xref: /openbmc/linux/drivers/tty/vt/vt_ioctl.c (revision 9344dade)
1 /*
2  *  Copyright (C) 1992 obz under the linux copyright
3  *
4  *  Dynamic diacritical handling - aeb@cwi.nl - Dec 1993
5  *  Dynamic keymap and string allocation - aeb@cwi.nl - May 1994
6  *  Restrict VT switching via ioctl() - grif@cs.ucr.edu - Dec 1995
7  *  Some code moved for less code duplication - Andi Kleen - Mar 1997
8  *  Check put/get_user, cleanups - acme@conectiva.com.br - Jun 2001
9  */
10 
11 #include <linux/types.h>
12 #include <linux/errno.h>
13 #include <linux/sched.h>
14 #include <linux/tty.h>
15 #include <linux/timer.h>
16 #include <linux/kernel.h>
17 #include <linux/compat.h>
18 #include <linux/module.h>
19 #include <linux/kd.h>
20 #include <linux/vt.h>
21 #include <linux/string.h>
22 #include <linux/slab.h>
23 #include <linux/major.h>
24 #include <linux/fs.h>
25 #include <linux/console.h>
26 #include <linux/consolemap.h>
27 #include <linux/signal.h>
28 #include <linux/suspend.h>
29 #include <linux/timex.h>
30 
31 #include <asm/io.h>
32 #include <asm/uaccess.h>
33 
34 #include <linux/kbd_kern.h>
35 #include <linux/vt_kern.h>
36 #include <linux/kbd_diacr.h>
37 #include <linux/selection.h>
38 
39 char vt_dont_switch;
40 extern struct tty_driver *console_driver;
41 
42 #define VT_IS_IN_USE(i)	(console_driver->ttys[i] && console_driver->ttys[i]->count)
43 #define VT_BUSY(i)	(VT_IS_IN_USE(i) || i == fg_console || vc_cons[i].d == sel_cons)
44 
45 /*
46  * Console (vt and kd) routines, as defined by USL SVR4 manual, and by
47  * experimentation and study of X386 SYSV handling.
48  *
49  * One point of difference: SYSV vt's are /dev/vtX, which X >= 0, and
50  * /dev/console is a separate ttyp. Under Linux, /dev/tty0 is /dev/console,
51  * and the vc start at /dev/ttyX, X >= 1. We maintain that here, so we will
52  * always treat our set of vt as numbered 1..MAX_NR_CONSOLES (corresponding to
53  * ttys 0..MAX_NR_CONSOLES-1). Explicitly naming VT 0 is illegal, but using
54  * /dev/tty0 (fg_console) as a target is legal, since an implicit aliasing
55  * to the current console is done by the main ioctl code.
56  */
57 
58 #ifdef CONFIG_X86
59 #include <linux/syscalls.h>
60 #endif
61 
62 static void complete_change_console(struct vc_data *vc);
63 
64 /*
65  *	User space VT_EVENT handlers
66  */
67 
68 struct vt_event_wait {
69 	struct list_head list;
70 	struct vt_event event;
71 	int done;
72 };
73 
74 static LIST_HEAD(vt_events);
75 static DEFINE_SPINLOCK(vt_event_lock);
76 static DECLARE_WAIT_QUEUE_HEAD(vt_event_waitqueue);
77 
78 /**
79  *	vt_event_post
80  *	@event: the event that occurred
81  *	@old: old console
82  *	@new: new console
83  *
84  *	Post an VT event to interested VT handlers
85  */
86 
87 void vt_event_post(unsigned int event, unsigned int old, unsigned int new)
88 {
89 	struct list_head *pos, *head;
90 	unsigned long flags;
91 	int wake = 0;
92 
93 	spin_lock_irqsave(&vt_event_lock, flags);
94 	head = &vt_events;
95 
96 	list_for_each(pos, head) {
97 		struct vt_event_wait *ve = list_entry(pos,
98 						struct vt_event_wait, list);
99 		if (!(ve->event.event & event))
100 			continue;
101 		ve->event.event = event;
102 		/* kernel view is consoles 0..n-1, user space view is
103 		   console 1..n with 0 meaning current, so we must bias */
104 		ve->event.oldev = old + 1;
105 		ve->event.newev = new + 1;
106 		wake = 1;
107 		ve->done = 1;
108 	}
109 	spin_unlock_irqrestore(&vt_event_lock, flags);
110 	if (wake)
111 		wake_up_interruptible(&vt_event_waitqueue);
112 }
113 
114 static void __vt_event_queue(struct vt_event_wait *vw)
115 {
116 	unsigned long flags;
117 	/* Prepare the event */
118 	INIT_LIST_HEAD(&vw->list);
119 	vw->done = 0;
120 	/* Queue our event */
121 	spin_lock_irqsave(&vt_event_lock, flags);
122 	list_add(&vw->list, &vt_events);
123 	spin_unlock_irqrestore(&vt_event_lock, flags);
124 }
125 
126 static void __vt_event_wait(struct vt_event_wait *vw)
127 {
128 	/* Wait for it to pass */
129 	wait_event_interruptible(vt_event_waitqueue, vw->done);
130 }
131 
132 static void __vt_event_dequeue(struct vt_event_wait *vw)
133 {
134 	unsigned long flags;
135 
136 	/* Dequeue it */
137 	spin_lock_irqsave(&vt_event_lock, flags);
138 	list_del(&vw->list);
139 	spin_unlock_irqrestore(&vt_event_lock, flags);
140 }
141 
142 /**
143  *	vt_event_wait		-	wait for an event
144  *	@vw: our event
145  *
146  *	Waits for an event to occur which completes our vt_event_wait
147  *	structure. On return the structure has wv->done set to 1 for success
148  *	or 0 if some event such as a signal ended the wait.
