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492 lines
11 KiB
492 lines
11 KiB
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%define GDT_Paragraph 0x1000
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%define GDT (GDT_Paragraph*16)
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%define GDT_CodeSegIndex 1
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%define GDT_DataSegIndex 2
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%define GDT_CodeSeg16Index 3
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%define GDT_DataSeg16Index 4
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%define GDT_Selector(DescriptorIndex, TableIndicator, RequestorPrivLevel) ((DescriptorIndex << 3) | ((TableIndicator & 1) << 2) | (RequestorPrivLevel & 0x3))
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%define GDT_CodeSegSelector GDT_Selector(GDT_CodeSegIndex, 0, 0)
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%define GDT_DataSegSelector GDT_Selector(GDT_DataSegIndex, 0, 0)
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%define GDT_CodeSeg16Selector GDT_Selector(GDT_CodeSeg16Index, 0, 0)
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%define GDT_DataSeg16Selector GDT_Selector(GDT_DataSeg16Index, 0, 0)
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%define VIDEO 0xB8000
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%define VIDEO_X_RES 80
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%define VIDEO_Y_RES 25
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%define ScreenCoord(x, y) (2*(VIDEO_X_RES*(y)+(x)))
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; GDT Stuff
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%define Data 0000b
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%define DataMutable 0010b
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%define DataShrink 0100b
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%define DataShrinkMutable 0110b
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%define Code 1000b
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%define CodeRead 1010b
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%define CodeOwnRing 1100b
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%define CodeOwnRingRead 1110b
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%macro GDT_NULL_ENTRY 1 ; address
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%assign address %1
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lea di, [address]
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xor ax, ax
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mov cx, 4
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rep stosw
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%assign GDT_COUNT (GDT_COUNT+1)
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%endmacro
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%macro GDT_ENTRY 6 ; address base limit type privilege bits32
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%assign address %1
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%assign base %2
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%assign limit %3
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%assign type (%4 & 0xf)
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%assign reserved (1<<4)
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%assign privilege ((%5 & 0x3) << 5)
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%assign present (1<<7)
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%assign access (present | privilege | reserved | type)
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%assign bits32 ((%6 & 1) << 2)
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%assign granularity (1<<3)
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%assign flags (granularity | bits32)
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%assign limit_0_15 (limit & 0xffff)
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%assign limit_16_19 ((limit >> 16) & 0xf)
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%assign base_0_15 (base & 0xffff)
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%assign base_16_23 ((base >> 16) & 0xff)
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%assign base_24_31 ((base >> 24) & 0xff)
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mov WORD [es:(address + 0)], limit_0_15
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mov WORD [es:(address + 2)], base_0_15
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mov WORD [es:(address + 4)], base_16_23 | (access << 8)
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mov WORD [es:(address + 6)], limit_16_19 | (flags << 4) | (base_24_31 << 8)
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%assign GDT_COUNT (GDT_COUNT+1)
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%endmacro
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%define IOKeyData 0x60
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%define InKeyStatus 0x64
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%define OutKeyCommand 0x64
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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Enable_A20:
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; Enables A20 gate using:the BIOS, keyboard controller, or Fast A20
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pushad ;Preserve registers
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pushfd ;Preserve EFLAGS because we might disable interrupts
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mov ax,0x2402 ;INT 15h AX=2402h: Query A20 status
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int 0x15 ;Check to see if A20 gate is enabled
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jc A20_No_BIOS ;Error? Don't use BIOS to enable gate
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test al,1 ;Test Bit 0 of AL
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je A20_Enabled ;A20 gate already enabled
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mov ax,0x2401 ;INT 15h AX=2401h: Enable A20 gate
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int 0x15 ;Use BIOS to enable A20 gate
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jc A20_No_BIOS ;Error? Don't use BIOS to enable gate
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or ah,ah ;Test AH
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jnz A20_No_BIOS ;Non-zero? A20 gate may not be enabled
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A20_Enabled:
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popfd ;Restore EFLAGS
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popad ;Restore registers
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ret ;Return
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A20_No_BIOS:
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mov ax,0x2403 ;INT 15h AX=2403h: Query A20 support
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int 0x15 ;Call BIOS to find out how the A20 gate can be enabled
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jc A20_KBD ;Error? Assume that keyboard controller is the only option
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test bx,1 ;Bit 0:Keyboard controller supported
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je A20_KBD ;BIOS indicates that keyboard controller is supported
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test bx,2 ;Bit 1:Fast A20 supported
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je FAST_A20 ;BIOS indicated that Fast A20 is supported
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call Check_A20 ;Test A20 gate manually
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jc A20_Enabled ;A20 gate already enabled
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A20_Fail:
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call A20_OUT_Wait ;"Unable to enable A20 gate!"
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cli ;Disable interrupts
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hlt ;Halt machine
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FAST_A20:
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in al,0x92 ;Read System Control Port A
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test al,2 ;Test Fast A20 bit
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jnz A20_Fail ;Bit already set, failed to enable A20 gate
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or al,2 ;Set Bit 1:Enable Fast A20
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and al,0xFE ;Always clear Bit 0 so that machine does not reboot
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out 0x92,al ;Write to port 92h
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call Check_A20 ;Check A20 gate
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jc A20_Enabled ;Success?
