| Andrew Scull | b4b6d4a | 2019-01-02 15:54:55 +0000 | [diff] [blame] | 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); |
| 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 |
| 43 | void 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 |