1 /*
2 * Provide access to virtual console memory.
3 * /dev/vcs0: the screen as it is being viewed right now (possibly scrolled)
4 * /dev/vcsN: the screen of /dev/ttyN (1 <= N <= 63)
5 * [minor: N]
6 *
7 * /dev/vcsaN: idem, but including attributes, and prefixed with
8 * the 4 bytes lines,columns,x,y (as screendump used to give).
9 * Attribute/character pair is in native endianity.
10 * [minor: N+128]
11 *
12 * This replaces screendump and part of selection, so that the system
13 * administrator can control access using file system permissions.
14 *
15 * aeb@cwi.nl - efter Friedas begravelse - 950211
16 *
17 * machek@k332.feld.cvut.cz - modified not to send characters to wrong console
18 * - fixed some fatal off-by-one bugs (0-- no longer == -1 -> looping and looping and looping...)
19 * - making it shorter - scr_readw are macros which expand in PRETTY long code
20 */
21
22 #include <linux/kernel.h>
23 #include <linux/major.h>
24 #include <linux/errno.h>
25 #include <linux/export.h>
26 #include <linux/tty.h>
27 #include <linux/interrupt.h>
28 #include <linux/mm.h>
29 #include <linux/init.h>
30 #include <linux/vt_kern.h>
31 #include <linux/selection.h>
32 #include <linux/kbd_kern.h>
33 #include <linux/console.h>
34 #include <linux/device.h>
35 #include <linux/sched.h>
36 #include <linux/fs.h>
37 #include <linux/poll.h>
38 #include <linux/signal.h>
39 #include <linux/slab.h>
40 #include <linux/notifier.h>
41
42 #include <asm/uaccess.h>
43 #include <asm/byteorder.h>
44 #include <asm/unaligned.h>
45
46 #undef attr
47 #undef org
48 #undef addr
49 #define HEADER_SIZE 4
50
51 #define CON_BUF_SIZE (CONFIG_BASE_SMALL ? 256 : PAGE_SIZE)
52
53 struct vcs_poll_data {
54 struct notifier_block notifier;
55 unsigned int cons_num;
56 bool seen_last_update;
57 wait_queue_head_t waitq;
58 struct fasync_struct *fasync;
59 };
60
61 static int
vcs_notifier(struct notifier_block * nb,unsigned long code,void * _param)62 vcs_notifier(struct notifier_block *nb, unsigned long code, void *_param)
63 {
64 struct vt_notifier_param *param = _param;
65 struct vc_data *vc = param->vc;
66 struct vcs_poll_data *poll =
67 container_of(nb, struct vcs_poll_data, notifier);
68 int currcons = poll->cons_num;
69
70 if (code != VT_UPDATE)
71 return NOTIFY_DONE;
72
73 if (currcons == 0)
74 currcons = fg_console;
75 else
76 currcons--;
77 if (currcons != vc->vc_num)
78 return NOTIFY_DONE;
79
80 poll->seen_last_update = false;
81 wake_up_interruptible(&poll->waitq);
82 kill_fasync(&poll->fasync, SIGIO, POLL_IN);
83 return NOTIFY_OK;
84 }
85
86 static void
vcs_poll_data_free(struct vcs_poll_data * poll)87 vcs_poll_data_free(struct vcs_poll_data *poll)
88 {
89 unregister_vt_notifier(&poll->notifier);
90 kfree(poll);
91 }
92
93 static struct vcs_poll_data *
vcs_poll_data_get(struct file * file)94 vcs_poll_data_get(struct file *file)
95 {
96 struct vcs_poll_data *poll = file->private_data, *kill = NULL;
97
98 if (poll)
99 return poll;
100
101 poll = kzalloc(sizeof(*poll), GFP_KERNEL);
102 if (!poll)
103 return NULL;
104 poll->cons_num = iminor(file->f_path.dentry->d_inode) & 127;
105 init_waitqueue_head(&poll->waitq);
106 poll->notifier.notifier_call = vcs_notifier;
107 if (register_vt_notifier(&poll->notifier) != 0) {
108 kfree(poll);
109 return NULL;
110 }
111
112 /*
113 * This code may be called either through ->poll() or ->fasync().
