drivers/char/pty.c

   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 <asm/bitops.h>
  33 #include <linux/devpts_fs.h>
  34
  35 #if defined(CONFIG_LEGACY_PTYS) || defined(CONFIG_UNIX98_PTYS)
  36
  37 #ifdef CONFIG_LEGACY_PTYS
  38 static struct tty_driver *pty_driver, *pty_slave_driver;
  39 #endif
  40
  41 /* These are global because they are accessed in tty_io.c */
  42 #ifdef CONFIG_UNIX98_PTYS
  43 struct tty_driver *ptm_driver;
  44 struct tty_driver *pts_driver;
  45 #endif
  46
  47 static void pty_close(struct tty_struct * tty, struct file * filp)
  48 {
  49         if (!tty)
  50                 return;
  51         if (tty->driver->subtype == PTY_TYPE_MASTER) {
  52                 if (tty->count > 1)
  53                         printk("master pty_close: count = %d!!\n", tty->count);
  54         } else {
  55                 if (tty->count > 2)
  56                         return;
  57         }
  58         wake_up_interruptible(&tty->read_wait);
  59         wake_up_interruptible(&tty->write_wait);
  60         tty->packet = 0;
  61         if (!tty->link)
  62                 return;
  63         tty->link->packet = 0;
  64         wake_up_interruptible(&tty->link->read_wait);
  65         wake_up_interruptible(&tty->link->write_wait);
  66         set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
  67         if (tty->driver->subtype == PTY_TYPE_MASTER) {
  68                 set_bit(TTY_OTHER_CLOSED, &tty->flags);
  69 #ifdef CONFIG_UNIX98_PTYS
  70                 if (tty->driver == ptm_driver)
  71                         devpts_pty_kill(tty->index);
  72 #endif
  73                 tty_vhangup(tty->link);
  74         }
  75 }
  76
  77 /*
  78  * The unthrottle routine is called by the line discipline to signal
  79  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
  80  * flag is always set, to force the line discipline to always call the
  81  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
  82  * characters in the queue.  This is necessary since each time this
  83  * happens, we need to wake up any sleeping processes that could be
  84  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
  85  * for the pty buffer to be drained.
  86  */
  87 static void pty_unthrottle(struct tty_struct * tty)
  88 {
  89         struct tty_struct *o_tty = tty->link;
  90
  91         if (!o_tty)
  92                 return;
  93
  94         if ((o_tty->flags & (1 << TTY_DO_WRITE_WAKEUP)) &&
  95             o_tty->ldisc.write_wakeup)
  96                 (o_tty->ldisc.write_wakeup)(o_tty);
  97         wake_up_interruptible(&o_tty->write_wait);
  98         set_bit(TTY_THROTTLED, &tty->flags);
  99 }
 100
 101 /*
 102  * WSH 05/24/97: modified to
 103  *   (1) use space in tty->flip instead of a shared temp buffer
 104  *       The flip buffers aren't being used for a pty, so there's lots
 105  *       of space available.  The buffer is protected by a per-pty
 106  *       semaphore that should almost never come under contention.
 107  *   (2) avoid redundant copying for cases where count >> receive_room
 108  * N.B. Calls from user space may now return an error code instead of
 109  * a count.
