Additional interface to kernel timekeeping for leapsecond clarity

[Watson Ladd]

Dear all,

I'm writing because I'm interested in adding a system call to linux
and other free operating systems that will return the current time in
a structure that will include a flag for whether or not there is a
leap second when the result is taken. While adjtimex exists, it's a
very heavy interface to this functionality. This is necessary for
computing the Modified Julian Day+microseconds since midnight in
userspace, something of interest for roughtime.

ntp_gettimex doesn't quite do this either: the TAI offset doesn't let
one compute the Modified Julian day without an almanac. To the best of
my knowledge this doesn't exist yet, but I would be happy to be proven
wrong.

Adding this would make it possible to adapt userspace to the harsh
realities of UTC.

Sincerely,
Watson Ladd