arch/x86/include/asm/archrandom.h

   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 __must_check 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 __must_check 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 __must_check 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 __must_check 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 /*
  77  * These are the generic interfaces; they must not be declared if the
  78  * stubs in <linux/random.h> are to be invoked,
  79  * i.e. CONFIG_ARCH_RANDOM is not defined.
  80  */
  81 #ifdef CONFIG_ARCH_RANDOM
  82
  83 static inline bool __must_check arch_get_random_long(unsigned long *v)
  84 {
  85         return static_cpu_has(X86_FEATURE_RDRAND) ? rdrand_long(v) : false;
  86 }
  87
  88 static inline bool __must_check arch_get_random_int(unsigned int *v)
  89 {
  90         return static_cpu_has(X86_FEATURE_RDRAND) ? rdrand_int(v) : false;
  91 }
  92
  93 static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
  94 {
  95         return static_cpu_has(X86_FEATURE_RDSEED) ? rdseed_long(v) : false;
  96 }
  97
  98 static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
  99 {
 100         return static_cpu_has(X86_FEATURE_RDSEED) ? rdseed_int(v) : false;
 101 }
 102
 103 extern void x86_init_rdrand(struct cpuinfo_x86 *c);
 104
 105 #else  /* !CONFIG_ARCH_RANDOM */
 106
 107 static inline void x86_init_rdrand(struct cpuinfo_x86 *c) { }
 108
 109 #endif  /* !CONFIG_ARCH_RANDOM */
 110
 111 #endif /* ASM_X86_ARCHRANDOM_H */