1 files changed, 159 insertions, 0 deletions
diff --git a/pkg/sentry/fs/file_operations.go b/pkg/sentry/fs/file_operations.go
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+++ b/pkg/sentry/fs/file_operations.go
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+// Copyright 2018 The gVisor Authors.
+//
+// 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"
+)
+
+// SpliceOpts define how a splice works.
+type SpliceOpts struct {
+	// Length is the length of the splice operation.
+	Length int64
+
+	// SrcOffset indicates whether the existing source file offset should
+	// be used. If this is true, then the Start value below is used.
+	//
+	// When passed to FileOperations object, this should always be true as
+	// the offset will be provided by a layer above, unless the object in
+	// question is a pipe or socket. This value can be relied upon for such
+	// an indicator.
+	SrcOffset bool
+
+	// SrcStart is the start of the source file. This is used only if
+	// SrcOffset is false.
+	SrcStart int64
+
+	// Dup indicates that the contents should not be consumed from the
+	// source (e.g. in the case of a socket or a pipe), but duplicated.
+	Dup bool
+
+	// DstOffset indicates that the destination file offset should be used.
+	//
+	// See SrcOffset for additional information.
+	DstOffset bool
+
+	// DstStart is the start of the destination file. This is used only if
+	// DstOffset is false.
+	DstStart int64
+}
+
+// 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)
+
+	// WriteTo is a variant of read that takes another file as a
+	// destination. For a splice (copy or move from one file to another),
+	// first a WriteTo on the source is attempted, followed by a ReadFrom
+	// on the destination, following by a buffered copy with standard Read
+	// and Write operations.
+	//
+	// The same preconditions as Read apply.
+	WriteTo(ctx context.Context, file *File, dst *File, opts SpliceOpts) (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)
+
+	// ReadFrom is a variant of write that takes a another file as a
+	// source. See WriteTo for details regarding how this is called.
+	//
+	// The same preconditions as Write apply; FileFlags.Write must be set.
+	ReadFrom(ctx context.Context, file *File, src *File, opts SpliceOpts) (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.FileNoMMap (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
+
+	// UnstableAttr returns the "unstable" attributes of the inode represented
+	// by the file. Most implementations can embed
+	// fsutil.FileUseInodeUnstableAttr, which delegates to
+	// InodeOperations.UnstableAttr.
+	UnstableAttr(ctx context.Context, file *File) (UnstableAttr, 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)
+}