/** @file

  This driver produces EFI_RNG_PROTOCOL instances for virtio-rng devices.

  The implementation is based on OvmfPkg/VirtioScsiDxe/VirtioScsi.c

  Copyright (C) 2012, Red Hat, Inc.
  Copyright (c) 2012 - 2014, Intel Corporation. All rights reserved.<BR>

  This driver:

  Copyright (C) 2016, Linaro Ltd.

  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/BaseMemoryLib.h>
#include <Library/DebugLib.h>
#include <Library/MemoryAllocationLib.h>
#include <Library/UefiBootServicesTableLib.h>
#include <Library/UefiLib.h>
#include <Library/VirtioLib.h>

#include "VirtioRng.h"

/**
  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
VirtioRngGetInfo (
  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
VirtioRngGetRNG (
  IN EFI_RNG_PROTOCOL            *This,
  IN EFI_RNG_ALGORITHM           *RNGAlgorithm, OPTIONAL
  IN UINTN                       RNGValueLength,
  OUT UINT8                      *RNGValue
  )
{
  VIRTIO_RNG_DEV            *Dev;
  DESC_INDICES              Indices;
  volatile UINT8            *Buffer;
  UINTN                     Index;
  UINT32                    Len;
  UINT32                    BufferSize;
  EFI_STATUS                Status;

  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;
  }

  Buffer = (volatile UINT8 *)AllocatePool (RNGValueLength);
  if (Buffer == NULL) {
    return EFI_DEVICE_ERROR;
  }

  Dev = VIRTIO_ENTROPY_SOURCE_FROM_RNG (This);

  //
  // The Virtio RNG device may return less data than we asked it to, and can
  // only return MAX_UINT32 bytes per invocation. So loop as long as needed to
  // get all the entropy we were asked for.
  //
  for (Index = 0; Index < RNGValueLength; Index += Len) {
    BufferSize = (UINT32)MIN (RNGValueLength - Index, (UINTN)MAX_UINT32);

    VirtioPrepare (&Dev->Ring, &Indices);
    VirtioAppendDesc (&Dev->Ring,
      (UINTN)Buffer + Index,
      BufferSize,
      VRING_DESC_F_WRITE,
      &Indices);

    if (VirtioFlush (Dev->VirtIo, 0, &Dev->Ring, &Indices, &Len) !=
        EFI_SUCCESS) {
      Status = EFI_DEVICE_ERROR;
      goto FreeBuffer;
    }
    ASSERT (Len > 0);
    ASSERT (Len <= BufferSize);
  }

  for (Index = 0; Index < RNGValueLength; Index++) {
    RNGValue[Index] = Buffer[Index];
  }
  Status = EFI_SUCCESS;

FreeBuffer:
  FreePool ((VOID *)Buffer);
  return Status;
}

STATIC
EFI_STATUS
EFIAPI
VirtioRngInit (
  IN OUT VIRTIO_RNG_DEV *Dev
  )
{
  UINT8      NextDevStat;
  EFI_STATUS Status;
  UINT16     QueueSize;
  UINT64     Features;

  //
  // Execute virtio-0.9.5, 2.2.1 Device Initialization Sequence.
  //
  NextDevStat = 0;             // step 1 -- reset device
  Status = Dev->VirtIo->SetDeviceStatus (Dev->VirtIo, NextDevStat);
  if (EFI_ERROR (Status)) {
    goto Failed;
  }

  NextDevStat |= VSTAT_ACK;    // step 2 -- acknowledge device presence
  Status = Dev->VirtIo->SetDeviceStatus (Dev->VirtIo, NextDevStat);
  if (EFI_ERROR (Status)) {
    goto Failed;
  }

  NextDevStat |= VSTAT_DRIVER; // step 3 -- we know how to drive it
  Status = Dev->VirtIo->SetDeviceStatus (Dev->VirtIo, NextDevStat);
  if (EFI_ERROR (Status)) {
    goto Failed;
  }

  //
  // Set Page Size - MMIO VirtIo Specific
  //
  Status = Dev->VirtIo->SetPageSize (Dev->VirtIo, EFI_PAGE_SIZE);
  if (EFI_ERROR (Status)) {
    goto Failed;
  }

  //
  // step 4a -- retrieve and validate features
  //
  Status = Dev->VirtIo->GetDeviceFeatures (Dev->VirtIo, &Features);
  if (EFI_ERROR (Status)) {
    goto Failed;
  }

  Features &= VIRTIO_F_VERSION_1;

  //
  // In virtio-1.0, feature negotiation is expected to complete before queue
  // discovery, and the device can also reject the selected set of features.
  //
  if (Dev->VirtIo->Revision >= VIRTIO_SPEC_REVISION (1, 0, 0)) {
    Status = Virtio10WriteFeatures (Dev->VirtIo, Features, &NextDevStat);
    if (EFI_ERROR (Status)) {
      goto Failed;
    }
  }

