Re: Non-Exec stack patches

[David Mosberger]

>>>>> On Wed, 24 Mar 2004 11:02:45 -0800, John Reiser <jreiser@xxxxxxxxxxxx> said:

  >> Only one mprotect() call is needed to make the entire stack
  >> executable.

  John> mprotect() only works on the portion that is currently allocated.
  John> If the stack grows, then another call is needed.

No, mprotect() on the entire stack will mark the vm_area with the
desired protection and VM_GROWSDOWN/VM_GROWSUP will expand
automatically with the new protection.  And if you want to expand the
stack in user-level, e.g., by intercepting SIGSEGV, you'll either do
an mmap() or mprotect() at any rate so there is zero extra cost there.

	--david
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