Update: This project is not being maintained and you should probably use eBPF
KPlugs is a Linux kernel module which provides an interface for dynamically executing scripts inside the Linux kernel. KPlugs uses a simple bytecode interpreter (the KPlugs Virtual Machine), and an interface that allows a user to dynamically load scripts into the kernel and execute them directly from user space. Because the interface is dynamic, it's easy to implement a user-mode library that wraps anything in the kernel.
KPlugs comes with a Python library that compiles a subset of the Python language to the KPlugs bytecode, and lets you easily load and execute your "kernel Python script".
For more information: http://www.kplugs.org