This series of patches is not strictly necessary, but it is a significant improvement. The current code has a sequence in several places that calls one or more of arch_get_random_long() or related functions, checks the return value(s) and on failure falls back to random_get_entropy(). These patches provide get_source_long(), which is intended to replace all such sequences. This is better in several ways. It never wastes effort by calling arch_get_random_long() et al. when the relevant config variables are not set. If config variables for a hardware rng or the latent entropy plugin are set, then it uses those instead. It does not deliver raw output from any of these sources, but masks it by mixing with stored random data. In the fallback case it gives much more random output In the cases where a good source is available, this adds a little overhead, but not much. It also saves some by not trying arch_get-random_long() unnecessarily. If no better source is available, get_source_long() falls back to get_xtea_long(), an internal-use-only pseudorandom generator based on the xtea block cipher. In general, that is considerably more expensive than random_get_entropy(), but also provably much stronger. With no good source, there is still a problem at boot; xtea cannot become secure until it is properly keyed. It does become safe eventually, and in the meanwhile it is certainly no worse than random_get_entropy().
