Re: Non-executable stack
Re: Non-executable stack
- Subject: Re: Non-executable stack
- From: Jim Magee <email@hidden>
- Date: Sun, 30 Mar 2003 23:35:01 -0500
On Sunday, March 30, 2003, at 7:48 PM, Brian Tabone wrote:
I read the MMU overview for the PowerPC and it seems that the MMU
supports fairly granular execute privileges (IE per page versus per
segment), which should make implementing the non-execute stack (and
perhaps non-execute data segment) simpler.
I think you need to read that again. The effect of the no-execute bit
is discussed on a page basis, but the bit itself is only settable at
the segment level. So, you have to give up 256 MB section(s) of your
address space to non-execute status, and you have to assure all stacks
are in that range. That was deemed too restrictive at the time.
--Jim
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