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
  24 STATIC BOOLEAN mRdRandSupported;
  25
  26 /**
  27   The constructor function checks whether or not RDRAND instruction is supported
  28   by the host hardware.
  29
  30   The constructor function checks whether or not RDRAND instruction is supported.
  31   It will ASSERT() if RDRAND instruction is not supported.
  32   It will always return EFI_SUCCESS.
  33
  34   @retval EFI_SUCCESS   The constructor always returns EFI_SUCCESS.
  35
  36 **/
  37 EFI_STATUS
  38 EFIAPI
  39 BaseRngLibConstructor (
  40   VOID
  41   )
  42 {
  43   UINT32  RegEcx;
  44
  45   //
  46   // Determine RDRAND support by examining bit 30 of the ECX register returned by
  47   // CPUID. A value of 1 indicates that processor support RDRAND instruction.
  48   //
  49   AsmCpuid (1, 0, 0, &RegEcx, 0);
  50   ASSERT ((RegEcx & RDRAND_MASK) == RDRAND_MASK);
  51
  52   mRdRandSupported = ((RegEcx & RDRAND_MASK) == RDRAND_MASK);
  53
  54   return EFI_SUCCESS;
  55 }
  56
  57 /**
  58   Generates a 16-bit random number.
  59
  60   @param[out] Rand     Buffer pointer to store the 16-bit random value.
  61
  62   @retval TRUE         Random number generated successfully.
  63   @retval FALSE        Failed to generate the random number.
  64
  65 **/
  66 BOOLEAN
  67 EFIAPI
  68 ArchGetRandomNumber16 (
  69   OUT     UINT16                    *Rand
  70   )
  71 {
  72   return AsmRdRand16 (Rand);
  73 }
  74
  75 /**
  76   Generates a 32-bit random number.
  77
  78   @param[out] Rand     Buffer pointer to store the 32-bit random value.
  79
  80   @retval TRUE         Random number generated successfully.
  81   @retval FALSE        Failed to generate the random number.
  82
  83 **/
  84 BOOLEAN
  85 EFIAPI
  86 ArchGetRandomNumber32 (
  87   OUT     UINT32                    *Rand
  88   )
  89 {
  90   return AsmRdRand32 (Rand);
  91 }
  92
  93 /**
  94   Generates a 64-bit random number.
  95
  96   @param[out] Rand     Buffer pointer to store the 64-bit random value.
  97
  98   @retval TRUE         Random number generated successfully.
  99   @retval FALSE        Failed to generate the random number.
 100
 101 **/
 102 BOOLEAN
 103 EFIAPI
 104 ArchGetRandomNumber64 (
 105   OUT     UINT64                    *Rand
 106   )
 107 {
 108   return AsmRdRand64 (Rand);
 109 }
 110
 111 /**
 112   Checks whether RDRAND is supported.
 113
 114   @retval TRUE         RDRAND is supported.
 115   @retval FALSE        RDRAND is not supported.
 116
 117 **/
 118 BOOLEAN
 119 EFIAPI
 120 ArchIsRngSupported (
 121   VOID
 122   )
 123 {
 124   /*
 125      Existing software depends on this always returning TRUE, so for
 126      now hard-code it.
 127
 128      return mRdRandSupported;
 129   */
 130   return TRUE;
 131 }