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/** @file
Random number generator services that uses RdRand instruction access
to provide high-quality random numbers.
Copyright (c) 2021, NUVIA Inc. All rights reserved.<BR>
Copyright (c) 2015, Intel Corporation. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent
**/
#include <Uefi.h>
#include <Library/BaseLib.h>
#include <Library/DebugLib.h>
#include "BaseRngLibInternals.h"
//
// Bit mask used to determine if RdRand instruction is supported.
//
#define RDRAND_MASK BIT30
STATIC BOOLEAN mRdRandSupported;
/**
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 EFI_SUCCESS.
@retval EFI_SUCCESS The constructor always returns EFI_SUCCESS.
**/
EFI_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);
mRdRandSupported = ((RegEcx & RDRAND_MASK) == RDRAND_MASK);
return EFI_SUCCESS;
}
/**
Generates a 16-bit random number.
@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
ArchGetRandomNumber16 (
OUT UINT16 *Rand
)
{
return AsmRdRand16 (Rand);
}
/**
Generates a 32-bit random number.
@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
ArchGetRandomNumber32 (
OUT UINT32 *Rand
)
{
return AsmRdRand32 (Rand);
}
/**
Generates a 64-bit random number.
@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
ArchGetRandomNumber64 (
OUT UINT64 *Rand
)
{
return AsmRdRand64 (Rand);
}
/**
Checks whether RDRAND is supported.
@retval TRUE RDRAND is supported.
@retval FALSE RDRAND is not supported.
**/
BOOLEAN
EFIAPI
ArchIsRngSupported (
VOID
)
{
/*
Existing software depends on this always returning TRUE, so for
now hard-code it.
return mRdRandSupported;
*/
return TRUE;
}
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