How to access user space memory from the Linux kernel?

Question

I know that copy_to_user/copy_from_user, get_user/put_user functions are for this purpose.

My question is that, given

Answer 1

You'll need to follow an address to get a corresponding page struct (see follow_page for the example). Next, getting the page struct you'll need to map it to kernel's address space via kmap or kmap_atomic.