149  */
150 
151 static void vt_event_wait(struct vt_event_wait *vw)
152 {
153 	__vt_event_queue(vw);
154 	__vt_event_wait(vw);
155 	__vt_event_dequeue(vw);
156 }
157 
158 /**
159  *	vt_event_wait_ioctl	-	event ioctl handler
160  *	@arg: argument to ioctl
161  *
162  *	Implement the VT_WAITEVENT ioctl using the VT event interface
163  */
164 
165 static int vt_event_wait_ioctl(struct vt_event __user *event)
166 {
167 	struct vt_event_wait vw;
168 
169 	if (copy_from_user(&vw.event, event, sizeof(struct vt_event)))
170 		return -EFAULT;
171 	/* Highest supported event for now */
172 	if (vw.event.event & ~VT_MAX_EVENT)
173 		return -EINVAL;
174 
175 	vt_event_wait(&vw);
176 	/* If it occurred report it */
177 	if (vw.done) {
178 		if (copy_to_user(event, &vw.event, sizeof(struct vt_event)))
179 			return -EFAULT;
180 		return 0;
181 	}
182 	return -EINTR;
183 }
184 
185 /**
186  *	vt_waitactive	-	active console wait
187  *	@event: event code
188  *	@n: new console
189  *
190  *	Helper for event waits. Used to implement the legacy
191  *	event waiting ioctls in terms of events
192  */
193 
194 int vt_waitactive(int n)
195 {
196 	struct vt_event_wait vw;
197 	do {
198 		vw.event.event = VT_EVENT_SWITCH;
199 		__vt_event_queue(&vw);
200 		if (n == fg_console + 1) {
201 			__vt_event_dequeue(&vw);
202 			break;
203 		}
204 		__vt_event_wait(&vw);
205 		__vt_event_dequeue(&vw);
206 		if (vw.done == 0)
207 			return -EINTR;
208 	} while (vw.event.newev != n);
209 	return 0;
210 }
211 
212 /*
213  * these are the valid i/o ports we're allowed to change. they map all the
214  * video ports
215  */
216 #define GPFIRST 0x3b4
217 #define GPLAST 0x3df
218 #define GPNUM (GPLAST - GPFIRST + 1)
219 
220 
221 
222 static inline int
223 do_fontx_ioctl(int cmd, struct consolefontdesc __user *user_cfd, int perm, struct console_font_op *op)
224 {
225 	struct consolefontdesc cfdarg;
226 	int i;
227 
228 	if (copy_from_user(&cfdarg, user_cfd, sizeof(struct consolefontdesc)))
229 		return -EFAULT;
230 
231 	switch (cmd) {
232 	case PIO_FONTX:
233 		if (!perm)
234 			return -EPERM;
235 		op->op = KD_FONT_OP_SET;
236 		op->flags = KD_FONT_FLAG_OLD;
237 		op->width = 8;
238 		op->height = cfdarg.charheight;
239 		op->charcount = cfdarg.charcount;
240 		op->data = cfdarg.chardata;
241 		return con_font_op(vc_cons[fg_console].d, op);
242 	case GIO_FONTX: {
243 		op->op = KD_FONT_OP_GET;
244 		op->flags = KD_FONT_FLAG_OLD;
245 		op->width = 8;
246 		op->height = cfdarg.charheight;
247 		op->charcount = cfdarg.charcount;
248 		op->data = cfdarg.chardata;
249 		i = con_font_op(vc_cons[fg_console].d, op);
250 		if (i)
251 			return i;
252 		cfdarg.charheight = op->height;
253 		cfdarg.charcount = op->charcount;
254 		if (copy_to_user(user_cfd, &cfdarg, sizeof(struct consolefontdesc)))
255 			return -EFAULT;
256 		return 0;
257 		}
258 	}
259 	return -EINVAL;
260 }
261 
262 static inline int
263 do_unimap_ioctl(int cmd, struct unimapdesc __user *user_ud, int perm, struct vc_data *vc)
264 {
265 	struct unimapdesc tmp;
266 
267 	if (copy_from_user(&tmp, user_ud, sizeof tmp))
268 		return -EFAULT;
269 	if (tmp.entries)
270 		if (!access_ok(VERIFY_WRITE, tmp.entries,
271 				tmp.entry_ct*sizeof(struct unipair)))
272 			return -EFAULT;
273 	switch (cmd) {
274 	case PIO_UNIMAP:
275 		if (!perm)
276 			return -EPERM;
277 		return con_set_unimap(vc, tmp.entry_ct, tmp.entries);
278 	case GIO_UNIMAP:
279 		if (!perm && fg_console != vc->vc_num)
280 			return -EPERM;
281 		return con_get_unimap(vc, tmp.entry_ct, &(user_ud->entry_ct), tmp.entries);
282 	}
283 	return 0;
284 }
285 
286 /* deallocate a single console, if possible (leave 0) */
287 static int vt_disallocate(unsigned int vc_num)
288 {
289 	struct vc_data *vc = NULL;
290 	int ret = 0;
291 
292 	console_lock();
293 	if (VT_BUSY(vc_num))
294 		ret = -EBUSY;
295 	else if (vc_num)
296 		vc = vc_deallocate(vc_num);
297 	console_unlock();
298 
299 	if (vc && vc_num >= MIN_NR_CONSOLES) {
300 		tty_port_destroy(&vc->port);
301 		kfree(vc);
302 	}
303 
304 	return ret;
305 }
306 
307 /* deallocate all unused consoles, but leave 0 */
308 static void vt_disallocate_all(void)
309 {
310 	struct vc_data *vc[MAX_NR_CONSOLES];
311 	int i;
312 
313 	console_lock();
314 	for (i = 1; i < MAX_NR_CONSOLES; i++)
315 		if (!VT_BUSY(i))
316 			vc[i] = vc_deallocate(i);
317 		else
318 			vc[i] = NULL;
319 	console_unlock();
320 
321 	for (i = 1; i < MAX_NR_CONSOLES; i++) {
322 		if (vc[i] && i >= MIN_NR_CONSOLES) {
323 			tty_port_destroy(&vc[i]->port);
324 			kfree(vc[i]);
325 		}
326 	}
327 }
328 
329 
330 /*
331  * We handle the console-specific ioctl's here.  We allow the
332  * capability to modify any console, not just the fg_console.
333  */
334 int vt_ioctl(struct tty_struct *tty,
335 	     unsigned int cmd, unsigned long arg)
336 {
337 	struct vc_data *vc = tty->driver_data;
338 	struct console_font_op op;	/* used in multiple places here */
339 	unsigned int console;
340 	unsigned char ucval;
341 	unsigned int uival;
342 	void __user *up = (void __user *)arg;
343 	int i, perm;
344 	int ret = 0;
345 
346 	console = vc->vc_num;
347 
348 
349 	if (!vc_cons_allocated(console)) { 	/* impossible? */
350 		ret = -ENOIOCTLCMD;
351 		goto out;
352 	}
353 
354 
355 	/*
356 	 * To have permissions to do most of the vt ioctls, we either have
357 	 * to be the owner of the tty, or have CAP_SYS_TTY_CONFIG.
