Donenfeld: Random number generator enhancements for Linux 5.17 and 5.18

Jason Donenfeld has published a lengthy look at the changes to the Linux random-number generator (RNG) for Linux 5.17 and the upcoming 5.18 kernel. It covers his efforts "to modernize both the code and the cryptography used" and also peers into the future for changes that may be coming.

random.c was introduced back in 1.3.30, steadily grew features, and was a pretty impressive driver for its time, but after some decades of tweaks, the general organization of the file, as well as some coding style aspects were showing some age. The documentation comments were also out of date in several places. That's only natural for a driver this old, no matter how innovative it was. So a significant amount of work has gone into general code readability and maintainability, as well as updating the documentation. I consider these types of very unsexy improvements to be as important if not more than the various fancy modern cryptographic improvements. My hope is that this will encourage more people to read the code, find bugs, and help improve it. And it should make the task of academics studying and modeling the code a little bit easier.