OvmfPkg/VirtioFsDxe: add a shared wrapper for FUSE_READ / FUSE_READDIRPLUS

Add the VirtioFsFuseReadFileOrDir() function, for sending the FUSE_READ or
FUSE_READDIRPLUS command to the Virtio Filesystem device.

Parsing the structured FUSE_READDIRPLUS output is complex, and cannot be
integrated into the wrapper function. Given that fact, FUSE_READ and
FUSE_READDIRPLUS turn out to need identical low-level handling, except for
the opcode. Hence the shared wrapper function.

(It's prudent to verify whether the FUSE server supports FUSE_READDIRPLUS,
so update the session init code accordingly.)

This is the first FUSE request wrapper function that deals with a variable
size tail buffer.

Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3097
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20201216211125.19496-33-lersek@redhat.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@arm.com>

4 files changed, 209 insertions, 4 deletions

diff --git a/OvmfPkg/VirtioFsDxe/FuseInit.c b/OvmfPkg/VirtioFsDxe/FuseInit.c
index aa19dbdc05..7aa6ee75ca 100644
--- a/OvmfPkg/VirtioFsDxe/FuseInit.c
+++ b/OvmfPkg/VirtioFsDxe/FuseInit.c
@@ -26,7 +26,8 @@
 

   @retval EFI_SUCCESS      The FUSE session has been started.

 

-  @retval EFI_UNSUPPORTED  FUSE interface version negotiation failed.

+  @retval EFI_UNSUPPORTED  FUSE interface version or feature negotiation

+                           failed.

 

   @return                  The "errno" value mapped to an EFI_STATUS code, if

                            the Virtio Filesystem device explicitly reported an

@@ -97,7 +98,7 @@ VirtioFsFuseInitSession (
   InitReq.Major        = VIRTIO_FS_FUSE_MAJOR;

   InitReq.Minor        = VIRTIO_FS_FUSE_MINOR;

   InitReq.MaxReadahead = 0;

-  InitReq.Flags        = 0;

+  InitReq.Flags        = VIRTIO_FS_FUSE_INIT_REQ_F_DO_READDIRPLUS;

 

   //

   // Submit the request.

@@ -121,10 +122,11 @@ VirtioFsFuseInitSession (
   }

 

   //

-  // Check FUSE interface version compatibility.

+  // Check FUSE interface version / feature compatibility.

   //

   if (InitResp.Major < InitReq.Major ||

-      (InitResp.Major == InitReq.Major && InitResp.Minor < InitReq.Minor)) {

+      (InitResp.Major == InitReq.Major && InitResp.Minor < InitReq.Minor) ||

+      (InitResp.Flags & VIRTIO_FS_FUSE_INIT_REQ_F_DO_READDIRPLUS) == 0) {

     return EFI_UNSUPPORTED;

   }

 

diff --git a/OvmfPkg/VirtioFsDxe/FuseRead.c b/OvmfPkg/VirtioFsDxe/FuseRead.c
new file mode 100644
index 0000000000..1611e298b9
--- /dev/null
+++ b/OvmfPkg/VirtioFsDxe/FuseRead.c
@@ -0,0 +1,191 @@
+/** @file

+  FUSE_READ / FUSE_READDIRPLUS wrapper for the Virtio Filesystem device.

+

+  Copyright (C) 2020, Red Hat, Inc.

+

+  SPDX-License-Identifier: BSD-2-Clause-Patent

+**/

+

+#include "VirtioFsDxe.h"

+

+/**

+  Read a chunk from a regular file or a directory stream, by sending the

+  FUSE_READ / FUSE_READDIRPLUS request to the Virtio Filesystem device.

+

+  The function may only be called after VirtioFsFuseInitSession() returns

+  successfully and before VirtioFsUninit() is called.

+

+  @param[in,out] VirtioFs  The Virtio Filesystem device to send the FUSE_READ

+                           or FUSE_READDIRPLUS request to. On output, the FUSE

+                           request counter "VirtioFs->RequestId" will have been

+                           incremented.

+

+  @param[in] NodeId        The inode number of the regular file or directory

+                           stream to read from.

+

+  @param[in] FuseHandle    The open handle to the regular file or directory

+                           stream to read from.

+

+  @param[in] IsDir         TRUE if NodeId and FuseHandle refer to a directory,

+                           FALSE if NodeId and FuseHandle refer to a regular

+                           file.

