As part of decommissioning mips support, remove the boot loader
support. Do this in advance of other boot loader work to limit the
amount of work that will be thrown away.

Sponsored by:		Netflix
Reviewed by:		jrtc27
Differential Revision:	https://reviews.freebsd.org/D33377

We want to keep our root file system open to preserve bcache segment
between file accesses, thus reducing physical disk IO.

Reviewed by:	imp, allanjude, kevans (previous version)
Differential Revision:	https://reviews.freebsd.org/D30848
MFC after:	1 month

MIPS BERI boot loader is built with -mno-abicalls and -fno-pic
so prevent adding PIE-related build flags.

Fix build after 9a227a2fd642 ("Enable PIE by default on 64-bit architectures")

Obtained from: Semihalf
Sponsored by: Stormshield

When performing buildworld for MIPS with PIE enabled, the build fails
with "position-independent code requires '-mabicalls'" message.
-mno-abicalls and -fno-pic flags are explicitly set in MIPS ubldr
makefile, so to work around this problem, set MK_PIE=no for MIPS
ubldr.

Submitted by: Dawid Gorecki <dgr@semihalf.com>
Reviewed by: emaste
Obtained from: Semihalf
Sponsored by: Stormshield
Differential Revision: https://reviews.freebsd.org/D28370

Need to add stub data and gfx functions to make linking happy.

- beriloader: archsw is declared extern and defined elsewhere
- ofwloader: ofw_elf{,64} are defined in elf_freebsd.c and
  ppc64_elf_freebsd.c respectively
- ubldr: syscall_ptr is defined in start.S for whichever ubldr platform is
  building

-fno-common will become the default in GCC10/LLVM11.

MFC after:	3 days

The vectx API, computes the hash for verifying a file as it is read.
This avoids the overhead of reading files twice - once to verify, then
again to load.

For doing an install via loader, avoiding the need to rewind
large files is critical.

This API is only used for modules, kernel and mdimage as these are the
biggest files read by the loader.
The reduction in boot time depends on how expensive the I/O is
on any given platform.  On a fast VM we see 6% improvement.

For install via loader the first file to be verified is likely to be the
kernel, so some of the prep work (finding manifest etc) done by
verify_file() needs to be factored so it can be reused for
vectx_open().

For missing or unrecognized fingerprint entries, we fail
in vectx_open() unless verifying is disabled.

Otherwise fingerprint check happens in vectx_close() and
since this API is only used for files which must be verified
(VE_MUST) we panic if we get an incorrect hash.

Reviewed by:	imp,tsoome
MFC after:	1 week
Sponsored by:	Juniper Networks
Differential Revision:	https://reviews.freebsd.org//D23827

BFD appears to silently truncate 0xffffffff80800000 when it processes the
ldscript for 32-bit mips, but LLD chokes on it as the linker script tries to
place elements above 32-bit range. It's unclear to me if silent truncation
is kosher or not and whether this patch is really what we want to do, but it
is one approach at least.

Reviewed by:	imp, mizhka
Differential Revision:	https://reviews.freebsd.org/D21487

NANDFS has been broken for years. Remove it. The NAND drivers that
remain are for ancient parts that are no longer relevant. They are
polled, have terrible performance and just for ancient arm
hardware. NAND parts have evolved significantly from this early work
and little to none of it would be relevant should someone need to
update to support raw nand. This code has been off by default for
years and has violated the vnode protocol leading to panics since it
was committed.

Numerous posts to arch@ and other locations have found no actual users
for this software.

Relnotes:	Yes
No Objection From: arch@
Differential Revision: https://reviews.freebsd.org/D20745

The values of the d_slice and d_partition fields of a disk_devdesc have a
few values with special meanings in the disk_open() routine. Through various
evolutions of the loader code over time, a d_partition value of -1 has
meant both "use the first ufs partition found in the bsd label" and "don't
open a bsd partition at all, open the raw slice."

This defines a new special value of -2 to mean open the raw slice, and it
gives symbolic names to all the special values used in d_slice and
d_partition, and adjusts all existing uses of those fields to use the new
constants.

The phab review for this timed out without being accepted, but I'm still
citing it below because there is useful commentary there.

Differential Revision:	https://reviews.freebsd.org/D19262