SecurityPkg/RandomNumberGenerator/RngDxe/IA32/RdRandWord.c

   1 /** @file
   2   RDRAND Support Routines.
   3
   4 Copyright (c) 2013, Intel Corporation. All rights reserved.<BR>
   5 This program and the accompanying materials
   6 are licensed and made available under the terms and conditions of the BSD License
   7 which accompanies this distribution.  The full text of the license may be found at
   8 http://opensource.org/licenses/bsd-license.php
   9
  10 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  11 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  12
  13 **/
  14
  15 #include "RdRand.h"
  16
  17 /**
  18   Generates a 64-bit random number through RDRAND instruction.
  19
  20   @param[out]  Rand          Buffer pointer to store the random result.
  21
  22   @retval TRUE               RDRAND call was successful.
  23   @retval FALSE              Failed attempts to call RDRAND.
  24
  25 **/
  26 BOOLEAN
  27 EFIAPI
  28 RdRand64Step  (
  29   OUT UINT64   *Rand
  30   )
  31 {
  32   UINT32  RandLow;
  33   UINT32  RandHigh;
  34
  35   //
  36   // Generating a 64-bit rand on a 32-bit system by
  37   // mapping two 32-bit RDRAND instructions.
  38   //
  39   if (!RdRand32Step (&RandLow)) {
  40     return FALSE;
  41   }
  42   if (!RdRand32Step (&RandHigh)) {
  43     return FALSE;
  44   }
  45
  46   *Rand = (UINT64) RandLow | LShiftU64 ((UINT64)RandHigh, 32);
  47
  48   return TRUE;
  49 }
  50
  51 /**
  52   Calls RDRAND to request a word-length random number.
  53
  54   @param[out]  Rand          Buffer pointer to store the random number.
  55   @param[in]   NeedRetry     Determine whether or not to loop retry.
  56
  57   @retval EFI_SUCCESS        Random word generation succeeded.
  58   @retval EFI_NOT_READY      Failed to request random word.
  59
  60 **/
  61 EFI_STATUS
  62 EFIAPI
  63 RdRandWord (
  64   OUT UINTN        *Rand,
  65   IN BOOLEAN       NeedRetry
  66   )
  67 {
  68   return RdRand32 (Rand, NeedRetry);
  69 }
  70
  71 /**
  72   Calls RDRAND to request multiple word-length random numbers.
  73
  74   @param[in]   Length        Size of the buffer, in words, to fill with.
  75   @param[out]  RandBuffer    Pointer to the buffer to store the random result.
  76
  77   @retval EFI_SUCCESS        Random words generation succeeded.
  78   @retval EFI_NOT_READY      Failed to request random words.
  79
  80 **/
  81 EFI_STATUS
  82 EFIAPI
  83 RdRandGetWords (
  84   IN UINTN         Length,
  85   OUT UINTN        *RandBuffer
  86   )
  87 {
  88   EFI_STATUS  Status;
  89   UINT32      Index;
  90
  91   for (Index = 0; Index < Length; Index++) {
  92     //
  93     // Obtain one word-length (32-bit) Random Number with possible retry-loop.
  94     //
  95     Status = RdRand32 (RandBuffer, TRUE);
  96     if (EFI_ERROR (Status)) {
  97       return Status;
  98     }
  99
 100     RandBuffer++;
 101   }
 102
 103   return EFI_SUCCESS;
 104 }