This started out as a patch adding a syscall wrapper for the two
functions. It still does that, but along the way I (or rather AI)
discovered an edge case in the truncation of microsecond values, where
we could turn bogus values into seemingly valid ones by throwing away
the high-order bits.
Additionally, when writing a test case, I noticed that the (64-bit)
kernel returns EINVAL for these out-or-range values. Our check returns
EOVERFLOW in this case, so I also change our error code in order to
provide an uniform behavior for the test case.
Neither of these (the check and the EINVAL error code) are present in
glibc (which lets truncated usec values through and returns EOVERFLOW on
second truncation), but I think it's better to be consistent with the
64-bit behavior. The EOVERFLOW error also has no foundation in POSIX
whereas EINVAL is mentioned as an error for invalid microseconds.
While in there, I also define ITIMER_REAL, ITIMER_VIRTUAL, and
ITIMER_PROF in linux/sys-time-macros.h and update code to use them
instead of raw numbers.
Assisted by Gemini.
Pavel Labath
9a4ad0acce