Re: [PATCH v5 11/11] random: insist on random_get_entropy() existing in order to simplify

Jason A. Donenfeld
2022-04-23T10:00:52Z

Hi Sandy,

On Sat, Apr 23, 2022 at 10:24:07AM +0800, Sandy Harris wrote:
> On Sat, Apr 23, 2022 at 6:37 AM Jason A. Donenfeld <Jason@zx2c4.com> wrote:
> >
> > All platforms are now guaranteed to provide some value for
> > random_get_entropy(). In case some bug leads to this not being so, we
> > print a warning, ...
>
> Would it make sense to test at compile time? If there is no hardware
> RNG nor a cycle counter, then the kernel should be compiled with
> the gcc latent entropy plugin. Generate a warning suggesting that,
> or even an error insisting on it.

Unfortunately, as a last ditch warning safeguard against bugs, I don't
think that's something we can determine at build time. A lot of this
machinery is dynamic. Fortunately a single check at init time brings
with it zero appreciable overhead.

Jason