summaryrefslogtreecommitdiff
path: root/drivers/tty/tty_ioctl.c
blob: 85de90eebc7bbf533e82df6a4ca3d83d0083afe6 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
// SPDX-License-Identifier: GPL-2.0
/*
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *
 * Modified by Fred N. van Kempen, 01/29/93, to add line disciplines
 * which can be dynamically activated and de-activated by the line
 * discipline handling modules (like SLIP).
 */

#include <linux/bits.h>
#include <linux/types.h>
#include <linux/termios.h>
#include <linux/errno.h>
#include <linux/sched/signal.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/tty.h>
#include <linux/fcntl.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/bitops.h>
#include <linux/mutex.h>
#include <linux/compat.h>
#include <linux/termios_internal.h>
#include "tty.h"

#include <asm/io.h>
#include <linux/uaccess.h>

#undef	DEBUG

/*
 * Internal flag options for termios setting behavior
 */
#define TERMIOS_FLUSH	BIT(0)
#define TERMIOS_WAIT	BIT(1)
#define TERMIOS_TERMIO	BIT(2)
#define TERMIOS_OLD	BIT(3)

/**
 * tty_chars_in_buffer - characters pending
 * @tty: terminal
 *
 * Returns: the number of bytes of data in the device private output queue. If
 * no private method is supplied there is assumed to be no queue on the device.
 */
unsigned int tty_chars_in_buffer(struct tty_struct *tty)
{
	if (tty->ops->chars_in_buffer)
		return tty->ops->chars_in_buffer(tty);
	return 0;
}
EXPORT_SYMBOL(tty_chars_in_buffer);

/**
 * tty_write_room - write queue space
 * @tty: terminal
 *
 * Returns: the number of bytes that can be queued to this device at the present
 * time. The result should be treated as a guarantee and the driver cannot
 * offer a value it later shrinks by more than the number of bytes written. If
 * no method is provided, 2K is always returned and data may be lost as there
 * will be no flow control.
 */
unsigned int tty_write_room(struct tty_struct *tty)
{
	if (tty->ops->write_room)
		return tty->ops->write_room(tty);
	return 2048;
}
EXPORT_SYMBOL(tty_write_room);

/**
 * tty_driver_flush_buffer - discard internal buffer
 * @tty: terminal
 *
 * Discard the internal output buffer for this device. If no method is provided,
 * then either the buffer cannot be hardware flushed or there is no buffer
 * driver side.
 */
void tty_driver_flush_buffer(struct tty_struct *tty)
{
	if (tty->ops->flush_buffer)
		tty->ops->flush_buffer(tty);
}
EXPORT_SYMBOL(tty_driver_flush_buffer);

/**
 * tty_unthrottle - flow control
 * @tty: terminal
 *
 * Indicate that a @tty may continue transmitting data down the stack. Takes
 * the &tty_struct->termios_rwsem to protect against parallel
 * throttle/unthrottle and also to ensure the driver can consistently reference
 * its own termios data at this point when implementing software flow control.
 *
 * Drivers should however remember that the stack can issue a throttle, then
 * change flow control method, then unthrottle.
 */
void tty_unthrottle(struct tty_struct *tty)
{
	down_write(&tty->termios_rwsem);
	if (test_and_clear_bit(TTY_THROTTLED, &tty->flags) &&
	    tty->ops->unthrottle)
		tty->ops->unthrottle(tty);
	tty->flow_change = TTY_FLOW_NO_CHANGE;
	up_write(&tty->termios_rwsem);
}
EXPORT_SYMBOL(tty_unthrottle);

/**
 * tty_throttle_safe - flow control
 * @tty: terminal
 *
 * Indicate that a @tty should stop transmitting data down the stack.
 * tty_throttle_safe() will only attempt throttle if @tty->flow_change is
 * %TTY_THROTTLE_SAFE. Prevents an accidental throttle due to race conditions
 * when throttling is conditional on factors evaluated prior to throttling.
 *
 * Returns: %true if @tty is throttled (or was already throttled)
 */
bool tty_throttle_safe(struct tty_struct *tty)
{
	bool ret = true;

