[PATCH edk2-platforms 1/2] Silicon/Bcm2836: add random number generator driver

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

Expose the SoC's RNG peripheral via the EFI_RNG_PROTOCOL.
This is used by Linux to seed the KASLR routines.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 Silicon/Broadcom/Bcm283x/Drivers/RngDxe/RngDxe.c            | 203 ++++++++++++++++++++
 Silicon/Broadcom/Bcm283x/Drivers/RngDxe/RngDxe.inf          |  45 +++++
 Silicon/Broadcom/Bcm283x/Include/IndustryStandard/Bcm2836.h |   9 +
 3 files changed, 257 insertions(+)

diff --git a/Silicon/Broadcom/Bcm283x/Drivers/RngDxe/RngDxe.c b/Silicon/Broadcom/Bcm283x/Drivers/RngDxe/RngDxe.c
new file mode 100644
index 000000000000..399d93158547
--- /dev/null
+++ b/Silicon/Broadcom/Bcm283x/Drivers/RngDxe/RngDxe.c
@@ -0,0 +1,203 @@
+/** @file
+
+  This driver produces an EFI_RNG_PROTOCOL instance for the Broadcom 2836 RNG
+
+  Copyright (C) 2019, Linaro Ltd. 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/BaseMemoryLib.h>
+#include <Library/DebugLib.h>
+#include <Library/IoLib.h>
+#include <Library/UefiBootServicesTableLib.h>
+
+#include <IndustryStandard/Bcm2836.h>
+
+#include <Protocol/Rng.h>
+
+#define RNG_WARMUP_COUNT        0x40000
+#define RNG_MAX_RETRIES         0x100         // arbitrary upper bound
+
+/**
+  Returns information about the random number generation implementation.
+
+  @param[in]     This                 A pointer to the EFI_RNG_PROTOCOL
+                                      instance.
+  @param[in,out] RNGAlgorithmListSize On input, the size in bytes of
+                                      RNGAlgorithmList.
+                                      On output with a return code of
+                                      EFI_SUCCESS, the size in bytes of the
+                                      data returned in RNGAlgorithmList. On
+                                      output with a return code of
+                                      EFI_BUFFER_TOO_SMALL, the size of
+                                      RNGAlgorithmList required to obtain the
+                                      list.
+  @param[out] RNGAlgorithmList        A caller-allocated memory buffer filled
+                                      by the driver with one EFI_RNG_ALGORITHM
+                                      element for each supported RNG algorithm.
+                                      The list must not change across multiple
+                                      calls to the same driver. The first
+                                      algorithm in the list is the default
+                                      algorithm for the driver.
+
+  @retval EFI_SUCCESS                 The RNG algorithm list was returned
+                                      successfully.
+  @retval EFI_UNSUPPORTED             The services is not supported by this
+                                      driver.
+  @retval EFI_DEVICE_ERROR            The list of algorithms could not be
+                                      retrieved due to a hardware or firmware
+                                      error.
+  @retval EFI_INVALID_PARAMETER       One or more of the parameters are
+                                      incorrect.
+  @retval EFI_BUFFER_TOO_SMALL        The buffer RNGAlgorithmList is too small
+                                      to hold the result.
+
+**/
+STATIC
+EFI_STATUS
+EFIAPI
+Bcm2836RngGetInfo (
+  IN      EFI_RNG_PROTOCOL        *This,
+  IN OUT  UINTN                   *RNGAlgorithmListSize,
+  OUT     EFI_RNG_ALGORITHM       *RNGAlgorithmList
+  )
+{
+  if (This == NULL || RNGAlgorithmListSize == NULL) {
+    return EFI_INVALID_PARAMETER;
+  }
+
+  if (*RNGAlgorithmListSize < sizeof (EFI_RNG_ALGORITHM)) {
+    *RNGAlgorithmListSize = sizeof (EFI_RNG_ALGORITHM);
+    return EFI_BUFFER_TOO_SMALL;
+  }
+
+  if (RNGAlgorithmList == NULL) {
+    return EFI_INVALID_PARAMETER;
+  }
+
+  *RNGAlgorithmListSize = sizeof (EFI_RNG_ALGORITHM);
+  CopyGuid (RNGAlgorithmList, &gEfiRngAlgorithmRaw);
+
+  return EFI_SUCCESS;
+}
+
+/**
+  Produces and returns an RNG value using either the default or specified RNG
+  algorithm.
+
+  @param[in]  This                    A pointer to the EFI_RNG_PROTOCOL
+                                      instance.
+  @param[in]  RNGAlgorithm            A pointer to the EFI_RNG_ALGORITHM that
+                                      identifies the RNG algorithm to use. May
+                                      be NULL in which case the function will
+                                      use its default RNG algorithm.
+  @param[in]  RNGValueLength          The length in bytes of the memory buffer
+                                      pointed to by RNGValue. The driver shall
