Helpers.c

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#include <Library/BaseLib.h>             // StrLen()
#include <Library/BaseMemoryLib.h>       // CopyMem()
#include <Library/MemoryAllocationLib.h> // AllocatePool()
#include <Library/TimeBaseLib.h>         // EpochToEfiTime()
#include <Library/VirtioLib.h>           // Virtio10WriteFeatures()
 
#include "VirtioFsDxe.h"
 
STATIC
EFI_STATUS
VirtioFsReadConfig (
  IN  VIRTIO_DEVICE_PROTOCOL  *Virtio,
  OUT VIRTIO_FS_CONFIG        *Config
  )
{
  UINTN       Idx;
  EFI_STATUS  Status;
 
  for (Idx = 0; Idx < VIRTIO_FS_TAG_BYTES; Idx++) {
    Status = Virtio->ReadDevice (
                       Virtio,                                 // This
                       OFFSET_OF (VIRTIO_FS_CONFIG, Tag[Idx]), // FieldOffset
                       sizeof Config->Tag[Idx],                // FieldSize
                       sizeof Config->Tag[Idx],                // BufferSize
                       &Config->Tag[Idx]                       // Buffer
                       );
    if (EFI_ERROR (Status)) {
      return Status;
    }
  }
 
  Status = Virtio->ReadDevice (
                     Virtio,                                     // This
                     OFFSET_OF (VIRTIO_FS_CONFIG, NumReqQueues), // FieldOffset
                     sizeof Config->NumReqQueues,                // FieldSize
                     sizeof Config->NumReqQueues,                // BufferSize
                     &Config->NumReqQueues                       // Buffer
                     );
  return Status;
}
 
EFI_STATUS
VirtioFsInit (
  IN OUT VIRTIO_FS  *VirtioFs
  )
{
  UINT8             NextDevStat;
  EFI_STATUS        Status;
  UINT64            Features;
  VIRTIO_FS_CONFIG  Config;
  UINTN             Idx;
  UINT64            RingBaseShift;
 
  //
  // Execute virtio-v1.1-cs01-87fa6b5d8155, 3.1.1 Driver Requirements: Device
  // Initialization.
  //
  // 1. Reset the device.
  //
  NextDevStat = 0;
  Status      = VirtioFs->Virtio->SetDeviceStatus (VirtioFs->Virtio, NextDevStat);
  if (EFI_ERROR (Status)) {
    goto Failed;
  }
 
  //
  // 2. Set the ACKNOWLEDGE status bit [...]
  //
  NextDevStat |= VSTAT_ACK;
  Status       = VirtioFs->Virtio->SetDeviceStatus (VirtioFs->Virtio, NextDevStat);
  if (EFI_ERROR (Status)) {
    goto Failed;
  }
 
  //
  // 3. Set the DRIVER status bit [...]
  //
  NextDevStat |= VSTAT_DRIVER;
  Status       = VirtioFs->Virtio->SetDeviceStatus (VirtioFs->Virtio, NextDevStat);
  if (EFI_ERROR (Status)) {
    goto Failed;
  }
 
  //
  // 4. Read device feature bits...
  //
  Status = VirtioFs->Virtio->GetDeviceFeatures (VirtioFs->Virtio, &Features);
  if (EFI_ERROR (Status)) {
    goto Failed;
  }
 
  if ((Features & VIRTIO_F_VERSION_1) == 0) {
    Status = EFI_UNSUPPORTED;
    goto Failed;
  }
 
  //
  // No device-specific feature bits have been defined in file "virtio-fs.tex"
  // of the virtio spec at <https://github.com/oasis-tcs/virtio-spec.git>, as
  // of commit 87fa6b5d8155.
  //
  Features &= VIRTIO_F_VERSION_1 | VIRTIO_F_IOMMU_PLATFORM;
 
  //
  // ... and write the subset of feature bits understood by the [...] driver to
  // the device. [...]
  // 5. Set the FEATURES_OK status bit.
  // 6. Re-read device status to ensure the FEATURES_OK bit is still set [...]
  //
  Status = Virtio10WriteFeatures (VirtioFs->Virtio, Features, &NextDevStat);
  if (EFI_ERROR (Status)) {
    goto Failed;
  }
 
  //
  // 7. Perform device-specific setup, including discovery of virtqueues for
  // the device, [...] reading [...] the device's virtio configuration space
  //
  Status = VirtioFsReadConfig (VirtioFs->Virtio, &Config);
  if (EFI_ERROR (Status)) {
    goto Failed;
  }
 
  //
  // 7.a. Convert the filesystem label from UTF-8 to UCS-2. Only labels with
  // printable ASCII code points (U+0020 through U+007E) are supported.
  // NUL-terminate at either the terminator we find, or right after the
  // original label.
  //
  for (Idx = 0; Idx < VIRTIO_FS_TAG_BYTES && Config.Tag[Idx] != '\0'; Idx++) {
    if ((Config.Tag[Idx] < 0x20) || (Config.Tag[Idx] > 0x7E)) {
      Status = EFI_UNSUPPORTED;
      goto Failed;
    }
 
    VirtioFs->Label[Idx] = Config.Tag[Idx];
  }
 
  VirtioFs->Label[Idx] = L'\0';
 
  //
  // 7.b. We need one queue for sending normal priority requests.
  //
  if (Config.NumReqQueues < 1) {
    Status = EFI_UNSUPPORTED;
    goto Failed;
  }
 
  //
  // 7.c. Fetch and remember the number of descriptors we can place on the
  // queue at once. We'll need two descriptors per request, as a minimum --
  // request header, response header.
  //
  Status = VirtioFs->Virtio->SetQueueSel (
                               VirtioFs->Virtio,
                               VIRTIO_FS_REQUEST_QUEUE
                               );
  if (EFI_ERROR (Status)) {
    goto Failed;
  }
 
  Status = VirtioFs->Virtio->GetQueueNumMax (
                               VirtioFs->Virtio,
                               &VirtioFs->QueueSize
                               );
  if (EFI_ERROR (Status)) {
    goto Failed;
  }
 
  if (VirtioFs->QueueSize < 2) {
    Status = EFI_UNSUPPORTED;
    goto Failed;
  }
 
  //
  // 7.d. [...] population of virtqueues [...]
  //
  Status = VirtioRingInit (
             VirtioFs->Virtio,
             VirtioFs->QueueSize,
             &VirtioFs->Ring
             );
  if (EFI_ERROR (Status)) {
    goto Failed;
  }
 
  Status = VirtioRingMap (
             VirtioFs->Virtio,
             &VirtioFs->Ring,
             &RingBaseShift,
             &VirtioFs->RingMap
             );
  if (EFI_ERROR (Status)) {
    goto ReleaseQueue;
  }
 
  Status = VirtioFs->Virtio->SetQueueAddress (
                               VirtioFs->Virtio,
                               &VirtioFs->Ring,
                               RingBaseShift
                               );
  if (EFI_ERROR (Status)) {
    goto UnmapQueue;
  }
 
  //
  // 8. Set the DRIVER_OK status bit.
  //
  NextDevStat |= VSTAT_DRIVER_OK;
  Status       = VirtioFs->Virtio->SetDeviceStatus (VirtioFs->Virtio, NextDevStat);
  if (EFI_ERROR (Status)) {
    goto UnmapQueue;
  }
 
  return EFI_SUCCESS;
 
UnmapQueue:
  VirtioFs->Virtio->UnmapSharedBuffer (VirtioFs->Virtio, VirtioFs->RingMap);
 
ReleaseQueue:
  VirtioRingUninit (VirtioFs->Virtio, &VirtioFs->Ring);
 
