From owner-freebsd-hackers Tue Sep 25 2:18:31 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from srv1.cosmo-project.de (srv1.cosmo-project.de [213.83.6.106]) by hub.freebsd.org (Postfix) with ESMTP id CE09F37B405 for ; Tue, 25 Sep 2001 02:18:27 -0700 (PDT) Received: from mail.cicely.de (cicely20 [10.1.1.22]) by srv1.cosmo-project.de (8.11.0/8.11.0) with ESMTP id f8P9IP692757; Tue, 25 Sep 2001 11:18:25 +0200 (CEST) Received: (from ticso@localhost) by mail.cicely.de (8.11.0/8.11.0) id f8P9IxC27864; Tue, 25 Sep 2001 11:18:59 +0200 (CEST) Date: Tue, 25 Sep 2001 11:18:59 +0200 From: Bernd Walter To: Peter Wullinger Cc: Bernd Walter , freebsd-hackers@FreeBSD.ORG Subject: Re: VM Corruption - stumped, anyone have any ideas? Message-ID: <20010925111858.C27615@cicely20.cicely.de> References: <200109250027.f8P0RRk97980@earth.backplane.com> <200109250114.VAA20993@glatton.cnchost.com> <20010925095607.B27615@cicely20.cicely.de> <20010925100103.A4016@pc04.ipc-kallmuenz.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <20010925100103.A4016@pc04.ipc-kallmuenz.de>; from RivaW@gmx.de on Tue, Sep 25, 2001 at 10:01:03AM +0200 X-Operating-System: NetBSD cicely20.cicely.de 1.5 sparc Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Tue, Sep 25, 2001 at 10:01:03AM +0200, Peter Wullinger wrote: > On Tue, Sep 25, 2001 at 09:56:07AM +0200, Bernd Walter wrote: > > On Mon, Sep 24, 2001 at 06:14:34PM -0700, Bakul Shah wrote: > > > FWIW, in a Unix port we did I remember putting the user > > > struct *above* the kernel stack. The stack grew down so you > > > hit the red zone (the guard pages) without clobbering the > > > user struct. Since struct user _ended_ on a page boundary, > > > its size was needed at locore.s assembly time but that was a > > > small price to pay for the added safety. > > > > I don't think a guard page can help here, because the page fault > > handler needs a working stack. > > > Depends on what is does ... if it just panics and syncs and does > not care overwriting the user struct of the current process (which > is lost anyway), is this much of a problem? Please correct me if I'm missing something. If it is overwriting there is no page fault thus no guard page and no panic. If you would have a page fault there is no space where the CPU can write the state information to for entering the handler. -- B.Walter COSMO-Project http://www.cosmo-project.de ticso@cicely.de Usergroup info@cosmo-project.de To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message