 110  */
 111 static int pty_write(struct tty_struct * tty, int from_user,
 112                        const unsigned char *buf, int count)
 113 {
 114         struct tty_struct *to = tty->link;
 115         int     c=0, n, room;
 116         char    *temp_buffer;
 117
 118         if (!to || tty->stopped)
 119                 return 0;
 120
 121         if (from_user) {
 122                 down(&tty->flip.pty_sem);
 123                 temp_buffer = &tty->flip.char_buf[0];
 124                 while (count > 0) {
 125                         /* check space so we don't copy needlessly */
 126                         n = to->ldisc.receive_room(to);
 127                         if (n > count)
 128                                 n = count;
 129                         if (!n) break;
 130
 131                         n  = min(n, PTY_BUF_SIZE);
 132                         n -= copy_from_user(temp_buffer, buf, n);
 133                         if (!n) {
 134                                 if (!c)
 135                                         c = -EFAULT;
 136                                 break;
 137                         }
 138
 139                         /* check again in case the buffer filled up */
 140                         room = to->ldisc.receive_room(to);
 141                         if (n > room)
 142                                 n = room;
 143                         if (!n) break;
 144                         buf   += n;
 145                         c     += n;
 146                         count -= n;
 147                         to->ldisc.receive_buf(to, temp_buffer, 0, n);
 148                 }
 149                 up(&tty->flip.pty_sem);
 150         } else {
 151                 c = to->ldisc.receive_room(to);
 152                 if (c > count)
 153                         c = count;
 154                 to->ldisc.receive_buf(to, buf, 0, c);
 155         }
 156
 157         return c;
 158 }
 159
 160 static int pty_write_room(struct tty_struct *tty)
 161 {
 162         struct tty_struct *to = tty->link;
 163
 164         if (!to || tty->stopped)
 165                 return 0;
 166
 167         return to->ldisc.receive_room(to);
 168 }
 169
 170 /*
 171  *      WSH 05/24/97:  Modified for asymmetric MASTER/SLAVE behavior
 172  *      The chars_in_buffer() value is used by the ldisc select() function
 173  *      to hold off writing when chars_in_buffer > WAKEUP_CHARS (== 256).
 174  *      The pty driver chars_in_buffer() Master/Slave must behave differently:
 175  *
 176  *      The Master side needs to allow typed-ahead commands to accumulate
 177  *      while being canonicalized, so we report "our buffer" as empty until
 178  *      some threshold is reached, and then report the count. (Any count >
 179  *      WAKEUP_CHARS is regarded by select() as "full".)  To avoid deadlock
 180  *      the count returned must be 0 if no canonical data is available to be
 181  *      read. (The N_TTY ldisc.chars_in_buffer now knows this.)
 182  *
 183  *      The Slave side passes all characters in raw mode to the Master side's
 184  *      buffer where they can be read immediately, so in this case we can
 185  *      return the true count in the buffer.
 186  */
 187 static int pty_chars_in_buffer(struct tty_struct *tty)
 188 {
 189         struct tty_struct *to = tty->link;
 190         int count;
 191
 192         if (!to || !to->ldisc.chars_in_buffer)
 193                 return 0;
 194
 195         /* The ldisc must report 0 if no characters available to be read */
 196         count = to->ldisc.chars_in_buffer(to);
 197
 198         if (tty->driver->subtype == PTY_TYPE_SLAVE) return count;
 199
 200         /* Master side driver ... if the other side's read buffer is less than
 201          * half full, return 0 to allow writers to proceed; otherwise return
 202          * the count.  This leaves a comfortable margin to avoid overflow,
 203          * and still allows half a buffer's worth of typed-ahead commands.
 204          */
 205         return ((count < N_TTY_BUF_SIZE/2) ? 0 : count);
 206 }
 207
 208 /*
 209  * Return the device number of a Unix98 PTY (only!).  This lets us open a
 210  * master pty with the multi-headed ptmx device, then find out which
 211  * one we got after it is open, with an ioctl.
