一个经典的实模式向保护模式相互切换,并输出显示的HELLO WORLD

cxdzxc

.386P
CSEG16 SEGMENT USE16
    ASSUME DS: CSEG16
Start:
    cld
    push cs
    pop ds
    mov ax, 0B800H
    mov es, ax
    mov si, OFFSET MsgR1
    mov di, (20)*2
    call ShowMessage
    mov eax, SEG CSEG32
    shl eax, 4
    add DWORD PTR CSD32[2], eax
    mov eax, SEG CSEG16
    shl eax, 4
    add DWORD PTR CSD16[2], eax
    add eax, OFFSET Gdt0
    mov GdtA, eax
    push es
    cli
    lgdt FWORD PTR GdtL
    mov eax, cr0
    or al, 1
    mov cr0, eax
    DB 0EAH    ; jmp CSD32:0
    DW 0
    DW OFFSET CSD32 - OFFSET Gdt0
Return16:
    mov si, OFFSET Msg16
    mov di, (80*2+20)*2
    call ShowMessage
    mov eax, cr0
    and al, 0FEH
    mov cr0, eax
    jmp @F
@@:
    pop es
    sti
    mov si, OFFSET MsgR2
    mov di, (80*3+20)*2
    call ShowMessage
    mov ah, 4CH
    int 21H
ShowMessage PROC NEAR
    mov ah, 0F4H
    .repeat
        lodsb cs:[si]
        stosw es:[di]
    .until (al == 0)
    ret
ShowMessage ENDP
Gdt0    DW 00000H, 0000H, 0000H, 0000H
CSD32    DW 0FFFFH, 0000H, 9A00H, 00CFH
CSD16    DW 0FFFFH, 0000H, 9A00H, 0080H
DSD16    DW 0FFFFH, 8000H, 920BH, 0080H
GdtL    DW $-Gdt0-1
GdtA    DD 0
MsgR1    DB "HELLO WORLD_DOS_16", 0
Msg16    DB "HELLO WORLD_P16", 0
MsgR2    DB "RETURN DOS---QQ GROUP:83372198;QQ:750347821;EMAIL:750347821@QQ.COM NAME:CXDZXC AddressANZHOU DATE:2009-3-15,HTTP://BIOSOS.5D6D.COM", 0
CSEG16 ENDS
CSEG32 SEGMENT USE32
    mov ax, DSD16 - Gdt0
    mov es, ax
    mov esi, OFFSET Msg32
    mov di, (80*1+20)*2
    mov ah, 0F4h
    .repeat
        lodsb cs:[esi]
        stosw es:[di]
    .until (al == 0)
    DB 0EAH    ; jmp CSD16:0
    DD Return16
    DW CSD16 - Gdt0
Msg32    DB "HELLO WORLD_P32", 0
CSEG32 ENDS
SSEG SEGMENT STACK
    DW 400H DUP(?)
SSEG ENDS
END Start

[ 本帖最后由 cxdzxc 于 2009-10-30 14:02 编辑 ]

onionmax

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cxdzxc

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