DuetPkg/BootSector/bs32.S

   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 #*    bs32.asm
  13 #*
  14 #*   Abstract:
  15 #*
  16 #------------------------------------------------------------------------------
  17
  18         #.MODEL small
  19         .stack:
  20         .486p:
  21         .code16
  22
  23 .equ                      FAT_DIRECTORY_ENTRY_SIZE, 0x0020
  24 .equ                      FAT_DIRECTORY_ENTRY_SHIFT, 5
  25 .equ                      BLOCK_SIZE, 0x0200
  26 .equ                      BLOCK_MASK, 0x01ff
  27 .equ                      BLOCK_SHIFT, 9
  28                                                # "EFILDR_____"
  29 .equ                      LOADER_FILENAME_PART1, 0x4c494645    # "EFIL"
  30 .equ                      LOADER_FILENAME_PART2, 0x30325244    # "DR20"
  31 .equ                      LOADER_FILENAME_PART3, 0x20202030    # "0___"
  32
  33         .org 0x0
  34 .global _start
  35 _start:
  36 Ia32Jump:
  37   jmp   BootSectorEntryPoint  # JMP inst                  - 3 bytes
  38   nop
  39
  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
  54
  55 #******************************************************************************
  56 #
  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.)
  59 #
  60 #******************************************************************************
  61
  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
  75 BootSectorEntryPoint:
  76         #ASSUME ds:@code
  77         #ASSUME ss:@code
  78
  79 # ****************************************************************************
  80 # Start Print
  81 # ****************************************************************************
  82   movw $StartString, %si
  83   call PrintString
  84
  85 # ****************************************************************************
  86 # Print over
  87 # ****************************************************************************
  88
  89   movw  %cs, %ax      # ax = 0
  90   movw  %ax, %ss      # ss = 0
  91   addw  $0x1000, %ax
  92   movw  %ax, %ds
  93
  94   movw  $0x7c00, %sp  # sp = 0x7c00
  95   movw  %sp, %bp      # bp = 0x7c00
  96
  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
 107
 108   cmpw  $0xaa55, SectorSignature(%bp)         # Verify Boot Sector Signature
 109   jne   BadBootSector
 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
 123
 124   movw  RootCluster(%bp), %ax             # ax = StartCluster of Root Directory
 125   subw  $2, %ax                           # ax = StartCluster - 2
 126   xorb  %bh, %bh
 127   movb  SectorsPerCluster(%bp), %bl       # bx = SectorsPerCluster
 128   mulw  %bx                               # ax = (StartCluster - 2) * SectorsPerCluster
 129   addw  (%bp), %ax                        # ax = FirstClusterLBA + (StartCluster-2)*SectorsPerCluster
 130   pushw %ds
 131   popw  %es
 132   xorw  %di, %di                          # Store directory in es:di = 1000:0000
 133   call  ReadBlocks                        # Read StartCluster of Root Directory
 134
 135   # dx - variable storage (initial value is 0)
 136   # bx - loader (initial value is 0)
 137   xorw  %dx, %dx
 138   xorw  %bx, %bx
 139
 140 FindEFILDR:
 141   cmpl  $LOADER_FILENAME_PART1, (%di)
 142   jne   FindVARSTORE
 143   cmpl  $LOADER_FILENAME_PART2, 4(%di)
 144   jne   FindVARSTORE
 145   cmpl  $LOADER_FILENAME_PART3, 7(%di)
 146   jne   FindVARSTORE
 147   movw  26(%di), %bx                      # bx = Start Cluster for EFILDR  <----------------------------------
 148   testw %dx, %dx
 149   je    FindNext                          # Efivar.bin is not loaded
 150   jmp   FoundAll
 151
 152 FindVARSTORE:
 153   ## if the file is not loader file, see if it's "EFIVAR  BIN"
 154   cmpl  $0x56494645, (%di)                # Compare to "EFIV"
 155   jne   FindNext
 156   cmpl  $0x20205241, 4(%di)               # Compare to "AR  "
 157   jne   FindNext
 158   cmpl  $0x4e494220, 7(%di)               # Compare to " BIN"
 159   jne   FindNext
 160   movw  %di, %dx                          # dx = Offset of Start Cluster for Efivar.bin <---------------------
 161   addw  $26, %dx
 162   testw %bx, %bx
 163   je    FindNext                          # Efildr is not loaded
 164   jmp   FoundAll
 165
 166 FindNext:
 167   # go to next find
 168   addw  $FAT_DIRECTORY_ENTRY_SIZE, %di    # Increment di
 169   subw  $FAT_DIRECTORY_ENTRY_SIZE, %cx    # Decrement cx
 170   # TODO: jump to FindVarStore if ...
