Kernel level file integrity checker

by Efstratios Karatzas for FreeBSD

This project will focus on providing file integrity checking capabilities to pefs. The file integrity checker will compare cryptographic checksums of files against a static signed checksum list at access time. The files are thought to be immutable and use of securelevel will guarantee that lower filesystems will protect those files. Securelevel will be extended to only permit execution of files with immutable flag set.