Failed:
  //
  // If any of these steps go irrecoverably wrong, the driver SHOULD set the
  // FAILED status bit to indicate that it has given up on the device (it can
  // reset the device later to restart if desired). [...]
  //
  // Virtio access failure here should not mask the original error.
  //
  NextDevStat |= VSTAT_FAILED;
  VirtioFs->Virtio->SetDeviceStatus (VirtioFs->Virtio, NextDevStat);
 
  return Status;
}
 
VOID
VirtioFsUninit (
  IN OUT VIRTIO_FS  *VirtioFs
  )
{
  //
  // Resetting the Virtio device makes it release its resources and forget its
  // configuration.
  //
  VirtioFs->Virtio->SetDeviceStatus (VirtioFs->Virtio, 0);
  VirtioFs->Virtio->UnmapSharedBuffer (VirtioFs->Virtio, VirtioFs->RingMap);
  VirtioRingUninit (VirtioFs->Virtio, &VirtioFs->Ring);
}
 
VOID
EFIAPI
VirtioFsExitBoot (
  IN EFI_EVENT  ExitBootEvent,
  IN VOID       *VirtioFsAsVoid
  )
{
  VIRTIO_FS  *VirtioFs;
 
  VirtioFs = VirtioFsAsVoid;
  DEBUG ((
    DEBUG_VERBOSE,
    "%a: VirtioFs=0x%p Label=\"%s\"\n",
    __func__,
    VirtioFsAsVoid,
    VirtioFs->Label
    ));
  VirtioFs->Virtio->SetDeviceStatus (VirtioFs->Virtio, 0);
}
 
EFI_STATUS
VirtioFsSgListsValidate (
  IN     VIRTIO_FS                      *VirtioFs,
  IN OUT VIRTIO_FS_SCATTER_GATHER_LIST  *RequestSgList,
  IN OUT VIRTIO_FS_SCATTER_GATHER_LIST  *ResponseSgList OPTIONAL
  )
{
  VIRTIO_FS_SCATTER_GATHER_LIST  *SgListParam[2];
  UINT16                         DescriptorsNeeded;
  UINTN                          ListId;
 
  if (RequestSgList == NULL) {
    return EFI_INVALID_PARAMETER;
  }
 
  SgListParam[0] = RequestSgList;
  SgListParam[1] = ResponseSgList;
 
  DescriptorsNeeded = 0;
  for (ListId = 0; ListId < ARRAY_SIZE (SgListParam); ListId++) {
    VIRTIO_FS_SCATTER_GATHER_LIST  *SgList;
    UINT32                         SgListTotalSize;
    UINTN                          IoVecIdx;
 
    SgList = SgListParam[ListId];
    if (SgList == NULL) {
      continue;
    }
 
    //
    // Sanity-check SgList -- it must provide at least one IO Vector.
    //
    if ((SgList->IoVec == NULL) || (SgList->NumVec == 0)) {
      return EFI_INVALID_PARAMETER;
    }
 
    //
    // Make sure that, for each IO Vector in this SgList, a virtio descriptor
    // can be added to the virtio queue, after the other descriptors added
    // previously.
    //
    if ((SgList->NumVec > (UINTN)(MAX_UINT16 - DescriptorsNeeded)) ||
        (DescriptorsNeeded + SgList->NumVec > VirtioFs->QueueSize))
    {
      return EFI_UNSUPPORTED;
    }
 
    DescriptorsNeeded += (UINT16)SgList->NumVec;
 
    SgListTotalSize = 0;
    for (IoVecIdx = 0; IoVecIdx < SgList->NumVec; IoVecIdx++) {
      VIRTIO_FS_IO_VECTOR  *IoVec;
 
      IoVec = &SgList->IoVec[IoVecIdx];
      //
      // Sanity-check this IoVec -- it must describe a non-empty buffer.
      //
      if ((IoVec->Buffer == NULL) || (IoVec->Size == 0)) {
        return EFI_INVALID_PARAMETER;
      }
 
      //
      // Make sure the cumulative size of all IO Vectors in this SgList remains
      // expressible as a UINT32.
      //
      if (IoVec->Size > MAX_UINT32 - SgListTotalSize) {
        return EFI_UNSUPPORTED;
      }
 
      SgListTotalSize += (UINT32)IoVec->Size;
 
      //
      // Initialize those fields in this IO Vector that will be updated in
      // relation to mapping / transfer.
      //
      IoVec->Mapped        = FALSE;
      IoVec->MappedAddress = 0;
      IoVec->Mapping       = NULL;
      IoVec->Transferred   = 0;
    }
 
    //
    // Store the cumulative size of all IO Vectors that we have calculated in
    // this SgList.
    //
    SgList->TotalSize = SgListTotalSize;
  }
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
VirtioFsSgListsSubmit (
  IN OUT VIRTIO_FS                      *VirtioFs,
  IN OUT VIRTIO_FS_SCATTER_GATHER_LIST  *RequestSgList,
  IN OUT VIRTIO_FS_SCATTER_GATHER_LIST  *ResponseSgList OPTIONAL
  )
{
  VIRTIO_FS_SCATTER_GATHER_LIST  *SgListParam[2];
  VIRTIO_MAP_OPERATION           SgListVirtioMapOp[ARRAY_SIZE (SgListParam)];
  UINT16                         SgListDescriptorFlag[ARRAY_SIZE (SgListParam)];
  UINTN                          ListId;
  VIRTIO_FS_SCATTER_GATHER_LIST  *SgList;
  UINTN                          IoVecIdx;
  VIRTIO_FS_IO_VECTOR            *IoVec;
  EFI_STATUS                     Status;
  DESC_INDICES                   Indices;
  UINT32                         TotalBytesWrittenByDevice;
  UINT32                         BytesPermittedForWrite;
 
  SgListParam[0]          = RequestSgList;
  SgListVirtioMapOp[0]    = VirtioOperationBusMasterRead;
  SgListDescriptorFlag[0] = 0;
 
  SgListParam[1]          = ResponseSgList;
  SgListVirtioMapOp[1]    = VirtioOperationBusMasterWrite;
  SgListDescriptorFlag[1] = VRING_DESC_F_WRITE;
 
  //
  // Map all IO Vectors.
  //
  for (ListId = 0; ListId < ARRAY_SIZE (SgListParam); ListId++) {
    SgList = SgListParam[ListId];
    if (SgList == NULL) {
      continue;
    }
 
    for (IoVecIdx = 0; IoVecIdx < SgList->NumVec; IoVecIdx++) {
      IoVec = &SgList->IoVec[IoVecIdx];
      //
      // Map this IO Vector.
      //
      Status = VirtioMapAllBytesInSharedBuffer (
                 VirtioFs->Virtio,
                 SgListVirtioMapOp[ListId],
                 IoVec->Buffer,
                 IoVec->Size,
                 &IoVec->MappedAddress,
                 &IoVec->Mapping
                 );
      if (EFI_ERROR (Status)) {
        goto Unmap;
      }
 
      IoVec->Mapped = TRUE;
    }
  }
 
  //
  // Compose the descriptor chain.
  //
  VirtioPrepare (&VirtioFs->Ring, &Indices);
  for (ListId = 0; ListId < ARRAY_SIZE (SgListParam); ListId++) {
    SgList = SgListParam[ListId];
    if (SgList == NULL) {
      continue;
    }
 
    for (IoVecIdx = 0; IoVecIdx < SgList->NumVec; IoVecIdx++) {
      UINT16  NextFlag;
 
      IoVec = &SgList->IoVec[IoVecIdx];
      //
      // Set VRING_DESC_F_NEXT on all except the very last descriptor.
      //
      NextFlag = VRING_DESC_F_NEXT;
      if ((ListId == ARRAY_SIZE (SgListParam) - 1) &&
          (IoVecIdx == SgList->NumVec - 1))
      {
        NextFlag = 0;
      }
 
      VirtioAppendDesc (
        &VirtioFs->Ring,
        IoVec->MappedAddress,
        (UINT32)IoVec->Size,
        SgListDescriptorFlag[ListId] | NextFlag,
        &Indices
        );
    }
  }
 
