OvmfPkg/VirtioFsDxe/SimpleFsRead.c

   1 /** @file
   2   EFI_FILE_PROTOCOL.Read() member function for the Virtio Filesystem driver.
   3
   4   Copyright (C) 2020, Red Hat, Inc.
   5
   6   SPDX-License-Identifier: BSD-2-Clause-Patent
   7 **/
   8
   9 #include "VirtioFsDxe.h"
  10
  11 /**
  12   Read from a regular file.
  13 **/
  14 STATIC
  15 EFI_STATUS
  16 ReadRegularFile (
  17   IN OUT VIRTIO_FS_FILE *VirtioFsFile,
  18   IN OUT UINTN          *BufferSize,
  19      OUT VOID           *Buffer
  20   )
  21 {
  22   VIRTIO_FS                          *VirtioFs;
  23   EFI_STATUS                         Status;
  24   VIRTIO_FS_FUSE_ATTRIBUTES_RESPONSE FuseAttr;
  25   UINTN                              Transferred;
  26   UINTN                              Left;
  27
  28   VirtioFs = VirtioFsFile->OwnerFs;
  29   //
  30   // The UEFI spec forbids reads that start beyond the end of the file.
  31   //
  32   Status = VirtioFsFuseGetAttr (VirtioFs, VirtioFsFile->NodeId, &FuseAttr);
  33   if (EFI_ERROR (Status) || VirtioFsFile->FilePosition > FuseAttr.Size) {
  34     return EFI_DEVICE_ERROR;
  35   }
  36
  37   Status      = EFI_SUCCESS;
  38   Transferred = 0;
  39   Left        = *BufferSize;
  40   while (Left > 0) {
  41     UINT32 ReadSize;
  42
  43     //
  44     // FUSE_READ cannot express a >=4GB buffer size.
  45     //
  46     ReadSize = (UINT32)MIN ((UINTN)MAX_UINT32, Left);
  47     Status = VirtioFsFuseReadFileOrDir (
  48                VirtioFs,
  49                VirtioFsFile->NodeId,
  50                VirtioFsFile->FuseHandle,
  51                FALSE,                                    // IsDir
  52                VirtioFsFile->FilePosition + Transferred,
  53                &ReadSize,
  54                (UINT8 *)Buffer + Transferred
  55                );
  56     if (EFI_ERROR (Status) || ReadSize == 0) {
  57       break;
  58     }
  59     Transferred += ReadSize;
  60     Left        -= ReadSize;
  61   }
  62
  63   *BufferSize = Transferred;
  64   VirtioFsFile->FilePosition += Transferred;
  65   //
  66   // If we managed to read some data, return success. If zero bytes were
  67   // transferred due to zero-sized buffer on input or due to EOF on first read,
  68   // return SUCCESS. Otherwise, return the error due to which zero bytes were
  69   // transferred.
  70   //
  71   return (Transferred > 0) ? EFI_SUCCESS : Status;
  72 }
  73
  74 EFI_STATUS
  75 EFIAPI
  76 VirtioFsSimpleFileRead (
  77   IN     EFI_FILE_PROTOCOL *This,
  78   IN OUT UINTN             *BufferSize,
  79      OUT VOID              *Buffer
  80   )
  81 {
  82   VIRTIO_FS_FILE *VirtioFsFile;
  83   EFI_STATUS     Status;
  84
  85   VirtioFsFile = VIRTIO_FS_FILE_FROM_SIMPLE_FILE (This);
  86
  87   if (VirtioFsFile->IsDirectory) {
  88     Status = EFI_NO_MEDIA;
  89   } else {
  90     Status = ReadRegularFile (VirtioFsFile, BufferSize, Buffer);
  91   }
  92   return Status;
  93 }