#------------------------------------------------------------------------------
#*
#*   Copyright (c) 2006 - 2011, Intel Corporation. All rights reserved.<BR>
#*   This program and the accompanying materials                          
#*   are licensed and made available under the terms and conditions of the BSD License         
#*   which accompanies this distribution.  The full text of the license may be found at        
#*   http://opensource.org/licenses/bsd-license.php                                            
#*                                                                                             
#*   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,                     
#*   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.             
#*   
#*    start.S
#*  
#*   Abstract:
#*
#------------------------------------------------------------------------------

        .stack: 
        .486p: 
        .code16
    
.equ                        FAT_DIRECTORY_ENTRY_SIZE, 0x020
.equ                        FAT_DIRECTORY_ENTRY_SHIFT, 5
.equ                        BLOCK_SIZE, 0x0200
.equ                        BLOCK_MASK, 0x01ff
.equ                        BLOCK_SHIFT, 9

       .org 0x0

.global _start
_start:

Ia32Jump: 
  jmp   BootSectorEntryPoint  # JMP inst    - 3 bytes
  nop

OemId:              .ascii   "INTEL   "       # OemId               - 8 bytes

SectorSize:         .word  0                  # Sector Size         - 16 bits
SectorsPerCluster:  .byte  0                  # Sector Per Cluster  - 8 bits
ReservedSectors:    .word  0                  # Reserved Sectors    - 16 bits
NoFats:             .byte  0                  # Number of FATs      - 8 bits
RootEntries:        .word  0                  # Root Entries        - 16 bits
Sectors:            .word  0                  # Number of Sectors   - 16 bits
Media:              .byte  0                  # Media               - 8 bits  - ignored
SectorsPerFat:      .word  0                  # Sectors Per FAT     - 16 bits
SectorsPerTrack:    .word  0                  # Sectors Per Track   - 16 bits - ignored
Heads:              .word  0                  # Heads               - 16 bits - ignored
HiddenSectors:      .long  0                  # Hidden Sectors      - 32 bits - ignored
LargeSectors:       .long  0                  # Large Sectors       - 32 bits 
PhysicalDrive:      .byte  0                  # PhysicalDriveNumber - 8 bits  - ignored
CurrentHead:        .byte  0                  # Current Head        - 8 bits
Signature:          .byte  0                  # Signature           - 8 bits  - ignored
VolId:              .ascii "    "             # Volume Serial Number- 4 bytes
FatLabel:           .ascii "           "      # Label               - 11 bytes
SystemId:           .ascii "FAT12   "         # SystemId            - 8 bytes

BootSectorEntryPoint: 
        #ASSUME ds:@code
        #ASSUME ss:@code
      # ds = 1000, es = 2000 + x (size of first cluster >> 4)
      # cx = Start Cluster of EfiLdr
      # dx = Start Cluster of Efivar.bin

# Re use the BPB data stored in Boot Sector
        movw    $0x7c00, %bp

        pushw   %cx
# Read Efivar.bin
#       1000:dx    = DirectoryEntry of Efivar.bin -> BS.com has filled already
        movw    $0x1900, %ax
        movw    %ax, %es
        testw   %dx, %dx
        jnz     CheckVarStoreSize

        movb    $1, %al
NoVarStore: 
        pushw   %es
# Set the 5th byte start @ 0:19000 to non-zero indicating we should init var store header in DxeIpl
        movb    %al, %es:(4)
        jmp     SaveVolumeId

CheckVarStoreSize: 
        movw    %dx, %di
        cmpl    $0x4000, %ds:2(%di)
        movb    $2, %al
        jne     NoVarStore

LoadVarStore: 
        movb    $0, %al
        movb    %al, %es:(4)
        movw    (%di), %cx
#       ES:DI = 1500:0
        xorw    %di, %di
        pushw   %es
        movw    $0x1500, %ax
        movw    %ax, %es
        call    ReadFile
SaveVolumeId: 
        popw    %es
        movw    VolId(%bp), %ax
        movw    %ax, %es:(0)                    # Save Volume Id to 0:19000. we will find the correct volume according to this VolumeId
        movw    VolId+2(%bp), %ax
        movw    %ax, %es:(2)

