Re: Standardizing an MSR or other hypercall to get an RNG seed?

Christopher Covington
2014-09-22T13:33:41Z

On 09/19/2014 02:42 PM, Andy Lutomirski wrote:
> On Fri, Sep 19, 2014 at 11:30 AM, Christopher Covington
> <cov@codeaurora.org> wrote:
>> On 09/17/2014 10:50 PM, Andy Lutomirski wrote:
>>> Hi all-
>>>
>>> I would like to standardize on a very simple protocol by which a guest
>>> OS can obtain an RNG seed early in boot.
>>>
>>> The main design requirements are:
>>>
>>> - The interface should be very easy to use. Linux, at least, will
>>> want to use it extremely early in boot as part of kernel ASLR. This
>>> means that PCI and ACPI will not work.
>>
>> How do non-virtual systems get entropy this early? RDRAND/Padlock? Truerand?
>> Could hypervisors and simulators simply make sure these work?
>>
>
> If RDRAND is available, then Linux, at least, will use it. The rest
> are too complicated for early use. Linux on x86 plays some vaguely
> clever games with rdtsc and poking at the i8254 port.

I just wanted to check that it couldn't be as simple as giving one or both of
the timers random initial values.

Christopher

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