  //
  // Submit the descriptor chain.
  //
  Status = VirtioFlush (
             VirtioFs->Virtio,
             VIRTIO_FS_REQUEST_QUEUE,
             &VirtioFs->Ring,
             &Indices,
             &TotalBytesWrittenByDevice
             );
  if (EFI_ERROR (Status)) {
    goto Unmap;
  }
 
  //
  // Sanity-check: the Virtio Filesystem device should not have written more
  // bytes than what we offered buffers for.
  //
  if (ResponseSgList == NULL) {
    BytesPermittedForWrite = 0;
  } else {
    BytesPermittedForWrite = ResponseSgList->TotalSize;
  }
 
  if (TotalBytesWrittenByDevice > BytesPermittedForWrite) {
    Status = EFI_DEVICE_ERROR;
    goto Unmap;
  }
 
  //
  // Update the transfer sizes in the IO Vectors.
  //
  for (ListId = 0; ListId < ARRAY_SIZE (SgListParam); ListId++) {
    SgList = SgListParam[ListId];
    if (SgList == NULL) {
      continue;
    }
 
    for (IoVecIdx = 0; IoVecIdx < SgList->NumVec; IoVecIdx++) {
      IoVec = &SgList->IoVec[IoVecIdx];
      if (SgListVirtioMapOp[ListId] == VirtioOperationBusMasterRead) {
        //
        // We report that the Virtio Filesystem device has read all buffers in
        // the request.
        //
        IoVec->Transferred = IoVec->Size;
      } else {
        //
        // Regarding the response, calculate how much of the current IO Vector
        // has been populated by the Virtio Filesystem device. In
        // "TotalBytesWrittenByDevice", VirtioFlush() reported the total count
        // across all device-writeable descriptors, in the order they were
        // chained on the ring.
        //
        IoVec->Transferred = MIN (
                               (UINTN)TotalBytesWrittenByDevice,
                               IoVec->Size
                               );
        TotalBytesWrittenByDevice -= (UINT32)IoVec->Transferred;
      }
    }
  }
 
  //
  // By now, "TotalBytesWrittenByDevice" has been exhausted.
  //
  ASSERT (TotalBytesWrittenByDevice == 0);
 
  //
  // We've succeeded; fall through.
  //
Unmap:
  //
  // Unmap all mapped IO Vectors on both the success and the error paths. The
  // unmapping occurs in reverse order of mapping, in an attempt to avoid
  // memory fragmentation.
  //
  ListId = ARRAY_SIZE (SgListParam);
  while (ListId > 0) {
    --ListId;
    SgList = SgListParam[ListId];
    if (SgList == NULL) {
      continue;
    }
 
    IoVecIdx = SgList->NumVec;
    while (IoVecIdx > 0) {
      EFI_STATUS  UnmapStatus;
 
      --IoVecIdx;
      IoVec = &SgList->IoVec[IoVecIdx];
      //
      // Unmap this IO Vector, if it has been mapped.
      //
      if (!IoVec->Mapped) {
        continue;
      }
 
      UnmapStatus = VirtioFs->Virtio->UnmapSharedBuffer (
                                        VirtioFs->Virtio,
                                        IoVec->Mapping
                                        );
      //
      // Re-set the following fields to the values they initially got from
      // VirtioFsSgListsValidate() -- the above unmapping attempt is considered
      // final, even if it fails.
      //
      IoVec->Mapped        = FALSE;
      IoVec->MappedAddress = 0;
      IoVec->Mapping       = NULL;
 
      //
      // If we are on the success path, but the unmapping failed, we need to
      // transparently flip to the failure path -- the caller must learn they
      // should not consult the response buffers.
      //
      // The branch below can be taken at most once.
      //
      if (!EFI_ERROR (Status) && EFI_ERROR (UnmapStatus)) {
        Status = UnmapStatus;
      }
    }
  }
 
  return Status;
}
 
EFI_STATUS
VirtioFsFuseNewRequest (
  IN OUT VIRTIO_FS              *VirtioFs,
  OUT VIRTIO_FS_FUSE_REQUEST    *Request,
  IN     UINT32                 RequestSize,
  IN     VIRTIO_FS_FUSE_OPCODE  Opcode,
  IN     UINT64                 NodeId
  )
{
  if (RequestSize < sizeof *Request) {
    return EFI_INVALID_PARAMETER;
  }
 
  if (VirtioFs->RequestId == MAX_UINT64) {
    return EFI_OUT_OF_RESOURCES;
  }
 
  Request->Len     = RequestSize;
  Request->Opcode  = Opcode;
  Request->Unique  = VirtioFs->RequestId++;
  Request->NodeId  = NodeId;
  Request->Uid     = 0;
  Request->Gid     = 0;
  Request->Pid     = 1;
  Request->Padding = 0;
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
VirtioFsFuseCheckResponse (
  IN  VIRTIO_FS_SCATTER_GATHER_LIST  *ResponseSgList,
  IN  UINT64                         RequestId,
  OUT UINTN                          *TailBufferFill
  )
{
  UINTN                    NumFixedSizeVec;
  VIRTIO_FS_FUSE_RESPONSE  *CommonResp;
  UINT32                   TotalTransferred;
  UINTN                    Idx;
 
  //
  // Ensured by VirtioFsSgListsValidate().
  //
  ASSERT (ResponseSgList->NumVec > 0);
 
  if (TailBufferFill == NULL) {
    //
    // All buffers are considered fixed size.
    //
    NumFixedSizeVec = ResponseSgList->NumVec;
  } else {
    //
    // If the last buffer is variable size, then we need that buffer to be
    // different from the first buffer, which is considered a
    // VIRTIO_FS_FUSE_RESPONSE (fixed size) structure.
    //
    if (ResponseSgList->NumVec == 1) {
      return EFI_INVALID_PARAMETER;
    }
 
    NumFixedSizeVec = ResponseSgList->NumVec - 1;
  }
 
  //
  // The first buffer is supposed to carry a (fully populated)
  // VIRTIO_FS_FUSE_RESPONSE structure.
  //
  if (ResponseSgList->IoVec[0].Size != sizeof *CommonResp) {
    return EFI_INVALID_PARAMETER;
  }
 
  if (ResponseSgList->IoVec[0].Transferred != ResponseSgList->IoVec[0].Size) {
    return EFI_PROTOCOL_ERROR;
  }
 
  //
  // FUSE must report the same number of bytes, written by the Virtio
  // Filesystem device, as the virtio transport does.
  //
  CommonResp       = ResponseSgList->IoVec[0].Buffer;
  TotalTransferred = 0;
  for (Idx = 0; Idx < ResponseSgList->NumVec; Idx++) {
    //
    // Integer overflow and truncation are not possible, based on
    // VirtioFsSgListsValidate() and VirtioFsSgListsSubmit().
    //
    TotalTransferred += (UINT32)ResponseSgList->IoVec[Idx].Transferred;
  }
 
  if (CommonResp->Len != TotalTransferred) {
    return EFI_PROTOCOL_ERROR;
  }
 
  //
  // Enforce that FUSE match our request ID in the response.
  //
  if (CommonResp->Unique != RequestId) {
    return EFI_PROTOCOL_ERROR;
  }
 
  //
  // If there is an explicit error report, skip checking the transfer
  // counts for the rest of the fixed size buffers.
  //
  if (CommonResp->Error != 0) {
    return EFI_DEVICE_ERROR;
  }
 
  //
  // There was no error reported, so we require that the Virtio Filesystem
  // device populate all fixed size buffers. We checked this for the very first
  // buffer above; let's check the rest (if any).
  //
  ASSERT (NumFixedSizeVec >= 1);
  for (Idx = 1; Idx < NumFixedSizeVec; Idx++) {
    if (ResponseSgList->IoVec[Idx].Transferred !=
        ResponseSgList->IoVec[Idx].Size)
    {
      return EFI_PROTOCOL_ERROR;
    }
  }
 
