From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751303AbeFDSqw (ORCPT ); Mon, 4 Jun 2018 14:46:52 -0400 Received: from esa2.hgst.iphmx.com ([68.232.143.124]:24887 "EHLO esa2.hgst.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750950AbeFDSqv (ORCPT ); Mon, 4 Jun 2018 14:46:51 -0400 X-IronPort-AV: E=Sophos;i="5.49,476,1520870400"; d="scan'208";a="176488093" Subject: Re: [PATCH 3/3] riscv: fix __user annotation for __copy_user() To: Luc Van Oostenryck , Palmer Dabbelt Cc: "linux-riscv@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Albert Ou References: <20180601152123.47256-1-luc.vanoostenryck@gmail.com> <20180601152123.47256-4-luc.vanoostenryck@gmail.com> From: Atish Patra Message-ID: <235fec3e-be2e-874a-8313-e7390fcdca74@wdc.com> Date: Mon, 4 Jun 2018 11:46:50 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <20180601152123.47256-4-luc.vanoostenryck@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/1/18 8:22 AM, Luc Van Oostenryck wrote: > __copy_user() is a function, written in assembly, used to copy > memory between kernel & user space. As such its to & from args > may both take a user pointer or a kernel pointer. > > However the prototype for this function declare these two args > as 'void __user *', which is no more & no less correct than > declaring them as 'void *'. In fact theer is no possible correct /s/theer/there > annotation for such a function. > > The problem is worked around here by declaring these args as > unsigned long and casting them to the right type in each of > two callers raw_copy_{to,from}_user() as some kind of cast would > be needed anyway. > > Note: another solution, maybe cleaner but slightly more complex, > would be to declare two version of __copy_user, > either in the asm file or via an alias, each having already > the correct typing for raw_copy_{to,from}_user(). > I feel that would be a better solution as it is implemented similarly in ARM as well. I am unable to understand how "unsigned long" is better than "void*". x86 implementation has both arguments as void*. Can you please clarify ? Regards, Atish > Signed-off-by: Luc Van Oostenryck > --- > arch/riscv/include/asm/uaccess.h | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/arch/riscv/include/asm/uaccess.h b/arch/riscv/include/asm/uaccess.h > index 14b0b22fb..c7a6a4a4a 100644 > --- a/arch/riscv/include/asm/uaccess.h > +++ b/arch/riscv/include/asm/uaccess.h > @@ -392,19 +392,19 @@ do { \ > }) > > > -extern unsigned long __must_check __copy_user(void __user *to, > - const void __user *from, unsigned long n); > +extern unsigned long __must_check __copy_user(unsigned long to, > + const unsigned long from, unsigned long n); > > static inline unsigned long > raw_copy_from_user(void *to, const void __user *from, unsigned long n) > { > - return __copy_user(to, from, n); > + return __copy_user((unsigned long)to, (unsigned long)from, n); > } > > static inline unsigned long > raw_copy_to_user(void __user *to, const void *from, unsigned long n) > { > - return __copy_user(to, from, n); > + return __copy_user((unsigned long)to, (unsigned long)from, n); > } > > extern long strncpy_from_user(char *dest, const char __user *src, long count); >