114 * If we have two threads using the same file descriptor, they could
115 * both enter this function, both notice that the structure hasn't
116 * been allocated yet and go ahead allocating it in parallel, but
117 * only one of them must survive and be shared otherwise we'd leak
118 * memory with a dangling notifier callback.
119 */
120 spin_lock(&file->f_lock);
121 if (!file->private_data) {
122 file->private_data = poll;
123 } else {
124 /* someone else raced ahead of us */
125 kill = poll;
126 poll = file->private_data;
127 }
128 spin_unlock(&file->f_lock);
129 if (kill)
130 vcs_poll_data_free(kill);
131
132 return poll;
133 }
134
135 /*
136 * Returns VC for inode.
137 * Must be called with console_lock.
138 */
139 static struct vc_data*
vcs_vc(struct inode * inode,int * viewed)140 vcs_vc(struct inode *inode, int *viewed)
141 {
142 unsigned int currcons = iminor(inode) & 127;
143
144 WARN_CONSOLE_UNLOCKED();
145
146 if (currcons == 0) {
147 currcons = fg_console;
148 if (viewed)
149 *viewed = 1;
150 } else {
151 currcons--;
152 if (viewed)
153 *viewed = 0;
154 }
155 return vc_cons[currcons].d;
156 }
157
158 /*
159 * Returns size for VC carried by inode.
160 * Must be called with console_lock.
161 */
162 static int
vcs_size(struct inode * inode)163 vcs_size(struct inode *inode)
164 {
165 int size;
166 int minor = iminor(inode);
167 struct vc_data *vc;
168
169 WARN_CONSOLE_UNLOCKED();
170
171 vc = vcs_vc(inode, NULL);
172 if (!vc)
173 return -ENXIO;
174
175 size = vc->vc_rows * vc->vc_cols;
176
177 if (minor & 128)
178 size = 2*size + HEADER_SIZE;
179 return size;
180 }
181
vcs_lseek(struct file * file,loff_t offset,int orig)182 static loff_t vcs_lseek(struct file *file, loff_t offset, int orig)
183 {
184 int size;
185
186 console_lock();
187 size = vcs_size(file->f_path.dentry->d_inode);
188 console_unlock();
189 if (size < 0)
190 return size;
191 switch (orig) {
192 default:
193 return -EINVAL;
194 case 2:
195 offset += size;
196 break;
197 case 1:
198 offset += file->f_pos;
199 case 0:
200 break;
201 }
202 if (offset < 0 || offset > size) {
203 return -EINVAL;
204 }
205 file->f_pos = offset;
206 return file->f_pos;
207 }
208
209
210 static ssize_t
vcs_read(struct file * file,char __user * buf,size_t count,loff_t * ppos)211 vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
212 {
213 struct inode *inode = file->f_path.dentry->d_inode;
214 unsigned int currcons = iminor(inode);
215 struct vc_data *vc;
216 struct vcs_poll_data *poll;
217 long pos;
218 long attr, read;
219 int col, maxcol, viewed;
220 unsigned short *org = NULL;
221 ssize_t ret;
222 char *con_buf;
223
224 con_buf = (char *) __get_free_page(GFP_KERNEL);
225 if (!con_buf)
226 return -ENOMEM;
227
228 pos = *ppos;
229
230 /* Select the proper current console and verify
231 * sanity of the situation under the console lock.