358 	 */
359 	perm = 0;
360 	if (current->signal->tty == tty || capable(CAP_SYS_TTY_CONFIG))
361 		perm = 1;
362 
363 	switch (cmd) {
364 	case TIOCLINUX:
365 		ret = tioclinux(tty, arg);
366 		break;
367 	case KIOCSOUND:
368 		if (!perm)
369 			return -EPERM;
370 		/*
371 		 * The use of PIT_TICK_RATE is historic, it used to be
372 		 * the platform-dependent CLOCK_TICK_RATE between 2.6.12
373 		 * and 2.6.36, which was a minor but unfortunate ABI
374 		 * change. kd_mksound is locked by the input layer.
375 		 */
376 		if (arg)
377 			arg = PIT_TICK_RATE / arg;
378 		kd_mksound(arg, 0);
379 		break;
380 
381 	case KDMKTONE:
382 		if (!perm)
383 			return -EPERM;
384 	{
385 		unsigned int ticks, count;
386 
387 		/*
388 		 * Generate the tone for the appropriate number of ticks.
389 		 * If the time is zero, turn off sound ourselves.
390 		 */
391 		ticks = HZ * ((arg >> 16) & 0xffff) / 1000;
392 		count = ticks ? (arg & 0xffff) : 0;
393 		if (count)
394 			count = PIT_TICK_RATE / count;
395 		kd_mksound(count, ticks);
396 		break;
397 	}
398 
399 	case KDGKBTYPE:
400 		/*
401 		 * this is naïve.
402 		 */
403 		ucval = KB_101;
404 		ret = put_user(ucval, (char __user *)arg);
405 		break;
406 
407 		/*
408 		 * These cannot be implemented on any machine that implements
409 		 * ioperm() in user level (such as Alpha PCs) or not at all.
410 		 *
411 		 * XXX: you should never use these, just call ioperm directly..
412 		 */
413 #ifdef CONFIG_X86
414 	case KDADDIO:
415 	case KDDELIO:
416 		/*
417 		 * KDADDIO and KDDELIO may be able to add ports beyond what
418 		 * we reject here, but to be safe...
419 		 *
420 		 * These are locked internally via sys_ioperm
421 		 */
422 		if (arg < GPFIRST || arg > GPLAST) {
423 			ret = -EINVAL;
424 			break;
425 		}
426 		ret = sys_ioperm(arg, 1, (cmd == KDADDIO)) ? -ENXIO : 0;
427 		break;
428 
429 	case KDENABIO:
430 	case KDDISABIO:
431 		ret = sys_ioperm(GPFIRST, GPNUM,
432 				  (cmd == KDENABIO)) ? -ENXIO : 0;
433 		break;
434 #endif
435 
436 	/* Linux m68k/i386 interface for setting the keyboard delay/repeat rate */
437 
438 	case KDKBDREP:
439 	{
440 		struct kbd_repeat kbrep;
441 
442 		if (!capable(CAP_SYS_TTY_CONFIG))
443 			return -EPERM;
444 
445 		if (copy_from_user(&kbrep, up, sizeof(struct kbd_repeat))) {
446 			ret =  -EFAULT;
447 			break;
448 		}
449 		ret = kbd_rate(&kbrep);
450 		if (ret)
451 			break;
452 		if (copy_to_user(up, &kbrep, sizeof(struct kbd_repeat)))
453 			ret = -EFAULT;
454 		break;
455 	}
456 
457 	case KDSETMODE:
458 		/*
459 		 * currently, setting the mode from KD_TEXT to KD_GRAPHICS
460 		 * doesn't do a whole lot. i'm not sure if it should do any
461 		 * restoration of modes or what...
462 		 *
463 		 * XXX It should at least call into the driver, fbdev's definitely
464 		 * need to restore their engine state. --BenH
465 		 */
466 		if (!perm)
467 			return -EPERM;
468 		switch (arg) {
469 		case KD_GRAPHICS:
470 			break;
471 		case KD_TEXT0:
472 		case KD_TEXT1:
473 			arg = KD_TEXT;
474 		case KD_TEXT:
475 			break;
476 		default:
477 			ret = -EINVAL;
478 			goto out;
479 		}
480 		/* FIXME: this needs the console lock extending */
481 		if (vc->vc_mode == (unsigned char) arg)
482 			break;
483 		vc->vc_mode = (unsigned char) arg;
484 		if (console != fg_console)
485 			break;
486 		/*
487 		 * explicitly blank/unblank the screen if switching modes
488 		 */
489 		console_lock();
490 		if (arg == KD_TEXT)
491 			do_unblank_screen(1);
492 		else
493 			do_blank_screen(1);
494 		console_unlock();
495 		break;
496 
497 	case KDGETMODE:
498 		uival = vc->vc_mode;
499 		goto setint;
500 
501 	case KDMAPDISP:
502 	case KDUNMAPDISP:
503 		/*
504 		 * these work like a combination of mmap and KDENABIO.
505 		 * this could be easily finished.
506 		 */
507 		ret = -EINVAL;
508 		break;
509 
510 	case KDSKBMODE:
511 		if (!perm)
512 			return -EPERM;
513 		ret = vt_do_kdskbmode(console, arg);
514 		if (ret == 0)
515 			tty_ldisc_flush(tty);
516 		break;
517 
518 	case KDGKBMODE:
519 		uival = vt_do_kdgkbmode(console);
520 		ret = put_user(uival, (int __user *)arg);
521 		break;
522 
523 	/* this could be folded into KDSKBMODE, but for compatibility
524 	   reasons it is not so easy to fold KDGKBMETA into KDGKBMODE */
525 	case KDSKBMETA:
526 		ret = vt_do_kdskbmeta(console, arg);
527 		break;
528 
529 	case KDGKBMETA:
530 		/* FIXME: should review whether this is worth locking */
531 		uival = vt_do_kdgkbmeta(console);
532 	setint:
533 		ret = put_user(uival, (int __user *)arg);
534 		break;
535 
536 	case KDGETKEYCODE:
537 	case KDSETKEYCODE:
538 		if(!capable(CAP_SYS_TTY_CONFIG))
539 			perm = 0;
540 		ret = vt_do_kbkeycode_ioctl(cmd, up, perm);
541 		break;
542 
543 	case KDGKBENT:
544 	case KDSKBENT:
545 		ret = vt_do_kdsk_ioctl(cmd, up, perm, console);
546 		break;
547 
548 	case KDGKBSENT:
549 	case KDSKBSENT:
550 		ret = vt_do_kdgkb_ioctl(cmd, up, perm);
551 		break;
552 
553 	/* Diacritical processing. Handled in keyboard.c as it has
554 	   to operate on the keyboard locks and structures */
555 	case KDGKBDIACR:
556 	case KDGKBDIACRUC:
557 	case KDSKBDIACR:
558 	case KDSKBDIACRUC:
559 		ret = vt_do_diacrit(cmd, up, perm);
560 		break;
561 
562 	/* the ioctls below read/set the flags usually shown in the leds */
563 	/* don't use them - they will go away without warning */
564 	case KDGKBLED:
565 	case KDSKBLED:
566 	case KDGETLED:
567 	case KDSETLED:
568 		ret = vt_do_kdskled(console, cmd, arg, perm);
569 		break;
570 
571 	/*
572 	 * A process can indicate its willingness to accept signals
573 	 * generated by pressing an appropriate key combination.
