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/** @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;
}
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