One of the things I've been thinking about recently was "protected
swap".  (specifically, for diskless paging space), but it occurs to me
that it could also apply to executables.

If you do MD5 hashes (or HMAC-SHA1, or whatever) *per file page*, with
the per-page hashes protected by a meta-hash, it might be possible to
do this sort of thing on the fly with minimal additional I/O impact
(you still wind up touching all the bytes of the page and hashing the
data, but it would be in the page fault handler and might actually not
hurt that much).

Exactly where to store the metadata is an interesting question..

					- Bill