# Read Efildr
        popw    %cx
#       cx    = Start Cluster of Efildr -> BS.com has filled already
#       ES:DI = 2000:0, first cluster will be read again
        xorw    %di, %di                            # di = 0
        movw    $0x2000, %ax
        movw    %ax, %es
        call    ReadFile
        movw    %cs, %ax
        movw    %ax, %cs:JumpSegment

JumpFarInstruction: 
        .byte   0xea
JumpOffset: 
        .word   0x200
JumpSegment: 
        .word   0x2000



# ****************************************************************************
# ReadFile
#
# Arguments:
#   CX    = Start Cluster of File
#   ES:DI = Buffer to store file content read from disk
#
# Return:
#   (ES << 4 + DI) = end of file content Buffer
#
# ****************************************************************************
ReadFile: 
# si      = NumberOfClusters
# cx      = ClusterNumber
# dx      = CachedFatSectorNumber
# ds:0000 = CacheFatSectorBuffer
# es:di   = Buffer to load file
# bx      = NextClusterNumber
        pusha
        movw    $1, %si                             # NumberOfClusters = 1
        pushw   %cx                                 # Push Start Cluster onto stack
        movw    $0xfff, %dx                         # CachedFatSectorNumber = 0xfff
FatChainLoop: 
        movw    %cx, %ax                            # ax = ClusterNumber    
        andw    $0xff8, %ax                         # ax = ax & 0xff8
        cmpw    $0xff8, %ax                         # See if this is the last cluster
        je      FoundLastCluster                    # Jump if last cluster found
        movw    %cx, %ax                            # ax = ClusterNumber
        shlw    %ax                                 # ax = ClusterNumber * 2
        addw    %cx, %ax                            # ax = ClusterNumber * 2 + ClusterNumber = ClusterNumber * 3
        shrw    %ax                                 # FatOffset = ClusterNumber*3 / 2
        pushw   %si                                 # Save si
        movw    %ax, %si                            # si = FatOffset
        shrw    $BLOCK_SHIFT, %ax                   # ax = FatOffset >> BLOCK_SHIFT
        addw    ReservedSectors(%bp), %ax           # ax = FatSectorNumber = ReservedSectors + (FatOffset >> BLOCK_OFFSET)
        andw    $BLOCK_MASK,%si                     # si = FatOffset & BLOCK_MASK
        cmpw    %dx, %ax                            # Compare FatSectorNumber to CachedFatSectorNumber
        je      SkipFatRead
        movw    $2, %bx
        pushw   %es
        pushw   %ds
        popw    %es
        call    ReadBlocks                          # Read 2 blocks starting at AX storing at ES:DI
        popw    %es
        movw    %ax, %dx                            # CachedFatSectorNumber = FatSectorNumber
SkipFatRead: 
        movw    (%si), %bx                          # bx = NextClusterNumber
        movw    %cx, %ax                            # ax = ClusterNumber
        andw    $1, %ax                             # See if this is an odd cluster number
        je      EvenFatEntry
        shrw    $4, %bx                             # NextClusterNumber = NextClusterNumber >> 4
EvenFatEntry: 
        andw    $0xfff, %bx                         # Strip upper 4 bits of NextClusterNumber
        popw    %si                                 # Restore si
        decw    %bx                                 # bx = NextClusterNumber - 1
        cmpw    %cx, %bx                            # See if (NextClusterNumber-1)==ClusterNumber
        jne     ReadClusters
        incw    %bx                                 # bx = NextClusterNumber
        incw    %si                                 # NumberOfClusters++
        movw    %bx, %cx                            # ClusterNumber = NextClusterNumber
        jmp     FatChainLoop
ReadClusters: 
        incw    %bx
        popw    %ax                                 # ax = StartCluster
        pushw   %bx                                 # StartCluster = NextClusterNumber
        movw    %bx, %cx                            # ClusterNumber = NextClusterNumber
        subw    $2, %ax                             # ax = StartCluster - 2
        xorb    %bh, %bh
        movb    SectorsPerCluster(%bp), %bl         # bx = SectorsPerCluster
        mulw    %bx                                 # ax = (StartCluster - 2) * SectorsPerCluster
        addw    (%bp), %ax                          # ax = FirstClusterLBA + (StartCluster-2)*SectorsPerCluster
        pushw   %ax                                 # save start sector
        movw    %si, %ax                            # ax = NumberOfClusters
        mulw    %bx                                 # ax = NumberOfClusters * SectorsPerCluster
        movw    %ax, %bx                            # bx = Number of Sectors
        popw    %ax                                 # ax = Start Sector
        call    ReadBlocks
        movw    $1, %si                             # NumberOfClusters = 1
        jmp     FatChainLoop
FoundLastCluster: 
        popw    %cx
        popa
        ret