  //
  // step 4b -- allocate request virtqueue, just use #0
  //
  Status = Dev->VirtIo->SetQueueSel (Dev->VirtIo, 0);
  if (EFI_ERROR (Status)) {
    goto Failed;
  }
  Status = Dev->VirtIo->GetQueueNumMax (Dev->VirtIo, &QueueSize);
  if (EFI_ERROR (Status)) {
    goto Failed;
  }

  //
  // VirtioRngGetRNG() uses one descriptor
  //
  if (QueueSize < 1) {
    Status = EFI_UNSUPPORTED;
    goto Failed;
  }

  Status = VirtioRingInit (QueueSize, &Dev->Ring);
  if (EFI_ERROR (Status)) {
    goto Failed;
  }

  //
  // Additional steps for MMIO: align the queue appropriately, and set the
  // size. If anything fails from here on, we must release the ring resources.
  //
  Status = Dev->VirtIo->SetQueueNum (Dev->VirtIo, QueueSize);
  if (EFI_ERROR (Status)) {
    goto ReleaseQueue;
  }

  Status = Dev->VirtIo->SetQueueAlign (Dev->VirtIo, EFI_PAGE_SIZE);
  if (EFI_ERROR (Status)) {
    goto ReleaseQueue;
  }

  //
  // step 4c -- Report GPFN (guest-physical frame number) of queue.
  //
  Status = Dev->VirtIo->SetQueueAddress (Dev->VirtIo, &Dev->Ring);
  if (EFI_ERROR (Status)) {
    goto ReleaseQueue;
  }

  //
  // step 5 -- Report understood features and guest-tuneables.
  //
  if (Dev->VirtIo->Revision < VIRTIO_SPEC_REVISION (1, 0, 0)) {
    Features &= ~(UINT64)VIRTIO_F_VERSION_1;
    Status = Dev->VirtIo->SetGuestFeatures (Dev->VirtIo, Features);
    if (EFI_ERROR (Status)) {
      goto ReleaseQueue;
    }
  }

  //
  // step 6 -- initialization complete
  //
  NextDevStat |= VSTAT_DRIVER_OK;
  Status = Dev->VirtIo->SetDeviceStatus (Dev->VirtIo, NextDevStat);
  if (EFI_ERROR (Status)) {
    goto ReleaseQueue;
  }

  //
  // populate the exported interface's attributes
  //
  Dev->Rng.GetInfo    = VirtioRngGetInfo;
  Dev->Rng.GetRNG     = VirtioRngGetRNG;

  return EFI_SUCCESS;

ReleaseQueue:
  VirtioRingUninit (&Dev->Ring);

Failed:
  //
  // Notify the host about our failure to setup: virtio-0.9.5, 2.2.2.1 Device
  // Status. VirtIo access failure here should not mask the original error.
  //
  NextDevStat |= VSTAT_FAILED;
  Dev->VirtIo->SetDeviceStatus (Dev->VirtIo, NextDevStat);

  return Status; // reached only via Failed above
}


STATIC
VOID
EFIAPI
VirtioRngUninit (
  IN OUT VIRTIO_RNG_DEV *Dev
  )
{
  //
  // Reset the virtual device -- see virtio-0.9.5, 2.2.2.1 Device Status. When
  // VIRTIO_CFG_WRITE() returns, the host will have learned to stay away from
  // the old comms area.
  //
  Dev->VirtIo->SetDeviceStatus (Dev->VirtIo, 0);
  VirtioRingUninit (&Dev->Ring);
}

//
// Event notification function enqueued by ExitBootServices().
//

STATIC
VOID
EFIAPI
VirtioRngExitBoot (
  IN  EFI_EVENT Event,
  IN  VOID      *Context
  )
{
  VIRTIO_RNG_DEV *Dev;

  //
  // Reset the device. This causes the hypervisor to forget about the virtio
  // ring.
  //
  // We allocated said ring in EfiBootServicesData type memory, and code
  // executing after ExitBootServices() is permitted to overwrite it.
  //
  Dev = Context;
  Dev->VirtIo->SetDeviceStatus (Dev->VirtIo, 0);
}


//
// Probe, start and stop functions of this driver, called by the DXE core for
// specific devices.
//
// The following specifications document these interfaces:
// - Driver Writer's Guide for UEFI 2.3.1 v1.01, 9 Driver Binding Protocol
// - UEFI Spec 2.3.1 + Errata C, 10.1 EFI Driver Binding Protocol
//
// The implementation follows:
// - Driver Writer's Guide for UEFI 2.3.1 v1.01
//   - 5.1.3.4 OpenProtocol() and CloseProtocol()
// - UEFI Spec 2.3.1 + Errata C
//   -  6.3 Protocol Handler Services
//

