1 /* SPDX-License-Identifier: GPL-2.0-only */ 2 /* 3 * This file is part of the Linux kernel. 4 * 5 * Copyright (c) 2011-2014, Intel Corporation 6 * Authors: Fenghua Yu <fenghua.yu@intel.com>, 7 * H. Peter Anvin <hpa@linux.intel.com> 8 */ 9 10 #ifndef ASM_X86_ARCHRANDOM_H 11 #define ASM_X86_ARCHRANDOM_H 12 13 #include <asm/processor.h> 14 #include <asm/cpufeature.h> 15 16 #define RDRAND_RETRY_LOOPS 10 17 18 #define RDRAND_INT ".byte 0x0f,0xc7,0xf0" 19 #define RDSEED_INT ".byte 0x0f,0xc7,0xf8" 20 #ifdef CONFIG_X86_64 21 # define RDRAND_LONG ".byte 0x48,0x0f,0xc7,0xf0" 22 # define RDSEED_LONG ".byte 0x48,0x0f,0xc7,0xf8" 23 #else 24 # define RDRAND_LONG RDRAND_INT 25 # define RDSEED_LONG RDSEED_INT 26 #endif 27 28 /* Unconditional execution of RDRAND and RDSEED */ 29 30 static inline bool rdrand_long(unsigned long *v) 31 { 32 bool ok; 33 unsigned int retry = RDRAND_RETRY_LOOPS; 34 do { 35 asm volatile(RDRAND_LONG 36 CC_SET(c) 37 : CC_OUT(c) (ok), "=a" (*v)); 38 if (ok) 39 return true; 40 } while (--retry); 41 return false; 42 } 43 44 static inline bool rdrand_int(unsigned int *v) 45 { 46 bool ok; 47 unsigned int retry = RDRAND_RETRY_LOOPS; 48 do { 49 asm volatile(RDRAND_INT 50 CC_SET(c) 51 : CC_OUT(c) (ok), "=a" (*v)); 52 if (ok) 53 return true; 54 } while (--retry); 55 return false; 56 } 57 58 static inline bool rdseed_long(unsigned long *v) 59 { 60 bool ok; 61 asm volatile(RDSEED_LONG 62 CC_SET(c) 63 : CC_OUT(c) (ok), "=a" (*v)); 64 return ok; 65 } 66 67 static inline bool rdseed_int(unsigned int *v) 68 { 69 bool ok; 70 asm volatile(RDSEED_INT 71 CC_SET(c) 72 : CC_OUT(c) (ok), "=a" (*v)); 73 return ok; 74 } 75 76 /* Conditional execution based on CPU type */ 77 #define arch_has_random() static_cpu_has(X86_FEATURE_RDRAND) 78 #define arch_has_random_seed() static_cpu_has(X86_FEATURE_RDSEED) 79 80 /* 81 * These are the generic interfaces; they must not be declared if the 82 * stubs in <linux/random.h> are to be invoked, 83 * i.e. CONFIG_ARCH_RANDOM is not defined. 84 */ 85 #ifdef CONFIG_ARCH_RANDOM 86 87 static inline bool arch_get_random_long(unsigned long *v) 88 { 89 return arch_has_random() ? rdrand_long(v) : false; 90 } 91 92 static inline bool arch_get_random_int(unsigned int *v) 93 { 94 return arch_has_random() ? rdrand_int(v) : false; 95 } 96 97 static inline bool arch_get_random_seed_long(unsigned long *v) 98 { 99 return arch_has_random_seed() ? rdseed_long(v) : false; 100 } 101 102 static inline bool arch_get_random_seed_int(unsigned int *v) 103 { 104 return arch_has_random_seed() ? rdseed_int(v) : false; 105 } 106 107 extern void x86_init_rdrand(struct cpuinfo_x86 *c); 108 109 #else /* !CONFIG_ARCH_RANDOM */ 110 111 static inline void x86_init_rdrand(struct cpuinfo_x86 *c) { } 112 113 #endif /* !CONFIG_ARCH_RANDOM */ 114 115 #endif /* ASM_X86_ARCHRANDOM_H */ 116