# ****************************************************************************
# ReadBlocks - Reads a set of blocks from a block device
#
# AX    = Start LBA
# BX    = Number of Blocks to Read
# ES:DI = Buffer to store sectors read from disk
# ****************************************************************************

# cx = Blocks
# bx = NumberOfBlocks
# si = StartLBA

ReadBlocks: 
        pusha
        addl    LBAOffsetForBootSector(%bp), %eax   # Add LBAOffsetForBootSector to Start LBA
        addl    HiddenSectors(%bp), %eax            # Add HiddenSectors to Start LBA
        movl    %eax, %esi                          # esi = Start LBA
        movw    %bx, %cx                            # cx = Number of blocks to read
ReadCylinderLoop: 
        movw    $0x7bfc, %bp                        # bp = 0x7bfc
        movl    %esi, %eax                          # eax = Start LBA
        xorl    %edx, %edx                          # edx = 0
        movzwl  (%bp), %ebx                         # bx = MaxSector
        divl    %ebx                                # ax = StartLBA / MaxSector
        incw    %dx                                 # dx = (StartLBA % MaxSector) + 1

        movw    (%bp), %bx                          # bx = MaxSector
        subw    %dx, %bx                            # bx = MaxSector - Sector
        incw    %bx                                 # bx = MaxSector - Sector + 1
        cmpw    %bx, %cx                            # Compare (Blocks) to (MaxSector - Sector + 1)
        jg      LimitTransfer
        movw    %cx, %bx                            # bx = Blocks
LimitTransfer: 
        pushw   %ax                                 # save ax
        movw    %es, %ax                            # ax = es
        shrw    $(BLOCK_SHIFT-4), %ax               # ax = Number of blocks into mem system
        andw    $0x7f, %ax                          # ax = Number of blocks into current seg
        addw    %bx, %ax                            # ax = End Block number of transfer
        cmpw    $0x80, %ax                          # See if it crosses a 64K boundry
        jle     NotCrossing64KBoundry               # Branch if not crossing 64K boundry
        subw    $0x80, %ax                          # ax = Number of blocks past 64K boundry
        subw    %ax, %bx                            # Decrease transfer size by block overage
NotCrossing64KBoundry: 
        popw    %ax                                 # restore ax

        pushw   %cx
        movb    %dl, %cl                            # cl = (StartLBA % MaxSector) + 1 = Sector
        xorw    %dx, %dx                            # dx = 0
        divw    2(%bp)                              # ax = ax / (MaxHead + 1) = Cylinder  
                                                    # dx = ax % (MaxHead + 1) = Head

