From owner-freebsd-hackers Tue Sep 25 9:40:54 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 4C26737B408 for ; Tue, 25 Sep 2001 09:36:13 -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 f8PGYK695210; Tue, 25 Sep 2001 18:34:20 +0200 (CEST) Received: (from ticso@localhost) by mail.cicely.de (8.11.0/8.11.0) id f8PGYuo29417; Tue, 25 Sep 2001 18:34:56 +0200 (CEST) Date: Tue, 25 Sep 2001 18:34:55 +0200 From: Bernd Walter To: Bakul Shah Cc: Bernd Walter , hackers@FreeBSD.ORG Subject: Re: VM Corruption - stumped, anyone have any ideas? Message-ID: <20010925183455.A29324@cicely20.cicely.de> References: <20010925095607.B27615@cicely20.cicely.de> <200109251610.MAA18919@warspite.cnchost.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <200109251610.MAA18919@warspite.cnchost.com>; from bakul@bitblocks.com on Tue, Sep 25, 2001 at 09:10:21AM -0700 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 09:10:21AM -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. > > You can't continue if you run out of the stack in any case > but the issue is what happens when you run off the end of the > stack. In the FreeBSD case you trash the user struct and > discover this problem in a very indirect way and possibly > after trashing god-knows-what-else. No Doubt about it. But you missed my point completely. Nevertheless PHK already explained why it still help. -- 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