	mutex_lock(&tty->throttle_mutex);
	if (!tty_throttled(tty)) {
		if (tty->flow_change != TTY_THROTTLE_SAFE)
			ret = false;
		else {
			set_bit(TTY_THROTTLED, &tty->flags);
			if (tty->ops->throttle)
				tty->ops->throttle(tty);
		}
	}
	mutex_unlock(&tty->throttle_mutex);

	return ret;
}

/**
 * tty_unthrottle_safe - flow control
 * @tty: terminal
 *
 * Similar to tty_unthrottle() but will only attempt unthrottle if
 * @tty->flow_change is %TTY_UNTHROTTLE_SAFE. Prevents an accidental unthrottle
 * due to race conditions when unthrottling is conditional on factors evaluated
 * prior to unthrottling.
 *
 * Returns: %true if @tty is unthrottled (or was already unthrottled)
 */
bool tty_unthrottle_safe(struct tty_struct *tty)
{
	bool ret = true;

	mutex_lock(&tty->throttle_mutex);
	if (tty_throttled(tty)) {
		if (tty->flow_change != TTY_UNTHROTTLE_SAFE)
			ret = false;
		else {
			clear_bit(TTY_THROTTLED, &tty->flags);
			if (tty->ops->unthrottle)
				tty->ops->unthrottle(tty);
		}
	}
	mutex_unlock(&tty->throttle_mutex);

	return ret;
}

/**
 * tty_wait_until_sent - wait for I/O to finish
 * @tty: tty we are waiting for
 * @timeout: how long we will wait
 *
 * Wait for characters pending in a tty driver to hit the wire, or for a
 * timeout to occur (eg due to flow control).
 *
 * Locking: none
 */

void tty_wait_until_sent(struct tty_struct *tty, long timeout)
{
	if (!timeout)
		timeout = MAX_SCHEDULE_TIMEOUT;

	timeout = wait_event_interruptible_timeout(tty->write_wait,
			!tty_chars_in_buffer(tty), timeout);
	if (timeout <= 0)
		return;

	if (timeout == MAX_SCHEDULE_TIMEOUT)
		timeout = 0;

	if (tty->ops->wait_until_sent)
		tty->ops->wait_until_sent(tty, timeout);
}
EXPORT_SYMBOL(tty_wait_until_sent);


/*
 *		Termios Helper Methods
 */

static void unset_locked_termios(struct tty_struct *tty, const struct ktermios *old)
{
	struct ktermios *termios = &tty->termios;
	struct ktermios *locked  = &tty->termios_locked;
	int	i;

#define NOSET_MASK(x, y, z) (x = ((x) & ~(z)) | ((y) & (z)))

	NOSET_MASK(termios->c_iflag, old->c_iflag, locked->c_iflag);
	NOSET_MASK(termios->c_oflag, old->c_oflag, locked->c_oflag);
	NOSET_MASK(termios->c_cflag, old->c_cflag, locked->c_cflag);
	NOSET_MASK(termios->c_lflag, old->c_lflag, locked->c_lflag);
	termios->c_line = locked->c_line ? old->c_line : termios->c_line;
	for (i = 0; i < NCCS; i++)
		termios->c_cc[i] = locked->c_cc[i] ?
			old->c_cc[i] : termios->c_cc[i];
	/* FIXME: What should we do for i/ospeed */
}

/**
 * tty_termios_copy_hw - copy hardware settings
 * @new: new termios
 * @old: old termios
 *
 * Propagate the hardware specific terminal setting bits from the @old termios
 * structure to the @new one. This is used in cases where the hardware does not
 * support reconfiguration or as a helper in some cases where only minimal
 * reconfiguration is supported.
 */
void tty_termios_copy_hw(struct ktermios *new, const struct ktermios *old)
{
	/* The bits a dumb device handles in software. Smart devices need
	   to always provide a set_termios method */
	new->c_cflag &= HUPCL | CREAD | CLOCAL;
	new->c_cflag |= old->c_cflag & ~(HUPCL | CREAD | CLOCAL);
	new->c_ispeed = old->c_ispeed;
	new->c_ospeed = old->c_ospeed;
}
EXPORT_SYMBOL(tty_termios_copy_hw);

