DuetPkg/BootSector/start.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 #*    start.S
  13 #*
  14 #*   Abstract:
  15 #*
  16 #------------------------------------------------------------------------------
  17
  18         .stack:
  19         .486p:
  20         .code16
  21
  22 .equ                        FAT_DIRECTORY_ENTRY_SIZE, 0x020
  23 .equ                        FAT_DIRECTORY_ENTRY_SHIFT, 5
  24 .equ                        BLOCK_SIZE, 0x0200
  25 .equ                        BLOCK_MASK, 0x01ff
  26 .equ                        BLOCK_SHIFT, 9
  27
  28        .org 0x0
  29
  30 .global _start
  31 _start:
  32
  33 Ia32Jump:
  34   jmp   BootSectorEntryPoint  # JMP inst    - 3 bytes
  35   nop
  36
  37 OemId:              .ascii   "INTEL   "       # OemId               - 8 bytes
  38
  39 SectorSize:         .word  0                  # Sector Size         - 16 bits
  40 SectorsPerCluster:  .byte  0                  # Sector Per Cluster  - 8 bits
  41 ReservedSectors:    .word  0                  # Reserved Sectors    - 16 bits
  42 NoFats:             .byte  0                  # Number of FATs      - 8 bits
  43 RootEntries:        .word  0                  # Root Entries        - 16 bits
  44 Sectors:            .word  0                  # Number of Sectors   - 16 bits
  45 Media:              .byte  0                  # Media               - 8 bits  - ignored
  46 SectorsPerFat:      .word  0                  # Sectors Per FAT     - 16 bits
  47 SectorsPerTrack:    .word  0                  # Sectors Per Track   - 16 bits - ignored
  48 Heads:              .word  0                  # Heads               - 16 bits - ignored
  49 HiddenSectors:      .long  0                  # Hidden Sectors      - 32 bits - ignored
  50 LargeSectors:       .long  0                  # Large Sectors       - 32 bits
  51 PhysicalDrive:      .byte  0                  # PhysicalDriveNumber - 8 bits  - ignored
  52 CurrentHead:        .byte  0                  # Current Head        - 8 bits
  53 Signature:          .byte  0                  # Signature           - 8 bits  - ignored
  54 VolId:              .ascii "    "             # Volume Serial Number- 4 bytes
  55 FatLabel:           .ascii "           "      # Label               - 11 bytes
  56 SystemId:           .ascii "FAT12   "         # SystemId            - 8 bytes
  57
  58 BootSectorEntryPoint:
  59         #ASSUME ds:@code
  60         #ASSUME ss:@code
  61       # ds = 1000, es = 2000 + x (size of first cluster >> 4)
  62       # cx = Start Cluster of EfiLdr
  63       # dx = Start Cluster of Efivar.bin
  64
  65 # Re use the BPB data stored in Boot Sector
  66         movw    $0x7c00, %bp
  67
  68         pushw   %cx
  69 # Read Efivar.bin
  70 #       1000:dx    = DirectoryEntry of Efivar.bin -> BS.com has filled already
  71         movw    $0x1900, %ax
  72         movw    %ax, %es
  73         testw   %dx, %dx
  74         jnz     CheckVarStoreSize
  75
  76         movb    $1, %al
  77 NoVarStore:
  78         pushw   %es
  79 # Set the 5th byte start @ 0:19000 to non-zero indicating we should init var store header in DxeIpl
  80         movb    %al, %es:(4)
  81         jmp     SaveVolumeId
  82
  83 CheckVarStoreSize:
  84         movw    %dx, %di
  85         cmpl    $0x4000, %ds:2(%di)
  86         movb    $2, %al
  87         jne     NoVarStore
  88
  89 LoadVarStore:
  90         movb    $0, %al
  91         movb    %al, %es:(4)
  92         movw    (%di), %cx
  93 #       ES:DI = 1500:0
  94         xorw    %di, %di
  95         pushw   %es
  96         movw    $0x1500, %ax
  97         movw    %ax, %es
  98         call    ReadFile
  99 SaveVolumeId:
 100         popw    %es
 101         movw    VolId(%bp), %ax
 102         movw    %ax, %es:(0)                    # Save Volume Id to 0:19000. we will find the correct volume according to this VolumeId
 103         movw    VolId+2(%bp), %ax
 104         movw    %ax, %es:(2)
 105
 106 # Read Efildr
 107         popw    %cx
 108 #       cx    = Start Cluster of Efildr -> BS.com has filled already
 109 #       ES:DI = 2000:0, first cluster will be read again
 110         xorw    %di, %di                            # di = 0
 111         movw    $0x2000, %ax
 112         movw    %ax, %es
 113         call    ReadFile
 114         movw    %cs, %ax
 115         movw    %ax, %cs:JumpSegment
 116
 117 JumpFarInstruction:
 118         .byte   0xea
 119 JumpOffset:
 120         .word   0x200
 121 JumpSegment:
 122         .word   0x2000
 123
 124
 125
 126 # ****************************************************************************
 127 # ReadFile
 128 #
 129 # Arguments:
 130 #   CX    = Start Cluster of File
 131 #   ES:DI = Buffer to store file content read from disk