574 	 * Thus, one can have a daemon that e.g. spawns a new console
575 	 * upon a keypress and then changes to it.
576 	 * See also the kbrequest field of inittab(5).
577 	 */
578 	case KDSIGACCEPT:
579 	{
580 		if (!perm || !capable(CAP_KILL))
581 			return -EPERM;
582 		if (!valid_signal(arg) || arg < 1 || arg == SIGKILL)
583 			ret = -EINVAL;
584 		else {
585 			spin_lock_irq(&vt_spawn_con.lock);
586 			put_pid(vt_spawn_con.pid);
587 			vt_spawn_con.pid = get_pid(task_pid(current));
588 			vt_spawn_con.sig = arg;
589 			spin_unlock_irq(&vt_spawn_con.lock);
590 		}
591 		break;
592 	}
593 
594 	case VT_SETMODE:
595 	{
596 		struct vt_mode tmp;
597 
598 		if (!perm)
599 			return -EPERM;
600 		if (copy_from_user(&tmp, up, sizeof(struct vt_mode))) {
601 			ret = -EFAULT;
602 			goto out;
603 		}
604 		if (tmp.mode != VT_AUTO && tmp.mode != VT_PROCESS) {
605 			ret = -EINVAL;
606 			goto out;
607 		}
608 		console_lock();
609 		vc->vt_mode = tmp;
610 		/* the frsig is ignored, so we set it to 0 */
611 		vc->vt_mode.frsig = 0;
612 		put_pid(vc->vt_pid);
613 		vc->vt_pid = get_pid(task_pid(current));
614 		/* no switch is required -- saw@shade.msu.ru */
615 		vc->vt_newvt = -1;
616 		console_unlock();
617 		break;
618 	}
619 
620 	case VT_GETMODE:
621 	{
622 		struct vt_mode tmp;
623 		int rc;
624 
625 		console_lock();
626 		memcpy(&tmp, &vc->vt_mode, sizeof(struct vt_mode));
627 		console_unlock();
628 
629 		rc = copy_to_user(up, &tmp, sizeof(struct vt_mode));
630 		if (rc)
631 			ret = -EFAULT;
632 		break;
633 	}
634 
635 	/*
636 	 * Returns global vt state. Note that VT 0 is always open, since
637 	 * it's an alias for the current VT, and people can't use it here.
638 	 * We cannot return state for more than 16 VTs, since v_state is short.
639 	 */
640 	case VT_GETSTATE:
641 	{
642 		struct vt_stat __user *vtstat = up;
643 		unsigned short state, mask;
644 
645 		/* Review: FIXME: Console lock ? */
646 		if (put_user(fg_console + 1, &vtstat->v_active))
647 			ret = -EFAULT;
648 		else {
649 			state = 1;	/* /dev/tty0 is always open */
650 			for (i = 0, mask = 2; i < MAX_NR_CONSOLES && mask;
651 							++i, mask <<= 1)
652 				if (VT_IS_IN_USE(i))
653 					state |= mask;
654 			ret = put_user(state, &vtstat->v_state);
655 		}
656 		break;
657 	}
658 
659 	/*
660 	 * Returns the first available (non-opened) console.
661 	 */
662 	case VT_OPENQRY:
663 		/* FIXME: locking ? - but then this is a stupid API */
664 		for (i = 0; i < MAX_NR_CONSOLES; ++i)
665 			if (! VT_IS_IN_USE(i))
666 				break;
667 		uival = i < MAX_NR_CONSOLES ? (i+1) : -1;
668 		goto setint;
669 
670 	/*
671 	 * ioctl(fd, VT_ACTIVATE, num) will cause us to switch to vt # num,
672 	 * with num >= 1 (switches to vt 0, our console, are not allowed, just
673 	 * to preserve sanity).
674 	 */
675 	case VT_ACTIVATE:
676 		if (!perm)
677 			return -EPERM;
678 		if (arg == 0 || arg > MAX_NR_CONSOLES)
679 			ret =  -ENXIO;
680 		else {
681 			arg--;
682 			console_lock();
683 			ret = vc_allocate(arg);
684 			console_unlock();
685 			if (ret)
686 				break;
687 			set_console(arg);
688 		}
689 		break;
690 
691 	case VT_SETACTIVATE:
692 	{
693 		struct vt_setactivate vsa;
694 
695 		if (!perm)
696 			return -EPERM;
697 
698 		if (copy_from_user(&vsa, (struct vt_setactivate __user *)arg,
699 					sizeof(struct vt_setactivate))) {
700 			ret = -EFAULT;
701 			goto out;
702 		}
703 		if (vsa.console == 0 || vsa.console > MAX_NR_CONSOLES)
704 			ret = -ENXIO;
705 		else {
706 			vsa.console--;
707 			console_lock();
708 			ret = vc_allocate(vsa.console);
709 			if (ret == 0) {
710 				struct vc_data *nvc;
711 				/* This is safe providing we don't drop the
712 				   console sem between vc_allocate and
713 				   finishing referencing nvc */
714 				nvc = vc_cons[vsa.console].d;
715 				nvc->vt_mode = vsa.mode;
716 				nvc->vt_mode.frsig = 0;
717 				put_pid(nvc->vt_pid);
718 				nvc->vt_pid = get_pid(task_pid(current));
719 			}
720 			console_unlock();
721 			if (ret)
722 				break;
723 			/* Commence switch and lock */
724 			/* Review set_console locks */
725 			set_console(vsa.console);
726 		}
727 		break;
728 	}
729 
730 	/*
731 	 * wait until the specified VT has been activated
732 	 */
733 	case VT_WAITACTIVE:
734 		if (!perm)
735 			return -EPERM;
736 		if (arg == 0 || arg > MAX_NR_CONSOLES)
737 			ret = -ENXIO;
738 		else
739 			ret = vt_waitactive(arg);
740 		break;
741 
742 	/*
743 	 * If a vt is under process control, the kernel will not switch to it
744 	 * immediately, but postpone the operation until the process calls this
745 	 * ioctl, allowing the switch to complete.