/**
 * tty_termios_hw_change - check for setting change
 * @a: termios
 * @b: termios to compare
 *
 * Check if any of the bits that affect a dumb device have changed between the
 * two termios structures, or a speed change is needed.
 *
 * Returns: %true if change is needed
 */
bool tty_termios_hw_change(const struct ktermios *a, const struct ktermios *b)
{
	if (a->c_ispeed != b->c_ispeed || a->c_ospeed != b->c_ospeed)
		return true;
	if ((a->c_cflag ^ b->c_cflag) & ~(HUPCL | CREAD | CLOCAL))
		return true;
	return false;
}
EXPORT_SYMBOL(tty_termios_hw_change);

/**
 * tty_get_char_size - get size of a character
 * @cflag: termios cflag value
 *
 * Returns: size (in bits) of a character depending on @cflag's %CSIZE setting
 */
unsigned char tty_get_char_size(unsigned int cflag)
{
	switch (cflag & CSIZE) {
	case CS5:
		return 5;
	case CS6:
		return 6;
	case CS7:
		return 7;
	case CS8:
	default:
		return 8;
	}
}
EXPORT_SYMBOL_GPL(tty_get_char_size);

/**
 * tty_get_frame_size - get size of a frame
 * @cflag: termios cflag value
 *
 * Get the size (in bits) of a frame depending on @cflag's %CSIZE, %CSTOPB, and
 * %PARENB setting. The result is a sum of character size, start and stop bits
 * -- one bit each -- second stop bit (if set), and parity bit (if set).
 *
 * Returns: size (in bits) of a frame depending on @cflag's setting.
 */
unsigned char tty_get_frame_size(unsigned int cflag)
{
	unsigned char bits = 2 + tty_get_char_size(cflag);

	if (cflag & CSTOPB)
		bits++;
	if (cflag & PARENB)
		bits++;
	if (cflag & ADDRB)
		bits++;

	return bits;
}
EXPORT_SYMBOL_GPL(tty_get_frame_size);

/**
 * tty_set_termios - update termios values
 * @tty: tty to update
 * @new_termios: desired new value
 *
 * Perform updates to the termios values set on this @tty. A master pty's
 * termios should never be set.
 *
 * Locking: &tty_struct->termios_rwsem
 */
int tty_set_termios(struct tty_struct *tty, struct ktermios *new_termios)
{
	struct ktermios old_termios;
	struct tty_ldisc *ld;

	WARN_ON(tty->driver->type == TTY_DRIVER_TYPE_PTY &&
		tty->driver->subtype == PTY_TYPE_MASTER);
	/*
	 *	Perform the actual termios internal changes under lock.
	 */


	/* FIXME: we need to decide on some locking/ordering semantics
	   for the set_termios notification eventually */
	down_write(&tty->termios_rwsem);
	old_termios = tty->termios;
	tty->termios = *new_termios;
	unset_locked_termios(tty, &old_termios);
	/* Reset any ADDRB changes, ADDRB is changed through ->rs485_config() */
	tty->termios.c_cflag ^= (tty->termios.c_cflag ^ old_termios.c_cflag) & ADDRB;

	if (tty->ops->set_termios)
		tty->ops->set_termios(tty, &old_termios);
	else
		tty_termios_copy_hw(&tty->termios, &old_termios);

	ld = tty_ldisc_ref(tty);
	if (ld != NULL) {
		if (ld->ops->set_termios)
			ld->ops->set_termios(tty, &old_termios);
		tty_ldisc_deref(ld);
	}
	up_write(&tty->termios_rwsem);
	return 0;
}
EXPORT_SYMBOL_GPL(tty_set_termios);


/*
 * Translate a "termio" structure into a "termios". Ugh.
 */
__weak int user_termio_to_kernel_termios(struct ktermios *termios,
						struct termio __user *termio)
{
	struct termio v;

	if (copy_from_user(&v, termio, sizeof(struct termio)))
		return -EFAULT;

	termios->c_iflag = (0xffff0000 & termios->c_iflag) | v.c_iflag;
	termios->c_oflag = (0xffff0000 & termios->c_oflag) | v.c_oflag;
	termios->c_cflag = (0xffff0000 & termios->c_cflag) | v.c_cflag;
	termios->c_lflag = (0xffff0000 & termios->c_lflag) | v.c_lflag;
	termios->c_line = (0xffff0000 & termios->c_lflag) | v.c_line;
	memcpy(termios->c_cc, v.c_cc, NCC);
	return 0;
}

