| blob | 5df6d6a521abfb3dba8af1a2a19f723b13a8db20 |
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 .code16\r
22 \r
23 .equ FAT_DIRECTORY_ENTRY_SIZE, 0x0020\r
24 .equ FAT_DIRECTORY_ENTRY_SHIFT, 5\r
25 .equ BLOCK_SIZE, 0x0200\r
26 .equ BLOCK_MASK, 0x01ff\r
27 .equ BLOCK_SHIFT, 9\r
28 # "EFILDR_____"\r
29 .equ LOADER_FILENAME_PART1, 0x4c494645 # "EFIL"\r
30 .equ LOADER_FILENAME_PART2, 0x30325244 # "DR20"\r
31 .equ LOADER_FILENAME_PART3, 0x20202030 # "0___"\r
32 \r
33 .org 0x0
34 .global _start
35 _start:\r
36 Ia32Jump: \r
37 jmp BootSectorEntryPoint # JMP inst - 3 bytes\r
38 nop\r
39 \r
40 OemId: .ascii "INTEL " # OemId - 8 bytes\r
41 # BPB data below will be fixed by tool\r
42 SectorSize: .word 0 # Sector Size - 16 bits\r
43 SectorsPerCluster: .byte 0 # Sector Per Cluster - 8 bits\r
44 ReservedSectors: .word 0 # Reserved Sectors - 16 bits\r
45 NoFats: .byte 0 # Number of FATs - 8 bits\r
46 RootEntries: .word 0 # Root Entries - 16 bits\r
47 Sectors: .word 0 # Number of Sectors - 16 bits\r
48 Media: .byte 0 # Media - 8 bits - ignored\r
49 SectorsPerFat: .word 0 # Sectors Per FAT - 16 bits\r
50 SectorsPerTrack: .word 0 # Sectors Per Track - 16 bits - ignored\r
51 Heads: .word 0 # Heads - 16 bits - ignored\r
52 HiddenSectors: .long 0 # Hidden Sectors - 32 bits - ignored\r
53 LargeSectors: .long 0 # Large Sectors - 32 bits \r
54 \r
55 #******************************************************************************\r
56 #\r
57 #The structure for FAT32 starting at offset 36 of the boot sector. (At this point, \r
58 #the BPB/boot sector for FAT12 and FAT16 differs from the BPB/boot sector for FAT32.)\r
59 #\r
60 #******************************************************************************\r
61 \r
62 SectorsPerFat32: .long 0 # Sectors Per FAT for FAT32 - 4 bytes\r
63 ExtFlags: .word 0 # Mirror Flag - 2 bytes\r
64 FSVersion: .word 0 # File System Version - 2 bytes\r
65 RootCluster: .long 0 # 1st Cluster Number of Root Dir - 4 bytes\r
66 FSInfo: .word 0 # Sector Number of FSINFO - 2 bytes\r
67 BkBootSector: .word 0 # Sector Number of Bk BootSector - 2 bytes\r
68 Reserved: .fill 12, 1, 0 # Reserved Field - 12 bytes\r
69 PhysicalDrive: .byte 0 # Physical Drive Number - 1 byte\r
70 Reserved1: .byte 0 # Reserved Field - 1 byte\r
71 Signature: .byte 0 # Extended Boot Signature - 1 byte\r
72 VolId: .ascii " " # Volume Serial Number - 4 bytes\r
73 FatLabel: .ascii " " # Volume Label - 11 bytes\r
74 FileSystemType: .ascii "FAT32 " # File System Type - 8 bytes\r
75 BootSectorEntryPoint: \r
76 #ASSUME ds:@code\r
77 #ASSUME ss:@code\r
78 \r
79 # ****************************************************************************\r
80 # Start Print\r
81 # ****************************************************************************\r
82 movw $StartString, %si\r
83 call PrintString\r
84 \r
85 # ****************************************************************************\r
86 # Print over\r
87 # ****************************************************************************\r
88 \r
89 movw %cs, %ax # ax = 0\r
90 movw %ax, %ss # ss = 0\r
91 addw $0x1000, %ax\r
92 movw %ax, %ds\r
93 \r
94 movw $0x7c00, %sp # sp = 0x7c00\r
95 movw %sp, %bp # bp = 0x7c00\r
96 \r
97 movb $8, %ah # ah = 8 - Get Drive Parameters Function\r
98 movb %dl, PhysicalDrive(%bp) # BBS defines that BIOS would pass the booting driver number to the loader through DL\r
99 int $0x13 # Get Drive Parameters\r
100 xorw %ax, %ax # ax = 0\r
101 movb %dh, %al # al = dh\r
102 incb %al # MaxHead = al + 1\r
103 pushw %ax # 0000:7bfe = MaxHead\r
104 movb %cl, %al # al = cl\r
105 andb $0x3f, %al # MaxSector = al & 0x3f\r
106 pushw %ax # 0000:7bfc = MaxSector\r
107 \r
