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xianfeng |
Hardware driver for Intel/AMD/VIA Random Number Generators (RNG)
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Copyright 2000,2001 Jeff Garzik
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Copyright 2000,2001 Philipp Rumpf
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Introduction:
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The hw_random device driver is software that makes use of a
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special hardware feature on your CPU or motherboard,
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a Random Number Generator (RNG).
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In order to make effective use of this device driver, you
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should download the support software as well. Download the
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latest version of the "rng-tools" package from the
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hw_random driver's official Web site:
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http://sourceforge.net/projects/gkernel/
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About the Intel RNG hardware, from the firmware hub datasheet:
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The Firmware Hub integrates a Random Number Generator (RNG)
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using thermal noise generated from inherently random quantum
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mechanical properties of silicon. When not generating new random
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bits the RNG circuitry will enter a low power state. Intel will
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provide a binary software driver to give third party software
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access to our RNG for use as a security feature. At this time,
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the RNG is only to be used with a system in an OS-present state.
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Theory of operation:
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Character driver. Using the standard open()
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and read() system calls, you can read random data from
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the hardware RNG device. This data is NOT CHECKED by any
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fitness tests, and could potentially be bogus (if the
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hardware is faulty or has been tampered with). Data is only
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output if the hardware "has-data" flag is set, but nevertheless
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a security-conscious person would run fitness tests on the
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data before assuming it is truly random.
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/dev/hwrandom is char device major 10, minor 183.
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Driver notes:
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* FIXME: support poll(2)
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NOTE: request_mem_region was removed, for two reasons:
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1) Only one RNG is supported by this driver, 2) The location
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used by the RNG is a fixed location in MMIO-addressable memory,
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3) users with properly working BIOS e820 handling will always
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have the region in which the RNG is located reserved, so
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request_mem_region calls always fail for proper setups.
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However, for people who use mem=XX, BIOS e820 information is
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-not- in /proc/iomem, and request_mem_region(RNG_ADDR) can
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succeed.
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Driver details:
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Based on:
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Intel 82802AB/82802AC Firmware Hub (FWH) Datasheet
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May 1999 Order Number: 290658-002 R
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Intel 82802 Firmware Hub: Random Number Generator
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Programmer's Reference Manual
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December 1999 Order Number: 298029-001 R
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Intel 82802 Firmware HUB Random Number Generator Driver
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Copyright (c) 2000 Matt Sottek
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Special thanks to Matt Sottek. I did the "guts", he
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did the "brains" and all the testing.
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