Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [RFC PATCH v2 1/4] y2038: add 64bit time_t support in timeval for 32bit architecture | Date | Wed, 15 Jul 2015 11:33:33 +0200 |
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On Wednesday 15 July 2015 11:18:31 Bamvor Zhang Jian wrote: > 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).
Correct, but POSIX allows it to be redefined along with time_t, so timeval can be a pair of 64-bit values. In contrast, timespec is required by POSIX (and C11) to be a time_t and a 'long', which is why we need a hack to check the size of the second word of the timespec structure.
Arnd
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