+

+  @param[in] Offset        If IsDir is FALSE: the absolute file position at

+                           which to start reading.

+

+                           If IsDir is TRUE: the directory stream cookie at

+                           which to start or continue reading. The zero-valued

+                           cookie identifies the start of the directory stream.

+                           Further positions in the directory stream can be

+                           passed in from the CookieForNextEntry field of

+                           VIRTIO_FS_FUSE_DIRENTPLUS_RESPONSE.

+

+  @param[in,out] Size      On input, the number of bytes to read. On successful

+                           return, the number of bytes actually read, which may

+                           be smaller than the value on input.

+

+                           When reading a regular file (i.e., when IsDir is

+                           FALSE), EOF can be detected by passing in a nonzero

+                           Size, and finding a zero Size on output.

+

+                           When reading a directory stream (i.e., when IsDir is

+                           TRUE), Data consists of a sequence of variably-sized

+                           records (directory entries). A read operation

+                           returns the maximal sequence of records that fits in

+                           Size, without having to truncate a record. In order

+                           to guarantee progress, call

+

+                             VirtioFsFuseStatFs (VirtioFs, NodeId,

+                               &FilesysAttr)

+

+                           first, to learn the maximum Namelen for the

+                           directory stream. Then assign Size at least

+

+                             VIRTIO_FS_FUSE_DIRENTPLUS_RESPONSE_SIZE (

+                               FilesysAttr.Namelen)

+

+                           on input. (Remember that

+                           VIRTIO_FS_FUSE_DIRENTPLUS_RESPONSE_SIZE() may return

+                           0 if its Namelen argument is invalid.) EOF can be

+                           detected if Size is set on input like described

+                           above, and Size is zero on output.

+

+  @param[out] Data         Buffer to read the bytes from the regular file or

+                           the directory stream into. The caller is responsible

+                           for providing room for (at least) as many bytes in

+                           Data as Size is on input.

+

+  @retval EFI_SUCCESS  Read successful. The caller is responsible for checking

+                       Size to learn the actual byte count transferred.

+

+  @return              The "errno" value mapped to an EFI_STATUS code, if the

+                       Virtio Filesystem device explicitly reported an error.

+

+  @return              Error codes propagated from VirtioFsSgListsValidate(),

+                       VirtioFsFuseNewRequest(), VirtioFsSgListsSubmit(),

+                       VirtioFsFuseCheckResponse().

+**/

+EFI_STATUS

+VirtioFsFuseReadFileOrDir (

+  IN OUT VIRTIO_FS *VirtioFs,

+  IN     UINT64    NodeId,

+  IN     UINT64    FuseHandle,

+  IN     BOOLEAN   IsDir,

+  IN     UINT64    Offset,

+  IN OUT UINT32    *Size,

+     OUT VOID      *Data

+  )

+{

+  VIRTIO_FS_FUSE_REQUEST        CommonReq;

+  VIRTIO_FS_FUSE_READ_REQUEST   ReadReq;

+  VIRTIO_FS_IO_VECTOR           ReqIoVec[2];

+  VIRTIO_FS_SCATTER_GATHER_LIST ReqSgList;

+  VIRTIO_FS_FUSE_RESPONSE       CommonResp;

+  VIRTIO_FS_IO_VECTOR           RespIoVec[2];

+  VIRTIO_FS_SCATTER_GATHER_LIST RespSgList;

+  EFI_STATUS                    Status;

+  UINTN                         TailBufferFill;

+

+  //

+  // Set up the scatter-gather lists.

+  //

+  ReqIoVec[0].Buffer = &CommonReq;

+  ReqIoVec[0].Size   = sizeof CommonReq;

+  ReqIoVec[1].Buffer = &ReadReq;

+  ReqIoVec[1].Size   = sizeof ReadReq;

+  ReqSgList.IoVec    = ReqIoVec;

+  ReqSgList.NumVec   = ARRAY_SIZE (ReqIoVec);

+

+  RespIoVec[0].Buffer = &CommonResp;

+  RespIoVec[0].Size   = sizeof CommonResp;

+  RespIoVec[1].Buffer = Data;

+  RespIoVec[1].Size   = *Size;

+  RespSgList.IoVec    = RespIoVec;

+  RespSgList.NumVec   = ARRAY_SIZE (RespIoVec);

+

+  //

+  // Validate the scatter-gather lists; calculate the total transfer sizes.

