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Merge tag 'clk-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/clk/linux
[mirror_ubuntu-bionic-kernel.git] / drivers / tty / vt / vc_screen.c
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Provide access to virtual console memory.
4 * /dev/vcs0: 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 * This replaces screendump and part of selection, so that the system
14 * administrator can control access using file system permissions.
15 *
16 * aeb@cwi.nl - efter Friedas begravelse - 950211
17 *
18 * machek@k332.feld.cvut.cz - modified not to send characters to wrong console
19 * - fixed some fatal off-by-one bugs (0-- no longer == -1 -> looping and looping and looping...)
20 * - making it shorter - scr_readw are macros which expand in PRETTY long code
21 */
22
23 #include <linux/kernel.h>
24 #include <linux/major.h>
25 #include <linux/errno.h>
26 #include <linux/export.h>
27 #include <linux/tty.h>
28 #include <linux/interrupt.h>
29 #include <linux/mm.h>
30 #include <linux/init.h>
31 #include <linux/vt_kern.h>
32 #include <linux/selection.h>
33 #include <linux/kbd_kern.h>
34 #include <linux/console.h>
35 #include <linux/device.h>
36 #include <linux/sched.h>
37 #include <linux/fs.h>
38 #include <linux/poll.h>
39 #include <linux/signal.h>
40 #include <linux/slab.h>
41 #include <linux/notifier.h>
42
43 #include <linux/uaccess.h>
44 #include <asm/byteorder.h>
45 #include <asm/unaligned.h>
46
47 #undef attr
48 #undef org
49 #undef addr
50 #define HEADER_SIZE 4
51
52 #define CON_BUF_SIZE (CONFIG_BASE_SMALL ? 256 : PAGE_SIZE)
53
54 struct vcs_poll_data {
55 struct notifier_block notifier;
56 unsigned int cons_num;
57 bool seen_last_update;
58 wait_queue_head_t waitq;
59 struct fasync_struct *fasync;
60 };
61
62 static int
63 vcs_notifier(struct notifier_block *nb, unsigned long code, void *_param)
64 {
65 struct vt_notifier_param *param = _param;
66 struct vc_data *vc = param->vc;
67 struct vcs_poll_data *poll =
68 container_of(nb, struct vcs_poll_data, notifier);
69 int currcons = poll->cons_num;
70
71 if (code != VT_UPDATE)
72 return NOTIFY_DONE;
73
74 if (currcons == 0)
75 currcons = fg_console;
76 else
77 currcons--;
78 if (currcons != vc->vc_num)
79 return NOTIFY_DONE;
80
81 poll->seen_last_update = false;
82 wake_up_interruptible(&poll->waitq);
83 kill_fasync(&poll->fasync, SIGIO, POLL_IN);
84 return NOTIFY_OK;
85 }
86
87 static void
88 vcs_poll_data_free(struct vcs_poll_data *poll)
89 {
90 unregister_vt_notifier(&poll->notifier);
91 kfree(poll);
92 }
93
94 static struct vcs_poll_data *
95 vcs_poll_data_get(struct file *file)
96 {
97 struct vcs_poll_data *poll = file->private_data, *kill = NULL;
98
99 if (poll)
100 return poll;
101
102 poll = kzalloc(sizeof(*poll), GFP_KERNEL);
103 if (!poll)
104 return NULL;
105 poll->cons_num = iminor(file_inode(file)) & 127;
106 init_waitqueue_head(&poll->waitq);
107 poll->notifier.notifier_call = vcs_notifier;
108 if (register_vt_notifier(&poll->notifier) != 0) {
109 kfree(poll);
110 return NULL;
111 }
112
113 /*
114 * This code may be called either through ->poll() or ->fasync().
115 * If we have two threads using the same file descriptor, they could
116 * both enter this function, both notice that the structure hasn't
117 * been allocated yet and go ahead allocating it in parallel, but
118 * only one of them must survive and be shared otherwise we'd leak
119 * memory with a dangling notifier callback.
120 */
121 spin_lock(&file->f_lock);
122 if (!file->private_data) {
123 file->private_data = poll;
124 } else {
125 /* someone else raced ahead of us */
126 kill = poll;
127 poll = file->private_data;
128 }
129 spin_unlock(&file->f_lock);
130 if (kill)
131 vcs_poll_data_free(kill);
132
133 return poll;
134 }
135
136 /*
137 * Returns VC for inode.
138 * Must be called with console_lock.
139 */
140 static struct vc_data*
141 vcs_vc(struct inode *inode, int *viewed)
142 {
143 unsigned int currcons = iminor(inode) & 127;
144
145 WARN_CONSOLE_UNLOCKED();
146
147 if (currcons == 0) {
148 currcons = fg_console;
149 if (viewed)
150 *viewed = 1;
151 } else {
152 currcons--;
153 if (viewed)
154 *viewed = 0;
155 }
156 return vc_cons[currcons].d;
157 }
158
159 /*
160 * Returns size for VC carried by inode.
