MFC r281829 (by trasz@):

Modify kern___getcwd() to take max pathlen limit as an additional
argument. This will be used for the Linux emulation layer - for Linux,
PATH_MAX is 4096 and not 1024.

MFC r317845-r317846

r317845:
Provide a freebsd32 implementation of sigqueue()

The previous misuse of sys_sigqueue() was sending random register or
stack garbage to 64-bit targets. The freebsd32 implementation preserves
the sival_int member of value when signaling a 64-bit process.

Document the mixed ABI implementation of union sigval and the
incompability of sival_ptr with pointer integrity schemes.

Reviewed by: kib, wblock
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D10605

r317846:
Regen post r317845.

MFC with: r317845
Sponsored by: DARPA, AFRL

MFC r313715:
Order alphabetically.

MFC r283440:

For future use in the Linuxulator:

1. Add a kern_kqueue() counterpart for kqueue() with flags parameter.

2. Be a bit secure. To avoid a double fp lookup add a kern_kevent_fp()
counterpart for kern_kevent() with file pointer parameter instead
of file descriptor an pass the buck to it.

Suggested by: mjg [2]

MFC r283377:

In preparation for switching linuxulator to the use the native 1:1
threads split sys_sched_getparam(), sys_sched_setparam(),
sys_sched_getscheduler(), sys_sched_setscheduler() to their kern_*
counterparts and add targettd parameter to allow specify the target
thread directly by callee.

MFC r283374:

In preparation for switching linuxulator to the use the native 1:1
threads refactor kern_sched_rr_get_interval() and sys_sched_rr_get_interval().
Add a kern_sched_rr_get_interval() counterpart which takes a targettd
parameter to allow specify target thread directly by callee (new Linuxulator).

Linuxulator temporarily uses first thread in proc.

Move linux_sched_rr_get_interval() to the MI part.

MFC r283373:

In preparation for switching linuxulator to the use the native 1:1
threads introduce kern_thr_alloc() which will be used later in the
linux_clone().

MFC r283372:

In preparation for switching linuxulator to the use the native 1:1
threads split sys_thr_exit() up into sys_thr_exit() and kern_thr_exit().
Move
Where the second will be used in linux_exit() system call later.

MFC r277610 (by jillies):

Add futimens and utimensat system calls.

MFC r276564, r276654:

Cast *path to silence clang -Wpointer-sign warning.

Indeed, instead of hiding the kern___getcwd() bug by bogus cast
in r276564, change path type to char * (pathnames are always char *).
And remove bogus casts of malloc().
kern___getcwd() internally doesn't actually use or support u_char *
paths, except to copy them to a normal char * path.

These changes are not visible to libc as libc/gen/getcwd.c misdeclares
__getcwd() as taking a plain char * path.

While here remove _SYS_SYSPROTO_H_ for __getcwd() syscall as
we always have sysproto.h.

MFC r274462: Add the ppoll() system call.

MFC r272132:
Fix fcntl(2) compat32 after r270691.

Approved by: re (glebius)

MFC r269669:

Split up sys_ktimer_getoverrun() into a sys_ and a kern_ variant
and export the kern_ version needed by an upcoming linuxolator change.

Sponsored by: DARPA,AFRL

MFC r276564, r276654:

Cast *path to silence clang -Wpointer-sign warning.

Indeed, instead of hiding the kern___getcwd() bug by bogus cast
in r276564, change path type to char * (pathnames are always char *).
And remove bogus casts of malloc().
kern___getcwd() internally doesn't actually use or support u_char *
paths, except to copy them to a normal char * path.

These changes are not visible to libc as libc/gen/getcwd.c misdeclares
__getcwd() as taking a plain char * path.

While here remove _SYS_SYSPROTO_H_ for __getcwd() syscall as
we always have sysproto.h.

MFC r274462: Add the ppoll() system call.

MFC r272132:
Fix fcntl(2) compat32 after r270691.

Approved by: re (glebius)

MFC r269669:

Split up sys_ktimer_getoverrun() into a sys_ and a kern_ variant
and export the kern_ version needed by an upcoming linuxolator change.

Sponsored by: DARPA,AFRL