  //
  // If the last buffer is considered variable size, report its filled size.
  //
  if (TailBufferFill != NULL) {
    *TailBufferFill = ResponseSgList->IoVec[NumFixedSizeVec].Transferred;
  }
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
VirtioFsErrnoToEfiStatus (
  IN INT32  Errno
  )
{
  switch (Errno) {
    case   -1:// EPERM               Operation not permitted
      return EFI_SECURITY_VIOLATION;
 
    case   -2: // ENOENT              No such file or directory
    case   -3: // ESRCH               No such process
    case   -6: // ENXIO               No such device or address
    case  -10: // ECHILD              No child processes
    case  -19: // ENODEV              No such device
    case  -49: // EUNATCH             Protocol driver not attached
    case  -65: // ENOPKG              Package not installed
    case  -79: // ELIBACC             Can not access a needed shared library
    case -126: // ENOKEY              Required key not available
      return EFI_NOT_FOUND;
 
    case   -4: // EINTR               Interrupted system call
    case  -11: // EAGAIN, EWOULDBLOCK Resource temporarily unavailable
    case  -16: // EBUSY               Device or resource busy
    case  -26: // ETXTBSY             Text file busy
    case  -35: // EDEADLK, EDEADLOCK  Resource deadlock avoided
    case  -39: // ENOTEMPTY           Directory not empty
    case  -42: // ENOMSG              No message of desired type
    case  -61: // ENODATA             No data available
    case  -85: // ERESTART            Interrupted system call should be restarted
      return EFI_NOT_READY;
 
    case   -5: // EIO                 Input/output error
    case  -45: // EL2NSYNC            Level 2 not synchronized
    case  -46: // EL3HLT              Level 3 halted
    case  -47: // EL3RST              Level 3 reset
    case  -51: // EL2HLT              Level 2 halted
    case -121: // EREMOTEIO           Remote I/O error
    case -133: // EHWPOISON           Memory page has hardware error
      return EFI_DEVICE_ERROR;
 
    case   -7: // E2BIG               Argument list too long
    case  -36: // ENAMETOOLONG        File name too long
    case  -90: // EMSGSIZE            Message too long
      return EFI_BAD_BUFFER_SIZE;
 
    case   -8: // ENOEXEC             Exec format error
    case  -15: // ENOTBLK             Block device required
    case  -18: // EXDEV               Invalid cross-device link
    case  -20: // ENOTDIR             Not a directory
    case  -21: // EISDIR              Is a directory
    case  -25: // ENOTTY              Inappropriate ioctl for device
    case  -27: // EFBIG               File too large
    case  -29: // ESPIPE              Illegal seek
    case  -38: // ENOSYS              Function not implemented
    case  -59: // EBFONT              Bad font file format
    case  -60: // ENOSTR              Device not a stream
    case  -83: // ELIBEXEC            Cannot exec a shared library directly
    case  -88: // ENOTSOCK            Socket operation on non-socket
    case  -91: // EPROTOTYPE          Protocol wrong type for socket
    case  -92: // ENOPROTOOPT         Protocol not available
    case  -93: // EPROTONOSUPPORT     Protocol not supported
    case  -94: // ESOCKTNOSUPPORT     Socket type not supported
    case  -95: // ENOTSUP, EOPNOTSUPP Operation not supported
    case  -96: // EPFNOSUPPORT        Protocol family not supported
    case  -97: // EAFNOSUPPORT        Address family not supported by protocol
    case  -99: // EADDRNOTAVAIL       Cannot assign requested address
    case -118: // ENOTNAM             Not a XENIX named type file
    case -120: // EISNAM              Is a named type file
    case -124: // EMEDIUMTYPE         Wrong medium type
      return EFI_UNSUPPORTED;
 
    case   -9: // EBADF               Bad file descriptor
    case  -14: // EFAULT              Bad address
    case  -44: // ECHRNG              Channel number out of range
    case  -48: // ELNRNG              Link number out of range
    case  -53: // EBADR               Invalid request descriptor
    case  -56: // EBADRQC             Invalid request code
    case  -57: // EBADSLT             Invalid slot
    case  -76: // ENOTUNIQ            Name not unique on network
    case  -84: // EILSEQ        Invalid or incomplete multibyte or wide character
      return EFI_NO_MAPPING;
 
    case  -12: // ENOMEM              Cannot allocate memory
    case  -23: // ENFILE              Too many open files in system
    case  -24: // EMFILE              Too many open files
    case  -31: // EMLINK              Too many links
    case  -37: // ENOLCK              No locks available
    case  -40: // ELOOP               Too many levels of symbolic links
    case  -50: // ENOCSI              No CSI structure available
    case  -55: // ENOANO              No anode
    case  -63: // ENOSR               Out of streams resources
    case  -82: // ELIBMAX         Attempting to link in too many shared libraries
    case  -87: // EUSERS              Too many users
    case -105: // ENOBUFS             No buffer space available
    case -109: // ETOOMANYREFS        Too many references: cannot splice
    case -119: // ENAVAIL             No XENIX semaphores available
    case -122: // EDQUOT              Disk quota exceeded
      return EFI_OUT_OF_RESOURCES;
 
    case  -13:// EACCES              Permission denied
      return EFI_ACCESS_DENIED;
 
    case  -17: // EEXIST              File exists
    case  -98: // EADDRINUSE          Address already in use
    case -106: // EISCONN             Transport endpoint is already connected
    case -114: // EALREADY            Operation already in progress
    case -115: // EINPROGRESS         Operation now in progress
      return EFI_ALREADY_STARTED;
 
    case  -22: // EINVAL              Invalid argument
    case  -33: // EDOM                Numerical argument out of domain
      return EFI_INVALID_PARAMETER;
 
    case  -28: // ENOSPC              No space left on device
    case  -54: // EXFULL              Exchange full
      return EFI_VOLUME_FULL;
 
    case  -30:// EROFS               Read-only file system
      return EFI_WRITE_PROTECTED;
 
    case  -32: // EPIPE               Broken pipe
    case  -43: // EIDRM               Identifier removed
    case  -67: // ENOLINK             Link has been severed
    case  -68: // EADV                Advertise error
    case  -69: // ESRMNT              Srmount error
    case  -70: // ECOMM               Communication error on send
    case  -73: // EDOTDOT             RFS specific error
    case  -78: // EREMCHG             Remote address changed
    case  -86: // ESTRPIPE            Streams pipe error
    case -102: // ENETRESET           Network dropped connection on reset
    case -103: // ECONNABORTED        Software caused connection abort
    case -104: // ECONNRESET          Connection reset by peer
    case -116: // ESTALE              Stale file handle
    case -125: // ECANCELED           Operation canceled
    case -128: // EKEYREVOKED         Key has been revoked
    case -129: // EKEYREJECTED        Key was rejected by service
    case -130: // EOWNERDEAD          Owner died
    case -131: // ENOTRECOVERABLE     State not recoverable
      return EFI_ABORTED;
 
    case  -34: // ERANGE              Numerical result out of range
    case  -75: // EOVERFLOW           Value too large for defined data type
      return EFI_BUFFER_TOO_SMALL;
 
    case  -52: // EBADE               Invalid exchange
    case -108: // ESHUTDOWN         Cannot send after transport endpoint shutdown
    case -111: // ECONNREFUSED        Connection refused
      return EFI_END_OF_FILE;
 
    case  -62: // ETIME               Timer expired
    case -110: // ETIMEDOUT           Connection timed out
    case -127: // EKEYEXPIRED         Key has expired
      return EFI_TIMEOUT;
 
    case  -64: // ENONET              Machine is not on the network
    case  -66: // EREMOTE             Object is remote
    case  -72: // EMULTIHOP           Multihop attempted
    case -100: // ENETDOWN            Network is down
    case -101: // ENETUNREACH         Network is unreachable
    case -112: // EHOSTDOWN           Host is down
    case -113: // EHOSTUNREACH        No route to host
    case -123: // ENOMEDIUM           No medium found
    case -132: // ERFKILL             Operation not possible due to RF-kill
      return EFI_NO_MEDIA;
 
    case  -71:// EPROTO              Protocol error
      return EFI_PROTOCOL_ERROR;
 
    case  -74: // EBADMSG             Bad message
    case  -77: // EBADFD              File descriptor in bad state
    case  -80: // ELIBBAD             Accessing a corrupted shared library
    case  -81: // ELIBSCN             .lib section in a.out corrupted
    case -117: // EUCLEAN             Structure needs cleaning
      return EFI_VOLUME_CORRUPTED;
 
    case  -89: // EDESTADDRREQ        Destination address required
    case -107: // ENOTCONN            Transport endpoint is not connected
      return EFI_NOT_STARTED;
 
    default:
      break;
  }
 
  return EFI_DEVICE_ERROR;
}
 
//
// Parser states for canonicalizing a POSIX pathname.
//
typedef enum {
  ParserInit,   // just starting
  ParserEnd,    // finished
  ParserSlash,  // slash(es) seen
  ParserDot,    // one dot seen since last slash
  ParserDotDot, // two dots seen since last slash
  ParserNormal, // a different sequence seen
} PARSER_STATE;
 
