Using user-space processes to assist kernel modules

Question

I'm working on one piece of a very high performance piece of hardware that works under Linux. We'd like to cache some data but we're worried about memory consumption - so the idea is to create a user process to manage the cache. That way, the cache can be in virtual memory, not in kernel space, et cetera.

The question is: what's the best way to do this? My first instinct is to have the kernel module create a character device file, and have a user program that opens that file, then sits on a select statement waiting for commands to arrive on it. But I'm concerned that this might not be optimal. A friend mentioned he knew of a socket-based interface, but when pressed he couldn't provide any details....

Any suggestions?

Answer 1

I think you're looking for the netlink interface. See Why and How to Use Netlink Socket [sic] for more information. Be careful of security issues when talking between the kernel and user space; there was a recent vulnerability when udev neglected to check that messages were coming from the kernel rather than user space.