Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame^] | 1 | /* |
| 2 | * linux/drivers/char/pty.c |
| 3 | * |
| 4 | * Copyright (C) 1991, 1992 Linus Torvalds |
| 5 | * |
| 6 | * Added support for a Unix98-style ptmx device. |
| 7 | * -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998 |
| 8 | * Added TTY_DO_WRITE_WAKEUP to enable n_tty to send POLL_OUT to |
| 9 | * waiting writers -- Sapan Bhatia <sapan@corewars.org> |
| 10 | * |
| 11 | * |
| 12 | */ |
| 13 | |
| 14 | #include <linux/config.h> |
| 15 | #include <linux/module.h> /* For EXPORT_SYMBOL */ |
| 16 | |
| 17 | #include <linux/errno.h> |
| 18 | #include <linux/sched.h> |
| 19 | #include <linux/interrupt.h> |
| 20 | #include <linux/tty.h> |
| 21 | #include <linux/tty_flip.h> |
| 22 | #include <linux/fcntl.h> |
| 23 | #include <linux/string.h> |
| 24 | #include <linux/major.h> |
| 25 | #include <linux/mm.h> |
| 26 | #include <linux/init.h> |
| 27 | #include <linux/devfs_fs_kernel.h> |
| 28 | #include <linux/sysctl.h> |
| 29 | |
| 30 | #include <asm/uaccess.h> |
| 31 | #include <asm/system.h> |
| 32 | #include <linux/bitops.h> |
| 33 | #include <linux/devpts_fs.h> |
| 34 | |
| 35 | /* These are global because they are accessed in tty_io.c */ |
| 36 | #ifdef CONFIG_UNIX98_PTYS |
| 37 | struct tty_driver *ptm_driver; |
| 38 | static struct tty_driver *pts_driver; |
| 39 | #endif |
| 40 | |
| 41 | static void pty_close(struct tty_struct * tty, struct file * filp) |
| 42 | { |
| 43 | if (!tty) |
| 44 | return; |
| 45 | if (tty->driver->subtype == PTY_TYPE_MASTER) { |
| 46 | if (tty->count > 1) |
| 47 | printk("master pty_close: count = %d!!\n", tty->count); |
| 48 | } else { |
| 49 | if (tty->count > 2) |
| 50 | return; |
| 51 | } |
| 52 | wake_up_interruptible(&tty->read_wait); |
| 53 | wake_up_interruptible(&tty->write_wait); |
| 54 | tty->packet = 0; |
| 55 | if (!tty->link) |
| 56 | return; |
| 57 | tty->link->packet = 0; |
| 58 | set_bit(TTY_OTHER_CLOSED, &tty->link->flags); |
| 59 | wake_up_interruptible(&tty->link->read_wait); |
| 60 | wake_up_interruptible(&tty->link->write_wait); |
| 61 | if (tty->driver->subtype == PTY_TYPE_MASTER) { |
| 62 | set_bit(TTY_OTHER_CLOSED, &tty->flags); |
| 63 | #ifdef CONFIG_UNIX98_PTYS |
| 64 | if (tty->driver == ptm_driver) |
| 65 | devpts_pty_kill(tty->index); |
| 66 | #endif |
| 67 | tty_vhangup(tty->link); |
| 68 | } |
| 69 | } |
| 70 | |
| 71 | /* |
| 72 | * The unthrottle routine is called by the line discipline to signal |
| 73 | * that it can receive more characters. For PTY's, the TTY_THROTTLED |
| 74 | * flag is always set, to force the line discipline to always call the |
| 75 | * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE |
| 76 | * characters in the queue. This is necessary since each time this |
| 77 | * happens, we need to wake up any sleeping processes that could be |
| 78 | * (1) trying to send data to the pty, or (2) waiting in wait_until_sent() |
| 79 | * for the pty buffer to be drained. |
| 80 | */ |
| 81 | static void pty_unthrottle(struct tty_struct * tty) |
| 82 | { |
| 83 | struct tty_struct *o_tty = tty->link; |
| 84 | |