        pushw   %bx                                 # Save number of blocks to transfer
        movb    %dl, %dh                            # dh = Head
        movw    $0x7c00, %bp                        # bp = 0x7c00
        movb    PhysicalDrive(%bp), %dl             # dl = Drive Number
        movb    %al, %ch                            # ch = Cylinder
        movb    %bl, %al                            # al = Blocks
        movb    $2, %ah                             # ah = Function 2
        movw    %di, %bx                            # es:bx = Buffer address
        int     $0x13
        jc      DiskError
        popw    %bx
        popw    %cx
        movzwl  %bx, %ebx
        addl    %ebx, %esi                          # StartLBA = StartLBA + NumberOfBlocks
        subw    %bx, %cx                            # Blocks = Blocks - NumberOfBlocks
        movw    %es, %ax
        shlw    $(BLOCK_SHIFT-4), %bx
        addw    %bx, %ax
        movw    %ax, %es                            # es:di = es:di + NumberOfBlocks*BLOCK_SIZE
        cmpw    $0, %cx
        jne     ReadCylinderLoop
        popa
        ret

DiskError: 
        pushw %cs
        popw %ds
        leaw ErrorString, %si
        movw $7, %cx
        jmp  PrintStringAndHalt

PrintStringAndHalt: 
        movw $0xb800, %ax
        movw %ax, %es
        movw $160, %di
        rep
        movsw
Halt: 
        jmp   Halt

ErrorString: 
        .byte 'S', 0x0c, 'E', 0x0c, 'r', 0x0c, 'r', 0x0c, 'o', 0x0c, 'r', 0x0c, '!',0x0c

        .org     0x01fa
LBAOffsetForBootSector: 
        .long   0x0

        .org    0x01fe
        .word   0xaa55

#******************************************************************************
#******************************************************************************
#******************************************************************************

.equ                 DELAY_PORT, 0x0ed           # Port to use for 1uS delay
.equ                 KBD_CONTROL_PORT, 0x060     # 8042 control port     
.equ                 KBD_STATUS_PORT, 0x064      # 8042 status port      
.equ                 WRITE_DATA_PORT_CMD, 0x0d1  # 8042 command to write the data port
.equ                 ENABLE_A20_CMD, 0x0df       # 8042 command to enable A20

        .org     0x200
        jmp start
Em64String: 
        .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

start:  
        movw %cs, %ax
        movw %ax, %ds
        movw %ax, %es
        movw %ax, %ss
        movw $MyStack, %sp

#        mov ax,0b800h
#        mov es,ax
#        mov byte ptr es:[160],'a'
#        mov ax,cs
#        mov es,ax

        movl $0, %ebx
        leal MemoryMap, %edi
MemMapLoop: 
        movl $0xe820, %eax
        movl $20, %ecx
        movl $0x534d4150, %edx  # SMAP
        int $0x15
        jc  MemMapDone
        addl $20, %edi
        cmpl $0, %ebx
        je  MemMapDone
        jmp MemMapLoop
MemMapDone: 
        leal MemoryMap, %eax
        subl %eax, %edi                     # Get the address of the memory map
        movl %edi, MemoryMapSize            # Save the size of the memory map

        xorl    %ebx, %ebx
        movw    %cs, %bx                    # BX=segment
        shll    $4, %ebx                    # BX="linear" address of segment base
        leal    GDT_BASE(%ebx), %eax        # EAX=PHYSICAL address of gdt
        movl    %eax, (gdtr + 2)            # Put address of gdt into the gdtr
        leal    IDT_BASE(%ebx), %eax        # EAX=PHYSICAL address of idt
        movl    %eax, (idtr + 2)            # Put address of idt into the idtr
        leal    MemoryMapSize(%ebx), %edx   # Physical base address of the memory map

        addl $0x1000, %ebx                  # Source of EFI32
        movl %ebx, JUMP+2
        addl $0x1000, %ebx
        movl %ebx, %esi                     # Source of EFILDR32

#        mov ax,0b800h
#        mov es,ax
#        mov byte ptr es:[162],'b'
#        mov ax,cs
#        mov es,ax

#
# Enable A20 Gate 
#

        movw $0x2401, %ax                   # Enable A20 Gate
        int $0x15
        jnc A20GateEnabled                  # Jump if it suceeded

