[mirror_ubuntu-artful-kernel.git] / arch / x86 / kernel / cpu / rdrand.c

/*
 * This file is part of the Linux kernel.
 *
 * Copyright (c) 2011, Intel Corporation
 * Authors: Fenghua Yu <fenghua.yu@intel.com>,
 *          H. Peter Anvin <hpa@linux.intel.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
 *
 */

#include <asm/processor.h>
#include <asm/archrandom.h>
#include <asm/sections.h>

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);

/*
 * RDRAND has Built-In-Self-Test (BIST) that runs on every invocation.
 * Run the instruction a few times as a sanity check.
 * If it fails, it is simple to disable RDRAND here.
 */
#define SANITY_CHECK_LOOPS 8

void x86_init_rdrand(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_ARCH_RANDOM
	unsigned long tmp;
	int i;

	if (!cpu_has(c, X86_FEATURE_RDRAND))
		return;

	for (i = 0; i < SANITY_CHECK_LOOPS; i++) {
		if (!rdrand_long(&tmp)) {
			clear_cpu_cap(c, X86_FEATURE_RDRAND);
			printk_once(KERN_WARNING "rdrand: disabled\n");
			return;
		}
	}
#endif
}
Commit	Line	Data
49d859d7 PA	1	/*
	2	* This file is part of the Linux kernel.
	3	*
	4	* Copyright (c) 2011, Intel Corporation
	5	* Authors: Fenghua Yu <fenghua.yu@intel.com>,
	6	* H. Peter Anvin <hpa@linux.intel.com>
	7	*
	8	* This program is free software; you can redistribute it and/or modify it
	9	* under the terms and conditions of the GNU General Public License,
	10	* version 2, as published by the Free Software Foundation.
	11	*
	12	* This program is distributed in the hope it will be useful, but WITHOUT
	13	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	14	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
	15	* more details.
	16	*
	17	* You should have received a copy of the GNU General Public License along with
	18	* this program; if not, write to the Free Software Foundation, Inc.,
	19	* 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
	20	*
	21	*/
	22
	23	#include <asm/processor.h>
	24	#include <asm/archrandom.h>
	25	#include <asm/sections.h>
	26
	27	static int __init x86_rdrand_setup(char *s)
	28	{
	29	setup_clear_cpu_cap(X86_FEATURE_RDRAND);
7a5091d5	30	setup_clear_cpu_cap(X86_FEATURE_RDSEED);
49d859d7 PA	31	return 1;
	32	}
	33	__setup("nordrand", x86_rdrand_setup);
	34
49d859d7	35	/*
0007bccc LB	36	* RDRAND has Built-In-Self-Test (BIST) that runs on every invocation.
	37	* Run the instruction a few times as a sanity check.
	38	* If it fails, it is simple to disable RDRAND here.
49d859d7	39	*/
0007bccc	40	#define SANITY_CHECK_LOOPS 8
49d859d7	41
148f9bb8	42	void x86_init_rdrand(struct cpuinfo_x86 *c)
49d859d7 PA	43	{
	44	#ifdef CONFIG_ARCH_RANDOM
	45	unsigned long tmp;
0007bccc	46	int i;
49d859d7 PA	47
49d859d7 PA	48	if (!cpu_has(c, X86_FEATURE_RDRAND))
0007bccc	49	return;
49d859d7	50
0007bccc LB	51	for (i = 0; i < SANITY_CHECK_LOOPS; i++) {
	52	if (!rdrand_long(&tmp)) {
	53	clear_cpu_cap(c, X86_FEATURE_RDRAND);
	54	printk_once(KERN_WARNING "rdrand: disabled\n");
	55	return;
	56	}
49d859d7	57	}
49d859d7 PA	58	#endif
49d859d7 PA	59	}