| blob | f2e3b91454888fa84bd161f258e2eab17922961e |
1 #------------------------------------------------------------------------------\r
2 #*\r
3 #* Copyright 2006 - 2007, Intel Corporation \r
4 #* All rights reserved. This program and the accompanying materials \r
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 #* bs32.asm\r
13 #* \r
14 #* Abstract:\r
15 #*\r
16 #------------------------------------------------------------------------------\r
17 \r
18 #.MODEL small\r
19 #.stack: \r
20 #.486p: \r
21 #.code: \r
22 .section .text
23 \r
24 .equ FAT_DIRECTORY_ENTRY_SIZE, 0x0020\r
25 .equ FAT_DIRECTORY_ENTRY_SHIFT, 5\r
26 .equ BLOCK_SIZE, 0x0200\r
27 .equ BLOCK_MASK, 0x01ff\r
28 .equ BLOCK_SHIFT, 9\r
29 # "EFILDR_____"\r
30 .equ LOADER_FILENAME_PART1, 0x4c494645 # "EFIL"\r
31 .equ LOADER_FILENAME_PART2, 0x30325244 # "DR20"\r
32 .equ LOADER_FILENAME_PART3, 0x20202030 # "0___"\r
33 \r
34 .org 0x00
35 .global _start
36 _start:\r
37 Ia32Jump: \r
38 jmp BootSectorEntryPoint # JMP inst - 3 bytes\r
39 nop\r
40 \r
41 OemId: .ascii "INTEL " # OemId - 8 bytes\r
42 # BPB data below will be fixed by tool\r
43 SectorSize: .word 0 # Sector Size - 16 bits\r
44 SectorsPerCluster: .byte 0 # Sector Per Cluster - 8 bits\r
45 ReservedSectors: .word 0 # Reserved Sectors - 16 bits\r
46 NoFats: .byte 0 # Number of FATs - 8 bits\r
47 RootEntries: .word 0 # Root Entries - 16 bits\r
48 Sectors: .word 0 # Number of Sectors - 16 bits\r
49 Media: .byte 0 # Media - 8 bits - ignored\r
50 SectorsPerFat: .word 0 # Sectors Per FAT - 16 bits\r
51 SectorsPerTrack: .word 0 # Sectors Per Track - 16 bits - ignored\r
52 Heads: .word 0 # Heads - 16 bits - ignored\r
53 HiddenSectors: .long 0 # Hidden Sectors - 32 bits - ignored\r
54 LargeSectors: .long 0 # Large Sectors - 32 bits \r
55 \r
56 #******************************************************************************\r
57 #\r
58 #The structure for FAT32 starting at offset 36 of the boot sector. (At this point, \r
59 #the BPB/boot sector for FAT12 and FAT16 differs from the BPB/boot sector for FAT32.)\r
60 #\r
61 #******************************************************************************\r
62 \r
63 SectorsPerFat32: .long 0 # Sectors Per FAT for FAT32 - 4 bytes\r
64 ExtFlags: .word 0 # Mirror Flag - 2 bytes\r
65 FSVersion: .word 0 # File System Version - 2 bytes\r
66 RootCluster: .long 0 # 1st Cluster Number of Root Dir - 4 bytes\r
67 FSInfo: .word 0 # Sector Number of FSINFO - 2 bytes\r
68 BkBootSector: .word 0 # Sector Number of Bk BootSector - 2 bytes\r
69 Reserved: .fill 12, 1, 0 # Reserved Field - 12 bytes\r
70 PhysicalDrive: .byte 0 # Physical Drive Number - 1 byte\r
71 Reserved1: .byte 0 # Reserved Field - 1 byte\r
72 Signature: .byte 0 # Extended Boot Signature - 1 byte\r
73 VolId: .ascii " " # Volume Serial Number - 4 bytes\r
74 FatLabel: .ascii " " # Volume Label - 11 bytes\r
