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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462
|
// 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 devpts
import (
"bytes"
"unicode/utf8"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/errors/linuxerr"
"gvisor.dev/gvisor/pkg/sentry/arch"
"gvisor.dev/gvisor/pkg/sentry/kernel"
"gvisor.dev/gvisor/pkg/sync"
"gvisor.dev/gvisor/pkg/usermem"
"gvisor.dev/gvisor/pkg/waiter"
)
const (
// canonMaxBytes is the number of bytes that fit into a single line of
// terminal input in canonical mode. This corresponds to N_TTY_BUF_SIZE
// in include/linux/tty.h.
canonMaxBytes = 4096
// nonCanonMaxBytes is the maximum number of bytes that can be read at
// a time in noncanonical mode.
nonCanonMaxBytes = canonMaxBytes - 1
spacesPerTab = 8
)
// lineDiscipline dictates how input and output are handled between the
// pseudoterminal (pty) master and replica. It can be configured to alter I/O,
// modify control characters (e.g. Ctrl-C for SIGINT), etc. The following man
// pages are good resources for how to affect the line discipline:
//
// - termios(3)
// - tty_ioctl(4)
//
// This file corresponds most closely to drivers/tty/n_tty.c.
//
// lineDiscipline has a simple structure but supports a multitude of options
// (see the above man pages). It consists of two queues of bytes: one from the
// terminal master to replica (the input queue) and one from replica to master
// (the output queue). When bytes are written to one end of the pty, the line
// discipline reads the bytes, modifies them or takes special action if
// required, and enqueues them to be read by the other end of the pty:
//
// input from terminal +-------------+ input to process (e.g. bash)
// +------------------------>| input queue |---------------------------+
// | (inputQueueWrite) +-------------+ (inputQueueRead) |
// | |
// | v
//
// masterFD replicaFD
//
// ^ |
// | |
// | output to terminal +--------------+ output from process |
// +------------------------| output queue |<--------------------------+
// (outputQueueRead) +--------------+ (outputQueueWrite)
//
// There is special handling for the ECHO option, where bytes written to the
// input queue are also output back to the terminal by being written to
// l.outQueue by the input queue transformer.
//
// Lock order:
//
// termiosMu
// inQueue.mu
// outQueue.mu
//
// +stateify savable
type lineDiscipline struct {
// sizeMu protects size.
sizeMu sync.Mutex `state:"nosave"`
// size is the terminal size (width and height).
size linux.WindowSize
// inQueue is the input queue of the terminal.
inQueue queue
// outQueue is the output queue of the terminal.
outQueue queue
// termiosMu protects termios.
termiosMu sync.RWMutex `state:"nosave"`
// termios is the terminal configuration used by the lineDiscipline.
termios linux.KernelTermios
// column is the location in a row of the cursor. This is important for
// handling certain special characters like backspace.
column int
// masterWaiter is used to wait on the master end of the TTY.
masterWaiter waiter.Queue
// replicaWaiter is used to wait on the replica end of the TTY.
replicaWaiter waiter.Queue
}
func newLineDiscipline(termios linux.KernelTermios) *lineDiscipline {
ld := lineDiscipline{termios: termios}
ld.inQueue.transformer = &inputQueueTransformer{}
ld.outQueue.transformer = &outputQueueTransformer{}
return &ld
}
// getTermios gets the linux.Termios for the tty.
func (l *lineDiscipline) getTermios(task *kernel.Task, args arch.SyscallArguments) (uintptr, error) {
l.termiosMu.RLock()
defer l.termiosMu.RUnlock()
// We must copy a Termios struct, not KernelTermios.
t := l.termios.ToTermios()
_, err := t.CopyOut(task, args[2].Pointer())
return 0, err
}
// setTermios sets a linux.Termios for the tty.
func (l *lineDiscipline) setTermios(task *kernel.Task, args arch.SyscallArguments) (uintptr, error) {
l.termiosMu.Lock()
oldCanonEnabled := l.termios.LEnabled(linux.ICANON)
// We must copy a Termios struct, not KernelTermios.
var t linux.Termios
_, err := t.CopyIn(task, args[2].Pointer())
l.termios.FromTermios(t)
// If canonical mode is turned off, move bytes from inQueue's wait
// buffer to its read buffer. Anything already in the read buffer is
// now readable.
if oldCanonEnabled && !l.termios.LEnabled(linux.ICANON) {
l.inQueue.mu.Lock()
l.inQueue.pushWaitBufLocked(l)
l.inQueue.readable = true
l.inQueue.mu.Unlock()
l.termiosMu.Unlock()
l.replicaWaiter.Notify(waiter.ReadableEvents)
} else {
l.termiosMu.Unlock()
}
return 0, err
}
func (l *lineDiscipline) windowSize(t *kernel.Task, args arch.SyscallArguments) error {
l.sizeMu.Lock()
defer l.sizeMu.Unlock()
_, err := l.size.CopyOut(t, args[2].Pointer())
return err
}
func (l *lineDiscipline) setWindowSize(t *kernel.Task, args arch.SyscallArguments) error {
l.sizeMu.Lock()
defer l.sizeMu.Unlock()
_, err := l.size.CopyIn(t, args[2].Pointer())
return err
}
func (l *lineDiscipline) masterReadiness() waiter.EventMask {
// We don't have to lock a termios because the default master termios
// is immutable.
