arch/x86/include/asm/archrandom.h

   1 /*
   2  * This file is part of the Linux kernel.
   3  *
   4  * Copyright (c) 2011, 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 #ifdef CONFIG_X86_64
  35 # define RDRAND_LONG    ".byte 0x48,0x0f,0xc7,0xf0"
  36 #else
  37 # define RDRAND_LONG    RDRAND_INT
  38 #endif
  39
  40 #ifdef CONFIG_ARCH_RANDOM
  41
  42 /* Instead of arch_get_random_long() when alternatives haven't run. */
  43 static inline int rdrand_long(unsigned long *v)
  44 {
  45         int ok;
  46         asm volatile("1: " RDRAND_LONG "\n\t"
  47                      "jc 2f\n\t"
  48                      "decl %0\n\t"
  49                      "jnz 1b\n\t"
  50                      "2:"
  51                      : "=r" (ok), "=a" (*v)
  52                      : "0" (RDRAND_RETRY_LOOPS));
  53         return ok;
  54 }
  55
  56 #define GET_RANDOM(name, type, rdrand, nop)                     \
  57 static inline int name(type *v)                                 \
  58 {                                                               \
  59         int ok;                                                 \
  60         alternative_io("movl $0, %0\n\t"                        \
  61                        nop,                                     \
  62                        "\n1: " rdrand "\n\t"                    \
  63                        "jc 2f\n\t"                              \
  64                        "decl %0\n\t"                            \
  65                        "jnz 1b\n\t"                             \
  66                        "2:",                                    \
  67                        X86_FEATURE_RDRAND,                      \
  68                        ASM_OUTPUT2("=r" (ok), "=a" (*v)),       \
  69                        "0" (RDRAND_RETRY_LOOPS));               \
  70         return ok;                                              \
  71 }
  72
  73 #ifdef CONFIG_X86_64
  74
  75 GET_RANDOM(arch_get_random_long, unsigned long, RDRAND_LONG, ASM_NOP5);
  76 GET_RANDOM(arch_get_random_int, unsigned int, RDRAND_INT, ASM_NOP4);
  77
  78 #else
  79
  80 GET_RANDOM(arch_get_random_long, unsigned long, RDRAND_LONG, ASM_NOP3);
  81 GET_RANDOM(arch_get_random_int, unsigned int, RDRAND_INT, ASM_NOP3);
  82
  83 #endif /* CONFIG_X86_64 */
  84
  85 #else
  86
  87 static inline int rdrand_long(unsigned long *v)
  88 {
  89         return 0;
  90 }
  91
  92 #endif  /* CONFIG_ARCH_RANDOM */
  93
  94 extern void x86_init_rdrand(struct cpuinfo_x86 *c);
  95
  96 #endif /* ASM_X86_ARCHRANDOM_H */