From: Al Boldi <a1426z@gawab.com>
To: Arjan van de Ven <arjan@infradead.org>
Cc: Frank van Maarseveen <frankvm@frankvm.com>,
linux-kernel@vger.kernel.org, Andi Kleen <ak@suse.de>
Subject: Re: [PATCH] x86: Don't randomize stack unless current->personality permits it
Date: Sat, 15 Jul 2006 20:39:58 +0300 [thread overview]
Message-ID: <200607152039.58733.a1426z@gawab.com> (raw)
In-Reply-To: <200607151709.45870.a1426z@gawab.com>
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
next prev parent reply other threads:[~2006-07-15 17:39 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-07-11 19:57 [PATCH] x86: Don't randomize stack unless current->personality permits it Al Boldi
2006-07-12 16:03 ` Andi Kleen
2006-07-12 20:12 ` Al Boldi
2006-07-12 20:27 ` Arjan van de Ven
2006-07-12 21:13 ` Al Boldi
2006-07-13 9:44 ` Frank van Maarseveen
2006-07-13 20:51 ` Al Boldi
2006-07-13 20:54 ` Arjan van de Ven
2006-07-15 11:29 ` Al Boldi
2006-07-15 12:22 ` Arjan van de Ven
2006-07-15 14:09 ` Al Boldi
2006-07-15 16:15 ` Arjan van de Ven
2006-07-15 17:39 ` Al Boldi [this message]
2006-07-17 15:50 ` Paulo Marques
2006-07-18 5:21 ` Al Boldi
-- strict thread matches above, loose matches on Subject: below --
2006-07-25 0:21 Chuck Ebbert
2006-07-25 4:57 ` Al Boldi
2006-07-19 17:02 Chuck Ebbert
2006-07-20 17:23 ` Al Boldi
2006-07-24 15:57 ` Al Boldi
2006-07-16 3:58 Chuck Ebbert
2006-07-16 19:49 ` Al Boldi
2006-07-11 15:22 Frank van Maarseveen
2006-07-11 20:11 ` Arjan van de Ven
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