+                                      return exactly this numbers of bytes.
+  @param[out] RNGValue                A caller-allocated memory buffer filled
+                                      by the driver with the resulting RNG
+                                      value.
+
+  @retval EFI_SUCCESS                 The RNG value was returned successfully.
+  @retval EFI_UNSUPPORTED             The algorithm specified by RNGAlgorithm
+                                      is not supported by this driver.
+  @retval EFI_DEVICE_ERROR            An RNG value could not be retrieved due
+                                      to a hardware or firmware error.
+  @retval EFI_NOT_READY               There is not enough random data available
+                                      to satisfy the length requested by
+                                      RNGValueLength.
+  @retval EFI_INVALID_PARAMETER       RNGValue is NULL or RNGValueLength is
+                                      zero.
+
+**/
+STATIC
+EFI_STATUS
+EFIAPI
+Bcm2836RngGetRNG (
+  IN EFI_RNG_PROTOCOL            *This,
+  IN EFI_RNG_ALGORITHM           *RNGAlgorithm, OPTIONAL
+  IN UINTN                       RNGValueLength,
+  OUT UINT8                      *RNGValue
+  )
+{
+  UINT32 Val;
+  UINT32 Num;
+  UINT32 Retries;
+
+  if (This == NULL || RNGValueLength == 0 || RNGValue == NULL) {
+    return EFI_INVALID_PARAMETER;
+  }
+
+  //
+  // We only support the raw algorithm, so reject requests for anything else
+  //
+  if (RNGAlgorithm != NULL &&
+      !CompareGuid (RNGAlgorithm, &gEfiRngAlgorithmRaw)) {
+    return EFI_UNSUPPORTED;
+  }
+
+  while (RNGValueLength > 0) {
+    Retries = RNG_MAX_RETRIES;
+    do {
+      Num = MmioRead32 (RNG_STATUS) >> 24;
+      MemoryFence ();
+    } while (!Num && Retries-- > 0);
+
+    if (!Num) {
+      return EFI_DEVICE_ERROR;
+    }
+
+    while (RNGValueLength >= sizeof (UINT32) && Num > 0) {
+      WriteUnaligned32 ((VOID *)RNGValue, MmioRead32 (RNG_DATA));
+      RNGValue += sizeof (UINT32);
+      RNGValueLength -= sizeof (UINT32);
+      Num--;
+    }
+
+    if (RNGValueLength > 0 && Num > 0) {
+      Val = MmioRead32 (RNG_DATA);
+      while (RNGValueLength--) {
+        *RNGValue++ = (UINT8)Val;
+        Val >>= 8;
+      }
+    }
+  }
+  return EFI_SUCCESS;
+}
+
+STATIC EFI_RNG_PROTOCOL mBcm2836RngProtocol = {
+  Bcm2836RngGetInfo,
+  Bcm2836RngGetRNG
+};
+
+//
+// Entry point of this driver.
+//
+EFI_STATUS
+EFIAPI
+Bcm2836RngEntryPoint (
+  IN EFI_HANDLE       ImageHandle,
+  IN EFI_SYSTEM_TABLE *SystemTable
+  )
+{
+  EFI_STATUS      Status;
+
+  Status = gBS->InstallMultipleProtocolInterfaces (&ImageHandle,
+                  &gEfiRngProtocolGuid, &mBcm2836RngProtocol,
+                  NULL);
+  ASSERT_EFI_ERROR (Status);
+
+  MmioWrite32 (RNG_STATUS, RNG_WARMUP_COUNT);
+  MmioWrite32 (RNG_CTRL, RNG_CTRL_ENABLE);
+
+  return EFI_SUCCESS;
+}
diff --git a/Silicon/Broadcom/Bcm283x/Drivers/RngDxe/RngDxe.inf b/Silicon/Broadcom/Bcm283x/Drivers/RngDxe/RngDxe.inf
new file mode 100644
index 000000000000..45e8825244f7
--- /dev/null
+++ b/Silicon/Broadcom/Bcm283x/Drivers/RngDxe/RngDxe.inf
@@ -0,0 +1,45 @@
+#/** @file
+#
+#  Copyright (c) 2019 Linaro, Ltd. All rights reserved.
+#
+#  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.
+#
+#**/
+
+[Defines]
+  INF_VERSION                    = 0x0001001B
+  BASE_NAME                      = RngDxe
+  FILE_GUID                      = 9743084e-c82a-4714-b2ba-f571f81cb021
+  MODULE_TYPE                    = DXE_DRIVER
+  VERSION_STRING                 = 1.0
+  ENTRY_POINT                    = Bcm2836RngEntryPoint
+
+[Sources]
+  RngDxe.c
+
+[Packages]
+  MdePkg/MdePkg.dec
+  Silicon/Broadcom/Bcm283x/Bcm283x.dec
+
+[LibraryClasses]
+  BaseLib
+  BaseMemoryLib
+  DebugLib
+  IoLib
+  UefiBootServicesTableLib
+  UefiDriverEntryPoint
+
+[Protocols]
+  gEfiRngProtocolGuid              ## PRODUCES
+
+[Guids]
+  gEfiRngAlgorithmRaw
+
+[Depex]
+  TRUE
diff --git a/Silicon/Broadcom/Bcm283x/Include/IndustryStandard/Bcm2836.h b/Silicon/Broadcom/Bcm283x/Include/IndustryStandard/Bcm2836.h
index f9fffb764649..f06eb2312c61 100644
--- a/Silicon/Broadcom/Bcm283x/Include/IndustryStandard/Bcm2836.h
+++ b/Silicon/Broadcom/Bcm283x/Include/IndustryStandard/Bcm2836.h
@@ -69,4 +69,13 @@
 #define BCM2836_INTC_TIMER_CONTROL_OFFSET                   0x00000040
 #define BCM2836_INTC_TIMER_PENDING_OFFSET                   0x00000060
 
+/* random number generator */
+#define RNG_BASE_ADDRESS   (BCM2836_SOC_REGISTERS + 0x00104000)
+
+#define RNG_CTRL           (RNG_BASE_ADDRESS + 0x0)
+#define RNG_STATUS         (RNG_BASE_ADDRESS + 0x4)
+#define RNG_DATA           (RNG_BASE_ADDRESS + 0x8)
+
+#define RNG_CTRL_ENABLE    0x1
+
 #endif /*__BCM2836_H__ */
-- 
2.20.1