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Commit 7a5091d5 authored May 11, 2014 by H. Peter Anvin

x86, rdrand: When nordrand is specified, disable RDSEED as well



One can logically expect that when the user has specified "nordrand",
the user doesn't want any use of the CPU random number generator,
neither RDRAND nor RDSEED, so disable both.

Reported-by: Stephan Mueller <smueller@chronox.de>
Cc: Theodore Ts'o <tytso@mit.edu>
Link: http://lkml.kernel.org/r/21542339.0lFnPSyGRS@myon.chronox.de


Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

parent d6d211db

Documentation/kernel-parameters.txt

+4 −4

Original line number	Diff line number	Diff line
		@@ -2218,10 +2218,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
		noreplace-smp [X86-32,SMP] Don't replace SMP instructions
		with UP alternatives

		nordrand [X86] Disable the direct use of the RDRAND
		instruction even if it is supported by the
		processor. RDRAND is still available to user
		space applications.
		nordrand [X86] Disable kernel use of the RDRAND and
		RDSEED instructions even if they are supported
		by the processor. RDRAND and RDSEED are still
		available to user space applications.

		noresume [SWSUSP] Disables resume and restores original swap
		space.

arch/x86/kernel/cpu/rdrand.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -27,6 +27,7 @@
		static int __init x86_rdrand_setup(char *s)
		{
		setup_clear_cpu_cap(X86_FEATURE_RDRAND);
		setup_clear_cpu_cap(X86_FEATURE_RDSEED);
		return 1;
		}
		__setup("nordrand", x86_rdrand_setup);