| 85 | if (!o_tty) |
| 86 | return; |
| 87 | |
| 88 | tty_wakeup(o_tty); |
| 89 | set_bit(TTY_THROTTLED, &tty->flags); |
| 90 | } |
| 91 | |
| 92 | /* |
| 93 | * WSH 05/24/97: modified to |
| 94 | * (1) use space in tty->flip instead of a shared temp buffer |
| 95 | * The flip buffers aren't being used for a pty, so there's lots |
| 96 | * of space available. The buffer is protected by a per-pty |
| 97 | * semaphore that should almost never come under contention. |
| 98 | * (2) avoid redundant copying for cases where count >> receive_room |
| 99 | * N.B. Calls from user space may now return an error code instead of |
| 100 | * a count. |
| 101 | * |
| 102 | * FIXME: Our pty_write method is called with our ldisc lock held but |
| 103 | * not our partners. We can't just take the other one blindly without |
| 104 | * risking deadlocks. There is also the small matter of TTY_DONT_FLIP |
| 105 | */ |
| 106 | static int pty_write(struct tty_struct * tty, const unsigned char *buf, int count) |
| 107 | { |
| 108 | struct tty_struct *to = tty->link; |
| 109 | int c; |
| 110 | |
| 111 | if (!to || tty->stopped) |
| 112 | return 0; |
| 113 | |
| 114 | c = to->ldisc.receive_room(to); |
| 115 | if (c > count) |
| 116 | c = count; |
| 117 | to->ldisc.receive_buf(to, buf, NULL, c); |
| 118 | |
| 119 | return c; |
| 120 | } |
| 121 | |
| 122 | static int pty_write_room(struct tty_struct *tty) |
| 123 | { |
| 124 | struct tty_struct *to = tty->link; |
| 125 | |
| 126 | if (!to || tty->stopped) |
| 127 | return 0; |
| 128 | |
| 129 | return to->ldisc.receive_room(to); |
| 130 | } |
| 131 | |
| 132 | /* |
| 133 | * WSH 05/24/97: Modified for asymmetric MASTER/SLAVE behavior |
| 134 | * The chars_in_buffer() value is used by the ldisc select() function |
| 135 | * to hold off writing when chars_in_buffer > WAKEUP_CHARS (== 256). |
| 136 | * The pty driver chars_in_buffer() Master/Slave must behave differently: |
| 137 | * |
| 138 | * The Master side needs to allow typed-ahead commands to accumulate |
| 139 | * while being canonicalized, so we report "our buffer" as empty until |
| 140 | * some threshold is reached, and then report the count. (Any count > |
| 141 | * WAKEUP_CHARS is regarded by select() as "full".) To avoid deadlock |
| 142 | * the count returned must be 0 if no canonical data is available to be |
| 143 | * read. (The N_TTY ldisc.chars_in_buffer now knows this.) |
| 144 | * |
| 145 | * The Slave side passes all characters in raw mode to the Master side's |
| 146 | * buffer where they can be read immediately, so in this case we can |
| 147 | * return the true count in the buffer. |
| 148 | */ |
| 149 | static int pty_chars_in_buffer(struct tty_struct *tty) |
| 150 | { |
| 151 | struct tty_struct *to = tty->link; |
| 152 | ssize_t (*chars_in_buffer)(struct tty_struct *); |
| 153 | int count; |
| 154 | |
| 155 | /* We should get the line discipline lock for "tty->link" */ |
| 156 | if (!to || !(chars_in_buffer = to->ldisc.chars_in_buffer)) |
| 157 | return 0; |
| 158 | |
| 159 | /* The ldisc must report 0 if no characters available to be read */ |
| 160 | count = chars_in_buffer(to); |
