/** @file | |
Random number generator services that uses RdRand instruction access | |
to provide high-quality random numbers. | |
Copyright (c) 2015, Intel Corporation. All rights reserved.<BR> | |
This program and the accompanying materials | |
are licensed and made available under the terms and conditions of the BSD License | |
which accompanies this distribution. The full text of the license may be found at | |
http://opensource.org/licenses/bsd-license.php | |
THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, | |
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED. | |
**/ | |
#include <Library/BaseLib.h> | |
#include <Library/DebugLib.h> | |
// | |
// Bit mask used to determine if RdRand instruction is supported. | |
// | |
#define RDRAND_MASK BIT30 | |
// | |
// Limited retry number when valid random data is returned. | |
// Uses the recommended value defined in Section 7.3.17 of "Intel 64 and IA-32 | |
// Architectures Software Developer's Mannual". | |
// | |
#define RDRAND_RETRY_LIMIT 10 | |
/** | |
The constructor function checks whether or not RDRAND instruction is supported | |
by the host hardware. | |
The constructor function checks whether or not RDRAND instruction is supported. | |
It will ASSERT() if RDRAND instruction is not supported. | |
It will always return RETURN_SUCCESS. | |
@retval RETURN_SUCCESS The constructor always returns EFI_SUCCESS. | |
**/ | |
RETURN_STATUS | |
EFIAPI | |
BaseRngLibConstructor ( | |
VOID | |
) | |
{ | |
UINT32 RegEcx; | |
// | |
// Determine RDRAND support by examining bit 30 of the ECX register returned by | |
// CPUID. A value of 1 indicates that processor support RDRAND instruction. | |
// | |
AsmCpuid (1, 0, 0, &RegEcx, 0); | |
ASSERT ((RegEcx & RDRAND_MASK) == RDRAND_MASK); | |
return RETURN_SUCCESS; | |
} | |
/** | |
Generates a 16-bit random number. | |
if Rand is NULL, then ASSERT(). | |
@param[out] Rand Buffer pointer to store the 16-bit random value. | |
@retval TRUE Random number generated successfully. | |
@retval FALSE Failed to generate the random number. | |
**/ | |
BOOLEAN | |
EFIAPI | |
GetRandomNumber16 ( | |
OUT UINT16 *Rand | |
) | |
{ | |
UINT32 Index; | |
ASSERT (Rand != NULL); | |
// | |
// A loop to fetch a 16 bit random value with a retry count limit. | |
// | |
for (Index = 0; Index < RDRAND_RETRY_LIMIT; Index++) { | |
if (AsmRdRand16 (Rand)) { | |
return TRUE; | |
} | |
} | |
return FALSE; | |
} | |
/** | |
Generates a 32-bit random number. | |
if Rand is NULL, then ASSERT(). | |
@param[out] Rand Buffer pointer to store the 32-bit random value. | |
@retval TRUE Random number generated successfully. | |
@retval FALSE Failed to generate the random number. | |
**/ | |
BOOLEAN | |
EFIAPI | |
GetRandomNumber32 ( | |
OUT UINT32 *Rand | |
) | |
{ | |
UINT32 Index; | |
ASSERT (Rand != NULL); | |
// | |
// A loop to fetch a 32 bit random value with a retry count limit. | |
// | |
for (Index = 0; Index < RDRAND_RETRY_LIMIT; Index++) { | |
if (AsmRdRand32 (Rand)) { | |
return TRUE; | |
} | |
} | |
return FALSE; | |
} | |
/** | |
Generates a 64-bit random number. | |
if Rand is NULL, then ASSERT(). | |
@param[out] Rand Buffer pointer to store the 64-bit random value. | |
@retval TRUE Random number generated successfully. | |
@retval FALSE Failed to generate the random number. | |
**/ | |
BOOLEAN | |
EFIAPI | |
GetRandomNumber64 ( | |
OUT UINT64 *Rand | |
) | |
{ | |
UINT32 Index; | |
ASSERT (Rand != NULL); | |
// | |
// A loop to fetch a 64 bit random value with a retry count limit. | |
// | |
for (Index = 0; Index < RDRAND_RETRY_LIMIT; Index++) { | |
if (AsmRdRand64 (Rand)) { | |
return TRUE; | |
} | |
} | |
return FALSE; | |
} | |
/** | |
Generates a 128-bit random number. | |
if Rand is NULL, then ASSERT(). | |
@param[out] Rand Buffer pointer to store the 128-bit random value. | |
@retval TRUE Random number generated successfully. | |
@retval FALSE Failed to generate the random number. | |
**/ | |
BOOLEAN | |
EFIAPI | |
GetRandomNumber128 ( | |
OUT UINT64 *Rand | |
) | |
{ | |
ASSERT (Rand != NULL); | |
// | |
// Read first 64 bits | |
// | |
if (!GetRandomNumber64 (Rand)) { | |
return FALSE; | |
} | |
// | |
// Read second 64 bits | |
// | |
return GetRandomNumber64 (++Rand); | |
} |