sys: Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

linuxkpi: Add __copy_to_user_inatomic and __copy_from_user_inatomic

Reviewed by: bz
Obtained from: drm-kmod
Sponsored by: Beckhoff Automation GmbH & Co. KG
Differential Revision: https://reviews.freebsd.org/D36113

LinuxKPI: Constantly use _LINUXKPI_ prefix in include guards

MFC after: 1 week
Reviewed by: bz, emaste, hselasky, manu
Differential Revision: https://reviews.freebsd.org/D33562

LinuxKPI: remove < 5.0 version support

We are not aware of any out-of-tree consumers anymore
which would need KPI support for before Linux version 5.
Update the two in-tree consumers to use the new KPI.
This allows us to remove the extra version check and
will also give access to {lower,upper}_32_bits() unconditionally.

Sponsored-by: The FreeBSD Foundation
Reviewed-by: hselasky, rlibby, rstone
MFC-after: 2 weeks
X-MFC: to 13 only
Differential Revision: https://reviews.freebsd.org/D29391

LinuxKPI: Update access_ok macro for v5.0.

Check LINUXKPI_VERSION macro for backwards compatibility.
It's recommended to update any drivers that depend on the older KPI
so we can deprecate < 5.0 code as we update to newer Linux version.
This patch is part of D19565

Reviewed by: hps
Approved by: imp (mentor), hps
MFC after: 1 week

Allow the put_user() function macro to put constant values by using the
existing __put_user() macro.

MFC after: 1 week
Submitted by: Johannes Lundberg <johalun0@gmail.com>
Sponsored by: Mellanox Technologies

Add comment describing the use of pagefault_disable() and
pagefault_enable() in the LinuxKPI.

Suggested by: rpokala@
MFC after: 1 week
Sponsored by: Mellanox Technologies

The LinuxKPI pagefault disable and enable functions can only be used
pairwise to support the FreeBSD way of pushing and popping the page
fault flags. Ensure this by requiring every occurrence of pagefault
disable function call to have a corresponding pagefault enable call.

Obtained from: kmacy @
MFC after: 1 week
Sponsored by: Mellanox Technologies

Implement more userspace memory access functions in the LinuxKPI.

Obtained from: kmacy @
MFC after: 1 week
Sponsored by: Mellanox Technologies

Fix handling of IOCTLs in the LinuxKPI.

Linux requires that all IOCTL data resides in userspace. FreeBSD
always moves the main IOCTL structure into a kernel buffer before
invoking the IOCTL handler and then copies it back into userspace,
before returning. Hide this difference in the "linux_copyin()" and
"linux_copyout()" functions by remapping userspace addresses in the
range from 0x10000 to 0x20000, to the kernel IOCTL data buffer.

It is assumed that the userspace code, data and stack segments starts
no lower than memory address 0x400000, which is also stated by "man 1
ld", which means any valid userspace pointer can be passed to regular
LinuxKPI handled IOCTLs.

Bump the FreeBSD version to force recompilation of all kernel modules.

Discussed with: kmacy @
MFC after: 1 week
Sponsored by: Mellanox Technologies

Define __get_user() and __put_user() for the LinuxKPI.

MFC after: 1 week
Sponsored by: Mellanox Technologies

Finish process of moving the LinuxKPI module into the default kernel build.

- Move all files related to the LinuxKPI into sys/compat/linuxkpi and
its subfolders.
- Update sys/conf/files and some Makefiles to use new file locations.
- Added description of COMPAT_LINUXKPI to sys/conf/NOTES which in turn
adds the LinuxKPI to all LINT builds.
- The LinuxKPI can be added to the kernel by setting the
COMPAT_LINUXKPI option. The OFED kernel option no longer builds the
LinuxKPI into the kernel. This was done to keep the build rules for
the LinuxKPI in sys/conf/files simple.
- Extend the LinuxKPI module to include support for USB by moving the
Linux USB compat from usb.ko to linuxkpi.ko.
- Bump the FreeBSD_version.
- A universe kernel build has been done.

Reviewed by: np @ (cxgb and cxgbe related changes only)
Sponsored by: Mellanox Technologies