From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Laight Subject: RE: [PATCH v2 02/18] uaccess: fix nios2 and microblaze get_user_8() 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> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; 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=jr3Dh3k7CC7YgbsgaubNDDBD8Tig0SDZzvDMZMY1Ihw=; b=skLxJe66B/MSAF qnnbXTc19HanljddGLWPTdYvlhvzVkyljShFrjJdPpDY1p+F40Hzp8oYreaO7RgeCMywkENf6y9kw XZ9iIKflbj78D0uRvHYRXqFwjYNtYPUl7w59/Snt727RPespBb1yu5M0eMWIpG2whOJU7WLk5CY6s qs6pjZXtStfk6H8iEuXacPi1+ZZulLIn9X/2fLnY+DpxHBYV8pa5KgS5MRU3pMXVrk2+8M4ZSPyGM cLQJ6Sm6I7ZOn/dLmIgjUGMyUcB27TdMCwvulDok/oc5zy6UE7HrHXiCOrB0GaNc9dsneLQd+yw5b iUzzdyDr97Y/Gli07eeA==; In-Reply-To: <20220216131332.1489939-3-arnd@kernel.org> Content-Language: en-US List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-riscv" Errors-To: linux-riscv-bounces+glpr-linux-riscv=m.gmane-mx.org@lists.infradead.org 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" From: Arnd Bergmann > Sent: 16 February 2022 13:13 > > These two architectures implement 8-byte get_user() through > a memcpy() into a four-byte variable, which won't fit. > > 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. > ... > case 4: \ > - __get_user_asm("lw", (ptr), __gu_val, __gu_err); \ > + __get_user_asm("lw", (ptr), x, __gu_err); \ > break; \ > - case 8: \ > - __gu_err = __copy_from_user(&__gu_val, ptr, 8); \ > - if (__gu_err) \ > - __gu_err = -EFAULT; \ > + case 8: { \ > + __u64 __x = 0; \ > + __gu_err = raw_copy_from_user(&__x, ptr, 8) ? \ > + -EFAULT : 0; \ > + (x) = (typeof(x))(typeof((x) - (x)))__x; \ > break; \ Wouldn't it be better to just fetch two 32bit values: Something like (for LE - nios2 is definitely LE: __u32 val_lo, val_hi; __get_user_asm("lw", (ptr), val_lo, __gu_err); __get_user_asm("lw", (ptr) + 4, val_hi, __gu_err); x = val_lo | val_hi << 32; break; David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)