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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Provide access to virtual console memory.
4 * /dev/vcs: the screen as it is being viewed right now (possibly scrolled)
5 * /dev/vcsN: the screen of /dev/ttyN (1 <= N <= 63)
6 * [minor: N]
7 *
8 * /dev/vcsaN: idem, but including attributes, and prefixed with
9 * the 4 bytes lines,columns,x,y (as screendump used to give).
10 * Attribute/character pair is in native endianity.
11 * [minor: N+128]
12 *
13 * /dev/vcsuN: similar to /dev/vcsaN but using 4-byte unicode values
14 * instead of 1-byte screen glyph values.
15 * [minor: N+64]
16 *
17 * /dev/vcsuaN: same idea as /dev/vcsaN for unicode (not yet implemented).
18 *
19 * This replaces screendump and part of selection, so that the system
20 * administrator can control access using file system permissions.
21 *
22 * aeb@cwi.nl - efter Friedas begravelse - 950211
23 *
24 * machek@k332.feld.cvut.cz - modified not to send characters to wrong console
25 * - fixed some fatal off-by-one bugs (0-- no longer == -1 -> looping and looping and looping...)
26 * - making it shorter - scr_readw are macros which expand in PRETTY long code
27 */
28
29#include <linux/kernel.h>
30#include <linux/major.h>
31#include <linux/errno.h>
32#include <linux/export.h>
33#include <linux/tty.h>
34#include <linux/interrupt.h>
35#include <linux/mm.h>
36#include <linux/init.h>
37#include <linux/vt_kern.h>
38#include <linux/selection.h>
39#include <linux/kbd_kern.h>
40#include <linux/console.h>
41#include <linux/device.h>
42#include <linux/sched.h>
43#include <linux/fs.h>
44#include <linux/poll.h>
45#include <linux/signal.h>
46#include <linux/slab.h>
47#include <linux/notifier.h>
48
49#include <linux/uaccess.h>
50#include <asm/byteorder.h>
51#include <asm/unaligned.h>
52
53#define HEADER_SIZE 4u
54#define CON_BUF_SIZE (CONFIG_BASE_SMALL ? 256 : PAGE_SIZE)
55
56/*
57 * Our minor space:
58 *
59 * 0 ... 63 glyph mode without attributes
60 * 64 ... 127 unicode mode without attributes
61 * 128 ... 191 glyph mode with attributes
62 * 192 ... 255 unused (reserved for unicode with attributes)
63 *
64 * This relies on MAX_NR_CONSOLES being <= 63, meaning 63 actual consoles
65 * with minors 0, 64, 128 and 192 being proxies for the foreground console.
66 */
67#if MAX_NR_CONSOLES > 63
68#warning "/dev/vcs* devices may not accommodate more than 63 consoles"
69#endif
70
71#define console(inode) (iminor(inode) & 63)
72#define use_unicode(inode) (iminor(inode) & 64)
73#define use_attributes(inode) (iminor(inode) & 128)
74
75
76struct vcs_poll_data {
77 struct notifier_block notifier;
78 unsigned int cons_num;
79 int event;
80 wait_queue_head_t waitq;
81 struct fasync_struct *fasync;
82};
83
84static int
85vcs_notifier(struct notifier_block *nb, unsigned long code, void *_param)
86{
87 struct vt_notifier_param *param = _param;
88 struct vc_data *vc = param->vc;
89 struct vcs_poll_data *poll =
90 container_of(nb, struct vcs_poll_data, notifier);
91 int currcons = poll->cons_num;
92 int fa_band;
93
94 switch (code) {
95 case VT_UPDATE:
96 fa_band = POLL_PRI;
97 break;
98 case VT_DEALLOCATE:
99 fa_band = POLL_HUP;
100 break;
101 default:
102 return NOTIFY_DONE;
103 }
104
105 if (currcons == 0)
106 currcons = fg_console;
107 else
108 currcons--;
109 if (currcons != vc->vc_num)
110 return NOTIFY_DONE;
111
112 poll->event = code;
113 wake_up_interruptible(&poll->waitq);
114 kill_fasync(&poll->fasync, SIGIO, fa_band);
115 return NOTIFY_OK;
116}
117
118static void
119vcs_poll_data_free(struct vcs_poll_data *poll)
120{
121 unregister_vt_notifier(&poll->notifier);
122 kfree(poll);
123}
124
125static struct vcs_poll_data *
126vcs_poll_data_get(struct file *file)
127{
128 struct vcs_poll_data *poll = file->private_data, *kill = NULL;
129
130 if (poll)
131 return poll;
132
133 poll = kzalloc(sizeof(*poll), GFP_KERNEL);
134 if (!poll)
135 return NULL;
136 poll->cons_num = console(file_inode(file));
137 init_waitqueue_head(&poll->waitq);
138 poll->notifier.notifier_call = vcs_notifier;
139 /*
140 * In order not to lose any update event, we must pretend one might
141 * have occurred before we have a chance to register our notifier.
142 * This is also how user space has come to detect which kernels
143 * support POLLPRI on /dev/vcs* devices i.e. using poll() with
144 * POLLPRI and a zero timeout.
145 */
146 poll->event = VT_UPDATE;
147
148 if (register_vt_notifier(&poll->notifier) != 0) {
149 kfree(poll);
150 return NULL;
151 }
152
153 /*
154 * This code may be called either through ->poll() or ->fasync().
155 * If we have two threads using the same file descriptor, they could
156 * both enter this function, both notice that the structure hasn't
157 * been allocated yet and go ahead allocating it in parallel, but
158 * only one of them must survive and be shared otherwise we'd leak
159 * memory with a dangling notifier callback.
