Flashing the BIOS on the PC Engines APU4c4

I absolutely love the PC Engines APU devices. I use them for testing HardenedBSD experimental features in more constrained 64-bit environments and firewalls.

Their USB and mSATA ports have a few quirks, and I bumped up against a major quirk that required flashing a different BIOS as a workaround. This article details the hacky way in which I went about doing that.

What prompted this article is that something in either the CAM or GEOM layer in FreeBSD 11.2 caused the mSATA to hang, preventing file writes. OPNsense 18.7 uses FreeBSD 11.1 whereas the recently-released OPNsense 19.1 uses HardenedBSD 11.2 (based on FreeBSD 11.2). I reached out to PC Engines directly, and they let me know that the issue is a known BIOS issue. Flashing the "legacy" BIOS series would provide me with a working system.

It also just so happens that a new "legacy" BIOS version was just released which turns on ECC mode for the RAM. So, I get a working OPNsense install AND ECC RAM! I'll have one bird for dinner, the other for dessert.

Though I'm using an APU4, these instructions should work for the other APU devices. The BIOS ROM download URLs should be changed to reflect the device you're targeting along with the BIOS version you wish to deploy.

SPECIAL NOTE: There be dragons! I'm primarily writing this article to document the procedure for my own purposes. My memory tends to be pretty faulty these days. So, if something goes wrong, please do not hold me responsible. You're the one at the keyboard. ;)

VERY SPECIAL NOTE: We'll use the mSATA drive for swap space, just in case. Should the swap space be used, it will destroy what ever is on the disk.

This post also assumes you know your way around a BSD system. You'll need to modify some commands to accomodate your setup.

Well, get on with it already!

So, you'll need a few things before we get started. You'll need to download a HardenedBSD installation image. Use the memstick image, since we're going to boot off of a USB thumbdrive.

The latest build of 12-STABLE/amd64 can be found here

Write that to your thumbdrive:

# dd if=HardenedBSD-12-STABLE-v1200058.2-amd64-mini-memstick.img \
    of=/dev/da0 bs=64k status=progress

Plug the memstick into your APU. Attach your serial cable to your system, and connect to it using cu(1) :

# cu -s 115200 -l /dev/cuaU0

When prompted, press F10 and boot from USB. You will see the HardenedBSD bootloader screen pop up. Select the third option, "Escape to Loader Prompt".

Type in the following commands for serial console access:

set comconsole_speed="115200"
set console="comconsole"
boot

You'll be prompted to select the terminal type. In my case, I enter "xterm". Next, you'll be selected with options to install HardenedBSD. Select LiveCD mode instead and login with the password-less root account.

We're going to set up swap first, in preparation for a ramdrive that will hold a chroot filesystem. We'll create a 3GB ramdisk that will hold the live environment. We'll format the ramdisk as UFS, mount it, and create two directories; one to hold a downloaded binary update and the other to hold the chroot filesystem. Following that, we'll set up networking.

# gpart destroy -F ada0
# gpart create -s gpt ada0
# gpart add -t freebsd-swap -s 2g ada0
# swapon /dev/ada0p1
# mdconfig -a -s 3g
# newfs md0
# mount /dev/md0 /mnt
# mkdir -p /mnt/update/../root
# dhclient igb0

HardenedBSD created a binary update utility for base, similar in scope to freebsd-update(8) , called hbsd-update(8) . We'll use that to populate /mnt/root . We'll then copy over /etc/resolv.conf so that DNS works within the chroot. Finally, we'll mount devfs(5) in the chroot.

# hbsd-update -VdnU -t /mnt/update -r /mnt/root
# cp /etc/resolv.conf /mnt/root/etc/
# mount -t devfs devfs /mnt/root/dev

We're now ready to dive into our chroot environment. We'll install the flashrom and ca_root_nss packages, download BIOS v4.0.23, and flash it.

VERY SPECIAL EXTRA CRUCIAL NOTE : Make sure you're downloading the right BIOS for your system! Do NOT blame me if you simply copy these next commands verbatim without first ensuring they apply to your system.

At the time of this writing (05 Feb 2019), the BIOS releases can be found here .

# chroot /mnt/root
# pkg install -y flashrom ca_root_nss
# fetch http://pcengines.ch/file/apu4_v4.0.23.rom.tar.gz
# tar -xf apu4_v4.0.23.rom.tar.gz
# flashrom -p internal:boardmismatch=force -w apu4_v4.0.23.rom

That is it! You've now flashed the "legacy" BIOS on your APU4! Go ahead and shutdown the system with shutdown -p now and go about your merry way! I know I'll be enjoying my new OPNsense 19.1 installation.

Flashing the BIOS on the PC Engines APU4c4

Flashing the BIOS on the PC Engines APU4c4

Well, get on with it already!

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