 132 #
 133 # Return:
 134 #   (ES << 4 + DI) = end of file content Buffer
 135 #
 136 # ****************************************************************************
 137 ReadFile:
 138 # si      = NumberOfClusters
 139 # cx      = ClusterNumber
 140 # dx      = CachedFatSectorNumber
 141 # ds:0000 = CacheFatSectorBuffer
 142 # es:di   = Buffer to load file
 143 # bx      = NextClusterNumber
 144         pusha
 145         movw    $1, %si                             # NumberOfClusters = 1
 146         pushw   %cx                                 # Push Start Cluster onto stack
 147         movw    $0xfff, %dx                         # CachedFatSectorNumber = 0xfff
 148 FatChainLoop:
 149         movw    %cx, %ax                            # ax = ClusterNumber
 150         andw    $0xff8, %ax                         # ax = ax & 0xff8
 151         cmpw    $0xff8, %ax                         # See if this is the last cluster
 152         je      FoundLastCluster                    # Jump if last cluster found
 153         movw    %cx, %ax                            # ax = ClusterNumber
 154         shlw    %ax                                 # ax = ClusterNumber * 2
 155         addw    %cx, %ax                            # ax = ClusterNumber * 2 + ClusterNumber = ClusterNumber * 3
 156         shrw    %ax                                 # FatOffset = ClusterNumber*3 / 2
 157         pushw   %si                                 # Save si
 158         movw    %ax, %si                            # si = FatOffset
 159         shrw    $BLOCK_SHIFT, %ax                   # ax = FatOffset >> BLOCK_SHIFT
 160         addw    ReservedSectors(%bp), %ax           # ax = FatSectorNumber = ReservedSectors + (FatOffset >> BLOCK_OFFSET)
 161         andw    $BLOCK_MASK,%si                     # si = FatOffset & BLOCK_MASK
 162         cmpw    %dx, %ax                            # Compare FatSectorNumber to CachedFatSectorNumber
 163         je      SkipFatRead
 164         movw    $2, %bx
 165         pushw   %es
 166         pushw   %ds
 167         popw    %es
 168         call    ReadBlocks                          # Read 2 blocks starting at AX storing at ES:DI
 169         popw    %es
 170         movw    %ax, %dx                            # CachedFatSectorNumber = FatSectorNumber
 171 SkipFatRead:
 172         movw    (%si), %bx                          # bx = NextClusterNumber
 173         movw    %cx, %ax                            # ax = ClusterNumber
 174         andw    $1, %ax                             # See if this is an odd cluster number
 175         je      EvenFatEntry
 176         shrw    $4, %bx                             # NextClusterNumber = NextClusterNumber >> 4
 177 EvenFatEntry:
 178         andw    $0xfff, %bx                         # Strip upper 4 bits of NextClusterNumber
 179         popw    %si                                 # Restore si
 180         decw    %bx                                 # bx = NextClusterNumber - 1
 181         cmpw    %cx, %bx                            # See if (NextClusterNumber-1)==ClusterNumber
 182         jne     ReadClusters
 183         incw    %bx                                 # bx = NextClusterNumber
 184         incw    %si                                 # NumberOfClusters++
 185         movw    %bx, %cx                            # ClusterNumber = NextClusterNumber
 186         jmp     FatChainLoop
 187 ReadClusters:
 188         incw    %bx
 189         popw    %ax                                 # ax = StartCluster
 190         pushw   %bx                                 # StartCluster = NextClusterNumber
 191         movw    %bx, %cx                            # ClusterNumber = NextClusterNumber
 192         subw    $2, %ax                             # ax = StartCluster - 2
 193         xorb    %bh, %bh
 194         movb    SectorsPerCluster(%bp), %bl         # bx = SectorsPerCluster
 195         mulw    %bx                                 # ax = (StartCluster - 2) * SectorsPerCluster
 196         addw    (%bp), %ax                          # ax = FirstClusterLBA + (StartCluster-2)*SectorsPerCluster
 197         pushw   %ax                                 # save start sector
 198         movw    %si, %ax                            # ax = NumberOfClusters
 199         mulw    %bx                                 # ax = NumberOfClusters * SectorsPerCluster
 200         movw    %ax, %bx                            # bx = Number of Sectors
 201         popw    %ax                                 # ax = Start Sector
 202         call    ReadBlocks
 203         movw    $1, %si                             # NumberOfClusters = 1
 204         jmp     FatChainLoop
 205 FoundLastCluster:
 206         popw    %cx
 207         popa
