github.com/SagerNet/gvisor@v0.0.0-20210707092255-7731c139d75c/pkg/sentry/fs/sys/fs.go (about)

     1  // Copyright 2018 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package sys
    16  
    17  import (
    18  	"github.com/SagerNet/gvisor/pkg/context"
    19  	"github.com/SagerNet/gvisor/pkg/sentry/fs"
    20  )
    21  
    22  // filesystem is a sysfs.
    23  //
    24  // +stateify savable
    25  type filesystem struct{}
    26  
    27  var _ fs.Filesystem = (*filesystem)(nil)
    28  
    29  func init() {
    30  	fs.RegisterFilesystem(&filesystem{})
    31  }
    32  
    33  // FilesystemName is the name under which the filesystem is registered.
    34  // Name matches fs/sysfs/mount.c:sysfs_fs_type.name.
    35  const FilesystemName = "sysfs"
    36  
    37  // Name is the name of the file system.
    38  func (*filesystem) Name() string {
    39  	return FilesystemName
    40  }
    41  
    42  // AllowUserMount allows users to mount(2) this file system.
    43  func (*filesystem) AllowUserMount() bool {
    44  	return true
    45  }
    46  
    47  // AllowUserList allows this filesystem to be listed in /proc/filesystems.
    48  func (*filesystem) AllowUserList() bool {
    49  	return true
    50  }
    51  
    52  // Flags returns that there is nothing special about this file system.
    53  //
    54  // In Linux, sysfs returns FS_USERNS_VISIBLE | FS_USERNS_MOUNT, see fs/sysfs/mount.c.
    55  func (*filesystem) Flags() fs.FilesystemFlags {
    56  	return 0
    57  }
    58  
    59  // Mount returns a sysfs root which can be positioned in the vfs.
    60  func (f *filesystem) Mount(ctx context.Context, device string, flags fs.MountSourceFlags, data string, _ interface{}) (*fs.Inode, error) {
    61  	// device is always ignored.
    62  	// sysfs ignores data, see fs/sysfs/mount.c:sysfs_mount.
    63  
    64  	return New(ctx, fs.NewNonCachingMountSource(ctx, f, flags)), nil
    65  }