Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265135AbTFMFLF (ORCPT ); Fri, 13 Jun 2003 01:11:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S265136AbTFMFLF (ORCPT ); Fri, 13 Jun 2003 01:11:05 -0400 Received: from neon-gw-l3.transmeta.com ([63.209.4.196]:20746 "EHLO neon-gw.transmeta.com") by vger.kernel.org with ESMTP id S265135AbTFMFLD (ORCPT ); Fri, 13 Jun 2003 01:11:03 -0400 Date: Thu, 12 Jun 2003 22:24:27 -0700 (PDT) From: Linus Torvalds To: davidm@hpl.hp.com cc: roland@redhat.com, Subject: Re: FIXMAP-related change to mm/memory.c In-Reply-To: <200306130124.h5D1O2DT025311@napali.hpl.hp.com> Message-ID: 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: 979 Lines: 28 On Thu, 12 Jun 2003, David Mosberger wrote: > > Is it possible to constrain the FIXADDR range on x86/x86-64 > (FIXADDR_START-FIXADDR_TOP) such that the entire range is read-only by > user-level? If so, we could simplify the permission test like this: Well, you could replace the uses of FIXADDR_START/FIXADDR_TOP with something like FIXADDR_USER_START/FIXADDR_USER_TOP, and then force those to cover only the _one_ user-accessible page. Something like #define FIXADDR_USER_START (fix_to_virt(FIX_VSYSCALL)) #define FIXADDR_USER_END (FIXADDR_USER_START + PAGE_SIZE) should work. In that case you can drop the page table testing, since we "know" it is safe. But I'm too lazy to test, so please send a tested patch, 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/