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=-4.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 1A943C433DB for ; Fri, 26 Mar 2021 16:46:23 +0000 (UTC) Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 B67DD619DC for ; Fri, 26 Mar 2021 16:46:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B67DD619DC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=ACULAB.COM Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=desiato.20200630; h=Sender:Content-Transfer-Encoding :Content-Type:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:In-Reply-To:References:Message-ID:Date: Subject:CC:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=MOg0GCaagrTwyXTh/qXuz5duMeS1PEfepxyUJ9trQFc=; b=ft2JcGWMsORYaTPe6JSVZSi0D NRqyLqOeTOtBRzeecqO34i5asMwk5R9wpIVSrGt0lwPCmFo2MqvAKoJ9OHsuTqCM0YUnBGMrTOCch wCpLvkXgScgLCdi2sQnCs3AajsmnKTb3yV1qJipDQy4u4X5b+N8/7x1K1ydvA+sxXIyacFWZbZayU Sckk7vpoCr1lGqeDDSeAkin6F0GIha0Yf+NEgGpbbkaFijMOgcANjGY/G/KMqKmP7hT83uCtRbWGP KxtJ0/xBsWwhTlleOad/pZgvK0CLQdGz65sFXbQlNoaOydRJIhMQdRn2Sp5UjoLt6AG8Z/8efkvU1 uo/z0VRjw==; Received: from localhost ([::1] helo=desiato.infradead.org) by desiato.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1lPpZz-0040hP-0f; Fri, 26 Mar 2021 16:44:59 +0000 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.86.151]) by desiato.infradead.org with esmtps (Exim 4.94 #2 (Red Hat Linux)) id 1lPpZt-0040ge-2k for linux-arm-kernel@lists.infradead.org; Fri, 26 Mar 2021 16:44:55 +0000 Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-213-YTy4IFWENUi9fJgzzqBpKg-2; Fri, 26 Mar 2021 16:44:49 +0000 X-MC-Unique: YTy4IFWENUi9fJgzzqBpKg-2 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Fri, 26 Mar 2021 16:44:48 +0000 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.012; Fri, 26 Mar 2021 16:44:48 +0000 From: David Laight To: 'Al Viro' , Christoph Hellwig CC: "linux-arch@vger.kernel.org" , "linux-s390@vger.kernel.org" , "linux-parisc@vger.kernel.org" , Arnd Bergmann , Brian Gerst , "x86@kernel.org" , "linux-mips@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "Luis Chamberlain" , "Eric W. Biederman" , "sparclinux@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , "linux-arm-kernel@lists.infradead.org" Subject: RE: [PATCH 3/4] exec: simplify the compat syscall handling Thread-Topic: [PATCH 3/4] exec: simplify the compat syscall handling Thread-Index: AQHXIlr1GfPxLRNSxkCVNQRYzf6AcKqWeGLg Date: Fri, 26 Mar 2021 16:44:48 +0000 Message-ID: References: <20210326143831.1550030-1-hch@lst.de> <20210326143831.1550030-4-hch@lst.de> In-Reply-To: Accept-Language: en-GB, 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 X-Mimecast-Originator: aculab.com Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210326_164453_220855_4EA723A1 X-CRM114-Status: GOOD ( 11.31 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Al Viro > Sent: 26 March 2021 16:12 > > On Fri, Mar 26, 2021 at 03:38:30PM +0100, Christoph Hellwig wrote: > > > +static const char __user * > > +get_user_arg_ptr(const char __user *const __user *argv, int nr) > > { > > + if (in_compat_syscall()) { > > + const compat_uptr_t __user *compat_argv = > > + compat_ptr((unsigned long)argv); > > compat_uptr_t compat; > > > > + if (get_user(compat, compat_argv + nr)) > > return ERR_PTR(-EFAULT); > > return compat_ptr(compat); > > + } else { > > + const char __user *native; > > > > + if (get_user(native, argv + nr)) > > + return ERR_PTR(-EFAULT); > > + return native; > > + } > > } > > Yecchhh.... So you have in_compat_syscall() called again and again, for > each argument in the list? I agree that current version is fucking ugly, > but I really hate that approach ;-/ Especially since in_compat_syscall() isn't entirely trivial on x86-64. Probably all in the noise for 'exec', but all the bits do add up. You may not want separate get_user() on some architectures either. The user_access_begin/end aren't cheap. OTOH if you call copy_from_user() you get hit by the stupid additional costs of 'user copy hardening'. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales) _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel