Gitiles
Code Review Sign In
gerrit.devboardsforandroid.linaro.org / device / linaro / hikey960 / 82c807137a2c3f033e23e414476d131e88ad221a / . / uefi / linaro-edk2 / DuetPkg / BootSector / bootsect.S
blob: 5993a1ac99310cb5875e18431598483b3b486881 [file] [log] [blame]
Vishal Bhoj82c80712015-12-15 21:13:33 +0530[diff] [blame^]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#* bootsect.S
13#*
14#* bootsect.S is built as 16-bit binary file in 512 bytes and patched to disk/partition's
15#* first section - boot sector.
16#*
17#* The startup sequence for DUET disk boot sector is:
18#*
19#* 1, LegacyBios check 0xAA55 signature at boot sectore offset 0x1FE to judget
20#* whether disk/partition is bootable.
21#* 2, LegacyBios will load boot sector to 0x7c00 in real mode, pass BPB data and
22#* hand off control to 0x7c00 code.
23#* 3, boot sector code simply parse FAT format in boot disk and find EfiLdr binary file
24#* and EfiVar.bin if exists. For first boot, EfiVar.bin does not exist.
25#* 4, boot sector load the first sector of EfiLdr binary which is start.com to
26#* 0x2000:0x0000 address.
27#* 5, boot sector handoff control to 0x2000:0x0000 for start.com binary.
28#*
29#------------------------------------------------------------------------------
30
31 .stack:
32 .486p:
33 .code16
34
35.equ FAT_DIRECTORY_ENTRY_SIZE, 0x020
36.equ FAT_DIRECTORY_ENTRY_SHIFT, 5
37.equ BLOCK_SIZE, 0x0200
38.equ BLOCK_MASK, 0x01ff
39.equ BLOCK_SHIFT, 9
40 # "EFILDR_____"
41.equ LOADER_FILENAME_PART1, 0x04c494645 # "EFIL"
42.equ LOADER_FILENAME_PART2, 0x020205244 # "DR__"
43.equ LOADER_FILENAME_PART3, 0x020202020 # "____"
44
45 .org 0x0
46.global _start
47_start:
48Ia32Jump:
49 jmp BootSectorEntryPoint # JMP inst - 3 bytes
50 nop
51
52OemId: .ascii "INTEL " # OemId - 8 bytes
53# BPB data below will be fixed by tool
54SectorSize: .word 0 # Sector Size - 16 bits
55SectorsPerCluster: .byte 0 # Sector Per Cluster - 8 bits
56ReservedSectors: .word 0 # Reserved Sectors - 16 bits
57NoFats: .byte 0 # Number of FATs - 8 bits
58RootEntries: .word 0 # Root Entries - 16 bits
59Sectors: .word 0 # Number of Sectors - 16 bits
60Media: .byte 0 # Media - 8 bits - ignored
61SectorsPerFat: .word 0 # Sectors Per FAT - 16 bits
62SectorsPerTrack: .word 0 # Sectors Per Track - 16 bits - ignored
63Heads: .word 0 # Heads - 16 bits - ignored
64HiddenSectors: .long 0 # Hidden Sectors - 32 bits - ignored
65LargeSectors: .long 0 # Large Sectors - 32 bits
66PhysicalDrive: .byte 0 # PhysicalDriveNumber - 8 bits - ignored
67CurrentHead: .byte 0 # Current Head - 8 bits
68Signature: .byte 0 # Signature - 8 bits - ignored
69VolId: .ascii " " # Volume Serial Number- 4 bytes
70FatLabel: .ascii " " # Label - 11 bytes
71SystemId: .ascii "FAT12 " # SystemId - 8 bytes
72
73BootSectorEntryPoint:
74 #ASSUME ds:@code
75 #ASSUME ss:@code
76
77# ****************************************************************************
78# Start Print
79# ****************************************************************************
80 movw $StartString, %si
81 call PrintString
82
83# ****************************************************************************
84# Print over
85# ****************************************************************************
86
87 movw %cs, %ax # ax = 0
88 movw %ax, %ss # ss = 0
89 addw $0x1000, %ax
90 movw %ax, %ds
91
92 movw $0x7c00, %sp # sp = 0x7c00
93 movw %sp, %bp # bp = 0x7c00
94
95 movb $8, %ah # ah = 8 - Get Drive Parameters Function
96 movb %dl, PhysicalDrive(%bp) # BBS defines that BIOS would pass the booting driver number to the loader through DL
97 int $0x13 # Get Drive Parameters
98 xorw %ax, %ax # ax = 0
99 movb %dh, %al # al = dh
100 incb %al # MaxHead = al + 1
101 pushw %ax # 0000:7bfe = MaxHead
102 movb %cl, %al # al = cl
103 andb $0x3f, %al # MaxSector = al & 0x3f
104 pushw %ax # 0000:7bfc = MaxSector
105
106 cmpw $0xaa55, SectorSignature(%bp) # Verify Boot Sector Signature
107 jne BadBootSector
108 movw RootEntries(%bp), %cx # cx = RootEntries
109 shlw $FAT_DIRECTORY_ENTRY_SHIFT, %cx # cx = cx * 32 = cx * sizeof(FAT_DIRECTORY_ENTRY) = Size of Root Directory in bytes
110 movw %cx, %bx # bx = size of the Root Directory in bytes
111 andw $BLOCK_MASK, %bx # See if it is an even number of sectors long
112 jne BadBootSector # If is isn't, then the boot sector is bad.
