/* * 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