Arbitrary Code Execution

I'm not looking to execute arbitrary code in someone else's program. Instead, I'm trying to create a runtime compiler, that generates code, and then transfers execution to it. I'll probably look at various assemblers to figure out what instructions to generate, etc.,
but once I have everything in memory, is there a way I can transfer execution to the location of a pointer in C or C++?

Just FYI, I don't care if its x86 specific, because even if the method is not, the code I generate will be.

Quote:

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Originally Posted by CrazyNorman

I'm not looking to execute arbitrary code in someone else's program. Instead, I'm trying to create a runtime compiler, that generates code, and then transfers execution to it. I'll probably look at various assemblers to figure out what instructions to generate, etc.,
but once I have everything in memory, is there a way I can transfer execution to the location of a pointer in C or C++?

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Cast the address to an appropriate function type and call through the pointer. The machine code will have to comprehend C calling conventions in order to handle the stack properly.

Code:

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typedef void (*machine_func)();
machine_func f = (machine_func)some_address;
f();

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Thanks. Just what I was looking for.

Quote:

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Originally Posted by CrazyNorman

Thanks. Just what I was looking for.

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Be aware that on many platforms, memory which is marked as "data" is not executable, so your program may crash when you try to call your dynamically generated code. You have to learn how to configure a block of memory to allow execution, however that is done on your particular platform.