From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751985AbcEYUDi (ORCPT ); Wed, 25 May 2016 16:03:38 -0400 Received: from mail-bl2on0083.outbound.protection.outlook.com ([65.55.169.83]:30080 "EHLO na01-bl2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751042AbcEYUDf (ORCPT ); Wed, 25 May 2016 16:03:35 -0400 Authentication-Results: davemloft.net; dkim=none (message not signed) header.d=none;davemloft.net; dmarc=none action=none header.from=caviumnetworks.com; Date: Wed, 25 May 2016 23:03:27 +0300 From: Yury Norov To: David Miller CC: , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH 01/23] all: syscall wrappers: add documentation Message-ID: <20160525200327.GA22395@yury-N73SV> References: <1464048292-30136-1-git-send-email-ynorov@caviumnetworks.com> <1464048292-30136-2-git-send-email-ynorov@caviumnetworks.com> <20160525.123017.1597296248000772613.davem@davemloft.net> MIME-Version: 1.0 Content-Type: text/plain; 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X-Microsoft-Exchange-Diagnostics: =?us-ascii?Q?1;CY1PR07MB2231;23:+fjP6b9Dibk/p8FSGNQfbHgNq5a/DCk/wTkndf4sI?= =?us-ascii?Q?nKe3KDbwCcaRxvn0BpZ+r5fvLsEroxZaGuusBvWSUMvLhocigBXk64aoN/XI?= =?us-ascii?Q?48WH3aC/GqoyWrWjvQYs6C+1RkryXt5Y12dp0ovBmxbbZRnAcsbTVmJ9YHwT?= =?us-ascii?Q?4CkOiDYbPdoHzed3SK9ahCrun3wj/sPlf/45eh4Y+f05w9ffjkQFw385goRm?= =?us-ascii?Q?9wHXFXcPQdTwf4QdQ+DQS+Tq3RWI0LQdn7gajQiExtsuXHsc3DkNOT/W6qO6?= =?us-ascii?Q?q19C8TTWF7SB+r8TrQpzZkeLRviL8jBTf8IH3VSv5A08eUKxQ94sPO97YCHj?= =?us-ascii?Q?EBohoJxuDFM1x7A2B1++9eH6iNWeVHucyAk0ec71qQl4UM0Pk2j3AcrsUFIV?= =?us-ascii?Q?VnVxusAYg3o824dLlM8K/XJ11++6K3LU5t2V6wmS83ZK61MqaqNwhUCDl6OT?= =?us-ascii?Q?vd+oZGYrYcogDqkv37/Zri1Nd323N7Vr/q3caUVuZRLVyltHCEtHts/wl8tS?= =?us-ascii?Q?Wn6KTD/iZQB9n+7MzIKOz2QQm0YtnZDCGM7DTX0rxyP+i56R5mTNa/7ahDjJ?= =?us-ascii?Q?Vtmevi31SRGe6RLY7lF+RjZFp6b0i/ydyqZxsFzZTSVRS1Z5//JUjlBFMiKY?= =?us-ascii?Q?37QsP6AKPJRvy0e2eIwLnOJ+8KNu9v1FtEJhEVmzd5iU9umweUDDI55GvnXT?= =?us-ascii?Q?kr4q0P4IKGJkx1teOcmWWigQHBjXWn0YiRMbPrDfrOkxvHgMTrFv57gqDoNZ?= =?us-ascii?Q?oJTf++Ks6opZY0NRVhLz3j8pkMqMsPcnh2HNg47StPOkRPY5Ws55qLEydkZg?= =?us-ascii?Q?maBFgm/PEihX9Jiq74JpEI+XeZiuPosGz0buVgmCEhKiS05QBKUGxM6UQ+tm?= =?us-ascii?Q?/sKk2ExZE3TuC6KnkoaNiAlPAHNN1LJQ4AkHZUmPRu23WzGtr/5EpcCgN6rJ?= =?us-ascii?Q?1mJs3xmW5fCBqmLpk1abeJuTRxZ29bNQ7JXm3ZGoA=3D=3D?= X-Microsoft-Exchange-Diagnostics: 1;CY1PR07MB2231;5:UDE/OcXmKUyNqVKoPuM/udNiYnNMsuUd0ZGBOBiMB5NGsdgimMS3UUrgb1tdNrS0MdmoMTVc+zuf6ToCKeJB3JsCeJfPgL4tugv+Px5H8cQImkDALh0R15kGtVGzC2vOp4EVd4DPpv4D3T1yy6OHXA==;24:zJytpvZzP79jV9H6qv1zG4okHRtWDJFjtOGMuN25GbHJXJy0+E/6XpQ0ExoinHA6NSCrVcnk9Us7dLXLok1yWDpznPGqi0shUswWL4kSrRo=;7:fuydfoNqkv9Z530nRY6fnU6tVFXESS69eVgSpvLplRT+yq7sWpFaxdx2SV+hjs8WGMmZrdcmqkCUM4znR6z5yArUULTW7+MsgNZKPA64VDI/QA3CdBIoRXts3cRvoAK0LZUrgxwz5mlJXiP88IR3AdqEy0Ou1tB+bLncOHNMTjXJprHoW93LkDbhFM4r1evp SpamDiagnosticOutput: 1:23 SpamDiagnosticMetadata: NSPM X-OriginatorOrg: caviumnetworks.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 May 2016 20:03:31.7540 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY1PR07MB2231 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 25, 2016 at 12:30:17PM -0700, David Miller wrote: > From: Yury Norov > Date: Tue, 24 May 2016 03:04:30 +0300 > > > +To clear that top halves, automatic wrappers are introduced. They clear all > > +required registers before passing control to regular syscall handler. > > Why have one of these for every single compat system call, rather than > simply clearing the top half of all of these registers unconditionally > in the 32-bit system call trap before the system call is invoked? > > That's what we do on sparc64. > > And with that, you only need wrappers for the case where there needs > to be proper sign extention of a 32-bit signed argument. It was discussed as one of possible solutions. The downside of it is that we cannot pass 64-bit types (like off_t) in single register. The other downside is that we clear top halves for every single syscall, and it looks excessive. So, from spark64 and s390 approaches we choosed second.