获取单个 C 函数的可执行二进制文件

Question

I have a simple C function, called add :

int add(int a, int b) {
  return a + b;
}

I need to get the optimized executable binary code for this given function without any of the other side effects of the binary. This would then be dynamically loaded and modified to include templates via a JIT system. I have experimented with trying to use objdump, but that doesn't really work for getting the actual binary as the object file is not the actual executable.

I need to link together the moving parts of functions to include their binary together at runtime and enabled PROT_EXEC to execute all of these partials together as a single function and call as a function pointer. The reason I need this is because I have a byte instruction encoding type which I would like to turn into JIT functions on the fly (similar to JIT compiling RegExp into validator functions). If there are any other viable solutions I should consider, then please describe them.

The main reason I want to use this approach is because I can see the godbolt shows the binary for functions as self-contained, so hopefully I can do something similar to include the binary in my own project.

Thank you for any help.

Note: the C function is entirely self-contained without referencing other functions

Answer 1

The easiest way is using IDA . You can compile your code (preferably with symbols) into ELF file/ EXE file and open the generated file in IDA. There you can see your function in the function window and then move into the hex window to copy the hex dump of your function.

Note: There are a lot of things that can go wrong here, for example, you must compile your code with the flag -PIC so it wouldn't use absolute addresses.

It is also recommended to know at least basic assembly.

This link might be interesting: https://github.com/Neetx/Shellcode-Extractor