interfaces that don't make sense for times in the past Here, we are relatively free to change the start of the epoch in the kernel but convert to something else on the user space boundary. One possibility is to scale them to boot time and use ktime_t in the kernel.
[Does checkpoint/restore have any implications here wrt to how freely we can change the start of the epoch? E.g., when freezing/restoring processed from different systems that have timer_settime() timers?]
interfaces that require absolute times These absolutely have to use something better than time_t both in user space and in the kernel so we can deal with old files. A lot of file systems need to be fixed as well so we can actually store the times, regardless of whether we are running a 32 or 64 bit kernel.
memory mapped packet sockets Socket timestamps are exported to user space using a memory mapped interface defined in include/uapi/linux/if_packet.h. There are currently three versions of this interface, all use a 32-bit time type. We will likely need a version 4 to solve this.
sys_time sys_stime sys_nanosleep sys_clock_settime sys_clock_gettime sys_clock_getres sys_clock_nanosleep sys_sched_rr_get_interval sys_futex sys_rt_sigtimedwait sys_io_getevents sys_recvmmsg sys_semtimedop sys_mq_timedsend sys_mq_timedreceive sys_utimensat sys_pselect6 sys_ppoll sys_gettimeofday sys_settimeofday sys_utimes sys_select sys_futimesat sys_utime sys_timer_gettime sys_timer_settime sys_timerfd_settime sys_timerfd_gettime sys_wait4 sys_waitid sys_getrusage sys_getitimer sys_setitimer sys_adjtimex sys_clock_adjtime