OvmfPkg/VirtioFsDxe: implement the wrapper function for FUSE_OPENDIR

Add the VirtioFsFuseOpenDir() function, for sending the FUSE_OPENDIR
command to the Virtio Filesystem device.

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: <20201216211125.19496-10-lersek@redhat.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@arm.com>

OvmfPkg/Include/IndustryStandard/VirtioFs.h

@@ -81,6 +81,7 @@ typedef struct {
 //
 typedef enum {
   VirtioFsFuseOpInit        = 26,
+  VirtioFsFuseOpOpenDir     = 27,
 } VIRTIO_FS_FUSE_OPCODE;
 
 #pragma pack (1)
@@ -127,6 +128,20 @@ typedef struct {
   UINT16 MapAlignment;
   UINT32 Unused[8];
 } VIRTIO_FS_FUSE_INIT_RESPONSE;
+
+//
+// Headers for VirtioFsFuseOpOpenDir.
+//
+typedef struct {
+  UINT32 Flags;
+  UINT32 Unused;
+} VIRTIO_FS_FUSE_OPEN_REQUEST;
+
+typedef struct {
+  UINT64 FileHandle;
+  UINT32 OpenFlags;
+  UINT32 Padding;
+} VIRTIO_FS_FUSE_OPEN_RESPONSE;
 #pragma pack ()
 
 #endif // VIRTIO_FS_H_

OvmfPkg/VirtioFsDxe/FuseOpenDir.c

@@ -0,0 +1,120 @@
+/** @file
+  FUSE_OPENDIR wrapper for the Virtio Filesystem device.
+
+  Copyright (C) 2020, Red Hat, Inc.
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+**/
+
+#include "VirtioFsDxe.h"
+
+/**
+  Send a FUSE_OPENDIR request to the Virtio Filesystem device, for opening a
+  directory.
+
+  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_OPENDIR request to. On output, the FUSE request
+                           counter "VirtioFs->RequestId" will have been
+                           incremented.
+
+  @param[in] NodeId        The inode number of the directory to open.
+
+  @param[out] FuseHandle   The open file handle returned by the Virtio
+                           Filesystem device.
+
+  @retval EFI_SUCCESS  The directory has been opened.
+
+  @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
+VirtioFsFuseOpenDir (
+  IN OUT VIRTIO_FS *VirtioFs,
+  IN     UINT64    NodeId,
+     OUT UINT64    *FuseHandle
+  )
+{
+  VIRTIO_FS_FUSE_REQUEST        CommonReq;
+  VIRTIO_FS_FUSE_OPEN_REQUEST   OpenReq;
+  VIRTIO_FS_IO_VECTOR           ReqIoVec[2];
+  VIRTIO_FS_SCATTER_GATHER_LIST ReqSgList;
+  VIRTIO_FS_FUSE_RESPONSE       CommonResp;
+  VIRTIO_FS_FUSE_OPEN_RESPONSE  OpenResp;
+  VIRTIO_FS_IO_VECTOR           RespIoVec[2];
+  VIRTIO_FS_SCATTER_GATHER_LIST RespSgList;
+  EFI_STATUS                    Status;
+
+  //
+  // Set up the scatter-gather lists.
+  //
+  ReqIoVec[0].Buffer = &CommonReq;
+  ReqIoVec[0].Size   = sizeof CommonReq;
+  ReqIoVec[1].Buffer = &OpenReq;
+  ReqIoVec[1].Size   = sizeof OpenReq;
+  ReqSgList.IoVec    = ReqIoVec;
+  ReqSgList.NumVec   = ARRAY_SIZE (ReqIoVec);
+
+  RespIoVec[0].Buffer = &CommonResp;
+  RespIoVec[0].Size   = sizeof CommonResp;
+  RespIoVec[1].Buffer = &OpenResp;
+  RespIoVec[1].Size   = sizeof OpenResp;
+  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,
+             VirtioFsFuseOpOpenDir, NodeId);
+  if (EFI_ERROR (Status)) {
+    return Status;
+  }
+
+  //
+  // Populate the FUSE_OPENDIR-specific fields.
+  //
+  OpenReq.Flags  = 0;
+  OpenReq.Unused = 0;
+
+  //
+  // Submit the request.
+  //
+  Status = VirtioFsSgListsSubmit (VirtioFs, &ReqSgList, &RespSgList);
+  if (EFI_ERROR (Status)) {
+    return Status;
+  }
+
+  //
+  // Verify the response (all response buffers are fixed size).
+  //
+  Status = VirtioFsFuseCheckResponse (&RespSgList, CommonReq.Unique, NULL);
+  if (EFI_ERROR (Status)) {
+    if (Status == EFI_DEVICE_ERROR) {
+      DEBUG ((DEBUG_ERROR, "%a: Label=\"%s\" NodeId=%Lu Errno=%d\n",
+        __FUNCTION__, VirtioFs->Label, NodeId, CommonResp.Error));
+      Status = VirtioFsErrnoToEfiStatus (CommonResp.Error);
+    }
+    return Status;
+  }
+
+  //
+  // Output the open file handle.
+  //
+  *FuseHandle = OpenResp.FileHandle;
+  return EFI_SUCCESS;
+}

OvmfPkg/VirtioFsDxe/VirtioFsDxe.h

@@ -163,6 +163,13 @@ VirtioFsFuseInitSession (
   IN OUT VIRTIO_FS *VirtioFs
   );
 
+EFI_STATUS
+VirtioFsFuseOpenDir (
+  IN OUT VIRTIO_FS *VirtioFs,
+  IN     UINT64    NodeId,
+     OUT UINT64    *FuseHandle
+  );
+
 //
 // EFI_SIMPLE_FILE_SYSTEM_PROTOCOL member functions for the Virtio Filesystem
 // driver.

OvmfPkg/VirtioFsDxe/VirtioFsDxe.inf

@@ -83,6 +83,7 @@
 [Sources]
   DriverBinding.c
   FuseInit.c
+  FuseOpenDir.c
   Helpers.c
   SimpleFsOpenVolume.c
   VirtioFsDxe.h