746 	 *
747 	 * According to the X sources this is the behavior:
748 	 *	0:	pending switch-from not OK
749 	 *	1:	pending switch-from OK
750 	 *	2:	completed switch-to OK
751 	 */
752 	case VT_RELDISP:
753 		if (!perm)
754 			return -EPERM;
755 
756 		console_lock();
757 		if (vc->vt_mode.mode != VT_PROCESS) {
758 			console_unlock();
759 			ret = -EINVAL;
760 			break;
761 		}
762 		/*
763 		 * Switching-from response
764 		 */
765 		if (vc->vt_newvt >= 0) {
766 			if (arg == 0)
767 				/*
768 				 * Switch disallowed, so forget we were trying
769 				 * to do it.
770 				 */
771 				vc->vt_newvt = -1;
772 
773 			else {
774 				/*
775 				 * The current vt has been released, so
776 				 * complete the switch.
777 				 */
778 				int newvt;
779 				newvt = vc->vt_newvt;
780 				vc->vt_newvt = -1;
781 				ret = vc_allocate(newvt);
782 				if (ret) {
783 					console_unlock();
784 					break;
785 				}
786 				/*
787 				 * When we actually do the console switch,
788 				 * make sure we are atomic with respect to
789 				 * other console switches..
790 				 */
791 				complete_change_console(vc_cons[newvt].d);
792 			}
793 		} else {
794 			/*
795 			 * Switched-to response
796 			 */
797 			/*
798 			 * If it's just an ACK, ignore it
799 			 */
800 			if (arg != VT_ACKACQ)
801 				ret = -EINVAL;
802 		}
803 		console_unlock();
804 		break;
805 
806 	 /*
807 	  * Disallocate memory associated to VT (but leave VT1)
808 	  */
809 	 case VT_DISALLOCATE:
810 		if (arg > MAX_NR_CONSOLES) {
811 			ret = -ENXIO;
812 			break;
813 		}
814 		if (arg == 0)
815 			vt_disallocate_all();
816 		else
817 			ret = vt_disallocate(--arg);
818 		break;
819 
820 	case VT_RESIZE:
821 	{
822 		struct vt_sizes __user *vtsizes = up;
823 		struct vc_data *vc;
824 
825 		ushort ll,cc;
826 		if (!perm)
827 			return -EPERM;
828 		if (get_user(ll, &vtsizes->v_rows) ||
829 		    get_user(cc, &vtsizes->v_cols))
830 			ret = -EFAULT;
831 		else {
832 			console_lock();
833 			for (i = 0; i < MAX_NR_CONSOLES; i++) {
834 				vc = vc_cons[i].d;
835 
836 				if (vc) {
837 					vc->vc_resize_user = 1;
838 					/* FIXME: review v tty lock */
839 					vc_resize(vc_cons[i].d, cc, ll);
840 				}
841 			}
842 			console_unlock();
843 		}
844 		break;
845 	}
846 
847 	case VT_RESIZEX:
848 	{
849 		struct vt_consize __user *vtconsize = up;
850 		ushort ll,cc,vlin,clin,vcol,ccol;
851 		if (!perm)
852 			return -EPERM;
853 		if (!access_ok(VERIFY_READ, vtconsize,
854 				sizeof(struct vt_consize))) {
855 			ret = -EFAULT;
856 			break;
857 		}
858 		/* FIXME: Should check the copies properly */
859 		__get_user(ll, &vtconsize->v_rows);
860 		__get_user(cc, &vtconsize->v_cols);
861 		__get_user(vlin, &vtconsize->v_vlin);
862 		__get_user(clin, &vtconsize->v_clin);
863 		__get_user(vcol, &vtconsize->v_vcol);
864 		__get_user(ccol, &vtconsize->v_ccol);
865 		vlin = vlin ? vlin : vc->vc_scan_lines;
866 		if (clin) {
867 			if (ll) {
868 				if (ll != vlin/clin) {
869 					/* Parameters don't add up */
870 					ret = -EINVAL;
871 					break;
872 				}
873 			} else
874 				ll = vlin/clin;
875 		}
876 		if (vcol && ccol) {
877 			if (cc) {
878 				if (cc != vcol/ccol) {
879 					ret = -EINVAL;
880 					break;
881 				}
882 			} else
883 				cc = vcol/ccol;
884 		}
885 
886 		if (clin > 32) {
887 			ret =  -EINVAL;
888 			break;
889 		}
890 
891 		for (i = 0; i < MAX_NR_CONSOLES; i++) {
892 			if (!vc_cons[i].d)
893 				continue;
894 			console_lock();
895 			if (vlin)
896 				vc_cons[i].d->vc_scan_lines = vlin;
897 			if (clin)
898 				vc_cons[i].d->vc_font.height = clin;
899 			vc_cons[i].d->vc_resize_user = 1;
900 			vc_resize(vc_cons[i].d, cc, ll);
901 			console_unlock();
902 		}
903 		break;
904 	}
905 
906 	case PIO_FONT: {
907 		if (!perm)
908 			return -EPERM;
909 		op.op = KD_FONT_OP_SET;
910 		op.flags = KD_FONT_FLAG_OLD | KD_FONT_FLAG_DONT_RECALC;	/* Compatibility */
911 		op.width = 8;
912 		op.height = 0;
913 		op.charcount = 256;
914 		op.data = up;
915 		ret = con_font_op(vc_cons[fg_console].d, &op);
916 		break;
917 	}
918 
919 	case GIO_FONT: {
920 		op.op = KD_FONT_OP_GET;
921 		op.flags = KD_FONT_FLAG_OLD;
922 		op.width = 8;
923 		op.height = 32;
924 		op.charcount = 256;
925 		op.data = up;
926 		ret = con_font_op(vc_cons[fg_console].d, &op);
927 		break;
928 	}
929 
930 	case PIO_CMAP:
931                 if (!perm)
932 			ret = -EPERM;
933 		else
934 	                ret = con_set_cmap(up);
935 		break;
936 
937 	case GIO_CMAP:
938                 ret = con_get_cmap(up);
939 		break;
940 
941 	case PIO_FONTX:
942 	case GIO_FONTX:
943 		ret = do_fontx_ioctl(cmd, up, perm, &op);
944 		break;
945 
946 	case PIO_FONTRESET:
947 	{
948 		if (!perm)
949 			return -EPERM;
950 
951 #ifdef BROKEN_GRAPHICS_PROGRAMS
952 		/* With BROKEN_GRAPHICS_PROGRAMS defined, the default
953 		   font is not saved. */