STATIC
VOID
ParserStripSlash (
  IN     CHAR8  *Buffer,
  IN OUT UINTN  *Position
  )
{
  ASSERT (*Position >= 1);
  ASSERT (Buffer[*Position - 1] == '/');
  if (*Position == 1) {
    return;
  }
 
  (*Position)--;
}
 
STATIC
VOID
ParserCopy (
  OUT CHAR8     *Buffer,
  IN OUT UINTN  *Position,
  IN     UINTN  Size,
  IN     CHAR8  Char8
  )
{
  ASSERT (*Position < Size);
  Buffer[(*Position)++] = Char8;
}
 
STATIC
VOID
ParserRewindDot (
  IN     CHAR8  *Buffer,
  IN OUT UINTN  *Position
  )
{
  ASSERT (*Position >= 2);
  ASSERT (Buffer[*Position - 1] == '.');
  ASSERT (Buffer[*Position - 2] == '/');
  (*Position)--;
}
 
STATIC
VOID
ParserRewindDotDot (
  IN     CHAR8  *Buffer,
  IN OUT UINTN  *Position,
  OUT BOOLEAN   *RootEscape
 
  )
{
  ASSERT (*Position >= 3);
  ASSERT (Buffer[*Position - 1] == '.');
  ASSERT (Buffer[*Position - 2] == '.');
  ASSERT (Buffer[*Position - 3] == '/');
  (*Position) -= 2;
 
  if (*Position == 1) {
    //
    // Root directory slash reached; don't try to climb higher.
    //
    *RootEscape = TRUE;
    return;
  }
 
  //
  // Skip slash.
  //
  (*Position)--;
  //
  // Scan until next slash to the left.
  //
  do {
    ASSERT (*Position > 0);
    (*Position)--;
  } while (Buffer[*Position] != '/');
 
  (*Position)++;
}
 
EFI_STATUS
VirtioFsAppendPath (
  IN     CHAR8   *LhsPath8,
  IN     CHAR16  *RhsPath16,
  OUT CHAR8      **ResultPath8,
  OUT BOOLEAN    *RootEscape
  )
{
  UINTN         RhsLen;
  CHAR8         *RhsPath8;
  UINTN         Idx;
  EFI_STATUS    Status;
  UINTN         SizeToSanitize;
  CHAR8         *BufferToSanitize;
  CHAR8         *SanitizedBuffer;
  PARSER_STATE  State;
  UINTN         SanitizedPosition;
 
  //
  // Appending an empty pathname is not allowed.
  //
  RhsLen = StrLen (RhsPath16);
  if (RhsLen == 0) {
    return EFI_INVALID_PARAMETER;
  }
 
  //
  // Enforce length restriction on RhsPath16.
  //
  if (RhsLen > VIRTIO_FS_MAX_PATHNAME_LENGTH) {
    return EFI_INVALID_PARAMETER;
  }
 
  //
  // Transliterate RhsPath16 to RhsPath8 by:
  // - rejecting RhsPath16 if a character outside of printable ASCII is seen,
  // - rejecting RhsPath16 if a forward slash is seen,
  // - replacing backslashes with forward slashes,
  // - casting the characters from CHAR16 to CHAR8.
  //
  RhsPath8 = AllocatePool (RhsLen + 1);
  if (RhsPath8 == NULL) {
    return EFI_OUT_OF_RESOURCES;
  }
 
  for (Idx = 0; RhsPath16[Idx] != L'\0'; Idx++) {
    if ((RhsPath16[Idx] < 0x20) || (RhsPath16[Idx] > 0x7E) ||
        (RhsPath16[Idx] == L'/'))
    {
      Status = EFI_UNSUPPORTED;
      goto FreeRhsPath8;
    }
 
    RhsPath8[Idx] = (CHAR8)((RhsPath16[Idx] == L'\\') ? L'/' : RhsPath16[Idx]);
  }
 
  RhsPath8[Idx++] = '\0';
 
  //
  // Now prepare the input for the canonicalization (squashing of sequences of
  // forward slashes, and eliminating . (dot) and .. (dot-dot) pathname
  // components).
  //
  // The sanitized path can never be longer than the naive concatenation of the
  // left hand side and right hand side paths, so we'll use the catenated size
  // for allocating the sanitized output too.
  //
  if (RhsPath8[0] == '/') {
    //
    // If the right hand side path is absolute, then it is not appended to the
    // left hand side path -- it *replaces* the left hand side path.
    //
    SizeToSanitize   = RhsLen + 1;
    BufferToSanitize = RhsPath8;
  } else {
    //
    // If the right hand side path is relative, then it is appended (naively)
    // to the left hand side.
    //
    UINTN  LhsLen;
 
    LhsLen           = AsciiStrLen (LhsPath8);
    SizeToSanitize   = LhsLen + 1 + RhsLen + 1;
    BufferToSanitize = AllocatePool (SizeToSanitize);
    if (BufferToSanitize == NULL) {
      Status = EFI_OUT_OF_RESOURCES;
      goto FreeRhsPath8;
    }
 
    CopyMem (BufferToSanitize, LhsPath8, LhsLen);
    BufferToSanitize[LhsLen] = '/';
    CopyMem (BufferToSanitize + LhsLen + 1, RhsPath8, RhsLen + 1);
  }
 
  //
  // Allocate the output buffer.
  //
  SanitizedBuffer = AllocatePool (SizeToSanitize);
  if (SanitizedBuffer == NULL) {
    Status = EFI_OUT_OF_RESOURCES;
    goto FreeBufferToSanitize;
  }
 
  //
  // State machine for parsing the input and producing the canonical output
  // follows.
  //
  *RootEscape       = FALSE;
  Idx               = 0;
  State             = ParserInit;
  SanitizedPosition = 0;
  do {
    CHAR8  Chr8;
 