160 */
161 spin_lock(&file->f_lock);
162 if (!file->private_data) {
163 file->private_data = poll;
164 } else {
165 /* someone else raced ahead of us */
166 kill = poll;
167 poll = file->private_data;
168 }
169 spin_unlock(&file->f_lock);
170 if (kill)
171 vcs_poll_data_free(kill);
172
173 return poll;
174}
175
176/**
177 * vcs_vc - return VC for @inode
178 * @inode: inode for which to return a VC
179 * @viewed: returns whether this console is currently foreground (viewed)
180 *
181 * Must be called with console_lock.
182 */
183static struct vc_data *vcs_vc(struct inode *inode, bool *viewed)
184{
185 unsigned int currcons = console(inode);
186
187 WARN_CONSOLE_UNLOCKED();
188
189 if (currcons == 0) {
190 currcons = fg_console;
191 if (viewed)
192 *viewed = true;
193 } else {
194 currcons--;
195 if (viewed)
196 *viewed = false;
197 }
198 return vc_cons[currcons].d;
199}
200
201/**
202 * vcs_size - return size for a VC in @vc
203 * @vc: which VC
204 * @attr: does it use attributes?
205 * @unicode: is it unicode?
206 *
207 * Must be called with console_lock.
208 */
209static int vcs_size(const struct vc_data *vc, bool attr, bool unicode)
210{
211 int size;
212
213 WARN_CONSOLE_UNLOCKED();
214
215 size = vc->vc_rows * vc->vc_cols;
216
217 if (attr) {
218 if (unicode)
219 return -EOPNOTSUPP;
220
221 size = 2 * size + HEADER_SIZE;
222 } else if (unicode)
223 size *= 4;
224
225 return size;
226}
227
228static loff_t vcs_lseek(struct file *file, loff_t offset, int orig)
229{
230 struct inode *inode = file_inode(file);
231 struct vc_data *vc;
232 int size;
233
234 console_lock();
235 vc = vcs_vc(inode, NULL);
236 if (!vc) {
237 console_unlock();
238 return -ENXIO;
239 }
240
241 size = vcs_size(vc, use_attributes(inode), use_unicode(inode));
242 console_unlock();
243 if (size < 0)
244 return size;
245 return fixed_size_llseek(file, offset, orig, size);
246}
247
248static int vcs_read_buf_uni(struct vc_data *vc, char *con_buf,
249 unsigned int pos, unsigned int count, bool viewed)
250{
251 unsigned int nr, row, col, maxcol = vc->vc_cols;
252 int ret;
253
254 ret = vc_uniscr_check(vc);
255 if (ret)
256 return ret;
257
258 pos /= 4;
259 row = pos / maxcol;
260 col = pos % maxcol;
261 nr = maxcol - col;
262 do {
263 if (nr > count / 4)
264 nr = count / 4;
265 vc_uniscr_copy_line(vc, con_buf, viewed, row, col, nr);
266 con_buf += nr * 4;
267 count -= nr * 4;
268 row++;
269 col = 0;
270 nr = maxcol;
271 } while (count);
272
273 return 0;
274}
275
276static void vcs_read_buf_noattr(const struct vc_data *vc, char *con_buf,
277 unsigned int pos, unsigned int count, bool viewed)
278{
279 u16 *org;
280 unsigned int col, maxcol = vc->vc_cols;
281
282 org = screen_pos(vc, pos, viewed);
283 col = pos % maxcol;
284 pos += maxcol - col;
285
286 while (count-- > 0) {
287 *con_buf++ = (vcs_scr_readw(vc, org++) & 0xff);
288 if (++col == maxcol) {
289 org = screen_pos(vc, pos, viewed);
290 col = 0;
291 pos += maxcol;
292 }
293 }
294}
295
296static unsigned int vcs_read_buf(const struct vc_data *vc, char *con_buf,
297 unsigned int pos, unsigned int count, bool viewed,
298 unsigned int *skip)
299{
300 u16 *org, *con_buf16;
301 unsigned int col, maxcol = vc->vc_cols;
302 unsigned int filled = count;
303
304 if (pos < HEADER_SIZE) {
305 /* clamp header values if they don't fit */
306 con_buf[0] = min(vc->vc_rows, 0xFFu);
307 con_buf[1] = min(vc->vc_cols, 0xFFu);
308 getconsxy(vc, con_buf + 2);
309
310 *skip += pos;
311 count += pos;
312 if (count > CON_BUF_SIZE) {
313 count = CON_BUF_SIZE;
314 filled = count - pos;
315 }
316
317 /* Advance state pointers and move on. */
318 count -= min(HEADER_SIZE, count);
319 pos = HEADER_SIZE;
320 con_buf += HEADER_SIZE;
321 /* If count >= 0, then pos is even... */
322 } else if (pos & 1) {
323 /*
324 * Skip first byte for output if start address is odd. Update
325 * region sizes up/down depending on free space in buffer.
326 */
327 (*skip)++;
328 if (count < CON_BUF_SIZE)
329 count++;
330 else
331 filled--;
332 }
333
334 if (!count)
335 return filled;
336
337 pos -= HEADER_SIZE;
338 pos /= 2;
339 col = pos % maxcol;
340
341 org = screen_pos(vc, pos, viewed);
342 pos += maxcol - col;
343
344 /*
345 * Buffer has even length, so we can always copy character + attribute.
346 * We do not copy last byte to userspace if count is odd.
347 */
348 count = (count + 1) / 2;
349 con_buf16 = (u16 *)con_buf;
350
351 while (count) {
352 *con_buf16++ = vcs_scr_readw(vc, org++);
353 count--;
354 if (++col == maxcol) {
355 org = screen_pos(vc, pos, viewed);
356 col = 0;
357 pos += maxcol;
358 }
359 }
360
361 return filled;
362}
363
364static ssize_t
365vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
366{
367 struct inode *inode = file_inode(file);
368 struct vc_data *vc;
369 struct vcs_poll_data *poll;
370 unsigned int read;
371 ssize_t ret;
372 char *con_buf;
373 loff_t pos;
374 bool viewed, attr, uni_mode;
375
376 con_buf = (char *) __get_free_page(GFP_KERNEL);
377 if (!con_buf)
378 return -ENOMEM;
379
380 pos = *ppos;
381
382 /* Select the proper current console and verify
383 * sanity of the situation under the console lock.