return l.inQueue.writeReadiness(&linux.MasterTermios) | l.outQueue.readReadiness(&linux.MasterTermios)
}
func (l *lineDiscipline) replicaReadiness() waiter.EventMask {
l.termiosMu.RLock()
defer l.termiosMu.RUnlock()
return l.outQueue.writeReadiness(&l.termios) | l.inQueue.readReadiness(&l.termios)
}
func (l *lineDiscipline) inputQueueReadSize(t *kernel.Task, io usermem.IO, args arch.SyscallArguments) error {
return l.inQueue.readableSize(t, io, args)
}
func (l *lineDiscipline) inputQueueRead(ctx context.Context, dst usermem.IOSequence) (int64, error) {
l.termiosMu.RLock()
n, pushed, notifyEcho, err := l.inQueue.read(ctx, dst, l)
l.termiosMu.RUnlock()
if err != nil {
return 0, err
}
if n > 0 {
if notifyEcho {
l.masterWaiter.Notify(waiter.ReadableEvents | waiter.WritableEvents)
} else {
l.masterWaiter.Notify(waiter.WritableEvents)
}
if pushed {
l.replicaWaiter.Notify(waiter.ReadableEvents)
}
return n, nil
} else if notifyEcho {
l.masterWaiter.Notify(waiter.ReadableEvents)
}
return 0, linuxerr.ErrWouldBlock
}
func (l *lineDiscipline) inputQueueWrite(ctx context.Context, src usermem.IOSequence) (int64, error) {
l.termiosMu.RLock()
n, notifyEcho, err := l.inQueue.write(ctx, src, l)
l.termiosMu.RUnlock()
if err != nil {
return 0, err
}
if notifyEcho {
l.masterWaiter.Notify(waiter.ReadableEvents)
}
if n > 0 {
l.replicaWaiter.Notify(waiter.ReadableEvents)
return n, nil
}
return 0, linuxerr.ErrWouldBlock
}
func (l *lineDiscipline) outputQueueReadSize(t *kernel.Task, io usermem.IO, args arch.SyscallArguments) error {
return l.outQueue.readableSize(t, io, args)
}
func (l *lineDiscipline) outputQueueRead(ctx context.Context, dst usermem.IOSequence) (int64, error) {
l.termiosMu.RLock()
// Ignore notifyEcho, as it cannot happen when reading from the output queue.
n, pushed, _, err := l.outQueue.read(ctx, dst, l)
l.termiosMu.RUnlock()
if err != nil {
return 0, err
}
if n > 0 {
l.replicaWaiter.Notify(waiter.WritableEvents)
if pushed {
l.masterWaiter.Notify(waiter.ReadableEvents)
}
return n, nil
}
return 0, linuxerr.ErrWouldBlock
}
func (l *lineDiscipline) outputQueueWrite(ctx context.Context, src usermem.IOSequence) (int64, error) {
l.termiosMu.RLock()
// Ignore notifyEcho, as it cannot happen when writing to the output queue.
n, _, err := l.outQueue.write(ctx, src, l)
l.termiosMu.RUnlock()
if err != nil {
return 0, err
}
if n > 0 {
l.masterWaiter.Notify(waiter.ReadableEvents)
return n, nil
}
return 0, linuxerr.ErrWouldBlock
}
// transformer is a helper interface to make it easier to stateify queue.
type transformer interface {
// transform functions require queue's mutex to be held.
// The boolean indicates whether there was any echoed bytes.
transform(*lineDiscipline, *queue, []byte) (int, bool)
}
// outputQueueTransformer implements transformer. It performs line discipline
// transformations on the output queue.
//
// +stateify savable
type outputQueueTransformer struct{}
// transform does output processing for one end of the pty. See
// drivers/tty/n_tty.c:do_output_char for an analogous kernel function.
//
// Preconditions:
// - l.termiosMu must be held for reading.