STATIC
EFI_STATUS
EFIAPI
VirtioRngDriverBindingSupported (
  IN EFI_DRIVER_BINDING_PROTOCOL *This,
  IN EFI_HANDLE                  DeviceHandle,
  IN EFI_DEVICE_PATH_PROTOCOL    *RemainingDevicePath
  )
{
  EFI_STATUS             Status;
  VIRTIO_DEVICE_PROTOCOL *VirtIo;

  //
  // Attempt to open the device with the VirtIo set of interfaces. On success,
  // the protocol is "instantiated" for the VirtIo device. Covers duplicate
  // open attempts (EFI_ALREADY_STARTED).
  //
  Status = gBS->OpenProtocol (
                  DeviceHandle,               // candidate device
                  &gVirtioDeviceProtocolGuid, // for generic VirtIo access
                  (VOID **)&VirtIo,           // handle to instantiate
                  This->DriverBindingHandle,  // requestor driver identity
                  DeviceHandle,               // ControllerHandle, according to
                                              // the UEFI Driver Model
                  EFI_OPEN_PROTOCOL_BY_DRIVER // get exclusive VirtIo access to
                                              // the device; to be released
                  );
  if (EFI_ERROR (Status)) {
    return Status;
  }

  if (VirtIo->SubSystemDeviceId != VIRTIO_SUBSYSTEM_ENTROPY_SOURCE) {
    Status = EFI_UNSUPPORTED;
  }

  //
  // We needed VirtIo access only transitorily, to see whether we support the
  // device or not.
  //
  gBS->CloseProtocol (DeviceHandle, &gVirtioDeviceProtocolGuid,
         This->DriverBindingHandle, DeviceHandle);
  return Status;
}

STATIC
EFI_STATUS
EFIAPI
VirtioRngDriverBindingStart (
  IN EFI_DRIVER_BINDING_PROTOCOL *This,
  IN EFI_HANDLE                  DeviceHandle,
  IN EFI_DEVICE_PATH_PROTOCOL    *RemainingDevicePath
  )
{
  VIRTIO_RNG_DEV  *Dev;
  EFI_STATUS Status;

  Dev = (VIRTIO_RNG_DEV *) AllocateZeroPool (sizeof *Dev);
  if (Dev == NULL) {
    return EFI_OUT_OF_RESOURCES;
  }

  Status = gBS->OpenProtocol (DeviceHandle, &gVirtioDeviceProtocolGuid,
                  (VOID **)&Dev->VirtIo, This->DriverBindingHandle,
                  DeviceHandle, EFI_OPEN_PROTOCOL_BY_DRIVER);
  if (EFI_ERROR (Status)) {
    goto FreeVirtioRng;
  }

  //
  // VirtIo access granted, configure virtio-rng device.
  //
  Status = VirtioRngInit (Dev);
  if (EFI_ERROR (Status)) {
    goto CloseVirtIo;
  }

  Status = gBS->CreateEvent (EVT_SIGNAL_EXIT_BOOT_SERVICES, TPL_CALLBACK,
                  &VirtioRngExitBoot, Dev, &Dev->ExitBoot);
  if (EFI_ERROR (Status)) {
    goto UninitDev;
  }

  //
  // Setup complete, attempt to export the driver instance's EFI_RNG_PROTOCOL
  // interface.
  //
  Dev->Signature = VIRTIO_RNG_SIG;
  Status = gBS->InstallProtocolInterface (&DeviceHandle,
                  &gEfiRngProtocolGuid, EFI_NATIVE_INTERFACE,
                  &Dev->Rng);
  if (EFI_ERROR (Status)) {
    goto CloseExitBoot;
  }

  return EFI_SUCCESS;

CloseExitBoot:
  gBS->CloseEvent (Dev->ExitBoot);

UninitDev:
  VirtioRngUninit (Dev);

CloseVirtIo:
  gBS->CloseProtocol (DeviceHandle, &gVirtioDeviceProtocolGuid,
         This->DriverBindingHandle, DeviceHandle);

FreeVirtioRng:
  FreePool (Dev);

  return Status;
}


STATIC
EFI_STATUS
EFIAPI
VirtioRngDriverBindingStop (
  IN EFI_DRIVER_BINDING_PROTOCOL *This,
  IN EFI_HANDLE                  DeviceHandle,
  IN UINTN                       NumberOfChildren,
  IN EFI_HANDLE                  *ChildHandleBuffer
  )
{
  EFI_STATUS                      Status;
  EFI_RNG_PROTOCOL                *Rng;
  VIRTIO_RNG_DEV                  *Dev;

