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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>
61 lines
1.7 KiB
C
61 lines
1.7 KiB
C
/*
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* This file is part of the Linux kernel.
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*
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* Copyright (c) 2011, Intel Corporation
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* Authors: Fenghua Yu <fenghua.yu@intel.com>,
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* H. Peter Anvin <hpa@linux.intel.com>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms and conditions of the GNU General Public License,
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* version 2, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
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*
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*/
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#include <asm/processor.h>
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#include <asm/archrandom.h>
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#include <asm/sections.h>
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static int __init x86_rdrand_setup(char *s)
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{
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setup_clear_cpu_cap(X86_FEATURE_RDRAND);
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setup_clear_cpu_cap(X86_FEATURE_RDSEED);
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return 1;
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}
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__setup("nordrand", x86_rdrand_setup);
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/*
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* Force a reseed cycle; we are architecturally guaranteed a reseed
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* after no more than 512 128-bit chunks of random data. This also
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* acts as a test of the CPU capability.
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*/
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#define RESEED_LOOP ((512*128)/sizeof(unsigned long))
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void x86_init_rdrand(struct cpuinfo_x86 *c)
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{
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#ifdef CONFIG_ARCH_RANDOM
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unsigned long tmp;
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int i, count, ok;
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if (!cpu_has(c, X86_FEATURE_RDRAND))
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return; /* Nothing to do */
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for (count = i = 0; i < RESEED_LOOP; i++) {
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ok = rdrand_long(&tmp);
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if (ok)
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count++;
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}
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if (count != RESEED_LOOP)
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clear_cpu_cap(c, X86_FEATURE_RDRAND);
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#endif
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}
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