 208         ret
 209
 210
 211 # ****************************************************************************
 212 # ReadBlocks - Reads a set of blocks from a block device
 213 #
 214 # AX    = Start LBA
 215 # BX    = Number of Blocks to Read
 216 # ES:DI = Buffer to store sectors read from disk
 217 # ****************************************************************************
 218
 219 # cx = Blocks
 220 # bx = NumberOfBlocks
 221 # si = StartLBA
 222
 223 ReadBlocks:
 224         pusha
 225         addl    LBAOffsetForBootSector(%bp), %eax   # Add LBAOffsetForBootSector to Start LBA
 226         addl    HiddenSectors(%bp), %eax            # Add HiddenSectors to Start LBA
 227         movl    %eax, %esi                          # esi = Start LBA
 228         movw    %bx, %cx                            # cx = Number of blocks to read
 229 ReadCylinderLoop:
 230         movw    $0x7bfc, %bp                        # bp = 0x7bfc
 231         movl    %esi, %eax                          # eax = Start LBA
 232         xorl    %edx, %edx                          # edx = 0
 233         movzwl  (%bp), %ebx                         # bx = MaxSector
 234         divl    %ebx                                # ax = StartLBA / MaxSector
 235         incw    %dx                                 # dx = (StartLBA % MaxSector) + 1
 236
 237         movw    (%bp), %bx                          # bx = MaxSector
 238         subw    %dx, %bx                            # bx = MaxSector - Sector
 239         incw    %bx                                 # bx = MaxSector - Sector + 1
 240         cmpw    %bx, %cx                            # Compare (Blocks) to (MaxSector - Sector + 1)
 241         jg      LimitTransfer
 242         movw    %cx, %bx                            # bx = Blocks
 243 LimitTransfer:
 244         pushw   %ax                                 # save ax
 245         movw    %es, %ax                            # ax = es
 246         shrw    $(BLOCK_SHIFT-4), %ax               # ax = Number of blocks into mem system
 247         andw    $0x7f, %ax                          # ax = Number of blocks into current seg
 248         addw    %bx, %ax                            # ax = End Block number of transfer
 249         cmpw    $0x80, %ax                          # See if it crosses a 64K boundry
 250         jle     NotCrossing64KBoundry               # Branch if not crossing 64K boundry
 251         subw    $0x80, %ax                          # ax = Number of blocks past 64K boundry
 252         subw    %ax, %bx                            # Decrease transfer size by block overage
 253 NotCrossing64KBoundry:
 254         popw    %ax                                 # restore ax
 255
 256         pushw   %cx
 257         movb    %dl, %cl                            # cl = (StartLBA % MaxSector) + 1 = Sector
 258         xorw    %dx, %dx                            # dx = 0
 259         divw    2(%bp)                              # ax = ax / (MaxHead + 1) = Cylinder
 260                                                     # dx = ax % (MaxHead + 1) = Head
 261
 262         pushw   %bx                                 # Save number of blocks to transfer
 263         movb    %dl, %dh                            # dh = Head
 264         movw    $0x7c00, %bp                        # bp = 0x7c00
 265         movb    PhysicalDrive(%bp), %dl             # dl = Drive Number
 266         movb    %al, %ch                            # ch = Cylinder
 267         movb    %bl, %al                            # al = Blocks
 268         movb    $2, %ah                             # ah = Function 2
 269         movw    %di, %bx                            # es:bx = Buffer address
 270         int     $0x13
 271         jc      DiskError
 272         popw    %bx
 273         popw    %cx
 274         movzwl  %bx, %ebx
 275         addl    %ebx, %esi                          # StartLBA = StartLBA + NumberOfBlocks
 276         subw    %bx, %cx                            # Blocks = Blocks - NumberOfBlocks
 277         movw    %es, %ax
 278         shlw    $(BLOCK_SHIFT-4), %bx
 279         addw    %bx, %ax
 280         movw    %ax, %es                            # es:di = es:di + NumberOfBlocks*BLOCK_SIZE
 281         cmpw    $0, %cx
 282         jne     ReadCylinderLoop
 283         popa
 284         ret
 285
 286 DiskError:
 287         pushw %cs
 288         popw %ds
 289         leaw ErrorString, %si
 290         movw $7, %cx
 291         jmp  PrintStringAndHalt
 292
 293 PrintStringAndHalt:
 294         movw $0xb800, %ax
 295         movw %ax, %es
 296         movw $160, %di
 297         rep
 298         movsw
 299 Halt:
 300         jmp   Halt
 301
 302 ErrorString:
 303         .byte 'S', 0x0c, 'E', 0x0c, 'r', 0x0c, 'r', 0x0c, 'o', 0x0c, 'r', 0x0c, '!',0x0c
