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
|
// 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 signalfd provides an implementation of signal file descriptors.
package signalfd
import (
"sync"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/binary"
"gvisor.dev/gvisor/pkg/sentry/context"
"gvisor.dev/gvisor/pkg/sentry/fs"
"gvisor.dev/gvisor/pkg/sentry/fs/anon"
"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
"gvisor.dev/gvisor/pkg/sentry/kernel"
"gvisor.dev/gvisor/pkg/sentry/usermem"
"gvisor.dev/gvisor/pkg/syserror"
"gvisor.dev/gvisor/pkg/waiter"
)
// SignalOperations represent a file with signalfd semantics.
//
// +stateify savable
type SignalOperations struct {
fsutil.FileNoopRelease `state:"nosave"`
fsutil.FilePipeSeek `state:"nosave"`
fsutil.FileNotDirReaddir `state:"nosave"`
fsutil.FileNoIoctl `state:"nosave"`
fsutil.FileNoFsync `state:"nosave"`
fsutil.FileNoMMap `state:"nosave"`
fsutil.FileNoSplice `state:"nosave"`
fsutil.FileNoWrite `state:"nosave"`
fsutil.FileNoopFlush `state:"nosave"`
fsutil.FileUseInodeUnstableAttr `state:"nosave"`
// target is the original task target.
//
// The semantics here are a bit broken. Linux will always use current
// for all reads, regardless of where the signalfd originated. We can't
// do exactly that because we need to plumb the context through
// EventRegister in order to support proper blocking behavior. This
// will undoubtedly become very complicated quickly.
target *kernel.Task
// mu protects below.
mu sync.Mutex `state:"nosave"`
// mask is the signal mask. Protected by mu.
mask linux.SignalSet
}
// New creates a new signalfd object with the supplied mask.
func New(ctx context.Context, mask linux.SignalSet) (*fs.File, error) {
t := kernel.TaskFromContext(ctx)
if t == nil {
// No task context? Not valid.
return nil, syserror.EINVAL
}
// name matches fs/signalfd.c:signalfd4.
dirent := fs.NewDirent(ctx, anon.NewInode(ctx), "anon_inode:[signalfd]")
return fs.NewFile(ctx, dirent, fs.FileFlags{Read: true, Write: true}, &SignalOperations{
target: t,
mask: mask,
}), nil
}
// Release implements fs.FileOperations.Release.
func (s *SignalOperations) Release() {}
// Mask returns the signal mask.
func (s *SignalOperations) Mask() linux.SignalSet {
s.mu.Lock()
mask := s.mask
s.mu.Unlock()
return mask
}
// SetMask sets the signal mask.
func (s *SignalOperations) SetMask(mask linux.SignalSet) {
s.mu.Lock()
s.mask = mask
s.mu.Unlock()
}
// Read implements fs.FileOperations.Read.
func (s *SignalOperations) Read(ctx context.Context, _ *fs.File, dst usermem.IOSequence, _ int64) (int64, error) {
// Attempt to dequeue relevant signals.
info, err := s.target.Sigtimedwait(s.Mask(), 0)
if err != nil {
// There must be no signal available.
return 0, syserror.ErrWouldBlock
}
// Copy out the signal info using the specified format.
var buf [128]byte
binary.Marshal(buf[:0], usermem.ByteOrder, &linux.SignalfdSiginfo{
Signo: uint32(info.Signo),
Errno: info.Errno,
Code: info.Code,
PID: uint32(info.Pid()),
UID: uint32(info.Uid()),
Status: info.Status(),
Overrun: uint32(info.Overrun()),
Addr: info.Addr(),
})
n, err := dst.CopyOut(ctx, buf[:])
return int64(n), err
}
// Readiness implements waiter.Waitable.Readiness.
func (s *SignalOperations) Readiness(mask waiter.EventMask) waiter.EventMask {
if mask&waiter.EventIn != 0 && s.target.PendingSignals()&s.Mask() != 0 {
return waiter.EventIn // Pending signals.
}
return 0
}
// EventRegister implements waiter.Waitable.EventRegister.
func (s *SignalOperations) EventRegister(entry *waiter.Entry, _ waiter.EventMask) {
// Register for the signal set; ignore the passed events.
s.target.SignalRegister(entry, waiter.EventMask(s.Mask()))
}
// EventUnregister implements waiter.Waitable.EventUnregister.
func (s *SignalOperations) EventUnregister(entry *waiter.Entry) {
// Unregister the original entry.
s.target.SignalUnregister(entry)
}
|