 171   jne   FindEFILDR
 172   jmp   NotFoundAll
 173
 174 FoundAll:
 175 FoundEFILDR:
 176   movw    %bx, %cx                            # cx = Start Cluster for EFILDR  <----------------------------------
 177   movw    %cs, %ax                            # Destination = 2000:0000
 178   addw    $0x2000, %ax
 179   movw    %ax, %es
 180   xorw    %di, %di
 181 ReadFirstClusterOfEFILDR:
 182   movw    %cx, %ax                            # ax = StartCluster
 183   subw    $2, %ax                             # ax = StartCluster - 2
 184   xorb    %bh, %bh
 185   movb    SectorsPerCluster(%bp), %bl         # bx = SectorsPerCluster
 186   pushw   %dx
 187   mulw    %bx
 188   popw    %dx                                 # ax = (StartCluster - 2) * SectorsPerCluster
 189   addw    (%bp), %ax                          # ax = FirstClusterLBA + (StartCluster-2)*SectorsPerCluster
 190   xorb    %bh, %bh
 191   movb    SectorsPerCluster(%bp), %bl         # bx = Number of Sectors in a cluster
 192   pushw   %es
 193   call    ReadBlocks
 194   popw    %ax
 195 JumpIntoFirstSectorOfEFILDR:
 196   movw    %ax, JumpSegment(%bp)
 197 JumpFarInstruction:
 198   .byte   0xea
 199 JumpOffset:
 200   .word   0x000
 201 JumpSegment:
 202   .word   0x2000
 203
 204
 205 PrintString:
 206   movw $0xb800, %ax
 207   movw %ax, %es
 208   movw $0x7c0, %ax
 209   movw %ax, %ds
 210   movw $7, %cx
 211   movw $160, %di
 212   rep
 213   movsw
 214   ret
 215 # ****************************************************************************
 216 # ReadBlocks - Reads a set of blocks from a block device
 217 #
 218 # AX    = Start LBA
 219 # BX    = Number of Blocks to Read
 220 # ES:DI = Buffer to store sectors read from disk
 221 # ****************************************************************************
 222
 223 # cx = Blocks
 224 # bx = NumberOfBlocks
 225 # si = StartLBA
 226
 227 ReadBlocks:
 228   pusha
 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
 233 ReadCylinderLoop:
 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)
 243   jg      LimitTransfer
 244   movw    %cx, %bx                            # bx = Blocks
 245 LimitTransfer:
 246   pushw   %cx
 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
 251
 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
 260   int     $0x13
 261   jc      DiskError
 262   popw    %bx
 263   popw    %cx
 264   movzwl  %bx, %ebx
 265   addl    %ebx, %esi                          # StartLBA = StartLBA + NumberOfBlocks
 266   subw    %bx, %cx                            # Blocks = Blocks - NumberOfBlocks
 267   movw    %es, %ax
 268   shlw    $(BLOCK_SHIFT-4), %bx
 269   addw    %bx, %ax
 270   movw    %ax, %es                            # es:di = es:di + NumberOfBlocks*BLOCK_SIZE
 271   cmpw    $0, %cx
 272   jne     ReadCylinderLoop
 273   popa
 274   ret
 275
 276 # ****************************************************************************
 277 # ERROR Condition:
 278 # ****************************************************************************
 279 NotFoundAll:
 280   ## if we found EFILDR, continue
 281   testw %bx, %bx
 282   jne  FoundEFILDR
 283 BadBootSector:
 284 DiskError:
 285   movw $ErrorString, %si
 286   call PrintString
 287 Halt:
 288   jmp   Halt
 289
 290 StartString:
 291   .byte 'B', 0x0c, 'S', 0x0c, 't', 0x0c, 'a', 0x0c, 'r', 0x0c, 't', 0x0c, '!', 0x0c
 292 ErrorString:
 293   .byte 'B', 0x0c, 'E', 0x0c, 'r', 0x0c, 'r', 0x0c, 'o', 0x0c, 'r', 0x0c, '!', 0x0c
 294
 295 # ****************************************************************************
 296 # LBA Offset for BootSector, need patched by tool for HD boot.
 297 # ****************************************************************************
 298
 299   #.org 0x01fa
 300 LBAOffsetForBootSector:
 301   .long     0x0
 302
 303 # ****************************************************************************
 304 # Sector Signature
 305 # ****************************************************************************
 306
 307   #.org 0x01fe
 308 SectorSignature:
 309   .word     0xaa55      # Boot Sector Signature
 310
 311
 312