1;------------------------------------------------------------------------------
2;*
3;*   Copyright (c) 2006 - 2007, 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    .code
23
24BLOCK_SIZE                EQU     0200h
25BLOCK_MASK                EQU     01ffh
26BLOCK_SHIFT               EQU     9
27
28; ****************************************************************************
29; Code loaded by BIOS at 0x0000:0x7C00
30; ****************************************************************************
31
32        org 0h
33Start:
34
35; ****************************************************************************
36; Start Print
37; ****************************************************************************
38
39    mov  ax,0b800h
40    mov  es,ax
41    mov  ax, 07c0h
42    mov  ds, ax
43    lea  si, cs:[StartString]
44    mov  cx, 10
45    mov  di, 160
46    rep  movsw
47
48; ****************************************************************************
49; Print over
50; ****************************************************************************
51
52; ****************************************************************************
53; Initialize segment registers and copy code at 0x0000:0x7c00 to 0x0000:0x0600
54; ****************************************************************************
55        xor   ax, ax                    ; AX = 0x0000
56        mov   bx, 07c00h                ; BX = 0x7C00
57        mov   bp, 0600h                 ; BP = 0x0600
58        mov   si, OFFSET RelocatedStart ; SI = Offset(RelocatedStart)
59        mov   cx, 0200h                 ; CX = 0x0200
60        sub   cx, si                    ; CS = 0x0200 - Offset(RelocatedStart)
61        lea   di, [bp+si]               ; DI = 0x0600 + Offset(RelocatedStart)
62        lea   si, [bx+si]               ; BX = 0x7C00 + Offset(RelocatedStart)
63        mov   ss, ax                    ; SS = 0x0000
64        mov   sp, bx                    ; SP = 0x7C00
65        mov   es,ax                     ; ES = 0x0000
66        mov   ds,ax                     ; DS = 0x0000
67        push  ax                        ; PUSH 0x0000
68        push  di                        ; PUSH 0x0600 + Offset(RelocatedStart)
69        cld                             ; Clear the direction flag
70        rep   movsb                     ; Copy 0x0200 bytes from 0x7C00 to 0x0600
71        retf                            ; JMP 0x0000:0x0600 + Offset(RelocatedStart)
72
73; ****************************************************************************
74; Code relocated to 0x0000:0x0600
75; ****************************************************************************
76
77RelocatedStart:
78; ****************************************************************************
79; Get Driver Parameters to 0x0000:0x7BFC
80; ****************************************************************************
81        xor   ax,ax         ; ax = 0
82        mov   ss,ax         ; ss = 0
83        add   ax,1000h
84        mov   ds,ax
85
86        mov   sp,07c00h     ; sp = 0x7c00
87        mov   bp,sp         ; bp = 0x7c00
88
89        mov   ah,8                                ; ah = 8 - Get Drive Parameters Function
90        mov   byte ptr [bp+PhysicalDrive],dl      ; BBS defines that BIOS would pass the booting driver number to the loader through DL
91        int   13h                                 ; Get Drive Parameters
92        xor   ax,ax                   ; ax = 0
93        mov   al,dh                   ; al = dh
94        inc   al                      ; MaxHead = al + 1
95        push  ax                      ; 0000:7bfe = MaxHead
96        mov   al,cl                   ; al = cl
97        and   al,03fh                 ; MaxSector = al & 0x3f
98        push  ax                      ; 0000:7bfc = MaxSector
99
100; ****************************************************************************
101; Read GPT Header from hard disk to 0x0000:0x0800
102; ****************************************************************************
103        xor     ax, ax
104        mov     es, ax                            ; Read to 0x0000:0x0800
105        mov     di, 0800h                         ; Read to 0x0000:0x0800
106        mov     eax, 1                            ; Read LBA #1
107        mov     edx, 0                            ; Read LBA #1
