On Mon, May 14, 2018 at 10:53 AM, Kees Cook <keescook@xxxxxxxxxxxx> wrote: > On Mon, May 14, 2018 at 10:25 AM, Deepa Dinamani <deepa.kernel@xxxxxxxxx> wrote: >> On Mon, May 14, 2018 at 9:30 AM, Kees Cook <keescook@xxxxxxxxxxxx> wrote: >>> On Sun, May 13, 2018 at 9:05 PM, Deepa Dinamani <deepa.kernel@xxxxxxxxx> wrote: >>>> Kees mentioned that he wants to merge a patch to pstore that changes >>>> it to use timespec64 internally for 4.17: >>>> https://lkml.org/lkml/2018/5/13/3 >>> >>> I'm still working on a v2 for pstore. What is the correct >>> cross-architecture format string for timespec64's tv_sec? In your >>> other patches, you're using %lld and a (long long) cast. I'd really >>> like to avoid the need for casts. >> >> We cannot really avoid it for now. >> struct timespec64 is defined this way for now: >> >> struct timespec { >> __kernel_time_t tv_sec; /* seconds */ >> long tv_nsec; /* nanoseconds */ >> }; >> >> #if __BITS_PER_LONG == 64 >> /* this trick allows us to optimize out timespec64_to_timespec */ >> # define timespec64 timespec >> >> #else >> >> struct timespec64 { >> time64_t tv_sec; /* seconds */ >> long tv_nsec; /* nanoseconds */ >> }; >> >> #endif >> >> This will all lead to tv_sec being long on a 64 bit architecture and >> long long on a 32 bit architecture. >> So there is no way of avoiding the cast for now. >> >> We plan to get rid of this trick and to have a single definition for >> timespec64. But, that cleanup is planned for later when we cleanup all >> struct timespec uses internally. > > Can we do something like: > > #if __BITS_PER_LONG == 64 > # define TVSEC_FMT "%ld" > #else > # define TVSEC_FMT "%lld" > #endif > > so we can do stuff like: sprintf(buf, "seconds: " KTIME_FMT, time->tv_sec) > > ? It seems easier to clean up than casts. We have already introduced these casts in many places now. It would be easier to do the clean up if they all follow a similar pattern. ( I could probably write a coccinelle script that is not very long). But, it would be not much trouble if you wanted to follow this for pstore. We also contemplated adding a format specifier for time. But, I think we deferred it until we have a uniform way of using time internally. -Deepa