#
# If INT 15 Function 2401 is not supported, then attempt to Enable A20 manually.
#

        call    Empty8042InputBuffer        # Empty the Input Buffer on the 8042 controller
        jnz     Timeout8042                 # Jump if the 8042 timed out
        outw    %ax, $DELAY_PORT            # Delay 1 uS
        mov     $WRITE_DATA_PORT_CMD, %al   # 8042 cmd to write output port
        out     %al, $KBD_STATUS_PORT       # Send command to the 8042
        call    Empty8042InputBuffer        # Empty the Input Buffer on the 8042 controller
        jnz     Timeout8042                 # Jump if the 8042 timed out
        mov     $ENABLE_A20_CMD, %al        # gate address bit 20 on
        out     %al, $KBD_CONTROL_PORT      # Send command to thre 8042
        call    Empty8042InputBuffer        # Empty the Input Buffer on the 8042 controller
        movw    $25, %cx                    # Delay 25 uS for the command to complete on the 8042
Delay25uS: 
        outw    %ax, $DELAY_PORT            # Delay 1 uS
        loop    Delay25uS
Timeout8042: 


A20GateEnabled: 
        movw    $0x0008, %bx                # Flat data descriptor

#
# DISABLE INTERRUPTS - Entering Protected Mode
#

        cli

#        mov ax,0b800h
#        mov es,ax
#        mov byte ptr es:[164],'c'
#        mov ax,cs
#        mov es,ax

        .byte   0x66
        lgdt    gdtr
        .byte   0x66
        lidt    idtr

        movl    %cr0, %eax
        orb     $1, %al
        movl    %eax, %cr0
JUMP: 
# jmp far 0010:00020000
        .byte 0x66
        .byte 0xea
        .long 0x00020000
        .word 0x0010

Empty8042InputBuffer: 
        movw $0, %cx
Empty8042Loop: 
        outw    %ax, $DELAY_PORT            # Delay 1us
        in      $KBD_STATUS_PORT, %al       # Read the 8042 Status Port
        andb    $0x2, %al                   # Check the Input Buffer Full Flag
        loopnz  Empty8042Loop               # Loop until the input buffer is empty or a timout of 65536 uS
        ret

##############################################################################
# data
##############################################################################

        .p2align 1

        gdtr:    .long  GDT_END - GDT_BASE - 1  # GDT limit 
        .long 0                                 # (GDT base gets set above)
##############################################################################
#   global descriptor table (GDT)
##############################################################################

        .p2align 1

GDT_BASE: 
# null descriptor
.equ                NULL_SEL, .-GDT_BASE
        .word 0         # limit 15:0
        .word 0         # base 15:0
        .byte 0         # base 23:16
        .byte 0         # type
        .byte 0         # limit 19:16, flags
        .byte 0         # base 31:24

# linear data segment descriptor
.equ            LINEAR_SEL, .-GDT_BASE
        .word 0xFFFF    # limit 0xFFFFF
        .word 0         # base 0
        .byte 0
        .byte 0x92      # present, ring 0, data, expand-up, writable
        .byte 0xCF              # page-granular, 32-bit
        .byte 0

# linear code segment descriptor
.equ            LINEAR_CODE_SEL, .-GDT_BASE
        .word 0xFFFF    # limit 0xFFFFF
        .word 0         # base 0
        .byte 0
        .byte 0x9A      # present, ring 0, data, expand-up, writable
        .byte 0xCF              # page-granular, 32-bit
        .byte 0

# system data segment descriptor
.equ            SYS_DATA_SEL, .-GDT_BASE
        .word 0xFFFF    # limit 0xFFFFF
        .word 0         # base 0
        .byte 0
        .byte 0x92      # present, ring 0, data, expand-up, writable
        .byte 0xCF              # page-granular, 32-bit
        .byte 0

