From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932506AbWGOL3R (ORCPT ); Sat, 15 Jul 2006 07:29:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932510AbWGOL3R (ORCPT ); Sat, 15 Jul 2006 07:29:17 -0400 Received: from [212.76.87.2] ([212.76.87.2]:46599 "EHLO raad.intranet") by vger.kernel.org with ESMTP id S932506AbWGOL3Q (ORCPT ); Sat, 15 Jul 2006 07:29:16 -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 14:29:32 +0300 User-Agent: KMail/1.5 Cc: Frank van Maarseveen , linux-kernel@vger.kernel.org, Andi Kleen References: <200607112257.22069.a1426z@gawab.com> <200607132351.04721.a1426z@gawab.com> <1152824071.3024.89.camel@laptopd505.fenrus.org> In-Reply-To: <1152824071.3024.89.camel@laptopd505.fenrus.org> MIME-Version: 1.0 Content-Disposition: inline Content-Type: text/plain; charset="windows-1256" Content-Transfer-Encoding: 7bit Message-Id: <200607151429.32298.a1426z@gawab.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org 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? Anyway, I tried different combinations of turning off randomization in both functions and got mixed results, so it looks like there is some interaction here. Trying different compiler versions and switches also show different results. Calling these slowdowns blips is really an understatement, as there are cases which lock into 800% hits. i.e: processes that, when repeatedly called, lock into a continuous 8x slowdown on i686P4. 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. 2.4.31 doesn't show these slowdowns. What is 2.6 doing? Thanks! -- Al