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f3eb2131 | 1 | #------------------------------------------------------------------------------\r |
2 | #*\r | |
e7c4ef5e | 3 | #* Copyright (c) 2006 - 2012, Intel Corporation. All rights reserved.<BR>\r |
b1f700a8 | 4 | #* This program and the accompanying materials\r |
f3eb2131 | 5 | #* are licensed and made available under the terms and conditions of the BSD License\r |
6 | #* which accompanies this distribution. The full text of the license may be found at\r | |
7 | #* http://opensource.org/licenses/bsd-license.php\r | |
8 | #*\r | |
9 | #* THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r | |
10 | #* WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r | |
11 | #*\r | |
12 | #* Mbr.asm\r | |
13 | #*\r | |
14 | #* Abstract:\r | |
15 | #*\r | |
16 | #------------------------------------------------------------------------------\r | |
17 | \r | |
697ecfd3 | 18 | .code16 \r |
19 | \r | |
f3eb2131 | 20 | .equ BLOCK_SIZE, 0x0200\r |
21 | .equ BLOCK_MASK, 0x01ff\r | |
22 | .equ BLOCK_SHIFT, 9\r | |
23 | \r | |
24 | # ****************************************************************************\r | |
25 | # Code loaded by BIOS at 0x0000:0x7C00\r | |
26 | # ****************************************************************************\r | |
27 | \r | |
28 | .org 0x0\r | |
29 | \r | |
ae3d1e91 | 30 | .global _start\r |
f3eb2131 | 31 | _start:\r |
32 | \r | |
33 | # ****************************************************************************\r | |
34 | # Start Print\r | |
35 | # ****************************************************************************\r | |
36 | \r | |
37 | movw $0xb800, %ax\r | |
38 | movw %ax, %es\r | |
39 | movw $0x7c0, %ax\r | |
40 | movw %ax, %ds\r | |
41 | leaw %cs:StartString, %si\r | |
42 | movw $10, %cx\r | |
43 | movw $160, %di\r | |
44 | rep \r | |
45 | movsw\r | |
46 | \r | |
47 | # ****************************************************************************\r | |
48 | # Print over\r | |
49 | # ****************************************************************************\r | |
50 | \r | |
51 | # ****************************************************************************\r | |
52 | # Initialize segment registers and copy code at 0x0000:0x7c00 to 0x0000:0x0600\r | |
53 | # ****************************************************************************\r | |
54 | xorw %ax, %ax # AX = 0x0000\r | |
55 | movw $0x7c00, %bx # BX = 0x7C00\r | |
56 | movw $0x600, %bp # BP = 0x0600\r | |
e7c4ef5e | 57 | movw $RelocatedStart, %si # SI = Offset(RelocatedStart)\r |
f3eb2131 | 58 | movw $0x200, %cx # CX = 0x0200\r |
59 | subw %si, %cx # CS = 0x0200 - Offset(RelocatedStart)\r | |
60 | leaw (%bp,%si,), %di # DI = 0x0600 + Offset(RelocatedStart)\r | |
61 | leaw (%bx,%si,), %si # BX = 0x7C00 + Offset(RelocatedStart)\r | |
62 | movw %ax, %ss # SS = 0x0000\r | |
63 | movw %bx, %sp # SP = 0x7C00\r | |
64 | movw %ax, %es # ES = 0x0000\r | |
65 | movw %ax, %ds # DS = 0x0000\r | |
66 | pushw %ax # PUSH 0x0000\r | |
67 | pushw %di # PUSH 0x0600 + Offset(RelocatedStart)\r | |
68 | cld # Clear the direction flag\r | |
69 | rep\r | |
70 | movsb # Copy 0x0200 bytes from 0x7C00 to 0x0600\r | |
71 | retl # JMP 0x0000:0x0600 + Offset(RelocatedStart)\r | |
72 | \r | |
73 | # ****************************************************************************\r | |
74 | # Code relocated to 0x0000:0x0600\r | |
75 | # ****************************************************************************\r | |
76 | \r | |
77 | RelocatedStart: \r | |
78 | # ****************************************************************************\r | |