108        mov     bx, 1                             ; Read 1 Block
109        push    es
110        call    ReadBlocks
111        pop     es
112
113; ****************************************************************************
114; Read Target GPT Entry from hard disk to 0x0000:0x0A00
115; ****************************************************************************
116        cmp   dword ptr es:[di], 020494645h       ; Check for "EFI "
117        jne   BadGpt
118        cmp   dword ptr es:[di + 4], 054524150h   ; Check for "PART"
119        jne   BadGpt
120        cmp   dword ptr es:[di + 8], 000010000h   ; Check Revision - 0x10000
121        jne   BadGpt
122
123        mov   eax, dword ptr es:[di + 84]         ; EAX = SizeOfPartitionEntry
124        mul   byte ptr [bp+GptPartitionIndicator] ; EAX = SizeOfPartitionEntry * GptPartitionIndicator
125        mov   edx, eax                            ; EDX = SizeOfPartitionEntry * GptPartitionIndicator
126        shr   eax, BLOCK_SHIFT                    ; EAX = (SizeOfPartitionEntry * GptPartitionIndicator) / BLOCK_SIZE
127        and   edx, BLOCK_MASK                     ; EDX = Targer PartitionEntryLBA Offset
128                                                  ;     = (SizeOfPartitionEntry * GptPartitionIndicator) % BLOCK_SIZE
129        push  edx
130        mov   ecx, dword ptr es:[di + 72]         ; ECX = PartitionEntryLBA (Low)
131        mov   ebx, dword ptr es:[di + 76]         ; EBX = PartitionEntryLBA (High)
132        add   eax, ecx                            ; EAX = Target PartitionEntryLBA (Low)
133                                                  ;     = (PartitionEntryLBA +
134                                                  ;        (SizeOfPartitionEntry * GptPartitionIndicator) / BLOCK_SIZE)
135        adc   edx, ebx                            ; EDX = Target PartitionEntryLBA (High)
136
137        mov   di, 0A00h                           ; Read to 0x0000:0x0A00
138        mov   bx, 1                               ; Read 1 Block
139        push  es
140        call  ReadBlocks
141        pop   es
142
143; ****************************************************************************
144; Read Target DBR from hard disk to 0x0000:0x7C00
145; ****************************************************************************
146        pop   edx                                 ; EDX = (SizeOfPartitionEntry * GptPartitionIndicator) % BLOCK_SIZE
147        add   di, dx                              ; DI = Targer PartitionEntryLBA Offset
148        cmp   dword ptr es:[di], 0C12A7328h       ; Check for EFI System Partition "C12A7328-F81F-11d2-BA4B-00A0C93EC93B"
149        jne   BadGpt
150        cmp   dword ptr es:[di + 4], 011d2F81Fh   ;
151        jne   BadGpt
152        cmp   dword ptr es:[di + 8], 0A0004BBAh   ;
153        jne   BadGpt
154        cmp   dword ptr es:[di + 0ch], 03BC93EC9h ;
155        jne   BadGpt
156
157        mov   eax, dword ptr es:[di + 32]         ; EAX = StartingLBA (Low)
158        mov   edx, dword ptr es:[di + 36]         ; EDX = StartingLBA (High)
159        mov   di, 07C00h                          ; Read to 0x0000:0x7C00
160        mov   bx, 1                               ; Read 1 Block
161        call  ReadBlocks
162
163; ****************************************************************************
164; Transfer control to BootSector - Jump to 0x0000:0x7C00
165; ****************************************************************************
166        xor   ax, ax
167        push  ax                        ; PUSH 0x0000
168        mov   di, 07c00h
169        push  di                        ; PUSH 0x7C00
170        retf                            ; JMP 0x0000:0x7C00
171
172; ****************************************************************************
173; ReadBlocks - Reads a set of blocks from a block device
174;
175; EDX:EAX = Start LBA
176; BX      = Number of Blocks to Read (must < 127)
177; ES:DI   = Buffer to store sectors read from disk
178; ****************************************************************************
179
180; si = DiskAddressPacket
181
182ReadBlocks:
183        pushad
184        push  ds
185        xor   cx, cx
186        mov   ds, cx
187        mov   bp, 0600h                         ; bp = 0x600