/*
 * Translate a "termios" structure into a "termio". Ugh.
 */
__weak int kernel_termios_to_user_termio(struct termio __user *termio,
						struct ktermios *termios)
{
	struct termio v;
	memset(&v, 0, sizeof(struct termio));
	v.c_iflag = termios->c_iflag;
	v.c_oflag = termios->c_oflag;
	v.c_cflag = termios->c_cflag;
	v.c_lflag = termios->c_lflag;
	v.c_line = termios->c_line;
	memcpy(v.c_cc, termios->c_cc, NCC);
	return copy_to_user(termio, &v, sizeof(struct termio));
}

#ifdef TCGETS2
__weak int user_termios_to_kernel_termios(struct ktermios *k,
						 struct termios2 __user *u)
{
	return copy_from_user(k, u, sizeof(struct termios2));
}
__weak int kernel_termios_to_user_termios(struct termios2 __user *u,
						 struct ktermios *k)
{
	return copy_to_user(u, k, sizeof(struct termios2));
}
__weak int user_termios_to_kernel_termios_1(struct ktermios *k,
						   struct termios __user *u)
{
	return copy_from_user(k, u, sizeof(struct termios));
}
__weak int kernel_termios_to_user_termios_1(struct termios __user *u,
						   struct ktermios *k)
{
	return copy_to_user(u, k, sizeof(struct termios));
}

#else

__weak int user_termios_to_kernel_termios(struct ktermios *k,
						 struct termios __user *u)
{
	return copy_from_user(k, u, sizeof(struct termios));
}
__weak int kernel_termios_to_user_termios(struct termios __user *u,
						 struct ktermios *k)
{
	return copy_to_user(u, k, sizeof(struct termios));
}
#endif /* TCGETS2 */

/**
 * set_termios - set termios values for a tty
 * @tty: terminal device
 * @arg: user data
 * @opt: option information
 *
 * Helper function to prepare termios data and run necessary other functions
 * before using tty_set_termios() to do the actual changes.
 *
 * Locking: called functions take &tty_struct->ldisc_sem and
 * &tty_struct->termios_rwsem locks
 *
 * Returns: 0 on success, an error otherwise
 */
static int set_termios(struct tty_struct *tty, void __user *arg, int opt)
{
	struct ktermios tmp_termios;
	struct tty_ldisc *ld;
	int retval = tty_check_change(tty);

	if (retval)
		return retval;

	down_read(&tty->termios_rwsem);
	tmp_termios = tty->termios;
	up_read(&tty->termios_rwsem);

	if (opt & TERMIOS_TERMIO) {
		if (user_termio_to_kernel_termios(&tmp_termios,
						(struct termio __user *)arg))
			return -EFAULT;
#ifdef TCGETS2
	} else if (opt & TERMIOS_OLD) {
		if (user_termios_to_kernel_termios_1(&tmp_termios,
						(struct termios __user *)arg))
			return -EFAULT;
	} else {
		if (user_termios_to_kernel_termios(&tmp_termios,
						(struct termios2 __user *)arg))
			return -EFAULT;
	}
#else
	} else if (user_termios_to_kernel_termios(&tmp_termios,
					(struct termios __user *)arg))
		return -EFAULT;
#endif

	/* If old style Bfoo values are used then load c_ispeed/c_ospeed
	 * with the real speed so its unconditionally usable */
	tmp_termios.c_ispeed = tty_termios_input_baud_rate(&tmp_termios);
	tmp_termios.c_ospeed = tty_termios_baud_rate(&tmp_termios);

	if (opt & (TERMIOS_FLUSH|TERMIOS_WAIT)) {
retry_write_wait:
		retval = wait_event_interruptible(tty->write_wait, !tty_chars_in_buffer(tty));
		if (retval < 0)
			return retval;

		if (tty_write_lock(tty, false) < 0)
			goto retry_write_wait;

