DuetPkg/BootSector/st32_64.S

   1 #------------------------------------------------------------------------------
   2 #*
   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
   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 #*    st32_64.asm
  13 #*
  14 #*   Abstract:
  15 #*
  16 #------------------------------------------------------------------------------
  17
  18
  19         .stack:
  20         .486p:
  21         .code16
  22
  23 .equ                        FAT_DIRECTORY_ENTRY_SIZE, 0x020
  24 .equ                        FAT_DIRECTORY_ENTRY_SHIFT, 5
  25 .equ                        BLOCK_SIZE, 0x0200
  26 .equ                        BLOCK_MASK, 0x01ff
  27 .equ                        BLOCK_SHIFT, 9
  28
  29        .org 0x0
  30
  31 .global _start
  32 _start:
  33
  34 Ia32Jump:
  35   jmp   BootSectorEntryPoint  # JMP inst    - 3 bytes
  36   nop
  37
  38 OemId:               .ascii  "INTEL   "    # OemId                           - 8 bytes
  39 SectorSize:          .word  0              # Sector Size                     - 2 bytes
  40 SectorsPerCluster:   .byte  0              # Sector Per Cluster              - 1 byte
  41 ReservedSectors:     .word  0              # Reserved Sectors                - 2 bytes
  42 NoFats:              .byte  0              # Number of FATs                  - 1 byte
  43 RootEntries:         .word  0              # Root Entries                    - 2 bytes
  44 Sectors:             .word  0              # Number of Sectors               - 2 bytes
  45 Media:               .byte  0              # Media                           - 1 byte
  46 SectorsPerFat16:     .word  0              # Sectors Per FAT for FAT12/FAT16 - 2 byte
  47 SectorsPerTrack:     .word  0              # Sectors Per Track               - 2 bytes
  48 Heads:               .word  0              # Heads                           - 2 bytes
  49 HiddenSectors:       .long  0              # Hidden Sectors                  - 4 bytes
  50 LargeSectors:        .long  0              # Large Sectors                   - 4 bytes
  51
  52 #******************************************************************************
  53 #
  54 #The structure for FAT32 starting at offset 36 of the boot sector. (At this point,
  55 #the BPB/boot sector for FAT12 and FAT16 differs from the BPB/boot sector for FAT32.)
  56 #
  57 #******************************************************************************
  58
  59 SectorsPerFat32:     .long  0              # Sectors Per FAT for FAT32       - 4 bytes
  60 ExtFlags:            .word  0              # Mirror Flag                     - 2 bytes
  61 FSVersion:           .word  0              # File System Version             - 2 bytes
  62 RootCluster:         .long  0              # 1st Cluster Number of Root Dir  - 4 bytes
  63 FSInfo:              .word  0              # Sector Number of FSINFO         - 2 bytes
  64 BkBootSector:        .word  0              # Sector Number of Bk BootSector  - 2 bytes
  65 Reserved:            .fill 12,1,0          # Reserved Field                  - 12 bytes
  66 PhysicalDrive:       .byte  0              # Physical Drive Number           - 1 byte
  67 Reserved1:           .byte  0              # Reserved Field                  - 1 byte
  68 Signature:           .byte  0              # Extended Boot Signature         - 1 byte
  69 VolId:               .ascii  "    "        # Volume Serial Number            - 4 bytes
  70 FatLabel:            .ascii  "           " # Volume Label                    - 11 bytes
  71 FileSystemType:      .ascii  "FAT32   "    # File System Type                - 8 bytes
  72
  73
  74 BootSectorEntryPoint:
  75       # ASSUME  ds:@code
  76       # ASSUME  ss:@code
  77       # ds = 1000, es = 2000 + x (size of first cluster >> 4)
  78       # cx = Start Cluster of EfiLdr
  79       # dx = Start Cluster of Efivar.bin
  80
  81 # Re use the BPB data stored in Boot Sector
  82         movw    $0x7c00,%bp
  83
  84         pushw   %cx
  85 # Read Efivar.bin
  86 #       1000:dx    = DirectoryEntry of Efivar.bin -> BS.com has filled already
  87         movw    $0x1900,%ax
  88         movw    %ax,%es
  89         testw   %dx,%dx
  90         jnz     CheckVarStoreSize
  91
  92         movb    $1,%al
  93 NoVarStore:
  94         pushw   %es
  95 # Set the 5th byte start @ 0:19000 to non-zero indicating we should init var store header in DxeIpl
  96         movb    %al, %es:(4)
  97         jmp     SaveVolumeId
  98
  99 CheckVarStoreSize:
 100         movw    %dx,%di
 101         cmpl    $0x4000, %ds:2(%di)
 102         movb    $2,%al
 103         jne     NoVarStore
 104
 105 LoadVarStore:
 106         movb    $0,%al
 107         movb    %al, %es:(4)
 108         movw    (%di), %cx
 109 #       ES:DI = 1500:0
 110         xorw    %di,%di
 111         pushw   %es
 112         movw    $0x1500,%ax
 113         movw    %ax,%es
 114         call    ReadFile
 115 SaveVolumeId:
 116         popw    %es
 117         movw    VolId(%bp), %ax
 118         movw    %ax, %es:(0)                    # Save Volume Id to 0:19000. we will find the correct volume according to this VolumeId
 119         movw    VolId+2(%bp), %ax
 120         movw    %ax, %es:(2)
 121
 122 # Read Efildr
 123         popw    %cx
 124 #       cx    = Start Cluster of Efildr -> BS.com has filled already
 125 #       ES:DI = 2000:0, first cluster will be read again
 126         xorw    %di,%di                             # di = 0
 127         movw    $0x2000,%ax
 128         movw    %ax,%es
 129         call    ReadFile
 130         movw    %cs,%ax
 131         movw    %ax, %cs:JumpSegment
 132
 133 CheckEm64T:
 134         movl $0x80000001,%eax
 135 #        cpuid
 136         .word 0xA20F
 137         btl  $29,%edx
 138         jc   CheckEm64TPass
 139         pushw %cs
 140         popw %ds
 141         leaw Em64String,%si
 142         movw $18,%cx
 143         jmp  PrintStringAndHalt
 144 CheckEm64TPass:
 145 JumpFarInstruction:
 146         .byte 0xea
 147 JumpOffset:
 148         .word 0x200