| 161 | |
| 162 | if (tty->driver->subtype == PTY_TYPE_SLAVE) return count; |
| 163 | |
| 164 | /* Master side driver ... if the other side's read buffer is less than |
| 165 | * half full, return 0 to allow writers to proceed; otherwise return |
| 166 | * the count. This leaves a comfortable margin to avoid overflow, |
| 167 | * and still allows half a buffer's worth of typed-ahead commands. |
| 168 | */ |
| 169 | return ((count < N_TTY_BUF_SIZE/2) ? 0 : count); |
| 170 | } |
| 171 | |
| 172 | /* Set the lock flag on a pty */ |
| 173 | static int pty_set_lock(struct tty_struct *tty, int __user * arg) |
| 174 | { |
| 175 | int val; |
| 176 | if (get_user(val,arg)) |
| 177 | return -EFAULT; |
| 178 | if (val) |
| 179 | set_bit(TTY_PTY_LOCK, &tty->flags); |
| 180 | else |
| 181 | clear_bit(TTY_PTY_LOCK, &tty->flags); |
| 182 | return 0; |
| 183 | } |
| 184 | |
| 185 | static void pty_flush_buffer(struct tty_struct *tty) |
| 186 | { |
| 187 | struct tty_struct *to = tty->link; |
| 188 | |
| 189 | if (!to) |
| 190 | return; |
| 191 | |
| 192 | if (to->ldisc.flush_buffer) |
| 193 | to->ldisc.flush_buffer(to); |
| 194 | |
| 195 | if (to->packet) { |
| 196 | tty->ctrl_status |= TIOCPKT_FLUSHWRITE; |
| 197 | wake_up_interruptible(&to->read_wait); |
| 198 | } |
| 199 | } |
| 200 | |
| 201 | static int pty_open(struct tty_struct *tty, struct file * filp) |
| 202 | { |
| 203 | int retval = -ENODEV; |
| 204 | |
| 205 | if (!tty || !tty->link) |
| 206 | goto out; |
| 207 | |
| 208 | retval = -EIO; |
| 209 | if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) |
| 210 | goto out; |
| 211 | if (test_bit(TTY_PTY_LOCK, &tty->link->flags)) |
| 212 | goto out; |
| 213 | if (tty->link->count != 1) |
| 214 | goto out; |
| 215 | |
| 216 | clear_bit(TTY_OTHER_CLOSED, &tty->link->flags); |
| 217 | set_bit(TTY_THROTTLED, &tty->flags); |
| 218 | set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); |
| 219 | retval = 0; |
| 220 | out: |
| 221 | return retval; |
| 222 | } |
| 223 | |
| 224 | static void pty_set_termios(struct tty_struct *tty, struct termios *old_termios) |
| 225 | { |
| 226 | tty->termios->c_cflag &= ~(CSIZE | PARENB); |
| 227 | tty->termios->c_cflag |= (CS8 | CREAD); |
| 228 | } |
| 229 | |
| 230 | static struct tty_operations pty_ops = { |
| 231 | .open = pty_open, |
| 232 | .close = pty_close, |
| 233 | .write = pty_write, |
| 234 | .write_room = pty_write_room, |
| 235 | .flush_buffer = pty_flush_buffer, |
| 236 | .chars_in_buffer = pty_chars_in_buffer, |
| 237 | .unthrottle = pty_unthrottle, |
| 238 | .set_termios = pty_set_termios, |
| 239 | }; |
| 240 | |
| 241 | /* Traditional BSD devices */ |
| 242 | #ifdef CONFIG_LEGACY_PTYS |
| 243 | static struct tty_driver *pty_driver, *pty_slave_driver; |
| 244 | |
| 245 | static int pty_bsd_ioctl(struct tty_struct *tty, struct file *file, |
| 246 | unsigned int cmd, unsigned long arg) |
| 247 | { |
| 248 | switch (cmd) { |
| 249 | case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */ |
| 250 | return pty_set_lock(tty, (int __user *) arg); |
| 251 | } |
| 252 | return -ENOIOCTLCMD; |
| 253 | } |
| 254 | |
