1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
|
// 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 dev provides a filesystem with simple devices.
package dev
import (
"math"
"gvisor.dev/gvisor/pkg/sentry/context"
"gvisor.dev/gvisor/pkg/sentry/fs"
"gvisor.dev/gvisor/pkg/sentry/fs/ashmem"
"gvisor.dev/gvisor/pkg/sentry/fs/binder"
"gvisor.dev/gvisor/pkg/sentry/fs/ramfs"
"gvisor.dev/gvisor/pkg/sentry/fs/tmpfs"
"gvisor.dev/gvisor/pkg/sentry/usermem"
)
// Memory device numbers are from Linux's drivers/char/mem.c
const (
// Mem device major.
memDevMajor uint16 = 1
// Mem device minors.
nullDevMinor uint32 = 3
zeroDevMinor uint32 = 5
fullDevMinor uint32 = 7
randomDevMinor uint32 = 8
urandomDevMinor uint32 = 9
)
func newCharacterDevice(iops fs.InodeOperations, msrc *fs.MountSource) *fs.Inode {
return fs.NewInode(iops, msrc, fs.StableAttr{
DeviceID: devDevice.DeviceID(),
InodeID: devDevice.NextIno(),
BlockSize: usermem.PageSize,
Type: fs.CharacterDevice,
})
}
func newMemDevice(iops fs.InodeOperations, msrc *fs.MountSource, minor uint32) *fs.Inode {
return fs.NewInode(iops, msrc, fs.StableAttr{
DeviceID: devDevice.DeviceID(),
InodeID: devDevice.NextIno(),
BlockSize: usermem.PageSize,
Type: fs.CharacterDevice,
DeviceFileMajor: memDevMajor,
DeviceFileMinor: minor,
})
}
func newDirectory(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
iops := ramfs.NewDir(ctx, nil, fs.RootOwner, fs.FilePermsFromMode(0555))
return fs.NewInode(iops, msrc, fs.StableAttr{
DeviceID: devDevice.DeviceID(),
InodeID: devDevice.NextIno(),
BlockSize: usermem.PageSize,
Type: fs.Directory,
})
}
func newSymlink(ctx context.Context, target string, msrc *fs.MountSource) *fs.Inode {
iops := ramfs.NewSymlink(ctx, fs.RootOwner, target)
return fs.NewInode(iops, msrc, fs.StableAttr{
DeviceID: devDevice.DeviceID(),
InodeID: devDevice.NextIno(),
BlockSize: usermem.PageSize,
Type: fs.Symlink,
})
}
// New returns the root node of a device filesystem.
func New(ctx context.Context, msrc *fs.MountSource, binderEnabled bool, ashmemEnabled bool) *fs.Inode {
contents := map[string]*fs.Inode{
"fd": newSymlink(ctx, "/proc/self/fd", msrc),
"stdin": newSymlink(ctx, "/proc/self/fd/0", msrc),
"stdout": newSymlink(ctx, "/proc/self/fd/1", msrc),
"stderr": newSymlink(ctx, "/proc/self/fd/2", msrc),
"null": newMemDevice(newNullDevice(ctx, fs.RootOwner, 0666), msrc, nullDevMinor),
"zero": newMemDevice(newZeroDevice(ctx, fs.RootOwner, 0666), msrc, zeroDevMinor),
"full": newMemDevice(newFullDevice(ctx, fs.RootOwner, 0666), msrc, fullDevMinor),
// This is not as good as /dev/random in linux because go
// runtime uses sys_random and /dev/urandom internally.
// According to 'man 4 random', this will be sufficient unless
// application uses this to generate long-lived GPG/SSL/SSH
// keys.
"random": newMemDevice(newRandomDevice(ctx, fs.RootOwner, 0444), msrc, randomDevMinor),
"urandom": newMemDevice(newRandomDevice(ctx, fs.RootOwner, 0444), msrc, urandomDevMinor),
"shm": tmpfs.NewDir(ctx, nil, fs.RootOwner, fs.FilePermsFromMode(0777), msrc),
// A devpts is typically mounted at /dev/pts to provide
// pseudoterminal support. Place an empty directory there for
// the devpts to be mounted over.
"pts": newDirectory(ctx, msrc),
// Similarly, applications expect a ptmx device at /dev/ptmx
// connected to the terminals provided by /dev/pts/. Rather
// than creating a device directly (which requires a hairy
// lookup on open to determine if a devpts exists), just create
// a symlink to the ptmx provided by devpts. (The Linux devpts
// documentation recommends this).
//
// If no devpts is mounted, this will simply be a dangling
// symlink, which is fine.
"ptmx": newSymlink(ctx, "pts/ptmx", msrc),
}
if binderEnabled {
binder := binder.NewDevice(ctx, fs.RootOwner, fs.FilePermsFromMode(0666))
contents["binder"] = newCharacterDevice(binder, msrc)
}
if ashmemEnabled {
ashmem := ashmem.NewDevice(ctx, fs.RootOwner, fs.FilePermsFromMode(0666))
contents["ashmem"] = newCharacterDevice(ashmem, msrc)
}
iops := ramfs.NewDir(ctx, contents, fs.RootOwner, fs.FilePermsFromMode(0555))
return fs.NewInode(iops, msrc, fs.StableAttr{
DeviceID: devDevice.DeviceID(),
InodeID: devDevice.NextIno(),
BlockSize: usermem.PageSize,
Type: fs.Directory,
})
}
// readZeros implements fs.FileOperations.Read with infinite null bytes.
type readZeros struct{}
// Read implements fs.FileOperations.Read.
func (*readZeros) Read(ctx context.Context, file *fs.File, dst usermem.IOSequence, offset int64) (int64, error) {
return dst.ZeroOut(ctx, math.MaxInt64)
}
|
