The input layer is now sending us a bunch of events in a row for each actual
event.  This shows up weaknesses in the periodicity detector and using the
high clock rate from get_clock: each keystroke is getting accounted as 10
different maximal-entropy events.

A brief touch on a trackpad will generate as much as 2000 maximal entropy
events which is more than 2k of /dev/random output.  IOW, we're WAY
overestimating input entropy.  Here's one keystroke:

random 0024 0000 0000: mouse event
random 0035 0000 0000: added 11 entropy credits to input
random 0035 0000 0000: mouse event
random 0046 0000 0000: added 11 entropy credits to input
random 0046 0000 0000: mouse event
random 0056 0000 0000: added 10 entropy credits to input
random 0056 0000 0000: keyboard event
random 0067 0000 0000: added 11 entropy credits to input
random 0067 0000 0000: mouse event
random 0078 0000 0000: added 11 entropy credits to input
random 0078 0000 0000: awake
random 0078 0000 0000: reading 128 bits
random 0078 0000 0000: going to reseed blocking with 128 bits (128 of 0 requested)
random 0078 0000 0000: trying to extract 128 bits from input
random 0006 0000 0000: debiting 72 entropy credits from input
random 0006 0072 0000: added 72 entropy credits to blocking
random 0006 0072 0000: trying to extract 128 bits from blocking
random 0006 0000 0000: debiting 72 entropy credits from blocking
random 0006 0000 0000: read got 72 bits (56 still needed)
random 0006 0000 0000: reading 56 bits
random 0006 0000 0000: going to reseed blocking with 64 bits (56 of 0 requested
random 0006 0000 0000: trying to extract 64 bits from input
random 0006 0000 0000: debiting 0 entropy credits from input
random 0006 0000 0000: trying to extract 56 bits from blocking
random 0006 0000 0000: debiting 0 entropy credits from blocking
random 0006 0000 0000: read got 0 bits (56 still needed)
random 0006 0000 0000: sleeping
random 0006 0000 0000: mouse event
random 0017 0000 0000: added 11 entropy credits to input
random 0017 0000 0000: mouse event
random 0028 0000 0000: added 11 entropy credits to input
random 0028 0000 0000: mouse event
random 0038 0000 0000: added 10 entropy credits to input
random 0038 0000 0000: keyboard event
random 0049 0000 0000: added 11 entropy credits to input
random 0049 0000 0000: mouse event
random 0060 0000 0000: added 11 entropy credits to input

The first step to fixing this is to check periodicity and estimate entropy
against a slow clock like jiffies.  We continue to mix in get_clock() rather
than jiffies where available.

This throws away most of the duplicate events and gives us more sensible
entropy estimates, but we still duplicates from input.c and keyboard.c.
Signed-off-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>