SecurityPkg/RandomNumberGenerator/RngDxe/IA32/GccRdRand.c

   1 /** @file
   2   RDRAND Support Routines for GCC environment.
   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 /**
  16   Generates a 16-bit random number through RDRAND instruction.
  17
  18   @param[out]  Rand          Buffer pointer to store the random result.
  19
  20   @retval TRUE               RDRAND call was successful.
  21   @retval FALSE              Failed attempts to call RDRAND.
  22
  23 **/
  24 BOOLEAN
  25 EFIAPI
  26 RdRand16Step (
  27   OUT UINT16       *Rand
  28   )
  29 {
  30   UINT8  Carry;
  31
  32   //
  33   // Uses byte code for RDRAND instruction,
  34   // in case that GCC version has no direct support on RDRAND assembly.
  35   //
  36   __asm__ __volatile__ (
  37     ".byte 0x66; .byte 0x0f; .byte 0xc7; .byte 0xf0; setc %1"
  38     :"=a"  (*Rand),
  39      "=qm" (Carry)
  40     );
  41
  42   return (BOOLEAN) Carry;
  43 }
  44
  45 /**
  46   Generates a 32-bit random number through RDRAND instruction.
  47
  48   @param[out]  Rand          Buffer pointer to store the random result.
  49
  50   @retval TRUE               RDRAND call was successful.
  51   @retval FALSE              Failed attempts to call RDRAND.
  52
  53 **/
  54 BOOLEAN
  55 EFIAPI
  56 RdRand32Step (
  57   OUT UINT32       *Rand
  58   )
  59 {
  60   UINT8  Carry;
  61
  62   __asm__ __volatile__ (
  63     ".byte 0x0f; .byte 0xc7; .byte 0xf0; setc %1"
  64     :"=a"  (*Rand),
  65      "=qm" (Carry)
  66     );
  67
  68   return (BOOLEAN) Carry;
  69 }