75 FileSystemType: .ascii "FAT32 " # File System Type - 8 bytes\r
76 BootSectorEntryPoint: \r
77 #ASSUME ds:@code\r
78 #ASSUME ss:@code\r
79 \r
80 # ****************************************************************************\r
81 # Start Print\r
82 # ****************************************************************************\r
83 leaw %cs:StartString, %si\r
84 call PrintString\r
85 \r
86 # ****************************************************************************\r
87 # Print over\r
88 # ****************************************************************************\r
89 \r
90 movw %cs, %ax # ax = 0\r
91 movw %ax, %ss # ss = 0\r
92 addw $0x1000, %ax\r
93 movw %ax, %ds\r
94 \r
95 movw $0x7c00, %sp # sp = 0x7c00\r
96 movw %sp, %bp # bp = 0x7c00\r
97 \r
98 movb $8, %ah # ah = 8 - Get Drive Parameters Function\r
99 movb %dl, PhysicalDrive(%bp) # BBS defines that BIOS would pass the booting driver number to the loader through DL\r
100 int $0x13 # Get Drive Parameters\r
101 xorw %ax, %ax # ax = 0\r
102 movb %dh, %al # al = dh\r
103 incb %al # MaxHead = al + 1\r
104 pushw %ax # 0000:7bfe = MaxHead\r
105 movb %cl, %al # al = cl\r
106 andb $0x3f, %al # MaxSector = al & 0x3f\r
107 pushw %ax # 0000:7bfc = MaxSector\r
108 \r
109 cmpw $0xaa55, SectorSignature(%bp) # Verify Boot Sector Signature\r
110 jne BadBootSector\r
111 movw RootEntries(%bp), %cx # cx = RootEntries\r
112 shlw $FAT_DIRECTORY_ENTRY_SHIFT, %cx # cx = cx * 32 = cx * sizeof(FAT_DIRECTORY_ENTRY) = Size of Root Directory in bytes\r
113 movw %cx, %bx # bx = size of the Root Directory in bytes\r
114 andw $BLOCK_MASK, %bx # See if it is an even number of sectors long\r
115 jne BadBootSector # If is isn't, then the boot sector is bad.\r
116 movw %cx, %bx # bx = size of the Root Directory in bytes\r
117 shrw $BLOCK_SHIFT, %bx # bx = size of Root Directory in sectors\r
118 movb NoFats(%bp), %al # al = NoFats\r
119 xorb %ah, %ah # ah = 0 ==> ax = NoFats\r
120 mulw SectorsPerFat32(%bp) # ax = NoFats * SectorsPerFat\r
121 addw ReservedSectors(%bp), %ax # ax = NoFats * SectorsPerFat + ReservedSectors = RootLBA\r
122 addw %bx, %ax # ax = NoFats * SectorsPerFat + ReservedSectors + RootDirSectors = FirstClusterLBA\r
123 movw %ax, (%bp) # Save FirstClusterLBA for later use\r
124 \r
125 movw RootCluster(%bp), %ax # ax = StartCluster of Root Directory\r
126 subw $2, %ax # ax = StartCluster - 2\r
127 xorb %bh, %bh\r
128 movb SectorsPerCluster(%bp), %bl # bx = SectorsPerCluster\r
129 mulw %bx # ax = (StartCluster - 2) * SectorsPerCluster\r
130 addw (%bp), %ax # ax = FirstClusterLBA + (StartCluster-2)*SectorsPerCluster\r
131 pushw %ds\r
132 popw %es\r
133 xorw %di, %di # Store directory in es:di = 1000:0000\r
134 call ReadBlocks # Read StartCluster of Root Directory\r
135 \r
136 # dx - variable storage (initial value is 0)\r
137 # bx - loader (initial value is 0)\r
138 xorw %dx, %dx\r
139 xorw %bx, %bx\r
140 \r
