First, you will need a few things.

(1) My latest branch at https://github.com/bsdimp/freebsd/tree/boot-linuxboot
 (so the boot-linuxboot branch of my freebsd tree, it's sync to Friday).

(2) a small cache of binaries. You'll need to put these into
 ~/stand-test-root/cache. You can find the tarball at
 freefall.freebsd.org:~imp/cache.tar. You can just extract this in ~. These are
 the linux kernels I'm testing with.

(3) The latest qemu-system-aarch64 (I think ports/pkg version of emulators/qemu
 is recent enough). If not, I know the latest master of qemu project works.

(4) A recent enough universe that the building of stand will work for all the
 architectures that I build. You can hack the ARCHES line near the top of
 tools/boot/full-test.sh if need be, but you'll need at least amd64, arm64 and
 maybe riscv (I don't have a good way to filter arches in this script yet, since
 it's at an early state of development.

(5) Build the kernel for at least arm64 and use it as an 'override'. I do this
 by sudo -E make installkernel
 DESTDIR=$HOME/stand-test-root/override/arm64-aarch64 TARGET=arm64 after
 building the kernel. The script is designed to use kernels and binaries from
 the latest CDs to do the testing, but has a way to override the kernel and
 since we need to fix arm64...

(6) You'll need to build the images. If you've done 1-5 correctly (and I've not
 missed anything), then "cd <mumble>/src; sh tools/boot/full-test.sh" will create
 all the images and scripts to run qemu. There should be no errors, though
 warnings about zfs.ko etc missing from powerpc is fine (and ignored by the
 script already).

(7) There will be a script to recreate this created in
 $HOME/stand-test-root/scripts/arm64-aarch64/linuxboot-test.sh. Just run it with
 'sh'. And extra args are passed to qemu, so '-s -S' for gdb and
 '-d trace:gicv3\* -D /tmp/gic.log' for verbose gic tracing (spaces are important).

There's also a linuxboot-test-raw.sh which boots w/o EDK2+Linux.efi but loads
the kernel directly. and freebsd-test.sh which uses EDK2+loader.efi to boot FreeBSD
w/o kboot at all.