108 cmpw $0xaa55, SectorSignature(%bp) # Verify Boot Sector Signature\r
109 jne BadBootSector\r
110 movw RootEntries(%bp), %cx # cx = RootEntries\r
111 shlw $FAT_DIRECTORY_ENTRY_SHIFT, %cx # cx = cx * 32 = cx * sizeof(FAT_DIRECTORY_ENTRY) = Size of Root Directory in bytes\r
112 movw %cx, %bx # bx = size of the Root Directory in bytes\r
113 andw $BLOCK_MASK, %bx # See if it is an even number of sectors long\r
114 jne BadBootSector # If is isn't, then the boot sector is bad.\r
115 movw %cx, %bx # bx = size of the Root Directory in bytes\r
116 shrw $BLOCK_SHIFT, %bx # bx = size of Root Directory in sectors\r
117 movb NoFats(%bp), %al # al = NoFats\r
118 xorb %ah, %ah # ah = 0 ==> ax = NoFats\r
119 mulw SectorsPerFat32(%bp) # ax = NoFats * SectorsPerFat\r
120 addw ReservedSectors(%bp), %ax # ax = NoFats * SectorsPerFat + ReservedSectors = RootLBA\r
121 addw %bx, %ax # ax = NoFats * SectorsPerFat + ReservedSectors + RootDirSectors = FirstClusterLBA\r
122 movw %ax, (%bp) # Save FirstClusterLBA for later use\r
123 \r
124 movw RootCluster(%bp), %ax # ax = StartCluster of Root Directory\r
125 subw $2, %ax # ax = StartCluster - 2\r
126 xorb %bh, %bh\r
127 movb SectorsPerCluster(%bp), %bl # bx = SectorsPerCluster\r
128 mulw %bx # ax = (StartCluster - 2) * SectorsPerCluster\r
129 addw (%bp), %ax # ax = FirstClusterLBA + (StartCluster-2)*SectorsPerCluster\r
130 pushw %ds\r
131 popw %es\r
132 xorw %di, %di # Store directory in es:di = 1000:0000\r
133 call ReadBlocks # Read StartCluster of Root Directory\r
134 \r
135 # dx - variable storage (initial value is 0)\r
136 # bx - loader (initial value is 0)\r
137 xorw %dx, %dx\r
138 xorw %bx, %bx\r
139 \r
140 FindEFILDR: \r
141 cmpl $LOADER_FILENAME_PART1, (%di)\r
142 jne FindVARSTORE\r
143 cmpl $LOADER_FILENAME_PART2, 4(%di)\r
144 jne FindVARSTORE\r
145 cmpl $LOADER_FILENAME_PART3, 7(%di)\r
146 jne FindVARSTORE\r
147 movw 26(%di), %bx # bx = Start Cluster for EFILDR <----------------------------------\r
148 testw %dx, %dx\r
149 je FindNext # Efivar.bin is not loaded\r
150 jmp FoundAll\r
151 \r
152 FindVARSTORE: \r
153 ## if the file is not loader file, see if it's "EFIVAR BIN"\r
154 cmpl $0x56494645, (%di) # Compare to "EFIV"\r
155 jne FindNext\r
156 cmpl $0x20205241, 4(%di) # Compare to "AR "\r
157 jne FindNext\r
158 cmpl $0x4e494220, 7(%di) # Compare to " BIN"\r
159 jne FindNext\r
160 movw %di, %dx # dx = Offset of Start Cluster for Efivar.bin <---------------------\r
161 addw $26, %dx\r
162 testw %bx, %bx\r
163 je FindNext # Efildr is not loaded\r
164 jmp FoundAll\r
165 \r
166 FindNext: \r
167 # go to next find\r
168 addw $FAT_DIRECTORY_ENTRY_SIZE, %di # Increment di\r
169 subw $FAT_DIRECTORY_ENTRY_SIZE, %cx # Decrement cx\r
170 # TODO: jump to FindVarStore if ...\r
171 jne FindEFILDR\r
172 jmp NotFoundAll\r
173 \r
174 FoundAll: \r
175 FoundEFILDR: \r
176 movw %bx, %cx # cx = Start Cluster for EFILDR <----------------------------------\r
177 movw %cs, %ax # Destination = 2000:0000\r
178 addw $0x2000, %ax\r
179 movw %ax, %es\r
180 xorw %di, %di\r
181 ReadFirstClusterOfEFILDR: \r
182 movw %cx, %ax # ax = StartCluster\r
183 subw $2, %ax # ax = StartCluster - 2\r
184 xorb %bh, %bh\r
185 movb SectorsPerCluster(%bp), %bl # bx = SectorsPerCluster\r
186 pushw %dx\r
187 mulw %bx\r
188 popw %dx # ax = (StartCluster - 2) * SectorsPerCluster\r
189 addw (%bp), %ax # ax = FirstClusterLBA + (StartCluster-2)*SectorsPerCluster\r
190 xorb %bh, %bh\r
191 movb SectorsPerCluster(%bp), %bl # bx = Number of Sectors in a cluster\r
192 pushw %es\r
193 call ReadBlocks\r
194 popw %ax\r
195 JumpIntoFirstSectorOfEFILDR: \r
196 movw %ax, JumpSegment(%bp)\r
197 JumpFarInstruction: \r
198 .byte 0xea\r
199 JumpOffset: \r
200 .word 0x000\r
