1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *  Copyright (C) 1991, 1992  Linus Torvalds
4  */
5 
6 /*
7  * 'tty_io.c' gives an orthogonal feeling to tty's, be they consoles
8  * or rs-channels. It also implements echoing, cooked mode etc.
9  *
10  * Kill-line thanks to John T Kohl, who also corrected VMIN = VTIME = 0.
11  *
12  * Modified by Theodore Ts'o, 9/14/92, to dynamically allocate the
13  * tty_struct and tty_queue structures.  Previously there was an array
14  * of 256 tty_struct's which was statically allocated, and the
15  * tty_queue structures were allocated at boot time.  Both are now
16  * dynamically allocated only when the tty is open.
17  *
18  * Also restructured routines so that there is more of a separation
19  * between the high-level tty routines (tty_io.c and tty_ioctl.c) and
20  * the low-level tty routines (serial.c, pty.c, console.c).  This
21  * makes for cleaner and more compact code.  -TYT, 9/17/92
22  *
23  * Modified by Fred N. van Kempen, 01/29/93, to add line disciplines
24  * which can be dynamically activated and de-activated by the line
25  * discipline handling modules (like SLIP).
26  *
27  * NOTE: pay no attention to the line discipline code (yet); its
28  * interface is still subject to change in this version...
29  * -- TYT, 1/31/92
30  *
31  * Added functionality to the OPOST tty handling.  No delays, but all
32  * other bits should be there.
33  *	-- Nick Holloway <alfie@dcs.warwick.ac.uk>, 27th May 1993.
34  *
35  * Rewrote canonical mode and added more termios flags.
36  *	-- julian@uhunix.uhcc.hawaii.edu (J. Cowley), 13Jan94
37  *
38  * Reorganized FASYNC support so mouse code can share it.
39  *	-- ctm@ardi.com, 9Sep95
40  *
41  * New TIOCLINUX variants added.
42  *	-- mj@k332.feld.cvut.cz, 19-Nov-95
43  *
44  * Restrict vt switching via ioctl()
45  *      -- grif@cs.ucr.edu, 5-Dec-95
46  *
47  * Move console and virtual terminal code to more appropriate files,
48  * implement CONFIG_VT and generalize console device interface.
49  *	-- Marko Kohtala <Marko.Kohtala@hut.fi>, March 97
50  *
51  * Rewrote tty_init_dev and tty_release_dev to eliminate races.
52  *	-- Bill Hawes <whawes@star.net>, June 97
53  *
54  * Added devfs support.
55  *      -- C. Scott Ananian <cananian@alumni.princeton.edu>, 13-Jan-1998
56  *
57  * Added support for a Unix98-style ptmx device.
58  *      -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998
59  *
60  * Reduced memory usage for older ARM systems
61  *      -- Russell King <rmk@arm.linux.org.uk>
62  *
63  * Move do_SAK() into process context.  Less stack use in devfs functions.
64  * alloc_tty_struct() always uses kmalloc()
65  *			 -- Andrew Morton <andrewm@uow.edu.eu> 17Mar01
66  */
67 
68 #include <linux/types.h>
69 #include <linux/major.h>
70 #include <linux/errno.h>
71 #include <linux/signal.h>
72 #include <linux/fcntl.h>
73 #include <linux/sched/signal.h>
74 #include <linux/sched/task.h>
75 #include <linux/interrupt.h>
76 #include <linux/tty.h>
77 #include <linux/tty_driver.h>
78 #include <linux/tty_flip.h>
79 #include <linux/devpts_fs.h>
80 #include <linux/file.h>
81 #include <linux/fdtable.h>
82 #include <linux/console.h>
83 #include <linux/timer.h>
84 #include <linux/ctype.h>
85 #include <linux/kd.h>
86 #include <linux/mm.h>
87 #include <linux/string.h>
88 #include <linux/slab.h>
89 #include <linux/poll.h>
90 #include <linux/ppp-ioctl.h>
91 #include <linux/proc_fs.h>
92 #include <linux/init.h>
93 #include <linux/module.h>
94 #include <linux/device.h>
95 #include <linux/wait.h>
96 #include <linux/bitops.h>
97 #include <linux/delay.h>
98 #include <linux/seq_file.h>
99 #include <linux/serial.h>
100 #include <linux/ratelimit.h>
101 #include <linux/compat.h>
102 
103 #include <linux/uaccess.h>
104 
105 #include <linux/kbd_kern.h>
106 #include <linux/vt_kern.h>
107 #include <linux/selection.h>
108 
109 #include <linux/kmod.h>
110 #include <linux/nsproxy.h>
111 #include "tty.h"
112 
113 #undef TTY_DEBUG_HANGUP
114 #ifdef TTY_DEBUG_HANGUP
115 # define tty_debug_hangup(tty, f, args...)	tty_debug(tty, f, ##args)
116 #else
117 # define tty_debug_hangup(tty, f, args...)	do { } while (0)
118 #endif
119 
120 #define TTY_PARANOIA_CHECK 1
121 #define CHECK_TTY_COUNT 1
122 
123 struct ktermios tty_std_termios = {	/* for the benefit of tty drivers  */
124 	.c_iflag = ICRNL | IXON,
125 	.c_oflag = OPOST | ONLCR,
126 	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
127 	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
128 		   ECHOCTL | ECHOKE | IEXTEN,
129 	.c_cc = INIT_C_CC,
130 	.c_ispeed = 38400,
131 	.c_ospeed = 38400,
132 	/* .c_line = N_TTY, */
133 };
134 EXPORT_SYMBOL(tty_std_termios);
135 
136 /* This list gets poked at by procfs and various bits of boot up code. This
137  * could do with some rationalisation such as pulling the tty proc function
138  * into this file.
139  */
140 
141 LIST_HEAD(tty_drivers);			/* linked list of tty drivers */
142 
143 /* Mutex to protect creating and releasing a tty */
144 DEFINE_MUTEX(tty_mutex);
145 
146 static ssize_t tty_read(struct kiocb *, struct iov_iter *);
147 static ssize_t tty_write(struct kiocb *, struct iov_iter *);
148 static __poll_t tty_poll(struct file *, poll_table *);
149 static int tty_open(struct inode *, struct file *);
150 #ifdef CONFIG_COMPAT
151 static long tty_compat_ioctl(struct file *file, unsigned int cmd,
152 				unsigned long arg);
153 #else
154 #define tty_compat_ioctl NULL
155 #endif
156 static int __tty_fasync(int fd, struct file *filp, int on);
157 static int tty_fasync(int fd, struct file *filp, int on);
158 static void release_tty(struct tty_struct *tty, int idx);
159 
160 /**
161  * free_tty_struct	-	free a disused tty
162  * @tty: tty struct to free
163  *
164  * Free the write buffers, tty queue and tty memory itself.
165  *
166  * Locking: none. Must be called after tty is definitely unused
167  */
free_tty_struct(struct tty_struct * tty)168 static void free_tty_struct(struct tty_struct *tty)
169 {
170 	tty_ldisc_deinit(tty);
171 	put_device(tty->dev);
172 	kvfree(tty->write_buf);
173 	tty->magic = 0xDEADDEAD;
174 	kfree(tty);
175 }
176 
file_tty(struct file * file)177 static inline struct tty_struct *file_tty(struct file *file)
178 {
179 	return ((struct tty_file_private *)file->private_data)->tty;
180 }
181 
tty_alloc_file(struct file * file)182 int tty_alloc_file(struct file *file)
183 {
184 	struct tty_file_private *priv;
185 
186 	priv = kmalloc(sizeof(*priv), GFP_KERNEL);
187 	if (!priv)
188 		return -ENOMEM;
189 
190 	file->private_data = priv;
191 
192 	return 0;
193 }
194 
195 /* Associate a new file with the tty structure */
tty_add_file(struct tty_struct * tty,struct file * file)196 void tty_add_file(struct tty_struct *tty, struct file *file)
197 {
198 	struct tty_file_private *priv = file->private_data;
199 
200 	priv->tty = tty;
201 	priv->file = file;
202 
203 	spin_lock(&tty->files_lock);
204 	list_add(&priv->list, &tty->tty_files);
205 	spin_unlock(&tty->files_lock);
206 }
207 
208 /**
209  * tty_free_file - free file->private_data
210  * @file: to free private_data of
211  *
212  * This shall be used only for fail path handling when tty_add_file was not
213  * called yet.
214  */
tty_free_file(struct file * file)215 void tty_free_file(struct file *file)
216 {
217 	struct tty_file_private *priv = file->private_data;
218 
219 	file->private_data = NULL;
220 	kfree(priv);
221 }
222 
223 /* Delete file from its tty */
tty_del_file(struct file * file)224 static void tty_del_file(struct file *file)
225 {
226 	struct tty_file_private *priv = file->private_data;
227 	struct tty_struct *tty = priv->tty;
228 
229 	spin_lock(&tty->files_lock);
230 	list_del(&priv->list);
231 	spin_unlock(&tty->files_lock);
232 	tty_free_file(file);
233 }
234 
235 /**
236  * tty_name	-	return tty naming
237  * @tty: tty structure
238  *
239  * Convert a tty structure into a name. The name reflects the kernel naming
240  * policy and if udev is in use may not reflect user space
241  *
242  * Locking: none
243  */
tty_name(const struct tty_struct * tty)244 const char *tty_name(const struct tty_struct *tty)
245 {
246 	if (!tty) /* Hmm.  NULL pointer.  That's fun. */
247 		return "NULL tty";
248 	return tty->name;
249 }
250 EXPORT_SYMBOL(tty_name);
251 
tty_driver_name(const struct tty_struct * tty)252 const char *tty_driver_name(const struct tty_struct *tty)
253 {
254 	if (!tty || !tty->driver)
255 		return "";
256 	return tty->driver->name;
257 }
258 
tty_paranoia_check(struct tty_struct * tty,struct inode * inode,const char * routine)259 static int tty_paranoia_check(struct tty_struct *tty, struct inode *inode,
260 			      const char *routine)
261 {
262 #ifdef TTY_PARANOIA_CHECK
263 	if (!tty) {
264 		pr_warn("(%d:%d): %s: NULL tty\n",
265 			imajor(inode), iminor(inode), routine);
266 		return 1;
267 	}
268 	if (tty->magic != TTY_MAGIC) {
269 		pr_warn("(%d:%d): %s: bad magic number\n",
270 			imajor(inode), iminor(inode), routine);
271 		return 1;
272 	}
273 #endif
274 	return 0;
275 }
276 
277 /* Caller must hold tty_lock */
check_tty_count(struct tty_struct * tty,const char * routine)278 static int check_tty_count(struct tty_struct *tty, const char *routine)
279 {
280 #ifdef CHECK_TTY_COUNT
281 	struct list_head *p;
282 	int count = 0, kopen_count = 0;
283 
284 	spin_lock(&tty->files_lock);
285 	list_for_each(p, &tty->tty_files) {
286 		count++;
287 	}
288 	spin_unlock(&tty->files_lock);
289 	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
290 	    tty->driver->subtype == PTY_TYPE_SLAVE &&
291 	    tty->link && tty->link->count)
292 		count++;
293 	if (tty_port_kopened(tty->port))
294 		kopen_count++;
295 	if (tty->count != (count + kopen_count)) {
296 		tty_warn(tty, "%s: tty->count(%d) != (#fd's(%d) + #kopen's(%d))\n",
297 			 routine, tty->count, count, kopen_count);
298 		return (count + kopen_count);
299 	}
300 #endif
301 	return 0;
302 }
303 
304 /**
305  * get_tty_driver		-	find device of a tty
306  * @device: device identifier
307  * @index: returns the index of the tty
308  *
309  * This routine returns a tty driver structure, given a device number and also
310  * passes back the index number.
311  *
312  * Locking: caller must hold tty_mutex
313  */
get_tty_driver(dev_t device,int * index)314 static struct tty_driver *get_tty_driver(dev_t device, int *index)
315 {
316 	struct tty_driver *p;
317 
318 	list_for_each_entry(p, &tty_drivers, tty_drivers) {
319 		dev_t base = MKDEV(p->major, p->minor_start);
320 
321 		if (device < base || device >= base + p->num)
322 			continue;
323 		*index = device - base;
324 		return tty_driver_kref_get(p);
325 	}
326 	return NULL;
327 }
328 
329 /**
330  * tty_dev_name_to_number	-	return dev_t for device name
331  * @name: user space name of device under /dev
332  * @number: pointer to dev_t that this function will populate
333  *
334  * This function converts device names like ttyS0 or ttyUSB1 into dev_t like
335  * (4, 64) or (188, 1). If no corresponding driver is registered then the
336  * function returns -%ENODEV.
337  *
338  * Locking: this acquires tty_mutex to protect the tty_drivers list from
339  *	being modified while we are traversing it, and makes sure to
340  *	release it before exiting.
341  */
tty_dev_name_to_number(const char * name,dev_t * number)342 int tty_dev_name_to_number(const char *name, dev_t *number)
343 {
344 	struct tty_driver *p;
345 	int ret;
346 	int index, prefix_length = 0;
347 	const char *str;
348 
349 	for (str = name; *str && !isdigit(*str); str++)
350 		;
351 
352 	if (!*str)
353 		return -EINVAL;
354 
355 	ret = kstrtoint(str, 10, &index);
356 	if (ret)
357 		return ret;
358 
359 	prefix_length = str - name;
360 	mutex_lock(&tty_mutex);
361 
362 	list_for_each_entry(p, &tty_drivers, tty_drivers)
363 		if (prefix_length == strlen(p->name) && strncmp(name,
364 					p->name, prefix_length) == 0) {
365 			if (index < p->num) {
366 				*number = MKDEV(p->major, p->minor_start + index);
367 				goto out;
368 			}
369 		}
370 
371 	/* if here then driver wasn't found */
372 	ret = -ENODEV;
373 out:
374 	mutex_unlock(&tty_mutex);
375 	return ret;
376 }
377 EXPORT_SYMBOL_GPL(tty_dev_name_to_number);
378 
379 #ifdef CONFIG_CONSOLE_POLL
380 
381 /**
382  * tty_find_polling_driver	-	find device of a polled tty
383  * @name: name string to match
384  * @line: pointer to resulting tty line nr
385  *
386  * This routine returns a tty driver structure, given a name and the condition
387  * that the tty driver is capable of polled operation.
388  */
tty_find_polling_driver(char * name,int * line)389 struct tty_driver *tty_find_polling_driver(char *name, int *line)
390 {
391 	struct tty_driver *p, *res = NULL;
392 	int tty_line = 0;
393 	int len;
394 	char *str, *stp;
395 
396 	for (str = name; *str; str++)
397 		if ((*str >= '0' && *str <= '9') || *str == ',')
398 			break;
399 	if (!*str)
400 		return NULL;
401 
402 	len = str - name;
403 	tty_line = simple_strtoul(str, &str, 10);
404 
405 	mutex_lock(&tty_mutex);
406 	/* Search through the tty devices to look for a match */
407 	list_for_each_entry(p, &tty_drivers, tty_drivers) {
408 		if (!len || strncmp(name, p->name, len) != 0)
409 			continue;
410 		stp = str;
411 		if (*stp == ',')
412 			stp++;
413 		if (*stp == '\0')
414 			stp = NULL;
415 
416 		if (tty_line >= 0 && tty_line < p->num && p->ops &&
417 		    p->ops->poll_init && !p->ops->poll_init(p, tty_line, stp)) {
418 			res = tty_driver_kref_get(p);
419 			*line = tty_line;
420 			break;
421 		}
422 	}
423 	mutex_unlock(&tty_mutex);
424 
425 	return res;
426 }
427 EXPORT_SYMBOL_GPL(tty_find_polling_driver);
428 #endif
429 
hung_up_tty_read(struct kiocb * iocb,struct iov_iter * to)430 static ssize_t hung_up_tty_read(struct kiocb *iocb, struct iov_iter *to)
431 {
432 	return 0;
433 }
434 
hung_up_tty_write(struct kiocb * iocb,struct iov_iter * from)435 static ssize_t hung_up_tty_write(struct kiocb *iocb, struct iov_iter *from)
436 {
437 	return -EIO;
438 }
439 
440 /* No kernel lock held - none needed ;) */
hung_up_tty_poll(struct file * filp,poll_table * wait)441 static __poll_t hung_up_tty_poll(struct file *filp, poll_table *wait)
442 {
443 	return EPOLLIN | EPOLLOUT | EPOLLERR | EPOLLHUP | EPOLLRDNORM | EPOLLWRNORM;
444 }
445 
hung_up_tty_ioctl(struct file * file,unsigned int cmd,unsigned long arg)446 static long hung_up_tty_ioctl(struct file *file, unsigned int cmd,
447 		unsigned long arg)
448 {
449 	return cmd == TIOCSPGRP ? -ENOTTY : -EIO;
450 }
451 
hung_up_tty_compat_ioctl(struct file * file,unsigned int cmd,unsigned long arg)452 static long hung_up_tty_compat_ioctl(struct file *file,
453 				     unsigned int cmd, unsigned long arg)
454 {
455 	return cmd == TIOCSPGRP ? -ENOTTY : -EIO;
456 }
457 
hung_up_tty_fasync(int fd,struct file * file,int on)458 static int hung_up_tty_fasync(int fd, struct file *file, int on)
459 {
460 	return -ENOTTY;
461 }
462 
tty_show_fdinfo(struct seq_file * m,struct file * file)463 static void tty_show_fdinfo(struct seq_file *m, struct file *file)
464 {
465 	struct tty_struct *tty = file_tty(file);
466 
467 	if (tty && tty->ops && tty->ops->show_fdinfo)
468 		tty->ops->show_fdinfo(tty, m);
469 }
470 
471 static const struct file_operations tty_fops = {
472 	.llseek		= no_llseek,
473 	.read_iter	= tty_read,
474 	.write_iter	= tty_write,
475 	.splice_read	= generic_file_splice_read,
476 	.splice_write	= iter_file_splice_write,
477 	.poll		= tty_poll,
478 	.unlocked_ioctl	= tty_ioctl,
479 	.compat_ioctl	= tty_compat_ioctl,
480 	.open		= tty_open,
481 	.release	= tty_release,
482 	.fasync		= tty_fasync,
483 	.show_fdinfo	= tty_show_fdinfo,
484 };
485 
486 static const struct file_operations console_fops = {
487 	.llseek		= no_llseek,
488 	.read_iter	= tty_read,
489 	.write_iter	= redirected_tty_write,
490 	.splice_read	= generic_file_splice_read,
491 	.splice_write	= iter_file_splice_write,
492 	.poll		= tty_poll,
493 	.unlocked_ioctl	= tty_ioctl,
494 	.compat_ioctl	= tty_compat_ioctl,
495 	.open		= tty_open,
496 	.release	= tty_release,
497 	.fasync		= tty_fasync,
498 };
499 
500 static const struct file_operations hung_up_tty_fops = {
501 	.llseek		= no_llseek,
502 	.read_iter	= hung_up_tty_read,
503 	.write_iter	= hung_up_tty_write,
504 	.poll		= hung_up_tty_poll,
505 	.unlocked_ioctl	= hung_up_tty_ioctl,
506 	.compat_ioctl	= hung_up_tty_compat_ioctl,
507 	.release	= tty_release,
508 	.fasync		= hung_up_tty_fasync,
509 };
510 
511 static DEFINE_SPINLOCK(redirect_lock);
512 static struct file *redirect;
513 
514 /**
515  * tty_wakeup	-	request more data
516  * @tty: terminal
517  *
518  * Internal and external helper for wakeups of tty. This function informs the
519  * line discipline if present that the driver is ready to receive more output
520  * data.