113 movw %cx, %bx # bx = size of the Root Directory in bytes
114 shrw $BLOCK_SHIFT, %bx # bx = size of Root Directory in sectors
115 movb NoFats(%bp), %al # al = NoFats
116 xorb %ah, %ah # ah = 0 ==> ax = NoFats
117 mulw SectorsPerFat(%bp) # ax = NoFats * SectorsPerFat
118 addw ReservedSectors(%bp), %ax # ax = NoFats * SectorsPerFat + ReservedSectors = RootLBA
119 pushw %ds
120 popw %es
121 xorw %di, %di # Store directory in es:di = 1000:0000
122 call ReadBlocks # Read entire Root Directory
123 addw %bx, %ax # ax = NoFats * SectorsPerFat + ReservedSectors + RootDirSectors = FirstClusterLBA (FirstDataSector)
124 movw %ax, (%bp) # Save FirstClusterLBA (FirstDataSector) for later use
125
126 # dx - variable storage (initial value is 0)
127 # bx - loader (initial value is 0)
128 xorw %dx, %dx
129 xorw %bx, %bx
130
131FindEFILDR:
132 cmpl $LOADER_FILENAME_PART1, (%di) # Compare to "EFIL"
133 jne FindVARSTORE
134 cmpl $LOADER_FILENAME_PART2, 4(%di)
135 jne FindVARSTORE
136 cmpl $LOADER_FILENAME_PART3, 7(%di)
137 jne FindVARSTORE
138 movw 26(%di), %bx # bx = Start Cluster for EFILDR <----------------------------------
139 testw %dx, %dx
140 je FindNext # Efivar.bin is not loaded
141 jmp FoundAll
142
143FindVARSTORE:
144 ## if the file is not loader file, see if it's "EFIVAR BIN"
145 cmpl $0x56494645, (%di) # Compare to "EFIV"
146 jne FindNext
147 cmpl $0x20205241, 4(%di) # Compare to "AR "
148 jne FindNext
149 cmpl $0x4e494220, 7(%di) # Compare to " BIN"
150 jne FindNext
151 movw %di, %dx # dx = Offset of Start Cluster for Efivar.bin <---------------------
152 addw $26, %dx
153 testw %bx, %bx
154 je FindNext # Efildr is not loaded
155 jmp FoundAll
156
157FindNext:
158 # go to next find
159 addw $FAT_DIRECTORY_ENTRY_SIZE, %di # Increment di
160 subw $FAT_DIRECTORY_ENTRY_SIZE, %cx # Decrement cx
161 # TODO: jump to FindVarStore if ...
