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. -Kees -- Kees Cook Pixel Security
