From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750729AbWGORjr (ORCPT ); Sat, 15 Jul 2006 13:39:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750726AbWGORjr (ORCPT ); Sat, 15 Jul 2006 13:39:47 -0400 Received: from [83.101.158.20] ([83.101.158.20]:41224 "EHLO raad.intranet") by vger.kernel.org with ESMTP id S1750729AbWGORjq (ORCPT ); Sat, 15 Jul 2006 13:39:46 -0400 From: Al Boldi To: Arjan van de Ven Subject: Re: [PATCH] x86: Don't randomize stack unless current->personality permits it Date: Sat, 15 Jul 2006 20:39:58 +0300 User-Agent: KMail/1.5 Cc: Frank van Maarseveen , linux-kernel@vger.kernel.org, Andi Kleen References: <200607112257.22069.a1426z@gawab.com> <1152966159.3114.19.camel@laptopd505.fenrus.org> <200607151709.45870.a1426z@gawab.com> In-Reply-To: <200607151709.45870.a1426z@gawab.com> MIME-Version: 1.0 Content-Type: text/plain; charset="windows-1256" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200607152039.58733.a1426z@gawab.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org 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