linux-kernel - Re: [RFC PATCH v12 1/4] crypto: make Jitter RNG directly accessible

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Date:   Tue, 18 Jul 2017 11:02:02 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Stephan Müller <smueller@...onox.de>,
        "Jason A. Donenfeld" <jason@...c4.com>,
        linux-crypto@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v12 1/4] crypto: make Jitter RNG directly accessible

On Tue, Jul 18, 2017 at 10:49 AM, Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
> On Tue, Jul 18, 2017 at 10:40:07AM +0200, Stephan Müller wrote:
>> Am Dienstag, 18. Juli 2017, 10:30:14 CEST schrieb Greg Kroah-Hartman:
>>
>> Hi Greg,
>>
>> > > +typedef  unsigned long long      __u64;
>> > > +typedef  long long               __s64;
>> >
>> > types.h already has these defines, don't re-typedef them again...
>>
>> The issue is that the C code is compiled without optimizations. Thus, the C
>> code shall not depend on any other header file.
>
> That is very strange for a kernel file, I don't know what to say...
>
>> This issue was discussed during the inclusion of the Jitter RNG C code into
>> the kernel.
>
> Ok, that was then, this is now, why not change it now?  How does
> including types.h change anything?

I can see why the jitterentropy implementation avoids using kernel headers,
the problem now is that part of it gets moved into a new header, and that
already violates the original principle.

>From my reading of the code, we could probably leave the structure
definition in the crypto/jitterentropy.c, and have the statically
allocated instance in the same file when CONFIG_LRNG is
set, or provide a way to allocate an instance early (I assume you
can't call jent_entropy_collector_alloc() here since you need
the RNG long before kzalloc() works).

        Arnd