201 JumpSegment: \r
202 .word 0x2000\r
203 \r
204 \r
205 PrintString: \r
206 movw $0xb800, %ax\r
207 movw %ax, %es\r
208 movw $0x7c0, %ax\r
209 movw %ax, %ds\r
210 movw $7, %cx\r
211 movw $160, %di\r
212 rep\r
213 movsw\r
214 ret\r
215 # ****************************************************************************\r
216 # ReadBlocks - Reads a set of blocks from a block device\r
217 #\r
218 # AX = Start LBA\r
219 # BX = Number of Blocks to Read\r
220 # ES:DI = Buffer to store sectors read from disk\r
221 # ****************************************************************************\r
222 \r
223 # cx = Blocks\r
224 # bx = NumberOfBlocks\r
225 # si = StartLBA\r
226 \r
227 ReadBlocks: \r
228 pusha\r
229 addl LBAOffsetForBootSector(%bp), %eax # Add LBAOffsetForBootSector to Start LBA\r
230 addl HiddenSectors(%bp), %eax # Add HiddenSectors to Start LBA\r
231 movl %eax, %esi # esi = Start LBA\r
232 movw %bx, %cx # cx = Number of blocks to read\r
233 ReadCylinderLoop: \r
234 movw $0x7bfc, %bp # bp = 0x7bfc\r
235 movl %esi, %eax # eax = Start LBA\r
236 xorl %edx, %edx # edx = 0\r
237 movzwl (%bp), %ebx # bx = MaxSector\r
238 divl %ebx # ax = StartLBA / MaxSector\r
239 incw %dx # dx = (StartLBA % MaxSector) + 1\r
240 subw %dx, %bx # bx = MaxSector - Sector\r
241 incw %bx # bx = MaxSector - Sector + 1\r
242 cmpw %bx, %cx # Compare (Blocks) to (MaxSector - Sector + 1)\r
243 jg LimitTransfer\r
244 movw %cx, %bx # bx = Blocks\r
245 LimitTransfer: \r
246 pushw %cx\r
247 movb %dl, %cl # cl = (StartLBA % MaxSector) + 1 = Sector\r
248 xorw %dx, %dx # dx = 0\r
249 divw 2(%bp) # ax = ax / (MaxHead + 1) = Cylinder \r
250 # dx = ax % (MaxHead + 1) = Head\r
251 \r
252 pushw %bx # Save number of blocks to transfer\r
253 movb %dl, %dh # dh = Head\r
254 movw $0x7c00, %bp # bp = 0x7c00\r
255 movb PhysicalDrive(%bp), %dl # dl = Drive Number\r
256 movb %al, %ch # ch = Cylinder\r
257 movb %bl, %al # al = Blocks\r
258 movb $2, %ah # ah = Function 2\r
259 movw %di, %bx # es:bx = Buffer address\r
260 int $0x13\r
261 jc DiskError\r
262 popw %bx\r
263 popw %cx\r
264 movzwl %bx, %ebx\r
265 addl %ebx, %esi # StartLBA = StartLBA + NumberOfBlocks\r
266 subw %bx, %cx # Blocks = Blocks - NumberOfBlocks\r
267 movw %es, %ax\r
268 shlw $(BLOCK_SHIFT-4), %bx\r
269 addw %bx, %ax\r
270 movw %ax, %es # es:di = es:di + NumberOfBlocks*BLOCK_SIZE\r
271 cmpw $0, %cx\r
272 jne ReadCylinderLoop\r
273 popa\r
274 ret\r
275 \r
276 # ****************************************************************************\r
277 # ERROR Condition:\r
278 # ****************************************************************************\r
279 NotFoundAll: \r
280 ## if we found EFILDR, continue\r
281 testw %bx, %bx\r
282 jne FoundEFILDR\r
283 BadBootSector: \r
284 DiskError: \r
285 movw $ErrorString, %si\r
286 call PrintString\r
287 Halt: \r
288 jmp Halt\r
289 \r
290 StartString: \r
291 .byte 'B', 0x0c, 'S', 0x0c, 't', 0x0c, 'a', 0x0c, 'r', 0x0c, 't', 0x0c, '!', 0x0c\r
292 ErrorString: \r
293 .byte 'B', 0x0c, 'E', 0x0c, 'r', 0x0c, 'r', 0x0c, 'o', 0x0c, 'r', 0x0c, '!', 0x0c\r
294 \r
295 # ****************************************************************************\r
296 # LBA Offset for BootSector, need patched by tool for HD boot.\r
297 # ****************************************************************************\r
298 \r
299 #.org 0x01fa\r
300 LBAOffsetForBootSector: \r
301 .long 0x0\r
302 \r
303 # ****************************************************************************\r
304 # Sector Signature\r
305 # ****************************************************************************\r
306 \r
307 #.org 0x01fe\r
308 SectorSignature: \r
309 .word 0xaa55 # Boot Sector Signature\r
310 \r
311 \r
312 \r