141 FindEFILDR: \r
142 cmpl $LOADER_FILENAME_PART1, (%di)\r
143 jne FindVARSTORE\r
144 cmpl $LOADER_FILENAME_PART2, 4(%di)\r
145 jne FindVARSTORE\r
146 cmpl $LOADER_FILENAME_PART3, 7(%di)\r
147 jne FindVARSTORE\r
148 movw 26(%di), %bx # bx = Start Cluster for EFILDR <----------------------------------\r
149 testw %dx, %dx\r
150 je FindNext # Efivar.bin is not loaded\r
151 jmp FoundAll\r
152 \r
153 FindVARSTORE: \r
154 ## if the file is not loader file, see if it's "EFIVAR BIN"\r
155 cmpl $0x56494645, (%di) # Compare to "EFIV"\r
156 jne FindNext\r
157 cmpl $0x20205241, 4(%di) # Compare to "AR "\r
158 jne FindNext\r
159 cmpl $0x4e494220, 7(%di) # Compare to " BIN"\r
160 jne FindNext\r
161 movw %di, %dx # dx = Offset of Start Cluster for Efivar.bin <---------------------\r
162 addw $26, %dx\r
163 testw %bx, %bx\r
164 je FindNext # Efildr is not loaded\r
165 jmp FoundAll\r
166 \r
167 FindNext: \r
168 # go to next find\r
169 addw $FAT_DIRECTORY_ENTRY_SIZE, %di # Increment di\r
170 subw $FAT_DIRECTORY_ENTRY_SIZE, %cx # Decrement cx\r
171 # TODO: jump to FindVarStore if ...\r
172 jne FindEFILDR\r
173 jmp NotFoundAll\r
174 \r
175 FoundAll: \r
176 FoundEFILDR: \r
177 movw %bx, %cx # cx = Start Cluster for EFILDR <----------------------------------\r
178 movw %cs, %ax # Destination = 2000:0000\r
179 addw $0x2000, %ax\r
180 movw %ax, %es\r
181 xorw %di, %di\r
182 ReadFirstClusterOfEFILDR: \r
183 movw %cx, %ax # ax = StartCluster\r
184 subw $2, %ax # ax = StartCluster - 2\r
185 xorb %bh, %bh\r
186 movb SectorsPerCluster(%bp), %bl # bx = SectorsPerCluster\r
187 pushw %dx\r
188 mulw %bx\r
189 popw %dx # ax = (StartCluster - 2) * SectorsPerCluster\r
190 addw (%bp), %ax # ax = FirstClusterLBA + (StartCluster-2)*SectorsPerCluster\r
191 xorb %bh, %bh\r
192 movb SectorsPerCluster(%bp), %bl # bx = Number of Sectors in a cluster\r
193 pushw %es\r
194 call ReadBlocks\r
195 popw %ax\r
196 JumpIntoFirstSectorOfEFILDR: \r
197 movw %ax, JumpSegment(%bp)\r
198 JumpFarInstruction: \r
199 .byte 0xea\r
200 JumpOffset: \r
201 .word 0x000\r
202 JumpSegment: \r
203 .word 0x2000\r
204 \r
205 \r
206 PrintString: \r
207 movw $0xb800, %ax\r
208 movw %ax, %es\r
209 movw $0x7c0, %ax\r
210 movw %ax, %ds\r
211 movw $7, %cx\r
212 movw $160, %di\r
213 rep\r
214 movsw\r
215 ret\r
216 # ****************************************************************************\r
217 # ReadBlocks - Reads a set of blocks from a block device\r
218 #\r
219 # AX = Start LBA\r
220 # BX = Number of Blocks to Read\r
221 # ES:DI = Buffer to store sectors read from disk\r
222 # ****************************************************************************\r
223 \r
224 # cx = Blocks\r
225 # bx = NumberOfBlocks\r
226 # si = StartLBA\r
227 \r
228 ReadBlocks: \r
229 pusha\r
230 addl LBAOffsetForBootSector(%bp), %eax # Add LBAOffsetForBootSector to Start LBA\r
231 addl HiddenSectors(%bp), %eax # Add HiddenSectors to Start LBA\r
