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 E1050C2D0A8 for ; Wed, 23 Sep 2020 16:38:46 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 2996920936 for ; Wed, 23 Sep 2020 16:38:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2996920936 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zeniv.linux.org.uk Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 9DE0B6B0070; Wed, 23 Sep 2020 12:38:45 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9BF656B0072; Wed, 23 Sep 2020 12:38:45 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 83B316B0071; Wed, 23 Sep 2020 12:38:45 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0029.hostedemail.com [216.40.44.29]) by kanga.kvack.org (Postfix) with ESMTP id 5E54D6B006E for ; Wed, 23 Sep 2020 12:38:45 -0400 (EDT) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 2424C81EDBD3 for ; Wed, 23 Sep 2020 16:38:45 +0000 (UTC) X-FDA: 77294885010.14.grass09_0606d0527157 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin14.hostedemail.com (Postfix) with ESMTP id ECF391822989D; Wed, 23 Sep 2020 16:38:44 +0000 (UTC) X-HE-Tag: grass09_0606d0527157 X-Filterd-Recvd-Size: 3764 Received: from ZenIV.linux.org.uk (zeniv.linux.org.uk [195.92.253.2]) by imf18.hostedemail.com (Postfix) with ESMTP; Wed, 23 Sep 2020 16:38:44 +0000 (UTC) Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kL7mp-004f4D-Mx; Wed, 23 Sep 2020 16:38:31 +0000 Date: Wed, 23 Sep 2020 17:38:31 +0100 From: Al Viro To: Christoph Hellwig Cc: 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: <20200923163831.GO3421308@ZenIV.linux.org.uk> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200923145901.GN3421308@ZenIV.linux.org.uk> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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?