Re: [PATCH] crypto: jitterentropy - bind statically into kernel

[Ard Biesheuvel]

On Mon, 5 Oct 2020 at 08:19, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
>
> On Sun, Oct 04, 2020 at 11:16:10PM +0200, Ard Biesheuvel wrote:
> > On Sun, 4 Oct 2020 at 20:48, Stephan M??ller <smueller@xxxxxxxxxx> wrote:
> > >
> > > The RISC-V architecture is about to implement the callback
> > > random_get_entropy with a function that is not exported to modules.
> >
> > Why is that? Wouldn't it be better to export the symbol instead?
>
> get_cycles is a low-level time keeping detail that really should not
> be exported, and at least for RISC-V this would be the only modular
> user.  Once that is sorted out I'll audit other common architectures
> to drop the export, as it isn't something that should be used in ramdom
> driver code.

Fair enough.

But this means we should fix the jitterentropy driver rather than
sidestepping the issue by only allowing it to be built in a way where
we don't happen to notice that the symbol in question is not meant for
general consumption.

If jitterentropy is a special case, we could put a alternate
non-'static inline' version of random_get_entropy() in the core
kernel, and only export it if JITTER_ENTROPY is built as a module in
the first place. But I'd prefer it if jitterentropy switches to an API
that is suitable for driver consumption.