 304
 305         .org     0x01fa
 306 LBAOffsetForBootSector:
 307         .long   0x0
 308
 309         .org    0x01fe
 310         .word   0xaa55
 311
 312 #******************************************************************************
 313 #******************************************************************************
 314 #******************************************************************************
 315
 316 .equ                 DELAY_PORT, 0x0ed           # Port to use for 1uS delay
 317 .equ                 KBD_CONTROL_PORT, 0x060     # 8042 control port
 318 .equ                 KBD_STATUS_PORT, 0x064      # 8042 status port
 319 .equ                 WRITE_DATA_PORT_CMD, 0x0d1  # 8042 command to write the data port
 320 .equ                 ENABLE_A20_CMD, 0x0df       # 8042 command to enable A20
 321
 322         .org     0x200
 323         jmp start
 324 Em64String:
 325         .byte 'E', 0x0c, 'm', 0x0c, '6', 0x0c, '4', 0x0c, 'T', 0x0c, ' ', 0x0c, 'U', 0x0c, 'n', 0x0c, 's', 0x0c, 'u', 0x0c, 'p', 0x0c, 'p', 0x0c, 'o', 0x0c, 'r', 0x0c, 't', 0x0c, 'e', 0x0c, 'd', 0x0c, '!', 0x0c
 326
 327 start:
 328         movw %cs, %ax
 329         movw %ax, %ds
 330         movw %ax, %es
 331         movw %ax, %ss
 332         movw $MyStack, %sp
 333
 334 #        mov ax,0b800h
 335 #        mov es,ax
 336 #        mov byte ptr es:[160],'a'
 337 #        mov ax,cs
 338 #        mov es,ax
 339
 340         movl $0, %ebx
 341         leal MemoryMap, %edi
 342 MemMapLoop:
 343         movl $0xe820, %eax
 344         movl $20, %ecx
 345         movl $0x534d4150, %edx  # SMAP
 346         int $0x15
 347         jc  MemMapDone
 348         addl $20, %edi
 349         cmpl $0, %ebx
 350         je  MemMapDone
 351         jmp MemMapLoop
 352 MemMapDone:
 353         leal MemoryMap, %eax
 354         subl %eax, %edi                     # Get the address of the memory map
 355         movl %edi, MemoryMapSize            # Save the size of the memory map
 356
 357         xorl    %ebx, %ebx
 358         movw    %cs, %bx                    # BX=segment
 359         shll    $4, %ebx                    # BX="linear" address of segment base
 360         leal    GDT_BASE(%ebx), %eax        # EAX=PHYSICAL address of gdt
 361         movl    %eax, (gdtr + 2)            # Put address of gdt into the gdtr
 362         leal    IDT_BASE(%ebx), %eax        # EAX=PHYSICAL address of idt
 363         movl    %eax, (idtr + 2)            # Put address of idt into the idtr
 364         leal    MemoryMapSize(%ebx), %edx   # Physical base address of the memory map
 365
 366         addl $0x1000, %ebx                  # Source of EFI32
 367         movl %ebx, JUMP+2
 368         addl $0x1000, %ebx
 369         movl %ebx, %esi                     # Source of EFILDR32
 370
 371 #        mov ax,0b800h
 372 #        mov es,ax
 373 #        mov byte ptr es:[162],'b'
 374 #        mov ax,cs
 375 #        mov es,ax
 376
 377 #
 378 # Enable A20 Gate
 379 #
 380
 381         movw $0x2401, %ax                   # Enable A20 Gate
 382         int $0x15
 383         jnc A20GateEnabled                  # Jump if it suceeded
 384
 385 #
 386 # If INT 15 Function 2401 is not supported, then attempt to Enable A20 manually.
 387 #
 388
 389         call    Empty8042InputBuffer        # Empty the Input Buffer on the 8042 controller
 390         jnz     Timeout8042                 # Jump if the 8042 timed out
 391         outw    %ax, $DELAY_PORT            # Delay 1 uS
 392         mov     $WRITE_DATA_PORT_CMD, %al   # 8042 cmd to write output port
 393         out     %al, $KBD_STATUS_PORT       # Send command to the 8042
 394         call    Empty8042InputBuffer        # Empty the Input Buffer on the 8042 controller
 395         jnz     Timeout8042                 # Jump if the 8042 timed out
 396         mov     $ENABLE_A20_CMD, %al        # gate address bit 20 on
 397         out     %al, $KBD_CONTROL_PORT      # Send command to thre 8042
 398         call    Empty8042InputBuffer        # Empty the Input Buffer on the 8042 controller
 399         movw    $25, %cx                    # Delay 25 uS for the command to complete on the 8042
 400 Delay25uS:
 401         outw    %ax, $DELAY_PORT            # Delay 1 uS
 402         loop    Delay25uS
 403 Timeout8042:
 404
 405
 406 A20GateEnabled:
 407
 408 #
 409 # DISABLE INTERRUPTS - Entering Protected Mode
 410 #
 411
 412         cli
 413
 414 #        mov ax,0b800h
 415 #        mov es,ax
 416 #        mov byte ptr es:[164],'c'
 417 #        mov ax,cs
 418 #        mov es,ax
 419
 420         .byte   0x66
 421         lgdt    gdtr
 422         .byte   0x66
 423         lidt    idtr
 424
 425         movl    %cr0, %eax
 426         orb     $1, %al