232 */
233 console_lock();
234
235 attr = (currcons & 128);
236 ret = -ENXIO;
237 vc = vcs_vc(inode, &viewed);
238 if (!vc)
239 goto unlock_out;
240
241 ret = -EINVAL;
242 if (pos < 0)
243 goto unlock_out;
244 poll = file->private_data;
245 if (count && poll)
246 poll->seen_last_update = true;
247 read = 0;
248 ret = 0;
249 while (count) {
250 char *con_buf0, *con_buf_start;
251 long this_round, size;
252 ssize_t orig_count;
253 long p = pos;
254
255 /* Check whether we are above size each round,
256 * as copy_to_user at the end of this loop
257 * could sleep.
258 */
259 size = vcs_size(inode);
260 if (size < 0) {
261 if (read)
262 break;
263 ret = size;
264 goto unlock_out;
265 }
266 if (pos >= size)
267 break;
268 if (count > size - pos)
269 count = size - pos;
270
271 this_round = count;
272 if (this_round > CON_BUF_SIZE)
273 this_round = CON_BUF_SIZE;
274
275 /* Perform the whole read into the local con_buf.
276 * Then we can drop the console spinlock and safely
277 * attempt to move it to userspace.
278 */
279
280 con_buf_start = con_buf0 = con_buf;
281 orig_count = this_round;
282 maxcol = vc->vc_cols;
283 if (!attr) {
284 org = screen_pos(vc, p, viewed);
285 col = p % maxcol;
286 p += maxcol - col;
287 while (this_round-- > 0) {
288 *con_buf0++ = (vcs_scr_readw(vc, org++) & 0xff);
289 if (++col == maxcol) {
290 org = screen_pos(vc, p, viewed);
291 col = 0;
292 p += maxcol;
293 }
294 }
295 } else {
296 if (p < HEADER_SIZE) {
297 size_t tmp_count;
298
299 con_buf0[0] = (char)vc->vc_rows;
300 con_buf0[1] = (char)vc->vc_cols;
301 getconsxy(vc, con_buf0 + 2);
302
303 con_buf_start += p;
304 this_round += p;
305 if (this_round > CON_BUF_SIZE) {
306 this_round = CON_BUF_SIZE;
307 orig_count = this_round - p;
308 }
309
310 tmp_count = HEADER_SIZE;
311 if (tmp_count > this_round)
312 tmp_count = this_round;
313
314 /* Advance state pointers and move on. */
315 this_round -= tmp_count;
316 p = HEADER_SIZE;
317 con_buf0 = con_buf + HEADER_SIZE;
318 /* If this_round >= 0, then p is even... */
319 } else if (p & 1) {
320 /* Skip first byte for output if start address is odd
321 * Update region sizes up/down depending on free
322 * space in buffer.
323 */
324 con_buf_start++;
325 if (this_round < CON_BUF_SIZE)
326 this_round++;
327 else
328 orig_count--;
329 }
330 if (this_round > 0) {
331 unsigned short *tmp_buf = (unsigned short *)con_buf0;
332
333 p -= HEADER_SIZE;
334 p /= 2;
335 col = p % maxcol;
336
337 org = screen_pos(vc, p, viewed);
338 p += maxcol - col;
339
340 /* Buffer has even length, so we can always copy
341 * character + attribute. We do not copy last byte
342 * to userspace if this_round is odd.
343 */
344 this_round = (this_round + 1) >> 1;
345
346 while (this_round) {
347 *tmp_buf++ = vcs_scr_readw(vc, org++);
348 this_round --;
349 if (++col == maxcol) {
350 org = screen_pos(vc, p, viewed);
351 col = 0;
352 p += maxcol;
353 }
354 }
355 }
356 }
357
358 /* Finally, release the console semaphore while we push
359 * all the data to userspace from our temporary buffer.
360 *
361 * AKPM: Even though it's a semaphore, we should drop it because
362 * the pagefault handling code may want to call printk().