# system code segment descriptor
.equ            SYS_CODE_SEL, .-GDT_BASE
        .word 0xFFFF    # limit 0xFFFFF
        .word 0         # base 0
        .byte 0
        .byte 0x9A      # present, ring 0, data, expand-up, writable
        .byte 0xCF              # page-granular, 32-bit
        .byte 0

# spare segment descriptor
.equ        SPARE3_SEL, .-GDT_BASE
        .word 0         # limit 0xFFFFF
        .word 0         # base 0
        .byte 0
        .byte 0         # present, ring 0, data, expand-up, writable
        .byte 0         # page-granular, 32-bit
        .byte 0

# spare segment descriptor
.equ        SPARE4_SEL, .-GDT_BASE
        .word 0         # limit 0xFFFFF
        .word 0         # base 0
        .byte 0
        .byte 0         # present, ring 0, data, expand-up, writable
        .byte 0         # page-granular, 32-bit
        .byte 0

# spare segment descriptor
.equ        SPARE5_SEL, .-GDT_BASE
        .word 0         # limit 0xFFFFF
        .word 0         # base 0
        .byte 0
        .byte 0         # present, ring 0, data, expand-up, writable
        .byte 0         # page-granular, 32-bit
        .byte 0

GDT_END: 

        .p2align 1



idtr:  .long  IDT_END - IDT_BASE - 1 # IDT limit
        .long 0                      # (IDT base gets set above)
##############################################################################
#   interrupt descriptor table (IDT)
#
#   Note: The hardware IRQ's specified in this table are the normal PC/AT IRQ
#       mappings.  This implementation only uses the system timer and all other
#       IRQs will remain masked.  The descriptors for vectors 33+ are provided
#       for convenience.
##############################################################################

#idt_tag db "IDT",0     
        .p2align 1

IDT_BASE: 
# divide by zero (INT 0)
.equ                DIV_ZERO_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e | 0x80  # type = 386 interrupt gate, present
        .word 0            # offset 31:16

# debug exception (INT 1)
.equ                DEBUG_EXCEPT_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e | 0x80  # type = 386 interrupt gate, present
        .word 0            # offset 31:16

# NMI (INT 2)
.equ                NMI_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # type = 386 interrupt gate, present
        .word 0            # offset 31:16

# soft breakpoint (INT 3)
.equ                BREAKPOINT_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # type = 386 interrupt gate, present
        .word 0            # offset 31:16

# overflow (INT 4)
.equ                OVERFLOW_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # type = 386 interrupt gate, present
        .word 0            # offset 31:16

# bounds check (INT 5)
.equ                BOUNDS_CHECK_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # type = 386 interrupt gate, present
        .word 0            # offset 31:16

# invalid opcode (INT 6)
.equ                INVALID_OPCODE_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # type = 386 interrupt gate, present
        .word 0            # offset 31:16

# device not available (INT 7)
.equ                DEV_NOT_AVAIL_SEL, .-IDT_BASE
         .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # type = 386 interrupt gate, present
        .word 0            # offset 31:16

# double fault (INT 8)
.equ                DOUBLE_FAULT_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # type = 386 interrupt gate, present
        .word 0            # offset 31:16

# Coprocessor segment overrun - reserved (INT 9)
.equ                RSVD_INTR_SEL1, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # type = 386 interrupt gate, present
        .word 0            # offset 31:16

# invalid TSS (INT 0x0a)
.equ                INVALID_TSS_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # type = 386 interrupt gate, present
        .word 0            # offset 31:16

# segment not present (INT 0x0b)
.equ                SEG_NOT_PRESENT_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # type = 386 interrupt gate, present
        .word 0            # offset 31:16

# stack fault (INT 0x0c)
.equ                STACK_FAULT_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # type = 386 interrupt gate, present
        .word 0            # offset 31:16

# general protection (INT 0x0d)
.equ                GP_FAULT_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # type = 386 interrupt gate, present
        .word 0            # offset 31:16

# page fault (INT 0x0e)
.equ                PAGE_FAULT_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # type = 386 interrupt gate, present
        .word 0            # offset 31:16

