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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable 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 3FA39C4321A for ; Thu, 25 Apr 2019 15:36:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6CF73206C0 for ; Thu, 25 Apr 2019 15:36:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726985AbfDYPfs (ORCPT ); Thu, 25 Apr 2019 11:35:48 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:47236 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726229AbfDYPfr (ORCPT ); Thu, 25 Apr 2019 11:35:47 -0400 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92 #3 (Red Hat Linux)) id 1hJgPO-0002EI-Tp; Thu, 25 Apr 2019 15:35:35 +0000 Date: Thu, 25 Apr 2019 16:35:34 +0100 From: Al Viro To: Mauro Carvalho Chehab Cc: Arnd Bergmann , linux-fsdevel@vger.kernel.org, y2038@lists.linaro.org, linux-kernel@vger.kernel.org, Jason Gunthorpe , Daniel Vetter , Greg Kroah-Hartman , David Sterba , Darren Hart , Jonathan Cameron , Bjorn Andersson , devel@driverdev.osuosl.org, qat-linux@intel.com, linux-crypto@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, amd-gfx@lists.freedesktop.org, linux-input@vger.kernel.org, linux-iio@vger.kernel.org, linux-rdma@vger.kernel.org, linux-nvdimm@lists.01.org, linux-nvme@lists.infradead.org, linux-pci@vger.kernel.org, platform-driver-x86@vger.kernel.org, linux-remoteproc@vger.kernel.org, sparclinux@vger.kernel.org, linux-scsi@vger.kernel.org, linux-usb@vger.kernel.org, linux-btrfs@vger.kernel.org, ceph-devel@vger.kernel.org, linux-wireless@vger.kernel.org, netdev@vger.kernel.org, Sean Young Subject: Re: [PATCH v3 12/26] compat_ioctl: move more drivers to compat_ptr_ioctl Message-ID: <20190425153534.GS2217@ZenIV.linux.org.uk> References: <20190416202013.4034148-1-arnd@arndb.de> <20190416202701.127745-1-arnd@arndb.de> <20190425122153.450fc094@coco.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190425122153.450fc094@coco.lan> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Thu, Apr 25, 2019 at 12:21:53PM -0300, Mauro Carvalho Chehab wrote: > If I understand your patch description well, using compat_ptr_ioctl > only works if the driver is not for s390, right? No; s390 is where "oh, just set ->compat_ioctl same as ->unlocked_ioctl and be done with that; compat_ptr() is a no-op anyway" breaks. IOW, s390 is the reason for having compat_ptr_ioctl() in the first place; that thing works on all biarch architectures, as long as all stuff handled by ->ioctl() takes pointer to arch-independent object as argument. IOW, argument ignored => OK any arithmetical type => no go, compat_ptr() would bugger it pointer to int => OK pointer to string => OK pointer to u64 => OK pointer to struct {u64 addr; char s[11];} => OK pointer to long => needs explicit handler pointer to struct {void *addr; char s[11];} => needs explicit handler pointer to struct {int x; u64 y;} => needs explicit handler on amd64 For "just use ->unlocked_ioctl for ->ioctl" we have argument ignored => OK any arithmetical type => OK any pointer => instant breakage on s390, in addtion to cases that break with compat_ptr_ioctl(). Probably some form of that ought to go into commit message for compat_ptr_ioctl() introduction...