 427         movl    %eax, %cr0
 428
 429         movl $0x008, %eax                   # Flat data descriptor
 430         movl $0x00400000, %ebp              # Destination of EFILDR32
 431         movl $0x00070000, %ebx              # Length of copy
 432
 433 JUMP:
 434 # jmp far 0010:00020000
 435         .byte 0x66
 436         .byte 0xea
 437         .long 0x00020000
 438         .word 0x0010
 439
 440 Empty8042InputBuffer:
 441         movw $0, %cx
 442 Empty8042Loop:
 443         outw    %ax, $DELAY_PORT            # Delay 1us
 444         in      $KBD_STATUS_PORT, %al       # Read the 8042 Status Port
 445         andb    $0x2, %al                   # Check the Input Buffer Full Flag
 446         loopnz  Empty8042Loop               # Loop until the input buffer is empty or a timout of 65536 uS
 447         ret
 448
 449 ##############################################################################
 450 # data
 451 ##############################################################################
 452
 453         .p2align 1
 454
 455         gdtr:    .long  GDT_END - GDT_BASE - 1  # GDT limit
 456         .long 0                                 # (GDT base gets set above)
 457 ##############################################################################
 458 #   global descriptor table (GDT)
 459 ##############################################################################
 460
 461         .p2align 1
 462
 463 GDT_BASE:
 464 # null descriptor
 465 .equ                NULL_SEL, .-GDT_BASE
 466         .word 0         # limit 15:0
 467         .word 0         # base 15:0
 468         .byte 0         # base 23:16
 469         .byte 0         # type
 470         .byte 0         # limit 19:16, flags
 471         .byte 0         # base 31:24
 472
 473 # linear data segment descriptor
 474 .equ            LINEAR_SEL, .-GDT_BASE
 475         .word 0xFFFF    # limit 0xFFFFF
 476         .word 0         # base 0
 477         .byte 0
 478         .byte 0x92      # present, ring 0, data, expand-up, writable
 479         .byte 0xCF              # page-granular, 32-bit
 480         .byte 0
 481
 482 # linear code segment descriptor
 483 .equ            LINEAR_CODE_SEL, .-GDT_BASE
 484         .word 0xFFFF    # limit 0xFFFFF
 485         .word 0         # base 0
 486         .byte 0
 487         .byte 0x9A      # present, ring 0, data, expand-up, writable
 488         .byte 0xCF              # page-granular, 32-bit
 489         .byte 0
 490
 491 # system data segment descriptor
 492 .equ            SYS_DATA_SEL, .-GDT_BASE
 493         .word 0xFFFF    # limit 0xFFFFF
 494         .word 0         # base 0
 495         .byte 0
 496         .byte 0x92      # present, ring 0, data, expand-up, writable
 497         .byte 0xCF              # page-granular, 32-bit
 498         .byte 0
 499
 500 # system code segment descriptor
 501 .equ            SYS_CODE_SEL, .-GDT_BASE
 502         .word 0xFFFF    # limit 0xFFFFF
 503         .word 0         # base 0
 504         .byte 0
 505         .byte 0x9A      # present, ring 0, data, expand-up, writable
 506         .byte 0xCF              # page-granular, 32-bit
 507         .byte 0
 508
 509 # spare segment descriptor
 510 .equ        SPARE3_SEL, .-GDT_BASE
 511         .word 0         # limit 0xFFFFF
 512         .word 0         # base 0
 513         .byte 0
 514         .byte 0         # present, ring 0, data, expand-up, writable
 515         .byte 0         # page-granular, 32-bit
 516         .byte 0
 517
 518 # spare segment descriptor
 519 .equ        SPARE4_SEL, .-GDT_BASE
 520         .word 0         # limit 0xFFFFF
 521         .word 0         # base 0
 522         .byte 0
 523         .byte 0         # present, ring 0, data, expand-up, writable
 524         .byte 0         # page-granular, 32-bit
 525         .byte 0
 526
 527 # spare segment descriptor
 528 .equ        SPARE5_SEL, .-GDT_BASE
 529         .word 0         # limit 0xFFFFF
 530         .word 0         # base 0
 531         .byte 0
 532         .byte 0         # present, ring 0, data, expand-up, writable
 533         .byte 0         # page-granular, 32-bit
 534         .byte 0
 535
 536 GDT_END:
 537
 538         .p2align 1
 539
 540
 541
 542 idtr:  .long  IDT_END - IDT_BASE - 1 # IDT limit
 543         .long 0                      # (IDT base gets set above)
 544 ##############################################################################
 545 #   interrupt descriptor table (IDT)
 546 #
 547 #   Note: The hardware IRQ's specified in this table are the normal PC/AT IRQ
 548 #       mappings.  This implementation only uses the system timer and all other
 549 #       IRQs will remain masked.  The descriptors for vectors 33+ are provided
 550 #       for convenience.
