Run-time call stack verification is used to determine that a code module has been called by a legitimate caller. A return address on the stack indicates where execution is to return upon execution of the next return instruction, and this return address is indicative of where the code module was called from. The code module may determine that the call is allowed, or disallowed, based on the location of the return address. A calling convention is provided that allows the code module to be called through an intermediary, while also preserving the original return address that was in effect at the time the intermediary was called and also resisting modification to the call stack during the time that the original return address is being verified.