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author | Linus Torvalds <torvalds@linux-foundation.org> | 2019-07-16 12:21:41 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-07-16 12:21:41 -0700 |
commit | c309b6f24222246c18a8b65d3950e6e755440865 (patch) | |
tree | 11893170f5c246bb0dee8066e85878af04162ab0 /Documentation/admin-guide/hw_random.rst | |
parent | 3e859477a1db52a0435d06a55fdb54f62d69c292 (diff) | |
parent | 168869492e7009b6861b615f1d030c99bc805e83 (diff) |
Merge tag 'docs/v5.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media
Pull rst conversion of docs from Mauro Carvalho Chehab:
"As agreed with Jon, I'm sending this big series directly to you, c/c
him, as this series required a special care, in order to avoid
conflicts with other trees"
* tag 'docs/v5.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: (77 commits)
docs: kbuild: fix build with pdf and fix some minor issues
docs: block: fix pdf output
docs: arm: fix a breakage with pdf output
docs: don't use nested tables
docs: gpio: add sysfs interface to the admin-guide
docs: locking: add it to the main index
docs: add some directories to the main documentation index
docs: add SPDX tags to new index files
docs: add a memory-devices subdir to driver-api
docs: phy: place documentation under driver-api
docs: serial: move it to the driver-api
docs: driver-api: add remaining converted dirs to it
docs: driver-api: add xilinx driver API documentation
docs: driver-api: add a series of orphaned documents
docs: admin-guide: add a series of orphaned documents
docs: cgroup-v1: add it to the admin-guide book
docs: aoe: add it to the driver-api book
docs: add some documentation dirs to the driver-api book
docs: driver-model: move it to the driver-api book
docs: lp855x-driver.rst: add it to the driver-api book
...
Diffstat (limited to 'Documentation/admin-guide/hw_random.rst')
-rw-r--r-- | Documentation/admin-guide/hw_random.rst | 105 |
1 files changed, 105 insertions, 0 deletions
diff --git a/Documentation/admin-guide/hw_random.rst b/Documentation/admin-guide/hw_random.rst new file mode 100644 index 000000000000..121de96e395e --- /dev/null +++ b/Documentation/admin-guide/hw_random.rst @@ -0,0 +1,105 @@ +========================================================== +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. |