1#------------------------------------------------------------------------------
2#*
3#*   Copyright (c) 2006 - 2011, Intel Corporation. All rights reserved.<BR>
4#*   This program and the accompanying materials
5#*   are licensed and made available under the terms and conditions of the BSD License
6#*   which accompanies this distribution.  The full text of the license may be found at
7#*   http://opensource.org/licenses/bsd-license.php
8#*
9#*   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
10#*   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
11#*
12#*    gpt.asm
13#*
14#*   Abstract:
15#*
16#------------------------------------------------------------------------------
17
18    #.MODEL small
19#   .dosseg
20    .stack:
21    .486p:
22    .code16
23
24.equ                      BLOCK_SIZE,  0x0200
25.equ                      BLOCK_MASK,  0x01ff
26.equ                      BLOCK_SHIFT, 9
27
28# ****************************************************************************
29# Code loaded by BIOS at 0x0000:0x7C00
30# ****************************************************************************
31
32        .org 0x00
33Start:
34
35# ****************************************************************************
36# Start Print
37# ****************************************************************************
38
39    movw $0xb800, %ax
40    movw %ax, %es
41    movw $0x7c0, %ax
42    movw %ax, %ds
43    leaw %cs:StartString, %si
44    movw $10, %cx
45    movw $160, %di
46    rep
47    movsw
48
49# ****************************************************************************
50# Print over
51# ****************************************************************************
52
53# ****************************************************************************
54# Initialize segment registers and copy code at 0x0000:0x7c00 to 0x0000:0x0600
55# ****************************************************************************
56        xorw  %ax, %ax                  # AX = 0x0000
57        movw  $0x7c00, %bx              # BX = 0x7C00
58        movw  $0x600, %bp               # BP = 0x0600
59        movw  RelocatedStart, %si       # SI = Offset(RelocatedStart)
60        movw  $0x200, %cx               # CX = 0x0200
61        subw  %si, %cx                  # CS = 0x0200 - Offset(RelocatedStart)
62        leaw  (%bp,%si,), %di           # DI = 0x0600 + Offset(RelocatedStart)
63        leaw  (%bx,%si,), %si           # BX = 0x7C00 + Offset(RelocatedStart)
64        movw  %ax, %ss                  # SS = 0x0000
65        movw  %bx, %sp                  # SP = 0x7C00
66        movw  %ax, %es                  # ES = 0x0000
67        movw  %ax, %ds                  # DS = 0x0000
68        pushw %ax                       # PUSH 0x0000
69        pushw %di                       # PUSH 0x0600 + Offset(RelocatedStart)
70        cld                             # Clear the direction flag
71        rep
72        movsb                           # Copy 0x0200 bytes from 0x7C00 to 0x0600
73        retl                            # JMP 0x0000:0x0600 + Offset(RelocatedStart)
74
75# ****************************************************************************
76# Code relocated to 0x0000:0x0600
77# ****************************************************************************
78
79RelocatedStart:
80# ****************************************************************************
81# Get Driver Parameters to 0x0000:0x7BFC
82# ****************************************************************************
83        xorw  %ax, %ax      # ax = 0
84        movw  %ax, %ss      # ss = 0
85        addw  $0x1000, %ax
86        movw  %ax, %ds
87
88        movw  $0x7c00, %sp  # sp = 0x7c00
89        movw  %sp, %bp      # bp = 0x7c00
90
91        movb  $8, %ah                             # ah = 8 - Get Drive Parameters Function
92        movb  %dl, PhysicalDrive(%bp)             # BBS defines that BIOS would pass the booting driver number to the loader through DL
93        int   $0x13                               # Get Drive Parameters
94        xorw  %ax, %ax                # ax = 0
95        movb  %dh, %al                # al = dh
96        incb  %al                     # MaxHead = al + 1
97        pushw %ax                     # 0000:7bfe = MaxHead
98        movb  %cl, %al                # al = cl
99        andb  $0x3f, %al              # MaxSector = al & 0x3f
100        pushw %ax                     # 0000:7bfc = MaxSector
101
102# ****************************************************************************
103# Read GPT Header from hard disk to 0x0000:0x0800
104# ****************************************************************************