162 jne FindEFILDR
163 jmp NotFoundAll
164
165FoundAll:
166FoundEFILDR:
167 movw %bx, %cx # cx = Start Cluster for EFILDR <----------------------------------
168 movw %cs, %ax # Destination = 2000:0000
169 addw $0x2000, %ax
170 movw %ax, %es
171 xorw %di, %di
172ReadFirstClusterOfEFILDR:
173 movw %cx, %ax # ax = StartCluster
174 subw $2, %ax # ax = StartCluster - 2
175 xorb %bh, %bh
176 movb SectorsPerCluster(%bp), %bl # bx = SectorsPerCluster
177 pushw %dx
178 mulw %bx
179 popw %dx # ax = (StartCluster - 2) * SectorsPerCluster
180 addw (%bp), %ax # ax = FirstClusterLBA + (StartCluster-2)*SectorsPerCluster
181 xorb %bh, %bh
182 movb SectorsPerCluster(%bp), %bl # bx = Number of Sectors in a cluster
183 pushw %es
184 call ReadBlocks
185 popw %ax
186JumpIntoFirstSectorOfEFILDR:
187 movw %ax, JumpSegment(%bp)
188JumpFarInstruction:
189 .byte 0xea
190JumpOffset:
191 .word 0x000
192JumpSegment:
193 .word 0x2000
194
195
196PrintString:
197 movw $0xb800, %ax
198 movw %ax, %es
199 movw $0x7c0, %ax
200 movw %ax, %ds
201 movw $7, %cx
202 movw $160, %di
203 rep
204 movsw
205 ret
206# ****************************************************************************
207# ReadBlocks - Reads a set of blocks from a block device
208#
209# AX = Start LBA
210# BX = Number of Blocks to Read
211# ES:DI = Buffer to store sectors read from disk
212# ****************************************************************************
213
214# cx = Blocks
215# bx = NumberOfBlocks
216# si = StartLBA
217
218ReadBlocks:
219 pusha
220 addl LBAOffsetForBootSector(%bp), %eax # Add LBAOffsetForBootSector to Start LBA
221 addl HiddenSectors(%bp), %eax # Add HiddenSectors to Start LBA
222 movl %eax, %esi # esi = Start LBA
223 movw %bx, %cx # cx = Number of blocks to read
224ReadCylinderLoop:
225 movw $0x7bfc, %bp # bp = 0x7bfc
226 movl %esi, %eax # eax = Start LBA
227 xorl %edx, %edx # edx = 0
228 movzwl (%bp), %ebx # bx = MaxSector
229 divl %ebx # ax = StartLBA / MaxSector
230 incw %dx # dx = (StartLBA % MaxSector) + 1
231 subw %dx, %bx # bx = MaxSector - Sector
232 incw %bx # bx = MaxSector - Sector + 1
233 cmpw %bx, %cx # Compare (Blocks) to (MaxSector - Sector + 1)
234 jg LimitTransfer
235 movw %cx, %bx # bx = Blocks
236LimitTransfer:
237 pushw %cx
238 movb %dl, %cl # cl = (StartLBA % MaxSector) + 1 = Sector
239 xorw %dx, %dx # dx = 0
240 divw 2(%bp) # ax = ax / (MaxHead + 1) = Cylinder
241 # dx = ax % (MaxHead + 1) = Head
242
243 pushw %bx # Save number of blocks to transfer
244 movb %dl, %dh # dh = Head
245 movw $0x7c00, %bp # bp = 0x7c00
246 movb PhysicalDrive(%bp), %dl # dl = Drive Number
247 movb %al, %ch # ch = Cylinder
248 movb %bl, %al # al = Blocks
249 movb $2, %ah # ah = Function 2
250 movw %di, %bx # es:bx = Buffer address
251 int $0x13
252 jc DiskError
253 popw %bx
254 popw %cx
255 movzwl %bx, %ebx
256 addl %ebx, %esi # StartLBA = StartLBA + NumberOfBlocks
257 subw %bx, %cx # Blocks = Blocks - NumberOfBlocks
258 movw %es, %ax
259 shlw $(BLOCK_SHIFT-4), %bx
260 addw %bx, %ax
261 movw %ax, %es # es:di = es:di + NumberOfBlocks*BLOCK_SIZE
262 cmpw $0, %cx
263 jne ReadCylinderLoop
264 popa
265 ret
266
267# ****************************************************************************
268# ERROR Condition:
269# ****************************************************************************
270NotFoundAll:
271 ## if we found EFILDR, continue
272 testw %bx, %bx
273 jne FoundEFILDR
274BadBootSector:
275DiskError:
276 movw $ErrorString, %si
277 call PrintString
278Halt:
279 jmp Halt
280
281StartString:
282 .byte 'B', 0x0c, 'S', 0x0c, 't', 0x0c, 'a', 0x0c, 'r', 0x0c, 't', 0x0c, '!', 0x0c
283ErrorString:
284 .byte 'B', 0x0c, 'E', 0x0c, 'r', 0x0c, 'r', 0x0c, 'o', 0x0c, 'r', 0x0c, '!', 0x0c
285
286# ****************************************************************************
287# LBA Offset for BootSector, need patched by tool for HD boot.
288# ****************************************************************************
289
290 .org 0x01fa # Comment it for pass build. Should optimise code size.
291LBAOffsetForBootSector:
292 .long 0x0
293
294# ****************************************************************************
295# Sector Signature
296# ****************************************************************************
297
298 .org 0x01fe # Comment it for pass build.
299SectorSignature:
300 .word 0xaa55 # Boot Sector Signature
301
302
303