 149 JumpSegment:
 150         .word 0x2000
 151
 152
 153
 154 # ****************************************************************************
 155 # ReadFile
 156 #
 157 # Arguments:
 158 #   CX    = Start Cluster of File
 159 #   ES:DI = Buffer to store file content read from disk
 160 #
 161 # Return:
 162 #   (ES << 4 + DI) = end of file content Buffer
 163 #
 164 # ****************************************************************************
 165 ReadFile:
 166 # si      = NumberOfClusters
 167 # cx      = ClusterNumber
 168 # dx      = CachedFatSectorNumber
 169 # ds:0000 = CacheFatSectorBuffer
 170 # es:di   = Buffer to load file
 171 # bx      = NextClusterNumber
 172         pusha
 173         movw    $1,%si                              # NumberOfClusters = 1
 174         pushw   %cx                                 # Push Start Cluster onto stack
 175         movw    $0xfff,%dx                          # CachedFatSectorNumber = 0xfff
 176 FatChainLoop:
 177         movw    %cx,%ax                             # ax = ClusterNumber
 178         andw    $0xfff8,%ax                         # ax = ax & 0xfff8
 179         cmpw    $0xfff8,%ax                         # See if this is the last cluster
 180         je      FoundLastCluster                    # Jump if last cluster found
 181         movw    %cx,%ax                             # ax = ClusterNumber
 182         shlw    $2, %ax                             # FatOffset = ClusterNumber * 2
 183         pushw   %si                                 # Save si
 184         movw    %ax,%si                             # si = FatOffset
 185         shrw    $BLOCK_SHIFT, %ax                   # ax = FatOffset >> BLOCK_SHIFT
 186         addw    ReservedSectors(%bp), %ax           # ax = FatSectorNumber = ReservedSectors + (FatOffset >> BLOCK_OFFSET)
 187         andw    $BLOCK_MASK, %si                    # si = FatOffset & BLOCK_MASK
 188         cmpw    %dx,%ax                             # Compare FatSectorNumber to CachedFatSectorNumber
 189         je      SkipFatRead
 190         movw    $2,%bx
 191         pushw   %es
 192         pushw   %ds
 193         popw    %es
 194         call    ReadBlocks                          # Read 2 blocks starting at AX storing at ES:DI
 195         popw    %es
 196         movw    %ax,%dx                             # CachedFatSectorNumber = FatSectorNumber
 197 SkipFatRead:
 198         movw    (%si), %bx                          # bx = NextClusterNumber
 199         movw    %cx,%ax                             # ax = ClusterNumber
 200         popw    %si                                 # Restore si
 201         decw    %bx                                 # bx = NextClusterNumber - 1
 202         cmpw    %cx,%bx                             # See if (NextClusterNumber-1)==ClusterNumber
 203         jne     ReadClusters
 204         incw    %bx                                 # bx = NextClusterNumber
 205         incw    %si                                 # NumberOfClusters++
 206         movw    %bx,%cx                             # ClusterNumber = NextClusterNumber
 207         jmp     FatChainLoop
 208 ReadClusters:
 209         incw    %bx
 210         popw    %ax                                 # ax = StartCluster
 211         pushw   %bx                                 # StartCluster = NextClusterNumber
 212         movw    %bx,%cx                             # ClusterNumber = NextClusterNumber
 213         subw    $2,%ax                              # ax = StartCluster - 2
 214         xorb    %bh,%bh
 215         movb    SectorsPerCluster(%bp), %bl         # bx = SectorsPerCluster
 216         mulw    %bx                                 # ax = (StartCluster - 2) * SectorsPerCluster
 217         addw    (%bp), %ax                          # ax = FirstClusterLBA + (StartCluster-2)*SectorsPerCluster
 218         pushw   %ax                                 # save start sector
 219         movw    %si,%ax                             # ax = NumberOfClusters
 220         mulw    %bx                                 # ax = NumberOfClusters * SectorsPerCluster
 221         movw    %ax,%bx                             # bx = Number of Sectors
 222         popw    %ax                                 # ax = Start Sector
 223         call    ReadBlocks
 224         movw    $1,%si                              # NumberOfClusters = 1
 225         jmp     FatChainLoop
 226 FoundLastCluster:
 227         popw    %cx
 228         popa
 229         ret
 230
 231
 232 # ****************************************************************************
 233 # ReadBlocks - Reads a set of blocks from a block device
 234 #
 235 # AX    = Start LBA
 236 # BX    = Number of Blocks to Read
 237 # ES:DI = Buffer to store sectors read from disk
 238 # ****************************************************************************
 239
 240 # cx = Blocks
 241 # bx = NumberOfBlocks
 242 # si = StartLBA
 243
 244 ReadBlocks:
 245         pusha
 246         addl    LBAOffsetForBootSector(%bp), %eax   # Add LBAOffsetForBootSector to Start LBA
 247         addl    HiddenSectors(%bp), %eax            # Add HiddenSectors to Start LBA
 248         movl    %eax,%esi                           # esi = Start LBA
 249         movw    %bx,%cx                             # cx = Number of blocks to read
 250 ReadCylinderLoop:
 251         movw    $0x7bfc,%bp                         # bp = 0x7bfc
 252         movl    %esi,%eax                           # eax = Start LBA
 253         xorl    %edx,%edx                           # edx = 0
 254         movzwl  (%bp), %ebx                         # bx = MaxSector
 255         divl    %ebx                                # ax = StartLBA / MaxSector
 256         incw    %dx                                 # dx = (StartLBA % MaxSector) + 1
 257
 258         movw    (%bp), %bx                          # bx = MaxSector
 259         subw    %dx,%bx                             # bx = MaxSector - Sector
 260         incw    %bx                                 # bx = MaxSector - Sector + 1