79 | # Get Driver Parameters to 0x0000:0x7BFC\r | |
80 | # ****************************************************************************\r | |
81 | \r | |
82 | xorw %ax, %ax # AX = 0\r | |
83 | movw %ax, %ss # SS = 0\r | |
84 | addw $0x1000, %ax\r | |
85 | movw %ax, %ds\r | |
86 | \r | |
87 | movw $0x7c00, %sp # SP = 0x7c00\r | |
88 | movw %sp, %bp # BP = 0x7c00\r | |
89 | \r | |
90 | movb $8, %ah # AH = 8 - Get Drive Parameters Function\r | |
91 | movb %dl, PhysicalDrive(%bp) # BBS defines that BIOS would pass the booting driver number to the loader through DL\r | |
92 | int $0x13 # Get Drive Parameters\r | |
93 | xorw %ax, %ax # AX = 0\r | |
94 | movb %dh, %al # AL = DH\r | |
95 | incb %al # MaxHead = AL + 1\r | |
96 | pushw %ax # 0000:7bfe = MaxHead\r | |
97 | movb %cl, %al # AL = CL\r | |
98 | andb $0x3f, %al # MaxSector = AL & 0x3f\r | |
99 | pushw %ax # 0000:7bfc = MaxSector\r | |
100 | \r | |
101 | # ****************************************************************************\r | |
102 | # Read Target DBR from hard disk to 0x0000:0x7C00\r | |
103 | # ****************************************************************************\r | |
104 | \r | |
105 | xorw %ax, %ax\r | |
106 | movb MbrPartitionIndicator(%bp), %al # AX = MbrPartitionIndex\r | |
107 | cmpb $0xff, %al # 0xFF means do legacy MBR boot\r | |
108 | jnz EfiDbr\r | |
109 | LegacyMbr: \r | |
110 | movl $0x0000600, %eax # Assume LegacyMBR is backuped in Sector 6\r | |
111 | jmp StartReadTo7C00 # EAX = Header/Sector/Tracker/Zero\r | |
112 | \r | |
113 | EfiDbr: \r | |
114 | cmpb $4, %al # MbrPartitionIndex should < 4\r | |
115 | jae BadDbr\r | |
116 | shlw $4, %ax # AX = MBREntrySize * Index\r | |
117 | addw $0x1be, %ax # AX = MBREntryOffset\r | |
118 | movw %ax, %di # DI = MBREntryOffset\r | |
119 | \r | |
120 | # Here we don't use the C/H/S information provided by Partition table\r | |
121 | # but calculate C/H/S from LBA ourselves\r | |
122 | # Ci: Cylinder number\r | |
123 | # Hi: Header number\r | |
124 | # Si: Sector number\r | |
125 | movl %es:8(%bp,%di,), %eax # Start LBA\r | |
126 | movl %eax, %edx\r | |
127 | shrl $16, %edx # DX:AX = Start LBA\r | |
128 | # = Ci * (H * S) + Hi * S + (Si - 1)\r | |
129 | \r | |
130 | # Calculate C/H/S according to LBA\r | |
131 | movw $0x7bfa, %bp\r | |
132 | divw 2(%bp) # AX = Hi + H*Ci\r | |
133 | # DX = Si - 1\r | |
134 | incw %dx # DX = Si\r | |
135 | pushw %dx # 0000:7bfa = Si <----\r | |
136 | xorw %dx, %dx # DX:AX = Hi + H*Ci\r | |
137 | divw 4(%bp) # AX = Ci <----\r | |
138 | # DX = Hi <----\r | |
139 | \r | |
140 | StartReadTo7C00: \r | |
141 | \r | |
142 | movb (%bp), %cl # Si\r | |
143 | movb %al, %ch # Ci[0-7]\r | |
144 | orb %ah, %cl # Ci[8,9]\r | |
145 | movw $0x7c00, %bx # ES:BX = 0000:7C00h\r | |
146 | movb $0x2, %ah # Function 02h\r | |
147 | movb $1, %al # 1 Sector\r | |
148 | movb %dl, %dh # Hi\r | |
149 | movw $0x600, %bp\r | |
150 | movb PhysicalDrive(%bp), %dl # Drive number\r | |
151 | int $0x13\r | |
152 | jc BadDbr\r | |
153 | \r | |
154 | \r | |
155 | \r | |
156 | # ****************************************************************************\r | |
157 | # Transfer control to BootSector - Jump to 0x0000:0x7C00\r | |
158 | # ****************************************************************************\r | |
159 | xorw %ax, %ax\r | |
160 | pushw %ax # PUSH 0x0000 - Segment\r | |
161 | movw $0x7c00, %di\r | |
162 | pushw %di # PUSH 0x7C00 - Offset\r | |
163 | retl # JMP 0x0000:0x7C00\r | |
164 | \r | |
165 | # ****************************************************************************\r | |
166 | # ERROR Condition:\r | |
