1 /* 2 * This file is part of the Linux kernel. 3 * 4 * Copyright (c) 2011-2014, 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 #ifndef ASM_X86_ARCHRANDOM_H 24 #define ASM_X86_ARCHRANDOM_H 25 26 #include <asm/processor.h> 27 #include <asm/cpufeature.h> 28 29 #define RDRAND_RETRY_LOOPS 10 30 31 #define RDRAND_INT ".byte 0x0f,0xc7,0xf0" 32 #define RDSEED_INT ".byte 0x0f,0xc7,0xf8" 33 #ifdef CONFIG_X86_64 34 # define RDRAND_LONG ".byte 0x48,0x0f,0xc7,0xf0" 35 # define RDSEED_LONG ".byte 0x48,0x0f,0xc7,0xf8" 36 #else 37 # define RDRAND_LONG RDRAND_INT 38 # define RDSEED_LONG RDSEED_INT 39 #endif 40 41 /* Unconditional execution of RDRAND and RDSEED */ 42 43 static inline bool rdrand_long(unsigned long *v) 44 { 45 bool ok; 46 unsigned int retry = RDRAND_RETRY_LOOPS; 47 do { 48 asm volatile(RDRAND_LONG "\n\t" 49 CC_SET(c) 50 : CC_OUT(c) (ok), "=a" (*v)); 51 if (ok) 52 return true; 53 } while (--retry); 54 return false; 55 } 56 57 static inline bool rdrand_int(unsigned int *v) 58 { 59 bool ok; 60 unsigned int retry = RDRAND_RETRY_LOOPS; 61 do { 62 asm volatile(RDRAND_INT "\n\t" 63 CC_SET(c) 64 : CC_OUT(c) (ok), "=a" (*v)); 65 if (ok) 66 return true; 67 } while (--retry); 68 return false; 69 } 70 71 static inline bool rdseed_long(unsigned long *v) 72 { 73 bool ok; 74 asm volatile(RDSEED_LONG "\n\t" 75 CC_SET(c) 76 : CC_OUT(c) (ok), "=a" (*v)); 77 return ok; 78 } 79 80 static inline bool rdseed_int(unsigned int *v) 81 { 82 bool ok; 83 asm volatile(RDSEED_INT "\n\t" 84 CC_SET(c) 85 : CC_OUT(c) (ok), "=a" (*v)); 86 return ok; 87 } 88 89 /* Conditional execution based on CPU type */ 90 #define arch_has_random() static_cpu_has(X86_FEATURE_RDRAND) 91 #define arch_has_random_seed() static_cpu_has(X86_FEATURE_RDSEED) 92 93 /* 94 * These are the generic interfaces; they must not be declared if the 95 * stubs in <linux/random.h> are to be invoked, 96 * i.e. CONFIG_ARCH_RANDOM is not defined. 97 */ 98 #ifdef CONFIG_ARCH_RANDOM 99 100 static inline bool arch_get_random_long(unsigned long *v) 101 { 102 return arch_has_random() ? rdrand_long(v) : false; 103 } 104 105 static inline bool arch_get_random_int(unsigned int *v) 106 { 107 return arch_has_random() ? rdrand_int(v) : false; 108 } 109 110 static inline bool arch_get_random_seed_long(unsigned long *v) 111 { 112 return arch_has_random_seed() ? rdseed_long(v) : false; 113 } 114 115 static inline bool arch_get_random_seed_int(unsigned int *v) 116 { 117 return arch_has_random_seed() ? rdseed_int(v) : false; 118 } 119 120 extern void x86_init_rdrand(struct cpuinfo_x86 *c); 121 122 #else /* !CONFIG_ARCH_RANDOM */ 123 124 static inline void x86_init_rdrand(struct cpuinfo_x86 *c) { } 125 126 #endif /* !CONFIG_ARCH_RANDOM */ 127 128 #endif /* ASM_X86_ARCHRANDOM_H */ 129