From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932247AbWDUIGk (ORCPT ); Fri, 21 Apr 2006 04:06:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932269AbWDUIGk (ORCPT ); Fri, 21 Apr 2006 04:06:40 -0400 Received: from ns2.suse.de ([195.135.220.15]:1743 "EHLO mx2.suse.de") by vger.kernel.org with ESMTP id S932247AbWDUIGj (ORCPT ); Fri, 21 Apr 2006 04:06:39 -0400 Date: Fri, 21 Apr 2006 10:06:38 +0200 From: Nick Piggin To: Andrew Morton Cc: Nick Piggin , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [patch 1/5] mm: remap_vmalloc_range Message-ID: <20060421080638.GP21660@wotan.suse.de> References: <20060301045901.12434.54077.sendpatchset@linux.site> <20060301045910.12434.4844.sendpatchset@linux.site> <20060421001712.4cd5625e.akpm@osdl.org> <20060421073315.GL21660@wotan.suse.de> <20060421005913.1c4322a2.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060421005913.1c4322a2.akpm@osdl.org> User-Agent: Mutt/1.5.6i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 21, 2006 at 12:59:13AM -0700, Andrew Morton wrote: > Nick Piggin wrote: > > > > They should use vma->vm_page_prot? > > > > The callers affected are the PAGE_SHARED ones (the others are unchanged). > > Isn't it correct to provide readonly mappings if userspace asks for it? > > Dunno. I assume perfmon was using PAGE_READONLY because it doesn't want > userspace altering the memory. One would think that this should be > enforced at mmap()-time, and that mprotect() might be able to override it > anyway. But I haven't looked that closely. Oh yes definitely, and the perfmon case is OK, because it sets PAGE_READONLY in ->vm_page_prot. About the mprotect issue -- I'm not sure, this might be a problem for perfmon? > First impression is that there's some potential for breaking stuff in all > this - convince me otherwise ;) Well, the PAGE_SHARED guys might break if userspace if they expect to be able to write to readonly mappings. Unfortunate, but we could just put our feet down and tell them to fix the code?