MFC r359938:

Remove bogus use of useracc() in (clock_)nanosleep.

There's no point in pre-checking that we can access the user's rmtp
pointer before we do it in copyout().

While here, improve style(9) compliance.

Reviewed by: imp
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D24409

MFC r335553: Make CLOCK_PROCESS_CPUTIME_ID more accurate by including
the current timeslice, matching the behaviour of CLOCK_VIRTUAL and
CLOCK_PROF.

Revert r330897:

This was intended to be a non-functional change. It wasn't. The commit
message was thus wrong. In addition it broke arm, and merged crypto
related code.

Revert with prejudice.

This revert skips files touched in r316370 since that commit was since
MFCed. This revert also skips files that require $FreeBSD$ property
changes.

Thank you to those who helped me get out of this mess including but not
limited to gonzo, kevans, rgrimes.

Requested by: gjb (re)

Partial merge of the SPDX changes

These changes are incomplete but are making it difficult
to determine what other changes can/should be merged.

No objections from: pfg

MFC r329271:

nanosleep(2): Fix bogus incrementing of rmtp by tc_tick_sbt on [EINTR].

MFC r315526

Add clock_nanosleep()

Add a clock_nanosleep() syscall, as specified by POSIX.
Make nanosleep() a wrapper around it.

Attach the clock_nanosleep test from NetBSD. Adjust it for the
FreeBSD behavior of updating rmtp only when interrupted by a signal.
I believe this to be POSIX-compliant, since POSIX mentions the rmtp
parameter only in the paragraph about EINTR. This is also what
Linux does. (NetBSD updates rmtp unconditionally.)

Copy the whole nanosleep.2 man page from NetBSD because it is complete
and closely resembles the POSIX description. Edit, polish, and reword it
a bit, being sure to keep any relevant text from the FreeBSD page.

Regenerate syscall files.

Relnotes: yes
Sponsored by: Dell EMC

MFC r315510

nanosleep: plug a kernel memory disclosure

nanosleep() updates rmtp on EINVAL. In that case, kern_nanosleep()
has not updated rmt, so sys_nanosleep() updates the user-space rmtp
by copying garbage from its stack frame. This is not only a kernel
memory disclosure, it's also not POSIX-compliant. Fix it to update
rmtp only on EINTR.

Security: possibly
Sponsored by: Dell EMC

MFC r303388:
Remove Giant from settime().

MFC r302770:
Trace timeval parameters to the getitimer(2) and setitimer(2) syscalls.

Approved by: re (gjb)