384 */
385 console_lock();
386
387 uni_mode = use_unicode(inode);
388 attr = use_attributes(inode);
389
390 ret = -EINVAL;
391 if (pos < 0)
392 goto unlock_out;
393 /* we enforce 32-bit alignment for pos and count in unicode mode */
394 if (uni_mode && (pos | count) & 3)
395 goto unlock_out;
396
397 poll = file->private_data;
398 if (count && poll)
399 poll->event = 0;
400 read = 0;
401 ret = 0;
402 while (count) {
403 unsigned int this_round, skip = 0;
404 int size;
405
406 vc = vcs_vc(inode, &viewed);
407 if (!vc) {
408 ret = -ENXIO;
409 break;
410 }
411
412 /* Check whether we are above size each round,
413 * as copy_to_user at the end of this loop
414 * could sleep.
415 */
416 size = vcs_size(vc, attr, uni_mode);
417 if (size < 0) {
418 ret = size;
419 break;
420 }
421 if (pos >= size)
422 break;
423 if (count > size - pos)
424 count = size - pos;
425
426 this_round = count;
427 if (this_round > CON_BUF_SIZE)
428 this_round = CON_BUF_SIZE;
429
430 /* Perform the whole read into the local con_buf.
431 * Then we can drop the console spinlock and safely
432 * attempt to move it to userspace.
433 */
434
435 if (uni_mode) {
436 ret = vcs_read_buf_uni(vc, con_buf, pos, this_round,
437 viewed);
438 if (ret)
439 break;
440 } else if (!attr) {
441 vcs_read_buf_noattr(vc, con_buf, pos, this_round,
442 viewed);
443 } else {
444 this_round = vcs_read_buf(vc, con_buf, pos, this_round,
445 viewed, &skip);
446 }
447
448 /* Finally, release the console semaphore while we push
449 * all the data to userspace from our temporary buffer.
450 *
451 * AKPM: Even though it's a semaphore, we should drop it because
452 * the pagefault handling code may want to call printk().
453 */
454
455 console_unlock();
456 ret = copy_to_user(buf, con_buf + skip, this_round);
457 console_lock();
458
459 if (ret) {
460 read += this_round - ret;
461 ret = -EFAULT;
462 break;
463 }
464 buf += this_round;
465 pos += this_round;
466 read += this_round;
467 count -= this_round;
468 }
469 *ppos += read;
470 if (read)
471 ret = read;
472unlock_out:
473 console_unlock();
474 free_page((unsigned long) con_buf);
475 return ret;
476}
477
478static u16 *vcs_write_buf_noattr(struct vc_data *vc, const char *con_buf,
479 unsigned int pos, unsigned int count, bool viewed, u16 **org0)
480{
481 u16 *org;
482 unsigned int col, maxcol = vc->vc_cols;
483
484 *org0 = org = screen_pos(vc, pos, viewed);
485 col = pos % maxcol;
486 pos += maxcol - col;
487
488 while (count > 0) {
489 unsigned char c = *con_buf++;
490
491 count--;
492 vcs_scr_writew(vc,
493 (vcs_scr_readw(vc, org) & 0xff00) | c, org);
494 org++;
495 if (++col == maxcol) {
496 org = screen_pos(vc, pos, viewed);
497 col = 0;
498 pos += maxcol;
499 }
500 }
501
502 return org;
503}
504
505/*
506 * Compilers (gcc 10) are unable to optimize the swap in cpu_to_le16. So do it
507 * the poor man way.
508 */
509static inline u16 vc_compile_le16(u8 hi, u8 lo)
510{
511#ifdef __BIG_ENDIAN
512 return (lo << 8u) | hi;
513#else
514 return (hi << 8u) | lo;
515#endif
516}
517
518static u16 *vcs_write_buf(struct vc_data *vc, const char *con_buf,
519 unsigned int pos, unsigned int count, bool viewed, u16 **org0)
520{
521 u16 *org;
522 unsigned int col, maxcol = vc->vc_cols;
523 unsigned char c;
524
525 /* header */
526 if (pos < HEADER_SIZE) {
527 char header[HEADER_SIZE];
528
529 getconsxy(vc, header + 2);
530 while (pos < HEADER_SIZE && count > 0) {
531 count--;
532 header[pos++] = *con_buf++;
533 }
534 if (!viewed)
535 putconsxy(vc, header + 2);
536 }
537
538 if (!count)
539 return NULL;
540
541 pos -= HEADER_SIZE;
542 col = (pos/2) % maxcol;
543
544 *org0 = org = screen_pos(vc, pos/2, viewed);
545
546 /* odd pos -- the first single character */
547 if (pos & 1) {
548 count--;
549 c = *con_buf++;
550 vcs_scr_writew(vc, vc_compile_le16(c, vcs_scr_readw(vc, org)),
551 org);
552 org++;
553 pos++;
554 if (++col == maxcol) {
555 org = screen_pos(vc, pos/2, viewed);
556 col = 0;
557 }
558 }
559
560 pos /= 2;
561 pos += maxcol - col;
562
563 /* even pos -- handle attr+character pairs */
564 while (count > 1) {
565 unsigned short w;
566
567 w = get_unaligned(((unsigned short *)con_buf));
568 vcs_scr_writew(vc, w, org++);
569 con_buf += 2;
570 count -= 2;
571 if (++col == maxcol) {
572 org = screen_pos(vc, pos, viewed);
573 col = 0;
574 pos += maxcol;
575 }
576 }
577
578 if (!count)
579 return org;
580
581 /* odd pos -- the remaining character */
582 c = *con_buf++;
583 vcs_scr_writew(vc, vc_compile_le16(vcs_scr_readw(vc, org) >> 8, c),
584 org);
585
586 return org;
587}
588
589static ssize_t
590vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
591{
592 struct inode *inode = file_inode(file);
593 struct vc_data *vc;
594 char *con_buf;
595 u16 *org0, *org;
596 unsigned int written;
597 int size;
598 ssize_t ret;
599 loff_t pos;
600 bool viewed, attr;
601
602 if (use_unicode(inode))
603 return -EOPNOTSUPP;
604
605 con_buf = (char *) __get_free_page(GFP_KERNEL);
606 if (!con_buf)
607 return -ENOMEM;
608
609 pos = *ppos;
610
611 /* Select the proper current console and verify
612 * sanity of the situation under the console lock.
