Re: [PATCH RFC] random: Account for entropy loss due to overwrites

From: H. Peter Anvin
Date: Tue Oct 16 2012 - 00:45:16 EST

On 10/15/2012 09:08 PM, Theodore Ts'o wrote:
> On Sat, Sep 29, 2012 at 12:47:04PM -0700, H. Peter Anvin wrote:
>>> -static struct poolinfo {
>>> +static const struct poolinfo {
>>> + int poolshift; /* log2(POOLBITS) */
>>> int poolwords;
>>> int tap1, tap2, tap3, tap4, tap5;
> Poolshift is duplicated information; it's just log2(poolwords) + 5
> (since POOLBITS is poolwords*32).
> Granted you don't want to recalculate it every single time you need to
> use it, but perhaps it would be better to add poolshift to struct
> entropy_store, and set it in init_std_data()?

Or we could compute poolwords (and poolbits, and poolbytes) from it,
since shifts generally are cheap. I don't strongly care, whatever your
preference is.


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