228 lines
4.0 KiB
NASM
228 lines
4.0 KiB
NASM
[BITS 16]
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[ORG 0x100]
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SECTION .text
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push cs
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push cs
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pop ds
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pop es
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call EnableA20
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mov ax,cs
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mov [RealCS],ax
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lea ax,[Real]
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mov [RealIP],ax
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xor eax,eax
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mov ax,cs
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shl eax,4
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mov [GDT.Entry1+2],ax
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mov [GDT.Entry2+2],ax
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mov [GDT.Entry4+2],ax
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mov [GDT.Entry5+2],ax
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shr eax,16
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mov [GDT.Entry1+4],al
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mov [GDT.Entry2+4],al
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mov [GDT.Entry4+4],al
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mov [GDT.Entry5+4],al
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xor eax,eax
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mov ax,cs
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shl eax,4
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add eax,gdt0
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mov [GDTR.Address],eax
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lgdt [GDTR]
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cli
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;mov al,0xFF
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;out 0x21,al
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mov al,0x80
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out 0x70,al
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mov si,msgpmode
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call showstr
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mov eax,cr0
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or al,1
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mov cr0,eax
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jmp SYS_CODE_SEL:GoPMode32
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GoPMode32:
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[BITS 32]
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mov ax,SYS_DATA_SEL
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mov ds,ax
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mov ecx,20000/4
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cld
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mov esi,kernel
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mov edi,0x100000
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mov ax,ALL_DATA_SEL
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mov es,ax
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mov gs,ax
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mov fs,ax
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mov ss,ax
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rep movsd
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mov ds,ax
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mov esp,0x3fffff
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call KERNEL_SEL:0x100000
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jmp REAL_CODE_SEL:GoReal
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GoReal:
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[BITS 16]
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mov ax,REAL_DATA_SEL
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mov ds,ax
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mov es,ax
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mov ss,ax
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mov gs,ax
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mov fs,ax
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mov esp,0xffff
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mov eax,cr0
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and al,0xFE
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mov cr0,eax
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jmp far [RealIP]
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Real:
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jmp Real
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msgpmode db 'Pmode loader is loading',0
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;======================SHOWSTR========================
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;Affiche la chaine de caractère pointé par ds:si à l'écran
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;-> DS, SI
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;<- Flag Carry si erreur
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;=====================================================
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showstr:
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pusha
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Next_Char:
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lodsb
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or al,al
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jz End_Show
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mov ah,0x0E
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mov bx,0x07
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int 0x10
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jmp Next_Char
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End_Show:
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popa
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ret
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;***********************EnableA20*******************************
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;->
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;<-
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;Ouvre l'autoroute A20
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;***************************************************************
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EnableA20:
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cli
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call ClearKeybBuffer
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call WaitKeybCommand
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mov al,0xd1
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out 0x64,al
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call WaitKeybCommand
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mov al,0xdf
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out 0x60,al
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call WaitKeybCommand
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jmp A20Enabled
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WaitKeybCommand:
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in al,0x64
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test al,0x02
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jnz WaitKeybCommand
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ret
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ClearKeybBuffer:
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in al,0x64
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test al,0x01
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jnz ReadKeyb
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ret
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ReadKeyb:
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in al,0x60
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jmp ClearKeybBuffer
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A20Enabled:
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sti
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ret
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section .data
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RealIP: dw 0
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RealCS: dw 0
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GDTR:
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.Size: dw GDT_END
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.Address: dd 0
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gdt0 equ $ ; null entry
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GDT:
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.Entry0: dw 0 ; limit 15:0
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dw 0 ; base 15:0
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db 0 ; base 23:16
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db 0 ; type
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db 0 ; limit 19:16, flags
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db 0 ; base 31:24
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SYS_CODE_SEL equ $-gdt0 ; code segment descriptor
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.Entry1: dw 0xFFFF
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dw 0x0 ; base
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db 0x0 ; base
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db 0x9A ; present, ring 0, code, non-conforming, readable
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db 0x40 ; 32 bit
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db 0
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SYS_DATA_SEL equ $-gdt0 ; data segment descriptor
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.Entry2: dw 0xFFFF
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dw 0x0 ; base
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db 0x0 ; base
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db 0x92 ; present, ring 0, data, expand-up, writable
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db 0x40 ; 32 bit
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db 0
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ALL_DATA_SEL equ $-gdt0 ; 4meg data segment descriptor
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.Entry3: dw 0x03ff
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dw 0x0 ; base
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db 0x0 ; base
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db 0x92 ; present, ring 0, data, expand-up, writable
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db 0xcf ; 4k pages, 32 bit
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db 0
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REAL_CODE_SEL equ $-gdt0 ; code segment descriptor for 16 bit mode
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.Entry4: dw 0xFFFF
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dw 0x0 ; base
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db 0x0 ; base
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db 0x9A ; present, ring 0, code, non-conforming, readable
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db 0x00 ; 16 bit
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db 0
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REAL_DATA_SEL equ $-gdt0 ; data segment descriptor for 16 bit mode
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.Entry5: dw 0xFFFF
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dw 0x0 ; base
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db 0x0 ; base
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db 0x92 ; present, ring 0, data, expand-up, writable
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db 0x00 ; 16 bit
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db 0
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KERNEL_SEL equ $-gdt0 ; 4meg code segment descriptor
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.Entry6: dw 0x03ff
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dw 0x0 ; base
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db 0x0 ; base
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db 0x9A ; present, ring 0, code, non-conforming, readable
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db 0xcf ; 4k pages, 32 bit
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db 0
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GDT_END equ $-gdt0 -1
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kernel:
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SECTION .bss
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