Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 106 insertions, 0 deletions

diff --git a/pkg/sentry/fs/file_operations.go b/pkg/sentry/fs/file_operations.go
new file mode 100644
index 000000000..d223bb5c7
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+++ b/pkg/sentry/fs/file_operations.go
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+// Copyright 2018 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package fs
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/memmap"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+	"gvisor.googlesource.com/gvisor/pkg/waiter"
+)
+
+// FileOperations are operations on a File that diverge per file system.
+//
+// Operations that take a *File may use only the following interfaces:
+//
+// - File.UniqueID:	Operations may only read this value.
+// - File.Dirent:	Operations must not take or drop a reference.
+// - File.Offset(): 	This value is guaranteed to not change for the
+//			duration of the operation.
+// - File.Flags():	This value may change during the operation.
+type FileOperations interface {
+	// Release release resources held by FileOperations.
+	Release()
+
+	// Waitable defines how this File can be waited on for read and
+	// write readiness.
+	waiter.Waitable
+
+	// Seek seeks to offset based on SeekWhence. Returns the new
+	// offset or no change in the offset and an error.
+	Seek(ctx context.Context, file *File, whence SeekWhence, offset int64) (int64, error)
+
+	// Readdir reads the directory entries of file and serializes them
+	// using serializer.
+	//
+	// Returns the new directory offset or no change in the offset and
+	// an error. The offset returned must not be less than file.Offset().
+	//
+	// Serialization of directory entries must not happen asynchronously.
+	Readdir(ctx context.Context, file *File, serializer DentrySerializer) (int64, error)
+
+	// Read reads from file into dst at offset and returns the number
+	// of bytes read which must be greater than or equal to 0. File
+	// systems that do not support reading at an offset, (i.e. pipefs,
+	// sockfs) may ignore the offset. These file systems are expected
+	// to construct Files with !FileFlags.Pread.
+	//
+	// Read may return a nil error and only partially fill dst (at or
+	// before EOF). If the file represents a symlink, Read reads the target
+	// value of the symlink.
+	//
+	// Read does not check permissions nor flags.
+	//
+	// Read must not be called if !FileFlags.Read.
+	Read(ctx context.Context, file *File, dst usermem.IOSequence, offset int64) (int64, error)
+
+	// Write writes src to file at offset and returns the number of bytes
+	// written which must be greater than or equal to 0. Like Read, file
+	// systems that do not support writing at an offset (i.e. pipefs, sockfs)
+	// may ignore the offset. These file systems are expected to construct
+	// Files with !FileFlags.Pwrite.
+	//
+	// If only part of src could be written, Write must return an error
+	// indicating why (e.g. syserror.ErrWouldBlock).
+	//
+	// Write does not check permissions nor flags.
+	//
+	// Write must not be called if !FileFlags.Write.
+	Write(ctx context.Context, file *File, src usermem.IOSequence, offset int64) (int64, error)
+
+	// Fsync writes buffered modifications of file and/or flushes in-flight
+	// operations to backing storage based on syncType. The range to sync is
+	// [start, end]. The end is inclusive so that the last byte of a maximally
+	// sized file can be synced.
+	Fsync(ctx context.Context, file *File, start, end int64, syncType SyncType) error
+
+	// Flush this file's buffers/state (on close(2)).
+	Flush(ctx context.Context, file *File) error
+
+	// ConfigureMMap mutates opts to implement mmap(2) for the file. Most
+	// implementations can either embed fsutil.NoMMap (if they don't support
+	// memory mapping) or call fsutil.GenericConfigureMMap with the appropriate
+	// memmap.Mappable.
+	ConfigureMMap(ctx context.Context, file *File, opts *memmap.MMapOpts) error
+
+	// Ioctl implements the ioctl(2) linux syscall.
+	//
+	// io provides access to the virtual memory space to which pointers in args
+	// refer.
+	//
+	// Preconditions: The AddressSpace (if any) that io refers to is activated.
+	Ioctl(ctx context.Context, io usermem.IO, args arch.SyscallArguments) (uintptr, error)
+}