74 lines
1.1 KiB
NASM
74 lines
1.1 KiB
NASM
format MZ
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heap 0
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stack 800h
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entry main:start
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segment main use16
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use16
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start:
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mov ax,_data
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mov ds, ax
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mov es, ax
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xor eax, eax
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mov ax,ds
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shl eax, 4
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mov bx, gdt
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add ebx, eax ; ebx - ëèíåéíûé àäðåñ gdt
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mov word [gdtPtr], 2 * 8 -1 ; ïðåäåë gdt 2 äåñêðèïòîðà = 0x000f
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mov dword [gdtPtr + 2], ebx
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lgdt pword [gdtPtr]
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in al, 0x70 ;çàïðåùàåì NMI
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mov bl, al
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or al, 0x80
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out 70h , al
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in al, 0x71 ;íåêîòîðûå RTC ïîñëå çàïèñè áàéòà â ïîðò 0õ70
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;îæèäàþò îáðàùåíèÿ ê ïîðòó 0x71
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cli
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mov eax, cr0
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or al, 01b
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mov cr0, eax
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mov dx, 0x08
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mov gs, dx ;gs - ãëîáàëüíûé ñåãìåíò ñ áàçîé 0 è ïðåäåëîì 0xFFFFFFFF
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mov fs, dx
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and al, 0xFE
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mov cr0, eax
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sti
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mov al, bl
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out 70h , al
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in al, 71h
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mov dx,92h
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in al,dx
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or al,2
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out dx,al
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;òåïåðü ìîæíî ïîëó÷èòü äîñòóï êî âñåé ïàìÿòè
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;íàïðèìåð
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;mov eax, [gs:0xFFFFFFF0] ;
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mov ah,4ch ;çàâåðøåíèå ÄÎÑ ïðîãðàììû
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int 21h
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segment _data use16
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align 16
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gdt dw 0, 0, 0, 0 ;0
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_flat dw 0ffffh,0,0F200h,008fh ;08 ñåãìåíò äàííûõ DPL = 3
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;áàçà 0, ïðåäåë 0xFFFFFFFF
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gdtPtr dq ? |