 212  */
 213 #ifdef CONFIG_UNIX98_PTYS
 214 static int pty_get_device_number(struct tty_struct *tty, unsigned __user *value)
 215 {
 216         unsigned int result = tty->index;
 217         return put_user(result, value);
 218 }
 219 #endif
 220
 221 /* Set the lock flag on a pty */
 222 static int pty_set_lock(struct tty_struct *tty, int __user * arg)
 223 {
 224         int val;
 225         if (get_user(val,arg))
 226                 return -EFAULT;
 227         if (val)
 228                 set_bit(TTY_PTY_LOCK, &tty->flags);
 229         else
 230                 clear_bit(TTY_PTY_LOCK, &tty->flags);
 231         return 0;
 232 }
 233
 234 #ifdef CONFIG_LEGACY_PTYS
 235 static int pty_bsd_ioctl(struct tty_struct *tty, struct file *file,
 236                          unsigned int cmd, unsigned long arg)
 237 {
 238         if (!tty) {
 239                 printk("pty_ioctl called with NULL tty!\n");
 240                 return -EIO;
 241         }
 242         switch(cmd) {
 243         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 244                 return pty_set_lock(tty, (int __user *) arg);
 245         }
 246         return -ENOIOCTLCMD;
 247 }
 248 #endif
 249
 250 #ifdef CONFIG_UNIX98_PTYS
 251 static int pty_unix98_ioctl(struct tty_struct *tty, struct file *file,
 252                             unsigned int cmd, unsigned long arg)
 253 {
 254         if (!tty) {
 255                 printk("pty_unix98_ioctl called with NULL tty!\n");
 256                 return -EIO;
 257         }
 258         switch(cmd) {
 259         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 260                 return pty_set_lock(tty, (int __user *)arg);
 261         case TIOCGPTN: /* Get PT Number */
 262                 return pty_get_device_number(tty, (unsigned int __user *)arg);
 263         }
 264
 265         return -ENOIOCTLCMD;
 266 }
 267 #endif
 268
 269 static void pty_flush_buffer(struct tty_struct *tty)
 270 {
 271         struct tty_struct *to = tty->link;
 272
 273         if (!to)
 274                 return;
 275
 276         if (to->ldisc.flush_buffer)
 277                 to->ldisc.flush_buffer(to);
 278
 279         if (to->packet) {
 280                 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
 281                 wake_up_interruptible(&to->read_wait);
 282         }
 283 }
 284
 285 static int pty_open(struct tty_struct *tty, struct file * filp)
 286 {
 287         int     retval = -ENODEV;
 288
 289         if (!tty || !tty->link)
 290                 goto out;
 291
 292         retval = -EIO;
 293         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 294                 goto out;
 295         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
 296                 goto out;
 297         if (tty->link->count != 1)
 298                 goto out;
 299
 300         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 301         set_bit(TTY_THROTTLED, &tty->flags);
 302         set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 303         retval = 0;
 304 out:
 305         return retval;
 306 }
 307
 308 static void pty_set_termios(struct tty_struct *tty, struct termios *old_termios)
 309 {
 310         tty->termios->c_cflag &= ~(CSIZE | PARENB);
 311         tty->termios->c_cflag |= (CS8 | CREAD);
 312 }
 313
 314 static struct tty_operations pty_ops = {
 315         .open = pty_open,
 316         .close = pty_close,
 317         .write = pty_write,
 318         .write_room = pty_write_room,
 319         .flush_buffer = pty_flush_buffer,
 320         .chars_in_buffer = pty_chars_in_buffer,
 321         .unthrottle = pty_unthrottle,
 322         .set_termios = pty_set_termios,
 323 };
 324
 325 /* sysctl support for setting limits on the number of Unix98 ptys allocated.
 326    Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly. */
 327 #ifdef CONFIG_UNIX98_PTYS
 328 int pty_limit = NR_UNIX98_PTY_DEFAULT;
 329 static int pty_limit_min = 0;
 330 static int pty_limit_max = NR_UNIX98_PTY_MAX;
 331
 332 ctl_table pty_table[] = {
 333         {
 334                 .ctl_name       = PTY_MAX,
 335                 .procname       = "max",
 336                 .maxlen         = sizeof(int),
 337                 .mode           = 0644,
 338                 .data           = &pty_limit,
 339                 .proc_handler   = &proc_dointvec_minmax,
 340                 .strategy       = &sysctl_intvec,
 341                 .extra1         = &pty_limit_min,
 342                 .extra2         = &pty_limit_max,
 343         }, {
 344                 .ctl_name       = PTY_NR,
 345                 .procname       = "nr",
 346                 .maxlen         = sizeof(int),
 347                 .mode           = 0444,
 348                 .proc_handler   = &proc_dointvec,
 349         }, {
 350                 .ctl_name       = 0
 351         }
 352 };
 353 #endif
 354
 355 /* Initialization */
 356
 357 static int __init pty_init(void)
