you need to install gdb (GNU Debugger)
You should get something like "Binary file mem_086cb000 matches
". Open this file in editor, search for config (e.g. "worker_connections" directive), copy&paste. Profit!
Update: This method isn't entirely reliable. It's based on assumption that nginx process will read configuration and don't overwrite/reuse this memory area later. Master nginx process gives us best chances for that I guess.
Thanks for the tips !