linux-kernel - Re: drivers/char/random.c: variable type mismatch

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Date:	Wed, 14 Nov 2012 18:58:30 +0100
From:	Stephan Mueller <stephan.mueller@...ec.com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Theodore Ts'o <tytso@....edu>, lkml <linux-kernel@...r.kernel.org>
Subject: Re: drivers/char/random.c: variable type mismatch

On 14.11.2012 18:52:53, +0100, H. Peter Anvin <hpa@...or.com> wrote:

Hi Peter,

> On 11/14/2012 08:15 AM, Stephan Mueller wrote:
>>
>> I agree with the argument of correlation.
>>
>> So, if the reduction of values with a known lack of entropy is of
>> interest, why not change the jiffies variable type too? There we know
>> that only the lower 32 bits are really relevant. Therefore, wouldn't be
>> a structure of
>>
>>          struct {
>>                  unsigned jiffies;
>>                  unsigned cycles;
>>                  unsigned num;
>>          } sample;
>>
>> be more appropriate?
>>
> 
> Probably.  It doesn't make much difference, however.

Well, I guess it does. Because for every byte of the struct, the
input_pool is shuffled. Currently, it is shuffled with bytes known to
have no entropy. With the change, the number of bytes mixed into the
pool without entropy is reduced.
> 
>     -hpa
> 

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