OvmfPkg/VirtioFsDxe: implement EFI_FILE_PROTOCOL.Read() for regular files

[mirror_edk2.git] / OvmfPkg / VirtioFsDxe / SimpleFsRead.c

/** @file\r
  EFI_FILE_PROTOCOL.Read() member function for the Virtio Filesystem driver.\r
\r
  Copyright (C) 2020, Red Hat, Inc.\r
\r
  SPDX-License-Identifier: BSD-2-Clause-Patent\r
**/\r
\r
#include "VirtioFsDxe.h"\r
\r
/**\r
  Read from a regular file.\r
**/\r
STATIC\r
EFI_STATUS\r
ReadRegularFile (\r
  IN OUT VIRTIO_FS_FILE *VirtioFsFile,\r
  IN OUT UINTN          *BufferSize,\r
     OUT VOID           *Buffer\r
  )\r
{\r
  VIRTIO_FS                          *VirtioFs;\r
  EFI_STATUS                         Status;\r
  VIRTIO_FS_FUSE_ATTRIBUTES_RESPONSE FuseAttr;\r
  UINTN                              Transferred;\r
  UINTN                              Left;\r
\r
  VirtioFs = VirtioFsFile->OwnerFs;\r
  //\r
  // The UEFI spec forbids reads that start beyond the end of the file.\r
  //\r
  Status = VirtioFsFuseGetAttr (VirtioFs, VirtioFsFile->NodeId, &FuseAttr);\r
  if (EFI_ERROR (Status) || VirtioFsFile->FilePosition > FuseAttr.Size) {\r
    return EFI_DEVICE_ERROR;\r
  }\r
\r
  Status      = EFI_SUCCESS;\r
  Transferred = 0;\r
  Left        = *BufferSize;\r
  while (Left > 0) {\r
    UINT32 ReadSize;\r
\r
    //\r
    // FUSE_READ cannot express a >=4GB buffer size.\r
    //\r
    ReadSize = (UINT32)MIN ((UINTN)MAX_UINT32, Left);\r
    Status = VirtioFsFuseReadFileOrDir (\r
               VirtioFs,\r
               VirtioFsFile->NodeId,\r
               VirtioFsFile->FuseHandle,\r
               FALSE,                                    // IsDir\r
               VirtioFsFile->FilePosition + Transferred,\r
               &ReadSize,\r
               (UINT8 *)Buffer + Transferred\r
               );\r
    if (EFI_ERROR (Status) || ReadSize == 0) {\r
      break;\r
    }\r
    Transferred += ReadSize;\r
    Left        -= ReadSize;\r
  }\r
\r
  *BufferSize = Transferred;\r
  VirtioFsFile->FilePosition += Transferred;\r
  //\r
  // If we managed to read some data, return success. If zero bytes were\r
  // transferred due to zero-sized buffer on input or due to EOF on first read,\r
  // return SUCCESS. Otherwise, return the error due to which zero bytes were\r
  // transferred.\r
  //\r
  return (Transferred > 0) ? EFI_SUCCESS : Status;\r
}\r
\r
EFI_STATUS\r
EFIAPI\r
VirtioFsSimpleFileRead (\r
  IN     EFI_FILE_PROTOCOL *This,\r
  IN OUT UINTN             *BufferSize,\r
     OUT VOID              *Buffer\r
  )\r
{\r
  VIRTIO_FS_FILE *VirtioFsFile;\r
  EFI_STATUS     Status;\r
\r
  VirtioFsFile = VIRTIO_FS_FILE_FROM_SIMPLE_FILE (This);\r
\r
  if (VirtioFsFile->IsDirectory) {\r
    Status = EFI_NO_MEDIA;\r
  } else {\r
    Status = ReadRegularFile (VirtioFsFile, BufferSize, Buffer);\r
  }\r
  return Status;\r
}\r