1// SPDX-License-Identifier: GPL-2.0-only
 2/*
 3 * This file is part of the Linux kernel.
 4 *
 5 * Copyright (c) 2011, Intel Corporation
 6 * Authors: Fenghua Yu <fenghua.yu@intel.com>,
 7 *          H. Peter Anvin <hpa@linux.intel.com>
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 8 */
 9
10#include <asm/processor.h>
11#include <asm/archrandom.h>
12#include <asm/sections.h>
13
14static int __init x86_rdrand_setup(char *s)
15{
16	setup_clear_cpu_cap(X86_FEATURE_RDRAND);
17	setup_clear_cpu_cap(X86_FEATURE_RDSEED);
18	return 1;
19}
20__setup("nordrand", x86_rdrand_setup);
21
22/*
23 * RDRAND has Built-In-Self-Test (BIST) that runs on every invocation.
24 * Run the instruction a few times as a sanity check.
25 * If it fails, it is simple to disable RDRAND here.
26 */
27#define SANITY_CHECK_LOOPS 8
28
29#ifdef CONFIG_ARCH_RANDOM
30void x86_init_rdrand(struct cpuinfo_x86 *c)
31{
32	unsigned long tmp;
33	int i;
34
35	if (!cpu_has(c, X86_FEATURE_RDRAND))
36		return;
37
38	for (i = 0; i < SANITY_CHECK_LOOPS; i++) {
39		if (!rdrand_long(&tmp)) {
40			clear_cpu_cap(c, X86_FEATURE_RDRAND);
41			pr_warn_once("rdrand: disabled\n");
42			return;
43		}
44	}
45}
46#endif

 
 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
27static int __init x86_rdrand_setup(char *s)
28{
29	setup_clear_cpu_cap(X86_FEATURE_RDRAND);
30	setup_clear_cpu_cap(X86_FEATURE_RDSEED);
31	return 1;
32}
33__setup("nordrand", x86_rdrand_setup);
34
35/*
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.
39 */
40#define SANITY_CHECK_LOOPS 8
41
42#ifdef CONFIG_ARCH_RANDOM
43void x86_init_rdrand(struct cpuinfo_x86 *c)
44{
45	unsigned long tmp;
46	int i;
47
48	if (!cpu_has(c, X86_FEATURE_RDRAND))
49		return;
50
51	for (i = 0; i < SANITY_CHECK_LOOPS; i++) {
52		if (!rdrand_long(&tmp)) {
53			clear_cpu_cap(c, X86_FEATURE_RDRAND);
54			pr_warn_once("rdrand: disabled\n");
55			return;
56		}
57	}
58}
59#endif