From: Theodore Ts'o Date: Sun, 15 Jun 2014 20:59:24 +0000 (-0400) Subject: random: use registers from interrupted code for CPU's w/o a cycle counter X-Git-Tag: omap-for-v3.17/fixes-against-rc2~106^2~3 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ee3e00e9e7101c80a2ff2d5672d4b486bf001b88;p=pandora-kernel.git random: use registers from interrupted code for CPU's w/o a cycle counter For CPU's that don't have a cycle counter, or something equivalent which can be used for random_get_entropy(), random_get_entropy() will always return 0. In that case, substitute with the saved interrupt registers to add a bit more unpredictability. Some folks have suggested hashing all of the registers unconditionally, but this would increase the overhead of add_interrupt_randomness() by at least an order of magnitude, and this would very likely be unacceptable. The changes in this commit have been benchmarked as mostly unaffecting the overhead of add_interrupt_randomness() if the entropy counter is present, and doubling the overhead if it is not present. Signed-off-by: Theodore Ts'o Cc: Jörn Engel --- Reading git-diff-tree failed