Messages in this thread | | | From | Al Boldi <> | Subject | Re: [PATCH] x86: Don't randomize stack unless current->personality permits it | Date | Sat, 15 Jul 2006 20:39:58 +0300 |
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Arjan van de Ven wrote: > On Sat, 2006-07-15 at 17:09 +0300, Al Boldi wrote: > > Arjan van de Ven wrote: > > > On Sat, 2006-07-15 at 14:29 +0300, Al Boldi wrote: > > > > Arjan van de Ven wrote: > > > > > > BTW, why does randomize_stack_top() mod against (8192*1024) > > > > > > instead of (8192) like arch_align_stack()? > > > > > > > > > > because it wants to randomize for 8Mb, unlike arch_align_stack > > > > > which wants to randomize the last 8Kb within this 8Mb ;) > > > > > > > > Randomizing twice? > > > > > > a VMA can only be randomized in 4Kb (well page size) granularity, so > > > the 8Mb randomization can only work in that 4Kb unit, the "second" > > > randomization can work in 16 byte granularity. > > > > > > > There is even a case where a mere rename or running through an extra > > > > shell causes a slowdown. And that's with randomization turned off. > > > > > > randomization off will slow stuff down yes... you get cache alias > > > contention that way. > > a question.. do you have prelink installed/active on your system? that > may very well mess with timings...
No, not that I am aware of. How can I find out? I confirmed this on a standard rhel4 virgin-install. Does rhel4 have prelink enabled by default?
But even so, I don't think this is a timing issue, as the slowdowns are so huge it is obvious even without timing.
And 2.4.31 doesn't have this problem.
Did you try it?
Thanks!
-- Al
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