+  //

+  Status = VirtioFsSgListsValidate (VirtioFs, &ReqSgList, &RespSgList);

+  if (EFI_ERROR (Status)) {

+    return Status;

+  }

+

+  //

+  // Populate the common request header.

+  //

+  Status = VirtioFsFuseNewRequest (

+             VirtioFs,

+             &CommonReq,

+             ReqSgList.TotalSize,

+             IsDir ? VirtioFsFuseOpReadDirPlus : VirtioFsFuseOpRead,

+             NodeId

+             );

+  if (EFI_ERROR (Status)) {

+    return Status;

+  }

+

+  //

+  // Populate the FUSE_READ- / FUSE_READDIRPLUS-specific fields.

+  //

+  ReadReq.FileHandle = FuseHandle;

+  ReadReq.Offset     = Offset;

+  ReadReq.Size       = *Size;

+  ReadReq.ReadFlags  = 0;

+  ReadReq.LockOwner  = 0;

+  ReadReq.Flags      = 0;

+  ReadReq.Padding    = 0;

+

+  //

+  // Submit the request.

+  //

+  Status = VirtioFsSgListsSubmit (VirtioFs, &ReqSgList, &RespSgList);

+  if (EFI_ERROR (Status)) {

+    return Status;

+  }

+

+  //

+  // Verify the response. Note that TailBufferFill is variable.

+  //

+  Status = VirtioFsFuseCheckResponse (&RespSgList, CommonReq.Unique,

+             &TailBufferFill);

+  if (EFI_ERROR (Status)) {

+    if (Status == EFI_DEVICE_ERROR) {

+      DEBUG ((DEBUG_ERROR, "%a: Label=\"%s\" NodeId=%Lu FuseHandle=%Lu "

+        "IsDir=%d Offset=0x%Lx Size=0x%x Data@%p Errno=%d\n", __FUNCTION__,

+        VirtioFs->Label, NodeId, FuseHandle, IsDir, Offset, *Size, Data,

+        CommonResp.Error));

+      Status = VirtioFsErrnoToEfiStatus (CommonResp.Error);

+    }

+    return Status;

+  }

+

+  //

+  // Report the actual transfer size.

+  //

+  // Integer overflow in the (UINT32) cast below is not possible; the

+  // VIRTIO_FS_SCATTER_GATHER_LIST functions would have caught that.

+  //

+  *Size = (UINT32)TailBufferFill;

+  return EFI_SUCCESS;

+}

diff --git a/OvmfPkg/VirtioFsDxe/VirtioFsDxe.h b/OvmfPkg/VirtioFsDxe/VirtioFsDxe.h
index 948fcfb6b6..f5501af7d0 100644
--- a/OvmfPkg/VirtioFsDxe/VirtioFsDxe.h
+++ b/OvmfPkg/VirtioFsDxe/VirtioFsDxe.h
@@ -299,6 +299,17 @@ VirtioFsFuseOpen (
   );

 

 EFI_STATUS

+VirtioFsFuseReadFileOrDir (

+  IN OUT VIRTIO_FS *VirtioFs,

+  IN     UINT64    NodeId,

+  IN     UINT64    FuseHandle,

+  IN     BOOLEAN   IsDir,

+  IN     UINT64    Offset,

+  IN OUT UINT32    *Size,

+     OUT VOID      *Data

+  );

+

+EFI_STATUS

 VirtioFsFuseStatFs (

   IN OUT VIRTIO_FS                      *VirtioFs,

   IN     UINT64                         NodeId,

diff --git a/OvmfPkg/VirtioFsDxe/VirtioFsDxe.inf b/OvmfPkg/VirtioFsDxe/VirtioFsDxe.inf
index 3cb5c101c3..39c77c7c4e 100644
--- a/OvmfPkg/VirtioFsDxe/VirtioFsDxe.inf
+++ b/OvmfPkg/VirtioFsDxe/VirtioFsDxe.inf
@@ -93,6 +93,7 @@
   FuseOpen.c

   FuseOpenDir.c

   FuseOpenOrCreate.c

+  FuseRead.c

   FuseRelease.c

   FuseStatFs.c

   FuseUnlink.c