RPi3 boot stops at Using DTB provided by EFI at 0x8004000.

[bob prohaska]

An RPi3 hangs on boot with the console message
Using DTB provided by EFI at 0x8004000.

The system just completed an OS build/install cycle on r331088, the
only obvious change is some additional console output, which ends with

>> FreeBSD EFI boot block
   Loader path: /boot/loader.efi

   Initializing modules: ZFS UFS
   Probing 5 block devices......** done
    ZFS found no pools
    UFS found 2 partitions
Consoles: EFI console  
Command line arguments: loader.efi
Image base: 0x379ad008
EFI version: 2.05
EFI Firmware: Das U-boot (rev 0.00)

FreeBSD/arm64 EFI loader, Revision 1.1
(Sun Mar 18 04:46:21 PDT 2018 bob at www.zefox.org)
   BootCurrent: 0000
   BootOrder: 0004 0000[*] 0000[*] 0000[*] 5990 3af8 0000[*] 0000[*] ed78 3ab2 0000[*] 0000[*] 28ec 3af6 0000[*] 0000[*] 0067 0000[*] 0000[*] 0000[*] 02e0 3ab4 0000[*] 0000[*] 5000 3af8 0000[*] 0000[*] ee20 3ab2 0000[*] 0000[*] 2a48 3af6 0000[*] 0000[*] 5990 3af8 0000[*] 0000[*] 6000 3794 0000[*] 0000[*] 6000 3394 0000[*] 0000[*] 4000 0000[*] 0000[*] 0000[*] d520 3ab3 0000[*] 0000[*] 5000 3af8 0000[*] 0000[*] 4000 0000[*] 0000[*] 0000[*] 1000 0000[*] 0000[*] 0000[*] 6000 3394 0000[*] 0000[*] 0000[*] 0000[*] 0000[*] 0000[*] 0000[*] 0000[*] 0000[*] 0000[*] 0000[*] 0000[*] 0000[*] 0000[*] 0000[*] 0000[*] 0000[*] 0000[*] 02e0 3ab4 0000[*] 0000[*] 0000[*] 0000[*] 0000[*] 0000[*] ff20 3ab3 0000[*] 0000[*]
Loading /boot/defaults/loader.conf
/boot/kernel/kernel text=0x4e1587 data=0xe7320+0x70243c syms=[0x8+0x9e2b0+0x8+0x7e497]
/boot/entropy size=0x1000

Hit [Enter] to boot immediately, or any other key for command prompt.
Booting [/boot/kernel/kernel]...               
Using DTB provided by EFI at 0x8004000.

At this point the machine becomes stuck. Power-cycling allows an older
kernel, built on r326343, to come up normally. Both the functional and
non-functional kernels were built using a custom config file, which can
be seen at http://www.zefox.net/~fbsd/rpi3/kernel_config/ZEFOX

Thanks for reading, I'd be grateful for any workarounds.

bob prohaska