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Wed, 16 Feb 2022 13:35:33 +0000 (UTC) X-FDA: 79148740146.24.E28FBCD Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.86.151]) by imf01.hostedemail.com (Postfix) with ESMTP id 4D00640006 for ; Wed, 16 Feb 2022 13:35:32 +0000 (UTC) Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mtapsc-5-x7kvjQ_dNbmfJSCohruuVA-1; Wed, 16 Feb 2022 13:35:28 +0000 X-MC-Unique: x7kvjQ_dNbmfJSCohruuVA-1 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 15.0.1497.28; Wed, 16 Feb 2022 13:35:25 +0000 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.028; Wed, 16 Feb 2022 13:35:25 +0000 From: David Laight To: 'Arnd Bergmann' , Linus Torvalds , Christoph Hellwig , "linux-arch@vger.kernel.org" , "linux-mm@kvack.org" , "linux-api@vger.kernel.org" , "arnd@arndb.de" , "linux-kernel@vger.kernel.org" , "viro@zeniv.linux.org.uk" CC: "linux@armlinux.org.uk" , "will@kernel.org" , "guoren@kernel.org" , "bcain@codeaurora.org" , "geert@linux-m68k.org" , "monstr@monstr.eu" , "tsbogend@alpha.franken.de" , "nickhu@andestech.com" , "green.hu@gmail.com" , "dinguyen@kernel.org" , "shorne@gmail.com" , "deller@gmx.de" , "mpe@ellerman.id.au" , "peterz@infradead.org" , "mingo@redhat.com" , "mark.rutland@arm.com" , "hca@linux.ibm.com" , "dalias@libc.org" , "davem@davemloft.net" , "richard@nod.at" , "x86@kernel.org" , "jcmvbkbc@gmail.com" , "ebiederm@xmission.com" , "akpm@linux-foundation.org" , "ardb@kernel.org" , "linux-alpha@vger.kernel.org" , "linux-snps-arc@lists.infradead.org" , "linux-csky@vger.kernel.org" , "linux-hexagon@vger.kernel.org" , "linux-ia64@vger.kernel.org" , "linux-m68k@lists.linux-m68k.org" , "linux-mips@vger.kernel.org" , "openrisc@lists.librecores.org" , "linux-parisc@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , "linux-riscv@lists.infradead.org" , "linux-s390@vger.kernel.org" , "linux-sh@vger.kernel.org" , "sparclinux@vger.kernel.org" , "linux-um@lists.infradead.org" , "linux-xtensa@linux-xtensa.org" Subject: RE: [PATCH v2 02/18] uaccess: fix nios2 and microblaze get_user_8() Thread-Topic: [PATCH v2 02/18] uaccess: fix nios2 and microblaze get_user_8() Thread-Index: AQHYIzdfY+IsqXyFuUGlEUsFmAHn6KyWK9Eg Date: Wed, 16 Feb 2022 13:35:25 +0000 Message-ID: <4a7e026b07c94668a18cb4857ad6b7a5@AcuMS.aculab.com> References: <20220216131332.1489939-1-arnd@kernel.org> <20220216131332.1489939-3-arnd@kernel.org> In-Reply-To: <20220216131332.1489939-3-arnd@kernel.org> 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 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 4D00640006 X-Rspam-User: Authentication-Results: imf01.hostedemail.com; dkim=none; spf=pass (imf01.hostedemail.com: domain of david.laight@aculab.com designates 185.58.86.151 as permitted sender) smtp.mailfrom=david.laight@aculab.com; dmarc=pass (policy=none) header.from=aculab.com X-Stat-Signature: 5p17kb8cxyk4erentwprj3simkkyrgmp X-HE-Tag: 1645018532-963091 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: From: Arnd Bergmann > Sent: 16 February 2022 13:13 >=20 > These two architectures implement 8-byte get_user() through > a memcpy() into a four-byte variable, which won't fit. >=20 > Use a temporary 64-bit variable instead here, and use a double > cast the way that risc-v and openrisc do to avoid compile-time > warnings. >=20 ... > =09case 4:=09=09=09=09=09=09=09=09\ > -=09=09__get_user_asm("lw", (ptr), __gu_val, __gu_err);=09\ > +=09=09__get_user_asm("lw", (ptr), x, __gu_err);=09=09\ > =09=09break;=09=09=09=09=09=09=09\ > -=09case 8:=09=09=09=09=09=09=09=09\ > -=09=09__gu_err =3D __copy_from_user(&__gu_val, ptr, 8);=09=09\ > -=09=09if (__gu_err)=09=09=09=09=09=09\ > -=09=09=09__gu_err =3D -EFAULT;=09=09=09=09\ > +=09case 8: {=09=09=09=09=09=09=09\ > +=09=09__u64 __x =3D 0;=09=09=09=09=09=09\ > +=09=09__gu_err =3D raw_copy_from_user(&__x, ptr, 8) ?=09=09\ > +=09=09=09=09=09=09=09-EFAULT : 0;=09\ > +=09=09(x) =3D (typeof(x))(typeof((x) - (x)))__x;=09=09\ > =09=09break;=09=09=09=09=09=09=09\ Wouldn't it be better to just fetch two 32bit values: Something like (for LE - nios2 is definitely LE: =09=09__u32 val_lo, val_hi; =09=09__get_user_asm("lw", (ptr), val_lo, __gu_err); =09=09__get_user_asm("lw", (ptr) + 4, val_hi, __gu_err); =09=09x =3D val_lo | val_hi << 32; =09=09break; =09David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1= PT, UK Registration No: 1397386 (Wales)