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Commit 537878d2 authored by David Brownell's avatar David Brownell Committed by Linus Torvalds
Browse files

hw_random doc updates 



Update documentation for the hw_random support to be current:

 - Documentation/hw_random.txt has been updated to reflect the
   current code:  it's a framework now, a "core" with a small
   sysfs interface, that hardware-specific drivers plug in to.
   Text specific to Intel hardware is now at the end.

 - Kconfig now references the Documentation/hw_random.txt file
   and better explains what this really does.

Both chunks of documentation now higlight the fact that the kernel entropy
pool is maintained by "rngd", and this driver has nothing directly to do with
that important task.

Signed-off-by: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent cb622bbb

Documentation/hw_random.txt

+40 −19
Original line number Original line Diff line number Diff line 
	Hardware driver for Intel/AMD/VIA Random Number Generators (RNG)

	Copyright 2000,2001 Jeff Garzik <jgarzik@pobox.com>

	Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com>



Introduction:

Introduction:





	The hw_random device driver is software that makes use of a

	The hw_random framework is software that makes use of a

	special hardware feature on your CPU or motherboard,

	special hardware feature on your CPU or motherboard,

	a Random Number Generator (RNG).

	a Random Number Generator (RNG).  The software has two parts:

	a core providing the /dev/hw_random character device and its

	sysfs support, plus a hardware-specific driver that plugs

	into that core.





	In order to make effective use of this device driver, you

	To make the most effective use of these mechanisms, you

	should download the support software as well.  Download the

	should download the support software as well.  Download the

	latest version of the "rng-tools" package from the

	latest version of the "rng-tools" package from the

	hw_random driver's official Web site:

	hw_random driver's official Web site:





		http://sourceforge.net/projects/gkernel/

		http://sourceforge.net/projects/gkernel/





About the Intel RNG hardware, from the firmware hub datasheet:

	Those tools use /dev/hw_random to fill the kernel entropy pool,



	which is used internally and exported by the /dev/urandom and

	The Firmware Hub integrates a Random Number Generator (RNG)

	/dev/random special files.

	using thermal noise generated from inherently random quantum

	mechanical properties of silicon. When not generating new random

	bits the RNG circuitry will enter a low power state. Intel will

	provide a binary software driver to give third party software

	access to our RNG for use as a security feature. At this time,

	the RNG is only to be used with a system in an OS-present state.





Theory of operation:

Theory of operation:





	Character driver.  Using the standard open()

	CHARACTER DEVICE.  Using the standard open()

	and read() system calls, you can read random data from

	and read() system calls, you can read random data from

	the hardware RNG device.  This data is NOT CHECKED by any

	the hardware RNG device.  This data is NOT CHECKED by any

	fitness tests, and could potentially be bogus (if the

	fitness tests, and could potentially be bogus (if the
@@ -36,9 +29,37 @@ Theory of operation: 
	a security-conscious person would run fitness tests on the

	a security-conscious person would run fitness tests on the

	data before assuming it is truly random.

	data before assuming it is truly random.





	/dev/hwrandom is char device major 10, minor 183.

	The rng-tools package uses such tests in "rngd", and lets you

	run them by hand with a "rngtest" utility.



	/dev/hw_random is char device major 10, minor 183.



	CLASS DEVICE.  There is a /sys/class/misc/hw_random node with

	two unique attributes, "rng_available" and "rng_current".  The

	"rng_available" attribute lists the hardware-specific drivers

	available, while "rng_current" lists the one which is currently

	connected to /dev/hw_random.  If your system has more than one

	RNG available, you may change the one used by writing a name from

	the list in "rng_available" into "rng_current".



==========================================================================



	Hardware driver for Intel/AMD/VIA Random Number Generators (RNG)

	Copyright 2000,2001 Jeff Garzik <jgarzik@pobox.com>

	Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com>





About the Intel RNG hardware, from the firmware hub datasheet:



	The Firmware Hub integrates a Random Number Generator (RNG)

	using thermal noise generated from inherently random quantum

	mechanical properties of silicon. When not generating new random

	bits the RNG circuitry will enter a low power state. Intel will

	provide a binary software driver to give third party software

	access to our RNG for use as a security feature. At this time,

	the RNG is only to be used with a system in an OS-present state.





Driver notes:

Intel RNG Driver notes:





	* FIXME: support poll(2)

	* FIXME: support poll(2)

drivers/char/hw_random/Kconfig

+8 −1
Original line number Original line Diff line number Diff line
@@ -9,7 +9,14 @@ config HW_RANDOM 
	  Hardware Random Number Generator Core infrastructure.

	  Hardware Random Number Generator Core infrastructure.





	  To compile this driver as a module, choose M here: the

	  To compile this driver as a module, choose M here: the

	  module will be called rng-core.

	  module will be called rng-core.  This provides a device

	  that's usually called /dev/hw_random, and which exposes one

	  of possibly several hardware random number generators.



	  These hardware random number generators do not feed directly

	  into the kernel's random number generator.  That is usually

	  handled by the "rngd" daemon.  Documentation/hw_random.txt

	  has more information.





	  If unsure, say Y.

	  If unsure, say Y.