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 #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 */