74 строки
2.0 KiB
C
74 строки
2.0 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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return 1;
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}
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__setup("nordrand", x86_rdrand_setup);
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/* We can't use arch_get_random_long() here since alternatives haven't run */
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static inline int rdrand_long(unsigned long *v)
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{
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int ok;
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asm volatile("1: " RDRAND_LONG "\n\t"
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"jc 2f\n\t"
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"decl %0\n\t"
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"jnz 1b\n\t"
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"2:"
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: "=r" (ok), "=a" (*v)
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: "0" (RDRAND_RETRY_LOOPS));
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return ok;
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}
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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 __cpuinit 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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