From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752562AbbGODS7 (ORCPT ); Tue, 14 Jul 2015 23:18:59 -0400 Received: from mail-wi0-f174.google.com ([209.85.212.174]:35976 "EHLO mail-wi0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752494AbbGODS5 (ORCPT ); Tue, 14 Jul 2015 23:18:57 -0400 Message-ID: <55A5D107.5080604@linaro.org> Date: Wed, 15 Jul 2015 11:18:31 +0800 From: Bamvor Zhang Jian User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Arnd Bergmann CC: John Stultz , Thomas Gleixner , y2038@lists.linaro.org, lkml , Baolin Wang , bamvor.zhangjian@linaro.org Subject: Re: [RFC PATCH v2 1/4] y2038: add 64bit time_t support in timeval for 32bit architecture References: <1435587807-10008-1-git-send-email-bamvor.zhangjian@linaro.org> <559E38B7.2030201@linaro.org> <1819798.ecaiCVEJzg@wuerfel> In-Reply-To: <1819798.ecaiCVEJzg@wuerfel> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Arnd On 07/09/2015 06:26 PM, Arnd Bergmann wrote: > On Thursday 09 July 2015 17:02:47 Bamvor Zhang Jian wrote: >> On 07/09/2015 04:09 AM, John Stultz wrote: >>> On Mon, Jun 29, 2015 at 7:23 AM, Bamvor Zhang Jian >>> wrote: >>>> +int get_timeval64(struct timeval64 *tv, >>>> + const struct __kernel_timeval __user *utv) >>>> +{ >>>> + struct __kernel_timeval ktv; >>>> + int ret; >>>> + >>>> + ret = copy_from_user(&ktv, utv, sizeof(ktv)); >>>> + if (ret) >>>> + return -EFAULT; >>>> + >>>> + tv->tv_sec = ktv.tv_sec; >>>> + if (!IS_ENABLED(CONFIG_64BIT) >>>> +#ifdef CONFIG_COMPAT >>>> + || is_compat_task() >>>> +#endif >>> >>> These sorts of ifdefs are to be avoided inside of functions. >> >>> Instead, it seems is_compat_task() should be defined to 0 in the >>> !CONFIG_COMPAT case, so you can avoid the ifdefs and the compiler can >>> still optimize it out. >> I add this ifdef because I got compile failure on arm platform. This >> file do not include the directly. And in arm64, >> compat.h is included implicitily. >> So, I am not sure what I should do here. Include in >> this file directly or add a this check at the beginning of this file? >> >> #ifndef is_compat_task >> #define is_compat_task() (0) >> #endif >> > > Actually I think we can completely skip this test here: Unlike > timespec, timeval is defined in a way that always lets user space > use a 64-bit type for the microsecond portion (suseconds_t tv_usec). I do not familar with this type. I grep the suseconds_t in glibc, it seems that suseconds_t(__SUSECONDS_T_TYPE) is defined as __SYSCALL_SLONG_TYPE which is __SLONGWORD_TYPE(32bit on 32bit architecture). > I think we should simplify this case and just assume that user space > does exactly that, and treat a tv_usec value with a nonzero upper > half as an error. > > I would also keep this function local to the ppdev driver, in order > to not proliferate this to generic kernel code, but that is something > we can debate, based on what other drivers need. For core kernel > code, we should not need a get_timeval64 function because all system > calls that pass a timeval structure are obsolete and we don't need > to provide 64-bit time_t variants of them. Got it. regards bamvor > > Arnd >