intercepting file system system calls

Question

I am writing an application for which I need to intercept some filesystem system calls eg. unlink. I would like to save some file say abc. If user deletes the file then I need t

Answer 1

As far as hooking into the kernel and intercepting system calls go, this is something I do in a security module I wrote:

https://github.com/cormander/tpe-lkm

Look at hijacks.c and symbols.c for the code; how they're used is in the hijack_syscalls function inside security.c. I haven't tried this on linux > 3.0 yet, but the same basic concept should still work.

It's a bit tricky, and you may have to write a good deal of kernel code to do the file copy before the unlink, but it's possible here.