 551 ##############################################################################
 552
 553 #idt_tag db "IDT",0
 554         .p2align 1
 555
 556 IDT_BASE:
 557 # divide by zero (INT 0)
 558 .equ                DIV_ZERO_SEL, .-IDT_BASE
 559         .word 0            # offset 15:0
 560         .long SYS_CODE_SEL # selector 15:0
 561         .byte 0            # 0 for interrupt gate
 562         .byte 0x0e | 0x80  # type = 386 interrupt gate, present
 563         .word 0            # offset 31:16
 564
 565 # debug exception (INT 1)
 566 .equ                DEBUG_EXCEPT_SEL, .-IDT_BASE
 567         .word 0            # offset 15:0
 568         .long SYS_CODE_SEL # selector 15:0
 569         .byte 0            # 0 for interrupt gate
 570         .byte 0x0e | 0x80  # type = 386 interrupt gate, present
 571         .word 0            # offset 31:16
 572
 573 # NMI (INT 2)
 574 .equ                NMI_SEL, .-IDT_BASE
 575         .word 0            # offset 15:0
 576         .long SYS_CODE_SEL # selector 15:0
 577         .byte 0            # 0 for interrupt gate
 578         .byte 0x0e |  0x80 # type = 386 interrupt gate, present
 579         .word 0            # offset 31:16
 580
 581 # soft breakpoint (INT 3)
 582 .equ                BREAKPOINT_SEL, .-IDT_BASE
 583         .word 0            # offset 15:0
 584         .long SYS_CODE_SEL # selector 15:0
 585         .byte 0            # 0 for interrupt gate
 586         .byte 0x0e |  0x80 # type = 386 interrupt gate, present
 587         .word 0            # offset 31:16
 588
 589 # overflow (INT 4)
 590 .equ                OVERFLOW_SEL, .-IDT_BASE
 591         .word 0            # offset 15:0
 592         .long SYS_CODE_SEL # selector 15:0
 593         .byte 0            # 0 for interrupt gate
 594         .byte 0x0e |  0x80 # type = 386 interrupt gate, present
 595         .word 0            # offset 31:16
 596
 597 # bounds check (INT 5)
 598 .equ                BOUNDS_CHECK_SEL, .-IDT_BASE
 599         .word 0            # offset 15:0
 600         .long SYS_CODE_SEL # selector 15:0
 601         .byte 0            # 0 for interrupt gate
 602         .byte 0x0e |  0x80 # type = 386 interrupt gate, present
 603         .word 0            # offset 31:16
 604
 605 # invalid opcode (INT 6)
 606 .equ                INVALID_OPCODE_SEL, .-IDT_BASE
 607         .word 0            # offset 15:0
 608         .long SYS_CODE_SEL # selector 15:0
 609         .byte 0            # 0 for interrupt gate
 610         .byte 0x0e |  0x80 # type = 386 interrupt gate, present
 611         .word 0            # offset 31:16
 612
 613 # device not available (INT 7)
 614 .equ                DEV_NOT_AVAIL_SEL, .-IDT_BASE
 615          .word 0            # offset 15:0
 616         .long SYS_CODE_SEL # selector 15:0
 617         .byte 0            # 0 for interrupt gate
 618         .byte 0x0e |  0x80 # type = 386 interrupt gate, present
 619         .word 0            # offset 31:16
 620
 621 # double fault (INT 8)
 622 .equ                DOUBLE_FAULT_SEL, .-IDT_BASE
 623         .word 0            # offset 15:0
 624         .long SYS_CODE_SEL # selector 15:0
 625         .byte 0            # 0 for interrupt gate
 626         .byte 0x0e |  0x80 # type = 386 interrupt gate, present
 627         .word 0            # offset 31:16
 628
 629 # Coprocessor segment overrun - reserved (INT 9)
 630 .equ                RSVD_INTR_SEL1, .-IDT_BASE
 631         .word 0            # offset 15:0
 632         .long SYS_CODE_SEL # selector 15:0
 633         .byte 0            # 0 for interrupt gate
 634         .byte 0x0e |  0x80 # type = 386 interrupt gate, present
 635         .word 0            # offset 31:16
 636
 637 # invalid TSS (INT 0x0a)
 638 .equ                INVALID_TSS_SEL, .-IDT_BASE
 639         .word 0            # offset 15:0
 640         .long SYS_CODE_SEL # selector 15:0
 641         .byte 0            # 0 for interrupt gate
 642         .byte 0x0e |  0x80 # type = 386 interrupt gate, present
 643         .word 0            # offset 31:16
 644
 645 # segment not present (INT 0x0b)
 646 .equ                SEG_NOT_PRESENT_SEL, .-IDT_BASE
 647         .word 0            # offset 15:0
 648         .long SYS_CODE_SEL # selector 15:0
 649         .byte 0            # 0 for interrupt gate
 650         .byte 0x0e |  0x80 # type = 386 interrupt gate, present
 651         .word 0            # offset 31:16
 652
 653 # stack fault (INT 0x0c)
 654 .equ                STACK_FAULT_SEL, .-IDT_BASE
 655         .word 0            # offset 15:0
 656         .long SYS_CODE_SEL # selector 15:0
 657         .byte 0            # 0 for interrupt gate
 658         .byte 0x0e |  0x80 # type = 386 interrupt gate, present
 659         .word 0            # offset 31:16
 660
 661 # general protection (INT 0x0d)
 662 .equ                GP_FAULT_SEL, .-IDT_BASE
 663         .word 0            # offset 15:0
 664         .long SYS_CODE_SEL # selector 15:0
 665         .byte 0            # 0 for interrupt gate
 666         .byte 0x0e |  0x80 # type = 386 interrupt gate, present
