Kexec not working, unknown rel relocation: 43

I'm trying to get kexec to work, but haven't had any luck. I set up a VM on Virtualbox using openwrt-19.07.7-x86-generic-combined-ext4.img.gz, installed kexec and kexec-tools, then ran

kexec -l /boot/vmlinuz --append='root=PARTUUID... rootfstype=ext4 noinitrd'

But I got

Unknown rel relocation: 43

I googled the error a bit, but only got as far as it not being common, coming from busybox, and having something to do with elf.