MdePkg/Library/BaseRngLib/AArch64/Rndr.c

   1 /** @file
   2   Random number generator service that uses the RNDR instruction
   3   to provide pseudorandom 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 #include <Library/RngLib.h>
  16
  17 #include "ArmRng.h"
  18 #include "BaseRngLibInternals.h"
  19
  20 STATIC BOOLEAN mRndrSupported;
  21
  22 //
  23 // Bit mask used to determine if RNDR instruction is supported.
  24 //
  25 #define RNDR_MASK                  ((UINT64)MAX_UINT16 << 60U)
  26
  27 /**
  28   The constructor function checks whether or not RNDR instruction is supported
  29   by the host hardware.
  30
  31   The constructor function checks whether or not RNDR instruction is supported.
  32   It will ASSERT() if RNDR instruction is not supported.
  33   It will always return EFI_SUCCESS.
  34
  35   @retval EFI_SUCCESS   The constructor always returns EFI_SUCCESS.
  36
  37 **/
  38 EFI_STATUS
  39 EFIAPI
  40 BaseRngLibConstructor (
  41   VOID
  42   )
  43 {
  44   UINT64 Isar0;
  45   //
  46   // Determine RNDR support by examining bits 63:60 of the ISAR0 register returned by
  47   // MSR. A non-zero value indicates that the processor supports the RNDR instruction.
  48   //
  49   Isar0 = ArmReadIdIsar0 ();
  50   ASSERT ((Isar0 & RNDR_MASK) != 0);
  51
  52   mRndrSupported = ((Isar0 & RNDR_MASK) != 0);
  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   UINT64 Rand64;
  73
  74   if (ArchGetRandomNumber64 (&Rand64)) {
  75     *Rand = Rand64 & MAX_UINT16;
  76     return TRUE;
  77   }
  78
  79   return FALSE;
  80 }
  81
  82 /**
  83   Generates a 32-bit random number.
  84
  85   @param[out] Rand     Buffer pointer to store the 32-bit random value.
  86
  87   @retval TRUE         Random number generated successfully.
  88   @retval FALSE        Failed to generate the random number.
  89
  90 **/
  91 BOOLEAN
  92 EFIAPI
  93 ArchGetRandomNumber32 (
  94   OUT     UINT32                    *Rand
  95   )
  96 {
  97   UINT64 Rand64;
  98
  99   if (ArchGetRandomNumber64 (&Rand64)) {
 100     *Rand = Rand64 & MAX_UINT32;
 101     return TRUE;
 102   }
 103
 104   return FALSE;
 105 }
 106
 107 /**
 108   Generates a 64-bit random number.
 109
 110   @param[out] Rand     Buffer pointer to store the 64-bit random value.
 111
 112   @retval TRUE         Random number generated successfully.
 113   @retval FALSE        Failed to generate the random number.
 114
 115 **/
 116 BOOLEAN
 117 EFIAPI
 118 ArchGetRandomNumber64 (
 119   OUT     UINT64                    *Rand
 120   )
 121 {
 122   return ArmRndr (Rand);
 123 }
 124
 125 /**
 126   Checks whether RNDR is supported.
 127
 128   @retval TRUE         RNDR is supported.
 129   @retval FALSE        RNDR is not supported.
 130
 131 **/
 132 BOOLEAN
 133 EFIAPI
 134 ArchIsRngSupported (
 135   VOID
 136   )
 137 {
 138   return mRndrSupported;
 139 }