613 */
614 console_lock();
615
616 attr = use_attributes(inode);
617 ret = -ENXIO;
618 vc = vcs_vc(inode, &viewed);
619 if (!vc)
620 goto unlock_out;
621
622 size = vcs_size(vc, attr, false);
623 if (size < 0) {
624 ret = size;
625 goto unlock_out;
626 }
627 ret = -EINVAL;
628 if (pos < 0 || pos > size)
629 goto unlock_out;
630 if (count > size - pos)
631 count = size - pos;
632 written = 0;
633 while (count) {
634 unsigned int this_round = count;
635
636 if (this_round > CON_BUF_SIZE)
637 this_round = CON_BUF_SIZE;
638
639 /* Temporarily drop the console lock so that we can read
640 * in the write data from userspace safely.
641 */
642 console_unlock();
643 ret = copy_from_user(con_buf, buf, this_round);
644 console_lock();
645
646 if (ret) {
647 this_round -= ret;
648 if (!this_round) {
649 /* Abort loop if no data were copied. Otherwise
650 * fail with -EFAULT.
651 */
652 if (written)
653 break;
654 ret = -EFAULT;
655 goto unlock_out;
656 }
657 }
658
659 /* The vc might have been freed or vcs_size might have changed
660 * while we slept to grab the user buffer, so recheck.
661 * Return data written up to now on failure.
662 */
663 vc = vcs_vc(inode, &viewed);
664 if (!vc) {
665 if (written)
666 break;
667 ret = -ENXIO;
668 goto unlock_out;
669 }
670 size = vcs_size(vc, attr, false);
671 if (size < 0) {
672 if (written)
673 break;
674 ret = size;
675 goto unlock_out;
676 }
677 if (pos >= size)
678 break;
679 if (this_round > size - pos)
680 this_round = size - pos;
681
682 /* OK, now actually push the write to the console
683 * under the lock using the local kernel buffer.
684 */
685
686 if (attr)
687 org = vcs_write_buf(vc, con_buf, pos, this_round,
688 viewed, &org0);
689 else
690 org = vcs_write_buf_noattr(vc, con_buf, pos, this_round,
691 viewed, &org0);
692
693 count -= this_round;
694 written += this_round;
695 buf += this_round;
696 pos += this_round;
697 if (org)
698 update_region(vc, (unsigned long)(org0), org - org0);
699 }
700 *ppos += written;
701 ret = written;
702 if (written)
703 vcs_scr_updated(vc);
704
705unlock_out:
706 console_unlock();
707 free_page((unsigned long) con_buf);
708 return ret;
709}
710
711static __poll_t
712vcs_poll(struct file *file, poll_table *wait)
713{
714 struct vcs_poll_data *poll = vcs_poll_data_get(file);
715 __poll_t ret = DEFAULT_POLLMASK|EPOLLERR;
716
717 if (poll) {
718 poll_wait(file, &poll->waitq, wait);
719 switch (poll->event) {
720 case VT_UPDATE:
721 ret = DEFAULT_POLLMASK|EPOLLPRI;
722 break;
723 case VT_DEALLOCATE:
724 ret = DEFAULT_POLLMASK|EPOLLHUP|EPOLLERR;
725 break;
726 case 0:
727 ret = DEFAULT_POLLMASK;
728 break;
729 }
730 }
731 return ret;
732}
733
734static int
735vcs_fasync(int fd, struct file *file, int on)
736{
737 struct vcs_poll_data *poll = file->private_data;
738
739 if (!poll) {
740 /* don't allocate anything if all we want is disable fasync */
741 if (!on)
742 return 0;
743 poll = vcs_poll_data_get(file);
744 if (!poll)
745 return -ENOMEM;
746 }
747
748 return fasync_helper(fd, file, on, &poll->fasync);
749}
750
751static int
752vcs_open(struct inode *inode, struct file *filp)
753{
754 unsigned int currcons = console(inode);
755 bool attr = use_attributes(inode);
756 bool uni_mode = use_unicode(inode);
757 int ret = 0;
758
759 /* we currently don't support attributes in unicode mode */
760 if (attr && uni_mode)
761 return -EOPNOTSUPP;
762
763 console_lock();
764 if(currcons && !vc_cons_allocated(currcons-1))
765 ret = -ENXIO;
766 console_unlock();
767 return ret;
768}
769
770static int vcs_release(struct inode *inode, struct file *file)
771{
772 struct vcs_poll_data *poll = file->private_data;
773
774 if (poll)
775 vcs_poll_data_free(poll);
776 return 0;
777}
778
779static const struct file_operations vcs_fops = {
780 .llseek = vcs_lseek,
781 .read = vcs_read,
782 .write = vcs_write,
783 .poll = vcs_poll,
784 .fasync = vcs_fasync,
785 .open = vcs_open,
786 .release = vcs_release,
787};
788
789static const struct class vc_class = {
790 .name = "vc",
791};
792
793void vcs_make_sysfs(int index)
794{
795 device_create(&vc_class, NULL, MKDEV(VCS_MAJOR, index + 1), NULL, "vcs%u", index + 1);
796 device_create(&vc_class, NULL, MKDEV(VCS_MAJOR, index + 65), NULL, "vcsu%u", index + 1);
797 device_create(&vc_class, NULL, MKDEV(VCS_MAJOR, index + 129), NULL, "vcsa%u", index + 1);
798}
799
800void vcs_remove_sysfs(int index)
801{
802 device_destroy(&vc_class, MKDEV(VCS_MAJOR, index + 1));
803 device_destroy(&vc_class, MKDEV(VCS_MAJOR, index + 65));
804 device_destroy(&vc_class, MKDEV(VCS_MAJOR, index + 129));
805}
806
807int __init vcs_init(void)
808{
809 unsigned int i;
810
811 if (register_chrdev(VCS_MAJOR, "vcs", &vcs_fops))
812 panic("unable to get major %d for vcs device", VCS_MAJOR);
813 if (class_register(&vc_class))
814 panic("unable to create vc_class");
815
816 device_create(&vc_class, NULL, MKDEV(VCS_MAJOR, 0), NULL, "vcs");
817 device_create(&vc_class, NULL, MKDEV(VCS_MAJOR, 64), NULL, "vcsu");
818 device_create(&vc_class, NULL, MKDEV(VCS_MAJOR, 128), NULL, "vcsa");
819 for (i = 0; i < MIN_NR_CONSOLES; i++)
820 vcs_make_sysfs(i);
821 return 0;
822}
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Provide access to virtual console memory.
