Re: [Announcement] "Exec Shield", new Linux security feature

[Chuck Ebbert <76306.1226@compuserve.com>]

John Bradford wrote:

> Slightly off-topic, but does anybody know whether IA64 or x86-64 allow
> you to make the stack non-executable in the same way you can on SPARC?

 IA64 supports a mind-boggling variety of page-level protection modes,
including execute-only pages that usermode can jump to and get
'promoted' to lower (more privileged) levels.  _And_ it supports
protection keys that can be attached to pages so your process needs
to have the key loaded into a register to touch those pages.  The keys
can themselves be marked read/write/execute disable on loading, so
the supervisor can give you a key that keeps you from executing pages
even if their page-level protections would otherwise allow it.

 AMD64 supports a simple NX (no execute) bit that keeps both supervisor
and user code from executing, and that's probably all anyone really needs.

------
 Chuck