954 		ret = -ENOSYS;
955 		break;
956 #else
957 		{
958 		op.op = KD_FONT_OP_SET_DEFAULT;
959 		op.data = NULL;
960 		ret = con_font_op(vc_cons[fg_console].d, &op);
961 		if (ret)
962 			break;
963 		console_lock();
964 		con_set_default_unimap(vc_cons[fg_console].d);
965 		console_unlock();
966 		break;
967 		}
968 #endif
969 	}
970 
971 	case KDFONTOP: {
972 		if (copy_from_user(&op, up, sizeof(op))) {
973 			ret = -EFAULT;
974 			break;
975 		}
976 		if (!perm && op.op != KD_FONT_OP_GET)
977 			return -EPERM;
978 		ret = con_font_op(vc, &op);
979 		if (ret)
980 			break;
981 		if (copy_to_user(up, &op, sizeof(op)))
982 			ret = -EFAULT;
983 		break;
984 	}
985 
986 	case PIO_SCRNMAP:
987 		if (!perm)
988 			ret = -EPERM;
989 		else
990 			ret = con_set_trans_old(up);
991 		break;
992 
993 	case GIO_SCRNMAP:
994 		ret = con_get_trans_old(up);
995 		break;
996 
997 	case PIO_UNISCRNMAP:
998 		if (!perm)
999 			ret = -EPERM;
1000 		else
1001 			ret = con_set_trans_new(up);
1002 		break;
1003 
1004 	case GIO_UNISCRNMAP:
1005 		ret = con_get_trans_new(up);
1006 		break;
1007 
1008 	case PIO_UNIMAPCLR:
1009 	      { struct unimapinit ui;
1010 		if (!perm)
1011 			return -EPERM;
1012 		ret = copy_from_user(&ui, up, sizeof(struct unimapinit));
1013 		if (ret)
1014 			ret = -EFAULT;
1015 		else
1016 			con_clear_unimap(vc, &ui);
1017 		break;
1018 	      }
1019 
1020 	case PIO_UNIMAP:
1021 	case GIO_UNIMAP:
1022 		ret = do_unimap_ioctl(cmd, up, perm, vc);
1023 		break;
1024 
1025 	case VT_LOCKSWITCH:
1026 		if (!capable(CAP_SYS_TTY_CONFIG))
1027 			return -EPERM;
1028 		vt_dont_switch = 1;
1029 		break;
1030 	case VT_UNLOCKSWITCH:
1031 		if (!capable(CAP_SYS_TTY_CONFIG))
1032 			return -EPERM;
1033 		vt_dont_switch = 0;
1034 		break;
1035 	case VT_GETHIFONTMASK:
1036 		ret = put_user(vc->vc_hi_font_mask,
1037 					(unsigned short __user *)arg);
1038 		break;
1039 	case VT_WAITEVENT:
1040 		ret = vt_event_wait_ioctl((struct vt_event __user *)arg);
1041 		break;
1042 	default:
1043 		ret = -ENOIOCTLCMD;
1044 	}
1045 out:
1046 	return ret;
1047 }
1048 
1049 void reset_vc(struct vc_data *vc)
1050 {
1051 	vc->vc_mode = KD_TEXT;
1052 	vt_reset_unicode(vc->vc_num);
1053 	vc->vt_mode.mode = VT_AUTO;
1054 	vc->vt_mode.waitv = 0;
1055 	vc->vt_mode.relsig = 0;
1056 	vc->vt_mode.acqsig = 0;
1057 	vc->vt_mode.frsig = 0;
1058 	put_pid(vc->vt_pid);
1059 	vc->vt_pid = NULL;
1060 	vc->vt_newvt = -1;
1061 	if (!in_interrupt())    /* Via keyboard.c:SAK() - akpm */
1062 		reset_palette(vc);
1063 }
1064 
1065 void vc_SAK(struct work_struct *work)
1066 {
1067 	struct vc *vc_con =
1068 		container_of(work, struct vc, SAK_work);
1069 	struct vc_data *vc;
1070 	struct tty_struct *tty;
1071 
1072 	console_lock();
1073 	vc = vc_con->d;
1074 	if (vc) {
1075 		/* FIXME: review tty ref counting */
1076 		tty = vc->port.tty;
1077 		/*
1078 		 * SAK should also work in all raw modes and reset
1079 		 * them properly.
1080 		 */
1081 		if (tty)
1082 			__do_SAK(tty);
1083 		reset_vc(vc);
1084 	}
1085 	console_unlock();
1086 }
1087 
1088 #ifdef CONFIG_COMPAT
1089 
1090 struct compat_consolefontdesc {
1091 	unsigned short charcount;       /* characters in font (256 or 512) */
1092 	unsigned short charheight;      /* scan lines per character (1-32) */
1093 	compat_caddr_t chardata;	/* font data in expanded form */
1094 };
1095 
1096 static inline int
1097 compat_fontx_ioctl(int cmd, struct compat_consolefontdesc __user *user_cfd,
1098 			 int perm, struct console_font_op *op)
1099 {
1100 	struct compat_consolefontdesc cfdarg;
1101 	int i;
1102 
1103 	if (copy_from_user(&cfdarg, user_cfd, sizeof(struct compat_consolefontdesc)))
1104 		return -EFAULT;
1105 
1106 	switch (cmd) {
1107 	case PIO_FONTX:
1108 		if (!perm)
1109 			return -EPERM;
1110 		op->op = KD_FONT_OP_SET;
1111 		op->flags = KD_FONT_FLAG_OLD;
1112 		op->width = 8;
1113 		op->height = cfdarg.charheight;
1114 		op->charcount = cfdarg.charcount;
1115 		op->data = compat_ptr(cfdarg.chardata);
1116 		return con_font_op(vc_cons[fg_console].d, op);
1117 	case GIO_FONTX:
1118 		op->op = KD_FONT_OP_GET;
1119 		op->flags = KD_FONT_FLAG_OLD;
1120 		op->width = 8;
1121 		op->height = cfdarg.charheight;
1122 		op->charcount = cfdarg.charcount;
1123 		op->data = compat_ptr(cfdarg.chardata);
1124 		i = con_font_op(vc_cons[fg_console].d, op);
1125 		if (i)
1126 			return i;
1127 		cfdarg.charheight = op->height;
1128 		cfdarg.charcount = op->charcount;
1129 		if (copy_to_user(user_cfd, &cfdarg, sizeof(struct compat_consolefontdesc)))
1130 			return -EFAULT;
1131 		return 0;
1132 	}
1133 	return -EINVAL;
1134 }
1135 
1136 struct compat_console_font_op {
1137 	compat_uint_t op;        /* operation code KD_FONT_OP_* */
1138 	compat_uint_t flags;     /* KD_FONT_FLAG_* */
1139 	compat_uint_t width, height;     /* font size */
1140 	compat_uint_t charcount;
