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- /** @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;
- }
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