		/* Racing writer? */
		if (tty_chars_in_buffer(tty)) {
			tty_write_unlock(tty);
			goto retry_write_wait;
		}

		ld = tty_ldisc_ref(tty);
		if (ld != NULL) {
			if ((opt & TERMIOS_FLUSH) && ld->ops->flush_buffer)
				ld->ops->flush_buffer(tty);
			tty_ldisc_deref(ld);
		}

		if ((opt & TERMIOS_WAIT) && tty->ops->wait_until_sent) {
			tty->ops->wait_until_sent(tty, 0);
			if (signal_pending(current)) {
				tty_write_unlock(tty);
				return -ERESTARTSYS;
			}
		}

		tty_set_termios(tty, &tmp_termios);

		tty_write_unlock(tty);
	} else {
		tty_set_termios(tty, &tmp_termios);
	}

	/* FIXME: Arguably if tmp_termios == tty->termios AND the
	   actual requested termios was not tmp_termios then we may
	   want to return an error as no user requested change has
	   succeeded */
	return 0;
}

static void copy_termios(struct tty_struct *tty, struct ktermios *kterm)
{
	down_read(&tty->termios_rwsem);
	*kterm = tty->termios;
	up_read(&tty->termios_rwsem);
}

static void copy_termios_locked(struct tty_struct *tty, struct ktermios *kterm)
{
	down_read(&tty->termios_rwsem);
	*kterm = tty->termios_locked;
	up_read(&tty->termios_rwsem);
}

static int get_termio(struct tty_struct *tty, struct termio __user *termio)
{
	struct ktermios kterm;
	copy_termios(tty, &kterm);
	if (kernel_termios_to_user_termio(termio, &kterm))
		return -EFAULT;
	return 0;
}

#ifdef TIOCGETP
/*
 * These are deprecated, but there is limited support..
 *
 * The "sg_flags" translation is a joke..
 */
static int get_sgflags(struct tty_struct *tty)
{
	int flags = 0;

	if (!L_ICANON(tty)) {
		if (L_ISIG(tty))
			flags |= 0x02;		/* cbreak */
		else
			flags |= 0x20;		/* raw */
	}
	if (L_ECHO(tty))
		flags |= 0x08;			/* echo */
	if (O_OPOST(tty))
		if (O_ONLCR(tty))
			flags |= 0x10;		/* crmod */
	return flags;
}

static int get_sgttyb(struct tty_struct *tty, struct sgttyb __user *sgttyb)
{
	struct sgttyb tmp;

	down_read(&tty->termios_rwsem);
	tmp.sg_ispeed = tty->termios.c_ispeed;
	tmp.sg_ospeed = tty->termios.c_ospeed;
	tmp.sg_erase = tty->termios.c_cc[VERASE];
	tmp.sg_kill = tty->termios.c_cc[VKILL];
	tmp.sg_flags = get_sgflags(tty);
	up_read(&tty->termios_rwsem);

	return copy_to_user(sgttyb, &tmp, sizeof(tmp)) ? -EFAULT : 0;
}

static void set_sgflags(struct ktermios *termios, int flags)
{
	termios->c_iflag = ICRNL | IXON;
	termios->c_oflag = 0;
	termios->c_lflag = ISIG | ICANON;
	if (flags & 0x02) {	/* cbreak */
		termios->c_iflag = 0;
		termios->c_lflag &= ~ICANON;
	}
	if (flags & 0x08) {		/* echo */
		termios->c_lflag |= ECHO | ECHOE | ECHOK |
				    ECHOCTL | ECHOKE | IEXTEN;
	}
	if (flags & 0x10) {		/* crmod */
		termios->c_oflag |= OPOST | ONLCR;
	}
	if (flags & 0x20) {	/* raw */
		termios->c_iflag = 0;
		termios->c_lflag &= ~(ISIG | ICANON);
	}
	if (!(termios->c_lflag & ICANON)) {
		termios->c_cc[VMIN] = 1;
		termios->c_cc[VTIME] = 0;
	}
}

/**
 * set_sgttyb - set legacy terminal values
 * @tty: tty structure
 * @sgttyb: pointer to old style terminal structure
 *
 * Updates a terminal from the legacy BSD style terminal information structure.
 *
 * Locking: &tty_struct->termios_rwsem
 *
 * Returns: 0 on success, an error otherwise
 */
static int set_sgttyb(struct tty_struct *tty, struct sgttyb __user *sgttyb)
{
	int retval;
	struct sgttyb tmp;
	struct ktermios termios;

	retval = tty_check_change(tty);
	if (retval)
		return retval;

	if (copy_from_user(&tmp, sgttyb, sizeof(tmp)))
		return -EFAULT;

	down_write(&tty->termios_rwsem);
	termios = tty->termios;
	termios.c_cc[VERASE] = tmp.sg_erase;
	termios.c_cc[VKILL] = tmp.sg_kill;
	set_sgflags(&termios, tmp.sg_flags);
	/* Try and encode into Bfoo format */
	tty_termios_encode_baud_rate(&termios, termios.c_ispeed,
						termios.c_ospeed);
	up_write(&tty->termios_rwsem);
	tty_set_termios(tty, &termios);
	return 0;
}
#endif