521  */
tty_wakeup(struct tty_struct * tty)522 void tty_wakeup(struct tty_struct *tty)
523 {
524 	struct tty_ldisc *ld;
525 
526 	if (test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) {
527 		ld = tty_ldisc_ref(tty);
528 		if (ld) {
529 			if (ld->ops->write_wakeup)
530 				ld->ops->write_wakeup(tty);
531 			tty_ldisc_deref(ld);
532 		}
533 	}
534 	wake_up_interruptible_poll(&tty->write_wait, EPOLLOUT);
535 }
536 EXPORT_SYMBOL_GPL(tty_wakeup);
537 
538 /**
539  * tty_release_redirect	-	Release a redirect on a pty if present
540  * @tty: tty device
541  *
542  * This is available to the pty code so if the master closes, if the slave is a
543  * redirect it can release the redirect.
544  */
tty_release_redirect(struct tty_struct * tty)545 static struct file *tty_release_redirect(struct tty_struct *tty)
546 {
547 	struct file *f = NULL;
548 
549 	spin_lock(&redirect_lock);
550 	if (redirect && file_tty(redirect) == tty) {
551 		f = redirect;
552 		redirect = NULL;
553 	}
554 	spin_unlock(&redirect_lock);
555 
556 	return f;
557 }
558 
559 /**
560  * __tty_hangup		-	actual handler for hangup events
561  * @tty: tty device
562  * @exit_session: if non-zero, signal all foreground group processes
563  *
564  * This can be called by a "kworker" kernel thread. That is process synchronous
565  * but doesn't hold any locks, so we need to make sure we have the appropriate
566  * locks for what we're doing.
567  *
568  * The hangup event clears any pending redirections onto the hung up device. It
569  * ensures future writes will error and it does the needed line discipline
570  * hangup and signal delivery. The tty object itself remains intact.
571  *
572  * Locking:
573  *  * BTM
574  *
575  *   * redirect lock for undoing redirection
576  *   * file list lock for manipulating list of ttys
577  *   * tty_ldiscs_lock from called functions
578  *   * termios_rwsem resetting termios data
579  *   * tasklist_lock to walk task list for hangup event
580  *
581  *    * ->siglock to protect ->signal/->sighand
582  *
583  */
__tty_hangup(struct tty_struct * tty,int exit_session)584 static void __tty_hangup(struct tty_struct *tty, int exit_session)
585 {
586 	struct file *cons_filp = NULL;
587 	struct file *filp, *f;
588 	struct tty_file_private *priv;
589 	int    closecount = 0, n;
590 	int refs;
591 
592 	if (!tty)
593 		return;
594 
595 	f = tty_release_redirect(tty);
596 
597 	tty_lock(tty);
598 
599 	if (test_bit(TTY_HUPPED, &tty->flags)) {
600 		tty_unlock(tty);
601 		return;
602 	}
603 
604 	/*
605 	 * Some console devices aren't actually hung up for technical and
606 	 * historical reasons, which can lead to indefinite interruptible
607 	 * sleep in n_tty_read().  The following explicitly tells
608 	 * n_tty_read() to abort readers.
609 	 */
610 	set_bit(TTY_HUPPING, &tty->flags);
611 
612 	/* inuse_filps is protected by the single tty lock,
613 	 * this really needs to change if we want to flush the
614 	 * workqueue with the lock held.
615 	 */
616 	check_tty_count(tty, "tty_hangup");
617 
618 	spin_lock(&tty->files_lock);
619 	/* This breaks for file handles being sent over AF_UNIX sockets ? */
620 	list_for_each_entry(priv, &tty->tty_files, list) {
621 		filp = priv->file;
622 		if (filp->f_op->write_iter == redirected_tty_write)
623 			cons_filp = filp;
624 		if (filp->f_op->write_iter != tty_write)
625 			continue;
626 		closecount++;
627 		__tty_fasync(-1, filp, 0);	/* can't block */
628 		filp->f_op = &hung_up_tty_fops;
629 	}
630 	spin_unlock(&tty->files_lock);
631 
632 	refs = tty_signal_session_leader(tty, exit_session);
633 	/* Account for the p->signal references we killed */
634 	while (refs--)
635 		tty_kref_put(tty);
636 
637 	tty_ldisc_hangup(tty, cons_filp != NULL);
638 
639 	spin_lock_irq(&tty->ctrl.lock);
640 	clear_bit(TTY_THROTTLED, &tty->flags);
641 	clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
642 	put_pid(tty->ctrl.session);
643 	put_pid(tty->ctrl.pgrp);
644 	tty->ctrl.session = NULL;
645 	tty->ctrl.pgrp = NULL;
646 	tty->ctrl.pktstatus = 0;
647 	spin_unlock_irq(&tty->ctrl.lock);
648 
649 	/*
650 	 * If one of the devices matches a console pointer, we
651 	 * cannot just call hangup() because that will cause
652 	 * tty->count and state->count to go out of sync.
653 	 * So we just call close() the right number of times.
654 	 */
655 	if (cons_filp) {
656 		if (tty->ops->close)
657 			for (n = 0; n < closecount; n++)
658 				tty->ops->close(tty, cons_filp);
659 	} else if (tty->ops->hangup)
660 		tty->ops->hangup(tty);
661 	/*
662 	 * We don't want to have driver/ldisc interactions beyond the ones
663 	 * we did here. The driver layer expects no calls after ->hangup()
664 	 * from the ldisc side, which is now guaranteed.
665 	 */
666 	set_bit(TTY_HUPPED, &tty->flags);
667 	clear_bit(TTY_HUPPING, &tty->flags);
668 	tty_unlock(tty);
669 
670 	if (f)
671 		fput(f);
672 }
673 
do_tty_hangup(struct work_struct * work)674 static void do_tty_hangup(struct work_struct *work)
675 {
676 	struct tty_struct *tty =
677 		container_of(work, struct tty_struct, hangup_work);
678 
679 	__tty_hangup(tty, 0);
680 }
681 
682 /**
683  * tty_hangup		-	trigger a hangup event
684  * @tty: tty to hangup
685  *
686  * A carrier loss (virtual or otherwise) has occurred on @tty. Schedule a
687  * hangup sequence to run after this event.
688  */
tty_hangup(struct tty_struct * tty)689 void tty_hangup(struct tty_struct *tty)
690 {
691 	tty_debug_hangup(tty, "hangup\n");
692 	schedule_work(&tty->hangup_work);
693 }
694 EXPORT_SYMBOL(tty_hangup);
695 
696 /**
697  * tty_vhangup		-	process vhangup
698  * @tty: tty to hangup
699  *
700  * The user has asked via system call for the terminal to be hung up. We do
701  * this synchronously so that when the syscall returns the process is complete.
702  * That guarantee is necessary for security reasons.
703  */
tty_vhangup(struct tty_struct * tty)704 void tty_vhangup(struct tty_struct *tty)
705 {
706 	tty_debug_hangup(tty, "vhangup\n");
707 	__tty_hangup(tty, 0);
708 }
709 EXPORT_SYMBOL(tty_vhangup);
710 
711 
712 /**
713  * tty_vhangup_self	-	process vhangup for own ctty
714  *
715  * Perform a vhangup on the current controlling tty
716  */
tty_vhangup_self(void)717 void tty_vhangup_self(void)
718 {
719 	struct tty_struct *tty;
720 
721 	tty = get_current_tty();
722 	if (tty) {
723 		tty_vhangup(tty);
724 		tty_kref_put(tty);
725 	}
726 }
727 
728 /**
729  * tty_vhangup_session	-	hangup session leader exit
730  * @tty: tty to hangup
731  *
732  * The session leader is exiting and hanging up its controlling terminal.
733  * Every process in the foreground process group is signalled %SIGHUP.
734  *
735  * We do this synchronously so that when the syscall returns the process is
736  * complete. That guarantee is necessary for security reasons.
737  */
tty_vhangup_session(struct tty_struct * tty)738 void tty_vhangup_session(struct tty_struct *tty)
739 {
740 	tty_debug_hangup(tty, "session hangup\n");
741 	__tty_hangup(tty, 1);
742 }
743 
744 /**
745  * tty_hung_up_p	-	was tty hung up
746  * @filp: file pointer of tty
747  *
748  * Return: true if the tty has been subject to a vhangup or a carrier loss
749  */
tty_hung_up_p(struct file * filp)750 int tty_hung_up_p(struct file *filp)
751 {
752 	return (filp && filp->f_op == &hung_up_tty_fops);
753 }
754 EXPORT_SYMBOL(tty_hung_up_p);
755 
__stop_tty(struct tty_struct * tty)756 void __stop_tty(struct tty_struct *tty)
757 {
758 	if (tty->flow.stopped)
759 		return;
760 	tty->flow.stopped = true;
761 	if (tty->ops->stop)
762 		tty->ops->stop(tty);
763 }
764 
765 /**
766  * stop_tty	-	propagate flow control
767  * @tty: tty to stop
768  *
769  * Perform flow control to the driver. May be called on an already stopped
770  * device and will not re-call the &tty_driver->stop() method.
771  *
772  * This functionality is used by both the line disciplines for halting incoming
773  * flow and by the driver. It may therefore be called from any context, may be
774  * under the tty %atomic_write_lock but not always.
775  *
776  * Locking:
777  *	flow.lock
778  */
stop_tty(struct tty_struct * tty)779 void stop_tty(struct tty_struct *tty)
780 {
781 	unsigned long flags;
782 
783 	spin_lock_irqsave(&tty->flow.lock, flags);
784 	__stop_tty(tty);
785 	spin_unlock_irqrestore(&tty->flow.lock, flags);
786 }
787 EXPORT_SYMBOL(stop_tty);
788 
__start_tty(struct tty_struct * tty)789 void __start_tty(struct tty_struct *tty)
790 {
791 	if (!tty->flow.stopped || tty->flow.tco_stopped)
792 		return;
793 	tty->flow.stopped = false;
794 	if (tty->ops->start)
795 		tty->ops->start(tty);
796 	tty_wakeup(tty);
797 }
798 
799 /**
800  * start_tty	-	propagate flow control
801  * @tty: tty to start
802  *
803  * Start a tty that has been stopped if at all possible. If @tty was previously
804  * stopped and is now being started, the &tty_driver->start() method is invoked
805  * and the line discipline woken.
806  *
807  * Locking:
808  *	flow.lock
809  */
start_tty(struct tty_struct * tty)810 void start_tty(struct tty_struct *tty)
811 {
812 	unsigned long flags;
813 
814 	spin_lock_irqsave(&tty->flow.lock, flags);
815 	__start_tty(tty);
816 	spin_unlock_irqrestore(&tty->flow.lock, flags);
817 }
818 EXPORT_SYMBOL(start_tty);
819 
tty_update_time(struct timespec64 * time)820 static void tty_update_time(struct timespec64 *time)
821 {
822 	time64_t sec = ktime_get_real_seconds();
823 
824 	/*
825 	 * We only care if the two values differ in anything other than the
826 	 * lower three bits (i.e every 8 seconds).  If so, then we can update
827 	 * the time of the tty device, otherwise it could be construded as a
828 	 * security leak to let userspace know the exact timing of the tty.
829 	 */
830 	if ((sec ^ time->tv_sec) & ~7)
831 		time->tv_sec = sec;
832 }
833 
834 /*
835  * Iterate on the ldisc ->read() function until we've gotten all
836  * the data the ldisc has for us.
837  *
838  * The "cookie" is something that the ldisc read function can fill
839  * in to let us know that there is more data to be had.
840  *
841  * We promise to continue to call the ldisc until it stops returning
842  * data or clears the cookie. The cookie may be something that the
843  * ldisc maintains state for and needs to free.
844  */
iterate_tty_read(struct tty_ldisc * ld,struct tty_struct * tty,struct file * file,struct iov_iter * to)845 static int iterate_tty_read(struct tty_ldisc *ld, struct tty_struct *tty,
846 		struct file *file, struct iov_iter *to)
847 {
848 	int retval = 0;
849 	void *cookie = NULL;
850 	unsigned long offset = 0;
851 	char kernel_buf[64];
852 	size_t count = iov_iter_count(to);
853 
854 	do {
855 		int size, copied;
856 
857 		size = count > sizeof(kernel_buf) ? sizeof(kernel_buf) : count;
858 		size = ld->ops->read(tty, file, kernel_buf, size, &cookie, offset);
859 		if (!size)
860 			break;
861 
862 		if (size < 0) {
863 			/* Did we have an earlier error (ie -EFAULT)? */
864 			if (retval)
865 				break;
866 			retval = size;
867 
868 			/*
869 			 * -EOVERFLOW means we didn't have enough space
870 			 * for a whole packet, and we shouldn't return
871 			 * a partial result.
872 			 */
873 			if (retval == -EOVERFLOW)
874 				offset = 0;
875 			break;
876 		}
877 
878 		copied = copy_to_iter(kernel_buf, size, to);
879 		offset += copied;
880 		count -= copied;
881 
882 		/*
883 		 * If the user copy failed, we still need to do another ->read()
884 		 * call if we had a cookie to let the ldisc clear up.
885 		 *
886 		 * But make sure size is zeroed.
887 		 */
888 		if (unlikely(copied != size)) {
889 			count = 0;
890 			retval = -EFAULT;
891 		}
892 	} while (cookie);
893 
894 	/* We always clear tty buffer in case they contained passwords */
895 	memzero_explicit(kernel_buf, sizeof(kernel_buf));
896 	return offset ? offset : retval;
897 }
898 
899 
900 /**
901  * tty_read	-	read method for tty device files
902  * @iocb: kernel I/O control block
903  * @to: destination for the data read
904  *
905  * Perform the read system call function on this terminal device. Checks
906  * for hung up devices before calling the line discipline method.
907  *
908  * Locking:
909  *	Locks the line discipline internally while needed. Multiple read calls
910  *	may be outstanding in parallel.
911  */
tty_read(struct kiocb * iocb,struct iov_iter * to)912 static ssize_t tty_read(struct kiocb *iocb, struct iov_iter *to)
913 {
914 	int i;
915 	struct file *file = iocb->ki_filp;
916 	struct inode *inode = file_inode(file);
917 	struct tty_struct *tty = file_tty(file);
918 	struct tty_ldisc *ld;
919 
920 	if (tty_paranoia_check(tty, inode, "tty_read"))
921 		return -EIO;
922 	if (!tty || tty_io_error(tty))
923 		return -EIO;
924 
925 	/* We want to wait for the line discipline to sort out in this
926 	 * situation.
