Early beta releases of macOS Big Sur had a signed/unsigned error in
Apple's implementation of ntp_adjtime. Apple have since fixed this error
and the workaround is no longer required.
On macOS 11.0 (Big Sur) beta, ntp_adjtime() incorrectly returns
timex.freq as an unsigned number. This patch is a workaround for the bug
and should be removed when Apple fix the problem (assuming they will).
Call exit() in LOG_Message() after printing a fatal message to allow the
LOG macro or LOG_Message() to be used directly instead of the LOG_FATAL
macro.
The tai field in struct timex is a Linux-specific feature. It's possible
to read the current offset with ntp_gettime() (or ntp_gettimex() on
Linux), but apparently not all libc implementations support it.
Rework the code to save and adjust the last value instead of reading
the current value from the kernel.
It was never used for anything and messages in debug output already
include filenames, which can be easily grepped if there is a need
to see log messages only from a particular file.
The system drivers may implement their own slewing which the generic
driver can use to slew faster than the maximum frequency the driver is
allowed to set directly.
This is based on sys_linux.c and wrap_adjtimex.c. It's intended for all
systems that support the adjtimex() or ntp_adjtime() system call. The
driver functions can be replaced with extended system-specific versions
(e.g. to control the frequency with the tick field on Linux).
