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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 1C0F4C4727F for ; Wed, 23 Sep 2020 17:46:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D381F20719 for ; Wed, 23 Sep 2020 17:46:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726693AbgIWRqP (ORCPT ); Wed, 23 Sep 2020 13:46:15 -0400 Received: from verein.lst.de ([213.95.11.211]:49388 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726130AbgIWRqP (ORCPT ); Wed, 23 Sep 2020 13:46:15 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id 5EA266736F; Wed, 23 Sep 2020 19:46:09 +0200 (CEST) Date: Wed, 23 Sep 2020 19:46:09 +0200 From: Christoph Hellwig To: Al Viro Cc: Christoph Hellwig , Andrew Morton , Jens Axboe , Arnd Bergmann , David Howells , David Laight , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-aio@kvack.org, io-uring@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org Subject: Re: [PATCH 5/9] fs: remove various compat readv/writev helpers Message-ID: <20200923174609.GA24379@lst.de> References: <20200923060547.16903-1-hch@lst.de> <20200923060547.16903-6-hch@lst.de> <20200923142549.GK3421308@ZenIV.linux.org.uk> <20200923143251.GA14062@lst.de> <20200923145901.GN3421308@ZenIV.linux.org.uk> <20200923163831.GO3421308@ZenIV.linux.org.uk> <20200923170527.GQ3421308@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200923170527.GQ3421308@ZenIV.linux.org.uk> User-Agent: Mutt/1.5.17 (2007-11-01) Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Wed, Sep 23, 2020 at 06:05:27PM +0100, Al Viro wrote: > On Wed, Sep 23, 2020 at 05:38:31PM +0100, Al Viro wrote: > > On Wed, Sep 23, 2020 at 03:59:01PM +0100, Al Viro wrote: > > > > > > That's a very good question. But it does not just compile but actually > > > > works. Probably because all the syscall wrappers mean that we don't > > > > actually generate the normal names. I just tried this: > > > > > > > > --- a/include/linux/syscalls.h > > > > +++ b/include/linux/syscalls.h > > > > @@ -468,7 +468,7 @@ asmlinkage long sys_lseek(unsigned int fd, off_t offset, > > > > asmlinkage long sys_read(unsigned int fd, char __user *buf, size_t count); > > > > asmlinkage long sys_write(unsigned int fd, const char __user *buf, > > > > size_t count); > > > > -asmlinkage long sys_readv(unsigned long fd, > > > > +asmlinkage long sys_readv(void *fd, > > > > > > > > for fun, and the compiler doesn't care either.. > > > > > > Try to build it for sparc or ppc... > > > > FWIW, declarations in syscalls.h used to serve 4 purposes: > > 1) syscall table initializers needed symbols declared > > 2) direct calls needed the same > > 3) catching mismatches between the declarations and definitions > > 4) centralized list of all syscalls > > > > (2) has been (thankfully) reduced for some time; in any case, ksys_... is > > used for the remaining ones. > > > > (1) and (3) are served by syscalls.h in architectures other than x86, arm64 > > and s390. On those 3 (1) is done otherwise (near the syscall table initializer) > > and (3) is not done at all. > > > > I wonder if we should do something like > > > > SYSCALL_DECLARE3(readv, unsigned long, fd, const struct iovec __user *, vec, > > unsigned long, vlen); > > in syscalls.h instead, and not under that ifdef. > > > > Let it expand to declaration of sys_...() in generic case and, on x86, into > > __do_sys_...() and __ia32_sys_...()/__x64_sys_...(), with types matching > > what SYSCALL_DEFINE ends up using. > > > > Similar macro would cover compat_sys_...() declarations. That would > > restore mismatch checking for x86 and friends. AFAICS, the cost wouldn't > > be terribly high - cpp would have more to chew through in syscalls.h, > > but it shouldn't be all that costly. Famous last words, of course... > > > > Does anybody see fundamental problems with that? > > Just to make it clear - I do not propose to fold that into this series; > there we just need to keep those declarations in sync with fs/read_write.c Agreed. The above idea generally sounds sane to me.