1141 	compat_caddr_t data;    /* font data with height fixed to 32 */
1142 };
1143 
1144 static inline int
1145 compat_kdfontop_ioctl(struct compat_console_font_op __user *fontop,
1146 			 int perm, struct console_font_op *op, struct vc_data *vc)
1147 {
1148 	int i;
1149 
1150 	if (copy_from_user(op, fontop, sizeof(struct compat_console_font_op)))
1151 		return -EFAULT;
1152 	if (!perm && op->op != KD_FONT_OP_GET)
1153 		return -EPERM;
1154 	op->data = compat_ptr(((struct compat_console_font_op *)op)->data);
1155 	i = con_font_op(vc, op);
1156 	if (i)
1157 		return i;
1158 	((struct compat_console_font_op *)op)->data = (unsigned long)op->data;
1159 	if (copy_to_user(fontop, op, sizeof(struct compat_console_font_op)))
1160 		return -EFAULT;
1161 	return 0;
1162 }
1163 
1164 struct compat_unimapdesc {
1165 	unsigned short entry_ct;
1166 	compat_caddr_t entries;
1167 };
1168 
1169 static inline int
1170 compat_unimap_ioctl(unsigned int cmd, struct compat_unimapdesc __user *user_ud,
1171 			 int perm, struct vc_data *vc)
1172 {
1173 	struct compat_unimapdesc tmp;
1174 	struct unipair __user *tmp_entries;
1175 
1176 	if (copy_from_user(&tmp, user_ud, sizeof tmp))
1177 		return -EFAULT;
1178 	tmp_entries = compat_ptr(tmp.entries);
1179 	if (tmp_entries)
1180 		if (!access_ok(VERIFY_WRITE, tmp_entries,
1181 				tmp.entry_ct*sizeof(struct unipair)))
1182 			return -EFAULT;
1183 	switch (cmd) {
1184 	case PIO_UNIMAP:
1185 		if (!perm)
1186 			return -EPERM;
1187 		return con_set_unimap(vc, tmp.entry_ct, tmp_entries);
1188 	case GIO_UNIMAP:
1189 		if (!perm && fg_console != vc->vc_num)
1190 			return -EPERM;
1191 		return con_get_unimap(vc, tmp.entry_ct, &(user_ud->entry_ct), tmp_entries);
1192 	}
1193 	return 0;
1194 }
1195 
1196 long vt_compat_ioctl(struct tty_struct *tty,
1197 	     unsigned int cmd, unsigned long arg)
1198 {
1199 	struct vc_data *vc = tty->driver_data;
1200 	struct console_font_op op;	/* used in multiple places here */
1201 	unsigned int console;
1202 	void __user *up = (void __user *)arg;
1203 	int perm;
1204 	int ret = 0;
1205 
1206 	console = vc->vc_num;
1207 
1208 	if (!vc_cons_allocated(console)) { 	/* impossible? */
1209 		ret = -ENOIOCTLCMD;
1210 		goto out;
1211 	}
1212 
1213 	/*
1214 	 * To have permissions to do most of the vt ioctls, we either have
1215 	 * to be the owner of the tty, or have CAP_SYS_TTY_CONFIG.
1216 	 */
1217 	perm = 0;
1218 	if (current->signal->tty == tty || capable(CAP_SYS_TTY_CONFIG))
1219 		perm = 1;
1220 
1221 	switch (cmd) {
1222 	/*
1223 	 * these need special handlers for incompatible data structures
1224 	 */
1225 	case PIO_FONTX:
1226 	case GIO_FONTX:
1227 		ret = compat_fontx_ioctl(cmd, up, perm, &op);
1228 		break;
1229 
1230 	case KDFONTOP:
1231 		ret = compat_kdfontop_ioctl(up, perm, &op, vc);
1232 		break;
1233 
1234 	case PIO_UNIMAP:
1235 	case GIO_UNIMAP:
1236 		ret = compat_unimap_ioctl(cmd, up, perm, vc);
1237 		break;
1238 
1239 	/*
1240 	 * all these treat 'arg' as an integer
1241 	 */
1242 	case KIOCSOUND:
1243 	case KDMKTONE:
1244 #ifdef CONFIG_X86
1245 	case KDADDIO:
1246 	case KDDELIO:
1247 #endif
1248 	case KDSETMODE:
1249 	case KDMAPDISP:
1250 	case KDUNMAPDISP:
1251 	case KDSKBMODE:
1252 	case KDSKBMETA:
1253 	case KDSKBLED:
1254 	case KDSETLED:
1255 	case KDSIGACCEPT:
1256 	case VT_ACTIVATE:
1257 	case VT_WAITACTIVE:
1258 	case VT_RELDISP:
1259 	case VT_DISALLOCATE:
1260 	case VT_RESIZE:
1261 	case VT_RESIZEX:
1262 		goto fallback;
1263 
1264 	/*
1265 	 * the rest has a compatible data structure behind arg,
1266 	 * but we have to convert it to a proper 64 bit pointer.
1267 	 */
1268 	default:
1269 		arg = (unsigned long)compat_ptr(arg);
1270 		goto fallback;
1271 	}
1272 out:
1273 	return ret;
1274 
1275 fallback:
1276 	return vt_ioctl(tty, cmd, arg);
1277 }
1278 
1279 
1280 #endif /* CONFIG_COMPAT */
1281 
1282 
1283 /*
1284  * Performs the back end of a vt switch. Called under the console
1285  * semaphore.
1286  */
1287 static void complete_change_console(struct vc_data *vc)
1288 {
1289 	unsigned char old_vc_mode;
1290 	int old = fg_console;
1291 
1292 	last_console = fg_console;
1293 
1294 	/*
1295 	 * If we're switching, we could be going from KD_GRAPHICS to
1296 	 * KD_TEXT mode or vice versa, which means we need to blank or
1297 	 * unblank the screen later.
1298 	 */
1299 	old_vc_mode = vc_cons[fg_console].d->vc_mode;
1300 	switch_screen(vc);
1301 
1302 	/*
1303 	 * This can't appear below a successful kill_pid().  If it did,
1304 	 * then the *blank_screen operation could occur while X, having
1305 	 * received acqsig, is waking up on another processor.  This
1306 	 * condition can lead to overlapping accesses to the VGA range
1307 	 * and the framebuffer (causing system lockups).
1308 	 *
1309 	 * To account for this we duplicate this code below only if the
1310 	 * controlling process is gone and we've called reset_vc.
