Re: [PATCH v3 2/5] random,x86: Add arch_get_slow_rng_u64

Daniel Borkmann
2014-07-17T12:39:42Z

On 07/17/2014 12:59 AM, H. Peter Anvin wrote:
> On 07/16/2014 03:40 PM, Andy Lutomirski wrote:
>> On Wed, Jul 16, 2014 at 3:13 PM, Andy Lutomirski <luto@amacapital.net> wrote:
>>> My personal preference is to defer this until some user shows up. I
>>> think that even this would be too complicated for KASLR, which is the
>>> only extremely early-boot user that I found.
>>>
>>> Hmm. Does the prandom stuff want to use this?
>>
>> prandom isn't even using rdrand. I'd suggest fixing this separately,
>> or even just waiting until someone goes and deletes prandom.
>
> prandom is exactly the opposite; it is designed for when we need
> possibly low quality random numbers very quickly. RDRAND is actually
> too slow.

Yep, prandom() is quite heavily used in the network stack where it's
traded for speed.