927 	 */
928 	ld = tty_ldisc_ref_wait(tty);
929 	if (!ld)
930 		return hung_up_tty_read(iocb, to);
931 	i = -EIO;
932 	if (ld->ops->read)
933 		i = iterate_tty_read(ld, tty, file, to);
934 	tty_ldisc_deref(ld);
935 
936 	if (i > 0)
937 		tty_update_time(&inode->i_atime);
938 
939 	return i;
940 }
941 
tty_write_unlock(struct tty_struct * tty)942 static void tty_write_unlock(struct tty_struct *tty)
943 {
944 	mutex_unlock(&tty->atomic_write_lock);
945 	wake_up_interruptible_poll(&tty->write_wait, EPOLLOUT);
946 }
947 
tty_write_lock(struct tty_struct * tty,int ndelay)948 static int tty_write_lock(struct tty_struct *tty, int ndelay)
949 {
950 	if (!mutex_trylock(&tty->atomic_write_lock)) {
951 		if (ndelay)
952 			return -EAGAIN;
953 		if (mutex_lock_interruptible(&tty->atomic_write_lock))
954 			return -ERESTARTSYS;
955 	}
956 	return 0;
957 }
958 
959 /*
960  * Split writes up in sane blocksizes to avoid
961  * denial-of-service type attacks
962  */
do_tty_write(ssize_t (* write)(struct tty_struct *,struct file *,const unsigned char *,size_t),struct tty_struct * tty,struct file * file,struct iov_iter * from)963 static inline ssize_t do_tty_write(
964 	ssize_t (*write)(struct tty_struct *, struct file *, const unsigned char *, size_t),
965 	struct tty_struct *tty,
966 	struct file *file,
967 	struct iov_iter *from)
968 {
969 	size_t count = iov_iter_count(from);
970 	ssize_t ret, written = 0;
971 	unsigned int chunk;
972 
973 	ret = tty_write_lock(tty, file->f_flags & O_NDELAY);
974 	if (ret < 0)
975 		return ret;
976 
977 	/*
978 	 * We chunk up writes into a temporary buffer. This
979 	 * simplifies low-level drivers immensely, since they
980 	 * don't have locking issues and user mode accesses.
981 	 *
982 	 * But if TTY_NO_WRITE_SPLIT is set, we should use a
983 	 * big chunk-size..
984 	 *
985 	 * The default chunk-size is 2kB, because the NTTY
986 	 * layer has problems with bigger chunks. It will
987 	 * claim to be able to handle more characters than
988 	 * it actually does.
989 	 */
990 	chunk = 2048;
991 	if (test_bit(TTY_NO_WRITE_SPLIT, &tty->flags))
992 		chunk = 65536;
993 	if (count < chunk)
994 		chunk = count;
995 
996 	/* write_buf/write_cnt is protected by the atomic_write_lock mutex */
997 	if (tty->write_cnt < chunk) {
998 		unsigned char *buf_chunk;
999 
1000 		if (chunk < 1024)
1001 			chunk = 1024;
1002 
1003 		buf_chunk = kvmalloc(chunk, GFP_KERNEL | __GFP_RETRY_MAYFAIL);
1004 		if (!buf_chunk) {
1005 			ret = -ENOMEM;
1006 			goto out;
1007 		}
1008 		kvfree(tty->write_buf);
1009 		tty->write_cnt = chunk;
1010 		tty->write_buf = buf_chunk;
1011 	}
1012 
1013 	/* Do the write .. */
1014 	for (;;) {
1015 		size_t size = count;
1016 
1017 		if (size > chunk)
1018 			size = chunk;
1019 
1020 		ret = -EFAULT;
1021 		if (copy_from_iter(tty->write_buf, size, from) != size)
1022 			break;
1023 
1024 		ret = write(tty, file, tty->write_buf, size);
1025 		if (ret <= 0)
1026 			break;
1027 
1028 		written += ret;
1029 		if (ret > size)
1030 			break;
1031 
1032 		/* FIXME! Have Al check this! */
1033 		if (ret != size)
1034 			iov_iter_revert(from, size-ret);
1035 
1036 		count -= ret;
1037 		if (!count)
1038 			break;
1039 		ret = -ERESTARTSYS;
1040 		if (signal_pending(current))
1041 			break;
1042 		cond_resched();
1043 	}
1044 	if (written) {
1045 		tty_update_time(&file_inode(file)->i_mtime);
1046 		ret = written;
1047 	}
1048 out:
1049 	tty_write_unlock(tty);
1050 	return ret;
1051 }
1052 
1053 /**
1054  * tty_write_message - write a message to a certain tty, not just the console.
1055  * @tty: the destination tty_struct
1056  * @msg: the message to write
1057  *
1058  * This is used for messages that need to be redirected to a specific tty. We
1059  * don't put it into the syslog queue right now maybe in the future if really
1060  * needed.
1061  *
1062  * We must still hold the BTM and test the CLOSING flag for the moment.
1063  */
tty_write_message(struct tty_struct * tty,char * msg)1064 void tty_write_message(struct tty_struct *tty, char *msg)
1065 {
1066 	if (tty) {
1067 		mutex_lock(&tty->atomic_write_lock);
1068 		tty_lock(tty);
1069 		if (tty->ops->write && tty->count > 0)
1070 			tty->ops->write(tty, msg, strlen(msg));
1071 		tty_unlock(tty);
1072 		tty_write_unlock(tty);
1073 	}
1074 }
1075 
file_tty_write(struct file * file,struct kiocb * iocb,struct iov_iter * from)1076 static ssize_t file_tty_write(struct file *file, struct kiocb *iocb, struct iov_iter *from)
1077 {
1078 	struct tty_struct *tty = file_tty(file);
1079 	struct tty_ldisc *ld;
1080 	ssize_t ret;
1081 
1082 	if (tty_paranoia_check(tty, file_inode(file), "tty_write"))
1083 		return -EIO;
1084 	if (!tty || !tty->ops->write ||	tty_io_error(tty))
1085 		return -EIO;
1086 	/* Short term debug to catch buggy drivers */
1087 	if (tty->ops->write_room == NULL)
1088 		tty_err(tty, "missing write_room method\n");
1089 	ld = tty_ldisc_ref_wait(tty);
1090 	if (!ld)
1091 		return hung_up_tty_write(iocb, from);
1092 	if (!ld->ops->write)
1093 		ret = -EIO;
1094 	else
1095 		ret = do_tty_write(ld->ops->write, tty, file, from);
1096 	tty_ldisc_deref(ld);
1097 	return ret;
1098 }
1099 
1100 /**
1101  * tty_write		-	write method for tty device file
1102  * @iocb: kernel I/O control block
1103  * @from: iov_iter with data to write
1104  *
1105  * Write data to a tty device via the line discipline.
1106  *
1107  * Locking:
1108  *	Locks the line discipline as required
1109  *	Writes to the tty driver are serialized by the atomic_write_lock
1110  *	and are then processed in chunks to the device. The line
1111  *	discipline write method will not be invoked in parallel for
1112  *	each device.
1113  */
tty_write(struct kiocb * iocb,struct iov_iter * from)1114 static ssize_t tty_write(struct kiocb *iocb, struct iov_iter *from)
1115 {
1116 	return file_tty_write(iocb->ki_filp, iocb, from);
1117 }
1118 
redirected_tty_write(struct kiocb * iocb,struct iov_iter * iter)1119 ssize_t redirected_tty_write(struct kiocb *iocb, struct iov_iter *iter)
1120 {
1121 	struct file *p = NULL;
1122 
1123 	spin_lock(&redirect_lock);
1124 	if (redirect)
1125 		p = get_file(redirect);
1126 	spin_unlock(&redirect_lock);
1127 
1128 	/*
1129 	 * We know the redirected tty is just another tty, we can
1130 	 * call file_tty_write() directly with that file pointer.
1131 	 */
1132 	if (p) {
1133 		ssize_t res;
1134 
1135 		res = file_tty_write(p, iocb, iter);
1136 		fput(p);
1137 		return res;
1138 	}
1139 	return tty_write(iocb, iter);
1140 }
1141 
1142 /**
1143  * tty_send_xchar	-	send priority character
1144  * @tty: the tty to send to
1145  * @ch: xchar to send
1146  *
1147  * Send a high priority character to the tty even if stopped.
1148  *
1149  * Locking: none for xchar method, write ordering for write method.
1150  */
tty_send_xchar(struct tty_struct * tty,char ch)1151 int tty_send_xchar(struct tty_struct *tty, char ch)
1152 {
1153 	bool was_stopped = tty->flow.stopped;
1154 
1155 	if (tty->ops->send_xchar) {
1156 		down_read(&tty->termios_rwsem);
1157 		tty->ops->send_xchar(tty, ch);
1158 		up_read(&tty->termios_rwsem);
1159 		return 0;
1160 	}
1161 
1162 	if (tty_write_lock(tty, 0) < 0)
1163 		return -ERESTARTSYS;
1164 
1165 	down_read(&tty->termios_rwsem);
1166 	if (was_stopped)
1167 		start_tty(tty);
1168 	tty->ops->write(tty, &ch, 1);
1169 	if (was_stopped)
1170 		stop_tty(tty);
1171 	up_read(&tty->termios_rwsem);
1172 	tty_write_unlock(tty);
1173 	return 0;
1174 }
1175 
1176 /**
1177  * pty_line_name	-	generate name for a pty
1178  * @driver: the tty driver in use
1179  * @index: the minor number
1180  * @p: output buffer of at least 6 bytes
1181  *
1182  * Generate a name from a @driver reference and write it to the output buffer
1183  * @p.
1184  *
1185  * Locking: None
1186  */
pty_line_name(struct tty_driver * driver,int index,char * p)1187 static void pty_line_name(struct tty_driver *driver, int index, char *p)
1188 {
1189 	static const char ptychar[] = "pqrstuvwxyzabcde";
1190 	int i = index + driver->name_base;
1191 	/* ->name is initialized to "ttyp", but "tty" is expected */
1192 	sprintf(p, "%s%c%x",
1193 		driver->subtype == PTY_TYPE_SLAVE ? "tty" : driver->name,
1194 		ptychar[i >> 4 & 0xf], i & 0xf);
1195 }
1196 
1197 /**
1198  * tty_line_name	-	generate name for a tty
1199  * @driver: the tty driver in use
1200  * @index: the minor number
1201  * @p: output buffer of at least 7 bytes
1202  *
1203  * Generate a name from a @driver reference and write it to the output buffer
1204  * @p.
1205  *
1206  * Locking: None
1207  */
tty_line_name(struct tty_driver * driver,int index,char * p)1208 static ssize_t tty_line_name(struct tty_driver *driver, int index, char *p)
1209 {
1210 	if (driver->flags & TTY_DRIVER_UNNUMBERED_NODE)
1211 		return sprintf(p, "%s", driver->name);
1212 	else
1213 		return sprintf(p, "%s%d", driver->name,
1214 			       index + driver->name_base);
1215 }
1216 
1217 /**
1218  * tty_driver_lookup_tty() - find an existing tty, if any
1219  * @driver: the driver for the tty
1220  * @file: file object
1221  * @idx: the minor number
1222  *
1223  * Return: the tty, if found. If not found, return %NULL or ERR_PTR() if the
1224  * driver lookup() method returns an error.
1225  *
1226  * Locking: tty_mutex must be held. If the tty is found, bump the tty kref.
1227  */
tty_driver_lookup_tty(struct tty_driver * driver,struct file * file,int idx)1228 static struct tty_struct *tty_driver_lookup_tty(struct tty_driver *driver,
1229 		struct file *file, int idx)
1230 {
1231 	struct tty_struct *tty;
1232 
1233 	if (driver->ops->lookup)
1234 		if (!file)
1235 			tty = ERR_PTR(-EIO);
1236 		else
1237 			tty = driver->ops->lookup(driver, file, idx);
1238 	else
1239 		tty = driver->ttys[idx];
1240 
1241 	if (!IS_ERR(tty))
1242 		tty_kref_get(tty);
1243 	return tty;
1244 }
1245 
1246 /**
1247  * tty_init_termios	-  helper for termios setup
1248  * @tty: the tty to set up
1249  *
1250  * Initialise the termios structure for this tty. This runs under the
1251  * %tty_mutex currently so we can be relaxed about ordering.
1252  */
tty_init_termios(struct tty_struct * tty)1253 void tty_init_termios(struct tty_struct *tty)
1254 {
1255 	struct ktermios *tp;
1256 	int idx = tty->index;
1257 
1258 	if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS)
1259 		tty->termios = tty->driver->init_termios;
1260 	else {
1261 		/* Check for lazy saved data */
1262 		tp = tty->driver->termios[idx];
1263 		if (tp != NULL) {
1264 			tty->termios = *tp;
1265 			tty->termios.c_line  = tty->driver->init_termios.c_line;
1266 		} else
1267 			tty->termios = tty->driver->init_termios;
1268 	}
1269 	/* Compatibility until drivers always set this */
1270 	tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios);
1271 	tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios);
1272 }
1273 EXPORT_SYMBOL_GPL(tty_init_termios);
1274 
1275 /**
1276  * tty_standard_install - usual tty->ops->install
1277  * @driver: the driver for the tty
1278  * @tty: the tty
1279  *
1280  * If the @driver overrides @tty->ops->install, it still can call this function
1281  * to perform the standard install operations.
1282  */
tty_standard_install(struct tty_driver * driver,struct tty_struct * tty)1283 int tty_standard_install(struct tty_driver *driver, struct tty_struct *tty)
1284 {
1285 	tty_init_termios(tty);
1286 	tty_driver_kref_get(driver);
1287 	tty->count++;
1288 	driver->ttys[tty->index] = tty;
1289 	return 0;
1290 }
1291 EXPORT_SYMBOL_GPL(tty_standard_install);
1292 
1293 /**
1294  * tty_driver_install_tty() - install a tty entry in the driver
1295  * @driver: the driver for the tty
1296  * @tty: the tty
1297  *
1298  * Install a tty object into the driver tables. The @tty->index field will be
1299  * set by the time this is called. This method is responsible for ensuring any
1300  * need additional structures are allocated and configured.
1301  *
1302  * Locking: tty_mutex for now
1303  */
tty_driver_install_tty(struct tty_driver * driver,struct tty_struct * tty)1304 static int tty_driver_install_tty(struct tty_driver *driver,
1305 						struct tty_struct *tty)
1306 {
1307 	return driver->ops->install ? driver->ops->install(driver, tty) :
1308 		tty_standard_install(driver, tty);
1309 }
1310 
1311 /**
1312  * tty_driver_remove_tty() - remove a tty from the driver tables
1313  * @driver: the driver for the tty
1314  * @tty: tty to remove
1315  *
1316  * Remove a tty object from the driver tables. The tty->index field will be set
1317  * by the time this is called.
1318  *
1319  * Locking: tty_mutex for now
1320  */
tty_driver_remove_tty(struct tty_driver * driver,struct tty_struct * tty)1321 static void tty_driver_remove_tty(struct tty_driver *driver, struct tty_struct *tty)
1322 {
1323 	if (driver->ops->remove)
1324 		driver->ops->remove(driver, tty);
1325 	else
1326 		driver->ttys[tty->index] = NULL;
1327 }
1328 
1329 /**
1330  * tty_reopen()	- fast re-open of an open tty
1331  * @tty: the tty to open
1332  *
1333  * Re-opens on master ptys are not allowed and return -%EIO.
1334  *
1335  * Locking: Caller must hold tty_lock
1336  * Return: 0 on success, -errno on error.
1337  */
tty_reopen(struct tty_struct * tty)1338 static int tty_reopen(struct tty_struct *tty)
1339 {
1340 	struct tty_driver *driver = tty->driver;
1341 	struct tty_ldisc *ld;
1342 	int retval = 0;
1343 
1344 	if (driver->type == TTY_DRIVER_TYPE_PTY &&
1345 	    driver->subtype == PTY_TYPE_MASTER)
1346 		return -EIO;
1347 
1348 	if (!tty->count)
1349 		return -EAGAIN;
1350 
1351 	if (test_bit(TTY_EXCLUSIVE, &tty->flags) && !capable(CAP_SYS_ADMIN))
1352 		return -EBUSY;
1353 
1354 	ld = tty_ldisc_ref_wait(tty);
1355 	if (ld) {
1356 		tty_ldisc_deref(ld);
1357 	} else {
1358 		retval = tty_ldisc_lock(tty, 5 * HZ);
1359 		if (retval)
1360 			return retval;
1361 
1362 		if (!tty->ldisc)
1363 			retval = tty_ldisc_reinit(tty, tty->termios.c_line);
1364 		tty_ldisc_unlock(tty);
1365 	}
1366 
1367 	if (retval == 0)
1368 		tty->count++;
1369 
1370 	return retval;
1371 }
1372 
1373 /**
1374  * tty_init_dev		-	initialise a tty device
1375  * @driver: tty driver we are opening a device on
1376  * @idx: device index
1377  *
1378  * Prepare a tty device. This may not be a "new" clean device but could also be
1379  * an active device. The pty drivers require special handling because of this.
1380  *
1381  * Locking:
1382  *	The function is called under the tty_mutex, which protects us from the
1383  *	tty struct or driver itself going away.
1384  *
1385  * On exit the tty device has the line discipline attached and a reference
1386  * count of 1. If a pair was created for pty/tty use and the other was a pty
1387  * master then it too has a reference count of 1.
