How to distinguish Kernel Processes and User Processes in Linux?

Question

I know,
Proc file system will have all the PIDs of all processes, I want to distinguish kernel processes and user processes?
Can anyone help?

Comments

Typically a processes can run in both user space and kernel space, depending on what they're doing. The user code will run in user space until it requires kernel services, i.e. a kernel system call.

So I don't know how to answer this so only commenting.