. with hz=1000, clock_t only lasts a few years.
whenever we can't express the desired realtime
in ticks because the distance with boottime is
too high, simply adjust bootime like we do for
otherwise negative values.
. fixes test 2 on ARM
This also adds the sys_settime() kernel call which allows for the adjusting
of the clock named realtime in the kernel. The existing sys_stime()
function is still needed for a separate job (setting the boottime). The
boottime is set in the readclock driver. The sys_settime() interface is
meant to be flexible and will support both clock_settime() and adjtime()
when adjtime() is implemented later.
settimeofday() was adjusted to use the clock_settime() interface.
One side note discovered during testing: uptime(1) (part of the last(1)),
uses wtmp to determine boottime (not Minix's times(2)). This leads `uptime`
to report odd results when you set the time to a time prior to boottime.
This isn't a new bug introduced by my changes. It's been there for a while.