1388  *
1389  * WSH 06/09/97: Rewritten to remove races and properly clean up after a failed
1390  * open. The new code protects the open with a mutex, so it's really quite
1391  * straightforward. The mutex locking can probably be relaxed for the (most
1392  * common) case of reopening a tty.
1393  *
1394  * Return: new tty structure
1395  */
tty_init_dev(struct tty_driver * driver,int idx)1396 struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx)
1397 {
1398 	struct tty_struct *tty;
1399 	int retval;
1400 
1401 	/*
1402 	 * First time open is complex, especially for PTY devices.
1403 	 * This code guarantees that either everything succeeds and the
1404 	 * TTY is ready for operation, or else the table slots are vacated
1405 	 * and the allocated memory released.  (Except that the termios
1406 	 * may be retained.)
1407 	 */
1408 
1409 	if (!try_module_get(driver->owner))
1410 		return ERR_PTR(-ENODEV);
1411 
1412 	tty = alloc_tty_struct(driver, idx);
1413 	if (!tty) {
1414 		retval = -ENOMEM;
1415 		goto err_module_put;
1416 	}
1417 
1418 	tty_lock(tty);
1419 	retval = tty_driver_install_tty(driver, tty);
1420 	if (retval < 0)
1421 		goto err_free_tty;
1422 
1423 	if (!tty->port)
1424 		tty->port = driver->ports[idx];
1425 
1426 	if (WARN_RATELIMIT(!tty->port,
1427 			"%s: %s driver does not set tty->port. This would crash the kernel. Fix the driver!\n",
1428 			__func__, tty->driver->name)) {
1429 		retval = -EINVAL;
1430 		goto err_release_lock;
1431 	}
1432 
1433 	retval = tty_ldisc_lock(tty, 5 * HZ);
1434 	if (retval)
1435 		goto err_release_lock;
1436 	tty->port->itty = tty;
1437 
1438 	/*
1439 	 * Structures all installed ... call the ldisc open routines.
1440 	 * If we fail here just call release_tty to clean up.  No need
1441 	 * to decrement the use counts, as release_tty doesn't care.
1442 	 */
1443 	retval = tty_ldisc_setup(tty, tty->link);
1444 	if (retval)
1445 		goto err_release_tty;
1446 	tty_ldisc_unlock(tty);
1447 	/* Return the tty locked so that it cannot vanish under the caller */
1448 	return tty;
1449 
1450 err_free_tty:
1451 	tty_unlock(tty);
1452 	free_tty_struct(tty);
1453 err_module_put:
1454 	module_put(driver->owner);
1455 	return ERR_PTR(retval);
1456 
1457 	/* call the tty release_tty routine to clean out this slot */
1458 err_release_tty:
1459 	tty_ldisc_unlock(tty);
1460 	tty_info_ratelimited(tty, "ldisc open failed (%d), clearing slot %d\n",
1461 			     retval, idx);
1462 err_release_lock:
1463 	tty_unlock(tty);
1464 	release_tty(tty, idx);
1465 	return ERR_PTR(retval);
1466 }
1467 
1468 /**
1469  * tty_save_termios() - save tty termios data in driver table
1470  * @tty: tty whose termios data to save
1471  *
1472  * Locking: Caller guarantees serialisation with tty_init_termios().
1473  */
tty_save_termios(struct tty_struct * tty)1474 void tty_save_termios(struct tty_struct *tty)
1475 {
1476 	struct ktermios *tp;
1477 	int idx = tty->index;
1478 
1479 	/* If the port is going to reset then it has no termios to save */
1480 	if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS)
1481 		return;
1482 
1483 	/* Stash the termios data */
1484 	tp = tty->driver->termios[idx];
1485 	if (tp == NULL) {
1486 		tp = kmalloc(sizeof(*tp), GFP_KERNEL);
1487 		if (tp == NULL)
1488 			return;
1489 		tty->driver->termios[idx] = tp;
1490 	}
1491 	*tp = tty->termios;
1492 }
1493 EXPORT_SYMBOL_GPL(tty_save_termios);
1494 
1495 /**
1496  * tty_flush_works	-	flush all works of a tty/pty pair
1497  * @tty: tty device to flush works for (or either end of a pty pair)
1498  *
1499  * Sync flush all works belonging to @tty (and the 'other' tty).
1500  */
tty_flush_works(struct tty_struct * tty)1501 static void tty_flush_works(struct tty_struct *tty)
1502 {
1503 	flush_work(&tty->SAK_work);
1504 	flush_work(&tty->hangup_work);
1505 	if (tty->link) {
1506 		flush_work(&tty->link->SAK_work);
1507 		flush_work(&tty->link->hangup_work);
1508 	}
1509 }
1510 
1511 /**
1512  * release_one_tty	-	release tty structure memory
1513  * @work: work of tty we are obliterating
1514  *
1515  * Releases memory associated with a tty structure, and clears out the
1516  * driver table slots. This function is called when a device is no longer
1517  * in use. It also gets called when setup of a device fails.
1518  *
1519  * Locking:
1520  *	takes the file list lock internally when working on the list of ttys
1521  *	that the driver keeps.
1522  *
1523  * This method gets called from a work queue so that the driver private
1524  * cleanup ops can sleep (needed for USB at least)
1525  */
release_one_tty(struct work_struct * work)1526 static void release_one_tty(struct work_struct *work)
1527 {
1528 	struct tty_struct *tty =
1529 		container_of(work, struct tty_struct, hangup_work);
1530 	struct tty_driver *driver = tty->driver;
1531 	struct module *owner = driver->owner;
1532 
1533 	if (tty->ops->cleanup)
1534 		tty->ops->cleanup(tty);
1535 
1536 	tty->magic = 0;
1537 	tty_driver_kref_put(driver);
1538 	module_put(owner);
1539 
1540 	spin_lock(&tty->files_lock);
1541 	list_del_init(&tty->tty_files);
1542 	spin_unlock(&tty->files_lock);
1543 
1544 	put_pid(tty->ctrl.pgrp);
1545 	put_pid(tty->ctrl.session);
1546 	free_tty_struct(tty);
1547 }
1548 
queue_release_one_tty(struct kref * kref)1549 static void queue_release_one_tty(struct kref *kref)
1550 {
1551 	struct tty_struct *tty = container_of(kref, struct tty_struct, kref);
1552 
1553 	/* The hangup queue is now free so we can reuse it rather than
1554 	 *  waste a chunk of memory for each port.
1555 	 */
1556 	INIT_WORK(&tty->hangup_work, release_one_tty);
1557 	schedule_work(&tty->hangup_work);
1558 }
1559 
1560 /**
1561  * tty_kref_put		-	release a tty kref
1562  * @tty: tty device
1563  *
1564  * Release a reference to the @tty device and if need be let the kref layer
1565  * destruct the object for us.
1566  */
tty_kref_put(struct tty_struct * tty)1567 void tty_kref_put(struct tty_struct *tty)
1568 {
1569 	if (tty)
1570 		kref_put(&tty->kref, queue_release_one_tty);
1571 }
1572 EXPORT_SYMBOL(tty_kref_put);
1573 
1574 /**
1575  * release_tty		-	release tty structure memory
1576  * @tty: tty device release
1577  * @idx: index of the tty device release
1578  *
1579  * Release both @tty and a possible linked partner (think pty pair),
1580  * and decrement the refcount of the backing module.
1581  *
1582  * Locking:
1583  *	tty_mutex
1584  *	takes the file list lock internally when working on the list of ttys
1585  *	that the driver keeps.
1586  */
release_tty(struct tty_struct * tty,int idx)1587 static void release_tty(struct tty_struct *tty, int idx)
1588 {
1589 	/* This should always be true but check for the moment */
1590 	WARN_ON(tty->index != idx);
1591 	WARN_ON(!mutex_is_locked(&tty_mutex));
1592 	if (tty->ops->shutdown)
1593 		tty->ops->shutdown(tty);
1594 	tty_save_termios(tty);
1595 	tty_driver_remove_tty(tty->driver, tty);
1596 	if (tty->port)
1597 		tty->port->itty = NULL;
1598 	if (tty->link)
1599 		tty->link->port->itty = NULL;
1600 	if (tty->port)
1601 		tty_buffer_cancel_work(tty->port);
1602 	if (tty->link)
1603 		tty_buffer_cancel_work(tty->link->port);
1604 
1605 	tty_kref_put(tty->link);
1606 	tty_kref_put(tty);
1607 }
1608 
1609 /**
1610  * tty_release_checks - check a tty before real release
1611  * @tty: tty to check
1612  * @idx: index of the tty
1613  *
1614  * Performs some paranoid checking before true release of the @tty. This is a
1615  * no-op unless %TTY_PARANOIA_CHECK is defined.
1616  */
tty_release_checks(struct tty_struct * tty,int idx)1617 static int tty_release_checks(struct tty_struct *tty, int idx)
1618 {
1619 #ifdef TTY_PARANOIA_CHECK
1620 	if (idx < 0 || idx >= tty->driver->num) {
1621 		tty_debug(tty, "bad idx %d\n", idx);
1622 		return -1;
1623 	}
1624 
1625 	/* not much to check for devpts */
1626 	if (tty->driver->flags & TTY_DRIVER_DEVPTS_MEM)
1627 		return 0;
1628 
1629 	if (tty != tty->driver->ttys[idx]) {
1630 		tty_debug(tty, "bad driver table[%d] = %p\n",
1631 			  idx, tty->driver->ttys[idx]);
1632 		return -1;
1633 	}
1634 	if (tty->driver->other) {
1635 		struct tty_struct *o_tty = tty->link;
1636 
1637 		if (o_tty != tty->driver->other->ttys[idx]) {
1638 			tty_debug(tty, "bad other table[%d] = %p\n",
1639 				  idx, tty->driver->other->ttys[idx]);
1640 			return -1;
1641 		}
1642 		if (o_tty->link != tty) {
1643 			tty_debug(tty, "bad link = %p\n", o_tty->link);
1644 			return -1;
1645 		}
1646 	}
1647 #endif
1648 	return 0;
1649 }
1650 
1651 /**
1652  * tty_kclose      -       closes tty opened by tty_kopen
1653  * @tty: tty device
1654  *
1655  * Performs the final steps to release and free a tty device. It is the same as
1656  * tty_release_struct() except that it also resets %TTY_PORT_KOPENED flag on
1657  * @tty->port.
1658  */
tty_kclose(struct tty_struct * tty)1659 void tty_kclose(struct tty_struct *tty)
1660 {
1661 	/*
1662 	 * Ask the line discipline code to release its structures
1663 	 */
1664 	tty_ldisc_release(tty);
1665 
1666 	/* Wait for pending work before tty destruction commmences */
1667 	tty_flush_works(tty);
1668 
1669 	tty_debug_hangup(tty, "freeing structure\n");
1670 	/*
1671 	 * The release_tty function takes care of the details of clearing
1672 	 * the slots and preserving the termios structure.
1673 	 */
1674 	mutex_lock(&tty_mutex);
1675 	tty_port_set_kopened(tty->port, 0);
1676 	release_tty(tty, tty->index);
1677 	mutex_unlock(&tty_mutex);
1678 }
1679 EXPORT_SYMBOL_GPL(tty_kclose);
1680 
1681 /**
1682  * tty_release_struct	-	release a tty struct
1683  * @tty: tty device
1684  * @idx: index of the tty
1685  *
1686  * Performs the final steps to release and free a tty device. It is roughly the
1687  * reverse of tty_init_dev().
1688  */
tty_release_struct(struct tty_struct * tty,int idx)1689 void tty_release_struct(struct tty_struct *tty, int idx)
1690 {
1691 	/*
1692 	 * Ask the line discipline code to release its structures
1693 	 */
1694 	tty_ldisc_release(tty);
1695 
1696 	/* Wait for pending work before tty destruction commmences */
1697 	tty_flush_works(tty);
1698 
1699 	tty_debug_hangup(tty, "freeing structure\n");
1700 	/*
1701 	 * The release_tty function takes care of the details of clearing
1702 	 * the slots and preserving the termios structure.
1703 	 */
1704 	mutex_lock(&tty_mutex);
1705 	release_tty(tty, idx);
1706 	mutex_unlock(&tty_mutex);
1707 }
1708 EXPORT_SYMBOL_GPL(tty_release_struct);
1709 
1710 /**
1711  * tty_release		-	vfs callback for close
1712  * @inode: inode of tty
1713  * @filp: file pointer for handle to tty
1714  *
1715  * Called the last time each file handle is closed that references this tty.
1716  * There may however be several such references.
1717  *
1718  * Locking:
1719  *	Takes BKL. See tty_release_dev().
1720  *
1721  * Even releasing the tty structures is a tricky business. We have to be very
1722  * careful that the structures are all released at the same time, as interrupts
1723  * might otherwise get the wrong pointers.
1724  *
1725  * WSH 09/09/97: rewritten to avoid some nasty race conditions that could
1726  * lead to double frees or releasing memory still in use.
1727  */
tty_release(struct inode * inode,struct file * filp)1728 int tty_release(struct inode *inode, struct file *filp)
1729 {
1730 	struct tty_struct *tty = file_tty(filp);
1731 	struct tty_struct *o_tty = NULL;
1732 	int	do_sleep, final;
1733 	int	idx;
1734 	long	timeout = 0;
1735 	int	once = 1;
1736 
1737 	if (tty_paranoia_check(tty, inode, __func__))
1738 		return 0;
1739 
1740 	tty_lock(tty);
1741 	check_tty_count(tty, __func__);
1742 
1743 	__tty_fasync(-1, filp, 0);
1744 
1745 	idx = tty->index;
1746 	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
1747 	    tty->driver->subtype == PTY_TYPE_MASTER)
1748 		o_tty = tty->link;
1749 
1750 	if (tty_release_checks(tty, idx)) {
1751 		tty_unlock(tty);
1752 		return 0;
1753 	}
1754 
1755 	tty_debug_hangup(tty, "releasing (count=%d)\n", tty->count);
1756 
1757 	if (tty->ops->close)
1758 		tty->ops->close(tty, filp);
1759 
1760 	/* If tty is pty master, lock the slave pty (stable lock order) */
1761 	tty_lock_slave(o_tty);
1762 
1763 	/*
1764 	 * Sanity check: if tty->count is going to zero, there shouldn't be
1765 	 * any waiters on tty->read_wait or tty->write_wait.  We test the
1766 	 * wait queues and kick everyone out _before_ actually starting to
1767 	 * close.  This ensures that we won't block while releasing the tty
1768 	 * structure.
1769 	 *
1770 	 * The test for the o_tty closing is necessary, since the master and
1771 	 * slave sides may close in any order.  If the slave side closes out
1772 	 * first, its count will be one, since the master side holds an open.
1773 	 * Thus this test wouldn't be triggered at the time the slave closed,
1774 	 * so we do it now.
1775 	 */
1776 	while (1) {
1777 		do_sleep = 0;
1778 
1779 		if (tty->count <= 1) {
1780 			if (waitqueue_active(&tty->read_wait)) {
1781 				wake_up_poll(&tty->read_wait, EPOLLIN);
1782 				do_sleep++;
1783 			}
1784 			if (waitqueue_active(&tty->write_wait)) {
1785 				wake_up_poll(&tty->write_wait, EPOLLOUT);
1786 				do_sleep++;
1787 			}
1788 		}
1789 		if (o_tty && o_tty->count <= 1) {
1790 			if (waitqueue_active(&o_tty->read_wait)) {
1791 				wake_up_poll(&o_tty->read_wait, EPOLLIN);
1792 				do_sleep++;
1793 			}
1794 			if (waitqueue_active(&o_tty->write_wait)) {
1795 				wake_up_poll(&o_tty->write_wait, EPOLLOUT);
1796 				do_sleep++;
1797 			}
1798 		}
1799 		if (!do_sleep)
1800 			break;
1801 
1802 		if (once) {
1803 			once = 0;
1804 			tty_warn(tty, "read/write wait queue active!\n");
1805 		}
1806 		schedule_timeout_killable(timeout);
1807 		if (timeout < 120 * HZ)
1808 			timeout = 2 * timeout + 1;
1809 		else
1810 			timeout = MAX_SCHEDULE_TIMEOUT;
1811 	}
1812 
1813 	if (o_tty) {
1814 		if (--o_tty->count < 0) {
1815 			tty_warn(tty, "bad slave count (%d)\n", o_tty->count);
1816 			o_tty->count = 0;
1817 		}
1818 	}
1819 	if (--tty->count < 0) {
1820 		tty_warn(tty, "bad tty->count (%d)\n", tty->count);
1821 		tty->count = 0;
1822 	}
1823 
1824 	/*
1825 	 * We've decremented tty->count, so we need to remove this file
1826 	 * descriptor off the tty->tty_files list; this serves two
1827 	 * purposes:
1828 	 *  - check_tty_count sees the correct number of file descriptors
1829 	 *    associated with this tty.
1830 	 *  - do_tty_hangup no longer sees this file descriptor as
1831 	 *    something that needs to be handled for hangups.
1832 	 */
1833 	tty_del_file(filp);
1834 
1835 	/*
1836 	 * Perform some housekeeping before deciding whether to return.
1837 	 *
1838 	 * If _either_ side is closing, make sure there aren't any
1839 	 * processes that still think tty or o_tty is their controlling
1840 	 * tty.