167 | # ****************************************************************************\r | |
168 | \r | |
169 | BadDbr: \r | |
170 | pushw %ax\r | |
171 | movw $0xb800, %ax\r | |
172 | movw %ax, %es\r | |
173 | movw $0x60, %ax\r | |
174 | movw %ax, %ds\r | |
175 | leaw %cs:ErrorString, %si\r | |
176 | movw $320, %di\r | |
177 | popw %ax\r | |
178 | call A2C\r | |
179 | movb %ah, 16(%si)\r | |
180 | movb %al, 18(%si)\r | |
181 | movw $10, %cx\r | |
182 | rep\r | |
183 | movsw\r | |
184 | Halt: \r | |
185 | jmp Halt\r | |
186 | \r | |
187 | StartString: \r | |
188 | .byte 'M', 0x0c, 'B', 0x0c, 'R', 0x0c, ' ', 0x0c, 'S', 0x0c, 't', 0x0c, 'a', 0x0c, 'r', 0x0c, 't', 0x0c, '!', 0x0c\r | |
189 | ErrorString: \r | |
190 | .byte 'M', 0x0c, 'B', 0x0c, 'R', 0x0c, ' ', 0x0c, 'E', 0x0c, 'r', 0x0c, 'r', 0x0c, ':', 0x0c, '?', 0x0c, '?', 0x0c\r | |
191 | \r | |
192 | # ****************************************************************************\r | |
193 | # A2C - convert Ascii code stored in AH to character stored in AX\r | |
194 | # ****************************************************************************\r | |
195 | A2C: \r | |
196 | movb %ah, %al\r | |
197 | shrb $4, %ah\r | |
198 | andb $0xF, %al\r | |
199 | addb '0', %ah\r | |
200 | addb '0', %al\r | |
201 | \r | |
202 | cmpb '9', %ah\r | |
203 | jle A2C_L1\r | |
204 | addb $7, %ah\r | |
205 | A2C_L1: \r | |
206 | \r | |
207 | cmpb '9', %al\r | |
208 | jle A2C_L2\r | |
209 | addb $7, %al\r | |
210 | A2C_L2: \r | |
211 | ret\r | |
212 | \r | |
213 | \r | |
214 | # ****************************************************************************\r | |
215 | # PhysicalDrive - Used to indicate which disk to be boot\r | |
216 | # Can be patched by tool\r | |
217 | # ****************************************************************************\r | |
218 | .org 0x01B6\r | |
219 | PhysicalDrive: .byte 0x80\r | |
220 | \r | |
221 | # ****************************************************************************\r | |
222 | # MbrPartitionIndicator - Used to indicate which MBR partition to be boot\r | |
223 | # Can be patched by tool\r | |
224 | # OxFF means boot to legacy MBR. (LBA OFFSET 6)\r | |
225 | # ****************************************************************************\r | |
226 | .org 0x01B7\r | |
227 | MbrPartitionIndicator: .byte 0\r | |
228 | \r | |
229 | # ****************************************************************************\r | |
230 | # Unique MBR signature\r | |
231 | # ****************************************************************************\r | |
232 | .org 0x01B8\r | |
233 | .ascii "DUET"\r | |
234 | \r | |
235 | # ****************************************************************************\r | |
236 | # Unknown\r | |
237 | # ****************************************************************************\r | |
238 | .org 0x01BC\r | |
239 | .word 0\r | |
240 | \r | |
241 | # ****************************************************************************\r | |
242 | # MBR Entry - To be patched\r | |
243 | # ****************************************************************************\r | |
244 | .org 0x01BE\r | |
245 | .long 0,0,0,0\r | |
246 | .org 0x01CE\r | |
247 | .long 0,0,0,0\r | |
248 | .org 0x01DE\r | |
249 | .long 0,0,0,0\r | |
250 | .org 0x01EE\r | |
251 | .long 0,0,0,0\r | |
252 | \r | |
253 | # ****************************************************************************\r | |
254 | # Sector Signature\r | |
255 | # ****************************************************************************\r | |
256 | \r | |
257 | .org 0x01FE\r | |
258 | SectorSignature: \r | |
259 | .word 0xaa55 # Boot Sector Signature\r | |
260 | \r | |
261 | \r | |
262 | \r |