Re: [Qemu-devel] [PATCH v2] linux-user: Let user specify random seed

[Magnus Reftel]

On Thu, Oct 9, 2014 at 9:43 PM, Tom Musta <address@hidden> wrote:
> On 10/9/2014 3:36 AM, Magnus Reftel wrote:
>> This patch introduces the -seed command line option and the
>> QEMU_RAND_SEED environment variable for setting the random seed, which
>> is used for the AT_RANDOM ELF aux entry.
>>
>> This is an updated version of the patch, addressing review comments
>> from Eric Blake.
> Possibly a dumb question:  In a regular environment, is there a way for a 
> user to control the 16 bytes of random data
> pointed to by AT_RANDOM?  (I cannot find one).
>
> If not, why is this capability needed in Linux user mode?

The reason for this feature is to enable fully reproducible automatic
testing. You are correct that this is currently lacking in the Linux
kernel (the random bytes are always obtained using get_random_bytes).
For my purposes, having reproducibility under qemu is enough, but if
I'd be running on bare metal, I'd submit a patch for the kernel as
well.

BR
Magnus Reftel