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 #include <asm/alternative.h> 29 #include <asm/nops.h> 30 31 #define RDRAND_RETRY_LOOPS 10 32 33 #define RDRAND_INT ".byte 0x0f,0xc7,0xf0" 34 #define RDSEED_INT ".byte 0x0f,0xc7,0xf8" 35 #ifdef CONFIG_X86_64 36 # define RDRAND_LONG ".byte 0x48,0x0f,0xc7,0xf0" 37 # define RDSEED_LONG ".byte 0x48,0x0f,0xc7,0xf8" 38 #else 39 # define RDRAND_LONG RDRAND_INT 40 # define RDSEED_LONG RDSEED_INT 41 #endif 42 43 #ifdef CONFIG_ARCH_RANDOM 44 45 /* Instead of arch_get_random_long() when alternatives haven't run. */ 46 static inline int rdrand_long(unsigned long *v) 47 { 48 int ok; 49 asm volatile("1: " RDRAND_LONG "\n\t" 50 "jc 2f\n\t" 51 "decl %0\n\t" 52 "jnz 1b\n\t" 53 "2:" 54 : "=r" (ok), "=a" (*v) 55 : "0" (RDRAND_RETRY_LOOPS)); 56 return ok; 57 } 58 59 /* A single attempt at RDSEED */ 60 static inline bool rdseed_long(unsigned long *v) 61 { 62 unsigned char ok; 63 asm volatile(RDSEED_LONG "\n\t" 64 "setc %0" 65 : "=qm" (ok), "=a" (*v)); 66 return ok; 67 } 68 69 #define GET_RANDOM(name, type, rdrand, nop) \ 70 static inline int name(type *v) \ 71 { \ 72 int ok; \ 73 alternative_io("movl $0, %0\n\t" \ 74 nop, \ 75 "\n1: " rdrand "\n\t" \ 76 "jc 2f\n\t" \ 77 "decl %0\n\t" \ 78 "jnz 1b\n\t" \ 79 "2:", \ 80 X86_FEATURE_RDRAND, \ 81 ASM_OUTPUT2("=r" (ok), "=a" (*v)), \ 82 "0" (RDRAND_RETRY_LOOPS)); \ 83 return ok; \ 84 } 85 86 #define GET_SEED(name, type, rdseed, nop) \ 87 static inline int name(type *v) \ 88 { \ 89 unsigned char ok; \ 90 alternative_io("movb $0, %0\n\t" \ 91 nop, \ 92 rdseed "\n\t" \ 93 "setc %0", \ 94 X86_FEATURE_RDSEED, \ 95 ASM_OUTPUT2("=q" (ok), "=a" (*v))); \ 96 return ok; \ 97 } 98 99 #ifdef CONFIG_X86_64 100 101 GET_RANDOM(arch_get_random_long, unsigned long, RDRAND_LONG, ASM_NOP5); 102 GET_RANDOM(arch_get_random_int, unsigned int, RDRAND_INT, ASM_NOP4); 103 104 GET_SEED(arch_get_random_seed_long, unsigned long, RDSEED_LONG, ASM_NOP5); 105 GET_SEED(arch_get_random_seed_int, unsigned int, RDSEED_INT, ASM_NOP4); 106 107 #else 108 109 GET_RANDOM(arch_get_random_long, unsigned long, RDRAND_LONG, ASM_NOP3); 110 GET_RANDOM(arch_get_random_int, unsigned int, RDRAND_INT, ASM_NOP3); 111 112 GET_SEED(arch_get_random_seed_long, unsigned long, RDSEED_LONG, ASM_NOP4); 113 GET_SEED(arch_get_random_seed_int, unsigned int, RDSEED_INT, ASM_NOP4); 114 115 #endif /* CONFIG_X86_64 */ 116 117 #define arch_has_random() static_cpu_has(X86_FEATURE_RDRAND) 118 #define arch_has_random_seed() static_cpu_has(X86_FEATURE_RDSEED) 119 120 #else 121 122 static inline int rdrand_long(unsigned long *v) 123 { 124 return 0; 125 } 126 127 static inline bool rdseed_long(unsigned long *v) 128 { 129 return 0; 130 } 131 132 #endif /* CONFIG_ARCH_RANDOM */ 133 134 extern void x86_init_rdrand(struct cpuinfo_x86 *c); 135 136 #endif /* ASM_X86_ARCHRANDOM_H */ 137