mirror of
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2025-09-04 20:19:47 +08:00
4f4cfa6c56
There are lots of documents that belong to the admin-guide but are on random places (most under Documentation root dir). Move them to the admin guide. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
106 lines
3.8 KiB
ReStructuredText
106 lines
3.8 KiB
ReStructuredText
==========================================================
|
|
Linux support for random number generator in i8xx chipsets
|
|
==========================================================
|
|
|
|
Introduction
|
|
============
|
|
|
|
The hw_random framework is software that makes use of a
|
|
special hardware feature on your CPU or motherboard,
|
|
a Random Number Generator (RNG). The software has two parts:
|
|
a core providing the /dev/hwrng character device and its
|
|
sysfs support, plus a hardware-specific driver that plugs
|
|
into that core.
|
|
|
|
To make the most effective use of these mechanisms, you
|
|
should download the support software as well. Download the
|
|
latest version of the "rng-tools" package from the
|
|
hw_random driver's official Web site:
|
|
|
|
http://sourceforge.net/projects/gkernel/
|
|
|
|
Those tools use /dev/hwrng to fill the kernel entropy pool,
|
|
which is used internally and exported by the /dev/urandom and
|
|
/dev/random special files.
|
|
|
|
Theory of operation
|
|
===================
|
|
|
|
CHARACTER DEVICE. Using the standard open()
|
|
and read() system calls, you can read random data from
|
|
the hardware RNG device. This data is NOT CHECKED by any
|
|
fitness tests, and could potentially be bogus (if the
|
|
hardware is faulty or has been tampered with). Data is only
|
|
output if the hardware "has-data" flag is set, but nevertheless
|
|
a security-conscious person would run fitness tests on the
|
|
data before assuming it is truly random.
|
|
|
|
The rng-tools package uses such tests in "rngd", and lets you
|
|
run them by hand with a "rngtest" utility.
|
|
|
|
/dev/hwrng 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/hwrng. 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.
|
|
|
|
Intel RNG Driver notes
|
|
======================
|
|
|
|
FIXME: support poll(2)
|
|
|
|
.. note::
|
|
|
|
request_mem_region was removed, for three reasons:
|
|
|
|
1) Only one RNG is supported by this driver;
|
|
2) The location used by the RNG is a fixed location in
|
|
MMIO-addressable memory;
|
|
3) users with properly working BIOS e820 handling will always
|
|
have the region in which the RNG is located reserved, so
|
|
request_mem_region calls always fail for proper setups.
|
|
However, for people who use mem=XX, BIOS e820 information is
|
|
**not** in /proc/iomem, and request_mem_region(RNG_ADDR) can
|
|
succeed.
|
|
|
|
Driver details
|
|
==============
|
|
|
|
Based on:
|
|
Intel 82802AB/82802AC Firmware Hub (FWH) Datasheet
|
|
May 1999 Order Number: 290658-002 R
|
|
|
|
Intel 82802 Firmware Hub:
|
|
Random Number Generator
|
|
Programmer's Reference Manual
|
|
December 1999 Order Number: 298029-001 R
|
|
|
|
Intel 82802 Firmware HUB Random Number Generator Driver
|
|
Copyright (c) 2000 Matt Sottek <msottek@quiknet.com>
|
|
|
|
Special thanks to Matt Sottek. I did the "guts", he
|
|
did the "brains" and all the testing.
|