
; PhysicalDrive - Used to indicate which disk to be boot
; Can be patched by tool
; ****************************************************************************
org 01B6h
PhysicalDrive db 80h
; ****************************************************************************
; GptPartitionIndicator - Used to indicate which GPT partition to be boot
; Can be patched by tool
; ****************************************************************************
org 01B7h
GptPartitionIndicator db 0
; ****************************************************************************
; Unique MBR signature
; ****************************************************************************
org 01B8h
db 'DUET'
; ****************************************************************************
; Unknown
; ****************************************************************************
org 01BCh
dw 0
; ****************************************************************************
; PMBR Entry - Can be patched by tool
; ****************************************************************************
org 01BEh
db 0 ; Boot Indicator
db 0ffh ; Start Header
db 0ffh ; Start Sector
db 0ffh ; Start Track
db 0eeh ; OS Type
db 0ffh ; End Header
db 0ffh ; End Sector
db 0ffh ; End Track
dd 1 ; Starting LBA
dd 0FFFFFFFFh ; End LBA
org 01CEh
dd 0, 0, 0, 0
org 01DEh
dd 0, 0, 0, 0
org 01EEh
dd 0, 0, 0, 0
; ****************************************************************************
; Sector Signature
; ****************************************************************************
org 01FEh
SectorSignature:
dw 0aa55h ; Boot Sector Signature
end
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