Messages in this thread | | | Date | Wed, 15 Jul 2015 11:18:31 +0800 | From | Bamvor Zhang Jian <> | Subject | Re: [RFC PATCH v2 1/4] y2038: add 64bit time_t support in timeval for 32bit architecture |
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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 >>> <bamvor.zhangjian@linaro.org> 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 <linux/compat.h> directly. And in arm64, >> compat.h is included implicitily. >> So, I am not sure what I should do here. Include <linux/compat.h> 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 >
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