4 * /dev/vcs: the screen as it is being viewed right now (possibly scrolled)
5 * /dev/vcsN: the screen of /dev/ttyN (1 <= N <= 63)
6 * [minor: N]
7 *
8 * /dev/vcsaN: idem, but including attributes, and prefixed with
9 * the 4 bytes lines,columns,x,y (as screendump used to give).
10 * Attribute/character pair is in native endianity.
11 * [minor: N+128]
12 *
13 * /dev/vcsuN: similar to /dev/vcsaN but using 4-byte unicode values
14 * instead of 1-byte screen glyph values.
15 * [minor: N+64]
16 *
17 * /dev/vcsuaN: same idea as /dev/vcsaN for unicode (not yet implemented).
18 *
19 * This replaces screendump and part of selection, so that the system
20 * administrator can control access using file system permissions.
21 *
22 * aeb@cwi.nl - efter Friedas begravelse - 950211
23 *
24 * machek@k332.feld.cvut.cz - modified not to send characters to wrong console
25 * - fixed some fatal off-by-one bugs (0-- no longer == -1 -> looping and looping and looping...)
26 * - making it shorter - scr_readw are macros which expand in PRETTY long code
27 */
28
29#include <linux/kernel.h>
30#include <linux/major.h>
31#include <linux/errno.h>
32#include <linux/export.h>
33#include <linux/tty.h>
34#include <linux/interrupt.h>
35#include <linux/mm.h>
36#include <linux/init.h>
37#include <linux/vt_kern.h>
38#include <linux/selection.h>
39#include <linux/kbd_kern.h>
40#include <linux/console.h>
41#include <linux/device.h>
42#include <linux/sched.h>
43#include <linux/fs.h>
44#include <linux/poll.h>
45#include <linux/signal.h>
46#include <linux/slab.h>
47#include <linux/notifier.h>
48
49#include <linux/uaccess.h>
50#include <asm/byteorder.h>
51#include <asm/unaligned.h>
52
53#undef attr
54#undef org
55#undef addr
56#define HEADER_SIZE 4
57
58#define CON_BUF_SIZE (CONFIG_BASE_SMALL ? 256 : PAGE_SIZE)
59
60/*
61 * Our minor space:
62 *
63 * 0 ... 63 glyph mode without attributes
64 * 64 ... 127 unicode mode without attributes
65 * 128 ... 191 glyph mode with attributes
66 * 192 ... 255 unused (reserved for unicode with attributes)
67 *
68 * This relies on MAX_NR_CONSOLES being <= 63, meaning 63 actual consoles
69 * with minors 0, 64, 128 and 192 being proxies for the foreground console.
70 */
71#if MAX_NR_CONSOLES > 63
72#warning "/dev/vcs* devices may not accommodate more than 63 consoles"
73#endif
74
75#define console(inode) (iminor(inode) & 63)
76#define use_unicode(inode) (iminor(inode) & 64)
77#define use_attributes(inode) (iminor(inode) & 128)
78
79
80struct vcs_poll_data {
81 struct notifier_block notifier;
82 unsigned int cons_num;
83 int event;
84 wait_queue_head_t waitq;
85 struct fasync_struct *fasync;
86};
87
88static int
89vcs_notifier(struct notifier_block *nb, unsigned long code, void *_param)
90{
91 struct vt_notifier_param *param = _param;
92 struct vc_data *vc = param->vc;
93 struct vcs_poll_data *poll =
94 container_of(nb, struct vcs_poll_data, notifier);
95 int currcons = poll->cons_num;
96 int fa_band;
97
98 switch (code) {
99 case VT_UPDATE:
100 fa_band = POLL_PRI;
101 break;
102 case VT_DEALLOCATE:
103 fa_band = POLL_HUP;
104 break;
105 default:
106 return NOTIFY_DONE;
107 }
108
109 if (currcons == 0)
110 currcons = fg_console;
111 else
112 currcons--;
113 if (currcons != vc->vc_num)
114 return NOTIFY_DONE;
115
116 poll->event = code;
117 wake_up_interruptible(&poll->waitq);
118 kill_fasync(&poll->fasync, SIGIO, fa_band);
119 return NOTIFY_OK;
120}
121
122static void
123vcs_poll_data_free(struct vcs_poll_data *poll)
124{
125 unregister_vt_notifier(&poll->notifier);
126 kfree(poll);
127}
128
129static struct vcs_poll_data *
130vcs_poll_data_get(struct file *file)
131{
132 struct vcs_poll_data *poll = file->private_data, *kill = NULL;
133
134 if (poll)
135 return poll;
136
137 poll = kzalloc(sizeof(*poll), GFP_KERNEL);
138 if (!poll)
139 return NULL;
140 poll->cons_num = console(file_inode(file));
141 init_waitqueue_head(&poll->waitq);
142 poll->notifier.notifier_call = vcs_notifier;
143 /*
144 * In order not to lose any update event, we must pretend one might
145 * have occurred before we have a chance to register our notifier.