 261         cmpw    %bx,%cx                             # Compare (Blocks) to (MaxSector - Sector + 1)
 262         jg      LimitTransfer
 263         movw    %cx,%bx                             # bx = Blocks
 264 LimitTransfer:
 265         pushw   %ax                                 # save ax
 266         movw    %es,%ax                             # ax = es
 267         shrw    $(BLOCK_SHIFT-4), %ax               # ax = Number of blocks into mem system
 268         andw    $0x7f,%ax                           # ax = Number of blocks into current seg
 269         addw    %bx,%ax                             # ax = End Block number of transfer
 270         cmpw    $0x80,%ax                           # See if it crosses a 64K boundry
 271         jle     NotCrossing64KBoundry               # Branch if not crossing 64K boundry
 272         subw    $0x80,%ax                           # ax = Number of blocks past 64K boundry
 273         subw    %ax,%bx                             # Decrease transfer size by block overage
 274 NotCrossing64KBoundry:
 275         popw    %ax                                 # restore ax
 276
 277         pushw   %cx
 278         movb    %dl,%cl                             # cl = (StartLBA % MaxSector) + 1 = Sector
 279         xorw    %dx,%dx                             # dx = 0
 280         divw    2(%bp)                              # ax = ax / (MaxHead + 1) = Cylinder
 281                                                     # dx = ax % (MaxHead + 1) = Head
 282
 283         pushw   %bx                                 # Save number of blocks to transfer
 284         movb    %dl,%dh                             # dh = Head
 285         movw    $0x7c00,%bp                         # bp = 0x7c00
 286         movb    PhysicalDrive(%bp), %dl             # dl = Drive Number
 287         movb    %al,%ch                             # ch = Cylinder
 288         movb    %bl,%al                             # al = Blocks
 289         movb    $2,%ah                              # ah = Function 2
 290         movw    %di,%bx                             # es:bx = Buffer address
 291         int     $0x13
 292         jc      DiskError
 293         popw    %bx
 294         popw    %cx
 295         movzwl  %bx,%ebx
 296         addl    %ebx,%esi                           # StartLBA = StartLBA + NumberOfBlocks
 297         subw    %bx,%cx                             # Blocks = Blocks - NumberOfBlocks
 298         movw    %es,%ax
 299         shlw    $(BLOCK_SHIFT-4), %bx
 300         addw    %bx,%ax
 301         movw    %ax,%es                             # es:di = es:di + NumberOfBlocks*BLOCK_SIZE
 302         cmpw    $0,%cx
 303         jne     ReadCylinderLoop
 304         popa
 305         ret
 306
 307 DiskError:
 308         pushw %cs
 309         popw %ds
 310         leaw ErrorString,%si
 311         movw $7,%cx
 312         jmp  PrintStringAndHalt
 313
 314 PrintStringAndHalt:
 315         movw $0xb800,%ax
 316         movw %ax,%es
 317         movw $160,%di
 318         rep
 319         movsw
 320 Halt:
 321         jmp   Halt
 322
 323 ErrorString:
 324         .byte 'S', 0x0c, 'E', 0x0c, 'r', 0x0c, 'r', 0x0c, 'o', 0x0c, 'r', 0x0c, '!',0x0c
 325
 326         .org     0x01fa
 327 LBAOffsetForBootSector:
 328         .long 0x0
 329
 330         .org    0x01fe
 331         .word 0xaa55
 332
 333 #******************************************************************************
 334 #******************************************************************************
 335 #******************************************************************************
 336
 337 .equ                 DELAY_PORT, 0x0ed # Port to use for 1uS delay
 338 .equ                 KBD_CONTROL_PORT, 0x060 # 8042 control port
 339 .equ                 KBD_STATUS_PORT, 0x064 # 8042 status port
 340 .equ                 WRITE_DATA_PORT_CMD, 0x0d1 # 8042 command to write the data port
 341 .equ                 ENABLE_A20_CMD, 0x0df # 8042 command to enable A20
 342
 343         .org     0x200
 344         jmp start
 345 Em64String:
 346 .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
 347
 348 start:
 349         movw %cs,%ax
 350         movw %ax,%ds
 351         movw %ax,%es
 352         movw %ax,%ss
 353         movw $MyStack, %sp
 354
 355 #        mov ax,0b800h
 356 #        mov es,ax
 357 #        mov byte ptr es:[160],'a'
 358 #        mov ax,cs
 359 #        mov es,ax
 360
 361         movl $0,%ebx
 362         leal MemoryMap, %edi
 363 MemMapLoop:
 364         movl $0xe820,%eax
 365         movl $20,%ecx
 366         movl $0x534d4150, %edx  # SMAP
 367         int $0x15
 368         jc  MemMapDone
 369         addl $20,%edi
 370         cmpl $0,%ebx
 371         je  MemMapDone
 372         jmp MemMapLoop
 373 MemMapDone:
 374         leal MemoryMap, %eax
 375         subl %eax,%edi                      # Get the address of the memory map
 376         movl %edi, MemoryMapSize            # Save the size of the memory map
 377
 378         xorl    %ebx,%ebx
 379         movw    %cs,%bx                     # BX=segment
 380         shll    $4,%ebx                     # BX="linear" address of segment base
 381         leal    GDT_BASE(%ebx), %eax        # EAX=PHYSICAL address of gdt
 382         movl    %eax, (gdtr + 2)            # Put address of gdt into the gdtr
 383         leal    IDT_BASE(%ebx), %eax        # EAX=PHYSICAL address of idt
 384         movl    %eax, (idtr + 2)            # Put address of idt into the idtr
 385         leal    MemoryMapSize(%ebx), %edx   # Physical base address of the memory map
 386
 387 #        mov ax,0b800h
 388 #        mov es,ax
 389 #        mov byte ptr es:[162],'b'
 390 #        mov ax,cs
 391 #        mov es,ax
 392
 393 #
 394 # Enable A20 Gate
 395 #
 396
 397         movw $0x2401,%ax                    # Enable A20 Gate
 398         int $0x15
 399         jnc A20GateEnabled                  # Jump if it suceeded
 400
 401 #
 402 # If INT 15 Function 2401 is not supported, then attempt to Enable A20 manually.
