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

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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>
This commit is contained in:
H. Peter Anvin 2014-05-11 20:25:20 -07:00
parent d6d211db37
commit 7a5091d584
2 changed files with 5 additions and 4 deletions
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8
Documentation/kernel-parameters.txt
View file

@ -2218,10 +2218,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
noreplace-smp [X86-32,SMP] Don't replace SMP instructions noreplace-smp [X86-32,SMP] Don't replace SMP instructions
with UP alternatives with UP alternatives
nordrand [X86] Disable the direct use of the RDRAND nordrand [X86] Disable kernel use of the RDRAND and
instruction even if it is supported by the RDSEED instructions even if they are supported
processor. RDRAND is still available to user by the processor. RDRAND and RDSEED are still
space applications. available to user space applications.
noresume [SWSUSP] Disables resume and restores original swap noresume [SWSUSP] Disables resume and restores original swap
space. space.

1
arch/x86/kernel/cpu/rdrand.c
View file

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