| // SPDX-License-Identifier: GPL-2.0-only |
| /* |
| * 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> |
| */ |
| |
| #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 |
