Messages in this thread | | | Date | Wed, 24 Mar 2004 08:29:24 -0800 | From | John Reiser <> | Subject | Re: Non-Exec stack patches |
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Jakub> but it is still possible some language interpreter or Jakub> something builds code on the fly on the stack).
David> That's why there is mprotect().
But mprotect() costs enough (hundreds of cycles) to be a significant burden in some cases. Generating code to a stack region that is inherently executable is inexpensive (even allowing for restrictive alignment and avoiding I/D cache conflicts), is thread safe, is async-signal safe, and takes less work than other alternatives. Yes, the "black hats" do this; so do the "white hats." Please do not increase the minimum cost for applications that want generate-and-execute on the stack at upredictable high frequency.
-- John Reiser, jreiser@BitWagon.com
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