161 * Must be called with console_lock.
162 */
163 static int
164 vcs_size(struct inode *inode)
165 {
166 int size;
167 int minor = iminor(inode);
168 struct vc_data *vc;
169
170 WARN_CONSOLE_UNLOCKED();
171
172 vc = vcs_vc(inode, NULL);
173 if (!vc)
174 return -ENXIO;
175
176 size = vc->vc_rows * vc->vc_cols;
177
178 if (minor & 128)
179 size = 2*size + HEADER_SIZE;
180 return size;
181 }
182
183 static loff_t vcs_lseek(struct file *file, loff_t offset, int orig)
184 {
185 int size;
186
187 console_lock();
188 size = vcs_size(file_inode(file));
189 console_unlock();
190 if (size < 0)
191 return size;
192 return fixed_size_llseek(file, offset, orig, size);
193 }
194
195
196 static ssize_t
197 vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
198 {
199 struct inode *inode = file_inode(file);
200 unsigned int currcons = iminor(inode);
201 struct vc_data *vc;
202 struct vcs_poll_data *poll;
203 long pos;
204 long attr, read;
205 int col, maxcol, viewed;
206 unsigned short *org = NULL;
207 ssize_t ret;
208 char *con_buf;
209
210 con_buf = (char *) __get_free_page(GFP_KERNEL);
211 if (!con_buf)
212 return -ENOMEM;
213
214 pos = *ppos;
215
216 /* Select the proper current console and verify
217 * sanity of the situation under the console lock.
218 */
219 console_lock();
220
221 attr = (currcons & 128);
222 ret = -ENXIO;
223 vc = vcs_vc(inode, &viewed);
224 if (!vc)
225 goto unlock_out;
226
227 ret = -EINVAL;
228 if (pos < 0)
229 goto unlock_out;
230 poll = file->private_data;
231 if (count && poll)
232 poll->seen_last_update = true;
233 read = 0;
234 ret = 0;
235 while (count) {
236 char *con_buf0, *con_buf_start;
237 long this_round, size;
238 ssize_t orig_count;
239 long p = pos;
240
241 /* Check whether we are above size each round,
242 * as copy_to_user at the end of this loop
243 * could sleep.
244 */
245 size = vcs_size(inode);
246 if (size < 0) {
247 if (read)
248 break;
249 ret = size;
250 goto unlock_out;
251 }
252 if (pos >= size)
253 break;
254 if (count > size - pos)
255 count = size - pos;
256
257 this_round = count;
258 if (this_round > CON_BUF_SIZE)
259 this_round = CON_BUF_SIZE;
260
261 /* Perform the whole read into the local con_buf.
262 * Then we can drop the console spinlock and safely
263 * attempt to move it to userspace.
264 */
265
266 con_buf_start = con_buf0 = con_buf;
267 orig_count = this_round;
268 maxcol = vc->vc_cols;
269 if (!attr) {
270 org = screen_pos(vc, p, viewed);
271 col = p % maxcol;
272 p += maxcol - col;
273 while (this_round-- > 0) {
274 *con_buf0++ = (vcs_scr_readw(vc, org++) & 0xff);
275 if (++col == maxcol) {
276 org = screen_pos(vc, p, viewed);
277 col = 0;
278 p += maxcol;
279 }
280 }
281 } else {
282 if (p < HEADER_SIZE) {
283 size_t tmp_count;
284
285 con_buf0[0] = (char)vc->vc_rows;
286 con_buf0[1] = (char)vc->vc_cols;
287 getconsxy(vc, con_buf0 + 2);
288
289 con_buf_start += p;
290 this_round += p;
291 if (this_round > CON_BUF_SIZE) {
292 this_round = CON_BUF_SIZE;
293 orig_count = this_round - p;
294 }
295
296 tmp_count = HEADER_SIZE;
297 if (tmp_count > this_round)
298 tmp_count = this_round;
299
300 /* Advance state pointers and move on. */
301 this_round -= tmp_count;
302 p = HEADER_SIZE;
303 con_buf0 = con_buf + HEADER_SIZE;
304 /* If this_round >= 0, then p is even... */
305 } else if (p & 1) {
306 /* Skip first byte for output if start address is odd
307 * Update region sizes up/down depending on free
308 * space in buffer.
309 */
310 con_buf_start++;
311 if (this_round < CON_BUF_SIZE)
312 this_round++;
313 else
314 orig_count--;
315 }
316 if (this_round > 0) {
317 unsigned short *tmp_buf = (unsigned short *)con_buf0;
318
319 p -= HEADER_SIZE;
320 p /= 2;
321 col = p % maxcol;
322
323 org = screen_pos(vc, p, viewed);
324 p += maxcol - col;
325
326 /* Buffer has even length, so we can always copy
327 * character + attribute. We do not copy last byte
328 * to userspace if this_round is odd.
