/** @file
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This driver produces an EFI_RNG_PROTOCOL instance for the Broadcom 2835 RNG
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Copyright (C) 2019, Linaro Ltd. All rights reserved.<BR>
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SPDX-License-Identifier: BSD-2-Clause-Patent
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**/
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#include <Library/BaseLib.h>
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#include <Library/BaseMemoryLib.h>
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#include <Library/DebugLib.h>
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#include <Library/IoLib.h>
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#include <Library/UefiBootServicesTableLib.h>
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#include <IndustryStandard/Bcm2835Rng.h>
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#include <Protocol/Rng.h>
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#define RNG_WARMUP_COUNT 0x40000
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#define RNG_MAX_RETRIES 0x100 // arbitrary upper bound
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/**
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Returns information about the random number generation implementation.
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@param[in] This A pointer to the EFI_RNG_PROTOCOL
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instance.
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@param[in,out] RNGAlgorithmListSize On input, the size in bytes of
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RNGAlgorithmList.
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On output with a return code of
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EFI_SUCCESS, the size in bytes of the
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data returned in RNGAlgorithmList. On
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output with a return code of
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EFI_BUFFER_TOO_SMALL, the size of
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RNGAlgorithmList required to obtain the
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list.
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@param[out] RNGAlgorithmList A caller-allocated memory buffer filled
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by the driver with one EFI_RNG_ALGORITHM
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element for each supported RNG algorithm.
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The list must not change across multiple
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calls to the same driver. The first
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algorithm in the list is the default
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algorithm for the driver.
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@retval EFI_SUCCESS The RNG algorithm list was returned
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successfully.
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@retval EFI_UNSUPPORTED The services is not supported by this
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driver.
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@retval EFI_DEVICE_ERROR The list of algorithms could not be
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retrieved due to a hardware or firmware
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error.
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@retval EFI_INVALID_PARAMETER One or more of the parameters are
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incorrect.
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@retval EFI_BUFFER_TOO_SMALL The buffer RNGAlgorithmList is too small
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to hold the result.
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**/
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STATIC
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EFI_STATUS
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EFIAPI
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Bcm2835RngGetInfo (
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IN EFI_RNG_PROTOCOL *This,
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IN OUT UINTN *RNGAlgorithmListSize,
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OUT EFI_RNG_ALGORITHM *RNGAlgorithmList
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)
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{
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if (This == NULL || RNGAlgorithmListSize == NULL) {
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return EFI_INVALID_PARAMETER;
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}
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if (*RNGAlgorithmListSize < sizeof (EFI_RNG_ALGORITHM)) {
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*RNGAlgorithmListSize = sizeof (EFI_RNG_ALGORITHM);
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return EFI_BUFFER_TOO_SMALL;
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}
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if (RNGAlgorithmList == NULL) {
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return EFI_INVALID_PARAMETER;
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}
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*RNGAlgorithmListSize = sizeof (EFI_RNG_ALGORITHM);
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CopyGuid (RNGAlgorithmList, &gEfiRngAlgorithmRaw);
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return EFI_SUCCESS;
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}
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/**
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Produces and returns an RNG value using either the default or specified RNG
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algorithm.
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@param[in] This A pointer to the EFI_RNG_PROTOCOL
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instance.
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@param[in] RNGAlgorithm A pointer to the EFI_RNG_ALGORITHM that
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identifies the RNG algorithm to use. May
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be NULL in which case the function will
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use its default RNG algorithm.
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@param[in] RNGValueLength The length in bytes of the memory buffer
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pointed to by RNGValue. The driver shall
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return exactly this numbers of bytes.
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@param[out] RNGValue A caller-allocated memory buffer filled
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by the driver with the resulting RNG
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value.
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@retval EFI_SUCCESS The RNG value was returned successfully.
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@retval EFI_UNSUPPORTED The algorithm specified by RNGAlgorithm
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is not supported by this driver.
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@retval EFI_DEVICE_ERROR An RNG value could not be retrieved due
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to a hardware or firmware error.
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@retval EFI_NOT_READY There is not enough random data available
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to satisfy the length requested by
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RNGValueLength.
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@retval EFI_INVALID_PARAMETER RNGValue is NULL or RNGValueLength is
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zero.
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**/
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STATIC
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EFI_STATUS
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EFIAPI
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Bcm2835RngGetRNG (
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IN EFI_RNG_PROTOCOL *This,
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IN EFI_RNG_ALGORITHM *RNGAlgorithm, OPTIONAL
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IN UINTN RNGValueLength,
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OUT UINT8 *RNGValue
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)
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{
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UINT32 Val;
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UINT32 Num;
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UINT32 Retries;
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if (This == NULL || RNGValueLength == 0 || RNGValue == NULL) {
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return EFI_INVALID_PARAMETER;
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}
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//
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// We only support the raw algorithm, so reject requests for anything else
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//
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if (RNGAlgorithm != NULL &&
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!CompareGuid (RNGAlgorithm, &gEfiRngAlgorithmRaw)) {
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return EFI_UNSUPPORTED;
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}
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while (RNGValueLength > 0) {
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Retries = RNG_MAX_RETRIES;
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do {
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Num = MmioRead32 (RNG_STATUS) >> 24;
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MemoryFence ();
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} while (!Num && Retries-- > 0);
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if (!Num) {
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return EFI_DEVICE_ERROR;
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}
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while (RNGValueLength >= sizeof (UINT32) && Num > 0) {
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WriteUnaligned32 ((VOID *)RNGValue, MmioRead32 (RNG_DATA));
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RNGValue += sizeof (UINT32);
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RNGValueLength -= sizeof (UINT32);
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Num--;
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}
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if (RNGValueLength > 0 && Num > 0) {
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Val = MmioRead32 (RNG_DATA);
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while (RNGValueLength--) {
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*RNGValue++ = (UINT8)Val;
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Val >>= 8;
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}
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}
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}
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return EFI_SUCCESS;
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}
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STATIC EFI_RNG_PROTOCOL mBcm2835RngProtocol = {
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Bcm2835RngGetInfo,
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Bcm2835RngGetRNG
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};
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//
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// Entry point of this driver.
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//
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EFI_STATUS
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EFIAPI
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Bcm2835RngEntryPoint (
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IN EFI_HANDLE ImageHandle,
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IN EFI_SYSTEM_TABLE *SystemTable
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)
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{
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EFI_STATUS Status;
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Status = gBS->InstallMultipleProtocolInterfaces (&ImageHandle,
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&gEfiRngProtocolGuid, &mBcm2835RngProtocol,
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NULL);
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ASSERT_EFI_ERROR (Status);
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MmioWrite32 (RNG_STATUS, RNG_WARMUP_COUNT);
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MmioWrite32 (RNG_CTRL, RNG_CTRL_ENABLE);
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return EFI_SUCCESS;
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}
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