 667         .word 0            # offset 31:16
 668
 669 # page fault (INT 0x0e)
 670 .equ                PAGE_FAULT_SEL, .-IDT_BASE
 671         .word 0            # offset 15:0
 672         .long SYS_CODE_SEL # selector 15:0
 673         .byte 0            # 0 for interrupt gate
 674         .byte 0x0e |  0x80 # type = 386 interrupt gate, present
 675         .word 0            # offset 31:16
 676
 677 # Intel reserved - do not use (INT 0x0f)
 678 .equ                RSVD_INTR_SEL2, .-IDT_BASE
 679         .word 0            # offset 15:0
 680         .long SYS_CODE_SEL # selector 15:0
 681         .byte 0            # 0 for interrupt gate
 682         .byte 0x0e |  0x80 # type = 386 interrupt gate, present
 683         .word 0            # offset 31:16
 684
 685 # floating point error (INT 0x10)
 686 .equ                FLT_POINT_ERR_SEL, .-IDT_BASE
 687         .word 0            # offset 15:0
 688         .long SYS_CODE_SEL # selector 15:0
 689         .byte 0            # 0 for interrupt gate
 690         .byte 0x0e |  0x80 # type = 386 interrupt gate, present
 691         .word 0            # offset 31:16
 692
 693 # alignment check (INT 0x11)
 694 .equ                ALIGNMENT_CHECK_SEL, .-IDT_BASE
 695         .word 0            # offset 15:0
 696         .long SYS_CODE_SEL # selector 15:0
 697         .byte 0            # 0 for interrupt gate
 698         .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
 699         .word 0            # offset 31:16
 700
 701 # machine check (INT 0x12)
 702 .equ                MACHINE_CHECK_SEL, .-IDT_BASE
 703         .word 0            # offset 15:0
 704         .long SYS_CODE_SEL # selector 15:0
 705         .byte 0            # 0 for interrupt gate
 706         .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
 707         .word 0            # offset 31:16
 708
 709 # SIMD floating-point exception (INT 0x13)
 710 .equ                SIMD_EXCEPTION_SEL, .-IDT_BASE
 711         .word 0            # offset 15:0
 712         .long SYS_CODE_SEL # selector 15:0
 713         .byte 0            # 0 for interrupt gate
 714         .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
 715         .word 0            # offset 31:16
 716
 717 # 85 unspecified descriptors, First 12 of them are reserved, the rest are avail
 718     .fill 85 * 8, 1, 0   # db (85 * 8) dup(0)
 719
 720 # IRQ 0 (System timer) - (INT 0x68)
 721 .equ                IRQ0_SEL, .-IDT_BASE
 722         .word 0            # offset 15:0
 723         .long SYS_CODE_SEL # selector 15:0
 724         .byte 0            # 0 for interrupt gate
 725         .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
 726         .word 0            # offset 31:16
 727
 728 # IRQ 1 (8042 Keyboard controller) - (INT 0x69)
 729 .equ                IRQ1_SEL, .-IDT_BASE
 730         .word 0            # offset 15:0
 731         .long SYS_CODE_SEL # selector 15:0
 732         .byte 0            # 0 for interrupt gate
 733         .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
 734         .word 0            # offset 31:16
 735
 736 # Reserved - IRQ 2 redirect (IRQ 2) - DO NOT USE!!! - (INT 0x6a)
 737 .equ                IRQ2_SEL, .-IDT_BASE
 738         .word 0            # offset 15:0
 739         .long SYS_CODE_SEL # selector 15:0
 740         .byte 0            # 0 for interrupt gate
 741         .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
 742         .word 0            # offset 31:16
 743
 744 # IRQ 3 (COM 2) - (INT 0x6b)
 745 .equ                IRQ3_SEL, .-IDT_BASE
 746         .word 0            # offset 15:0
 747         .long SYS_CODE_SEL # selector 15:0
 748         .byte 0            # 0 for interrupt gate
 749         .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
 750         .word 0            # offset 31:16
 751
 752 # IRQ 4 (COM 1) - (INT 0x6c)
 753 .equ                IRQ4_SEL, .-IDT_BASE
 754         .word 0            # offset 15:0
 755         .long SYS_CODE_SEL # selector 15:0
 756         .byte 0            # 0 for interrupt gate
 757         .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
 758         .word 0            # offset 31:16
 759
 760 # IRQ 5 (LPT 2) - (INT 0x6d)
 761 .equ                IRQ5_SEL, .-IDT_BASE
 762         .word 0            # offset 15:0
 763         .long SYS_CODE_SEL # selector 15:0
 764         .byte 0            # 0 for interrupt gate
 765         .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
 766         .word 0            # offset 31:16
 767
 768 # IRQ 6 (Floppy controller) - (INT 0x6e)
 769 .equ                IRQ6_SEL, .-IDT_BASE
 770         .word 0            # offset 15:0
 771         .long SYS_CODE_SEL # selector 15:0
 772         .byte 0            # 0 for interrupt gate
 773         .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
 774         .word 0            # offset 31:16
 775
 776 # IRQ 7 (LPT 1) - (INT 0x6f)
 777 .equ                IRQ7_SEL, .-IDT_BASE
 778         .word 0            # offset 15:0
 779         .long SYS_CODE_SEL # selector 15:0