363 */
364
365 console_unlock();
366 ret = copy_to_user(buf, con_buf_start, orig_count);
367 console_lock();
368
369 if (ret) {
370 read += (orig_count - ret);
371 ret = -EFAULT;
372 break;
373 }
374 buf += orig_count;
375 pos += orig_count;
376 read += orig_count;
377 count -= orig_count;
378 }
379 *ppos += read;
380 if (read)
381 ret = read;
382 unlock_out:
383 console_unlock();
384 free_page((unsigned long) con_buf);
385 return ret;
386 }
387
388 static ssize_t
vcs_write(struct file * file,const char __user * buf,size_t count,loff_t * ppos)389 vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
390 {
391 struct inode *inode = file->f_path.dentry->d_inode;
392 unsigned int currcons = iminor(inode);
393 struct vc_data *vc;
394 long pos;
395 long attr, size, written;
396 char *con_buf0;
397 int col, maxcol, viewed;
398 u16 *org0 = NULL, *org = NULL;
399 size_t ret;
400 char *con_buf;
401
402 con_buf = (char *) __get_free_page(GFP_KERNEL);
403 if (!con_buf)
404 return -ENOMEM;
405
406 pos = *ppos;
407
408 /* Select the proper current console and verify
409 * sanity of the situation under the console lock.
410 */
411 console_lock();
412
413 attr = (currcons & 128);
414 ret = -ENXIO;
415 vc = vcs_vc(inode, &viewed);
416 if (!vc)
417 goto unlock_out;
418
419 size = vcs_size(inode);
420 ret = -EINVAL;
421 if (pos < 0 || pos > size)
422 goto unlock_out;
423 if (count > size - pos)
424 count = size - pos;
425 written = 0;
426 while (count) {
427 long this_round = count;
428 size_t orig_count;
429 long p;
430
431 if (this_round > CON_BUF_SIZE)
432 this_round = CON_BUF_SIZE;
433
434 /* Temporarily drop the console lock so that we can read
435 * in the write data from userspace safely.
436 */
437 console_unlock();
438 ret = copy_from_user(con_buf, buf, this_round);
439 console_lock();
440
441 if (ret) {
442 this_round -= ret;
443 if (!this_round) {
444 /* Abort loop if no data were copied. Otherwise
445 * fail with -EFAULT.
446 */
447 if (written)
448 break;
449 ret = -EFAULT;
450 goto unlock_out;
451 }
452 }
453
454 /* The vcs_size might have changed while we slept to grab
455 * the user buffer, so recheck.
456 * Return data written up to now on failure.
457 */
458 size = vcs_size(inode);
459 if (size < 0) {
460 if (written)
461 break;
462 ret = size;
463 goto unlock_out;
464 }
465 if (pos >= size)
466 break;
467 if (this_round > size - pos)
468 this_round = size - pos;
469
470 /* OK, now actually push the write to the console
471 * under the lock using the local kernel buffer.
472 */
473
474 con_buf0 = con_buf;
475 orig_count = this_round;
476 maxcol = vc->vc_cols;
477 p = pos;
478 if (!attr) {
479 org0 = org = screen_pos(vc, p, viewed);
480 col = p % maxcol;
481 p += maxcol - col;
482
483 while (this_round > 0) {
484 unsigned char c = *con_buf0++;
485
486 this_round--;
487 vcs_scr_writew(vc,
488 (vcs_scr_readw(vc, org) & 0xff00) | c, org);
489 org++;
490 if (++col == maxcol) {
491 org = screen_pos(vc, p, viewed);
492 col = 0;
493 p += maxcol;
494 }
495 }
496 } else {
497 if (p < HEADER_SIZE) {
498 char header[HEADER_SIZE];
499
500 getconsxy(vc, header + 2);
501 while (p < HEADER_SIZE && this_round > 0) {
502 this_round--;
503 header[p++] = *con_buf0++;
504 }
505 if (!viewed)
506 putconsxy(vc, header + 2);
507 }
