There's a guide for finding memory layouts here: https://dfhack.readthedocs.io/en/latest/library/xml/how-to-update.html
I'm not sure it still applies for 64-bit.
That's the one thing I found, but it doesn't seem applicable that much to a whole new number of bits/compiler/etc., nor does it seem that... good, really.
It's probably just me not having a grip on the memory-layouts repository yet, but when I looked at it, it seemed a bit too disorganized/cluttered for my liking (the fact that there are a number of disjoint scripts written in different languages for no discernible reason except perhaps historical happens to bug me quite a bit).
I'll be sure to check out #dfhack, and in the meantime mess around with the /proc filesystem and stuff in a little C++ program of my own, if for no other reason than I haven't done linux-specific code before

. And if making my own utility isn't good enough, I'd probably end up trying to use gdb in some way (I came across mentions of it while learning about linux memory today, so it might do the job).