 403 #
 404
 405         call    Empty8042InputBuffer        # Empty the Input Buffer on the 8042 controller
 406         jnz     Timeout8042                 # Jump if the 8042 timed out
 407         outw    %ax, $DELAY_PORT            # Delay 1 uS
 408         movb    $WRITE_DATA_PORT_CMD, %al   # 8042 cmd to write output port
 409         outb    %al, $KBD_STATUS_PORT       # Send command to the 8042
 410         call    Empty8042InputBuffer        # Empty the Input Buffer on the 8042 controller
 411         jnz     Timeout8042                 # Jump if the 8042 timed out
 412         movb    $ENABLE_A20_CMD, %al        # gate address bit 20 on
 413         outb    %al, $KBD_CONTROL_PORT      # Send command to thre 8042
 414         call    Empty8042InputBuffer        # Empty the Input Buffer on the 8042 controller
 415         movw    $25,%cx                     # Delay 25 uS for the command to complete on the 8042
 416 Delay25uS:
 417         outw    %ax, $DELAY_PORT            # Delay 1 uS
 418         loop    Delay25uS
 419 Timeout8042:
 420
 421
 422 A20GateEnabled:
 423
 424 #
 425 # DISABLE INTERRUPTS - Entering Protected Mode
 426 #
 427
 428         cli
 429
 430 #        mov ax,0b800h
 431 #        mov es,ax
 432 #        mov byte ptr es:[164],'c'
 433 #        mov ax,cs
 434 #        mov es,ax
 435
 436     leal OffsetIn32BitProtectedMode, %eax
 437     addl $0x20000+0x6,%eax
 438     movl %eax, OffsetIn32BitProtectedMode
 439
 440     leal OffsetInLongMode, %eax
 441     addl $0x20000+0x6,%eax
 442     movl %eax, OffsetInLongMode
 443
 444     #
 445     # load GDT
 446     #
 447     .byte 0x66
 448     lgdt    gdtr
 449
 450     #
 451     # Enable Protect Mode (set CR0.PE=1)
 452     #
 453     movl  %cr0, %eax      # Read CR0.
 454     orl   $0x1,%eax       # Set PE=1
 455     movl  %eax, %cr0      # Write CR0.
 456     .byte 0x66
 457     .byte 0xea                        # jmp far 16:32
 458 OffsetIn32BitProtectedMode:
 459     .long 0x0000000                   # offset $+8   (In32BitProtectedMode)
 460     .word 0x10                        # selector  (flat CS)
 461 In32BitProtectedMode:
 462
 463 #
 464 # Entering Long Mode
 465 #
 466     .byte 0x66
 467     movw $8,%ax
 468     movw %ax,%ds
 469     movw %ax,%es
 470     movw %ax,%ss
 471
 472     #
 473     # Enable the 64-bit page-translation-table entries by
 474     # setting CR4.PAE=1 (this is _required_ before activating
 475     # long mode). Paging is not enabled until after long mode
 476     # is enabled.
 477     #
 478     .byte 0xf
 479     .byte 0x20
 480     .byte 0xe0
 481 #    mov eax, cr4
 482     btsl $5,%eax
 483     .byte 0xf
 484     .byte 0x22
 485     .byte 0xe0
 486 #    mov cr4, eax
 487
 488     #
 489     # This is the Trapolean Page Tables that are guarenteed
 490     #  under 4GB.
 491     #
 492     # Address Map:
 493     #    10000 ~    12000 - efildr (loaded)
 494     #    20000 ~    21000 - start64.com
 495     #    21000 ~    22000 - efi64.com
 496     #    22000 ~    90000 - efildr
 497     #    90000 ~    96000 - 4G pagetable (will be reload later)
 498     #
 499     .byte 0xb8
 500     .long 0x90000
 501 #    mov eax, 90000h
 502     movl %eax, %cr3
 503
 504     #
 505     # Enable long mode (set EFER.LME=1).
 506     #
 507     .byte 0xb9
 508     .long 0xc0000080
 509 #    mov   ecx, 0c0000080h ; EFER MSR number.
 510     .byte 0xf
 511     .byte 0x32
 512 #    rdmsr                 ; Read EFER.
 513     .byte 0xf
 514     .byte 0xba
 515     .byte 0xe8
 516     .byte 0x8
 517 #    bts   eax, 8          ; Set LME=1.
 518     .byte 0xf
 519     .byte 0x30
 520 #    wrmsr                 ; Write EFER.
 521
 522     #
 523     # Enable paging to activate long mode (set CR0.PG=1)
 524     #
 525     movl  %cr0, %eax      # Read CR0.
 526     .byte 0xf
 527     .byte 0xba
 528     .byte 0xe8
 529     .byte 0x1f
 530 #    bts   eax, 31         ; Set PG=1.
 531     movl  %eax, %cr0      # Write CR0.
