Re: dynamically written code problem

[Jakub Jelinek <jakub at redhat dot com>]

On Mon, Oct 11, 2004 at 09:38:41AM +0200, Paolo Bonzini wrote:
> >2) doing mmap (..., | PROT_EXEC, ...) is preferrable to allocating 
> >elsewhere
> >   and then mprotecting when using exec-shield - otherwise you lose
> >   execute protection for too many pages where it is not desirable
> 
> I don't have an exec-shield system, so I didn't research much on this. 
> But on my system, mmap is allocating in the 0x40000000 range, and malloc 
> is allocating at the brk (around 0x08000000).  Is this different when 
> exec-shield is activated?

Yes.  mmap with PROT_EXEC set attempts to allocate as low as possible,
usually below the executable.
mmap without PROT_EXEC allocates as high as possible, below the stack.

	Jakub