CODEWITHSUNDEEP
winapiassemblyportable-executable
Puppy
Puppy

Reputation: 146998

WinAPI functions in new .exe

I've been looking recently into creating a new native language. I understand the (very) basics of the PE format and I've grabbed an assembler with a fairly kind interface off the webs, which I've successfully used to implement some simple functions. But I've run into a problem using functions from a library. The only way that I've called library functions from a dynamically compiled function previously is to pass in the function pointer manually- something I can't do if I create PE files and execute them in their own process. Now, I'm not planning on using the CRT, but I will need access to the Win API to implement my own standard libraries. How do I generate a reference to a WinAPI function so that the PE loader will patch it up?

Upvotes: 0

Views: 228

Answers (2)

egrunin
egrunin

Reputation: 25083

How about starting by emitting C instead of assembly? Then writing directly to ASM is just an optimization.

I'm not being facetious: most compilers turn out some kind of intermediate code before the final native code pass.

I realize you're trying to get away from all the null-delmited rigmarole, but you'll need that for the WinAPI functions anyway.

Re-reading your question: you do realize that you can get the WinAPI function addresses by calling LoadLibrary(), then calling GetProcAddress(), and then setting up the call...right?

If you want to see how to bootstrap this from pure assembly: the old SDKs had ASM sample code, probably the new ones still do. If they don't, the DDK will.

Upvotes: 0

kichik
kichik

Reputation: 34744

You need to write an import table. It's basically a list of function names that you wish to use in your application. It's pointed to by the PE header. The loader loads the DLL files into the process memory space for you, finds the requested function in their export table and leaves the address for it in the import table. You then usually dereference that and jmp there.

Check out Izelion's assembly tutorial for the full details and for asm examples.

Upvotes: 2

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