Next intruction to execute (IP)

This is a discussion on Next intruction to execute (IP) within the Tech Board forums, part of the Community Boards category; I have a script that load into memory a .exe file. I know the CS:IP address, but how can I ...

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    Registered User albert_sps's Avatar
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    Question Next intruction to execute (IP)

    I have a script that load into memory a .exe file. I know the CS:IP address, but how can I execute code using this address and an interrupt of DOS after i have loaded file into memory. I'm using Turbo c++.

    I have not to use interrupt 21h, 0x4b subfunction.

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    Captain Crash brewbuck's Avatar
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    Quote Originally Posted by albert_sps View Post
    I have a script that load into memory a .exe file. I know the CS:IP address, but how can I execute code using this address and an interrupt of DOS after i have loaded file into memory. I'm using Turbo c++.

    I have not to use interrupt 21h, 0x4b subfunction.
    So basically your task is to rewrite DOS. Okay then...

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    Kernel hacker
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    You mean that you have loaded an executable into memory, but you don't know how to "jump to it"?

    It's pretty simple really, just store the start-address (CS:IP) in memory, and use the indirect jump instruction:
    Code:
        jmp dword ptr [startaddress]
    Now, how you get back to where you started is a different matter.

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

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