MdePkg/Library/BaseRngLib/Rand/RdRand.c

   1 /** @file
   2   Random number generator services that uses RdRand instruction access
   3   to provide high-quality random numbers.
   4
   5 Copyright (c) 2021, NUVIA Inc. All rights reserved.<BR>
   6 Copyright (c) 2015, Intel Corporation. All rights reserved.<BR>
   7
   8 SPDX-License-Identifier: BSD-2-Clause-Patent
   9
  10 **/
  11
  12 #include <Uefi.h>
  13 #include <Library/BaseLib.h>
  14 #include <Library/DebugLib.h>
  15
  16 #include "BaseRngLibInternals.h"
  17
  18 //
  19 // Bit mask used to determine if RdRand instruction is supported.
  20 //
  21 #define RDRAND_MASK  BIT30
  22
  23 STATIC BOOLEAN  mRdRandSupported;
  24
  25 /**
  26   The constructor function checks whether or not RDRAND instruction is supported
  27   by the host hardware.
  28
  29   The constructor function checks whether or not RDRAND instruction is supported.
  30   It will ASSERT() if RDRAND instruction is not supported.
  31   It will always return EFI_SUCCESS.
  32
  33   @retval EFI_SUCCESS   The constructor always returns EFI_SUCCESS.
  34
  35 **/
  36 EFI_STATUS
  37 EFIAPI
  38 BaseRngLibConstructor (
  39   VOID
  40   )
  41 {
  42   UINT32  RegEcx;
  43
  44   //
  45   // Determine RDRAND support by examining bit 30 of the ECX register returned by
  46   // CPUID. A value of 1 indicates that processor support RDRAND instruction.
  47   //
  48   AsmCpuid (1, 0, 0, &RegEcx, 0);
  49   ASSERT ((RegEcx & RDRAND_MASK) == RDRAND_MASK);
  50
  51   mRdRandSupported = ((RegEcx & RDRAND_MASK) == RDRAND_MASK);
  52
  53   return EFI_SUCCESS;
  54 }
  55
  56 /**
  57   Generates a 16-bit random number.
  58
  59   @param[out] Rand     Buffer pointer to store the 16-bit random value.
  60
  61   @retval TRUE         Random number generated successfully.
  62   @retval FALSE        Failed to generate the random number.
  63
  64 **/
  65 BOOLEAN
  66 EFIAPI
  67 ArchGetRandomNumber16 (
  68   OUT     UINT16  *Rand
  69   )
  70 {
  71   return AsmRdRand16 (Rand);
  72 }
  73
  74 /**
  75   Generates a 32-bit random number.
  76
  77   @param[out] Rand     Buffer pointer to store the 32-bit random value.
  78
  79   @retval TRUE         Random number generated successfully.
  80   @retval FALSE        Failed to generate the random number.
  81
  82 **/
  83 BOOLEAN
  84 EFIAPI
  85 ArchGetRandomNumber32 (
  86   OUT     UINT32  *Rand
  87   )
  88 {
  89   return AsmRdRand32 (Rand);
  90 }
  91
  92 /**
  93   Generates a 64-bit random number.
  94
  95   @param[out] Rand     Buffer pointer to store the 64-bit random value.
  96
  97   @retval TRUE         Random number generated successfully.
  98   @retval FALSE        Failed to generate the random number.
  99
 100 **/
 101 BOOLEAN
 102 EFIAPI
 103 ArchGetRandomNumber64 (
 104   OUT     UINT64  *Rand
 105   )
 106 {
 107   return AsmRdRand64 (Rand);
 108 }
 109
 110 /**
 111   Checks whether RDRAND is supported.
 112
 113   @retval TRUE         RDRAND is supported.
 114   @retval FALSE        RDRAND is not supported.
 115
 116 **/
 117 BOOLEAN
 118 EFIAPI
 119 ArchIsRngSupported (
 120   VOID
 121   )
 122 {
 123   /*
 124      Existing software depends on this always returning TRUE, so for
 125      now hard-code it.
 126
 127      return mRdRandSupported;
 128   */
 129   return TRUE;
 130 }