 532     jmp   GoToLongMode
 533 GoToLongMode:
 534
 535     .byte 0x67
 536     .byte 0xea                  # Far Jump $+9:Selector to reload CS
 537 OffsetInLongMode:
 538     .long 00000000              #   $+9 Offset is ensuing instruction boundary
 539     .word 0x38                  #   Selector is our code selector, 38h
 540
 541 InLongMode:
 542     .byte 0x66
 543     movw    $0x30,%ax
 544     movw    %ax,%ds
 545
 546     .byte 0x66
 547     movw    $0x18,%ax
 548     movw    %ax,%es
 549     movw    %ax,%ss
 550     movw    %ax,%ds
 551
 552     .byte 0xbd
 553     .long 0x400000
 554 #    mov ebp,000400000h                  ; Destination of EFILDR32
 555     .byte 0xbb
 556     .long 0x70000
 557 #    mov ebx,000070000h                  ; Length of copy
 558
 559     #
 560     # load idt later
 561     #
 562     .byte 0x48
 563     .byte 0x33
 564     .byte 0xc0
 565 #    xor rax, rax
 566     .byte 0x66
 567      movw $idtr, %ax
 568     .byte 0x48
 569     .byte 0x5
 570     .long 0x20000
 571 #    add rax, 20000h
 572
 573     .byte 0xf
 574     .byte 0x1
 575     .byte 0x18
 576 #    lidt    fword ptr [rax]
 577
 578     .byte 0x48
 579     .byte 0xc7
 580     .byte 0xc0
 581     .long 0x21000
 582 #   mov rax, 21000h
 583     .byte 0x50
 584 #   push rax
 585
 586 # ret
 587     .byte 0xc3
 588
 589 Empty8042InputBuffer:
 590         movw $0,%cx
 591 Empty8042Loop:
 592         outw    %ax, $DELAY_PORT            # Delay 1us
 593         inb     $KBD_STATUS_PORT, %al       # Read the 8042 Status Port
 594         andb    $0x2,%al                    # Check the Input Buffer Full Flag
 595         loopnz  Empty8042Loop               # Loop until the input buffer is empty or a timout of 65536 uS
 596         ret
 597
 598 ##############################################################################
 599 # data
 600 ##############################################################################
 601
 602         .p2align 1
 603
 604         gdtr:    .word  GDT_END - GDT_BASE - 1  # GDT limit
 605         .long 0                     # (GDT base gets set above)
 606 ##############################################################################
 607 #   global descriptor table (GDT)
 608 ##############################################################################
 609
 610         .p2align 1
 611
 612 GDT_BASE:
 613 # null descriptor
 614 .equ                NULL_SEL, .-GDT_BASE    # Selector [0x0]
 615         .word 0         # limit 15:0
 616         .word 0         # base 15:0
 617         .byte 0         # base 23:16
 618         .byte 0         # type
 619         .byte 0         # limit 19:16, flags
 620         .byte 0         # base 31:24
 621
 622 # linear data segment descriptor
 623 .equ            LINEAR_SEL, .-GDT_BASE  # Selector [0x8]
 624         .word 0xFFFF    # limit 0xFFFFF
 625         .word 0         # base 0
 626         .byte 0
 627         .byte 0x92      # present, ring 0, data, expand-up, writable
 628         .byte 0xCF              # page-granular, 32-bit
 629         .byte 0
 630
 631 # linear code segment descriptor
 632 .equ            LINEAR_CODE_SEL, .-GDT_BASE # Selector [0x10]
 633         .word 0xFFFF    # limit 0xFFFFF
 634         .word 0         # base 0
 635         .byte 0
 636         .byte 0x9A      # present, ring 0, data, expand-up, writable
 637         .byte 0xCF              # page-granular, 32-bit
 638         .byte 0
 639
 640 # system data segment descriptor
 641 .equ            SYS_DATA_SEL, .-GDT_BASE # Selector [0x18]
 642         .word 0xFFFF    # limit 0xFFFFF
 643         .word 0         # base 0
 644         .byte 0
 645         .byte 0x92      # present, ring 0, data, expand-up, writable
 646         .byte 0xCF              # page-granular, 32-bit
 647         .byte 0
 648
 649 # system code segment descriptor
 650 .equ            SYS_CODE_SEL, .-GDT_BASE # Selector [0x20]
 651         .word 0xFFFF    # limit 0xFFFFF
 652         .word 0         # base 0
 653         .byte 0
 654         .byte 0x9A      # present, ring 0, data, expand-up, writable
 655         .byte 0xCF              # page-granular, 32-bit
 656         .byte 0
 657
 658 # spare segment descriptor
 659 .equ        SPARE3_SEL, .-GDT_BASE  # Selector [0x28]
 660         .word 0         # limit 0xFFFFF
 661         .word 0         # base 0
 662         .byte 0
 663         .byte 0         # present, ring 0, data, expand-up, writable
 664         .byte 0         # page-granular, 32-bit
 665         .byte 0
 666
 667 #
 668 # system data segment descriptor
 669 #
 670 .equ              SYS_DATA64_SEL, .-GDT_BASE # Selector [0x30]
 671         .word 0xFFFF    # limit 0xFFFFF
 672         .word 0         # base 0
 673         .byte 0
 674         .byte 0x92      # P | DPL [1..2] | 1   | 1   | C | R | A
 675         .byte 0xCF      # G | D   | L    | AVL | Segment [19..16]
 676         .byte 0
 677
 678 #
 679 # system code segment descriptor
 680 #
 681 .equ              SYS_CODE64_SEL, .-GDT_BASE # Selector [0x38]
 682         .word 0xFFFF    # limit 0xFFFFF
 683         .word 0         # base 0
 684         .byte 0
 685         .byte 0x9A      # P | DPL [1..2] | 1   | 1   | C | R | A
 686         .byte 0xAF      # G | D   | L    | AVL | Segment [19..16]
 687         .byte 0
 688
 689 # spare segment descriptor
 690 .equ        SPARE4_SEL, .-GDT_BASE    # Selector [0x40]
 691         .word 0         # limit 0xFFFFF
 692         .word 0         # base 0
 693         .byte 0
 694         .byte 0         # present, ring 0, data, expand-up, writable
 695         .byte 0         # page-granular, 32-bit
 696         .byte 0
 697
 698 GDT_END:
 699
 700         .p2align 1
 701
 702
 703
 704 idtr:   .long  IDT_END - IDT_BASE - 1 # IDT limit
 705         .quad 0                     # (IDT base gets set above)
 706
 707 ##############################################################################
 708 #   interrupt descriptor table (IDT)
 709 #
 710 #   Note: The hardware IRQ's specified in this table are the normal PC/AT IRQ
 711 #       mappings.  This implementation only uses the system timer and all other
 712 #       IRQs will remain masked.  The descriptors for vectors 33+ are provided
 713 #       for convenience.