329 */
330 this_round = (this_round + 1) >> 1;
331
332 while (this_round) {
333 *tmp_buf++ = vcs_scr_readw(vc, org++);
334 this_round --;
335 if (++col == maxcol) {
336 org = screen_pos(vc, p, viewed);
337 col = 0;
338 p += maxcol;
339 }
340 }
341 }
342 }
343
344 /* Finally, release the console semaphore while we push
345 * all the data to userspace from our temporary buffer.
346 *
347 * AKPM: Even though it's a semaphore, we should drop it because
348 * the pagefault handling code may want to call printk().
349 */
350
351 console_unlock();
352 ret = copy_to_user(buf, con_buf_start, orig_count);
353 console_lock();
354
355 if (ret) {
356 read += (orig_count - ret);
357 ret = -EFAULT;
358 break;
359 }
360 buf += orig_count;
361 pos += orig_count;
362 read += orig_count;
363 count -= orig_count;
364 }
365 *ppos += read;
366 if (read)
367 ret = read;
368 unlock_out:
369 console_unlock();
370 free_page((unsigned long) con_buf);
371 return ret;
372 }
373
374 static ssize_t
375 vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
376 {
377 struct inode *inode = file_inode(file);
378 unsigned int currcons = iminor(inode);
379 struct vc_data *vc;
380 long pos;
381 long attr, size, written;
382 char *con_buf0;
383 int col, maxcol, viewed;
384 u16 *org0 = NULL, *org = NULL;
385 size_t ret;
386 char *con_buf;
387
388 con_buf = (char *) __get_free_page(GFP_KERNEL);
389 if (!con_buf)
390 return -ENOMEM;
391
392 pos = *ppos;
393
394 /* Select the proper current console and verify
395 * sanity of the situation under the console lock.
396 */
397 console_lock();
398
399 attr = (currcons & 128);
400 ret = -ENXIO;
401 vc = vcs_vc(inode, &viewed);
402 if (!vc)
403 goto unlock_out;
404
405 size = vcs_size(inode);
406 ret = -EINVAL;
407 if (pos < 0 || pos > size)
408 goto unlock_out;
409 if (count > size - pos)
410 count = size - pos;
411 written = 0;
412 while (count) {
413 long this_round = count;
414 size_t orig_count;
415 long p;
416
417 if (this_round > CON_BUF_SIZE)
418 this_round = CON_BUF_SIZE;
419
420 /* Temporarily drop the console lock so that we can read
421 * in the write data from userspace safely.
422 */
423 console_unlock();
424 ret = copy_from_user(con_buf, buf, this_round);
425 console_lock();
426
427 if (ret) {
428 this_round -= ret;
429 if (!this_round) {
430 /* Abort loop if no data were copied. Otherwise
431 * fail with -EFAULT.
432 */
433 if (written)
434 break;
435 ret = -EFAULT;
436 goto unlock_out;
437 }
438 }
439
440 /* The vcs_size might have changed while we slept to grab
441 * the user buffer, so recheck.
442 * Return data written up to now on failure.
443 */
444 size = vcs_size(inode);
445 if (size < 0) {
446 if (written)
447 break;
448 ret = size;
449 goto unlock_out;
450 }
451 if (pos >= size)
452 break;
453 if (this_round > size - pos)
454 this_round = size - pos;
455
456 /* OK, now actually push the write to the console
457 * under the lock using the local kernel buffer.
