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Old 2nd March 2012
aleunix aleunix is offline
Real Name: Alessandro
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Join Date: May 2008
Location: Italy
Posts: 224
Default ASLR (Address Space Layout Randomization): i386 PAE vs 64 bit

As i discovery casually, using the last openbsd snapshot, starting from the new release probably the i386 will use PAE as default.
I already known that PAE is useful for give the possibility at 32 bit OS (using a pagination, as happen on the past on DOS) more then 4 gb of Ram but after some futher research, using as starting point the presentation give from jggimi's:
PAE for OpenBSD/i386, Michael Shalayeff
I was curious about the improvement security using the NX bit
and after a jump on:
Memory allocators in modern Operating Systems, Ariane van der Steldt
I discovery the ASLR.
On this article The PIE is not exactly a lieā€¦ where i think the general concept remain safe, despite speak about linux, was said that the few registry present on x86 platform make this solution less efficient (about performance) so even with system with less then 4 gb is better going directly for a 64 bit system.
Now i would like understand if PAE have a positive effect even from this point of view and which problematic the use of PAE could give at applications, for example i known that can give problem at some driver, but i don't known much about eventual other issue with other things.
Or if the 64bit remain the same the prefer choice even on low memory system for avoid eventual problems with certain software.
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