    ASSERT (Idx < SizeToSanitize);
    Chr8 = BufferToSanitize[Idx++];
 
    switch (State) {
      case ParserInit: // just starting
        ASSERT (Chr8 == '/');
        ParserCopy (SanitizedBuffer, &SanitizedPosition, SizeToSanitize, Chr8);
        State = ParserSlash;
        break;
 
      case ParserSlash: // slash(es) seen
        switch (Chr8) {
          case '\0':
            ParserStripSlash (SanitizedBuffer, &SanitizedPosition);
            ParserCopy (SanitizedBuffer, &SanitizedPosition, SizeToSanitize, Chr8);
            State = ParserEnd;
            break;
          case '/':
            //
            // skip & stay in same state
            //
            break;
          case '.':
            ParserCopy (SanitizedBuffer, &SanitizedPosition, SizeToSanitize, Chr8);
            State = ParserDot;
            break;
          default:
            ParserCopy (SanitizedBuffer, &SanitizedPosition, SizeToSanitize, Chr8);
            State = ParserNormal;
            break;
        }
 
        break;
 
      case ParserDot: // one dot seen since last slash
        switch (Chr8) {
          case '\0':
            ParserRewindDot (SanitizedBuffer, &SanitizedPosition);
            ParserStripSlash (SanitizedBuffer, &SanitizedPosition);
            ParserCopy (SanitizedBuffer, &SanitizedPosition, SizeToSanitize, Chr8);
            State = ParserEnd;
            break;
          case '/':
            ParserRewindDot (SanitizedBuffer, &SanitizedPosition);
            State = ParserSlash;
            break;
          case '.':
            ParserCopy (SanitizedBuffer, &SanitizedPosition, SizeToSanitize, Chr8);
            State = ParserDotDot;
            break;
          default:
            ParserCopy (SanitizedBuffer, &SanitizedPosition, SizeToSanitize, Chr8);
            State = ParserNormal;
            break;
        }
 
        break;
 
      case ParserDotDot: // two dots seen since last slash
        switch (Chr8) {
          case '\0':
            ParserRewindDotDot (SanitizedBuffer, &SanitizedPosition, RootEscape);
            ParserStripSlash (SanitizedBuffer, &SanitizedPosition);
            ParserCopy (SanitizedBuffer, &SanitizedPosition, SizeToSanitize, Chr8);
            State = ParserEnd;
            break;
          case '/':
            ParserRewindDotDot (SanitizedBuffer, &SanitizedPosition, RootEscape);
            State = ParserSlash;
            break;
          case '.':
          //
          // fall through
          //
          default:
            ParserCopy (SanitizedBuffer, &SanitizedPosition, SizeToSanitize, Chr8);
            State = ParserNormal;
            break;
        }
 
        break;
 
      case ParserNormal: // a different sequence seen
        switch (Chr8) {
          case '\0':
            ParserCopy (SanitizedBuffer, &SanitizedPosition, SizeToSanitize, Chr8);
            State = ParserEnd;
            break;
          case '/':
            ParserCopy (SanitizedBuffer, &SanitizedPosition, SizeToSanitize, Chr8);
            State = ParserSlash;
            break;
          case '.':
          //
          // fall through
          //
          default:
            //
            // copy and stay in same state
            //
            ParserCopy (SanitizedBuffer, &SanitizedPosition, SizeToSanitize, Chr8);
            break;
        }
 
        break;
 
      default:
        ASSERT (FALSE);
        break;
    }
  } while (State != ParserEnd);
 
  //
  // Ensure length invariant on ResultPath8.
  //
  ASSERT (SanitizedPosition >= 2);
  if (SanitizedPosition - 1 > VIRTIO_FS_MAX_PATHNAME_LENGTH) {
    Status = EFI_OUT_OF_RESOURCES;
    goto FreeSanitizedBuffer;
  }
 
  *ResultPath8    = SanitizedBuffer;
  SanitizedBuffer = NULL;
  Status          = EFI_SUCCESS;
  //
  // Fall through.
  //
FreeSanitizedBuffer:
  if (SanitizedBuffer != NULL) {
    FreePool (SanitizedBuffer);
  }
 
FreeBufferToSanitize:
  if (RhsPath8[0] != '/') {
    FreePool (BufferToSanitize);
  }
 
FreeRhsPath8:
  FreePool (RhsPath8);
  return Status;
}
 
EFI_STATUS
VirtioFsLookupMostSpecificParentDir (
  IN OUT VIRTIO_FS  *VirtioFs,
  IN OUT CHAR8      *Path,
  OUT UINT64        *DirNodeId,
  OUT CHAR8         **LastComponent
  )
{
  UINT64      ParentDirNodeId;
  CHAR8       *Slash;
  EFI_STATUS  Status;
  UINT64      NextDirNodeId;
 
  if (AsciiStrCmp (Path, "/") == 0) {
    return EFI_INVALID_PARAMETER;
  }
 
  ParentDirNodeId = VIRTIO_FS_FUSE_ROOT_DIR_NODE_ID;
  Slash           = Path;
  for ( ; ;) {
    CHAR8                               *NextSlash;
    VIRTIO_FS_FUSE_ATTRIBUTES_RESPONSE  FuseAttr;
    EFI_FILE_INFO                       FileInfo;
 
    //
    // Find the slash (if any) that terminates the next pathname component.
    //
    NextSlash = AsciiStrStr (Slash + 1, "/");
    if (NextSlash == NULL) {
      break;
    }
 
    //
    // Temporarily replace the found slash character with a NUL in-place, for
    // easy construction of the single-component filename that we need to look
    // up.
    //
    *NextSlash = '\0';
    Status     = VirtioFsFuseLookup (
                   VirtioFs,
                   ParentDirNodeId,
                   Slash + 1,
                   &NextDirNodeId,
                   &FuseAttr
                   );
    *NextSlash = '/';
 
    //
    // We're done with the directory inode that was the basis for the lookup.
    //
    if (ParentDirNodeId != VIRTIO_FS_FUSE_ROOT_DIR_NODE_ID) {
      VirtioFsFuseForget (VirtioFs, ParentDirNodeId);
    }
 
    //
    // If we couldn't look up the next *non-final* pathname component, bail.
    //
    if (EFI_ERROR (Status)) {
      return Status;
    }
 
    //
    // Lookup successful; now check if the next (non-final) component is a
    // directory. If not, bail.
    //
    Status = VirtioFsFuseAttrToEfiFileInfo (&FuseAttr, &FileInfo);
    if (EFI_ERROR (Status)) {
      goto ForgetNextDirNodeId;
    }
 
    if ((FileInfo.Attribute & EFI_FILE_DIRECTORY) == 0) {
      Status = EFI_ACCESS_DENIED;
      goto ForgetNextDirNodeId;
    }
 
    //
    // Advance.
    //
    ParentDirNodeId = NextDirNodeId;
    Slash           = NextSlash;
  }
 
  //
  // ParentDirNodeId corresponds to the last containing directory. The
  // remaining single-component filename represents a direct child under that
  // directory. Said filename starts at (Slash + 1).
  //
  *DirNodeId     = ParentDirNodeId;
  *LastComponent = Slash + 1;
  return EFI_SUCCESS;
 
ForgetNextDirNodeId:
  VirtioFsFuseForget (VirtioFs, NextDirNodeId);
  return Status;
}
 
EFI_STATUS
VirtioFsGetBasename (
  IN     CHAR8  *Path,
  OUT CHAR16    *Basename     OPTIONAL,
  IN OUT UINTN  *BasenameSize
  )
{
  UINTN  AllocSize;
  UINTN  LastComponent;
  UINTN  Idx;
  UINTN  PathSize;
 
  AllocSize = *BasenameSize;
 
  LastComponent = MAX_UINTN;
  for (Idx = 0; Path[Idx] != '\0'; Idx++) {
    if (Path[Idx] == '/') {
      LastComponent = Idx;
    }
  }
 
  PathSize = Idx + 1;
  ASSERT (LastComponent < MAX_UINTN);
  LastComponent++;
  *BasenameSize = (PathSize - LastComponent) * sizeof Basename[0];
 
  if (*BasenameSize > AllocSize) {
    return EFI_BUFFER_TOO_SMALL;
  }
 
  for (Idx = LastComponent; Idx < PathSize; Idx++) {
    Basename[Idx - LastComponent] = Path[Idx];
  }
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
VirtioFsComposeRenameDestination (
  IN     CHAR8   *LhsPath8,
  IN     CHAR16  *RhsPath16,
  OUT CHAR8      **ResultPath8,
  OUT BOOLEAN    *RootEscape
  )
{
  //
  // Lengths are expressed as numbers of characters (CHAR8 or CHAR16),
  // excluding terminating NULs. Sizes are expressed as byte counts, including
  // the bytes taken up by terminating NULs.
  //
  UINTN       RhsLen;
  UINTN       LhsBasename16Size;
  EFI_STATUS  Status;
  UINTN       LhsBasenameLen;
  UINTN       DestSuffix16Size;
  CHAR16      *DestSuffix16;
  CHAR8       *DestPrefix8;
 
