github.com/SagerNet/gvisor@v0.0.0-20210707092255-7731c139d75c/pkg/sentry/fs/dev/null.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 dev
    16  
    17  import (
    18  	"github.com/SagerNet/gvisor/pkg/abi/linux"
    19  	"github.com/SagerNet/gvisor/pkg/context"
    20  	"github.com/SagerNet/gvisor/pkg/sentry/fs"
    21  	"github.com/SagerNet/gvisor/pkg/sentry/fs/fsutil"
    22  	"github.com/SagerNet/gvisor/pkg/sentry/memmap"
    23  	"github.com/SagerNet/gvisor/pkg/sentry/mm"
    24  	"github.com/SagerNet/gvisor/pkg/sentry/pgalloc"
    25  	"github.com/SagerNet/gvisor/pkg/waiter"
    26  )
    27  
    28  // +stateify savable
    29  type nullDevice struct {
    30  	fsutil.InodeGenericChecker       `state:"nosave"`
    31  	fsutil.InodeNoExtendedAttributes `state:"nosave"`
    32  	fsutil.InodeNoopAllocate         `state:"nosave"`
    33  	fsutil.InodeNoopRelease          `state:"nosave"`
    34  	fsutil.InodeNoopTruncate         `state:"nosave"`
    35  	fsutil.InodeNoopWriteOut         `state:"nosave"`
    36  	fsutil.InodeNotDirectory         `state:"nosave"`
    37  	fsutil.InodeNotMappable          `state:"nosave"`
    38  	fsutil.InodeNotSocket            `state:"nosave"`
    39  	fsutil.InodeNotSymlink           `state:"nosave"`
    40  	fsutil.InodeVirtual              `state:"nosave"`
    41  
    42  	fsutil.InodeSimpleAttributes
    43  }
    44  
    45  var _ fs.InodeOperations = (*nullDevice)(nil)
    46  
    47  func newNullDevice(ctx context.Context, owner fs.FileOwner, mode linux.FileMode) *nullDevice {
    48  	n := &nullDevice{
    49  		InodeSimpleAttributes: fsutil.NewInodeSimpleAttributes(ctx, owner, fs.FilePermsFromMode(mode), linux.TMPFS_MAGIC),
    50  	}
    51  	return n
    52  }
    53  
    54  // GetFile implements fs.FileOperations.GetFile.
    55  func (n *nullDevice) GetFile(ctx context.Context, dirent *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
    56  	flags.Pread = true
    57  	flags.Pwrite = true
    58  
    59  	return fs.NewFile(ctx, dirent, flags, &nullFileOperations{}), nil
    60  }
    61  
    62  // +stateify savable
    63  type nullFileOperations struct {
    64  	fsutil.FileGenericSeek          `state:"nosave"`
    65  	fsutil.FileNoIoctl              `state:"nosave"`
    66  	fsutil.FileNoMMap               `state:"nosave"`
    67  	fsutil.FileNoSplice             `state:"nosave"`
    68  	fsutil.FileNoopFlush            `state:"nosave"`
    69  	fsutil.FileNoopFsync            `state:"nosave"`
    70  	fsutil.FileNoopRead             `state:"nosave"`
    71  	fsutil.FileNoopRelease          `state:"nosave"`
    72  	fsutil.FileNoopWrite            `state:"nosave"`
    73  	fsutil.FileNotDirReaddir        `state:"nosave"`
    74  	fsutil.FileUseInodeUnstableAttr `state:"nosave"`
    75  	waiter.AlwaysReady              `state:"nosave"`
    76  }
    77  
    78  var _ fs.FileOperations = (*nullFileOperations)(nil)
    79  
    80  // +stateify savable
    81  type zeroDevice struct {
    82  	nullDevice
    83  }
    84  
    85  var _ fs.InodeOperations = (*zeroDevice)(nil)
    86  
    87  func newZeroDevice(ctx context.Context, owner fs.FileOwner, mode linux.FileMode) *zeroDevice {
    88  	zd := &zeroDevice{
    89  		nullDevice: nullDevice{
    90  			InodeSimpleAttributes: fsutil.NewInodeSimpleAttributes(ctx, owner, fs.FilePermsFromMode(mode), linux.TMPFS_MAGIC),
    91  		},
    92  	}
    93  	return zd
    94  }
    95  
    96  // GetFile implements fs.FileOperations.GetFile.
    97  func (zd *zeroDevice) GetFile(ctx context.Context, dirent *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
    98  	flags.Pread = true
    99  	flags.Pwrite = true
   100  	flags.NonSeekable = true
   101  
   102  	return fs.NewFile(ctx, dirent, flags, &zeroFileOperations{}), nil
   103  }
   104  
   105  // +stateify savable
   106  type zeroFileOperations struct {
   107  	fsutil.FileGenericSeek          `state:"nosave"`
   108  	fsutil.FileNoIoctl              `state:"nosave"`
   109  	fsutil.FileNoSplice             `state:"nosave"`
   110  	fsutil.FileNoopFlush            `state:"nosave"`
   111  	fsutil.FileNoopFsync            `state:"nosave"`
   112  	fsutil.FileNoopRelease          `state:"nosave"`
   113  	fsutil.FileNoopWrite            `state:"nosave"`
   114  	fsutil.FileNotDirReaddir        `state:"nosave"`
   115  	fsutil.FileUseInodeUnstableAttr `state:"nosave"`
   116  	waiter.AlwaysReady              `state:"nosave"`
   117  	readZeros                       `state:"nosave"`
   118  }
   119  
   120  var _ fs.FileOperations = (*zeroFileOperations)(nil)
   121  
   122  // ConfigureMMap implements fs.FileOperations.ConfigureMMap.
   123  func (*zeroFileOperations) ConfigureMMap(ctx context.Context, file *fs.File, opts *memmap.MMapOpts) error {
   124  	m, err := mm.NewSharedAnonMappable(opts.Length, pgalloc.MemoryFileProviderFromContext(ctx))
   125  	if err != nil {
   126  		return err
   127  	}
   128  	opts.MappingIdentity = m
   129  	opts.Mappable = m
   130  	return nil
   131  }