On 17/09/2019 22.58, Linus Torvalds wrote: > Side note, and entirely unrelated to this particular problem, but > _because_ I was looking at the entropy init and sources of randomness > we have, I notice that we still don't use the ToD clock as a source. And unrelated to the non-use of the RTC (which I agree seems weird), but because there's no better place in this thread: How "random" is the contents of RAM after boot? Sure, for virtualized environments one probably always gets zeroed pages from the host (otherwise the host has a problem...), and on PCs maybe the BIOS interferes. But for cheap embedded devices with non-ECC RAM and not a lot of value-add firmware between power-on and start_kernel(), would it make sense to read a few MB of memory outside of where the kernel was loaded and feed those to add_device_randomness() (of course, doing it as early as possible, maybe first thing in start_kernel())? Or do the reading in the bootloader and pass on the sha256() in the DT/rng-seed property? A quick "kitchen-table" experiment with the board I have on my desk shows that there are at least some randomness to be had after a cold boot. Maybe this has already been suggested and rejected? Rasmus
