OvmfPkg/VirtioFsDxe: implement EFI_SIMPLE_FILE_SYSTEM_PROTOCOL.OpenVolume()

[mirror_edk2.git] / OvmfPkg / VirtioFsDxe / VirtioFsDxe.inf

## @file\r
# Provide EFI_SIMPLE_FILE_SYSTEM_PROTOCOL instances on virtio-fs devices.\r
#\r
# Copyright (C) 2020, Red Hat, Inc.\r
#\r
# SPDX-License-Identifier: BSD-2-Clause-Patent\r
#\r
#\r
# Permission Model of this driver:\r
#\r
# Regardless of the UID and GID values this driver send in the FUSE request\r
# header, the daemon (that is, the Virtio Filesystem device) always acts with\r
# root privileges on the host side. The only time the daemon considers said UID\r
# and GID fields is when creating a new file or directory. Thus, the guest\r
# driver cannot rely on the host for enforcing any file mode permissions,\r
# regardless of the "personality" that the guest driver poses as, because\r
# "root" on the host side ignores all file mode bits.\r
#\r
# Therefore the guest driver has to do its own permission checking, and use the\r
# host-side file mode bits only as a kind of "metadata storage" or "reminder"\r
# -- hopefully in a way that makes some sense on the host side too.\r
#\r
# The complete mapping between the EFI_FILE_PROTOCOL and the host-side file\r
# mode bits is described below.\r
#\r
# - The guest driver poses as UID 0, GID 0, PID 1.\r
#\r
# - If and only if all "w" bits are missing from a file on the host side, then\r
#   the file or directory is reported as EFI_FILE_READ_ONLY in the guest. When\r
#   setting EFI_FILE_READ_ONLY in the guest, all "w" bits (0222) are cleared on\r
#   the host; when clearing EFI_FILE_READ_ONLY in the guest, all "w" bits are\r
#   set on the host. Viewed from the host side, this sort of reflects that an\r
#   EFI_FILE_READ_ONLY file should not be written by anyone.\r
#\r
# - The attributes EFI_FILE_HIDDEN, EFI_FILE_SYSTEM, EFI_FILE_RESERVED, and\r
#   EFI_FILE_ARCHIVE are never reported in the guest, and they are silently\r
#   ignored when a SetInfo() call or a file-creating Open() call requests them.\r
#\r
# - On the host, files are created with 0666 file mode bits, directories are\r
#   created with 0777 file mode bits.\r
#\r
# - In the guest, the EFI_FILE_READ_ONLY attribute only controls the permitted\r
#   open mode. In particular, on directories, the EFI_FILE_READ_ONLY attribute\r
#   does not prevent the creation or deletion of entries inside the directory;\r
#   EFI_FILE_READ_ONLY only prevents the renaming, deleting, flushing (syncing)\r
#   and touching of the directory itself (with "touching" meaning updating the\r
#   timestamps). The fact that EFI_FILE_READ_ONLY being set on a directory is\r
#   irrelevant in the guest with regard to entry creation/deletion, is\r
#   well-mirrored by the fact that virtiofsd -- which runs as root, regardless\r
#   of guest driver personality -- ignores the absence of "w" permissions on a\r
#   host-side directory, when creating or removing entries in it.\r
#\r
# - When an EFI_FILE_PROTOCOL is opened read-only, then the Delete(), Write()\r
#   and Flush() member functions are disabled for it. Additionally, SetInfo()\r
#   is restricted to flipping the EFI_FILE_READ_ONLY bit (which takes effect at\r
#   the next Open()).\r
#\r
# - As a consequence of the above, for deleting a directory, it must be\r
#   presented in the guest as openable for writing.\r
#\r
# - We diverge from the UEFI spec, and permit Flush() on a directory that has\r
#   been opened read-write; otherwise the only way to invoke FUSE_FSYNCDIR on a\r
#   directory would be to Close() it.\r
#\r
# - OpenVolume() opens the root directory for read-only access. The Open()\r
#   member function may open it for read-write access. While the root directory\r
#   cannot be renamed or deleted, opening it for read-write access is useful\r
#   for calling Flush(), according to the previous paragraph, or for updating\r
#   the root directory's timestamps with SetInfo().\r
##\r
\r
[Defines]\r
  INF_VERSION                           = 1.29\r
  BASE_NAME                             = VirtioFsDxe\r
  FILE_GUID                             = 7BD9DDF7-8B83-488E-AEC9-24C78610289C\r
  MODULE_TYPE                           = UEFI_DRIVER\r
  ENTRY_POINT                           = VirtioFsEntryPoint\r
\r
[Packages]\r
  MdePkg/MdePkg.dec\r
  OvmfPkg/OvmfPkg.dec\r
\r
[Sources]\r
  DriverBinding.c\r
  FuseInit.c\r
  FuseOpenDir.c\r
  FuseRelease.c\r
  Helpers.c\r
  SimpleFsClose.c\r
  SimpleFsDelete.c\r
  SimpleFsFlush.c\r
  SimpleFsGetInfo.c\r
  SimpleFsGetPosition.c\r
  SimpleFsOpen.c\r
  SimpleFsOpenVolume.c\r
  SimpleFsRead.c\r
  SimpleFsSetInfo.c\r
  SimpleFsSetPosition.c\r
  SimpleFsWrite.c\r
  VirtioFsDxe.h\r
\r
[LibraryClasses]\r
  BaseLib\r
  DebugLib\r
  MemoryAllocationLib\r
  UefiBootServicesTableLib\r
  UefiDriverEntryPoint\r
  VirtioLib\r
\r
[Protocols]\r
  gEfiComponentName2ProtocolGuid        ## PRODUCES\r
  gEfiDriverBindingProtocolGuid         ## PRODUCES\r
  gEfiSimpleFileSystemProtocolGuid      ## BY_START\r
  gVirtioDeviceProtocolGuid             ## TO_START\r