 714 ##############################################################################
 715
 716 #idt_tag db "IDT",0
 717         .p2align 1
 718
 719
 720 IDT_BASE:
 721 # divide by zero (INT 0)
 722 .equ                DIV_ZERO_SEL, .-IDT_BASE
 723         .word 0               # offset 15:0
 724         .long SYS_CODE64_SEL  # selector 15:0
 725         .byte 0               # 0 for interrupt gate
 726         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 727         .word 0               # offset 31:16
 728         .long 0               # offset 63:32
 729         .long 0               # 0 for reserved
 730
 731 # debug exception (INT 1)
 732 .equ                DEBUG_EXCEPT_SEL, .-IDT_BASE
 733         .word 0               # offset 15:0
 734         .long SYS_CODE64_SEL  # selector 15:0
 735         .byte 0               # 0 for interrupt gate
 736         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 737         .word 0               # offset 31:16
 738         .long 0               # offset 63:32
 739         .long 0               # 0 for reserved
 740
 741 # NMI (INT 2)
 742 .equ                NMI_SEL, .-IDT_BASE
 743         .word 0               # offset 15:0
 744         .long SYS_CODE64_SEL  # selector 15:0
 745         .byte 0               # 0 for interrupt gate
 746         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 747         .word 0               # offset 31:16
 748         .long 0               # offset 63:32
 749         .long 0               # 0 for reserved
 750
 751 # soft breakpoint (INT 3)
 752 .equ                BREAKPOINT_SEL, .-IDT_BASE
 753         .word 0               # offset 15:0
 754         .long SYS_CODE64_SEL  # selector 15:0
 755         .byte 0               # 0 for interrupt gate
 756         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 757         .word 0               # offset 31:16
 758         .long 0               # offset 63:32
 759         .long 0               # 0 for reserved
 760
 761 # overflow (INT 4)
 762 .equ                OVERFLOW_SEL, .-IDT_BASE
 763         .word 0               # offset 15:0
 764         .long SYS_CODE64_SEL  # selector 15:0
 765         .byte 0               # 0 for interrupt gate
 766         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 767         .word 0               # offset 31:16
 768         .long 0               # offset 63:32
 769         .long 0               # 0 for reserved
 770
 771 # bounds check (INT 5)
 772 .equ                BOUNDS_CHECK_SEL, .-IDT_BASE
 773         .word 0               # offset 15:0
 774         .long SYS_CODE64_SEL  # selector 15:0
 775         .byte 0               # 0 for interrupt gate
 776         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 777         .word 0               # offset 31:16
 778         .long 0               # offset 63:32
 779         .long 0               # 0 for reserved
 780
 781 # invalid opcode (INT 6)
 782 .equ                INVALID_OPCODE_SEL, .-IDT_BASE
 783         .word 0               # offset 15:0
 784         .long SYS_CODE64_SEL  # selector 15:0
 785         .byte 0               # 0 for interrupt gate
 786         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 787         .word 0               # offset 31:16
 788         .long 0               # offset 63:32
 789         .long 0               # 0 for reserved
 790
 791 # device not available (INT 7)
 792 .equ                DEV_NOT_AVAIL_SEL, .-IDT_BASE
 793         .word 0               # offset 15:0
 794         .long SYS_CODE64_SEL  # selector 15:0
 795         .byte 0               # 0 for interrupt gate
 796         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 797         .word 0               # offset 31:16
 798         .long 0               # offset 63:32
 799         .long 0               # 0 for reserved
 800
 801 # double fault (INT 8)
 802 .equ                DOUBLE_FAULT_SEL, .-IDT_BASE
 803         .word 0               # offset 15:0
 804         .long SYS_CODE64_SEL  # selector 15:0
 805         .byte 0               # 0 for interrupt gate
 806         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 807         .word 0               # offset 31:16
 808         .long 0               # offset 63:32
 809         .long 0               # 0 for reserved
 810
 811 # Coprocessor segment overrun - reserved (INT 9)
 812 .equ                RSVD_INTR_SEL1, .-IDT_BASE
 813         .word 0               # offset 15:0
 814         .long SYS_CODE64_SEL  # selector 15:0
 815         .byte 0               # 0 for interrupt gate
 816         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 817         .word 0               # offset 31:16
 818         .long 0               # offset 63:32
 819         .long 0               # 0 for reserved
 820
 821 # invalid TSS (INT 0ah)
 822 .equ                INVALID_TSS_SEL, .-IDT_BASE
 823         .word 0               # offset 15:0
 824         .long SYS_CODE64_SEL  # selector 15:0
 825         .byte 0               # 0 for interrupt gate
 826         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 827         .word 0               # offset 31:16
 828         .long 0               # offset 63:32
 829         .long 0               # 0 for reserved
 830
 831 # segment not present (INT 0bh)
 832 .equ                SEG_NOT_PRESENT_SEL, .-IDT_BASE
 833         .word 0               # offset 15:0
 834         .long SYS_CODE64_SEL  # selector 15:0
 835         .byte 0               # 0 for interrupt gate
 836         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 837         .word 0               # offset 31:16
 838         .long 0               # offset 63:32
 839         .long 0               # 0 for reserved
 840
 841 # stack fault (INT 0ch)
 842 .equ                STACK_FAULT_SEL, .-IDT_BASE
 843         .word 0               # offset 15:0
 844         .long SYS_CODE64_SEL  # selector 15:0
 845         .byte 0               # 0 for interrupt gate
 846         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 847         .word 0               # offset 31:16
 848         .long 0               # offset 63:32
 849         .long 0               # 0 for reserved
 850
 851 # general protection (INT 0dh)
 852 .equ                GP_FAULT_SEL, .-IDT_BASE
 853         .word 0               # offset 15:0
