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The information on Groklaw is not intended to constitute legal advice. While Mark is a lawyer and he has asked other lawyers and law students to contribute articles, all of these articles are offered to help educate, not to provide specific legal advice. They are not your lawyers.

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Comments belong to whoever posts them. Please notify us of inappropriate comments.

noooo!

Authored by: greed on Tuesday, September 25 2012 @ 06:25 PM EDT

Yes, "segments" on Intel x86-family CPUs are not what anyone else
means by segments.

Segments on normal machines are memory protection domains.

We don't need them any more: we can do the same thing with a proper paged memory
management unit. Of course, Intel is again behind the curve here, taking forever
to introduce an "execute" flag for page permissions.

You can fake old-school (non-Intel) segments with a PMMU. AIX does this, in
32-bit mode, by allocating stack, heap, text and shared to specific virtual
segments. (And then has to deal with the fact that the default size of the heap
segment is usually too small.)

But the CPU doesn't have segmented addressing, it just uses the PMMU and virtual
memory to set the permissions as needed and manage allocation.

The problem really boils down to: "easy to program OR robust against
attack. Pick one."

[ Reply to This | Parent | # ]

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