Messages in this thread | | | From | Andi Kleen <> | Subject | Re: [PATCH for 2.6.18rc2] [1/7] i386/x86-64: Don't randomize stack top when... | Date | Tue, 25 Jul 2006 13:38:44 +0200 |
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On Tuesday 25 July 2006 11:06, Chuck Ebbert wrote: > In-Reply-To: <1153815124.8932.15.camel@laptopd505.fenrus.org> > > On Tue, 25 Jul 2006 10:12:04 +0200, Arjan van de Ven wrote: > > > > unsigned long arch_align_stack(unsigned long sp) > > > > { > > > > - if (randomize_va_space) > > > > + if (!(current->personality & ADDR_NO_RANDOMIZE) && > > > > randomize_va_space) sp -= get_random_int() % 8192; > > > > return sp & ~0xf; > > > > } > > > > > > I think this needs to be done always, at least on P4. It really isn't > > > 'randomization' at the same high level as the rest -- more like a small > > > adjustment. And the offset should be a multiple of 128 and < 7K (not > > > 8K.) Something like this: > > > > the 8K was what Intel proposed for 2.4 quite a while ago and has been in > > use in linux for years and years... Can you explain why you are saying > > 7Kb? throwing away that 1Kb of cache associativity is unfortunate and > > shouldn't be done unless there's a good reason, so I'm quite interested > > in finding out your reason ;) > > Well that's what the Intel IA-32 optimization manual says:
The reason I allowed to disable it is that it is sometimes very useful for debugging if you can get 100% reproducible addresses.
-Andi
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