1841 	 */
1842 	if (!tty->count) {
1843 		read_lock(&tasklist_lock);
1844 		session_clear_tty(tty->ctrl.session);
1845 		if (o_tty)
1846 			session_clear_tty(o_tty->ctrl.session);
1847 		read_unlock(&tasklist_lock);
1848 	}
1849 
1850 	/* check whether both sides are closing ... */
1851 	final = !tty->count && !(o_tty && o_tty->count);
1852 
1853 	tty_unlock_slave(o_tty);
1854 	tty_unlock(tty);
1855 
1856 	/* At this point, the tty->count == 0 should ensure a dead tty
1857 	 * cannot be re-opened by a racing opener.
1858 	 */
1859 
1860 	if (!final)
1861 		return 0;
1862 
1863 	tty_debug_hangup(tty, "final close\n");
1864 
1865 	tty_release_struct(tty, idx);
1866 	return 0;
1867 }
1868 
1869 /**
1870  * tty_open_current_tty - get locked tty of current task
1871  * @device: device number
1872  * @filp: file pointer to tty
1873  * @return: locked tty of the current task iff @device is /dev/tty
1874  *
1875  * Performs a re-open of the current task's controlling tty.
1876  *
1877  * We cannot return driver and index like for the other nodes because devpts
1878  * will not work then. It expects inodes to be from devpts FS.
1879  */
tty_open_current_tty(dev_t device,struct file * filp)1880 static struct tty_struct *tty_open_current_tty(dev_t device, struct file *filp)
1881 {
1882 	struct tty_struct *tty;
1883 	int retval;
1884 
1885 	if (device != MKDEV(TTYAUX_MAJOR, 0))
1886 		return NULL;
1887 
1888 	tty = get_current_tty();
1889 	if (!tty)
1890 		return ERR_PTR(-ENXIO);
1891 
1892 	filp->f_flags |= O_NONBLOCK; /* Don't let /dev/tty block */
1893 	/* noctty = 1; */
1894 	tty_lock(tty);
1895 	tty_kref_put(tty);	/* safe to drop the kref now */
1896 
1897 	retval = tty_reopen(tty);
1898 	if (retval < 0) {
1899 		tty_unlock(tty);
1900 		tty = ERR_PTR(retval);
1901 	}
1902 	return tty;
1903 }
1904 
1905 /**
1906  * tty_lookup_driver - lookup a tty driver for a given device file
1907  * @device: device number
1908  * @filp: file pointer to tty
1909  * @index: index for the device in the @return driver
1910  *
1911  * If returned value is not erroneous, the caller is responsible to decrement
1912  * the refcount by tty_driver_kref_put().
1913  *
1914  * Locking: %tty_mutex protects get_tty_driver()
1915  *
1916  * Return: driver for this inode (with increased refcount)
1917  */
tty_lookup_driver(dev_t device,struct file * filp,int * index)1918 static struct tty_driver *tty_lookup_driver(dev_t device, struct file *filp,
1919 		int *index)
1920 {
1921 	struct tty_driver *driver = NULL;
1922 
1923 	switch (device) {
1924 #ifdef CONFIG_VT
1925 	case MKDEV(TTY_MAJOR, 0): {
1926 		extern struct tty_driver *console_driver;
1927 
1928 		driver = tty_driver_kref_get(console_driver);
1929 		*index = fg_console;
1930 		break;
1931 	}
1932 #endif
1933 	case MKDEV(TTYAUX_MAJOR, 1): {
1934 		struct tty_driver *console_driver = console_device(index);
1935 
1936 		if (console_driver) {
1937 			driver = tty_driver_kref_get(console_driver);
1938 			if (driver && filp) {
1939 				/* Don't let /dev/console block */
1940 				filp->f_flags |= O_NONBLOCK;
1941 				break;
1942 			}
1943 		}
1944 		if (driver)
1945 			tty_driver_kref_put(driver);
1946 		return ERR_PTR(-ENODEV);
1947 	}
1948 	default:
1949 		driver = get_tty_driver(device, index);
1950 		if (!driver)
1951 			return ERR_PTR(-ENODEV);
1952 		break;
1953 	}
1954 	return driver;
1955 }
1956 
tty_kopen(dev_t device,int shared)1957 static struct tty_struct *tty_kopen(dev_t device, int shared)
1958 {
1959 	struct tty_struct *tty;
1960 	struct tty_driver *driver;
1961 	int index = -1;
1962 
1963 	mutex_lock(&tty_mutex);
1964 	driver = tty_lookup_driver(device, NULL, &index);
1965 	if (IS_ERR(driver)) {
1966 		mutex_unlock(&tty_mutex);
1967 		return ERR_CAST(driver);
1968 	}
1969 
1970 	/* check whether we're reopening an existing tty */
1971 	tty = tty_driver_lookup_tty(driver, NULL, index);
1972 	if (IS_ERR(tty) || shared)
1973 		goto out;
1974 
1975 	if (tty) {
1976 		/* drop kref from tty_driver_lookup_tty() */
1977 		tty_kref_put(tty);
1978 		tty = ERR_PTR(-EBUSY);
1979 	} else { /* tty_init_dev returns tty with the tty_lock held */
1980 		tty = tty_init_dev(driver, index);
1981 		if (IS_ERR(tty))
1982 			goto out;
1983 		tty_port_set_kopened(tty->port, 1);
1984 	}
1985 out:
1986 	mutex_unlock(&tty_mutex);
1987 	tty_driver_kref_put(driver);
1988 	return tty;
1989 }
1990 
1991 /**
1992  * tty_kopen_exclusive	-	open a tty device for kernel
1993  * @device: dev_t of device to open
1994  *
1995  * Opens tty exclusively for kernel. Performs the driver lookup, makes sure
1996  * it's not already opened and performs the first-time tty initialization.
1997  *
1998  * Claims the global %tty_mutex to serialize:
1999  *  * concurrent first-time tty initialization
2000  *  * concurrent tty driver removal w/ lookup
2001  *  * concurrent tty removal from driver table
2002  *
2003  * Return: the locked initialized &tty_struct
2004  */
tty_kopen_exclusive(dev_t device)2005 struct tty_struct *tty_kopen_exclusive(dev_t device)
2006 {
2007 	return tty_kopen(device, 0);
2008 }
2009 EXPORT_SYMBOL_GPL(tty_kopen_exclusive);
2010 
2011 /**
2012  * tty_kopen_shared	-	open a tty device for shared in-kernel use
2013  * @device: dev_t of device to open
2014  *
2015  * Opens an already existing tty for in-kernel use. Compared to
2016  * tty_kopen_exclusive() above it doesn't ensure to be the only user.
2017  *
2018  * Locking: identical to tty_kopen() above.
2019  */
tty_kopen_shared(dev_t device)2020 struct tty_struct *tty_kopen_shared(dev_t device)
2021 {
2022 	return tty_kopen(device, 1);
2023 }
2024 EXPORT_SYMBOL_GPL(tty_kopen_shared);
2025 
2026 /**
2027  * tty_open_by_driver	-	open a tty device
2028  * @device: dev_t of device to open
2029  * @filp: file pointer to tty
2030  *
2031  * Performs the driver lookup, checks for a reopen, or otherwise performs the
2032  * first-time tty initialization.
2033  *
2034  *
2035  * Claims the global tty_mutex to serialize:
2036  *  * concurrent first-time tty initialization
2037  *  * concurrent tty driver removal w/ lookup
2038  *  * concurrent tty removal from driver table
2039  *
2040  * Return: the locked initialized or re-opened &tty_struct
2041  */
tty_open_by_driver(dev_t device,struct file * filp)2042 static struct tty_struct *tty_open_by_driver(dev_t device,
2043 					     struct file *filp)
2044 {
2045 	struct tty_struct *tty;
2046 	struct tty_driver *driver = NULL;
2047 	int index = -1;
2048 	int retval;
2049 
2050 	mutex_lock(&tty_mutex);
2051 	driver = tty_lookup_driver(device, filp, &index);
2052 	if (IS_ERR(driver)) {
2053 		mutex_unlock(&tty_mutex);
2054 		return ERR_CAST(driver);
2055 	}
2056 
2057 	/* check whether we're reopening an existing tty */
2058 	tty = tty_driver_lookup_tty(driver, filp, index);
2059 	if (IS_ERR(tty)) {
2060 		mutex_unlock(&tty_mutex);
2061 		goto out;
2062 	}
2063 
2064 	if (tty) {
2065 		if (tty_port_kopened(tty->port)) {
2066 			tty_kref_put(tty);
2067 			mutex_unlock(&tty_mutex);
2068 			tty = ERR_PTR(-EBUSY);
2069 			goto out;
2070 		}
2071 		mutex_unlock(&tty_mutex);
2072 		retval = tty_lock_interruptible(tty);
2073 		tty_kref_put(tty);  /* drop kref from tty_driver_lookup_tty() */
2074 		if (retval) {
2075 			if (retval == -EINTR)
2076 				retval = -ERESTARTSYS;
2077 			tty = ERR_PTR(retval);
2078 			goto out;
2079 		}
2080 		retval = tty_reopen(tty);
2081 		if (retval < 0) {
2082 			tty_unlock(tty);
2083 			tty = ERR_PTR(retval);
2084 		}
2085 	} else { /* Returns with the tty_lock held for now */
2086 		tty = tty_init_dev(driver, index);
2087 		mutex_unlock(&tty_mutex);
2088 	}
2089 out:
2090 	tty_driver_kref_put(driver);
2091 	return tty;
2092 }
2093 
2094 /**
2095  * tty_open	-	open a tty device
2096  * @inode: inode of device file
2097  * @filp: file pointer to tty
2098  *
2099  * tty_open() and tty_release() keep up the tty count that contains the number
2100  * of opens done on a tty. We cannot use the inode-count, as different inodes
2101  * might point to the same tty.
2102  *
2103  * Open-counting is needed for pty masters, as well as for keeping track of
2104  * serial lines: DTR is dropped when the last close happens.
2105  * (This is not done solely through tty->count, now.  - Ted 1/27/92)
2106  *
2107  * The termios state of a pty is reset on the first open so that settings don't
2108  * persist across reuse.
2109  *
2110  * Locking:
2111  *  * %tty_mutex protects tty, tty_lookup_driver() and tty_init_dev().
2112  *  * @tty->count should protect the rest.
2113  *  * ->siglock protects ->signal/->sighand
2114  *
2115  * Note: the tty_unlock/lock cases without a ref are only safe due to %tty_mutex
2116  */
tty_open(struct inode * inode,struct file * filp)2117 static int tty_open(struct inode *inode, struct file *filp)
2118 {
2119 	struct tty_struct *tty;
2120 	int noctty, retval;
2121 	dev_t device = inode->i_rdev;
2122 	unsigned saved_flags = filp->f_flags;
2123 
2124 	nonseekable_open(inode, filp);
2125 
2126 retry_open:
2127 	retval = tty_alloc_file(filp);
2128 	if (retval)
2129 		return -ENOMEM;
2130 
2131 	tty = tty_open_current_tty(device, filp);
2132 	if (!tty)
2133 		tty = tty_open_by_driver(device, filp);
2134 
2135 	if (IS_ERR(tty)) {
2136 		tty_free_file(filp);
2137 		retval = PTR_ERR(tty);
2138 		if (retval != -EAGAIN || signal_pending(current))
2139 			return retval;
2140 		schedule();
2141 		goto retry_open;
2142 	}
2143 
2144 	tty_add_file(tty, filp);
2145 
2146 	check_tty_count(tty, __func__);
2147 	tty_debug_hangup(tty, "opening (count=%d)\n", tty->count);
2148 
2149 	if (tty->ops->open)
2150 		retval = tty->ops->open(tty, filp);
2151 	else
2152 		retval = -ENODEV;
2153 	filp->f_flags = saved_flags;
2154 
2155 	if (retval) {
2156 		tty_debug_hangup(tty, "open error %d, releasing\n", retval);
2157 
2158 		tty_unlock(tty); /* need to call tty_release without BTM */
2159 		tty_release(inode, filp);
2160 		if (retval != -ERESTARTSYS)
2161 			return retval;
2162 
2163 		if (signal_pending(current))
2164 			return retval;
2165 
2166 		schedule();
2167 		/*
2168 		 * Need to reset f_op in case a hangup happened.
2169 		 */
2170 		if (tty_hung_up_p(filp))
2171 			filp->f_op = &tty_fops;
2172 		goto retry_open;
2173 	}
2174 	clear_bit(TTY_HUPPED, &tty->flags);
2175 
2176 	noctty = (filp->f_flags & O_NOCTTY) ||
2177 		 (IS_ENABLED(CONFIG_VT) && device == MKDEV(TTY_MAJOR, 0)) ||
2178 		 device == MKDEV(TTYAUX_MAJOR, 1) ||
2179 		 (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
2180 		  tty->driver->subtype == PTY_TYPE_MASTER);
2181 	if (!noctty)
2182 		tty_open_proc_set_tty(filp, tty);
2183 	tty_unlock(tty);
2184 	return 0;
2185 }
2186 
2187 
2188 /**
2189  * tty_poll	-	check tty status
2190  * @filp: file being polled
2191  * @wait: poll wait structures to update
2192  *
2193  * Call the line discipline polling method to obtain the poll status of the
2194  * device.
2195  *
2196  * Locking: locks called line discipline but ldisc poll method may be
2197  * re-entered freely by other callers.
2198  */
tty_poll(struct file * filp,poll_table * wait)2199 static __poll_t tty_poll(struct file *filp, poll_table *wait)
2200 {
2201 	struct tty_struct *tty = file_tty(filp);
2202 	struct tty_ldisc *ld;
2203 	__poll_t ret = 0;
2204 
2205 	if (tty_paranoia_check(tty, file_inode(filp), "tty_poll"))
2206 		return 0;
2207 
2208 	ld = tty_ldisc_ref_wait(tty);
2209 	if (!ld)
2210 		return hung_up_tty_poll(filp, wait);
2211 	if (ld->ops->poll)
2212 		ret = ld->ops->poll(tty, filp, wait);
2213 	tty_ldisc_deref(ld);
2214 	return ret;
2215 }
2216 
__tty_fasync(int fd,struct file * filp,int on)2217 static int __tty_fasync(int fd, struct file *filp, int on)
2218 {
2219 	struct tty_struct *tty = file_tty(filp);
2220 	unsigned long flags;
2221 	int retval = 0;
2222 
2223 	if (tty_paranoia_check(tty, file_inode(filp), "tty_fasync"))
2224 		goto out;
2225 
2226 	retval = fasync_helper(fd, filp, on, &tty->fasync);
2227 	if (retval <= 0)
2228 		goto out;
2229 
2230 	if (on) {
2231 		enum pid_type type;
2232 		struct pid *pid;
2233 
2234 		spin_lock_irqsave(&tty->ctrl.lock, flags);
2235 		if (tty->ctrl.pgrp) {
2236 			pid = tty->ctrl.pgrp;
2237 			type = PIDTYPE_PGID;
2238 		} else {
2239 			pid = task_pid(current);
2240 			type = PIDTYPE_TGID;
2241 		}
2242 		get_pid(pid);
2243 		spin_unlock_irqrestore(&tty->ctrl.lock, flags);
2244 		__f_setown(filp, pid, type, 0);
2245 		put_pid(pid);
2246 		retval = 0;
2247 	}
2248 out:
2249 	return retval;
2250 }
2251 
tty_fasync(int fd,struct file * filp,int on)2252 static int tty_fasync(int fd, struct file *filp, int on)
2253 {
2254 	struct tty_struct *tty = file_tty(filp);
2255 	int retval = -ENOTTY;
2256 
2257 	tty_lock(tty);
2258 	if (!tty_hung_up_p(filp))
2259 		retval = __tty_fasync(fd, filp, on);
2260 	tty_unlock(tty);
2261 
2262 	return retval;
2263 }
2264 
2265 /**
2266  * tiocsti		-	fake input character
2267  * @tty: tty to fake input into
2268  * @p: pointer to character
2269  *
2270  * Fake input to a tty device. Does the necessary locking and input management.
2271  *
2272  * FIXME: does not honour flow control ??
2273  *
2274  * Locking:
2275  *  * Called functions take tty_ldiscs_lock
2276  *  * current->signal->tty check is safe without locks
2277  */
tiocsti(struct tty_struct * tty,char __user * p)2278 static int tiocsti(struct tty_struct *tty, char __user *p)
2279 {
2280 	char ch, mbz = 0;
2281 	struct tty_ldisc *ld;
2282 
2283 	if ((current->signal->tty != tty) && !capable(CAP_SYS_ADMIN))
2284 		return -EPERM;
2285 	if (get_user(ch, p))
2286 		return -EFAULT;
2287 	tty_audit_tiocsti(tty, ch);
2288 	ld = tty_ldisc_ref_wait(tty);
2289 	if (!ld)
2290 		return -EIO;
2291 	tty_buffer_lock_exclusive(tty->port);
2292 	if (ld->ops->receive_buf)
2293 		ld->ops->receive_buf(tty, &ch, &mbz, 1);
2294 	tty_buffer_unlock_exclusive(tty->port);
2295 	tty_ldisc_deref(ld);
2296 	return 0;
2297 }
2298 
2299 /**
2300  * tiocgwinsz		-	implement window query ioctl
2301  * @tty: tty
2302  * @arg: user buffer for result
2303  *
2304  * Copies the kernel idea of the window size into the user buffer.
