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// 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/context"
"gvisor.dev/gvisor/pkg/sentry/memmap"
"gvisor.dev/gvisor/pkg/sentry/vfs"
"gvisor.dev/gvisor/pkg/syserror"
"gvisor.dev/gvisor/pkg/usermem"
)
// 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
off int64
}
// Init initializes a GenericDirectoryFD.
func (fd *GenericDirectoryFD) Init(m *vfs.Mount, d *vfs.Dentry, children *OrderedChildren, opts *vfs.OpenOptions) error {
if vfs.AccessTypesForOpenFlags(opts)&vfs.MayWrite != 0 {
// Can't open directories for writing.
return syserror.EISDIR
}
if err := fd.vfsfd.Init(fd, opts.Flags, m, d, &vfs.FileDescriptionOptions{}); err != nil {
return err
}
fd.children = children
return nil
}
// 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++
}
var err error
relOffset := fd.off - int64(len(fd.children.set)) - 2
fd.off, err = fd.inode().IterDirents(ctx, cb, fd.off, relOffset)
return err
}
// 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
}
// 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)
}
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