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x86, random: Verify RDRAND functionality and allow it to be disabled

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If the CPU declares that RDRAND is available, go through a guranteed
reseed sequence, and make sure that it is actually working (producing
data.)   If it does not, disable the CPU feature flag.

Allow RDRAND to be disabled on the command line (as opposed to at
compile time) for a user who has special requirements with regards to
random numbers.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
H. Peter Anvin
2011-07-31 14:02:19 -07:00
parent 628c6246d4
commit 49d859d78c
5 changed files with 83 additions and 0 deletions
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2
arch/x86/kernel/cpu/common.c
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@ -15,6 +15,7 @@
#include <asm/stackprotector.h>
#include <asm/perf_event.h>
#include <asm/mmu_context.h>
#include <asm/archrandom.h>
#include <asm/hypervisor.h>
#include <asm/processor.h>
#include <asm/sections.h>
@ -857,6 +858,7 @@ static void __cpuinit identify_cpu(struct cpuinfo_x86 *c)
#endif
init_hypervisor(c);
x86_init_rdrand(c);
/*
* Clear/Set all flags overriden by options, need do it