arch/x86/include/asm/archrandom.h

   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
  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
  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
  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
  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 */