1 files changed, 207 insertions, 0 deletions
diff --git a/pkg/sentry/fsimpl/kernfs/fd_impl_util.go b/pkg/sentry/fsimpl/kernfs/fd_impl_util.go
new file mode 100644
index 000000000..d6c18937a
--- /dev/null
+++ b/pkg/sentry/fsimpl/kernfs/fd_impl_util.go
@@ -0,0 +1,207 @@
+// Copyright 2019 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 kernfs
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/context"
+	"gvisor.dev/gvisor/pkg/sentry/memmap"
+	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/syserror"
+)
+
+// GenericDirectoryFD implements vfs.FileDescriptionImpl for a generic directory
+// inode that uses OrderChildren to track child nodes. GenericDirectoryFD is not
+// compatible with dynamic directories.
+//
+// Note that GenericDirectoryFD holds a lock over OrderedChildren while calling
+// IterDirents callback. The IterDirents callback therefore cannot hash or
+// unhash children, or recursively call IterDirents on the same underlying
+// inode.
+//
+// Must be initialize with Init before first use.
+type GenericDirectoryFD struct {
+	vfs.FileDescriptionDefaultImpl
+	vfs.DirectoryFileDescriptionDefaultImpl
+
+	vfsfd    vfs.FileDescription
+	children *OrderedChildren
+	flags    uint32
+	off      int64
+}
+
+// Init initializes a GenericDirectoryFD.
+func (fd *GenericDirectoryFD) Init(m *vfs.Mount, d *vfs.Dentry, children *OrderedChildren, flags uint32) {
+	m.IncRef() // DecRef in vfs.FileDescription.vd.DecRef on final ref.
+	d.IncRef() // DecRef in vfs.FileDescription.vd.DecRef on final ref.
+	fd.children = children
+	fd.flags = flags
+	fd.vfsfd.Init(fd, m, d)
+}
+
+// VFSFileDescription returns a pointer to the vfs.FileDescription representing
+// this object.
+func (fd *GenericDirectoryFD) VFSFileDescription() *vfs.FileDescription {
+	return &fd.vfsfd
+}
+
+// ConfigureMMap implements vfs.FileDescriptionImpl.ConfigureMMap.
+func (fd *GenericDirectoryFD) ConfigureMMap(ctx context.Context, opts *memmap.MMapOpts) error {
+	return fd.FileDescriptionDefaultImpl.ConfigureMMap(ctx, opts)
+}
+
+// Read implmenets vfs.FileDescriptionImpl.Read.
+func (fd *GenericDirectoryFD) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) {
+	return fd.DirectoryFileDescriptionDefaultImpl.Read(ctx, dst, opts)
+}
+
+// PRead implmenets vfs.FileDescriptionImpl.PRead.
+func (fd *GenericDirectoryFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
+	return fd.DirectoryFileDescriptionDefaultImpl.PRead(ctx, dst, offset, opts)
+}
+
+// Write implements vfs.FileDescriptionImpl.Write.
+func (fd *GenericDirectoryFD) Write(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) {
+	return fd.DirectoryFileDescriptionDefaultImpl.Write(ctx, src, opts)
+}
+
+// PWrite implements vfs.FileDescriptionImpl.PWrite.
+func (fd *GenericDirectoryFD) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) {
+	return fd.DirectoryFileDescriptionDefaultImpl.PWrite(ctx, src, offset, opts)
+}
+
+// Release implements vfs.FileDecriptionImpl.Release.
+func (fd *GenericDirectoryFD) Release() {}
+
+func (fd *GenericDirectoryFD) filesystem() *vfs.Filesystem {
+	return fd.vfsfd.VirtualDentry().Mount().Filesystem()
+}
+
+func (fd *GenericDirectoryFD) inode() Inode {
+	return fd.vfsfd.VirtualDentry().Dentry().Impl().(*Dentry).inode
+}
+
+// IterDirents implements vfs.FileDecriptionImpl.IterDirents. IterDirents holds
+// o.mu when calling cb.