188        lea   si, [bp + OFFSET AddressPacket]   ; DS:SI = Disk Address Packet
189        mov   BYTE PTR ds:[si+2],bl             ;    02 = Number Of Block transfered
190        mov   WORD PTR ds:[si+4],di             ;    04 = Transfer Buffer Offset
191        mov   WORD PTR ds:[si+6],es             ;    06 = Transfer Buffer Segment
192        mov   DWORD PTR ds:[si+8],eax           ;    08 = Starting LBA (Low)
193        mov   DWORD PTR ds:[si+0ch],edx         ;    0C = Starting LBA (High)
194        mov   ah, 42h                           ; ah = Function 42
195        mov   dl,byte ptr [bp+PhysicalDrive]    ; dl = Drive Number
196        int   13h
197        jc    BadGpt
198        pop   ds
199        popad
200        ret
201
202; ****************************************************************************
203; Address Packet used by ReadBlocks
204; ****************************************************************************
205AddressPacket:
206        db    10h                       ; Size of address packet
207        db    00h                       ; Reserved.  Must be 0
208        db    01h                       ; Read blocks at a time (To be fixed each times)
209        db    00h                       ; Reserved.  Must be 0
210        dw    0000h                     ; Destination Address offset (To be fixed each times)
211        dw    0000h                     ; Destination Address segment (To be fixed each times)
212AddressPacketLba:
213        dd    0h, 0h                    ; Start LBA (To be fixed each times)
214AddressPacketEnd:
215
216; ****************************************************************************
217; ERROR Condition:
218; ****************************************************************************
219
220BadGpt:
221    mov  ax,0b800h
222    mov  es,ax
223    mov  ax, 060h
224    mov  ds, ax
225    lea  si, cs:[ErrorString]
226    mov  cx, 10
227    mov  di, 320
228    rep  movsw
229Halt:
230    jmp   Halt
231
232StartString:
233    db 'G', 0ch, 'P', 0ch, 'T', 0ch, ' ', 0ch, 'S', 0ch, 't', 0ch, 'a', 0ch, 'r', 0ch, 't', 0ch, '!', 0ch
234ErrorString:
235    db 'G', 0ch, 'P', 0ch, 'T', 0ch, ' ', 0ch, 'E', 0ch, 'r', 0ch, 'r', 0ch, 'o', 0ch, 'r', 0ch, '!', 0ch
236
237; ****************************************************************************
238; PhysicalDrive - Used to indicate which disk to be boot
239;                 Can be patched by tool
240; ****************************************************************************
241    org   01B6h
242PhysicalDrive         db  80h
243
244; ****************************************************************************
245; GptPartitionIndicator - Used to indicate which GPT partition to be boot
246;                         Can be patched by tool
247; ****************************************************************************
248    org   01B7h
249GptPartitionIndicator db 0
250
251; ****************************************************************************
252; Unique MBR signature
253; ****************************************************************************
254    org   01B8h
255    db 'DUET'
256
257; ****************************************************************************
258; Unknown
259; ****************************************************************************
260    org   01BCh
261    dw 0
262
263; ****************************************************************************
264; PMBR Entry - Can be patched by tool
265; ****************************************************************************
266    org   01BEh
267    db 0          ; Boot Indicator
268    db 0ffh       ; Start Header
269    db 0ffh       ; Start Sector
270    db 0ffh       ; Start Track
271    db 0eeh       ; OS Type
272    db 0ffh       ; End Header
273    db 0ffh       ; End Sector
274    db 0ffh       ; End Track
275    dd 1          ; Starting LBA
276    dd 0FFFFFFFFh ; End LBA
277
278    org   01CEh
279    dd 0, 0, 0, 0
280    org   01DEh
281    dd 0, 0, 0, 0
282    org   01EEh
283    dd 0, 0, 0, 0
284
285; ****************************************************************************
286; Sector Signature
287; ****************************************************************************
288
289  org 01FEh
290SectorSignature:
291  dw        0aa55h      ; Boot Sector Signature
292
293  end
294
295