#ifdef TIOCGETC
static int get_tchars(struct tty_struct *tty, struct tchars __user *tchars)
{
	struct tchars tmp;

	down_read(&tty->termios_rwsem);
	tmp.t_intrc = tty->termios.c_cc[VINTR];
	tmp.t_quitc = tty->termios.c_cc[VQUIT];
	tmp.t_startc = tty->termios.c_cc[VSTART];
	tmp.t_stopc = tty->termios.c_cc[VSTOP];
	tmp.t_eofc = tty->termios.c_cc[VEOF];
	tmp.t_brkc = tty->termios.c_cc[VEOL2];	/* what is brkc anyway? */
	up_read(&tty->termios_rwsem);
	return copy_to_user(tchars, &tmp, sizeof(tmp)) ? -EFAULT : 0;
}

static int set_tchars(struct tty_struct *tty, struct tchars __user *tchars)
{
	struct tchars tmp;

	if (copy_from_user(&tmp, tchars, sizeof(tmp)))
		return -EFAULT;
	down_write(&tty->termios_rwsem);
	tty->termios.c_cc[VINTR] = tmp.t_intrc;
	tty->termios.c_cc[VQUIT] = tmp.t_quitc;
	tty->termios.c_cc[VSTART] = tmp.t_startc;
	tty->termios.c_cc[VSTOP] = tmp.t_stopc;
	tty->termios.c_cc[VEOF] = tmp.t_eofc;
	tty->termios.c_cc[VEOL2] = tmp.t_brkc;	/* what is brkc anyway? */
	up_write(&tty->termios_rwsem);
	return 0;
}
#endif

#ifdef TIOCGLTC
static int get_ltchars(struct tty_struct *tty, struct ltchars __user *ltchars)
{
	struct ltchars tmp;

	down_read(&tty->termios_rwsem);
	tmp.t_suspc = tty->termios.c_cc[VSUSP];
	/* what is dsuspc anyway? */
	tmp.t_dsuspc = tty->termios.c_cc[VSUSP];
	tmp.t_rprntc = tty->termios.c_cc[VREPRINT];
	/* what is flushc anyway? */
	tmp.t_flushc = tty->termios.c_cc[VEOL2];
	tmp.t_werasc = tty->termios.c_cc[VWERASE];
	tmp.t_lnextc = tty->termios.c_cc[VLNEXT];
	up_read(&tty->termios_rwsem);
	return copy_to_user(ltchars, &tmp, sizeof(tmp)) ? -EFAULT : 0;
}

static int set_ltchars(struct tty_struct *tty, struct ltchars __user *ltchars)
{
	struct ltchars tmp;

	if (copy_from_user(&tmp, ltchars, sizeof(tmp)))
		return -EFAULT;

	down_write(&tty->termios_rwsem);
	tty->termios.c_cc[VSUSP] = tmp.t_suspc;
	/* what is dsuspc anyway? */
	tty->termios.c_cc[VEOL2] = tmp.t_dsuspc;
	tty->termios.c_cc[VREPRINT] = tmp.t_rprntc;
	/* what is flushc anyway? */
	tty->termios.c_cc[VEOL2] = tmp.t_flushc;
	tty->termios.c_cc[VWERASE] = tmp.t_werasc;
	tty->termios.c_cc[VLNEXT] = tmp.t_lnextc;
	up_write(&tty->termios_rwsem);
	return 0;
}
#endif

