1 #------------------------------------------------------------------------------
3 #* Copyright (c) 2006 - 2012, 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
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.
16 #------------------------------------------------------------------------------
23 .equ FAT_DIRECTORY_ENTRY_SIZE, 0x0020
24 .equ FAT_DIRECTORY_ENTRY_SHIFT, 5
25 .equ BLOCK_SIZE, 0x0200
26 .equ BLOCK_MASK, 0x01ff
29 .equ LOADER_FILENAME_PART1, 0x4c494645 # "EFIL"
30 .equ LOADER_FILENAME_PART2, 0x30325244 # "DR20"
31 .equ LOADER_FILENAME_PART3, 0x20202030 # "0___"
37 jmp BootSectorEntryPoint # JMP inst - 3 bytes
40 OemId: .ascii "INTEL " # OemId - 8 bytes
41 # BPB data below will be fixed by tool
42 SectorSize: .word 0 # Sector Size - 16 bits
43 SectorsPerCluster: .byte 0 # Sector Per Cluster - 8 bits
44 ReservedSectors: .word 0 # Reserved Sectors - 16 bits
45 NoFats: .byte 0 # Number of FATs - 8 bits
46 RootEntries: .word 0 # Root Entries - 16 bits
47 Sectors: .word 0 # Number of Sectors - 16 bits
48 Media: .byte 0 # Media - 8 bits - ignored
49 SectorsPerFat: .word 0 # Sectors Per FAT - 16 bits
50 SectorsPerTrack: .word 0 # Sectors Per Track - 16 bits - ignored
51 Heads: .word 0 # Heads - 16 bits - ignored
52 HiddenSectors: .long 0 # Hidden Sectors - 32 bits - ignored
53 LargeSectors: .long 0 # Large Sectors - 32 bits
55 #******************************************************************************
57 #The structure for FAT32 starting at offset 36 of the boot sector. (At this point,
58 #the BPB/boot sector for FAT12 and FAT16 differs from the BPB/boot sector for FAT32.)
60 #******************************************************************************
62 SectorsPerFat32: .long 0 # Sectors Per FAT for FAT32 - 4 bytes
63 ExtFlags: .word 0 # Mirror Flag - 2 bytes
64 FSVersion: .word 0 # File System Version - 2 bytes
65 RootCluster: .long 0 # 1st Cluster Number of Root Dir - 4 bytes
66 FSInfo: .word 0 # Sector Number of FSINFO - 2 bytes
67 BkBootSector: .word 0 # Sector Number of Bk BootSector - 2 bytes
68 Reserved: .fill 12, 1, 0 # Reserved Field - 12 bytes
69 PhysicalDrive: .byte 0 # Physical Drive Number - 1 byte
70 Reserved1: .byte 0 # Reserved Field - 1 byte
71 Signature: .byte 0 # Extended Boot Signature - 1 byte
72 VolId: .ascii " " # Volume Serial Number - 4 bytes
73 FatLabel: .ascii " " # Volume Label - 11 bytes
74 FileSystemType: .ascii "FAT32 " # File System Type - 8 bytes
79 # ****************************************************************************
81 # ****************************************************************************
82 movw $StartString, %si
85 # ****************************************************************************
87 # ****************************************************************************
89 movw %cs, %ax # ax = 0
90 movw %ax, %ss # ss = 0
94 movw $0x7c00, %sp # sp = 0x7c00
95 movw %sp, %bp # bp = 0x7c00
97 movb $8, %ah # ah = 8 - Get Drive Parameters Function
98 movb %dl, PhysicalDrive(%bp) # BBS defines that BIOS would pass the booting driver number to the loader through DL
99 int $0x13 # Get Drive Parameters
100 xorw %ax, %ax # ax = 0
101 movb %dh, %al # al = dh
102 incb %al # MaxHead = al + 1
103 pushw %ax # 0000:7bfe = MaxHead
104 movb %cl, %al # al = cl
105 andb $0x3f, %al # MaxSector = al & 0x3f
106 pushw %ax # 0000:7bfc = MaxSector
108 cmpw $0xaa55, SectorSignature(%bp) # Verify Boot Sector Signature
110 movw RootEntries(%bp), %cx # cx = RootEntries
111 shlw $FAT_DIRECTORY_ENTRY_SHIFT, %cx # cx = cx * 32 = cx * sizeof(FAT_DIRECTORY_ENTRY) = Size of Root Directory in bytes
112 movw %cx, %bx # bx = size of the Root Directory in bytes
113 andw $BLOCK_MASK, %bx # See if it is an even number of sectors long
114 jne BadBootSector # If is isn't, then the boot sector is bad.
