MFC r334310, r334337:

r334310 (imp):
Teach ufs_module.c about bsd labels and probe 'a' partition.

If the check for a UFS partition at offset 0 on the disk fails, check
to see if there's a BSD disklabel at block 1 (standard) or at offset
512 (install images assume 512 sector size). If found, probe for UFS
on the 'a' partition.

This fixes UEFI booting images from a BSD labeled MBR slice when the
'a' partiton isn't at offset 0. This is a stop-gap fix since we plan
on removing boot1.efi in FreeBSD 12. We can't easily do that for 11.2,
however, hence the short MFC window.

r334337 (emaste):
switch amd64 memstick installer images to MBR

A good number of BIOSes have trouble booting from GPT in non-UEFI
mode.

With this change amd64 memsticks remain dual-mode (booting from either
UEFI or CSM); the partitioning type is just switched from GPT to MBR.

PR: 227954

Note, there are two changes specific to stable/11 where there is code
that had diverged from head and never merged back. The two changes are
an include in stand/efi/boot1/ufs_module.c, replacing sys/disk/bsd.h
with sys/disklabel.h and replacing BSD_MAGIC with DISKMAGIC in the
same file. The latter two are direct commits to stable/11 in order to
avoid unexpected regressions at this point of the 11.2 cycle. Thank
you to imp@ for pointing out what changes needed to be made.

Approved by: re (marius)

Sponsored by: The FreeBSD Foundation

MFC r332390: make-memstick.sh: put partition args on separate lines

This makes it easier to identify the individual partition types and
facilitates comparisons across architectures.

Sponsored by: The FreeBSD Foundation

MFC r323438: make-memstick.sh: use UFSv2

There's not much practical difference as far as install media is
concerned but newfs creates UFSv2 by default and it is sensible to use
the contemporary UFS version.

I also intend to change makefs to create UFSv2 by default (to match
newfs) so we'll want make-memstick.sh to be explicit, rather than
relying on the host tool's default.

Sponsored by: The FreeBSD Foundation

make-memstick.sh: use 'set -e' to abort if any step fails

Also remove the now-redundant error handling that was only for makefs.

This script was run on an older FreeBSD host that lacked efi-on-mbr
support in makefs. A warning was emitted on the console (from makefs)
but the script continued running and exited with 0.

MFC of r308171 (arm64) and r323178 (other architectures).

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Prevent memstick installation medium from attempting to mount
the root filesystem read-write. This causes problems booting
the memstick installation medium from write-protected USB flash
drives.

Submitted by: A.J. Kehoe IV [1], Oliver Jones [2]
PR: 187161 [1], 205886 [2]
MFC after: 1 week
Sponsored by: The FreeBSD Foundation

Now that GENERIC can boot on UEFI systems (r268158), switch the build to use
UEFI-compatible images. These will boot as before on BIOS systems, but will
boot using the UEFI loader on UEFI-aware systems.

loader's GPT support on BIOS does not seem to like the root filesystem
being the last filesystem on the disk for some reason when made by this
script. Add a vestigial swap partition to allow this to boot with QEMU
BIOS.

Make a dual-boot BIOS/UEFI memstick image. Testing required before this gets
renamed make-memstick.sh.

Add a separate script to build the memstick.img and the
mini-memstick.img with UEFI support.

As the comments in the file suggest, 1) there must
be existing ${.OBJDIR}/usr/src/release/{release,bootonly};
2) TARGET/TARGET_ARCH must be amd64; and 3) it must be
a vt(4)-enabled kernel with vt_efifb (*not* vt_vga).

This script is not hooked into release/Makefile in any way
until further testing is complete.

Sponsored by: The FreeBSD Foundation