Re: Preventing exploitation with rebasing

[Seth Breidbart <sethb () panix com>]

In theory, it's easy to prove that some programs cannot be relocated,
period.  Anybody who has been programming long enough has seen people
re-use a memory location as both an address and a constant in order to
keep the program small enough (12k OK; 12k + 2 bytes really bad
news).  That can't be relocated.

Even under the assumption that locations aren't re-used, it's provably
impossible (Turing-complete) to determine whether the contents of a
location can be used as an address by a program.

That said, _if_ a program is relocatable, relocating it would seem to
be an easy way to gain some security.  Whether that's worth the cost
(in fragility and undebuggability) is another question.

Seth