/**
 * tty_change_softcar - carrier change ioctl helper
 * @tty: tty to update
 * @enable: enable/disable %CLOCAL
 *
 * Perform a change to the %CLOCAL state and call into the driver layer to make
 * it visible.
 *
 * Locking: &tty_struct->termios_rwsem.
 *
 * Returns: 0 on success, an error otherwise
 */
static int tty_change_softcar(struct tty_struct *tty, bool enable)
{
	int ret = 0;
	struct ktermios old;
	tcflag_t bit = enable ? CLOCAL : 0;

	down_write(&tty->termios_rwsem);
	old = tty->termios;
	tty->termios.c_cflag &= ~CLOCAL;
	tty->termios.c_cflag |= bit;
	if (tty->ops->set_termios)
		tty->ops->set_termios(tty, &old);
	if (C_CLOCAL(tty) != bit)
		ret = -EINVAL;
	up_write(&tty->termios_rwsem);
	return ret;
}

/**
 * tty_mode_ioctl - mode related ioctls
 * @tty: tty for the ioctl
 * @cmd: command
 * @arg: ioctl argument
 *
 * Perform non-line discipline specific mode control ioctls. This is designed
 * to be called by line disciplines to ensure they provide consistent mode
 * setting.
 */
int tty_mode_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)
{
	struct tty_struct *real_tty;
	void __user *p = (void __user *)arg;
	int ret = 0;
	struct ktermios kterm;

	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
	    tty->driver->subtype == PTY_TYPE_MASTER)
		real_tty = tty->link;
	else
		real_tty = tty;

	switch (cmd) {
#ifdef TIOCGETP
	case TIOCGETP:
		return get_sgttyb(real_tty, (struct sgttyb __user *) arg);
	case TIOCSETP:
	case TIOCSETN:
		return set_sgttyb(real_tty, (struct sgttyb __user *) arg);
#endif
#ifdef TIOCGETC
	case TIOCGETC:
		return get_tchars(real_tty, p);
	case TIOCSETC:
		return set_tchars(real_tty, p);
#endif
#ifdef TIOCGLTC
	case TIOCGLTC:
		return get_ltchars(real_tty, p);
	case TIOCSLTC:
		return set_ltchars(real_tty, p);
#endif
	case TCSETSF:
		return set_termios(real_tty, p,  TERMIOS_FLUSH | TERMIOS_WAIT | TERMIOS_OLD);
	case TCSETSW:
		return set_termios(real_tty, p, TERMIOS_WAIT | TERMIOS_OLD);
	case TCSETS:
		return set_termios(real_tty, p, TERMIOS_OLD);
#ifndef TCGETS2
	case TCGETS:
		copy_termios(real_tty, &kterm);
		if (kernel_termios_to_user_termios((struct termios __user *)arg, &kterm))
			ret = -EFAULT;
		return ret;
#else
	case TCGETS:
		copy_termios(real_tty, &kterm);
		if (kernel_termios_to_user_termios_1((struct termios __user *)arg, &kterm))
			ret = -EFAULT;
		return ret;
	case TCGETS2:
		copy_termios(real_tty, &kterm);
		if (kernel_termios_to_user_termios((struct termios2 __user *)arg, &kterm))
			ret = -EFAULT;
		return ret;
	case TCSETSF2:
		return set_termios(real_tty, p,  TERMIOS_FLUSH | TERMIOS_WAIT);
	case TCSETSW2:
		return set_termios(real_tty, p, TERMIOS_WAIT);
	case TCSETS2:
		return set_termios(real_tty, p, 0);
#endif
	case TCGETA:
		return get_termio(real_tty, p);
	case TCSETAF:
		return set_termios(real_tty, p, TERMIOS_FLUSH | TERMIOS_WAIT | TERMIOS_TERMIO);
	case TCSETAW:
		return set_termios(real_tty, p, TERMIOS_WAIT | TERMIOS_TERMIO);
	case TCSETA:
		return set_termios(real_tty, p, TERMIOS_TERMIO);
#ifndef TCGETS2
	case TIOCGLCKTRMIOS:
		copy_termios_locked(real_tty, &kterm);
		if (kernel_termios_to_user_termios((struct termios __user *)arg, &kterm))
			ret = -EFAULT;
		return ret;
	case TIOCSLCKTRMIOS:
		if (!checkpoint_restore_ns_capable(&init_user_ns))
			return -EPERM;
		copy_termios_locked(real_tty, &kterm);
		if (user_termios_to_kernel_termios(&kterm,
					       (struct termios __user *) arg))
			return -EFAULT;
		down_write(&real_tty->termios_rwsem);
		real_tty->termios_locked = kterm;
		up_write(&real_tty->termios_rwsem);
		return 0;
#else
	case TIOCGLCKTRMIOS:
		copy_termios_locked(real_tty, &kterm);
		if (kernel_termios_to_user_termios_1((struct termios __user *)arg, &kterm))
			ret = -EFAULT;
		return ret;
	case TIOCSLCKTRMIOS:
		if (!checkpoint_restore_ns_capable(&init_user_ns))
			return -EPERM;
		copy_termios_locked(real_tty, &kterm);
		if (user_termios_to_kernel_termios_1(&kterm,
					       (struct termios __user *) arg))
			return -EFAULT;
		down_write(&real_tty->termios_rwsem);
		real_tty->termios_locked = kterm;
		up_write(&real_tty->termios_rwsem);
		return ret;
#endif
#ifdef TCGETX
	case TCGETX:
	case TCSETX:
	case TCSETXW:
	case TCSETXF:
		return -ENOTTY;
#endif
	case TIOCGSOFTCAR:
		copy_termios(real_tty, &kterm);
		ret = put_user((kterm.c_cflag & CLOCAL) ? 1 : 0,
						(int __user *)arg);
		return ret;
	case TIOCSSOFTCAR:
		if (get_user(arg, (unsigned int __user *) arg))
			return -EFAULT;
		return tty_change_softcar(real_tty, arg);
	default:
		return -ENOIOCTLCMD;
	}
}
EXPORT_SYMBOL_GPL(tty_mode_ioctl);