# Intel reserved - do not use (INT 0x0f)
.equ                RSVD_INTR_SEL2, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # type = 386 interrupt gate, present
        .word 0            # offset 31:16

# floating point error (INT 0x10)
.equ                FLT_POINT_ERR_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # type = 386 interrupt gate, present
        .word 0            # offset 31:16

# alignment check (INT 0x11)
.equ                ALIGNMENT_CHECK_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
        .word 0            # offset 31:16

# machine check (INT 0x12)
.equ                MACHINE_CHECK_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
        .word 0            # offset 31:16

# SIMD floating-point exception (INT 0x13)
.equ                SIMD_EXCEPTION_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
        .word 0            # offset 31:16

# 85 unspecified descriptors, First 12 of them are reserved, the rest are avail
    .fill 85 * 8, 1, 0   # db (85 * 8) dup(0)

# IRQ 0 (System timer) - (INT 0x68)
.equ                IRQ0_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
        .word 0            # offset 31:16

# IRQ 1 (8042 Keyboard controller) - (INT 0x69)
.equ                IRQ1_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
        .word 0            # offset 31:16

# Reserved - IRQ 2 redirect (IRQ 2) - DO NOT USE!!! - (INT 0x6a)
.equ                IRQ2_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
        .word 0            # offset 31:16

# IRQ 3 (COM 2) - (INT 0x6b)
.equ                IRQ3_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
        .word 0            # offset 31:16

# IRQ 4 (COM 1) - (INT 0x6c)
.equ                IRQ4_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
        .word 0            # offset 31:16

# IRQ 5 (LPT 2) - (INT 0x6d)
.equ                IRQ5_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
        .word 0            # offset 31:16

# IRQ 6 (Floppy controller) - (INT 0x6e)
.equ                IRQ6_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
        .word 0            # offset 31:16

# IRQ 7 (LPT 1) - (INT 0x6f)
.equ                IRQ7_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
        .word 0            # offset 31:16

# IRQ 8 (RTC Alarm) - (INT 0x70)
.equ                IRQ8_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
        .word 0            # offset 31:16

# IRQ 9 - (INT 0x71)
.equ                IRQ9_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
        .word 0            # offset 31:16

# IRQ 10 - (INT 0x72)
.equ                 IRQ10_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
        .word 0            # offset 31:16

# IRQ 11 - (INT 0x73)
.equ                 IRQ11_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
        .word 0            # offset 31:16

# IRQ 12 (PS/2 mouse) - (INT 0x74)
.equ                 IRQ12_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
        .word 0            # offset 31:16
        
# IRQ 13 (Floating point error) - (INT 0x75)
.equ                 IRQ13_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
        .word 0            # offset 31:16

# IRQ 14 (Secondary IDE) - (INT 0x76)
.equ                 IRQ14_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
        .word 0            # offset 31:16

# IRQ 15 (Primary IDE) - (INT 0x77)
.equ                 IRQ15_SEL, .-IDT_BASE
        .word 0            # offset 15:0
        .long SYS_CODE_SEL # selector 15:0
        .byte 0            # 0 for interrupt gate
        .byte 0x0e |  0x80 # (10001110)type = 386 interrupt gate, present
        .word 0            # offset 31:16

IDT_END: 

        .p2align 1

MemoryMapSize:  .long 0
MemoryMap:  .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0
        .long 0,0,0,0,0,0,0,0

        .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
        .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

        .org 0x0fe0
MyStack:    
        # below is the pieces of the IVT that is used to redirect INT 68h - 6fh
        #    back to INT 08h - 0fh  when in real mode...  It is 'org'ed to a
        #    known low address (20f00) so it can be set up by PlMapIrqToVect in
        #    8259.c

        int $8
        iret

        int $9
        iret

        int $10
        iret

        int $11
        iret

        int $12
        iret

        int $13
        iret

        int $14
        iret

        int $15
        iret


        .org 0x0ffe
BlockSignature: 
        .word 0xaa55