1311 	 */
1312 	if (old_vc_mode != vc->vc_mode) {
1313 		if (vc->vc_mode == KD_TEXT)
1314 			do_unblank_screen(1);
1315 		else
1316 			do_blank_screen(1);
1317 	}
1318 
1319 	/*
1320 	 * If this new console is under process control, send it a signal
1321 	 * telling it that it has acquired. Also check if it has died and
1322 	 * clean up (similar to logic employed in change_console())
1323 	 */
1324 	if (vc->vt_mode.mode == VT_PROCESS) {
1325 		/*
1326 		 * Send the signal as privileged - kill_pid() will
1327 		 * tell us if the process has gone or something else
1328 		 * is awry
1329 		 */
1330 		if (kill_pid(vc->vt_pid, vc->vt_mode.acqsig, 1) != 0) {
1331 		/*
1332 		 * The controlling process has died, so we revert back to
1333 		 * normal operation. In this case, we'll also change back
1334 		 * to KD_TEXT mode. I'm not sure if this is strictly correct
1335 		 * but it saves the agony when the X server dies and the screen
1336 		 * remains blanked due to KD_GRAPHICS! It would be nice to do
1337 		 * this outside of VT_PROCESS but there is no single process
1338 		 * to account for and tracking tty count may be undesirable.
1339 		 */
1340 			reset_vc(vc);
1341 
1342 			if (old_vc_mode != vc->vc_mode) {
1343 				if (vc->vc_mode == KD_TEXT)
1344 					do_unblank_screen(1);
1345 				else
1346 					do_blank_screen(1);
1347 			}
1348 		}
1349 	}
1350 
1351 	/*
1352 	 * Wake anyone waiting for their VT to activate
1353 	 */
1354 	vt_event_post(VT_EVENT_SWITCH, old, vc->vc_num);
1355 	return;
1356 }
1357 
1358 /*
1359  * Performs the front-end of a vt switch
1360  */
1361 void change_console(struct vc_data *new_vc)
1362 {
1363 	struct vc_data *vc;
1364 
1365 	if (!new_vc || new_vc->vc_num == fg_console || vt_dont_switch)
1366 		return;
1367 
1368 	/*
1369 	 * If this vt is in process mode, then we need to handshake with
1370 	 * that process before switching. Essentially, we store where that
1371 	 * vt wants to switch to and wait for it to tell us when it's done
1372 	 * (via VT_RELDISP ioctl).
1373 	 *
1374 	 * We also check to see if the controlling process still exists.
1375 	 * If it doesn't, we reset this vt to auto mode and continue.
1376 	 * This is a cheap way to track process control. The worst thing
1377 	 * that can happen is: we send a signal to a process, it dies, and
1378 	 * the switch gets "lost" waiting for a response; hopefully, the
1379 	 * user will try again, we'll detect the process is gone (unless
1380 	 * the user waits just the right amount of time :-) and revert the
1381 	 * vt to auto control.
1382 	 */
1383 	vc = vc_cons[fg_console].d;
1384 	if (vc->vt_mode.mode == VT_PROCESS) {
1385 		/*
1386 		 * Send the signal as privileged - kill_pid() will
1387 		 * tell us if the process has gone or something else
1388 		 * is awry.
1389 		 *
1390 		 * We need to set vt_newvt *before* sending the signal or we
1391 		 * have a race.
1392 		 */
1393 		vc->vt_newvt = new_vc->vc_num;
1394 		if (kill_pid(vc->vt_pid, vc->vt_mode.relsig, 1) == 0) {
1395 			/*
1396 			 * It worked. Mark the vt to switch to and
1397 			 * return. The process needs to send us a
1398 			 * VT_RELDISP ioctl to complete the switch.
1399 			 */
1400 			return;
1401 		}
1402 
1403 		/*
1404 		 * The controlling process has died, so we revert back to
1405 		 * normal operation. In this case, we'll also change back
1406 		 * to KD_TEXT mode. I'm not sure if this is strictly correct
1407 		 * but it saves the agony when the X server dies and the screen
1408 		 * remains blanked due to KD_GRAPHICS! It would be nice to do
1409 		 * this outside of VT_PROCESS but there is no single process
1410 		 * to account for and tracking tty count may be undesirable.
1411 		 */
1412 		reset_vc(vc);
1413 
1414 		/*
1415 		 * Fall through to normal (VT_AUTO) handling of the switch...
1416 		 */
1417 	}
1418 
1419 	/*
1420 	 * Ignore all switches in KD_GRAPHICS+VT_AUTO mode
1421 	 */
1422 	if (vc->vc_mode == KD_GRAPHICS)
1423 		return;
1424 
1425 	complete_change_console(new_vc);
1426 }
1427 
1428 /* Perform a kernel triggered VT switch for suspend/resume */
1429 
1430 static int disable_vt_switch;
1431 
1432 int vt_move_to_console(unsigned int vt, int alloc)
1433 {
1434 	int prev;
1435 
1436 	console_lock();
1437 	/* Graphics mode - up to X */
1438 	if (disable_vt_switch) {
1439 		console_unlock();
1440 		return 0;
1441 	}
1442 	prev = fg_console;
1443 
1444 	if (alloc && vc_allocate(vt)) {
1445 		/* we can't have a free VC for now. Too bad,
1446 		 * we don't want to mess the screen for now. */
1447 		console_unlock();
1448 		return -ENOSPC;
1449 	}
1450 
1451 	if (set_console(vt)) {
1452 		/*
1453 		 * We're unable to switch to the SUSPEND_CONSOLE.
1454 		 * Let the calling function know so it can decide
1455 		 * what to do.
1456 		 */
1457 		console_unlock();
1458 		return -EIO;
1459 	}
1460 	console_unlock();
1461 	if (vt_waitactive(vt + 1)) {
1462 		pr_debug("Suspend: Can't switch VCs.");
1463 		return -EINTR;
1464 	}
1465 	return prev;
1466 }
1467 
1468 /*
1469  * Normally during a suspend, we allocate a new console and switch to it.
1470  * When we resume, we switch back to the original console.  This switch
1471  * can be slow, so on systems where the framebuffer can handle restoration
1472  * of video registers anyways, there's little point in doing the console
1473  * switch.  This function allows you to disable it by passing it '0'.
1474  */
1475 void pm_set_vt_switch(int do_switch)
1476 {
1477 	console_lock();
1478 	disable_vt_switch = !do_switch;
1479 	console_unlock();
1480 }
1481 EXPORT_SYMBOL(pm_set_vt_switch);
1482