| 255 | static void __init legacy_pty_init(void) |
| 256 | { |
| 257 | |
| 258 | pty_driver = alloc_tty_driver(NR_PTYS); |
| 259 | if (!pty_driver) |
| 260 | panic("Couldn't allocate pty driver"); |
| 261 | |
| 262 | pty_slave_driver = alloc_tty_driver(NR_PTYS); |
| 263 | if (!pty_slave_driver) |
| 264 | panic("Couldn't allocate pty slave driver"); |
| 265 | |
| 266 | pty_driver->owner = THIS_MODULE; |
| 267 | pty_driver->driver_name = "pty_master"; |
| 268 | pty_driver->name = "pty"; |
| 269 | pty_driver->devfs_name = "pty/m"; |
| 270 | pty_driver->major = PTY_MASTER_MAJOR; |
| 271 | pty_driver->minor_start = 0; |
| 272 | pty_driver->type = TTY_DRIVER_TYPE_PTY; |
| 273 | pty_driver->subtype = PTY_TYPE_MASTER; |
| 274 | pty_driver->init_termios = tty_std_termios; |
| 275 | pty_driver->init_termios.c_iflag = 0; |
| 276 | pty_driver->init_termios.c_oflag = 0; |
| 277 | pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD; |
| 278 | pty_driver->init_termios.c_lflag = 0; |
| 279 | pty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW; |
| 280 | pty_driver->other = pty_slave_driver; |
| 281 | tty_set_operations(pty_driver, &pty_ops); |
| 282 | pty_driver->ioctl = pty_bsd_ioctl; |
| 283 | |
| 284 | pty_slave_driver->owner = THIS_MODULE; |
| 285 | pty_slave_driver->driver_name = "pty_slave"; |
| 286 | pty_slave_driver->name = "ttyp"; |
| 287 | pty_slave_driver->devfs_name = "pty/s"; |
| 288 | pty_slave_driver->major = PTY_SLAVE_MAJOR; |
| 289 | pty_slave_driver->minor_start = 0; |
| 290 | pty_slave_driver->type = TTY_DRIVER_TYPE_PTY; |
| 291 | pty_slave_driver->subtype = PTY_TYPE_SLAVE; |
| 292 | pty_slave_driver->init_termios = tty_std_termios; |
| 293 | pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD; |
| 294 | pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS | |
| 295 | TTY_DRIVER_REAL_RAW; |
| 296 | pty_slave_driver->other = pty_driver; |
| 297 | tty_set_operations(pty_slave_driver, &pty_ops); |
| 298 | |
| 299 | if (tty_register_driver(pty_driver)) |
| 300 | panic("Couldn't register pty driver"); |
| 301 | if (tty_register_driver(pty_slave_driver)) |
| 302 | panic("Couldn't register pty slave driver"); |
| 303 | } |
| 304 | #else |
| 305 | static inline void legacy_pty_init(void) { } |
| 306 | #endif |
| 307 | |
| 308 | /* Unix98 devices */ |
| 309 | #ifdef CONFIG_UNIX98_PTYS |
| 310 | /* |
| 311 | * sysctl support for setting limits on the number of Unix98 ptys allocated. |
| 312 | * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly. |
| 313 | */ |
| 314 | int pty_limit = NR_UNIX98_PTY_DEFAULT; |
| 315 | static int pty_limit_min = 0; |
| 316 | static int pty_limit_max = NR_UNIX98_PTY_MAX; |
| 317 | |
| 318 | ctl_table pty_table[] = { |
| 319 | { |
| 320 | .ctl_name = PTY_MAX, |
| 321 | .procname = "max", |
| 322 | .maxlen = sizeof(int), |
| 323 | .mode = 0644, |
| 324 | .data = &pty_limit, |
| 325 | .proc_handler = &proc_dointvec_minmax, |
| 326 | .strategy = &sysctl_intvec, |
| 327 | .extra1 = &pty_limit_min, |
| 328 | .extra2 = &pty_limit_max, |
| 329 | }, { |
| 330 | .ctl_name = PTY_NR, |
| 331 | .procname = "nr", |
| 332 | .maxlen = sizeof(int), |