2305  *
2306  * Locking: @tty->winsize_mutex is taken to ensure the winsize data is
2307  * consistent.
2308  */
tiocgwinsz(struct tty_struct * tty,struct winsize __user * arg)2309 static int tiocgwinsz(struct tty_struct *tty, struct winsize __user *arg)
2310 {
2311 	int err;
2312 
2313 	mutex_lock(&tty->winsize_mutex);
2314 	err = copy_to_user(arg, &tty->winsize, sizeof(*arg));
2315 	mutex_unlock(&tty->winsize_mutex);
2316 
2317 	return err ? -EFAULT : 0;
2318 }
2319 
2320 /**
2321  * tty_do_resize	-	resize event
2322  * @tty: tty being resized
2323  * @ws: new dimensions
2324  *
2325  * Update the termios variables and send the necessary signals to peform a
2326  * terminal resize correctly.
2327  */
tty_do_resize(struct tty_struct * tty,struct winsize * ws)2328 int tty_do_resize(struct tty_struct *tty, struct winsize *ws)
2329 {
2330 	struct pid *pgrp;
2331 
2332 	/* Lock the tty */
2333 	mutex_lock(&tty->winsize_mutex);
2334 	if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
2335 		goto done;
2336 
2337 	/* Signal the foreground process group */
2338 	pgrp = tty_get_pgrp(tty);
2339 	if (pgrp)
2340 		kill_pgrp(pgrp, SIGWINCH, 1);
2341 	put_pid(pgrp);
2342 
2343 	tty->winsize = *ws;
2344 done:
2345 	mutex_unlock(&tty->winsize_mutex);
2346 	return 0;
2347 }
2348 EXPORT_SYMBOL(tty_do_resize);
2349 
2350 /**
2351  * tiocswinsz		-	implement window size set ioctl
2352  * @tty: tty side of tty
2353  * @arg: user buffer for result
2354  *
2355  * Copies the user idea of the window size to the kernel. Traditionally this is
2356  * just advisory information but for the Linux console it actually has driver
2357  * level meaning and triggers a VC resize.
2358  *
2359  * Locking:
2360  *	Driver dependent. The default do_resize method takes the tty termios
2361  *	mutex and ctrl.lock. The console takes its own lock then calls into the
2362  *	default method.
2363  */
tiocswinsz(struct tty_struct * tty,struct winsize __user * arg)2364 static int tiocswinsz(struct tty_struct *tty, struct winsize __user *arg)
2365 {
2366 	struct winsize tmp_ws;
2367 
2368 	if (copy_from_user(&tmp_ws, arg, sizeof(*arg)))
2369 		return -EFAULT;
2370 
2371 	if (tty->ops->resize)
2372 		return tty->ops->resize(tty, &tmp_ws);
2373 	else
2374 		return tty_do_resize(tty, &tmp_ws);
2375 }
2376 
2377 /**
2378  * tioccons	-	allow admin to move logical console
2379  * @file: the file to become console
2380  *
2381  * Allow the administrator to move the redirected console device.
2382  *
2383  * Locking: uses redirect_lock to guard the redirect information
2384  */
tioccons(struct file * file)2385 static int tioccons(struct file *file)
2386 {
2387 	if (!capable(CAP_SYS_ADMIN))
2388 		return -EPERM;
2389 	if (file->f_op->write_iter == redirected_tty_write) {
2390 		struct file *f;
2391 
2392 		spin_lock(&redirect_lock);
2393 		f = redirect;
2394 		redirect = NULL;
2395 		spin_unlock(&redirect_lock);
2396 		if (f)
2397 			fput(f);
2398 		return 0;
2399 	}
2400 	if (file->f_op->write_iter != tty_write)
2401 		return -ENOTTY;
2402 	if (!(file->f_mode & FMODE_WRITE))
2403 		return -EBADF;
2404 	if (!(file->f_mode & FMODE_CAN_WRITE))
2405 		return -EINVAL;
2406 	spin_lock(&redirect_lock);
2407 	if (redirect) {
2408 		spin_unlock(&redirect_lock);
2409 		return -EBUSY;
2410 	}
2411 	redirect = get_file(file);
2412 	spin_unlock(&redirect_lock);
2413 	return 0;
2414 }
2415 
2416 /**
2417  * tiocsetd	-	set line discipline
2418  * @tty: tty device
2419  * @p: pointer to user data
2420  *
2421  * Set the line discipline according to user request.
2422  *
2423  * Locking: see tty_set_ldisc(), this function is just a helper
2424  */
tiocsetd(struct tty_struct * tty,int __user * p)2425 static int tiocsetd(struct tty_struct *tty, int __user *p)
2426 {
2427 	int disc;
2428 	int ret;
2429 
2430 	if (get_user(disc, p))
2431 		return -EFAULT;
2432 
2433 	ret = tty_set_ldisc(tty, disc);
2434 
2435 	return ret;
2436 }
2437 
2438 /**
2439  * tiocgetd	-	get line discipline
2440  * @tty: tty device
2441  * @p: pointer to user data
2442  *
2443  * Retrieves the line discipline id directly from the ldisc.
2444  *
2445  * Locking: waits for ldisc reference (in case the line discipline is changing
2446  * or the @tty is being hungup)
2447  */
tiocgetd(struct tty_struct * tty,int __user * p)2448 static int tiocgetd(struct tty_struct *tty, int __user *p)
2449 {
2450 	struct tty_ldisc *ld;
2451 	int ret;
2452 
2453 	ld = tty_ldisc_ref_wait(tty);
2454 	if (!ld)
2455 		return -EIO;
2456 	ret = put_user(ld->ops->num, p);
2457 	tty_ldisc_deref(ld);
2458 	return ret;
2459 }
2460 
2461 /**
2462  * send_break	-	performed time break
2463  * @tty: device to break on
2464  * @duration: timeout in mS
2465  *
2466  * Perform a timed break on hardware that lacks its own driver level timed
2467  * break functionality.
2468  *
2469  * Locking:
2470  *	@tty->atomic_write_lock serializes
2471  */
send_break(struct tty_struct * tty,unsigned int duration)2472 static int send_break(struct tty_struct *tty, unsigned int duration)
2473 {
2474 	int retval;
2475 
2476 	if (tty->ops->break_ctl == NULL)
2477 		return 0;
2478 
2479 	if (tty->driver->flags & TTY_DRIVER_HARDWARE_BREAK)
2480 		retval = tty->ops->break_ctl(tty, duration);
2481 	else {
2482 		/* Do the work ourselves */
2483 		if (tty_write_lock(tty, 0) < 0)
2484 			return -EINTR;
2485 		retval = tty->ops->break_ctl(tty, -1);
2486 		if (retval)
2487 			goto out;
2488 		if (!signal_pending(current))
2489 			msleep_interruptible(duration);
2490 		retval = tty->ops->break_ctl(tty, 0);
2491 out:
2492 		tty_write_unlock(tty);
2493 		if (signal_pending(current))
2494 			retval = -EINTR;
2495 	}
2496 	return retval;
2497 }
2498 
2499 /**
2500  * tty_tiocmget		-	get modem status
2501  * @tty: tty device
2502  * @p: pointer to result
2503  *
2504  * Obtain the modem status bits from the tty driver if the feature is
2505  * supported. Return -%ENOTTY if it is not available.
2506  *
2507  * Locking: none (up to the driver)
2508  */
tty_tiocmget(struct tty_struct * tty,int __user * p)2509 static int tty_tiocmget(struct tty_struct *tty, int __user *p)
2510 {
2511 	int retval = -ENOTTY;
2512 
2513 	if (tty->ops->tiocmget) {
2514 		retval = tty->ops->tiocmget(tty);
2515 
2516 		if (retval >= 0)
2517 			retval = put_user(retval, p);
2518 	}
2519 	return retval;
2520 }
2521 
2522 /**
2523  * tty_tiocmset		-	set modem status
2524  * @tty: tty device
2525  * @cmd: command - clear bits, set bits or set all
2526  * @p: pointer to desired bits
2527  *
2528  * Set the modem status bits from the tty driver if the feature
2529  * is supported. Return -%ENOTTY if it is not available.
2530  *
2531  * Locking: none (up to the driver)
2532  */
tty_tiocmset(struct tty_struct * tty,unsigned int cmd,unsigned __user * p)2533 static int tty_tiocmset(struct tty_struct *tty, unsigned int cmd,
2534 	     unsigned __user *p)
2535 {
2536 	int retval;
2537 	unsigned int set, clear, val;
2538 
2539 	if (tty->ops->tiocmset == NULL)
2540 		return -ENOTTY;
2541 
2542 	retval = get_user(val, p);
2543 	if (retval)
2544 		return retval;
2545 	set = clear = 0;
2546 	switch (cmd) {
2547 	case TIOCMBIS:
2548 		set = val;
2549 		break;
2550 	case TIOCMBIC:
2551 		clear = val;
2552 		break;
2553 	case TIOCMSET:
2554 		set = val;
2555 		clear = ~val;
2556 		break;
2557 	}
2558 	set &= TIOCM_DTR|TIOCM_RTS|TIOCM_OUT1|TIOCM_OUT2|TIOCM_LOOP;
2559 	clear &= TIOCM_DTR|TIOCM_RTS|TIOCM_OUT1|TIOCM_OUT2|TIOCM_LOOP;
2560 	return tty->ops->tiocmset(tty, set, clear);
2561 }
2562 
2563 /**
2564  * tty_get_icount	-	get tty statistics
2565  * @tty: tty device
2566  * @icount: output parameter
2567  *
2568  * Gets a copy of the @tty's icount statistics.
2569  *
2570  * Locking: none (up to the driver)
2571  */
tty_get_icount(struct tty_struct * tty,struct serial_icounter_struct * icount)2572 int tty_get_icount(struct tty_struct *tty,
2573 		   struct serial_icounter_struct *icount)
2574 {
2575 	memset(icount, 0, sizeof(*icount));
2576 
2577 	if (tty->ops->get_icount)
2578 		return tty->ops->get_icount(tty, icount);
2579 	else
2580 		return -ENOTTY;
2581 }
2582 EXPORT_SYMBOL_GPL(tty_get_icount);
2583 
tty_tiocgicount(struct tty_struct * tty,void __user * arg)2584 static int tty_tiocgicount(struct tty_struct *tty, void __user *arg)
2585 {
2586 	struct serial_icounter_struct icount;
2587 	int retval;
2588 
2589 	retval = tty_get_icount(tty, &icount);
2590 	if (retval != 0)
2591 		return retval;
2592 
2593 	if (copy_to_user(arg, &icount, sizeof(icount)))
2594 		return -EFAULT;
2595 	return 0;
2596 }
2597 
tty_set_serial(struct tty_struct * tty,struct serial_struct * ss)2598 static int tty_set_serial(struct tty_struct *tty, struct serial_struct *ss)
2599 {
2600 	char comm[TASK_COMM_LEN];
2601 	int flags;
2602 
2603 	flags = ss->flags & ASYNC_DEPRECATED;
2604 
2605 	if (flags)
2606 		pr_warn_ratelimited("%s: '%s' is using deprecated serial flags (with no effect): %.8x\n",
2607 				__func__, get_task_comm(comm, current), flags);
2608 
2609 	if (!tty->ops->set_serial)
2610 		return -ENOTTY;
2611 
2612 	return tty->ops->set_serial(tty, ss);
2613 }
2614 
tty_tiocsserial(struct tty_struct * tty,struct serial_struct __user * ss)2615 static int tty_tiocsserial(struct tty_struct *tty, struct serial_struct __user *ss)
2616 {
2617 	struct serial_struct v;
2618 
2619 	if (copy_from_user(&v, ss, sizeof(*ss)))
2620 		return -EFAULT;
2621 
2622 	return tty_set_serial(tty, &v);
2623 }
2624 
tty_tiocgserial(struct tty_struct * tty,struct serial_struct __user * ss)2625 static int tty_tiocgserial(struct tty_struct *tty, struct serial_struct __user *ss)
2626 {
2627 	struct serial_struct v;
2628 	int err;
2629 
2630 	memset(&v, 0, sizeof(v));
2631 	if (!tty->ops->get_serial)
2632 		return -ENOTTY;
2633 	err = tty->ops->get_serial(tty, &v);
2634 	if (!err && copy_to_user(ss, &v, sizeof(v)))
2635 		err = -EFAULT;
2636 	return err;
2637 }
2638 
2639 /*
2640  * if pty, return the slave side (real_tty)
2641  * otherwise, return self
2642  */
tty_pair_get_tty(struct tty_struct * tty)2643 static struct tty_struct *tty_pair_get_tty(struct tty_struct *tty)
2644 {
2645 	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
2646 	    tty->driver->subtype == PTY_TYPE_MASTER)
2647 		tty = tty->link;
2648 	return tty;
2649 }
2650 
2651 /*
2652  * Split this up, as gcc can choke on it otherwise..
2653  */
tty_ioctl(struct file * file,unsigned int cmd,unsigned long arg)2654 long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
2655 {
2656 	struct tty_struct *tty = file_tty(file);
2657 	struct tty_struct *real_tty;
2658 	void __user *p = (void __user *)arg;
2659 	int retval;
2660 	struct tty_ldisc *ld;
2661 
2662 	if (tty_paranoia_check(tty, file_inode(file), "tty_ioctl"))
2663 		return -EINVAL;
2664 
2665 	real_tty = tty_pair_get_tty(tty);
2666 
2667 	/*
2668 	 * Factor out some common prep work
2669 	 */
2670 	switch (cmd) {
2671 	case TIOCSETD:
2672 	case TIOCSBRK:
2673 	case TIOCCBRK:
2674 	case TCSBRK:
2675 	case TCSBRKP:
2676 		retval = tty_check_change(tty);
2677 		if (retval)
2678 			return retval;
2679 		if (cmd != TIOCCBRK) {
2680 			tty_wait_until_sent(tty, 0);
2681 			if (signal_pending(current))
2682 				return -EINTR;
2683 		}
2684 		break;
2685 	}
2686 
2687 	/*
2688 	 *	Now do the stuff.
2689 	 */
2690 	switch (cmd) {
2691 	case TIOCSTI:
2692 		return tiocsti(tty, p);
2693 	case TIOCGWINSZ:
2694 		return tiocgwinsz(real_tty, p);
2695 	case TIOCSWINSZ:
2696 		return tiocswinsz(real_tty, p);
2697 	case TIOCCONS:
2698 		return real_tty != tty ? -EINVAL : tioccons(file);
2699 	case TIOCEXCL:
2700 		set_bit(TTY_EXCLUSIVE, &tty->flags);
2701 		return 0;
2702 	case TIOCNXCL:
2703 		clear_bit(TTY_EXCLUSIVE, &tty->flags);
2704 		return 0;
2705 	case TIOCGEXCL:
2706 	{
2707 		int excl = test_bit(TTY_EXCLUSIVE, &tty->flags);
2708 
2709 		return put_user(excl, (int __user *)p);
2710 	}
2711 	case TIOCGETD:
2712 		return tiocgetd(tty, p);
2713 	case TIOCSETD:
2714 		return tiocsetd(tty, p);
2715 	case TIOCVHANGUP:
2716 		if (!capable(CAP_SYS_ADMIN))
2717 			return -EPERM;
2718 		tty_vhangup(tty);
2719 		return 0;
2720 	case TIOCGDEV:
2721 	{
2722 		unsigned int ret = new_encode_dev(tty_devnum(real_tty));
2723 
2724 		return put_user(ret, (unsigned int __user *)p);
2725 	}
2726 	/*
2727 	 * Break handling
2728 	 */
2729 	case TIOCSBRK:	/* Turn break on, unconditionally */
2730 		if (tty->ops->break_ctl)
2731 			return tty->ops->break_ctl(tty, -1);
2732 		return 0;
2733 	case TIOCCBRK:	/* Turn break off, unconditionally */
2734 		if (tty->ops->break_ctl)
2735 			return tty->ops->break_ctl(tty, 0);
2736 		return 0;
2737 	case TCSBRK:   /* SVID version: non-zero arg --> no break */
2738 		/* non-zero arg means wait for all output data
2739 		 * to be sent (performed above) but don't send break.
2740 		 * This is used by the tcdrain() termios function.