  //
  // An empty destination operand for the rename/move operation is not allowed.
  //
  RhsLen = StrLen (RhsPath16);
  if (RhsLen == 0) {
    return EFI_INVALID_PARAMETER;
  }
 
  //
  // Enforce length restriction on RhsPath16.
  //
  if (RhsLen > VIRTIO_FS_MAX_PATHNAME_LENGTH) {
    return EFI_INVALID_PARAMETER;
  }
 
  //
  // Determine the length of the basename of LhsPath8.
  //
  LhsBasename16Size = 0;
  Status            = VirtioFsGetBasename (LhsPath8, NULL, &LhsBasename16Size);
  ASSERT (Status == EFI_BUFFER_TOO_SMALL);
  ASSERT (LhsBasename16Size >= sizeof (CHAR16));
  ASSERT (LhsBasename16Size % sizeof (CHAR16) == 0);
  LhsBasenameLen = LhsBasename16Size / sizeof (CHAR16) - 1;
  if (LhsBasenameLen == 0) {
    //
    // The root directory cannot be renamed/moved.
    //
    return EFI_INVALID_PARAMETER;
  }
 
  //
  // Resolve the "move into directory" convenience form in RhsPath16.
  //
  if (RhsPath16[RhsLen - 1] == L'\\') {
    //
    // Append the basename of LhsPath8 as a CHAR16 string to RhsPath16.
    //
    DestSuffix16Size = RhsLen * sizeof (CHAR16) + LhsBasename16Size;
    DestSuffix16     = AllocatePool (DestSuffix16Size);
    if (DestSuffix16 == NULL) {
      return EFI_OUT_OF_RESOURCES;
    }
 
    CopyMem (DestSuffix16, RhsPath16, RhsLen * sizeof (CHAR16));
    Status = VirtioFsGetBasename (
               LhsPath8,
               DestSuffix16 + RhsLen,
               &LhsBasename16Size
               );
    ASSERT_EFI_ERROR (Status);
  } else {
    //
    // Just create a copy of RhsPath16.
    //
    DestSuffix16Size = (RhsLen + 1) * sizeof (CHAR16);
    DestSuffix16     = AllocateCopyPool (DestSuffix16Size, RhsPath16);
    if (DestSuffix16 == NULL) {
      return EFI_OUT_OF_RESOURCES;
    }
  }
 
  //
  // If the destination operand is absolute, it will be interpreted relative to
  // the root directory.
  //
  // Otherwise (i.e., if the destination operand is relative), then create the
  // canonical pathname that the destination operand is interpreted relatively
  // to; that is, the canonical pathname of the most specific parent directory
  // found in LhsPath8.
  //
  if (DestSuffix16[0] == L'\\') {
    DestPrefix8 = AllocateCopyPool (sizeof "/", "/");
    if (DestPrefix8 == NULL) {
      Status = EFI_OUT_OF_RESOURCES;
      goto FreeDestSuffix16;
    }
  } else {
    UINTN  LhsLen;
    UINTN  DestPrefixLen;
 
    //
    // Strip the basename of LhsPath8.
    //
    LhsLen = AsciiStrLen (LhsPath8);
    ASSERT (LhsBasenameLen < LhsLen);
    DestPrefixLen = LhsLen - LhsBasenameLen;
    ASSERT (LhsPath8[DestPrefixLen - 1] == '/');
    //
    // If we're not at the root directory, strip the slash too.
    //
    if (DestPrefixLen > 1) {
      DestPrefixLen--;
    }
 
    DestPrefix8 = AllocatePool (DestPrefixLen + 1);
    if (DestPrefix8 == NULL) {
      Status = EFI_OUT_OF_RESOURCES;
      goto FreeDestSuffix16;
    }
 
    CopyMem (DestPrefix8, LhsPath8, DestPrefixLen);
    DestPrefix8[DestPrefixLen] = '\0';
  }
 
  //
  // Now combine DestPrefix8 and DestSuffix16 into the final canonical
  // pathname.
  //
  Status = VirtioFsAppendPath (
             DestPrefix8,
             DestSuffix16,
             ResultPath8,
             RootEscape
             );
 
  FreePool (DestPrefix8);
  //
  // Fall through.
  //
FreeDestSuffix16:
  FreePool (DestSuffix16);
 
  return Status;
}
 
EFI_STATUS
VirtioFsFuseAttrToEfiFileInfo (
  IN     VIRTIO_FS_FUSE_ATTRIBUTES_RESPONSE  *FuseAttr,
  OUT EFI_FILE_INFO                          *FileInfo
  )
{
  UINT64    EpochTime[3];
  EFI_TIME  *ConvertedTime[ARRAY_SIZE (EpochTime)];
  UINTN     Idx;
 
  FileInfo->FileSize = FuseAttr->Size;
 
  //
  // The unit for FuseAttr->Blocks is 512B.
  //
  if (FuseAttr->Blocks >= BIT55) {
    return EFI_UNSUPPORTED;
  }
 
  FileInfo->PhysicalSize = LShiftU64 (FuseAttr->Blocks, 9);
 
  //
  // Convert the timestamps. File creation time is not tracked by the Virtio
  // Filesystem device, so set FileInfo->CreateTime from FuseAttr->Mtime as
  // well.
  //
  EpochTime[0]     = FuseAttr->Mtime;
  EpochTime[1]     = FuseAttr->Atime;
  EpochTime[2]     = FuseAttr->Mtime;
  ConvertedTime[0] = &FileInfo->CreateTime;
  ConvertedTime[1] = &FileInfo->LastAccessTime;
  ConvertedTime[2] = &FileInfo->ModificationTime;
 
  for (Idx = 0; Idx < ARRAY_SIZE (EpochTime); Idx++) {
    //
    // EpochToEfiTime() takes a UINTN for seconds.
    //
    if (EpochTime[Idx] > MAX_UINTN) {
      return EFI_UNSUPPORTED;
    }
 
    //
    // Set the following fields in the converted time: Year, Month, Day, Hour,
    // Minute, Second, Nanosecond.
    //
    EpochToEfiTime ((UINTN)EpochTime[Idx], ConvertedTime[Idx]);
    //
    // The times are all expressed in UTC. Consequently, they are not affected
    // by daylight saving.
    //
    ConvertedTime[Idx]->TimeZone = 0;
    ConvertedTime[Idx]->Daylight = 0;
    //
    // Clear the padding fields.
    //
    ConvertedTime[Idx]->Pad1 = 0;
    ConvertedTime[Idx]->Pad2 = 0;
  }
 
  //
  // Set the attributes.
  //
  switch (FuseAttr->Mode & VIRTIO_FS_FUSE_MODE_TYPE_MASK) {
    case VIRTIO_FS_FUSE_MODE_TYPE_DIR:
      FileInfo->Attribute = EFI_FILE_DIRECTORY;
      break;
    case VIRTIO_FS_FUSE_MODE_TYPE_REG:
      FileInfo->Attribute = 0;
      break;
    default:
      //
      // Other file types are not supported.
      //
      return EFI_UNSUPPORTED;
  }
 
  //
  // Report the regular file or directory as read-only if all classes lack
  // write permission.
  //
  if ((FuseAttr->Mode & (VIRTIO_FS_FUSE_MODE_PERM_WUSR |
                         VIRTIO_FS_FUSE_MODE_PERM_WGRP |
                         VIRTIO_FS_FUSE_MODE_PERM_WOTH)) == 0)
  {
    FileInfo->Attribute |= EFI_FILE_READ_ONLY;
  }
 
  //
  // A hard link count greater than 1 is not supported for regular files.
  //
  if (((FileInfo->Attribute & EFI_FILE_DIRECTORY) == 0) && (FuseAttr->Nlink > 1)) {
    return EFI_UNSUPPORTED;
  }
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
VirtioFsFuseDirentPlusToEfiFileInfo (
  IN     VIRTIO_FS_FUSE_DIRENTPLUS_RESPONSE  *FuseDirent,
  IN OUT EFI_FILE_INFO                       *FileInfo
  )
{
  UINTN   DirentSize;
  UINTN   FileInfoSize;
  UINT8   *DirentName;
  UINT32  Idx;
 