// - q.mu must be held.
func (*outputQueueTransformer) transform(l *lineDiscipline, q *queue, buf []byte) (int, bool) {
// transformOutput is effectively always in noncanonical mode, as the
// master termios never has ICANON set.
if !l.termios.OEnabled(linux.OPOST) {
q.readBuf = append(q.readBuf, buf...)
if len(q.readBuf) > 0 {
q.readable = true
}
return len(buf), false
}
var ret int
for len(buf) > 0 {
size := l.peek(buf)
cBytes := append([]byte{}, buf[:size]...)
ret += size
buf = buf[size:]
// We're guaranteed that cBytes has at least one element.
switch cBytes[0] {
case '\n':
if l.termios.OEnabled(linux.ONLRET) {
l.column = 0
}
if l.termios.OEnabled(linux.ONLCR) {
q.readBuf = append(q.readBuf, '\r', '\n')
continue
}
case '\r':
if l.termios.OEnabled(linux.ONOCR) && l.column == 0 {
continue
}
if l.termios.OEnabled(linux.OCRNL) {
cBytes[0] = '\n'
if l.termios.OEnabled(linux.ONLRET) {
l.column = 0
}
break
}
l.column = 0
case '\t':
spaces := spacesPerTab - l.column%spacesPerTab
if l.termios.OutputFlags&linux.TABDLY == linux.XTABS {
l.column += spaces
q.readBuf = append(q.readBuf, bytes.Repeat([]byte{' '}, spacesPerTab)...)
continue
}
l.column += spaces
case '\b':
if l.column > 0 {
l.column--
}
default:
l.column++
}
q.readBuf = append(q.readBuf, cBytes...)
}
if len(q.readBuf) > 0 {
q.readable = true
}
return ret, false
}
// inputQueueTransformer implements transformer. It performs line discipline
// transformations on the input queue.
//
// +stateify savable
type inputQueueTransformer struct{}
// transform does input processing for one end of the pty. Characters read are
// transformed according to flags set in the termios struct. See
// drivers/tty/n_tty.c:n_tty_receive_char_special for an analogous kernel
// function.
// It returns an extra boolean indicating whether any characters need to be
// echoed, in which case we need to notify readers.
//
// Preconditions:
// - l.termiosMu must be held for reading.
// - q.mu must be held.
func (*inputQueueTransformer) transform(l *lineDiscipline, q *queue, buf []byte) (int, bool) {
// If there's a line waiting to be read in canonical mode, don't write
// anything else to the read buffer.
if l.termios.LEnabled(linux.ICANON) && q.readable {
return 0, false
}
maxBytes := nonCanonMaxBytes
if l.termios.LEnabled(linux.ICANON) {
maxBytes = canonMaxBytes
}
var ret int
var notifyEcho bool
for len(buf) > 0 && len(q.readBuf) < canonMaxBytes {
size := l.peek(buf)
cBytes := append([]byte{}, buf[:size]...)
// We're guaranteed that cBytes has at least one element.
switch cBytes[0] {
case '\r':
if l.termios.IEnabled(linux.IGNCR) {
buf = buf[size:]
ret += size
continue
}
if l.termios.IEnabled(linux.ICRNL) {
cBytes[0] = '\n'
}
case '\n':
if l.termios.IEnabled(linux.INLCR) {
cBytes[0] = '\r'
}
}
// In canonical mode, we discard non-terminating characters
// after the first 4095.
if l.shouldDiscard(q, cBytes) {
buf = buf[size:]
ret += size
continue
}
// Stop if the buffer would be overfilled.
if len(q.readBuf)+size > maxBytes {
break
}
buf = buf[size:]
ret += size
// If we get EOF, make the buffer available for reading.
if l.termios.LEnabled(linux.ICANON) && l.termios.IsEOF(cBytes[0]) {
q.readable = true
break
}
q.readBuf = append(q.readBuf, cBytes...)
// Anything written to the readBuf will have to be echoed.
if l.termios.LEnabled(linux.ECHO) {
l.outQueue.writeBytes(cBytes, l)
notifyEcho = true
}
// If we finish a line, make it available for reading.
if l.termios.LEnabled(linux.ICANON) && l.termios.IsTerminating(cBytes) {
q.readable = true
break
}
}
// In noncanonical mode, everything is readable.
if !l.termios.LEnabled(linux.ICANON) && len(q.readBuf) > 0 {
q.readable = true
}
return ret, notifyEcho
}
// shouldDiscard returns whether c should be discarded. In canonical mode, if
// too many bytes are enqueued, we keep reading input and discarding it until
// we find a terminating character. Signal/echo processing still occurs.
//
// Precondition:
// - l.termiosMu must be held for reading.
// - q.mu must be held.
func (l *lineDiscipline) shouldDiscard(q *queue, cBytes []byte) bool {
return l.termios.LEnabled(linux.ICANON) && len(q.readBuf)+len(cBytes) >= canonMaxBytes && !l.termios.IsTerminating(cBytes)
}
// peek returns the size in bytes of the next character to process. As long as
// b isn't empty, peek returns a value of at least 1.
func (l *lineDiscipline) peek(b []byte) int {
size := 1
// If UTF-8 support is enabled, runes might be multiple bytes.
if l.termios.IEnabled(linux.IUTF8) {
_, size = utf8.DecodeRune(b)
}
return size
}
|