146 * This is also how user space has come to detect which kernels
147 * support POLLPRI on /dev/vcs* devices i.e. using poll() with
148 * POLLPRI and a zero timeout.
149 */
150 poll->event = VT_UPDATE;
151
152 if (register_vt_notifier(&poll->notifier) != 0) {
153 kfree(poll);
154 return NULL;
155 }
156
157 /*
158 * This code may be called either through ->poll() or ->fasync().
159 * If we have two threads using the same file descriptor, they could
160 * both enter this function, both notice that the structure hasn't
161 * been allocated yet and go ahead allocating it in parallel, but
162 * only one of them must survive and be shared otherwise we'd leak
163 * memory with a dangling notifier callback.
164 */
165 spin_lock(&file->f_lock);
166 if (!file->private_data) {
167 file->private_data = poll;
168 } else {
169 /* someone else raced ahead of us */
170 kill = poll;
171 poll = file->private_data;
172 }
173 spin_unlock(&file->f_lock);
174 if (kill)
175 vcs_poll_data_free(kill);
176
177 return poll;
178}
179
180/*
181 * Returns VC for inode.
182 * Must be called with console_lock.
183 */
184static struct vc_data*
185vcs_vc(struct inode *inode, int *viewed)
186{
187 unsigned int currcons = console(inode);
188
189 WARN_CONSOLE_UNLOCKED();
190
191 if (currcons == 0) {
192 currcons = fg_console;
193 if (viewed)
194 *viewed = 1;
195 } else {
196 currcons--;
197 if (viewed)
198 *viewed = 0;
199 }
200 return vc_cons[currcons].d;
201}
202
203/*
204 * Returns size for VC carried by inode.
205 * Must be called with console_lock.
206 */
207static int
208vcs_size(struct inode *inode)
209{
210 int size;
211 struct vc_data *vc;
212
213 WARN_CONSOLE_UNLOCKED();
214
215 vc = vcs_vc(inode, NULL);
216 if (!vc)
217 return -ENXIO;
218
219 size = vc->vc_rows * vc->vc_cols;
220
221 if (use_attributes(inode)) {
222 if (use_unicode(inode))
223 return -EOPNOTSUPP;
224 size = 2*size + HEADER_SIZE;
225 } else if (use_unicode(inode))
226 size *= 4;
227 return size;
228}
229
230static loff_t vcs_lseek(struct file *file, loff_t offset, int orig)
231{
232 int size;
233
234 console_lock();
235 size = vcs_size(file_inode(file));
236 console_unlock();
237 if (size < 0)
238 return size;
239 return fixed_size_llseek(file, offset, orig, size);
240}
241
242
243static ssize_t
244vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
245{
246 struct inode *inode = file_inode(file);
247 struct vc_data *vc;
248 struct vcs_poll_data *poll;
249 long pos, read;
250 int attr, uni_mode, row, col, maxcol, viewed;
251 unsigned short *org = NULL;
252 ssize_t ret;
253 char *con_buf;
254
255 con_buf = (char *) __get_free_page(GFP_KERNEL);
256 if (!con_buf)
257 return -ENOMEM;
258
259 pos = *ppos;
260
261 /* Select the proper current console and verify
262 * sanity of the situation under the console lock.
263 */
264 console_lock();
265
266 uni_mode = use_unicode(inode);
267 attr = use_attributes(inode);
268 ret = -ENXIO;
269 vc = vcs_vc(inode, &viewed);
270 if (!vc)
271 goto unlock_out;
272
273 ret = -EINVAL;
274 if (pos < 0)
275 goto unlock_out;
276 /* we enforce 32-bit alignment for pos and count in unicode mode */
277 if (uni_mode && (pos | count) & 3)
278 goto unlock_out;
279
280 poll = file->private_data;
281 if (count && poll)
282 poll->event = 0;
283 read = 0;
284 ret = 0;
285 while (count) {
286 char *con_buf0, *con_buf_start;
287 long this_round, size;
288 ssize_t orig_count;
289 long p = pos;
290
291 /* Check whether we are above size each round,
292 * as copy_to_user at the end of this loop
293 * could sleep.
294 */
295 size = vcs_size(inode);
296 if (size < 0) {
297 if (read)
298 break;
299 ret = size;
300 goto unlock_out;
301 }
302 if (pos >= size)
303 break;
304 if (count > size - pos)
305 count = size - pos;
306
307 this_round = count;
308 if (this_round > CON_BUF_SIZE)
309 this_round = CON_BUF_SIZE;
310
311 /* Perform the whole read into the local con_buf.
312 * Then we can drop the console spinlock and safely
313 * attempt to move it to userspace.
