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 /* Unconditional execution of RDRAND and RDSEED */ 19 20 static inline bool __must_check rdrand_long(unsigned long *v) 21 { 22 bool ok; 23 unsigned int retry = RDRAND_RETRY_LOOPS; 24 do { 25 asm volatile("rdrand %[out]" 26 CC_SET(c) 27 : CC_OUT(c) (ok), [out] "=r" (*v)); 28 if (ok) 29 return true; 30 } while (--retry); 31 return false; 32 } 33 34 static inline bool __must_check rdseed_long(unsigned long *v) 35 { 36 bool ok; 37 asm volatile("rdseed %[out]" 38 CC_SET(c) 39 : CC_OUT(c) (ok), [out] "=r" (*v)); 40 return ok; 41 } 42 43 /* 44 * These are the generic interfaces; they must not be declared if the 45 * stubs in <linux/random.h> are to be invoked. 46 */ 47 48 static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs) 49 { 50 return max_longs && static_cpu_has(X86_FEATURE_RDRAND) && rdrand_long(v) ? 1 : 0; 51 } 52 53 static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs) 54 { 55 return max_longs && static_cpu_has(X86_FEATURE_RDSEED) && rdseed_long(v) ? 1 : 0; 56 } 57 58 #ifndef CONFIG_UML 59 void x86_init_rdrand(struct cpuinfo_x86 *c); 60 #endif 61 62 #endif /* ASM_X86_ARCHRANDOM_H */ 63