Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030509AbVIOQNd (ORCPT ); Thu, 15 Sep 2005 12:13:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030510AbVIOQNd (ORCPT ); Thu, 15 Sep 2005 12:13:33 -0400 Received: from smtp.osdl.org ([65.172.181.4]:39603 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S1030509AbVIOQNc (ORCPT ); Thu, 15 Sep 2005 12:13:32 -0400 Date: Thu, 15 Sep 2005 09:13:02 -0700 (PDT) From: Linus Torvalds To: Andrea Arcangeli cc: Hugh Dickins , Nick Piggin , linux-kernel@vger.kernel.org, Andrew Morton , Roland McGrath Subject: Re: ptrace can't be transparent on readonly MAP_SHARED In-Reply-To: <20050915154702.GA4122@opteron.random> Message-ID: References: <20050914212405.GD4966@opteron.random> <20050915154702.GA4122@opteron.random> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1173 Lines: 32 On Thu, 15 Sep 2005, Andrea Arcangeli wrote: > On Thu, Sep 15, 2005 at 08:12:59AM -0700, Linus Torvalds wrote: > > have a PROT_READONLY/PROT_NONE area that is visible from the debugger, but > > continues to cause SIGSEGV's if the user process itself tries to access > > it. To me, that's good. > > Continue to cause sigsegv yes, but on the wrong page, when it will read > the page it can contain different data compared to what is on > disk/pagecache. So? You're not making any sense. I repeat: we CANNOT AVOID the fact that we will do COW. That COW is required. No way we can avoid it. It has _nothing_ to do with maybe_mkwrite(). So I don't know why you continually refuse to just admit that fact. Why do you mix up the COW semantics with the maybe_mkwrite() semantics. If you can't argue against maybe_mkwrite() without involving the COW argument, then stop arguing. They are two totally different thigns. Linus - 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/