  Status = gBS->OpenProtocol (
                  DeviceHandle,                     // candidate device
                  &gEfiRngProtocolGuid,             // retrieve the RNG iface
                  (VOID **)&Rng,                    // target pointer
                  This->DriverBindingHandle,        // requestor driver ident.
                  DeviceHandle,                     // lookup req. for dev.
                  EFI_OPEN_PROTOCOL_GET_PROTOCOL    // lookup only, no new ref.
                  );
  if (EFI_ERROR (Status)) {
    return Status;
  }

  Dev = VIRTIO_ENTROPY_SOURCE_FROM_RNG (Rng);

  //
  // Handle Stop() requests for in-use driver instances gracefully.
  //
  Status = gBS->UninstallProtocolInterface (DeviceHandle,
                  &gEfiRngProtocolGuid, &Dev->Rng);
  if (EFI_ERROR (Status)) {
    return Status;
  }

  gBS->CloseEvent (Dev->ExitBoot);

  VirtioRngUninit (Dev);

  gBS->CloseProtocol (DeviceHandle, &gVirtioDeviceProtocolGuid,
         This->DriverBindingHandle, DeviceHandle);

  FreePool (Dev);

  return EFI_SUCCESS;
}


//
// The static object that groups the Supported() (ie. probe), Start() and
// Stop() functions of the driver together. Refer to UEFI Spec 2.3.1 + Errata
// C, 10.1 EFI Driver Binding Protocol.
//
STATIC EFI_DRIVER_BINDING_PROTOCOL gDriverBinding = {
  &VirtioRngDriverBindingSupported,
  &VirtioRngDriverBindingStart,
  &VirtioRngDriverBindingStop,
  0x10, // Version, must be in [0x10 .. 0xFFFFFFEF] for IHV-developed drivers
  NULL, // ImageHandle, to be overwritten by
        // EfiLibInstallDriverBindingComponentName2() in VirtioRngEntryPoint()
  NULL  // DriverBindingHandle, ditto
};


//
// The purpose of the following scaffolding (EFI_COMPONENT_NAME_PROTOCOL and
// EFI_COMPONENT_NAME2_PROTOCOL implementation) is to format the driver's name
// in English, for display on standard console devices. This is recommended for
// UEFI drivers that follow the UEFI Driver Model. Refer to the Driver Writer's
// Guide for UEFI 2.3.1 v1.01, 11 UEFI Driver and Controller Names.
//

STATIC
EFI_UNICODE_STRING_TABLE mDriverNameTable[] = {
  { "eng;en", L"Virtio Random Number Generator Driver" },
  { NULL,     NULL                   }
};

STATIC
EFI_COMPONENT_NAME_PROTOCOL gComponentName;

STATIC
EFI_STATUS
EFIAPI
VirtioRngGetDriverName (
  IN  EFI_COMPONENT_NAME_PROTOCOL *This,
  IN  CHAR8                       *Language,
  OUT CHAR16                      **DriverName
  )
{
  return LookupUnicodeString2 (
           Language,
           This->SupportedLanguages,
           mDriverNameTable,
           DriverName,
           (BOOLEAN)(This == &gComponentName) // Iso639Language
           );
}

STATIC
EFI_STATUS
EFIAPI
VirtioRngGetDeviceName (
  IN  EFI_COMPONENT_NAME_PROTOCOL *This,
  IN  EFI_HANDLE                  DeviceHandle,
  IN  EFI_HANDLE                  ChildHandle,
  IN  CHAR8                       *Language,
  OUT CHAR16                      **ControllerName
  )
{
  return EFI_UNSUPPORTED;
}

STATIC
EFI_COMPONENT_NAME_PROTOCOL gComponentName = {
  &VirtioRngGetDriverName,
  &VirtioRngGetDeviceName,
  "eng" // SupportedLanguages, ISO 639-2 language codes
};

STATIC
EFI_COMPONENT_NAME2_PROTOCOL gComponentName2 = {
  (EFI_COMPONENT_NAME2_GET_DRIVER_NAME)     &VirtioRngGetDriverName,
  (EFI_COMPONENT_NAME2_GET_CONTROLLER_NAME) &VirtioRngGetDeviceName,
  "en" // SupportedLanguages, RFC 4646 language codes
};


//
// Entry point of this driver.
//
EFI_STATUS
EFIAPI
VirtioRngEntryPoint (
  IN EFI_HANDLE       ImageHandle,
  IN EFI_SYSTEM_TABLE *SystemTable
  )
{
  return EfiLibInstallDriverBindingComponentName2 (
           ImageHandle,
           SystemTable,
           &gDriverBinding,
           ImageHandle,
           &gComponentName,
           &gComponentName2
           );
}