2741 		 */
2742 		if (!arg)
2743 			return send_break(tty, 250);
2744 		return 0;
2745 	case TCSBRKP:	/* support for POSIX tcsendbreak() */
2746 		return send_break(tty, arg ? arg*100 : 250);
2747 
2748 	case TIOCMGET:
2749 		return tty_tiocmget(tty, p);
2750 	case TIOCMSET:
2751 	case TIOCMBIC:
2752 	case TIOCMBIS:
2753 		return tty_tiocmset(tty, cmd, p);
2754 	case TIOCGICOUNT:
2755 		return tty_tiocgicount(tty, p);
2756 	case TCFLSH:
2757 		switch (arg) {
2758 		case TCIFLUSH:
2759 		case TCIOFLUSH:
2760 		/* flush tty buffer and allow ldisc to process ioctl */
2761 			tty_buffer_flush(tty, NULL);
2762 			break;
2763 		}
2764 		break;
2765 	case TIOCSSERIAL:
2766 		return tty_tiocsserial(tty, p);
2767 	case TIOCGSERIAL:
2768 		return tty_tiocgserial(tty, p);
2769 	case TIOCGPTPEER:
2770 		/* Special because the struct file is needed */
2771 		return ptm_open_peer(file, tty, (int)arg);
2772 	default:
2773 		retval = tty_jobctrl_ioctl(tty, real_tty, file, cmd, arg);
2774 		if (retval != -ENOIOCTLCMD)
2775 			return retval;
2776 	}
2777 	if (tty->ops->ioctl) {
2778 		retval = tty->ops->ioctl(tty, cmd, arg);
2779 		if (retval != -ENOIOCTLCMD)
2780 			return retval;
2781 	}
2782 	ld = tty_ldisc_ref_wait(tty);
2783 	if (!ld)
2784 		return hung_up_tty_ioctl(file, cmd, arg);
2785 	retval = -EINVAL;
2786 	if (ld->ops->ioctl) {
2787 		retval = ld->ops->ioctl(tty, cmd, arg);
2788 		if (retval == -ENOIOCTLCMD)
2789 			retval = -ENOTTY;
2790 	}
2791 	tty_ldisc_deref(ld);
2792 	return retval;
2793 }
2794 
2795 #ifdef CONFIG_COMPAT
2796 
2797 struct serial_struct32 {
2798 	compat_int_t    type;
2799 	compat_int_t    line;
2800 	compat_uint_t   port;
2801 	compat_int_t    irq;
2802 	compat_int_t    flags;
2803 	compat_int_t    xmit_fifo_size;
2804 	compat_int_t    custom_divisor;
2805 	compat_int_t    baud_base;
2806 	unsigned short  close_delay;
2807 	char    io_type;
2808 	char    reserved_char;
2809 	compat_int_t    hub6;
2810 	unsigned short  closing_wait; /* time to wait before closing */
2811 	unsigned short  closing_wait2; /* no longer used... */
2812 	compat_uint_t   iomem_base;
2813 	unsigned short  iomem_reg_shift;
2814 	unsigned int    port_high;
2815 	/* compat_ulong_t  iomap_base FIXME */
2816 	compat_int_t    reserved;
2817 };
2818 
compat_tty_tiocsserial(struct tty_struct * tty,struct serial_struct32 __user * ss)2819 static int compat_tty_tiocsserial(struct tty_struct *tty,
2820 		struct serial_struct32 __user *ss)
2821 {
2822 	struct serial_struct32 v32;
2823 	struct serial_struct v;
2824 
2825 	if (copy_from_user(&v32, ss, sizeof(*ss)))
2826 		return -EFAULT;
2827 
2828 	memcpy(&v, &v32, offsetof(struct serial_struct32, iomem_base));
2829 	v.iomem_base = compat_ptr(v32.iomem_base);
2830 	v.iomem_reg_shift = v32.iomem_reg_shift;
2831 	v.port_high = v32.port_high;
2832 	v.iomap_base = 0;
2833 
2834 	return tty_set_serial(tty, &v);
2835 }
2836 
compat_tty_tiocgserial(struct tty_struct * tty,struct serial_struct32 __user * ss)2837 static int compat_tty_tiocgserial(struct tty_struct *tty,
2838 			struct serial_struct32 __user *ss)
2839 {
2840 	struct serial_struct32 v32;
2841 	struct serial_struct v;
2842 	int err;
2843 
2844 	memset(&v, 0, sizeof(v));
2845 	memset(&v32, 0, sizeof(v32));
2846 
2847 	if (!tty->ops->get_serial)
2848 		return -ENOTTY;
2849 	err = tty->ops->get_serial(tty, &v);
2850 	if (!err) {
2851 		memcpy(&v32, &v, offsetof(struct serial_struct32, iomem_base));
2852 		v32.iomem_base = (unsigned long)v.iomem_base >> 32 ?
2853 			0xfffffff : ptr_to_compat(v.iomem_base);
2854 		v32.iomem_reg_shift = v.iomem_reg_shift;
2855 		v32.port_high = v.port_high;
2856 		if (copy_to_user(ss, &v32, sizeof(v32)))
2857 			err = -EFAULT;
2858 	}
2859 	return err;
2860 }
tty_compat_ioctl(struct file * file,unsigned int cmd,unsigned long arg)2861 static long tty_compat_ioctl(struct file *file, unsigned int cmd,
2862 				unsigned long arg)
2863 {
2864 	struct tty_struct *tty = file_tty(file);
2865 	struct tty_ldisc *ld;
2866 	int retval = -ENOIOCTLCMD;
2867 
2868 	switch (cmd) {
2869 	case TIOCOUTQ:
2870 	case TIOCSTI:
2871 	case TIOCGWINSZ:
2872 	case TIOCSWINSZ:
2873 	case TIOCGEXCL:
2874 	case TIOCGETD:
2875 	case TIOCSETD:
2876 	case TIOCGDEV:
2877 	case TIOCMGET:
2878 	case TIOCMSET:
2879 	case TIOCMBIC:
2880 	case TIOCMBIS:
2881 	case TIOCGICOUNT:
2882 	case TIOCGPGRP:
2883 	case TIOCSPGRP:
2884 	case TIOCGSID:
2885 	case TIOCSERGETLSR:
2886 	case TIOCGRS485:
2887 	case TIOCSRS485:
2888 #ifdef TIOCGETP
2889 	case TIOCGETP:
2890 	case TIOCSETP:
2891 	case TIOCSETN:
2892 #endif
2893 #ifdef TIOCGETC
2894 	case TIOCGETC:
2895 	case TIOCSETC:
2896 #endif
2897 #ifdef TIOCGLTC
2898 	case TIOCGLTC:
2899 	case TIOCSLTC:
2900 #endif
2901 	case TCSETSF:
2902 	case TCSETSW:
2903 	case TCSETS:
2904 	case TCGETS:
2905 #ifdef TCGETS2
2906 	case TCGETS2:
2907 	case TCSETSF2:
2908 	case TCSETSW2:
2909 	case TCSETS2:
2910 #endif
2911 	case TCGETA:
2912 	case TCSETAF:
2913 	case TCSETAW:
2914 	case TCSETA:
2915 	case TIOCGLCKTRMIOS:
2916 	case TIOCSLCKTRMIOS:
2917 #ifdef TCGETX
2918 	case TCGETX:
2919 	case TCSETX:
2920 	case TCSETXW:
2921 	case TCSETXF:
2922 #endif
2923 	case TIOCGSOFTCAR:
2924 	case TIOCSSOFTCAR:
2925 
2926 	case PPPIOCGCHAN:
2927 	case PPPIOCGUNIT:
2928 		return tty_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
2929 	case TIOCCONS:
2930 	case TIOCEXCL:
2931 	case TIOCNXCL:
2932 	case TIOCVHANGUP:
2933 	case TIOCSBRK:
2934 	case TIOCCBRK:
2935 	case TCSBRK:
2936 	case TCSBRKP:
2937 	case TCFLSH:
2938 	case TIOCGPTPEER:
2939 	case TIOCNOTTY:
2940 	case TIOCSCTTY:
2941 	case TCXONC:
2942 	case TIOCMIWAIT:
2943 	case TIOCSERCONFIG:
2944 		return tty_ioctl(file, cmd, arg);
2945 	}
2946 
2947 	if (tty_paranoia_check(tty, file_inode(file), "tty_ioctl"))
2948 		return -EINVAL;
2949 
2950 	switch (cmd) {
2951 	case TIOCSSERIAL:
2952 		return compat_tty_tiocsserial(tty, compat_ptr(arg));
2953 	case TIOCGSERIAL:
2954 		return compat_tty_tiocgserial(tty, compat_ptr(arg));
2955 	}
2956 	if (tty->ops->compat_ioctl) {
2957 		retval = tty->ops->compat_ioctl(tty, cmd, arg);
2958 		if (retval != -ENOIOCTLCMD)
2959 			return retval;
2960 	}
2961 
2962 	ld = tty_ldisc_ref_wait(tty);
2963 	if (!ld)
2964 		return hung_up_tty_compat_ioctl(file, cmd, arg);
2965 	if (ld->ops->compat_ioctl)
2966 		retval = ld->ops->compat_ioctl(tty, cmd, arg);
2967 	if (retval == -ENOIOCTLCMD && ld->ops->ioctl)
2968 		retval = ld->ops->ioctl(tty, (unsigned long)compat_ptr(cmd),
2969 				arg);
2970 	tty_ldisc_deref(ld);
2971 
2972 	return retval;
2973 }
2974 #endif
2975 
this_tty(const void * t,struct file * file,unsigned fd)2976 static int this_tty(const void *t, struct file *file, unsigned fd)
2977 {
2978 	if (likely(file->f_op->read_iter != tty_read))
2979 		return 0;
2980 	return file_tty(file) != t ? 0 : fd + 1;
2981 }
2982 
2983 /*
2984  * This implements the "Secure Attention Key" ---  the idea is to
2985  * prevent trojan horses by killing all processes associated with this
2986  * tty when the user hits the "Secure Attention Key".  Required for
2987  * super-paranoid applications --- see the Orange Book for more details.
2988  *
2989  * This code could be nicer; ideally it should send a HUP, wait a few
2990  * seconds, then send a INT, and then a KILL signal.  But you then
2991  * have to coordinate with the init process, since all processes associated
2992  * with the current tty must be dead before the new getty is allowed
2993  * to spawn.
2994  *
2995  * Now, if it would be correct ;-/ The current code has a nasty hole -
2996  * it doesn't catch files in flight. We may send the descriptor to ourselves
2997  * via AF_UNIX socket, close it and later fetch from socket. FIXME.
2998  *
2999  * Nasty bug: do_SAK is being called in interrupt context.  This can
3000  * deadlock.  We punt it up to process context.  AKPM - 16Mar2001
3001  */
__do_SAK(struct tty_struct * tty)3002 void __do_SAK(struct tty_struct *tty)
3003 {
3004 	struct task_struct *g, *p;
3005 	struct pid *session;
3006 	int i;
3007 	unsigned long flags;
3008 
3009 	spin_lock_irqsave(&tty->ctrl.lock, flags);
3010 	session = get_pid(tty->ctrl.session);
3011 	spin_unlock_irqrestore(&tty->ctrl.lock, flags);
3012 
3013 	tty_ldisc_flush(tty);
3014 
3015 	tty_driver_flush_buffer(tty);
3016 
3017 	read_lock(&tasklist_lock);
3018 	/* Kill the entire session */
3019 	do_each_pid_task(session, PIDTYPE_SID, p) {
3020 		tty_notice(tty, "SAK: killed process %d (%s): by session\n",
3021 			   task_pid_nr(p), p->comm);
3022 		group_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_SID);
3023 	} while_each_pid_task(session, PIDTYPE_SID, p);
3024 
3025 	/* Now kill any processes that happen to have the tty open */
3026 	do_each_thread(g, p) {
3027 		if (p->signal->tty == tty) {
3028 			tty_notice(tty, "SAK: killed process %d (%s): by controlling tty\n",
3029 				   task_pid_nr(p), p->comm);
3030 			group_send_sig_info(SIGKILL, SEND_SIG_PRIV, p,
3031 					PIDTYPE_SID);
3032 			continue;
3033 		}
3034 		task_lock(p);
3035 		i = iterate_fd(p->files, 0, this_tty, tty);
3036 		if (i != 0) {
3037 			tty_notice(tty, "SAK: killed process %d (%s): by fd#%d\n",
3038 				   task_pid_nr(p), p->comm, i - 1);
3039 			group_send_sig_info(SIGKILL, SEND_SIG_PRIV, p,
3040 					PIDTYPE_SID);
3041 		}
3042 		task_unlock(p);
3043 	} while_each_thread(g, p);
3044 	read_unlock(&tasklist_lock);
3045 	put_pid(session);
3046 }
3047 
do_SAK_work(struct work_struct * work)3048 static void do_SAK_work(struct work_struct *work)
3049 {
3050 	struct tty_struct *tty =
3051 		container_of(work, struct tty_struct, SAK_work);
3052 	__do_SAK(tty);
3053 }
3054 
3055 /*
3056  * The tq handling here is a little racy - tty->SAK_work may already be queued.
3057  * Fortunately we don't need to worry, because if ->SAK_work is already queued,
3058  * the values which we write to it will be identical to the values which it
3059  * already has. --akpm
3060  */
do_SAK(struct tty_struct * tty)3061 void do_SAK(struct tty_struct *tty)
3062 {
3063 	if (!tty)
3064 		return;
3065 	schedule_work(&tty->SAK_work);
3066 }
3067 EXPORT_SYMBOL(do_SAK);
3068 
3069 /* Must put_device() after it's unused! */
tty_get_device(struct tty_struct * tty)3070 static struct device *tty_get_device(struct tty_struct *tty)
3071 {
3072 	dev_t devt = tty_devnum(tty);
3073 
3074 	return class_find_device_by_devt(tty_class, devt);
3075 }
3076 
3077 
3078 /**
3079  * alloc_tty_struct - allocate a new tty
3080  * @driver: driver which will handle the returned tty
3081  * @idx: minor of the tty
3082  *
3083  * This subroutine allocates and initializes a tty structure.
3084  *
3085  * Locking: none - @tty in question is not exposed at this point
3086  */
alloc_tty_struct(struct tty_driver * driver,int idx)3087 struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx)
3088 {
3089 	struct tty_struct *tty;
3090 
3091 	tty = kzalloc(sizeof(*tty), GFP_KERNEL_ACCOUNT);
3092 	if (!tty)
3093 		return NULL;
3094 
3095 	kref_init(&tty->kref);
3096 	tty->magic = TTY_MAGIC;
3097 	if (tty_ldisc_init(tty)) {
3098 		kfree(tty);
3099 		return NULL;
3100 	}
3101 	tty->ctrl.session = NULL;
3102 	tty->ctrl.pgrp = NULL;
3103 	mutex_init(&tty->legacy_mutex);
3104 	mutex_init(&tty->throttle_mutex);
3105 	init_rwsem(&tty->termios_rwsem);
3106 	mutex_init(&tty->winsize_mutex);
3107 	init_ldsem(&tty->ldisc_sem);
3108 	init_waitqueue_head(&tty->write_wait);
3109 	init_waitqueue_head(&tty->read_wait);
3110 	INIT_WORK(&tty->hangup_work, do_tty_hangup);
3111 	mutex_init(&tty->atomic_write_lock);
3112 	spin_lock_init(&tty->ctrl.lock);
3113 	spin_lock_init(&tty->flow.lock);
3114 	spin_lock_init(&tty->files_lock);
3115 	INIT_LIST_HEAD(&tty->tty_files);
3116 	INIT_WORK(&tty->SAK_work, do_SAK_work);
3117 
3118 	tty->driver = driver;
3119 	tty->ops = driver->ops;
3120 	tty->index = idx;
3121 	tty_line_name(driver, idx, tty->name);
3122 	tty->dev = tty_get_device(tty);
3123 
3124 	return tty;
3125 }
3126 
3127 /**
3128  * tty_put_char	- write one character to a tty
3129  * @tty: tty
3130  * @ch: character to write
3131  *
3132  * Write one byte to the @tty using the provided @tty->ops->put_char() method
3133  * if present.
3134  *
3135  * Note: the specific put_char operation in the driver layer may go
3136  * away soon. Don't call it directly, use this method
3137  *
3138  * Return: the number of characters successfully output.
3139  */
tty_put_char(struct tty_struct * tty,unsigned char ch)3140 int tty_put_char(struct tty_struct *tty, unsigned char ch)
3141 {
3142 	if (tty->ops->put_char)
3143 		return tty->ops->put_char(tty, ch);
3144 	return tty->ops->write(tty, &ch, 1);
3145 }
3146 EXPORT_SYMBOL_GPL(tty_put_char);
3147 
3148 struct class *tty_class;
3149 
tty_cdev_add(struct tty_driver * driver,dev_t dev,unsigned int index,unsigned int count)3150 static int tty_cdev_add(struct tty_driver *driver, dev_t dev,
3151 		unsigned int index, unsigned int count)
3152 {
3153 	int err;
3154 
3155 	/* init here, since reused cdevs cause crashes */
3156 	driver->cdevs[index] = cdev_alloc();
3157 	if (!driver->cdevs[index])
3158 		return -ENOMEM;
3159 	driver->cdevs[index]->ops = &tty_fops;
3160 	driver->cdevs[index]->owner = driver->owner;
3161 	err = cdev_add(driver->cdevs[index], dev, count);
3162 	if (err)
3163 		kobject_put(&driver->cdevs[index]->kobj);
3164 	return err;
3165 }
3166 
3167 /**
3168  * tty_register_device - register a tty device
3169  * @driver: the tty driver that describes the tty device
3170  * @index: the index in the tty driver for this tty device
3171  * @device: a struct device that is associated with this tty device.
3172  *	This field is optional, if there is no known struct device
3173  *	for this tty device it can be set to NULL safely.
3174  *
3175  * This call is required to be made to register an individual tty device
3176  * if the tty driver's flags have the %TTY_DRIVER_DYNAMIC_DEV bit set.  If
3177  * that bit is not set, this function should not be called by a tty
3178  * driver.