314 */
315
316 con_buf_start = con_buf0 = con_buf;
317 orig_count = this_round;
318 maxcol = vc->vc_cols;
319 if (uni_mode) {
320 unsigned int nr;
321
322 ret = vc_uniscr_check(vc);
323 if (ret)
324 break;
325 p /= 4;
326 row = p / vc->vc_cols;
327 col = p % maxcol;
328 nr = maxcol - col;
329 do {
330 if (nr > this_round/4)
331 nr = this_round/4;
332 vc_uniscr_copy_line(vc, con_buf0, viewed,
333 row, col, nr);
334 con_buf0 += nr * 4;
335 this_round -= nr * 4;
336 row++;
337 col = 0;
338 nr = maxcol;
339 } while (this_round);
340 } else if (!attr) {
341 org = screen_pos(vc, p, viewed);
342 col = p % maxcol;
343 p += maxcol - col;
344 while (this_round-- > 0) {
345 *con_buf0++ = (vcs_scr_readw(vc, org++) & 0xff);
346 if (++col == maxcol) {
347 org = screen_pos(vc, p, viewed);
348 col = 0;
349 p += maxcol;
350 }
351 }
352 } else {
353 if (p < HEADER_SIZE) {
354 size_t tmp_count;
355
356 /* clamp header values if they don't fit */
357 con_buf0[0] = min(vc->vc_rows, 0xFFu);
358 con_buf0[1] = min(vc->vc_cols, 0xFFu);
359 getconsxy(vc, con_buf0 + 2);
360
361 con_buf_start += p;
362 this_round += p;
363 if (this_round > CON_BUF_SIZE) {
364 this_round = CON_BUF_SIZE;
365 orig_count = this_round - p;
366 }
367
368 tmp_count = HEADER_SIZE;
369 if (tmp_count > this_round)
370 tmp_count = this_round;
371
372 /* Advance state pointers and move on. */
373 this_round -= tmp_count;
374 p = HEADER_SIZE;
375 con_buf0 = con_buf + HEADER_SIZE;
376 /* If this_round >= 0, then p is even... */
377 } else if (p & 1) {
378 /* Skip first byte for output if start address is odd
379 * Update region sizes up/down depending on free
380 * space in buffer.
381 */
382 con_buf_start++;
383 if (this_round < CON_BUF_SIZE)
384 this_round++;
385 else
386 orig_count--;
387 }
388 if (this_round > 0) {
389 unsigned short *tmp_buf = (unsigned short *)con_buf0;
390
391 p -= HEADER_SIZE;
392 p /= 2;
393 col = p % maxcol;
394
395 org = screen_pos(vc, p, viewed);
396 p += maxcol - col;
397
398 /* Buffer has even length, so we can always copy
399 * character + attribute. We do not copy last byte
400 * to userspace if this_round is odd.
401 */
402 this_round = (this_round + 1) >> 1;
403
404 while (this_round) {
405 *tmp_buf++ = vcs_scr_readw(vc, org++);
406 this_round --;
407 if (++col == maxcol) {
408 org = screen_pos(vc, p, viewed);
409 col = 0;
410 p += maxcol;
411 }
412 }
413 }
414 }
415
416 /* Finally, release the console semaphore while we push
417 * all the data to userspace from our temporary buffer.
418 *
419 * AKPM: Even though it's a semaphore, we should drop it because
420 * the pagefault handling code may want to call printk().
421 */
422
423 console_unlock();
424 ret = copy_to_user(buf, con_buf_start, orig_count);
425 console_lock();
426
427 if (ret) {
428 read += (orig_count - ret);
429 ret = -EFAULT;
430 break;
431 }
432 buf += orig_count;
433 pos += orig_count;
434 read += orig_count;
435 count -= orig_count;
436 }
437 *ppos += read;
438 if (read)
439 ret = read;
440unlock_out:
441 console_unlock();
442 free_page((unsigned long) con_buf);
443 return ret;
444}
445
446static ssize_t
447vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
448{
449 struct inode *inode = file_inode(file);
450 struct vc_data *vc;
451 long pos;
452 long attr, size, written;
453 char *con_buf0;
454 int col, maxcol, viewed;
455 u16 *org0 = NULL, *org = NULL;
456 size_t ret;
457 char *con_buf;
458
459 con_buf = (char *) __get_free_page(GFP_KERNEL);
460 if (!con_buf)
461 return -ENOMEM;
462
463 pos = *ppos;
464
465 /* Select the proper current console and verify
466 * sanity of the situation under the console lock.
467 */
468 console_lock();
469
470 attr = use_attributes(inode);
471 ret = -ENXIO;
472 vc = vcs_vc(inode, &viewed);
473 if (!vc)
474 goto unlock_out;
475
476 size = vcs_size(inode);
477 ret = -EINVAL;
478 if (pos < 0 || pos > size)
479 goto unlock_out;
480 if (count > size - pos)
481 count = size - pos;
482 written = 0;
483 while (count) {
484 long this_round = count;
485 size_t orig_count;
486 long p;
487
488 if (this_round > CON_BUF_SIZE)
489 this_round = CON_BUF_SIZE;
490
491 /* Temporarily drop the console lock so that we can read
492 * in the write data from userspace safely.
493 */
494 console_unlock();
495 ret = copy_from_user(con_buf, buf, this_round);
496 console_lock();
497
498 if (ret) {
499 this_round -= ret;
500 if (!this_round) {
501 /* Abort loop if no data were copied. Otherwise
502 * fail with -EFAULT.
503 */
504 if (written)
505 break;
506 ret = -EFAULT;
507 goto unlock_out;
508 }
509 }
510
511 /* The vcs_size might have changed while we slept to grab
512 * the user buffer, so recheck.
513 * Return data written up to now on failure.
514 */
515 size = vcs_size(inode);
516 if (size < 0) {
517 if (written)
518 break;
519 ret = size;
520 goto unlock_out;
521 }
522 if (pos >= size)
523 break;
524 if (this_round > size - pos)
525 this_round = size - pos;
526
527 /* OK, now actually push the write to the console
528 * under the lock using the local kernel buffer.
