Execute a function in a x64 dll?

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Say if I have a x64 debug dll that includes 20 functions. Is there anyway I can execute any one of them if I feed into correct parameters?
I would like to write some source code that allows me to execute the functions according to my order.
Any thoughts is highly appreciated. Thanks.

Posted 18-Oct-12 11:11am

Nick Tsui

Updated 18-Oct-12 13:19pm

Sergey Alexandrovich Kryukov

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fjdiewornncalwe 18-Oct-12 17:12pm

If you target your solution to x64, then I shouldn't see why you can't do that.

Nick Tsui 18-Oct-12 18:08pm

Can I ask how I should do it?

Sergey Alexandrovich Kryukov 18-Oct-12 18:46pm

Can I ask what prevents you from doing it? There are no principle differences between x86, x86-64 or IE64 (Itanium) modes. A compiler will translate your code into any of them.
--SA

Sergey Alexandrovich Kryukov 18-Oct-12 18:56pm

Perhaps OP wants to use a mixture of two instruction-set architectures supported by the 64-bit OS, which is the problem.
Please see my answer.
--SA

Nick Tsui 18-Oct-12 17:23pm

Can I ask how I should do it?

Nick Tsui 18-Oct-12 18:07pm

Someone says rundll32.exe can do the job, but every time when I was using it to call a function in my.dll, it returns error like: There was a problem starting my.dll. my.dll is not a valid win32 application.
My command line is something like:
C:\Windows\System32\rundll32.exe C:\MyFolder\MyProject\my.dll, myfun 1 2
Where myfun(int a, int b) is a function in my.dll

manoranjan 19-Oct-12 1:13am

You cannot use rundll32 to call any type of functions. Usually, you use rundll to call functions that don't take arguments. However, see http://support.microsoft.com/kb/164787 for details. You can only pass strings to the function and not integers. In addition, either you need to create a .def file (for creating the dll) or, pass the decorated name to rundll32.

Nick Tsui 19-Oct-12 9:07am

I used rundll32 to call the constructor, which has no parameter input, of my class, it failed and returned the same error message.

manoranjan 22-Oct-12 0:16am

Please read the KB article carefully. You cannot call any arbitrary function using rundll32. Also, it does not make sense to call all functions at command-line. E.g. why would anyone want to call malloc() at DOS prompt? In your case, although, the constructor does not return a value (or take inputs), it needs to be invoked on an allocated memory. Therefore, even if the class was exported, you cannot use rundll32. Finally, you need to use decorated names.

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Sergey Alexandrovich Kryukov · Answer 1 · 2012-10-18T12:55:00

Please see my comment to the question. You don't need to do anything special to use one of the two 64-bit instruction-set architectures (x86-64 or Itanium, IE-64). To run it, you need that one of these architectures was on your hardware (CPU).

But further consideration is this: there is no a way to call a function of one executable module from some other executable module in the same process, if the two are compiled (targeted) to different instruction-set architectures. The only resolution could be separate processes collaborating over IPC. Also, on Windows, x86 is also always supported for any of the 64-bit architectures under WoW64.

That's all.

Please see:
http://en.wikipedia.org/wiki/Instruction_set_architecture[^],
http://en.wikipedia.org/wiki/WOW64[^],
http://en.wikipedia.org/wiki/X86[^],
http://en.wikipedia.org/wiki/X86-32[^],
http://en.wikipedia.org/wiki/X86-64[^],
http://en.wikipedia.org/wiki/Itanium[^].

Some advanced matter on instruction-set architectures and their interoperability:
http://en.wikipedia.org/wiki/X86_virtualization[^],
http://en.wikipedia.org/wiki/X86_calling_conventions[^],
http://en.wikipedia.org/wiki/X86_calling_conventions#x86-64_calling_conventions[^].

—SA