How to check for system functions within ModulePass during LLVM Instrumentation pass?

I’m implementing a custom LLVM modulePass, which performs some action on functions. I’m using Module::iterator to iterate through the functions in a Module. However, I would like to skip these iteration on global systems functions ( which are defined in system headers, etc).
I’ve done the similar scope limitation in Clang using SourceLocation. However, within the modulePass there isn’t any Declaration variables to get the location.
Can you please suggest, what would be the best way to do it.

Gentle reminder…