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cli ;No? something must have gone wrong
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hlt ;Clear interrupts and halt machine
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A20_KBD:
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cli ;Disable interrupts
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mov cx,50 ;Number of attempts to enable gate
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Use_KBD:
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call A20_OUT_Wait ;Wait for keyboard
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mov al,0xAD ;Disable Keyboard
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out 0x64,al ;Wait for Keyboard
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mov al,0xD0 ;Read Controller Output Port
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out 0x64,al
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call A20_IN_Wait ;Wait for Keyboard
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in al,0x60 ;Read Data Port
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push ax ;Save
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call A20_OUT_Wait ;Wait for Keyboard
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mov al,0xD1 ;Write Controller Output Port
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out 0x64,al
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call A20_OUT_Wait ;Wait for Keyboard
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pop ax ;Get port data back
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or al,10b ;Bit 1: Enable A20 gate
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out 0x60,al ;Write to data port
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call A20_OUT_Wait ;Wait for Keyboard
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mov al,0xAE ;Enable Keyboard
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out 0x64,al
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call A20_OUT_Wait ;Wait for Keyboard
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call Check_A20 ;Verify that gate is enabled
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jc A20_Enabled ;Yes? Return
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loop Use_KBD ;No? Keep trying
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jmp A20_Fail ;Could not enable gate after 50 tries
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A20_OUT_Wait:
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in al,0x64 ;Read status register
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test al,10b ;Is port ready?
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jnz A20_OUT_Wait ;Nope, wait
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ret ;Yep, continue
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A20_IN_Wait:
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in al,0x64 ;Read status register
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test al,1b ;Is port ready?
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jz A20_IN_Wait ;Nope, wait
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ret ;Yep, continue
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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Check_A20:
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; Test if A20 gate is enabled by comaparing the value in FFFF:7E0E
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; with the VBR boot signature at 0000:7DFE
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; Out: Carry flag set if A20 gate is enabled
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pushad ;Preserve registers
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push es
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mov ax, 0xFFFF
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mov es, ax ;Extra segment:FFFF
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cmp WORD [es:0x7DFE + 16], 0xAAFF ;See if boot signature is wrapped at FFFF:7E0E (Meaning FFFF:7E0E = 0:7DFE)
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stc ; Assume we didn't wrap, yes A20
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jne .End
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clc ; We did wrap, no A20
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.End:
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pop es
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popad
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ret
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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Go32Bit:
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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call Enable_A20
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; Set screen mode
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mov ax, 0x0003 ; AH=0 (Change video mode), AL=13h (Mode) = 320x200 - 256 colors
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mov bx, 0x0000
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int 0x10 ; Video BIOS interrupt
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;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; Global Descriptor Table ;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;
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mov ax, GDT_Paragraph
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mov es, ax
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mov cx, 4096
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lea si, [GO32_COPY_BEGIN]
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xor di, di
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rep movsb
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%assign GDT_COUNT 0
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GDT_NULL_ENTRY 0
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GDT_ENTRY (GDT_CodeSegIndex*8), 0x00000000, 0xffffffff, CodeRead, 0, 1
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GDT_ENTRY (GDT_DataSegIndex*8), 0x00000000, 0xffffffff, DataMutable, 0, 1
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GDT_ENTRY (GDT_CodeSeg16Index*8), 0x00000000, 0xffffffff, CodeRead, 0, 0
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GDT_ENTRY (GDT_DataSeg16Index*8), 0x00000000, 0xffffffff, DataMutable, 0, 0
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cli
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lgdt [GDT_Record]
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mov eax, cr0
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or al, 1 ; set PE (Protection Enable) bit in CR0 (Control Register 0)
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mov cr0, eax
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jmp ClearPrefetchQueue
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nop
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nop
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ClearPrefetchQueue:
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Manually assembled long jump ;;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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db 0x66 ; 32bit override
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db 0xea ; Long jump
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dd ProtectedModeBaby ; Absolute address
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dw GDT_CodeSegSelector ; Descriptor Selector
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GDT_Record:
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dw (GDT_COUNT*8) - 1 ; Size of GDT in bytes minus 1
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dd 0x1000*16 ; Linear address of GDT
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align 512
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BITS 32
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GO32_COPY_BEGIN:
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segment Go32Bit vstart=GDT
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GDT_SPACE: times (GDT_COUNT*8) db 0
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ProtectedModeBaby:
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; Update Other Segments
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mov ax, GDT_DataSegSelector
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mov ds, ax
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mov ss, ax
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mov es, ax
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mov fs, ax
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mov gs, ax
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; Setup stack
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mov esp, (100 << 20) - 1 ; 100M Addressable
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mov ebp, esp
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; Space for dynamic variables
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sub esp, 200*4 ; 200 32-bit integers
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push ebp
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DrawStuff:
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xor ecx, ecx
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xor edx, edx
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lea edi, [VIDEO]
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mov ebp, dword [Zoom]
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sar ebp, 9
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jnz .DrawLoop
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mov ebp, 0x7fffffff
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.DrawLoop:
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mov eax, [Px]
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shr eax, 4
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add eax, ecx
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imul eax, eax
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mov ebx, eax
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mov eax, [Py]
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shr eax, 4
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add eax, edx
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add eax, edx
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imul eax, eax
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add ebx, eax
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mov eax, [ColorOffset]
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push edx
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xor edx, edx
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idiv ebp