529 */
530
531 con_buf0 = con_buf;
532 orig_count = this_round;
533 maxcol = vc->vc_cols;
534 p = pos;
535 if (!attr) {
536 org0 = org = screen_pos(vc, p, viewed);
537 col = p % maxcol;
538 p += maxcol - col;
539
540 while (this_round > 0) {
541 unsigned char c = *con_buf0++;
542
543 this_round--;
544 vcs_scr_writew(vc,
545 (vcs_scr_readw(vc, org) & 0xff00) | c, org);
546 org++;
547 if (++col == maxcol) {
548 org = screen_pos(vc, p, viewed);
549 col = 0;
550 p += maxcol;
551 }
552 }
553 } else {
554 if (p < HEADER_SIZE) {
555 char header[HEADER_SIZE];
556
557 getconsxy(vc, header + 2);
558 while (p < HEADER_SIZE && this_round > 0) {
559 this_round--;
560 header[p++] = *con_buf0++;
561 }
562 if (!viewed)
563 putconsxy(vc, header + 2);
564 }
565 p -= HEADER_SIZE;
566 col = (p/2) % maxcol;
567 if (this_round > 0) {
568 org0 = org = screen_pos(vc, p/2, viewed);
569 if ((p & 1) && this_round > 0) {
570 char c;
571
572 this_round--;
573 c = *con_buf0++;
574#ifdef __BIG_ENDIAN
575 vcs_scr_writew(vc, c |
576 (vcs_scr_readw(vc, org) & 0xff00), org);
577#else
578 vcs_scr_writew(vc, (c << 8) |
579 (vcs_scr_readw(vc, org) & 0xff), org);
580#endif
581 org++;
582 p++;
583 if (++col == maxcol) {
584 org = screen_pos(vc, p/2, viewed);
585 col = 0;
586 }
587 }
588 p /= 2;
589 p += maxcol - col;
590 }
591 while (this_round > 1) {
592 unsigned short w;
593
594 w = get_unaligned(((unsigned short *)con_buf0));
595 vcs_scr_writew(vc, w, org++);
596 con_buf0 += 2;
597 this_round -= 2;
598 if (++col == maxcol) {
599 org = screen_pos(vc, p, viewed);
600 col = 0;
601 p += maxcol;
602 }
603 }
604 if (this_round > 0) {
605 unsigned char c;
606
607 c = *con_buf0++;
608#ifdef __BIG_ENDIAN
609 vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff) | (c << 8), org);
610#else
611 vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff00) | c, org);
612#endif
613 }
614 }
615 count -= orig_count;
616 written += orig_count;
617 buf += orig_count;
618 pos += orig_count;
619 if (org0)
620 update_region(vc, (unsigned long)(org0), org - org0);
621 }
622 *ppos += written;
623 ret = written;
624 if (written)
625 vcs_scr_updated(vc);
626
627unlock_out:
628 console_unlock();
629 free_page((unsigned long) con_buf);
630 return ret;
631}
632
633static __poll_t
634vcs_poll(struct file *file, poll_table *wait)
635{
636 struct vcs_poll_data *poll = vcs_poll_data_get(file);
637 __poll_t ret = DEFAULT_POLLMASK|EPOLLERR;
638
639 if (poll) {
640 poll_wait(file, &poll->waitq, wait);
641 switch (poll->event) {
642 case VT_UPDATE:
643 ret = DEFAULT_POLLMASK|EPOLLPRI;
644 break;
645 case VT_DEALLOCATE:
646 ret = DEFAULT_POLLMASK|EPOLLHUP|EPOLLERR;
647 break;
648 case 0:
649 ret = DEFAULT_POLLMASK;
650 break;
651 }
652 }
653 return ret;
654}
655
656static int
657vcs_fasync(int fd, struct file *file, int on)
658{
659 struct vcs_poll_data *poll = file->private_data;
660
661 if (!poll) {
662 /* don't allocate anything if all we want is disable fasync */
663 if (!on)
664 return 0;
665 poll = vcs_poll_data_get(file);
666 if (!poll)
667 return -ENOMEM;
668 }
669
670 return fasync_helper(fd, file, on, &poll->fasync);
671}
672
673static int
674vcs_open(struct inode *inode, struct file *filp)
675{
676 unsigned int currcons = console(inode);
677 bool attr = use_attributes(inode);
678 bool uni_mode = use_unicode(inode);
679 int ret = 0;
680
681 /* we currently don't support attributes in unicode mode */
682 if (attr && uni_mode)
683 return -EOPNOTSUPP;
684
685 console_lock();
686 if(currcons && !vc_cons_allocated(currcons-1))
687 ret = -ENXIO;
688 console_unlock();
689 return ret;
690}
691
692static int vcs_release(struct inode *inode, struct file *file)
693{
694 struct vcs_poll_data *poll = file->private_data;
695
696 if (poll)
697 vcs_poll_data_free(poll);
698 return 0;
699}
700
701static const struct file_operations vcs_fops = {
702 .llseek = vcs_lseek,
703 .read = vcs_read,
704 .write = vcs_write,
705 .poll = vcs_poll,
706 .fasync = vcs_fasync,
707 .open = vcs_open,
708 .release = vcs_release,
709};
710
711static struct class *vc_class;
712
713void vcs_make_sysfs(int index)
714{
715 device_create(vc_class, NULL, MKDEV(VCS_MAJOR, index + 1), NULL,
716 "vcs%u", index + 1);
717 device_create(vc_class, NULL, MKDEV(VCS_MAJOR, index + 65), NULL,
718 "vcsu%u", index + 1);
719 device_create(vc_class, NULL, MKDEV(VCS_MAJOR, index + 129), NULL,
720 "vcsa%u", index + 1);
721}
722
723void vcs_remove_sysfs(int index)
724{
725 device_destroy(vc_class, MKDEV(VCS_MAJOR, index + 1));
726 device_destroy(vc_class, MKDEV(VCS_MAJOR, index + 65));
727 device_destroy(vc_class, MKDEV(VCS_MAJOR, index + 129));
728}
729
730int __init vcs_init(void)
731{
732 unsigned int i;
733
734 if (register_chrdev(VCS_MAJOR, "vcs", &vcs_fops))
735 panic("unable to get major %d for vcs device", VCS_MAJOR);
736 vc_class = class_create(THIS_MODULE, "vc");
737
738 device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 0), NULL, "vcs");
739 device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 64), NULL, "vcsu");
740 device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 128), NULL, "vcsa");
741 for (i = 0; i < MIN_NR_CONSOLES; i++)
742 vcs_make_sysfs(i);
743 return 0;
744}