 854         .long SYS_CODE64_SEL  # selector 15:0
 855         .byte 0               # 0 for interrupt gate
 856         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 857         .word 0               # offset 31:16
 858         .long 0               # offset 63:32
 859         .long 0               # 0 for reserved
 860
 861 # page fault (INT 0eh)
 862 .equ                PAGE_FAULT_SEL, .-IDT_BASE
 863         .word 0               # offset 15:0
 864         .long SYS_CODE64_SEL  # selector 15:0
 865         .byte 0               # 0 for interrupt gate
 866         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 867         .word 0               # offset 31:16
 868         .long 0               # offset 63:32
 869         .long 0               # 0 for reserved
 870
 871 # Intel reserved - do not use (INT 0fh)
 872 .equ                RSVD_INTR_SEL2, .-IDT_BASE
 873         .word 0               # offset 15:0
 874         .long SYS_CODE64_SEL  # selector 15:0
 875         .byte 0               # 0 for interrupt gate
 876         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 877         .word 0               # offset 31:16
 878         .long 0               # offset 63:32
 879         .long 0               # 0 for reserved
 880
 881 # floating point error (INT 10h)
 882 .equ                FLT_POINT_ERR_SEL, .-IDT_BASE
 883         .word 0               # offset 15:0
 884         .long SYS_CODE64_SEL  # selector 15:0
 885         .byte 0               # 0 for interrupt gate
 886         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 887         .word 0               # offset 31:16
 888         .long 0               # offset 63:32
 889         .long 0               # 0 for reserved
 890
 891 # alignment check (INT 11h)
 892 .equ                ALIGNMENT_CHECK_SEL, .-IDT_BASE
 893         .word 0               # offset 15:0
 894         .long SYS_CODE64_SEL  # selector 15:0
 895         .byte 0               # 0 for interrupt gate
 896         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 897         .word 0               # offset 31:16
 898         .long 0               # offset 63:32
 899         .long 0               # 0 for reserved
 900
 901 # machine check (INT 12h)
 902 .equ                MACHINE_CHECK_SEL, .-IDT_BASE
 903         .word 0               # offset 15:0
 904         .long SYS_CODE64_SEL  # selector 15:0
 905         .byte 0               # 0 for interrupt gate
 906         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 907         .word 0               # offset 31:16
 908         .long 0               # offset 63:32
 909         .long 0               # 0 for reserved
 910
 911 # SIMD floating-point exception (INT 13h)
 912 .equ                SIMD_EXCEPTION_SEL, .-IDT_BASE
 913         .word 0               # offset 15:0
 914         .long SYS_CODE64_SEL  # selector 15:0
 915         .byte 0               # 0 for interrupt gate
 916         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 917         .word 0               # offset 31:16
 918         .long 0               # offset 63:32
 919         .long 0               # 0 for reserved
 920
 921 # 85 unspecified descriptors, First 12 of them are reserved, the rest are avail
 922         .fill 85 * 16, 1, 0   # db (85 * 16) dup(0)
 923
 924 # IRQ 0 (System timer) - (INT 68h)
 925 .equ                IRQ0_SEL, .-IDT_BASE
 926         .word 0               # offset 15:0
 927         .long SYS_CODE64_SEL  # selector 15:0
 928         .byte 0               # 0 for interrupt gate
 929         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 930         .word 0               # offset 31:16
 931         .long 0               # offset 63:32
 932         .long 0               # 0 for reserved
 933
 934 # IRQ 1 (8042 Keyboard controller) - (INT 69h)
 935 .equ                IRQ1_SEL, .-IDT_BASE
 936         .word 0               # offset 15:0
 937         .long SYS_CODE64_SEL  # selector 15:0
 938         .byte 0               # 0 for interrupt gate
 939         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 940         .word 0               # offset 31:16
 941         .long 0               # offset 63:32
 942         .long 0               # 0 for reserved
 943
 944 # Reserved - IRQ 2 redirect (IRQ 2) - DO NOT USE!!! - (INT 6ah)
 945 .equ                IRQ2_SEL, .-IDT_BASE
 946         .word 0               # offset 15:0
 947         .long SYS_CODE64_SEL  # selector 15:0
 948         .byte 0               # 0 for interrupt gate
 949         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 950         .word 0               # offset 31:16
 951         .long 0               # offset 63:32
 952         .long 0               # 0 for reserved
 953
 954 # IRQ 3 (COM 2) - (INT 6bh)
 955 .equ                IRQ3_SEL, .-IDT_BASE
 956         .word 0               # offset 15:0
 957         .long SYS_CODE64_SEL  # selector 15:0
 958         .byte 0               # 0 for interrupt gate
 959         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 960         .word 0               # offset 31:16
 961         .long 0               # offset 63:32
 962         .long 0               # 0 for reserved
 963
 964 # IRQ 4 (COM 1) - (INT 6ch)
 965 .equ                IRQ4_SEL, .-IDT_BASE
 966         .word 0               # offset 15:0
 967         .long SYS_CODE64_SEL  # selector 15:0
 968         .byte 0               # 0 for interrupt gate
 969         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 970         .word 0               # offset 31:16
 971         .long 0               # offset 63:32
 972         .long 0               # 0 for reserved
 973
 974 # IRQ 5 (LPT 2) - (INT 6dh)
 975 .equ                IRQ5_SEL, .-IDT_BASE
 976         .word 0               # offset 15:0
 977         .long SYS_CODE64_SEL  # selector 15:0
 978         .byte 0               # 0 for interrupt gate
 979         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 980         .word 0               # offset 31:16
 981         .long 0               # offset 63:32
 982         .long 0               # 0 for reserved
 983
 984 # IRQ 6 (Floppy controller) - (INT 6eh)
 985 .equ                IRQ6_SEL, .-IDT_BASE
 986         .word 0               # offset 15:0
 987         .long SYS_CODE64_SEL  # selector 15:0
 988         .byte 0               # 0 for interrupt gate
