How to verify NX CPU bit usage by Linux kernel?

I'd like to verify that the current system is using NX bit protection somehow. I know that this can be done by checking the initial lines in the dmesg output. But that's a rolling buffer, so I'm not always going to be able to do it on a long-running system. Is there another way to verify the NX usage? I can't see any relevant /proc file. I was thinking of checking the memory maps for the loaded modules (is the data section executable), but I can't find any place where I could get them from. I'm trying to check that with root privileges, but passively (I know you could write a module to do the check actively, but don't want to go that far).