 780         .byte 0            # 0 for interrupt gate
 781         .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
 782         .word 0            # offset 31:16
 783
 784 # IRQ 8 (RTC Alarm) - (INT 0x70)
 785 .equ                IRQ8_SEL, .-IDT_BASE
 786         .word 0            # offset 15:0
 787         .long SYS_CODE_SEL # selector 15:0
 788         .byte 0            # 0 for interrupt gate
 789         .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
 790         .word 0            # offset 31:16
 791
 792 # IRQ 9 - (INT 0x71)
 793 .equ                IRQ9_SEL, .-IDT_BASE
 794         .word 0            # offset 15:0
 795         .long SYS_CODE_SEL # selector 15:0
 796         .byte 0            # 0 for interrupt gate
 797         .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
 798         .word 0            # offset 31:16
 799
 800 # IRQ 10 - (INT 0x72)
 801 .equ                 IRQ10_SEL, .-IDT_BASE
 802         .word 0            # offset 15:0
 803         .long SYS_CODE_SEL # selector 15:0
 804         .byte 0            # 0 for interrupt gate
 805         .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
 806         .word 0            # offset 31:16
 807
 808 # IRQ 11 - (INT 0x73)
 809 .equ                 IRQ11_SEL, .-IDT_BASE
 810         .word 0            # offset 15:0
 811         .long SYS_CODE_SEL # selector 15:0
 812         .byte 0            # 0 for interrupt gate
 813         .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
 814         .word 0            # offset 31:16
 815
 816 # IRQ 12 (PS/2 mouse) - (INT 0x74)
 817 .equ                 IRQ12_SEL, .-IDT_BASE
 818         .word 0            # offset 15:0
 819         .long SYS_CODE_SEL # selector 15:0
 820         .byte 0            # 0 for interrupt gate
 821         .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
 822         .word 0            # offset 31:16
 823
 824 # IRQ 13 (Floating point error) - (INT 0x75)
 825 .equ                 IRQ13_SEL, .-IDT_BASE
 826         .word 0            # offset 15:0
 827         .long SYS_CODE_SEL # selector 15:0
 828         .byte 0            # 0 for interrupt gate
 829         .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
 830         .word 0            # offset 31:16
 831
 832 # IRQ 14 (Secondary IDE) - (INT 0x76)
 833 .equ                 IRQ14_SEL, .-IDT_BASE
 834         .word 0            # offset 15:0
 835         .long SYS_CODE_SEL # selector 15:0
 836         .byte 0            # 0 for interrupt gate
 837         .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
 838         .word 0            # offset 31:16
 839
 840 # IRQ 15 (Primary IDE) - (INT 0x77)
 841 .equ                 IRQ15_SEL, .-IDT_BASE
 842         .word 0            # offset 15:0
 843         .long SYS_CODE_SEL # selector 15:0
 844         .byte 0            # 0 for interrupt gate
 845         .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
 846         .word 0            # offset 31:16
 847
 848 IDT_END:
 849
 850         .p2align 1
 851
 852 MemoryMapSize:  .long 0
 853 MemoryMap:  .long 0,0,0,0,0,0,0,0
 854         .long 0,0,0,0,0,0,0,0
 855         .long 0,0,0,0,0,0,0,0
 856         .long 0,0,0,0,0,0,0,0
 857         .long 0,0,0,0,0,0,0,0
 858         .long 0,0,0,0,0,0,0,0
 859         .long 0,0,0,0,0,0,0,0
 860         .long 0,0,0,0,0,0,0,0
 861         .long 0,0,0,0,0,0,0,0
 862         .long 0,0,0,0,0,0,0,0
 863         .long 0,0,0,0,0,0,0,0
 864         .long 0,0,0,0,0,0,0,0
 865         .long 0,0,0,0,0,0,0,0
 866         .long 0,0,0,0,0,0,0,0
 867         .long 0,0,0,0,0,0,0,0
 868         .long 0,0,0,0,0,0,0,0
 869         .long 0,0,0,0,0,0,0,0
 870         .long 0,0,0,0,0,0,0,0
 871         .long 0,0,0,0,0,0,0,0
 872         .long 0,0,0,0,0,0,0,0
 873         .long 0,0,0,0,0,0,0,0
 874         .long 0,0,0,0,0,0,0,0
 875         .long 0,0,0,0,0,0,0,0
 876         .long 0,0,0,0,0,0,0,0
 877         .long 0,0,0,0,0,0,0,0
 878         .long 0,0,0,0,0,0,0,0
 879         .long 0,0,0,0,0,0,0,0
 880         .long 0,0,0,0,0,0,0,0
 881         .long 0,0,0,0,0,0,0,0
 882         .long 0,0,0,0,0,0,0,0
 883
 884         .long 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
 885         .long 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
 886
 887         .org 0x0fe0
 888 MyStack:
 889         # below is the pieces of the IVT that is used to redirect INT 68h - 6fh
 890         #    back to INT 08h - 0fh  when in real mode...  It is 'org'ed to a
 891         #    known low address (20f00) so it can be set up by PlMapIrqToVect in
 892         #    8259.c
 893
 894         int $8
 895         iret
 896
 897         int $9
 898         iret
 899
 900         int $10
 901         iret
 902
 903         int $11
 904         iret
 905
 906         int $12
 907         iret
 908
 909         int $13
 910         iret
 911
 912         int $14
 913         iret
 914
 915         int $15
 916         iret
 917
 918
 919         .org 0x0ffe
 920 BlockSignature:
 921         .word 0xaa55
 922
 923