115 movw %cx, %bx # bx = size of the Root Directory in bytes
116 shrw $BLOCK_SHIFT, %bx # bx = size of Root Directory in sectors
117 movb NoFats(%bp), %al # al = NoFats
118 xorb %ah, %ah # ah = 0 ==> ax = NoFats
119 mulw SectorsPerFat32(%bp) # ax = NoFats * SectorsPerFat
120 addw ReservedSectors(%bp), %ax # ax = NoFats * SectorsPerFat + ReservedSectors = RootLBA
121 addw %bx, %ax # ax = NoFats * SectorsPerFat + ReservedSectors + RootDirSectors = FirstClusterLBA
122 movw %ax, (%bp) # Save FirstClusterLBA for later use
124 movw RootCluster(%bp), %ax # ax = StartCluster of Root Directory
125 subw $2, %ax # ax = StartCluster - 2
127 movb SectorsPerCluster(%bp), %bl # bx = SectorsPerCluster
128 mulw %bx # ax = (StartCluster - 2) * SectorsPerCluster
129 addw (%bp), %ax # ax = FirstClusterLBA + (StartCluster-2)*SectorsPerCluster
132 xorw %di, %di # Store directory in es:di = 1000:0000
133 call ReadBlocks # Read StartCluster of Root Directory
135 # dx - variable storage (initial value is 0)
136 # bx - loader (initial value is 0)
141 cmpl $LOADER_FILENAME_PART1, (%di)
143 cmpl $LOADER_FILENAME_PART2, 4(%di)
145 cmpl $LOADER_FILENAME_PART3, 7(%di)
147 movw 26(%di), %bx # bx = Start Cluster for EFILDR <----------------------------------
149 je FindNext # Efivar.bin is not loaded
153 ## if the file is not loader file, see if it's "EFIVAR BIN"
154 cmpl $0x56494645, (%di) # Compare to "EFIV"
156 cmpl $0x20205241, 4(%di) # Compare to "AR "
158 cmpl $0x4e494220, 7(%di) # Compare to " BIN"
160 movw %di, %dx # dx = Offset of Start Cluster for Efivar.bin <---------------------
163 je FindNext # Efildr is not loaded
168 addw $FAT_DIRECTORY_ENTRY_SIZE, %di # Increment di
169 subw $FAT_DIRECTORY_ENTRY_SIZE, %cx # Decrement cx
170 # TODO: jump to FindVarStore if ...
176 movw %bx, %cx # cx = Start Cluster for EFILDR <----------------------------------
177 movw %cs, %ax # Destination = 2000:0000
181 ReadFirstClusterOfEFILDR:
182 movw %cx, %ax # ax = StartCluster
183 subw $2, %ax # ax = StartCluster - 2
185 movb SectorsPerCluster(%bp), %bl # bx = SectorsPerCluster
188 popw %dx # ax = (StartCluster - 2) * SectorsPerCluster
189 addw (%bp), %ax # ax = FirstClusterLBA + (StartCluster-2)*SectorsPerCluster
191 movb SectorsPerCluster(%bp), %bl # bx = Number of Sectors in a cluster
195 JumpIntoFirstSectorOfEFILDR:
196 movw %ax, JumpSegment(%bp)
215 # ****************************************************************************
216 # ReadBlocks - Reads a set of blocks from a block device
219 # BX = Number of Blocks to Read
220 # ES:DI = Buffer to store sectors read from disk
221 # ****************************************************************************
224 # bx = NumberOfBlocks
229 addl LBAOffsetForBootSector(%bp), %eax # Add LBAOffsetForBootSector to Start LBA
230 addl HiddenSectors(%bp), %eax # Add HiddenSectors to Start LBA
231 movl %eax, %esi # esi = Start LBA
232 movw %bx, %cx # cx = Number of blocks to read
234 movw $0x7bfc, %bp # bp = 0x7bfc
235 movl %esi, %eax # eax = Start LBA
236 xorl %edx, %edx # edx = 0
237 movzwl (%bp), %ebx # bx = MaxSector
238 divl %ebx # ax = StartLBA / MaxSector
239 incw %dx # dx = (StartLBA % MaxSector) + 1
240 subw %dx, %bx # bx = MaxSector - Sector
241 incw %bx # bx = MaxSector - Sector + 1
242 cmpw %bx, %cx # Compare (Blocks) to (MaxSector - Sector + 1)
244 movw %cx, %bx # bx = Blocks
247 movb %dl, %cl # cl = (StartLBA % MaxSector) + 1 = Sector
248 xorw %dx, %dx # dx = 0
249 divw 2(%bp) # ax = ax / (MaxHead + 1) = Cylinder
250 # dx = ax % (MaxHead + 1) = Head
252 pushw %bx # Save number of blocks to transfer
253 movb %dl, %dh # dh = Head
254 movw $0x7c00, %bp # bp = 0x7c00
255 movb PhysicalDrive(%bp), %dl # dl = Drive Number
256 movb %al, %ch # ch = Cylinder
257 movb %bl, %al # al = Blocks
258 movb $2, %ah # ah = Function 2
259 movw %di, %bx # es:bx = Buffer address
265 addl %ebx, %esi # StartLBA = StartLBA + NumberOfBlocks
266 subw %bx, %cx # Blocks = Blocks - NumberOfBlocks
268 shlw $(BLOCK_SHIFT-4), %bx
270 movw %ax, %es # es:di = es:di + NumberOfBlocks*BLOCK_SIZE
276 # ****************************************************************************
278 # ****************************************************************************
280 ## if we found EFILDR, continue
285 movw $ErrorString, %si
291 .byte 'B', 0x0c, 'S', 0x0c, 't', 0x0c, 'a', 0x0c, 'r', 0x0c, 't', 0x0c
293 .byte 'B', 0x0c, 'E', 0x0c, 'r', 0x0c, 'r', 0x0c, 'o', 0x0c, 'r', 0x0c
295 # ****************************************************************************
296 # LBA Offset for BootSector, need patched by tool for HD boot.
297 # ****************************************************************************
300 LBAOffsetForBootSector:
303 # ****************************************************************************
305 # ****************************************************************************
309 .word 0xaa55 # Boot Sector Signature