would a bad modified u-boot damage BBB to ?

I just got my first BBB and try to study u-boot on it. I just wonder whether or not some bad assembly code in charge of initializing/configuring hardware would damage it or there are some important rules to follow in order to keep the board safe?
I mean I would start from a vide start.S and add code by function like 1) set cpu into svc32, 2) turn off watchdog 3) configure cpu clk 4) setup stack pointer and clear bbs …

It won’t damage the hardware. It may not work, but you can always put it back the way you got it.