OvmfPkg/VirtioFsDxe/VirtioFsDxe.inf

   1 ## @file
   2 # Provide EFI_SIMPLE_FILE_SYSTEM_PROTOCOL instances on virtio-fs devices.
   3 #
   4 # Copyright (C) 2020, Red Hat, Inc.
   5 #
   6 # SPDX-License-Identifier: BSD-2-Clause-Patent
   7 #
   8 #
   9 # Permission Model of this driver:
  10 #
  11 # Regardless of the UID and GID values this driver send in the FUSE request
  12 # header, the daemon (that is, the Virtio Filesystem device) always acts with
  13 # root privileges on the host side. The only time the daemon considers said UID
  14 # and GID fields is when creating a new file or directory. Thus, the guest
  15 # driver cannot rely on the host for enforcing any file mode permissions,
  16 # regardless of the "personality" that the guest driver poses as, because
  17 # "root" on the host side ignores all file mode bits.
  18 #
  19 # Therefore the guest driver has to do its own permission checking, and use the
  20 # host-side file mode bits only as a kind of "metadata storage" or "reminder"
  21 # -- hopefully in a way that makes some sense on the host side too.
  22 #
  23 # The complete mapping between the EFI_FILE_PROTOCOL and the host-side file
  24 # mode bits is described below.
  25 #
  26 # - The guest driver poses as UID 0, GID 0, PID 1.
  27 #
  28 # - If and only if all "w" bits are missing from a file on the host side, then
  29 #   the file or directory is reported as EFI_FILE_READ_ONLY in the guest. When
  30 #   setting EFI_FILE_READ_ONLY in the guest, all "w" bits (0222) are cleared on
  31 #   the host; when clearing EFI_FILE_READ_ONLY in the guest, all "w" bits are
  32 #   set on the host. Viewed from the host side, this sort of reflects that an
  33 #   EFI_FILE_READ_ONLY file should not be written by anyone.
  34 #
  35 # - The attributes EFI_FILE_HIDDEN, EFI_FILE_SYSTEM, EFI_FILE_RESERVED, and
  36 #   EFI_FILE_ARCHIVE are never reported in the guest, and they are silently
  37 #   ignored when a SetInfo() call or a file-creating Open() call requests them.
  38 #
  39 # - On the host, files are created with 0666 file mode bits, directories are
  40 #   created with 0777 file mode bits.
  41 #
  42 # - In the guest, the EFI_FILE_READ_ONLY attribute only controls the permitted
  43 #   open mode. In particular, on directories, the EFI_FILE_READ_ONLY attribute
  44 #   does not prevent the creation or deletion of entries inside the directory;
  45 #   EFI_FILE_READ_ONLY only prevents the renaming, deleting, flushing (syncing)
  46 #   and touching of the directory itself (with "touching" meaning updating the
  47 #   timestamps). The fact that EFI_FILE_READ_ONLY being set on a directory is
  48 #   irrelevant in the guest with regard to entry creation/deletion, is
  49 #   well-mirrored by the fact that virtiofsd -- which runs as root, regardless
  50 #   of guest driver personality -- ignores the absence of "w" permissions on a
  51 #   host-side directory, when creating or removing entries in it.
  52 #
  53 # - When an EFI_FILE_PROTOCOL is opened read-only, then the Delete(), Write()
  54 #   and Flush() member functions are disabled for it. Additionally, SetInfo()
  55 #   is restricted to flipping the EFI_FILE_READ_ONLY bit (which takes effect at
  56 #   the next Open()).
  57 #
  58 # - As a consequence of the above, for deleting a directory, it must be
  59 #   presented in the guest as openable for writing.
  60 #
  61 # - We diverge from the UEFI spec, and permit Flush() on a directory that has
  62 #   been opened read-write; otherwise the only way to invoke FUSE_FSYNCDIR on a
  63 #   directory would be to Close() it.
  64 #
  65 # - OpenVolume() opens the root directory for read-only access. The Open()
  66 #   member function may open it for read-write access. While the root directory
  67 #   cannot be renamed or deleted, opening it for read-write access is useful
  68 #   for calling Flush(), according to the previous paragraph, or for updating
  69 #   the root directory's timestamps with SetInfo().
  70 ##
  71
  72 [Defines]
  73   INF_VERSION                           = 1.29
  74   BASE_NAME                             = VirtioFsDxe
  75   FILE_GUID                             = 7BD9DDF7-8B83-488E-AEC9-24C78610289C
  76   MODULE_TYPE                           = UEFI_DRIVER
  77   ENTRY_POINT                           = VirtioFsEntryPoint
  78
  79 [Packages]
  80   EmbeddedPkg/EmbeddedPkg.dec
  81   MdePkg/MdePkg.dec
  82   OvmfPkg/OvmfPkg.dec
  83
  84 [Sources]
  85   DriverBinding.c
  86   FuseFlush.c
  87   FuseForget.c
  88   FuseFsync.c
  89   FuseGetAttr.c
  90   FuseInit.c
  91   FuseLookup.c
  92   FuseMkDir.c
  93   FuseOpen.c
  94   FuseOpenDir.c
  95   FuseOpenOrCreate.c
  96   FuseRead.c
  97   FuseRelease.c
  98   FuseRename.c
  99   FuseSetAttr.c
 100   FuseStatFs.c
 101   FuseUnlink.c
 102   FuseWrite.c
 103   Helpers.c
 104   SimpleFsClose.c
 105   SimpleFsDelete.c
 106   SimpleFsFlush.c
 107   SimpleFsGetInfo.c
 108   SimpleFsGetPosition.c
 109   SimpleFsOpen.c
 110   SimpleFsOpenVolume.c
 111   SimpleFsRead.c
 112   SimpleFsSetInfo.c
 113   SimpleFsSetPosition.c
 114   SimpleFsWrite.c
 115   VirtioFsDxe.h
 116
 117 [LibraryClasses]
 118   BaseLib
 119   BaseMemoryLib
 120   DebugLib
 121   MemoryAllocationLib
 122   TimeBaseLib
 123   UefiBootServicesTableLib
 124   UefiDriverEntryPoint
 125   VirtioLib
 126
 127 [Protocols]
 128   gEfiComponentName2ProtocolGuid        ## PRODUCES
 129   gEfiDriverBindingProtocolGuid         ## PRODUCES
 130   gEfiSimpleFileSystemProtocolGuid      ## BY_START
 131   gVirtioDeviceProtocolGuid             ## TO_START
 132
 133 [Guids]
 134   gEfiFileInfoGuid
 135   gEfiFileSystemInfoGuid
 136   gEfiFileSystemVolumeLabelInfoIdGuid