+func (fd *GenericDirectoryFD) IterDirents(ctx context.Context, cb vfs.IterDirentsCallback) error {
+	vfsFS := fd.filesystem()
+	fs := vfsFS.Impl().(*Filesystem)
+	vfsd := fd.vfsfd.VirtualDentry().Dentry()
+
+	fs.mu.Lock()
+	defer fs.mu.Unlock()
+
+	// Handle ".".
+	if fd.off == 0 {
+		stat := fd.inode().Stat(vfsFS)
+		dirent := vfs.Dirent{
+			Name:    ".",
+			Type:    linux.DT_DIR,
+			Ino:     stat.Ino,
+			NextOff: 1,
+		}
+		if !cb.Handle(dirent) {
+			return nil
+		}
+		fd.off++
+	}
+
+	// Handle "..".
+	if fd.off == 1 {
+		parentInode := vfsd.ParentOrSelf().Impl().(*Dentry).inode
+		stat := parentInode.Stat(vfsFS)
+		dirent := vfs.Dirent{
+			Name:    "..",
+			Type:    linux.FileMode(stat.Mode).DirentType(),
+			Ino:     stat.Ino,
+			NextOff: 2,
+		}
+		if !cb.Handle(dirent) {
+			return nil
+		}
+		fd.off++
+	}
+
+	// Handle static children.
+	fd.children.mu.RLock()
+	defer fd.children.mu.RUnlock()
+	// fd.off accounts for "." and "..", but fd.children do not track
+	// these.
+	childIdx := fd.off - 2
+	for it := fd.children.nthLocked(childIdx); it != nil; it = it.Next() {
+		inode := it.Dentry.Impl().(*Dentry).inode
+		stat := inode.Stat(vfsFS)
+		dirent := vfs.Dirent{
+			Name:    it.Name,
+			Type:    linux.FileMode(stat.Mode).DirentType(),
+			Ino:     stat.Ino,
+			NextOff: fd.off + 1,
+		}
+		if !cb.Handle(dirent) {
+			return nil
+		}
+		fd.off++
+	}
+
+	return nil
+}
+
+// Seek implements vfs.FileDecriptionImpl.Seek.
+func (fd *GenericDirectoryFD) Seek(ctx context.Context, offset int64, whence int32) (int64, error) {
+	fs := fd.filesystem().Impl().(*Filesystem)
+	fs.mu.Lock()
+	defer fs.mu.Unlock()
+
+	switch whence {
+	case linux.SEEK_SET:
+		// Use offset as given.
+	case linux.SEEK_CUR:
+		offset += fd.off
+	default:
+		return 0, syserror.EINVAL
+	}
+	if offset < 0 {
+		return 0, syserror.EINVAL
+	}
+	fd.off = offset
+	return offset, nil
+}
+
+// StatusFlags implements vfs.FileDescriptionImpl.StatusFlags.
+func (fd *GenericDirectoryFD) StatusFlags(ctx context.Context) (uint32, error) {
+	return fd.flags, nil
+}
+
+// SetStatusFlags implements vfs.FileDescriptionImpl.SetStatusFlags.
+func (fd *GenericDirectoryFD) SetStatusFlags(ctx context.Context, flags uint32) error {
+	// None of the flags settable by fcntl(F_SETFL) are supported, so this is a
+	// no-op.
+	return nil
+}
+
+// Stat implements vfs.FileDescriptionImpl.Stat.
+func (fd *GenericDirectoryFD) Stat(ctx context.Context, opts vfs.StatOptions) (linux.Statx, error) {
+	fs := fd.filesystem()
+	inode := fd.inode()
+	return inode.Stat(fs), nil
+}
+
+// SetStat implements vfs.FileDescriptionImpl.SetStat.
+func (fd *GenericDirectoryFD) SetStat(ctx context.Context, opts vfs.SetStatOptions) error {
+	fs := fd.filesystem()
+	inode := fd.vfsfd.VirtualDentry().Dentry().Impl().(*Dentry).inode
+	return inode.SetStat(fs, opts)
+}