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The Jitter RNG implementation is updated to comply with upstream version 2.1.2. The change covers the following aspects: * Time variation measurement is conducted over the LFSR operation instead of the XOR folding * Invcation of stuck test during initialization * Removal of the stirring functionality and the Von-Neumann unbiaser as the LFSR using a primitive and irreducible polynomial generates an identical distribution of random bits This implementation was successfully used in FIPS 140-2 validations as well as in German BSI evaluations. This kernel implementation was tested as follows: * The unchanged kernel code file jitterentropy.c is compiled as part of user space application to generate raw unconditioned noise data. That data is processed with the NIST SP800-90B non-IID test tool to verify that the kernel code exhibits an equal amount of noise as the upstream Jitter RNG version 2.1.2. * Using AF_ALG with the libkcapi tool of kcapi-rng the Jitter RNG was output tested with dieharder to verify that the output does not exhibit statistical weaknesses. The following command was used: kcapi-rng -n "jitterentropy_rng" -b 100000000000 | dieharder -a -g 200 * The unchanged kernel code file jitterentropy.c is compiled as part of user space application to test the LFSR implementation. The LFSR is injected a monotonically increasing counter as input and the output is fed into dieharder to verify that the LFSR operation does not exhibit statistical weaknesses. * The patch was tested on the Muen separation kernel which returns a more coarse time stamp to verify that the Jitter RNG does not cause regressions with its initialization test considering that the Jitter RNG depends on a high-resolution timer. Tested-by: Reto Buerki <reet@codelabs.ch> Signed-off-by: Stephan Mueller <smueller@chronox.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.