60 lines
1.6 KiB
C
60 lines
1.6 KiB
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
|
||
|
|
|
||
|
|
#ifdef CONFIG_ARCH_RANDOM
|
||
|
|
void x86_init_rdrand(struct cpuinfo_x86 *c)
|
||
|
|
{
|
||
|
|
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);
|
||
|
|
pr_warn_once("rdrand: disabled\n");
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
#endif
|