232 movl %eax, %esi # esi = Start LBA\r
233 movw %bx, %cx # cx = Number of blocks to read\r
234 ReadCylinderLoop: \r
235 movw $0x7bfc, %bp # bp = 0x7bfc\r
236 movl %esi, %eax # eax = Start LBA\r
237 xorl %edx, %edx # edx = 0\r
238 movzwl (%bp), %ebx # bx = MaxSector\r
239 divl %ebx # ax = StartLBA / MaxSector\r
240 incw %dx # dx = (StartLBA % MaxSector) + 1\r
241 subw %dx, %bx # bx = MaxSector - Sector\r
242 incw %bx # bx = MaxSector - Sector + 1\r
243 cmpw %bx, %cx # Compare (Blocks) to (MaxSector - Sector + 1)\r
244 jg LimitTransfer\r
245 movw %cx, %bx # bx = Blocks\r
246 LimitTransfer: \r
247 pushw %cx\r
248 movb %dl, %cl # cl = (StartLBA % MaxSector) + 1 = Sector\r
249 xorw %dx, %dx # dx = 0\r
250 divw 2(%bp) # ax = ax / (MaxHead + 1) = Cylinder \r
251 # dx = ax % (MaxHead + 1) = Head\r
252 \r
253 pushw %bx # Save number of blocks to transfer\r
254 movb %dl, %dh # dh = Head\r
255 movw $0x7c00, %bp # bp = 0x7c00\r
256 movb PhysicalDrive(%bp), %dl # dl = Drive Number\r
257 movb %al, %ch # ch = Cylinder\r
258 movb %bl, %al # al = Blocks\r
259 movb $2, %ah # ah = Function 2\r
260 movw %di, %bx # es:bx = Buffer address\r
261 int $0x13\r
262 jc DiskError\r
263 popw %bx\r
264 popw %cx\r
265 movzwl %bx, %ebx\r
266 addl %ebx, %esi # StartLBA = StartLBA + NumberOfBlocks\r
267 subw %bx, %cx # Blocks = Blocks - NumberOfBlocks\r
268 movw %es, %ax\r
269 shlw $(BLOCK_SHIFT-4), %bx\r
270 addw %bx, %ax\r
271 movw %ax, %es # es:di = es:di + NumberOfBlocks*BLOCK_SIZE\r
272 cmpw $0, %cx\r
273 jne ReadCylinderLoop\r
274 popa\r
275 ret\r
276 \r
277 # ****************************************************************************\r
278 # ERROR Condition:\r
279 # ****************************************************************************\r
280 NotFoundAll: \r
281 ## if we found EFILDR, continue\r
282 testw %bx, %bx\r
283 jne FoundEFILDR\r
284 BadBootSector: \r
285 DiskError: \r
286 leaw %cs:ErrorString, %si\r
287 call PrintString\r
288 Halt: \r
289 jmp Halt\r
290 \r
291 StartString: \r
292 .byte 'B', 0x0c, 'S', 0x0c, 't', 0x0c, 'a', 0x0c, 'r', 0x0c, 't', 0x0c, '!', 0x0c\r
293 ErrorString: \r
294 .byte 'B', 0x0c, 'E', 0x0c, 'r', 0x0c, 'r', 0x0c, 'o', 0x0c, 'r', 0x0c, '!', 0x0c\r
295 \r
296 # ****************************************************************************\r
297 # LBA Offset for BootSector, need patched by tool for HD boot.\r
298 # ****************************************************************************\r
299 \r
300 # .org 0x01fa # BUG_BUG\r
301 LBAOffsetForBootSector: \r
302 .long 0x0\r
303 \r
304 # ****************************************************************************\r
305 # Sector Signature\r
306 # ****************************************************************************\r
307 \r
308 # .org 0x01fe # BUG_BUG\r
309 SectorSignature: \r
310 .word 0xaa55 # Boot Sector Signature\r
311 \r
312 \r
313 \r