/* Caller guarantees ldisc reference is held */
static int __tty_perform_flush(struct tty_struct *tty, unsigned long arg)
{
	struct tty_ldisc *ld = tty->ldisc;

	switch (arg) {
	case TCIFLUSH:
		if (ld && ld->ops->flush_buffer) {
			ld->ops->flush_buffer(tty);
			tty_unthrottle(tty);
		}
		break;
	case TCIOFLUSH:
		if (ld && ld->ops->flush_buffer) {
			ld->ops->flush_buffer(tty);
			tty_unthrottle(tty);
		}
		fallthrough;
	case TCOFLUSH:
		tty_driver_flush_buffer(tty);
		break;
	default:
		return -EINVAL;
	}
	return 0;
}

int tty_perform_flush(struct tty_struct *tty, unsigned long arg)
{
	struct tty_ldisc *ld;
	int retval = tty_check_change(tty);
	if (retval)
		return retval;

	ld = tty_ldisc_ref_wait(tty);
	retval = __tty_perform_flush(tty, arg);
	if (ld)
		tty_ldisc_deref(ld);
	return retval;
}
EXPORT_SYMBOL_GPL(tty_perform_flush);

int n_tty_ioctl_helper(struct tty_struct *tty, unsigned int cmd,
		unsigned long arg)
{
	int retval;

	switch (cmd) {
	case TCXONC:
		retval = tty_check_change(tty);
		if (retval)
			return retval;
		switch (arg) {
		case TCOOFF:
			spin_lock_irq(&tty->flow.lock);
			if (!tty->flow.tco_stopped) {
				tty->flow.tco_stopped = true;
				__stop_tty(tty);
			}
			spin_unlock_irq(&tty->flow.lock);
			break;
		case TCOON:
			spin_lock_irq(&tty->flow.lock);
			if (tty->flow.tco_stopped) {
				tty->flow.tco_stopped = false;
				__start_tty(tty);
			}
			spin_unlock_irq(&tty->flow.lock);
			break;
		case TCIOFF:
			if (STOP_CHAR(tty) != __DISABLED_CHAR)
				retval = tty_send_xchar(tty, STOP_CHAR(tty));
			break;
		case TCION:
			if (START_CHAR(tty) != __DISABLED_CHAR)
				retval = tty_send_xchar(tty, START_CHAR(tty));
			break;
		default:
			return -EINVAL;
		}
		return retval;
	case TCFLSH:
		retval = tty_check_change(tty);
		if (retval)
			return retval;
		return __tty_perform_flush(tty, arg);
	default:
		/* Try the mode commands */
		return tty_mode_ioctl(tty, cmd, arg);
	}
}
EXPORT_SYMBOL(n_tty_ioctl_helper);