| 333 | .mode = 0444, |
| 334 | .proc_handler = &proc_dointvec, |
| 335 | }, { |
| 336 | .ctl_name = 0 |
| 337 | } |
| 338 | }; |
| 339 | |
| 340 | static int pty_unix98_ioctl(struct tty_struct *tty, struct file *file, |
| 341 | unsigned int cmd, unsigned long arg) |
| 342 | { |
| 343 | switch (cmd) { |
| 344 | case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */ |
| 345 | return pty_set_lock(tty, (int __user *)arg); |
| 346 | case TIOCGPTN: /* Get PT Number */ |
| 347 | return put_user(tty->index, (unsigned int __user *)arg); |
| 348 | } |
| 349 | |
| 350 | return -ENOIOCTLCMD; |
| 351 | } |
| 352 | |
| 353 | static void __init unix98_pty_init(void) |
| 354 | { |
| 355 | devfs_mk_dir("pts"); |
| 356 | ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX); |
| 357 | if (!ptm_driver) |
| 358 | panic("Couldn't allocate Unix98 ptm driver"); |
| 359 | pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX); |
| 360 | if (!pts_driver) |
| 361 | panic("Couldn't allocate Unix98 pts driver"); |
| 362 | |
| 363 | ptm_driver->owner = THIS_MODULE; |
| 364 | ptm_driver->driver_name = "pty_master"; |
| 365 | ptm_driver->name = "ptm"; |
| 366 | ptm_driver->major = UNIX98_PTY_MASTER_MAJOR; |
| 367 | ptm_driver->minor_start = 0; |
| 368 | ptm_driver->type = TTY_DRIVER_TYPE_PTY; |
| 369 | ptm_driver->subtype = PTY_TYPE_MASTER; |
| 370 | ptm_driver->init_termios = tty_std_termios; |
| 371 | ptm_driver->init_termios.c_iflag = 0; |
| 372 | ptm_driver->init_termios.c_oflag = 0; |
| 373 | ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD; |
| 374 | ptm_driver->init_termios.c_lflag = 0; |
| 375 | ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW | |
| 376 | TTY_DRIVER_NO_DEVFS | TTY_DRIVER_DEVPTS_MEM; |
| 377 | ptm_driver->other = pts_driver; |
| 378 | tty_set_operations(ptm_driver, &pty_ops); |
| 379 | ptm_driver->ioctl = pty_unix98_ioctl; |
| 380 | |
| 381 | pts_driver->owner = THIS_MODULE; |
| 382 | pts_driver->driver_name = "pty_slave"; |
| 383 | pts_driver->name = "pts"; |
| 384 | pts_driver->major = UNIX98_PTY_SLAVE_MAJOR; |
| 385 | pts_driver->minor_start = 0; |
| 386 | pts_driver->type = TTY_DRIVER_TYPE_PTY; |
| 387 | pts_driver->subtype = PTY_TYPE_SLAVE; |
| 388 | pts_driver->init_termios = tty_std_termios; |
| 389 | pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD; |
| 390 | pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW | |
| 391 | TTY_DRIVER_NO_DEVFS | TTY_DRIVER_DEVPTS_MEM; |
| 392 | pts_driver->other = ptm_driver; |
| 393 | tty_set_operations(pts_driver, &pty_ops); |
| 394 | |
| 395 | if (tty_register_driver(ptm_driver)) |
| 396 | panic("Couldn't register Unix98 ptm driver"); |
| 397 | if (tty_register_driver(pts_driver)) |
| 398 | panic("Couldn't register Unix98 pts driver"); |
| 399 | |
| 400 | pty_table[1].data = &ptm_driver->refcount; |
| 401 | } |
| 402 | #else |
| 403 | static inline void unix98_pty_init(void) { } |
| 404 | #endif |
| 405 | |
| 406 | static int __init pty_init(void) |
| 407 | { |
| 408 | legacy_pty_init(); |
| 409 | unix98_pty_init(); |
| 410 | return 0; |
| 411 | } |
| 412 | module_init(pty_init); |