 989         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
 990         .word 0               # offset 31:16
 991         .long 0               # offset 63:32
 992         .long 0               # 0 for reserved
 993
 994 # IRQ 7 (LPT 1) - (INT 6fh)
 995 .equ                IRQ7_SEL, .-IDT_BASE
 996         .word 0               # offset 15:0
 997         .long SYS_CODE64_SEL  # selector 15:0
 998         .byte 0               # 0 for interrupt gate
 999         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
1000         .word 0               # offset 31:16
1001         .long 0               # offset 63:32
1002         .long 0               # 0 for reserved
1003
1004 # IRQ 8 (RTC Alarm) - (INT 70h)
1005 .equ                IRQ8_SEL, .-IDT_BASE
1006         .word 0               # offset 15:0
1007         .long SYS_CODE64_SEL  # selector 15:0
1008         .byte 0               # 0 for interrupt gate
1009         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
1010         .word 0               # offset 31:16
1011         .long 0               # offset 63:32
1012         .long 0               # 0 for reserved
1013
1014 # IRQ 9 - (INT 71h)
1015 .equ                IRQ9_SEL, .-IDT_BASE
1016         .word 0               # offset 15:0
1017         .long SYS_CODE64_SEL  # selector 15:0
1018         .byte 0               # 0 for interrupt gate
1019         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
1020         .word 0               # offset 31:16
1021         .long 0               # offset 63:32
1022         .long 0               # 0 for reserved
1023
1024 # IRQ 10 - (INT 72h)
1025 .equ                 IRQ10_SEL, .-IDT_BASE
1026         .word 0               # offset 15:0
1027         .long SYS_CODE64_SEL  # selector 15:0
1028         .byte 0               # 0 for interrupt gate
1029         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
1030         .word 0               # offset 31:16
1031         .long 0               # offset 63:32
1032         .long 0               # 0 for reserved
1033
1034 # IRQ 11 - (INT 73h)
1035 .equ                 IRQ11_SEL, .-IDT_BASE
1036         .word 0               # offset 15:0
1037         .long SYS_CODE64_SEL  # selector 15:0
1038         .byte 0               # 0 for interrupt gate
1039         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
1040         .word 0               # offset 31:16
1041         .long 0               # offset 63:32
1042         .long 0               # 0 for reserved
1043
1044 # IRQ 12 (PS/2 mouse) - (INT 74h)
1045 .equ                 IRQ12_SEL, .-IDT_BASE
1046         .word 0               # offset 15:0
1047         .long SYS_CODE64_SEL  # selector 15:0
1048         .byte 0               # 0 for interrupt gate
1049         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
1050         .word 0               # offset 31:16
1051         .long 0               # offset 63:32
1052         .long 0               # 0 for reserved
1053
1054 # IRQ 13 (Floating point error) - (INT 75h)
1055 .equ                 IRQ13_SEL, .-IDT_BASE
1056         .word 0               # offset 15:0
1057         .long SYS_CODE64_SEL  # selector 15:0
1058         .byte 0               # 0 for interrupt gate
1059         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
1060         .word 0               # offset 31:16
1061         .long 0               # offset 63:32
1062         .long 0               # 0 for reserved
1063
1064 # IRQ 14 (Secondary IDE) - (INT 76h)
1065 .equ                 IRQ14_SEL, .-IDT_BASE
1066         .word 0               # offset 15:0
1067         .long SYS_CODE64_SEL  # selector 15:0
1068         .byte 0               # 0 for interrupt gate
1069         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
1070         .word 0               # offset 31:16
1071         .long 0               # offset 63:32
1072         .long 0               # 0 for reserved
1073
1074 # IRQ 15 (Primary IDE) - (INT 77h)
1075 .equ                 IRQ15_SEL, .-IDT_BASE
1076         .word 0               # offset 15:0
1077         .long SYS_CODE64_SEL  # selector 15:0
1078         .byte 0               # 0 for interrupt gate
1079         .byte 0x0e | 0x80     # type = 386 interrupt gate, present
1080         .word 0               # offset 31:16
1081         .long 0               # offset 63:32
1082         .long 0               # 0 for reserved
1083
1084 IDT_END:
1085
1086         .p2align 1
1087
1088 MemoryMapSize:  .long 0
1089 MemoryMap:  .long 0,0,0,0,0,0,0,0
1090         .long 0,0,0,0,0,0,0,0
1091         .long 0,0,0,0,0,0,0,0
1092         .long 0,0,0,0,0,0,0,0
1093         .long 0,0,0,0,0,0,0,0
1094         .long 0,0,0,0,0,0,0,0
1095         .long 0,0,0,0,0,0,0,0
1096         .long 0,0,0,0,0,0,0,0
1097         .long 0,0,0,0,0,0,0,0
1098         .long 0,0,0,0,0,0,0,0
1099         .long 0,0,0,0,0,0,0,0
1100         .long 0,0,0,0,0,0,0,0
1101         .long 0,0,0,0,0,0,0,0
1102         .long 0,0,0,0,0,0,0,0
1103         .long 0,0,0,0,0,0,0,0
1104         .long 0,0,0,0,0,0,0,0
1105         .long 0,0,0,0,0,0,0,0
1106         .long 0,0,0,0,0,0,0,0
1107         .long 0,0,0,0,0,0,0,0
1108         .long 0,0,0,0,0,0,0,0
1109         .long 0,0,0,0,0,0,0,0
1110         .long 0,0,0,0,0,0,0,0
1111         .long 0,0,0,0,0,0,0,0
1112         .long 0,0,0,0,0,0,0,0
1113         .long 0,0,0,0,0,0,0,0
1114         .long 0,0,0,0,0,0,0,0
1115         .long 0,0,0,0,0,0,0,0
1116         .long 0,0,0,0,0,0,0,0
1117         .long 0,0,0,0,0,0,0,0
1118         .long 0,0,0,0,0,0,0,0
1119
1120         .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
1121
1122         .org 0x0fe0
1123 MyStack:
1124         # below is the pieces of the IVT that is used to redirect INT 68h - 6fh
1125         #    back to INT 08h - 0fh  when in real mode...  It is 'org'ed to a
1126         #    known low address (20f00) so it can be set up by PlMapIrqToVect in
1127         #    8259.c
1128
1129         int $8
1130         iret
1131
1132         int $9
1133         iret
1134
1135         int $10
1136         iret
1137
1138         int $11
1139         iret
1140
1141         int $12
1142         iret
1143
1144         int $13
1145         iret
1146
1147         int $14
1148         iret
1149
1150         int $15
1151         iret
1152
1153
1154         .org 0x0ffe
1155 BlockSignature:
1156         .word 0xaa55
1157