 358 {
 359 #ifdef CONFIG_LEGACY_PTYS
 360         /* Traditional BSD devices */
 361
 362         pty_driver = alloc_tty_driver(NR_PTYS);
 363         if (!pty_driver)
 364                 panic("Couldn't allocate pty driver");
 365
 366         pty_slave_driver = alloc_tty_driver(NR_PTYS);
 367         if (!pty_slave_driver)
 368                 panic("Couldn't allocate pty slave driver");
 369
 370         pty_driver->owner = THIS_MODULE;
 371         pty_driver->driver_name = "pty_master";
 372         pty_driver->name = "pty";
 373         pty_driver->devfs_name = "pty/m";
 374         pty_driver->major = PTY_MASTER_MAJOR;
 375         pty_driver->minor_start = 0;
 376         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 377         pty_driver->subtype = PTY_TYPE_MASTER;
 378         pty_driver->init_termios = tty_std_termios;
 379         pty_driver->init_termios.c_iflag = 0;
 380         pty_driver->init_termios.c_oflag = 0;
 381         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 382         pty_driver->init_termios.c_lflag = 0;
 383         pty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW;
 384         pty_driver->other = pty_slave_driver;
 385         tty_set_operations(pty_driver, &pty_ops);
 386         pty_driver->ioctl = pty_bsd_ioctl;
 387
 388         pty_slave_driver->owner = THIS_MODULE;
 389         pty_slave_driver->driver_name = "pty_slave";
 390         pty_slave_driver->name = "ttyp";
 391         pty_slave_driver->devfs_name = "pty/s";
 392         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 393         pty_slave_driver->minor_start = 0;
 394         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 395         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 396         pty_slave_driver->init_termios = tty_std_termios;
 397         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 398         pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS |
 399                                         TTY_DRIVER_REAL_RAW;
 400         pty_slave_driver->other = pty_driver;
 401         tty_set_operations(pty_slave_driver, &pty_ops);
 402
 403         if (tty_register_driver(pty_driver))
 404                 panic("Couldn't register pty driver");
 405         if (tty_register_driver(pty_slave_driver))
 406                 panic("Couldn't register pty slave driver");
 407
 408 #endif /* CONFIG_LEGACY_PTYS */
 409
 410 #ifdef CONFIG_UNIX98_PTYS
 411         /* Unix98 devices */
 412         devfs_mk_dir("pts");
 413         ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
 414         if (!ptm_driver)
 415                 panic("Couldn't allocate Unix98 ptm driver");
 416         pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
 417         if (!pts_driver)
 418                 panic("Couldn't allocate Unix98 pts driver");
 419
 420         ptm_driver->owner = THIS_MODULE;
 421         ptm_driver->driver_name = "pty_master";
 422         ptm_driver->name = "ptm";
 423         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 424         ptm_driver->minor_start = 0;
 425         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 426         ptm_driver->subtype = PTY_TYPE_MASTER;
 427         ptm_driver->init_termios = tty_std_termios;
 428         ptm_driver->init_termios.c_iflag = 0;
 429         ptm_driver->init_termios.c_oflag = 0;
 430         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 431         ptm_driver->init_termios.c_lflag = 0;
 432         ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
 433                 TTY_DRIVER_NO_DEVFS | TTY_DRIVER_DEVPTS_MEM;
 434         ptm_driver->other = pts_driver;
 435         tty_set_operations(ptm_driver, &pty_ops);
 436         ptm_driver->ioctl = pty_unix98_ioctl;
 437
 438         pts_driver->owner = THIS_MODULE;
 439         pts_driver->driver_name = "pty_slave";
 440         pts_driver->name = "pts";
 441         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 442         pts_driver->minor_start = 0;
 443         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 444         pts_driver->subtype = PTY_TYPE_SLAVE;
 445         pts_driver->init_termios = tty_std_termios;
 446         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 447         pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
 448                 TTY_DRIVER_NO_DEVFS | TTY_DRIVER_DEVPTS_MEM;
 449         pts_driver->other = ptm_driver;
 450         tty_set_operations(pts_driver, &pty_ops);
 451
 452         if (tty_register_driver(ptm_driver))
 453                 panic("Couldn't register Unix98 ptm driver");
 454         if (tty_register_driver(pts_driver))
 455                 panic("Couldn't register Unix98 pts driver");
 456
 457         pty_table[1].data = &ptm_driver->refcount;
 458 #endif /* CONFIG_UNIX98_PTYS */
 459
 460         return 0;
 461 }
 462 module_init(pty_init);
 463
 464 #endif /* CONFIG_LEGACY_PTYS || CONFIG_UNIX98_PTYS */