From 7a5091d58419b4e5222abce58a40c072786ea1d6 Mon Sep 17 00:00:00 2001
From: "H. Peter Anvin" <hpa@linux.intel.com>
Date: Sun, 11 May 2014 20:25:20 -0700
Subject: [PATCH] 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>
---
Documentation/kernel-parameters.txt | 8 ++++----
arch/x86/kernel/cpu/rdrand.c | 1 +
2 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 43842177b771..30a8ad0dae53 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -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.
diff --git a/arch/x86/kernel/cpu/rdrand.c b/arch/x86/kernel/cpu/rdrand.c
index 384df5105fbc..136ac74dee82 100644
--- a/arch/x86/kernel/cpu/rdrand.c
+++ b/arch/x86/kernel/cpu/rdrand.c
@@ -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);
--
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