  DirentSize = VIRTIO_FS_FUSE_DIRENTPLUS_RESPONSE_SIZE (FuseDirent->Namelen);
  if (DirentSize == 0) {
    return EFI_INVALID_PARAMETER;
  }
 
  //
  // We're now safe from overflow in the calculation below.
  //
  FileInfoSize = (OFFSET_OF (EFI_FILE_INFO, FileName) +
                  ((UINTN)FuseDirent->Namelen + 1) * sizeof (CHAR16));
  if (FileInfoSize > FileInfo->Size) {
    return EFI_BUFFER_TOO_SMALL;
  }
 
  //
  // Convert the name.
  //
  DirentName = (UINT8 *)(FuseDirent + 1);
  for (Idx = 0; Idx < FuseDirent->Namelen; Idx++) {
    UINT8  NameByte;
 
    NameByte = DirentName[Idx];
    if ((NameByte < 0x20) || (NameByte > 0x7E) ||
        (NameByte == '/') || (NameByte == '\\'))
    {
      return EFI_UNSUPPORTED;
    }
 
    FileInfo->FileName[Idx] = (CHAR16)NameByte;
  }
 
  FileInfo->FileName[Idx++] = L'\0';
  //
  // Set the (possibly reduced) size.
  //
  FileInfo->Size = FileInfoSize;
 
  return EFI_SUCCESS;
}
 
VOID
VirtioFsGetFuseSizeUpdate (
  IN     EFI_FILE_INFO  *Info,
  IN     EFI_FILE_INFO  *NewInfo,
  OUT BOOLEAN           *Update,
  OUT UINT64            *Size
  )
{
  BOOLEAN  IsDirectory;
 
  IsDirectory = (BOOLEAN)((Info->Attribute & EFI_FILE_DIRECTORY) != 0);
 
  if (IsDirectory || (Info->FileSize == NewInfo->FileSize)) {
    *Update = FALSE;
    return;
  }
 
  *Update = TRUE;
  *Size   = NewInfo->FileSize;
}
 
EFI_STATUS
VirtioFsGetFuseTimeUpdates (
  IN     EFI_FILE_INFO  *Info,
  IN     EFI_FILE_INFO  *NewInfo,
  OUT BOOLEAN           *UpdateAtime,
  OUT BOOLEAN           *UpdateMtime,
  OUT UINT64            *Atime,
  OUT UINT64            *Mtime
  )
{
  EFI_TIME               *Time[3];
  EFI_TIME               *NewTime[ARRAY_SIZE (Time)];
  UINTN                  Idx;
  STATIC CONST EFI_TIME  ZeroTime = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
  BOOLEAN                Change[ARRAY_SIZE (Time)];
  UINT64                 Seconds[ARRAY_SIZE (Time)];
 
  Time[0]    = &Info->CreateTime;
  Time[1]    = &Info->LastAccessTime;
  Time[2]    = &Info->ModificationTime;
  NewTime[0] = &NewInfo->CreateTime;
  NewTime[1] = &NewInfo->LastAccessTime;
  NewTime[2] = &NewInfo->ModificationTime;
 
  //
  // Determine which timestamps differ from the current state. (A zero time
  // means "don't update", per UEFI spec.) For each timestamp that's being
  // changed, calculate the seconds since the Epoch.
  //
  for (Idx = 0; Idx < ARRAY_SIZE (Time); Idx++) {
    if ((CompareMem (NewTime[Idx], &ZeroTime, sizeof (EFI_TIME)) == 0) ||
        (CompareMem (NewTime[Idx], Time[Idx], sizeof (EFI_TIME)) == 0))
    {
      Change[Idx] = FALSE;
    } else {
      if (!IsTimeValid (NewTime[Idx])) {
        return EFI_INVALID_PARAMETER;
      }
 
      Change[Idx]  = TRUE;
      Seconds[Idx] = EfiTimeToEpoch (NewTime[Idx]);
    }
  }
 
  //
  // If a change is requested for exactly one of CreateTime and
  // ModificationTime, we'll change the last modification time. If changes are
  // requested for both, and to the same timestamp, we'll similarly update the
  // last modification time. If changes are requested for both, but to
  // different timestamps, we reject the request.
  //
  if (Change[0] && Change[2] && (Seconds[0] != Seconds[2])) {
    return EFI_ACCESS_DENIED;
  }
 
  *UpdateAtime = FALSE;
  *UpdateMtime = FALSE;
 
  if (Change[0]) {
    *UpdateMtime = TRUE;
    *Mtime       = Seconds[0];
  }
 
  if (Change[1]) {
    *UpdateAtime = TRUE;
    *Atime       = Seconds[1];
  }
 
  if (Change[2]) {
    *UpdateMtime = TRUE;
    *Mtime       = Seconds[2];
  }
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
VirtioFsGetFuseModeUpdate (
  IN     EFI_FILE_INFO  *Info,
  IN     EFI_FILE_INFO  *NewInfo,
  OUT BOOLEAN           *Update,
  OUT UINT32            *Mode
  )
{
  UINT64   Toggle;
  BOOLEAN  IsDirectory;
  BOOLEAN  IsWriteable;
  BOOLEAN  WillBeWriteable;
 
  Toggle = Info->Attribute ^ NewInfo->Attribute;
  if ((Toggle & ~EFI_FILE_VALID_ATTR) != 0) {
    //
    // Unknown attribute requested.
    //
    return EFI_ACCESS_DENIED;
  }
 
  if ((Toggle & EFI_FILE_DIRECTORY) != 0) {
    //
    // EFI_FILE_DIRECTORY cannot be toggled.
    //
    return EFI_ACCESS_DENIED;
  }
 
  IsDirectory     = (BOOLEAN)((Info->Attribute    & EFI_FILE_DIRECTORY) != 0);
  IsWriteable     = (BOOLEAN)((Info->Attribute    & EFI_FILE_READ_ONLY) == 0);
  WillBeWriteable = (BOOLEAN)((NewInfo->Attribute & EFI_FILE_READ_ONLY) == 0);
 
  if (IsWriteable == WillBeWriteable) {
    *Update = FALSE;
    return EFI_SUCCESS;
  }
 
  if (IsDirectory) {
    if (WillBeWriteable) {
      *Mode = (VIRTIO_FS_FUSE_MODE_PERM_RWXU |
               VIRTIO_FS_FUSE_MODE_PERM_RWXG |
               VIRTIO_FS_FUSE_MODE_PERM_RWXO);
    } else {
      *Mode = (VIRTIO_FS_FUSE_MODE_PERM_RUSR |
               VIRTIO_FS_FUSE_MODE_PERM_XUSR |
               VIRTIO_FS_FUSE_MODE_PERM_RGRP |
               VIRTIO_FS_FUSE_MODE_PERM_XGRP |
               VIRTIO_FS_FUSE_MODE_PERM_ROTH |
               VIRTIO_FS_FUSE_MODE_PERM_XOTH);
    }
  } else {
    if (WillBeWriteable) {
      *Mode = (VIRTIO_FS_FUSE_MODE_PERM_RUSR |
               VIRTIO_FS_FUSE_MODE_PERM_WUSR |
               VIRTIO_FS_FUSE_MODE_PERM_RGRP |
               VIRTIO_FS_FUSE_MODE_PERM_WGRP |
               VIRTIO_FS_FUSE_MODE_PERM_ROTH |
               VIRTIO_FS_FUSE_MODE_PERM_WOTH);
    } else {
      *Mode = (VIRTIO_FS_FUSE_MODE_PERM_RUSR |
               VIRTIO_FS_FUSE_MODE_PERM_RGRP |
               VIRTIO_FS_FUSE_MODE_PERM_ROTH);
    }
  }
 
  *Update = TRUE;
  return EFI_SUCCESS;
}