From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 610BAC433E1 for ; Mon, 17 Aug 2020 08:26:06 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C7D9020658 for ; Mon, 17 Aug 2020 08:26:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C7D9020658 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=ACULAB.COM Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 4BVRvZ0B3RzDqMF for ; Mon, 17 Aug 2020 18:26:02 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=aculab.com (client-ip=207.82.80.151; helo=eu-smtp-delivery-151.mimecast.com; envelope-from=david.laight@aculab.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=ACULAB.COM Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [207.82.80.151]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4BVRrT4vgHzDqPf for ; Mon, 17 Aug 2020 18:23:19 +1000 (AEST) Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-180-lNRQs7-OMBKEt5epJ5rllg-1; Mon, 17 Aug 2020 09:23:12 +0100 X-MC-Unique: lNRQs7-OMBKEt5epJ5rllg-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Mon, 17 Aug 2020 09:23:11 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Mon, 17 Aug 2020 09:23:11 +0100 From: David Laight To: 'Christoph Hellwig' , Al Viro , Michael Ellerman , "x86@kernel.org" Subject: RE: [PATCH 09/11] x86: remove address space overrides using set_fs() Thread-Topic: [PATCH 09/11] x86: remove address space overrides using set_fs() Thread-Index: AQHWdGicIkTuqnSld0yWphpVxhe9Oqk79IHw Date: Mon, 17 Aug 2020 08:23:11 +0000 Message-ID: <935d551809894d14965e430e05d21057@AcuMS.aculab.com> References: <20200817073212.830069-1-hch@lst.de> <20200817073212.830069-10-hch@lst.de> In-Reply-To: <20200817073212.830069-10-hch@lst.de> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0.001 X-Mimecast-Originator: aculab.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "linux-fsdevel@vger.kernel.org" , "linux-arch@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , Kees Cook , "linux-kernel@vger.kernel.org" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" From: Christoph Hellwig > Sent: 17 August 2020 08:32 > > Stop providing the possibility to override the address space using > set_fs() now that there is no need for that any more. To properly > handle the TASK_SIZE_MAX checking for 4 vs 5-level page tables on > x86 a new alternative is introduced, which just like the one in > entry_64.S has to use the hardcoded virtual address bits to escape > the fact that TASK_SIZE_MAX isn't actually a constant when 5-level > page tables are enabled. .... > @@ -93,7 +69,7 @@ static inline bool pagefault_disabled(void); > #define access_ok(addr, size)=09=09=09=09=09\ > ({=09=09=09=09=09=09=09=09=09\ > =09WARN_ON_IN_IRQ();=09=09=09=09=09=09\ > -=09likely(!__range_not_ok(addr, size, user_addr_max()));=09=09\ > +=09likely(!__range_not_ok(addr, size, TASK_SIZE_MAX));=09=09\ > }) Can't that always compare against a constant even when 5-levl page tables are enabled on x86-64? On x86-64 it can (probably) reduce to (addr | (addr + size)) < 0. =09David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1= PT, UK Registration No: 1397386 (Wales)