But, my /proc/cpuinfo (I am using Linaro on an SD) gives 0000000000000000 for the serial number.
There is no u-boot environment variable named "serial" either.
There is a u-boot environment variable named "dieid#", but I can change it, and we have one system that writes the entire u-boot environment block on setup, and in any case it can't be trusted.
So the question remains, is there some kind of software-readable, unique, invariant serial number that can be read from these boards? The wiki seems to be entirely off.