105        xorw    %ax, %ax
106        movw    %ax, %es                          # Read to 0x0000:0x0800
107        movw    $0x800, %di                       # Read to 0x0000:0x0800
108        movl    $1, %eax                          # Read LBA #1
109        movl    $0, %edx                          # Read LBA #1
110        movw    $1, %bx                           # Read 1 Block
111        pushw   %es
112        call    ReadBlocks
113        popw    %es
114
115# ****************************************************************************
116# Read Target GPT Entry from hard disk to 0x0000:0x0A00
117# ****************************************************************************
118        cmpl  $0x20494645, %es:(%di)              # Check for "EFI "
119        jne   BadGpt
120        cmpl  $0x54524150, %es:4(%di)             # Check for "PART"
121        jne   BadGpt
122        cmpl  $0x00010000, %es:8(%di)             # Check Revision - 0x10000
123        jne   BadGpt
124
125        movl  %es:84(%di), %eax                   # EAX = SizeOfPartitionEntry
126        mulb  GptPartitionIndicator(%bp)          # EAX = SizeOfPartitionEntry * GptPartitionIndicator
127        movl  %eax, %edx                          # EDX = SizeOfPartitionEntry * GptPartitionIndicator
128        shrl  $BLOCK_SHIFT, %eax                  # EAX = (SizeOfPartitionEntry * GptPartitionIndicator) / BLOCK_SIZE
129        andl  $BLOCK_MASK, %edx                   # EDX = Targer PartitionEntryLBA Offset
130                                                  #     = (SizeOfPartitionEntry * GptPartitionIndicator) % BLOCK_SIZE
131        pushl %edx
132        movl  %es:72(%di), %ecx                   # ECX = PartitionEntryLBA (Low)
133        movl  %es:76(%di), %ebx                   # EBX = PartitionEntryLBA (High)
134        addl  %ecx, %eax                          # EAX = Target PartitionEntryLBA (Low)
135                                                  #     = (PartitionEntryLBA +
136                                                  #        (SizeOfPartitionEntry * GptPartitionIndicator) / BLOCK_SIZE)
137        adcl  %ebx, %edx                          # EDX = Target PartitionEntryLBA (High)
138
139        movw  $0xA00, %di                         # Read to 0x0000:0x0A00
140        movw  $1, %bx                             # Read 1 Block
141        pushw %es
142        call  ReadBlocks
143        popw  %es
144
145# ****************************************************************************
146# Read Target DBR from hard disk to 0x0000:0x7C00
147# ****************************************************************************
148        popl  %edx                                # EDX = (SizeOfPartitionEntry * GptPartitionIndicator) % BLOCK_SIZE
149        addw  %dx, %di                            # DI = Targer PartitionEntryLBA Offset
150        cmpl  $0xC12A7328, %es:(%di)              # Check for EFI System Partition "C12A7328-F81F-11d2-BA4B-00A0C93EC93B"
151        jne   BadGpt
152        cmpl  $0x11d2F81F, %es:4(%di)             #
153        jne   BadGpt
154        cmpl  $0xA0004BBA, %es:8(%di)             #
155        jne   BadGpt
156        cmpl  $0x3BC93EC9, %es:0xc(%di)           #
157        jne   BadGpt
158
159        movl  %es:32(%di), %eax                   # EAX = StartingLBA (Low)
160        movl  %es:36(%di), %edx                   # EDX = StartingLBA (High)
161        movw  $0x7C00, %di                        # Read to 0x0000:0x7C00
162        movw  $1, %bx                             # Read 1 Block
163        call  ReadBlocks
164
165# ****************************************************************************
166# Transfer control to BootSector - Jump to 0x0000:0x7C00
167# ****************************************************************************
168        xorw  %ax, %ax
169        pushw %ax                       # PUSH 0x0000
170        movw  $0x7c00, %di
171        pushw %di                       # PUSH 0x7C00
172        retl                            # JMP 0x0000:0x7C00
173
174# ****************************************************************************
175# ReadBlocks - Reads a set of blocks from a block device
176#
177# EDX:EAX = Start LBA
178# BX      = Number of Blocks to Read (must < 127)
179# ES:DI   = Buffer to store sectors read from disk
180# ****************************************************************************
181
182# si = DiskAddressPacket
183
184ReadBlocks:
185        pushal
186        pushw %ds
187        xorw  %cx, %cx
188        movw  %cx, %ds
189        movw  $0x600, %bp                       # bp = 0x600
