On Tue, Apr 8, 2025, at 22:37, Kees Cook wrote: > On April 8, 2025 2:22:52 AM PDT, Arnd Bergmann <[email protected]> wrote: >>> >>> indicates that Talos 1.9.1 uses latent_entropy (but we didn't check how >>> accurate that survey is). > > The early RNG for small machines remains pretty bad, so I can > understand wanting to keep that around. For bigger machines it's not as > much of a benefit.
Does "small machines" still mean those without a cycle counter as in the 2009 article [https://phrack.org/issues/66/15#article] or are you thinking of those that may have a working random_get_entropy() but that remains too predictable for add_device_randomness() because of the low frequency (e.g. 19.2 MHz on many ARMv7/v8)? The former (ARMv5, AMD Elan, Xburst) were still common back then but are mostly extinct now, while the latter obviously remain in wide use. >>Talos also uses stackleak. I also see that alpine and qubes have the >>same two gcc plugins enabled. > > Yeah, stackleak has no viable alternative. It's effectively > init_on_free for stack. It's be nice if there were a way to do this > with upstream compilers (track call depth). I guess a simplified version could in theory be done in the kernel using _mcount without compiler help, but that would be much more expensive if every function entry has to call it, right? Arnd