458 */
459
460 con_buf0 = con_buf;
461 orig_count = this_round;
462 maxcol = vc->vc_cols;
463 p = pos;
464 if (!attr) {
465 org0 = org = screen_pos(vc, p, viewed);
466 col = p % maxcol;
467 p += maxcol - col;
468
469 while (this_round > 0) {
470 unsigned char c = *con_buf0++;
471
472 this_round--;
473 vcs_scr_writew(vc,
474 (vcs_scr_readw(vc, org) & 0xff00) | c, org);
475 org++;
476 if (++col == maxcol) {
477 org = screen_pos(vc, p, viewed);
478 col = 0;
479 p += maxcol;
480 }
481 }
482 } else {
483 if (p < HEADER_SIZE) {
484 char header[HEADER_SIZE];
485
486 getconsxy(vc, header + 2);
487 while (p < HEADER_SIZE && this_round > 0) {
488 this_round--;
489 header[p++] = *con_buf0++;
490 }
491 if (!viewed)
492 putconsxy(vc, header + 2);
493 }
494 p -= HEADER_SIZE;
495 col = (p/2) % maxcol;
496 if (this_round > 0) {
497 org0 = org = screen_pos(vc, p/2, viewed);
498 if ((p & 1) && this_round > 0) {
499 char c;
500
501 this_round--;
502 c = *con_buf0++;
503 #ifdef __BIG_ENDIAN
504 vcs_scr_writew(vc, c |
505 (vcs_scr_readw(vc, org) & 0xff00), org);
506 #else
507 vcs_scr_writew(vc, (c << 8) |
508 (vcs_scr_readw(vc, org) & 0xff), org);
509 #endif
510 org++;
511 p++;
512 if (++col == maxcol) {
513 org = screen_pos(vc, p/2, viewed);
514 col = 0;
515 }
516 }
517 p /= 2;
518 p += maxcol - col;
519 }
520 while (this_round > 1) {
521 unsigned short w;
522
523 w = get_unaligned(((unsigned short *)con_buf0));
524 vcs_scr_writew(vc, w, org++);
525 con_buf0 += 2;
526 this_round -= 2;
527 if (++col == maxcol) {
528 org = screen_pos(vc, p, viewed);
529 col = 0;
530 p += maxcol;
531 }
532 }
533 if (this_round > 0) {
534 unsigned char c;
535
536 c = *con_buf0++;
537 #ifdef __BIG_ENDIAN
538 vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff) | (c << 8), org);
539 #else
540 vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff00) | c, org);
541 #endif
542 }
543 }
544 count -= orig_count;
545 written += orig_count;
546 buf += orig_count;
547 pos += orig_count;
548 if (org0)
549 update_region(vc, (unsigned long)(org0), org - org0);
550 }
551 *ppos += written;
552 ret = written;
553 if (written)
554 vcs_scr_updated(vc);
555
556 unlock_out:
557 console_unlock();
558 free_page((unsigned long) con_buf);
559 return ret;
560 }
561
562 static unsigned int
563 vcs_poll(struct file *file, poll_table *wait)
564 {
565 struct vcs_poll_data *poll = vcs_poll_data_get(file);
566 int ret = DEFAULT_POLLMASK|POLLERR|POLLPRI;
567
568 if (poll) {
569 poll_wait(file, &poll->waitq, wait);
570 if (poll->seen_last_update)
571 ret = DEFAULT_POLLMASK;
572 }
573 return ret;
574 }
575
576 static int
577 vcs_fasync(int fd, struct file *file, int on)
578 {
579 struct vcs_poll_data *poll = file->private_data;
580
581 if (!poll) {
582 /* don't allocate anything if all we want is disable fasync */
583 if (!on)
584 return 0;
585 poll = vcs_poll_data_get(file);
586 if (!poll)
587 return -ENOMEM;
588 }
589
590 return fasync_helper(fd, file, on, &poll->fasync);
591 }
592
593 static int
594 vcs_open(struct inode *inode, struct file *filp)
595 {
596 unsigned int currcons = iminor(inode) & 127;
597 int ret = 0;
598
599 console_lock();
600 if(currcons && !vc_cons_allocated(currcons-1))
601 ret = -ENXIO;
602 console_unlock();
603 return ret;
604 }
605
606 static int vcs_release(struct inode *inode, struct file *file)
607 {
608 struct vcs_poll_data *poll = file->private_data;
609
610 if (poll)
611 vcs_poll_data_free(poll);
612 return 0;
613 }
614
615 static const struct file_operations vcs_fops = {
616 .llseek = vcs_lseek,
617 .read = vcs_read,
618 .write = vcs_write,
619 .poll = vcs_poll,
620 .fasync = vcs_fasync,
621 .open = vcs_open,
622 .release = vcs_release,
623 };
624
625 static struct class *vc_class;
626
627 void vcs_make_sysfs(int index)
628 {
629 device_create(vc_class, NULL, MKDEV(VCS_MAJOR, index + 1), NULL,
630 "vcs%u", index + 1);
631 device_create(vc_class, NULL, MKDEV(VCS_MAJOR, index + 129), NULL,
632 "vcsa%u", index + 1);
633 }
634
635 void vcs_remove_sysfs(int index)
636 {
637 device_destroy(vc_class, MKDEV(VCS_MAJOR, index + 1));
638 device_destroy(vc_class, MKDEV(VCS_MAJOR, index + 129));
639 }
640
641 int __init vcs_init(void)
642 {
643 unsigned int i;
644
645 if (register_chrdev(VCS_MAJOR, "vcs", &vcs_fops))
646 panic("unable to get major %d for vcs device", VCS_MAJOR);
647 vc_class = class_create(THIS_MODULE, "vc");
648
649 device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 0), NULL, "vcs");
650 device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 128), NULL, "vcsa");
651 for (i = 0; i < MIN_NR_CONSOLES; i++)
652 vcs_make_sysfs(i);
653 return 0;
654 }
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