190        leaw  AddressPacket(%bp), %si
191        movb  %bl, %ds:2(%si)                   #    02 = Number Of Block transfered
192        movw  %di, %ds:4(%si)                   #    04 = Transfer Buffer Offset
193        movw  %es, %ds:6(%si)                   #    06 = Transfer Buffer Segment
194        movl  %eax, %ds:8(%si)                  #    08 = Starting LBA (Low)
195        movl  %edx, %ds:0xc(%si)                #    0C = Starting LBA (High)
196        movb  $0x42, %ah                        # ah = Function 42
197        movb  PhysicalDrive(%bp), %dl           # dl = Drive Number
198        int   $0x13
199        jc    BadGpt
200        popw  %ds
201        popal
202        ret
203
204# ****************************************************************************
205# Address Packet used by ReadBlocks
206# ****************************************************************************
207AddressPacket:
208        .byte 0x10                      # Size of address packet
209        .byte 0x0                       # Reserved.  Must be 0
210        .byte 0x1                       # Read blocks at a time (To be fixed each times)
211        .byte 0x0                       # Reserved.  Must be 0
212        .word 0x000                     # Destination Address offset (To be fixed each times)
213        .word 0x000                     # Destination Address segment (To be fixed each times)
214AddressPacketLba:
215        .long 0x0,0x0                   # Start LBA (To be fixed each times)
216AddressPacketEnd:
217
218# ****************************************************************************
219# ERROR Condition:
220# ****************************************************************************
221
222BadGpt:
223    movw $0xb800, %ax
224    movw %ax, %es
225    movw $0x60, %ax
226    movw %ax, %ds
227    leaw %cs:ErrorString, %si
228    movw $10, %cx
229    movw $320, %di
230    rep
231    movsw
232Halt:
233    jmp   Halt
234
235StartString:
236    .byte 'G', 0x0c, 'P', 0x0c, 'T', 0x0c, ' ', 0x0c, 'S', 0x0c, 't', 0x0c, 'a', 0x0c, 'r', 0x0c, 't', 0x0c, '!', 0x0c
237ErrorString:
238    .byte 'G', 0x0c, 'P', 0x0c, 'T', 0x0c, ' ', 0x0c, 'E', 0x0c, 'r', 0x0c, 'r', 0x0c, 'o', 0x0c, 'r', 0x0c, '!', 0x0c
239
240# ****************************************************************************
241# PhysicalDrive - Used to indicate which disk to be boot
242#                 Can be patched by tool
243# ****************************************************************************
244    # .org   0x01B6 # Just for passing build.
245PhysicalDrive:        .byte 0x80
246
247# ****************************************************************************
248# GptPartitionIndicator - Used to indicate which GPT partition to be boot
249#                         Can be patched by tool
250# ****************************************************************************
251   # .org   0x01B7  # Just for passing build.
252GptPartitionIndicator: .byte 0
253
254# ****************************************************************************
255# Unique MBR signature
256# ****************************************************************************
257   # .org   0x01B8  # Just for passing build.
258    .ascii "DUET"
259
260# ****************************************************************************
261# Unknown
262# ****************************************************************************
263    # .org   0x01BC  # Just for passing build.
264    .word 0
265
266# ****************************************************************************
267# PMBR Entry - Can be patched by tool
268# ****************************************************************************
269    # .org   0x01BE  # Just for passing build.
270    .byte 0       # Boot Indicator
271    .byte 0xff    # Start Header
272    .byte 0xff    # Start Sector
273    .byte 0xff    # Start Track
274    .byte 0xee    # OS Type
275    .byte 0xff    # End Header
276    .byte 0xff    # End Sector
277    .byte 0xff    # End Track
278    .long 1       # Starting LBA
279    .long 0xFFFFFFFF # End LBA
280
281    # .org   0x01CE  # Just for passing build.
282    .long  0,0,0,0
283    # .org   0x01DE  # Just for passing build.
284    .long  0,0,0,0
285    # .org   0x01EE  # Just for passing build.
286    .long 0,0,0,0
287
288# ****************************************************************************
289# Sector Signature
290# ****************************************************************************
291
292  # .org      0x01FE  # Just for passing build.
293SectorSignature:
294  .word     0xaa55      # Boot Sector Signature
295
296
297
298