3179  *
3180  * Locking: ??
3181  *
3182  * Return: A pointer to the struct device for this tty device (or
3183  * ERR_PTR(-EFOO) on error).
3184  */
tty_register_device(struct tty_driver * driver,unsigned index,struct device * device)3185 struct device *tty_register_device(struct tty_driver *driver, unsigned index,
3186 				   struct device *device)
3187 {
3188 	return tty_register_device_attr(driver, index, device, NULL, NULL);
3189 }
3190 EXPORT_SYMBOL(tty_register_device);
3191 
tty_device_create_release(struct device * dev)3192 static void tty_device_create_release(struct device *dev)
3193 {
3194 	dev_dbg(dev, "releasing...\n");
3195 	kfree(dev);
3196 }
3197 
3198 /**
3199  * tty_register_device_attr - register a tty device
3200  * @driver: the tty driver that describes the tty device
3201  * @index: the index in the tty driver for this tty device
3202  * @device: a struct device that is associated with this tty device.
3203  *	This field is optional, if there is no known struct device
3204  *	for this tty device it can be set to %NULL safely.
3205  * @drvdata: Driver data to be set to device.
3206  * @attr_grp: Attribute group to be set on device.
3207  *
3208  * This call is required to be made to register an individual tty device if the
3209  * tty driver's flags have the %TTY_DRIVER_DYNAMIC_DEV bit set. If that bit is
3210  * not set, this function should not be called by a tty driver.
3211  *
3212  * Locking: ??
3213  *
3214  * Return: A pointer to the struct device for this tty device (or
3215  * ERR_PTR(-EFOO) on error).
3216  */
tty_register_device_attr(struct tty_driver * driver,unsigned index,struct device * device,void * drvdata,const struct attribute_group ** attr_grp)3217 struct device *tty_register_device_attr(struct tty_driver *driver,
3218 				   unsigned index, struct device *device,
3219 				   void *drvdata,
3220 				   const struct attribute_group **attr_grp)
3221 {
3222 	char name[64];
3223 	dev_t devt = MKDEV(driver->major, driver->minor_start) + index;
3224 	struct ktermios *tp;
3225 	struct device *dev;
3226 	int retval;
3227 
3228 	if (index >= driver->num) {
3229 		pr_err("%s: Attempt to register invalid tty line number (%d)\n",
3230 		       driver->name, index);
3231 		return ERR_PTR(-EINVAL);
3232 	}
3233 
3234 	if (driver->type == TTY_DRIVER_TYPE_PTY)
3235 		pty_line_name(driver, index, name);
3236 	else
3237 		tty_line_name(driver, index, name);
3238 
3239 	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
3240 	if (!dev)
3241 		return ERR_PTR(-ENOMEM);
3242 
3243 	dev->devt = devt;
3244 	dev->class = tty_class;
3245 	dev->parent = device;
3246 	dev->release = tty_device_create_release;
3247 	dev_set_name(dev, "%s", name);
3248 	dev->groups = attr_grp;
3249 	dev_set_drvdata(dev, drvdata);
3250 
3251 	dev_set_uevent_suppress(dev, 1);
3252 
3253 	retval = device_register(dev);
3254 	if (retval)
3255 		goto err_put;
3256 
3257 	if (!(driver->flags & TTY_DRIVER_DYNAMIC_ALLOC)) {
3258 		/*
3259 		 * Free any saved termios data so that the termios state is
3260 		 * reset when reusing a minor number.
3261 		 */
3262 		tp = driver->termios[index];
3263 		if (tp) {
3264 			driver->termios[index] = NULL;
3265 			kfree(tp);
3266 		}
3267 
3268 		retval = tty_cdev_add(driver, devt, index, 1);
3269 		if (retval)
3270 			goto err_del;
3271 	}
3272 
3273 	dev_set_uevent_suppress(dev, 0);
3274 	kobject_uevent(&dev->kobj, KOBJ_ADD);
3275 
3276 	return dev;
3277 
3278 err_del:
3279 	device_del(dev);
3280 err_put:
3281 	put_device(dev);
3282 
3283 	return ERR_PTR(retval);
3284 }
3285 EXPORT_SYMBOL_GPL(tty_register_device_attr);
3286 
3287 /**
3288  * tty_unregister_device - unregister a tty device
3289  * @driver: the tty driver that describes the tty device
3290  * @index: the index in the tty driver for this tty device
3291  *
3292  * If a tty device is registered with a call to tty_register_device() then
3293  * this function must be called when the tty device is gone.
3294  *
3295  * Locking: ??
3296  */
tty_unregister_device(struct tty_driver * driver,unsigned index)3297 void tty_unregister_device(struct tty_driver *driver, unsigned index)
3298 {
3299 	device_destroy(tty_class,
3300 		MKDEV(driver->major, driver->minor_start) + index);
3301 	if (!(driver->flags & TTY_DRIVER_DYNAMIC_ALLOC)) {
3302 		cdev_del(driver->cdevs[index]);
3303 		driver->cdevs[index] = NULL;
3304 	}
3305 }
3306 EXPORT_SYMBOL(tty_unregister_device);
3307 
3308 /**
3309  * __tty_alloc_driver -- allocate tty driver
3310  * @lines: count of lines this driver can handle at most
3311  * @owner: module which is responsible for this driver
3312  * @flags: some of %TTY_DRIVER_ flags, will be set in driver->flags
3313  *
3314  * This should not be called directly, some of the provided macros should be
3315  * used instead. Use IS_ERR() and friends on @retval.
3316  */
__tty_alloc_driver(unsigned int lines,struct module * owner,unsigned long flags)3317 struct tty_driver *__tty_alloc_driver(unsigned int lines, struct module *owner,
3318 		unsigned long flags)
3319 {
3320 	struct tty_driver *driver;
3321 	unsigned int cdevs = 1;
3322 	int err;
3323 
3324 	if (!lines || (flags & TTY_DRIVER_UNNUMBERED_NODE && lines > 1))
3325 		return ERR_PTR(-EINVAL);
3326 
3327 	driver = kzalloc(sizeof(*driver), GFP_KERNEL);
3328 	if (!driver)
3329 		return ERR_PTR(-ENOMEM);
3330 
3331 	kref_init(&driver->kref);
3332 	driver->magic = TTY_DRIVER_MAGIC;
3333 	driver->num = lines;
3334 	driver->owner = owner;
3335 	driver->flags = flags;
3336 
3337 	if (!(flags & TTY_DRIVER_DEVPTS_MEM)) {
3338 		driver->ttys = kcalloc(lines, sizeof(*driver->ttys),
3339 				GFP_KERNEL);
3340 		driver->termios = kcalloc(lines, sizeof(*driver->termios),
3341 				GFP_KERNEL);
3342 		if (!driver->ttys || !driver->termios) {
3343 			err = -ENOMEM;
3344 			goto err_free_all;
3345 		}
3346 	}
3347 
3348 	if (!(flags & TTY_DRIVER_DYNAMIC_ALLOC)) {
3349 		driver->ports = kcalloc(lines, sizeof(*driver->ports),
3350 				GFP_KERNEL);
3351 		if (!driver->ports) {
3352 			err = -ENOMEM;
3353 			goto err_free_all;
3354 		}
3355 		cdevs = lines;
3356 	}
3357 
3358 	driver->cdevs = kcalloc(cdevs, sizeof(*driver->cdevs), GFP_KERNEL);
3359 	if (!driver->cdevs) {
3360 		err = -ENOMEM;
3361 		goto err_free_all;
3362 	}
3363 
3364 	return driver;
3365 err_free_all:
3366 	kfree(driver->ports);
3367 	kfree(driver->ttys);
3368 	kfree(driver->termios);
3369 	kfree(driver->cdevs);
3370 	kfree(driver);
3371 	return ERR_PTR(err);
3372 }
3373 EXPORT_SYMBOL(__tty_alloc_driver);
3374 
destruct_tty_driver(struct kref * kref)3375 static void destruct_tty_driver(struct kref *kref)
3376 {
3377 	struct tty_driver *driver = container_of(kref, struct tty_driver, kref);
3378 	int i;
3379 	struct ktermios *tp;
3380 
3381 	if (driver->flags & TTY_DRIVER_INSTALLED) {
3382 		for (i = 0; i < driver->num; i++) {
3383 			tp = driver->termios[i];
3384 			if (tp) {
3385 				driver->termios[i] = NULL;
3386 				kfree(tp);
3387 			}
3388 			if (!(driver->flags & TTY_DRIVER_DYNAMIC_DEV))
3389 				tty_unregister_device(driver, i);
3390 		}
3391 		proc_tty_unregister_driver(driver);
3392 		if (driver->flags & TTY_DRIVER_DYNAMIC_ALLOC)
3393 			cdev_del(driver->cdevs[0]);
3394 	}
3395 	kfree(driver->cdevs);
3396 	kfree(driver->ports);
3397 	kfree(driver->termios);
3398 	kfree(driver->ttys);
3399 	kfree(driver);
3400 }
3401 
3402 /**
3403  * tty_driver_kref_put -- drop a reference to a tty driver
3404  * @driver: driver of which to drop the reference
3405  *
3406  * The final put will destroy and free up the driver.
3407  */
tty_driver_kref_put(struct tty_driver * driver)3408 void tty_driver_kref_put(struct tty_driver *driver)
3409 {
3410 	kref_put(&driver->kref, destruct_tty_driver);
3411 }
3412 EXPORT_SYMBOL(tty_driver_kref_put);
3413 
3414 /**
3415  * tty_register_driver -- register a tty driver
3416  * @driver: driver to register
3417  *
3418  * Called by a tty driver to register itself.
3419  */
tty_register_driver(struct tty_driver * driver)3420 int tty_register_driver(struct tty_driver *driver)
3421 {
3422 	int error;
3423 	int i;
3424 	dev_t dev;
3425 	struct device *d;
3426 
3427 	if (!driver->major) {
3428 		error = alloc_chrdev_region(&dev, driver->minor_start,
3429 						driver->num, driver->name);
3430 		if (!error) {
3431 			driver->major = MAJOR(dev);
3432 			driver->minor_start = MINOR(dev);
3433 		}
3434 	} else {
3435 		dev = MKDEV(driver->major, driver->minor_start);
3436 		error = register_chrdev_region(dev, driver->num, driver->name);
3437 	}
3438 	if (error < 0)
3439 		goto err;
3440 
3441 	if (driver->flags & TTY_DRIVER_DYNAMIC_ALLOC) {
3442 		error = tty_cdev_add(driver, dev, 0, driver->num);
3443 		if (error)
3444 			goto err_unreg_char;
3445 	}
3446 
3447 	mutex_lock(&tty_mutex);
3448 	list_add(&driver->tty_drivers, &tty_drivers);
3449 	mutex_unlock(&tty_mutex);
3450 
3451 	if (!(driver->flags & TTY_DRIVER_DYNAMIC_DEV)) {
3452 		for (i = 0; i < driver->num; i++) {
3453 			d = tty_register_device(driver, i, NULL);
3454 			if (IS_ERR(d)) {
3455 				error = PTR_ERR(d);
3456 				goto err_unreg_devs;
3457 			}
3458 		}
3459 	}
3460 	proc_tty_register_driver(driver);
3461 	driver->flags |= TTY_DRIVER_INSTALLED;
3462 	return 0;
3463 
3464 err_unreg_devs:
3465 	for (i--; i >= 0; i--)
3466 		tty_unregister_device(driver, i);
3467 
3468 	mutex_lock(&tty_mutex);
3469 	list_del(&driver->tty_drivers);
3470 	mutex_unlock(&tty_mutex);
3471 
3472 err_unreg_char:
3473 	unregister_chrdev_region(dev, driver->num);
3474 err:
3475 	return error;
3476 }
3477 EXPORT_SYMBOL(tty_register_driver);
3478 
3479 /**
3480  * tty_unregister_driver -- unregister a tty driver
3481  * @driver: driver to unregister
3482  *
3483  * Called by a tty driver to unregister itself.
3484  */
tty_unregister_driver(struct tty_driver * driver)3485 void tty_unregister_driver(struct tty_driver *driver)
3486 {
3487 	unregister_chrdev_region(MKDEV(driver->major, driver->minor_start),
3488 				driver->num);
3489 	mutex_lock(&tty_mutex);
3490 	list_del(&driver->tty_drivers);
3491 	mutex_unlock(&tty_mutex);
3492 }
3493 EXPORT_SYMBOL(tty_unregister_driver);
3494 
tty_devnum(struct tty_struct * tty)3495 dev_t tty_devnum(struct tty_struct *tty)
3496 {
3497 	return MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;
3498 }
3499 EXPORT_SYMBOL(tty_devnum);
3500 
tty_default_fops(struct file_operations * fops)3501 void tty_default_fops(struct file_operations *fops)
3502 {
3503 	*fops = tty_fops;
3504 }
3505 
tty_devnode(struct device * dev,umode_t * mode)3506 static char *tty_devnode(struct device *dev, umode_t *mode)
3507 {
3508 	if (!mode)
3509 		return NULL;
3510 	if (dev->devt == MKDEV(TTYAUX_MAJOR, 0) ||
3511 	    dev->devt == MKDEV(TTYAUX_MAJOR, 2))
3512 		*mode = 0666;
3513 	return NULL;
3514 }
3515 
tty_class_init(void)3516 static int __init tty_class_init(void)
3517 {
3518 	tty_class = class_create(THIS_MODULE, "tty");
3519 	if (IS_ERR(tty_class))
3520 		return PTR_ERR(tty_class);
3521 	tty_class->devnode = tty_devnode;
3522 	return 0;
3523 }
3524 
3525 postcore_initcall(tty_class_init);
3526 
3527 /* 3/2004 jmc: why do these devices exist? */
3528 static struct cdev tty_cdev, console_cdev;
3529 
show_cons_active(struct device * dev,struct device_attribute * attr,char * buf)3530 static ssize_t show_cons_active(struct device *dev,
3531 				struct device_attribute *attr, char *buf)
3532 {
3533 	struct console *cs[16];
3534 	int i = 0;
3535 	struct console *c;
3536 	ssize_t count = 0;
3537 
3538 	console_lock();
3539 	for_each_console(c) {
3540 		if (!c->device)
3541 			continue;
3542 		if (!c->write)
3543 			continue;
3544 		if ((c->flags & CON_ENABLED) == 0)
3545 			continue;
3546 		cs[i++] = c;
3547 		if (i >= ARRAY_SIZE(cs))
3548 			break;
3549 	}
3550 	while (i--) {
3551 		int index = cs[i]->index;
3552 		struct tty_driver *drv = cs[i]->device(cs[i], &index);
3553 
3554 		/* don't resolve tty0 as some programs depend on it */
3555 		if (drv && (cs[i]->index > 0 || drv->major != TTY_MAJOR))
3556 			count += tty_line_name(drv, index, buf + count);
3557 		else
3558 			count += sprintf(buf + count, "%s%d",
3559 					 cs[i]->name, cs[i]->index);
3560 
3561 		count += sprintf(buf + count, "%c", i ? ' ':'\n');
3562 	}
3563 	console_unlock();
3564 
3565 	return count;
3566 }
3567 static DEVICE_ATTR(active, S_IRUGO, show_cons_active, NULL);
3568 
3569 static struct attribute *cons_dev_attrs[] = {
3570 	&dev_attr_active.attr,
3571 	NULL
3572 };
3573 
3574 ATTRIBUTE_GROUPS(cons_dev);
3575 
3576 static struct device *consdev;
3577 
console_sysfs_notify(void)3578 void console_sysfs_notify(void)
3579 {
3580 	if (consdev)
3581 		sysfs_notify(&consdev->kobj, NULL, "active");
3582 }
3583 
3584 /*
3585  * Ok, now we can initialize the rest of the tty devices and can count
3586  * on memory allocations, interrupts etc..
3587  */
tty_init(void)3588 int __init tty_init(void)
3589 {
3590 	tty_sysctl_init();
3591 	cdev_init(&tty_cdev, &tty_fops);
3592 	if (cdev_add(&tty_cdev, MKDEV(TTYAUX_MAJOR, 0), 1) ||
3593 	    register_chrdev_region(MKDEV(TTYAUX_MAJOR, 0), 1, "/dev/tty") < 0)
3594 		panic("Couldn't register /dev/tty driver\n");
3595 	device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 0), NULL, "tty");
3596 
3597 	cdev_init(&console_cdev, &console_fops);
3598 	if (cdev_add(&console_cdev, MKDEV(TTYAUX_MAJOR, 1), 1) ||
3599 	    register_chrdev_region(MKDEV(TTYAUX_MAJOR, 1), 1, "/dev/console") < 0)
3600 		panic("Couldn't register /dev/console driver\n");
3601 	consdev = device_create_with_groups(tty_class, NULL,
3602 					    MKDEV(TTYAUX_MAJOR, 1), NULL,
3603 					    cons_dev_groups, "console");
3604 	if (IS_ERR(consdev))
3605 		consdev = NULL;
3606 
3607 #ifdef CONFIG_VT
3608 	vty_init(&console_fops);
3609 #endif
3610 	return 0;
3611 }
3612 
3613