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pop edx
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xchg eax, ebx
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add ax, bx
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mov al, ah
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stosw
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inc ecx
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cmp ecx, VIDEO_X_RES
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jne .DrawLoop
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xor ecx, ecx
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inc edx
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cmp edx, VIDEO_Y_RES-2
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jne .DrawLoop
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pop ebp
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cld
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xor eax, eax
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in al, IOKeyData ; Get the scan code from the keyboard
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test al, 0x80
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jnz .ThereWasNothing
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cmp al, 75; left
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je .KeyLeft
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cmp al, 72; up
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je .KeyUp
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cmp al, 80; right
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je .KeyDown
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cmp al, 77; down
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je .KeyRight
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cmp al, 51; <
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je .KeyLess
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cmp al, 52; >
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je .KeyGreater
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cmp al, 1 ; Escape
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je .KeyEscape
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.ThereWasNothing:
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mov [Key], byte ' '
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jmp .PrintKeyLegend
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; lea esi, [ProtectedWelcomeStr]
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.KeyEscape:
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call Reboot
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jmp .PrintKeyLegend
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.KeyLeft:
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mov [Key], byte 'L'
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add [Px], dword -1
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jmp .PrintKeyLegend
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.KeyUp:
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mov [Key], byte 'U'
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add [Py], dword -1
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jmp .PrintKeyLegend
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.KeyRight:
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mov [Key], byte 'R'
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add [Px], dword 1
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jmp .PrintKeyLegend
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.KeyDown:
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mov [Key], byte 'D'
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add [Py], dword 1
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jmp .PrintKeyLegend
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.KeyLess:
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mov [Key], byte '<'
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add [Zoom], dword -1
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jmp .PrintKeyLegend
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.KeyGreater:
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mov [Key], byte '>'
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add [Zoom], dword 1
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.PrintKeyLegend:
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lea esi, [ThereWasSomethingStr]
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lea edi, [VIDEO + ScreenCoord((80-11), 24)]
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mov ah, 0x2f
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.print_loop:
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mov al, BYTE [esi]
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test al, al
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jz .break_print_loop
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stosw
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inc esi
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jmp .print_loop
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.break_print_loop:
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lea esi, [VarLabels]
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lea edi, [ConversionBuffer]
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mov ecx, VarLabelsLength
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call CopyData
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lea esi, [ConversionBuffer]
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lea edi, [VIDEO + ScreenCoord(0, 24)]
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mov ah, 0x0f
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call PrintString
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; lea esi, [ConversionBuffer]
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mov eax, dword [Px]
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sar eax, 4
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call IntToString
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; lea esi, [ConversionBuffer]
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; ecx set by IntToString
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mov edx, 7
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mov al, ' '
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call RightJustifyString
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; esi still ConversionBuffer
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mov ecx, edx
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lea edi, [VIDEO + ScreenCoord(StrXStart, 24)]
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mov ah, 0x70
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call PrintString
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; lea esi, [ConversionBuffer]
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mov eax, dword [Py]
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sar eax, 4
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call IntToString
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; lea esi, [ConversionBuffer]
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; ecx set by IntToString
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mov edx, 7
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mov al, ' '
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call RightJustifyString
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; esi still ConversionBuffer
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mov ecx, edx
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lea edi, [VIDEO + ScreenCoord(StrYStart, 24)]
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mov ah, 0x70
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call PrintString
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add [ColorOffset], dword 1
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jmp DrawStuff
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%include "Strings32.nasm"
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Halt:
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cli
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hlt
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jmp Halt
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; ------------------------------------------------------------------------------
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Reboot:
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in al, 0x64
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test al, 0x2 ; Wait for an empty Input Buffer
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jne Reboot
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mov al, 0xFE
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out 0x64, al ; Send the reboot call to the keyboard controller
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jmp Reboot
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;;;;;;;;;;;;;;;;;;;;;;;;
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;; Strings
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;;;;;;;;;;;;;;;;;;;;;;;;
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VarLabels: db "X:"
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StrXStart equ $-VarLabels
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db " "
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db "Y:"
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StrYStart equ $-VarLabels
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db " "
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VarLabelsLength equ $-VarLabels
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ProtectedWelcomeStr: db " Placeholder for SingOS - 32 bit edition! ", 0
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ProtectedWelcomeStrLength equ $-ProtectedWelcomeStr
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TestStr: db "hello, world"
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TestStrLength equ $-TestStr
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ThereWasSomethingStr: db " KEY = '"
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Key: db " ' ", 0
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Px: dd 0
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Py: dd 0
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ColorOffset: dd 0
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Zoom: dd (4<<9)
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ConversionBuffer: times 40 db 0
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align 512
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