需要帮助，在MS-DOS中钩新的键盘中断 [英] Need help hooking new keyboard interrupt in MS-DOS

问题描述

我正在为装配课做作业.

I am working on an assignment for an assembly class.

我以前设法使计时器中断显示并在每个刻度上更新一个时钟".

I have previously managed to make my timer interrupt display and update a 'clock' at every tick.

我正在尝试使用这些知识来替换键盘中断.但是，即使我注释掉新键盘中断处理程序的安装，我的程序也会干扰MS-DOS活动(即无法运行任何可执行文件，只能使用'dir'，'cd'和类似命令):

I am attempting to use this knowledge to replace my keyboard interrupt. But even when I comment out the installation of the new keyboard interrupt handler, my program is interfering with MS-DOS activities (i.e. cannot run any executables, can only use 'dir', 'cd' and similar commands):

.model tiny
.8086
.code
        org 100h
start:
        jmp setup

new_key PROC
        jmp cs: old_key
new_key ENDP

setup:
        mov ax, cs
        mov ds, ax

        old_key DD 00000000h

        MOV    AL, 9h                 ;+-
        MOV    AH, 35h                  ;| Save old_key
        INT    21h                     ;|
        MOV    WORD PTR [old_key],BX
        MOV    WORD PTR [old_key][2],ES


        ; cli   
        ; PUSH   CS                      ;| Install new_key
        ; POP    DS                      ;|
        ; LEA    DX, new_key
        ; MOV    AL, 9h
        ; MOV    AH, 25h
        ; INT    21h


        cli
        push ds
        LDS    DX,CS:[old_key]         ;+- 
        MOV    AL, 9h                  ;| Disinstall new_key
        MOV    AH, 25h                  ;| 
        INT    21h
        POP    DS
        STI   


        mov ax, TSR
        int CALLDOS

end start

由于即使在注释掉安装后仍然存在问题，我认为问题出在卸载或保存old_key上.我不知道哪里出了问题.应该不是安装和卸载代码与计时器中断的安装/卸载代码本质上相似?

Since there are problems even when I've commented out the installation, I think the problem lies with the disinstallation or the old_key saving. I do not know what is wrong however; shouldn't the installation and disinstallation code be essentially similar timer interrupt's install/disinstall code?

我们将不胜感激，谢谢您.

Assistance would be appreciated, thank you in advance.

推荐答案

    mov ds, ax

    old_key DD 00000000h

    MOV    AL, 9h                 ;+-

您不应该这样混合代码和数据. CPU不知道old_key不是代码，因此它将很乐意尝试执行它.将变量移到setup标签之前，或插入跳转指令以跳过该变量.

You shouldn't mix code and data like that. The CPU has no knowledge of old_key not being code, so it will happily try to execute it. Either move the variable to before the setup label, or insert a jump instruction to skip past it.

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