Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 9 Nov 2001 18:10:57 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 9 Nov 2001 18:10:48 -0500 Received: from pc3-redb4-0-cust118.bre.cable.ntl.com ([213.106.223.118]:49903 "HELO opel.itsolve.co.uk") by vger.kernel.org with SMTP id ; Fri, 9 Nov 2001 18:10:39 -0500 Date: Fri, 9 Nov 2001 23:10:37 +0000 From: Mark Zealey To: Linux Kernel Subject: Re: PROBLEM: Linux updates RTC secretly when clock synchronizes Message-ID: <20011109231037.C25361@itsolve.co.uk> In-Reply-To: <20011109223053.A964@atrey.karlin.mff.cuni.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: ; from rhw@MemAlpha.cx on Fri, Nov 09, 2001 at 10:54:10PM +0000 X-Operating-System: Linux sunbeam 2.2.19 X-Homepage: http://zealos.org/ Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 09, 2001 at 10:54:10PM +0000, Riley Williams wrote: > Hi Pavel. > > >>>> According to your comments, you prefer (2). > >>>> I most definitely prefer (1). > > >>> Hmm, and if some malicious software insmods kernel module to > >>> work around your printk()? > > >> ...it gets "Port busy" when it tries to access the RTC ports that the > >> RTC driver built into the kernel already has opened exclusively. At > >> least, that's my understanding of the situation at present. > > > It does not work that way. Userland does iopl(0), and then it just > > bangs any port it wants to. > > If any user can do that, then Linux is borken solid. > > Just out of curiosity, what is wrong with the idea of having the kernel > at iopl(0), any kernel modules at either iopl(1) or iopl(2) and apps at > iopl(3) ??? There is obviously something, but I've no idea what. Kernel stuff (kernel, modules) run at iopl(0). Only root programs can request iopl(0) for itself, otherwise all hell would break loose (eg, user 'nobody' writing to the hdd etc...) -- Mark Zealey mark@zealos.org mark@itsolve.co.uk UL++++>$ G!>(GCM/GCS/GS/GM) dpu? s:-@ a16! C++++>$ P++++>+++++$ L+++>+++++$ !E---? W+++>$ N- !o? !w--- O? !M? !V? !PS !PE--@ PGP+? r++ !t---?@ !X---? !R- b+ !tv b+ DI+ D+? G+++ e>+++++ !h++* r!-- y-- (www.geekcode.com) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/