508 p -= HEADER_SIZE;
509 col = (p/2) % maxcol;
510 if (this_round > 0) {
511 org0 = org = screen_pos(vc, p/2, viewed);
512 if ((p & 1) && this_round > 0) {
513 char c;
514
515 this_round--;
516 c = *con_buf0++;
517 #ifdef __BIG_ENDIAN
518 vcs_scr_writew(vc, c |
519 (vcs_scr_readw(vc, org) & 0xff00), org);
520 #else
521 vcs_scr_writew(vc, (c << 8) |
522 (vcs_scr_readw(vc, org) & 0xff), org);
523 #endif
524 org++;
525 p++;
526 if (++col == maxcol) {
527 org = screen_pos(vc, p/2, viewed);
528 col = 0;
529 }
530 }
531 p /= 2;
532 p += maxcol - col;
533 }
534 while (this_round > 1) {
535 unsigned short w;
536
537 w = get_unaligned(((unsigned short *)con_buf0));
538 vcs_scr_writew(vc, w, org++);
539 con_buf0 += 2;
540 this_round -= 2;
541 if (++col == maxcol) {
542 org = screen_pos(vc, p, viewed);
543 col = 0;
544 p += maxcol;
545 }
546 }
547 if (this_round > 0) {
548 unsigned char c;
549
550 c = *con_buf0++;
551 #ifdef __BIG_ENDIAN
552 vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff) | (c << 8), org);
553 #else
554 vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff00) | c, org);
555 #endif
556 }
557 }
558 count -= orig_count;
559 written += orig_count;
560 buf += orig_count;
561 pos += orig_count;
562 if (org0)
563 update_region(vc, (unsigned long)(org0), org - org0);
564 }
565 *ppos += written;
566 ret = written;
567 if (written)
568 vcs_scr_updated(vc);
569
570 unlock_out:
571 console_unlock();
572 free_page((unsigned long) con_buf);
573 return ret;
574 }
575
576 static unsigned int
vcs_poll(struct file * file,poll_table * wait)577 vcs_poll(struct file *file, poll_table *wait)
578 {
579 struct vcs_poll_data *poll = vcs_poll_data_get(file);
580 int ret = DEFAULT_POLLMASK|POLLERR|POLLPRI;
581
582 if (poll) {
583 poll_wait(file, &poll->waitq, wait);
584 if (poll->seen_last_update)
585 ret = DEFAULT_POLLMASK;
586 }
587 return ret;
588 }
589
590 static int
vcs_fasync(int fd,struct file * file,int on)591 vcs_fasync(int fd, struct file *file, int on)
592 {
593 struct vcs_poll_data *poll = file->private_data;
594
595 if (!poll) {
596 /* don't allocate anything if all we want is disable fasync */
597 if (!on)
598 return 0;
599 poll = vcs_poll_data_get(file);
600 if (!poll)
601 return -ENOMEM;
602 }
603
604 return fasync_helper(fd, file, on, &poll->fasync);
605 }
606
607 static int
vcs_open(struct inode * inode,struct file * filp)608 vcs_open(struct inode *inode, struct file *filp)
609 {
610 unsigned int currcons = iminor(inode) & 127;
611 int ret = 0;
612
613 console_lock();
614 if(currcons && !vc_cons_allocated(currcons-1))
615 ret = -ENXIO;
616 console_unlock();
617 return ret;
618 }
619
vcs_release(struct inode * inode,struct file * file)620 static int vcs_release(struct inode *inode, struct file *file)
621 {
622 struct vcs_poll_data *poll = file->private_data;
623
624 if (poll)
625 vcs_poll_data_free(poll);
626 return 0;
627 }
628
629 static const struct file_operations vcs_fops = {
630 .llseek = vcs_lseek,
631 .read = vcs_read,
632 .write = vcs_write,
633 .poll = vcs_poll,
634 .fasync = vcs_fasync,
635 .open = vcs_open,
636 .release = vcs_release,
637 };
638
639 static struct class *vc_class;
640
vcs_make_sysfs(int index)641 void vcs_make_sysfs(int index)
642 {
643 device_create(vc_class, NULL, MKDEV(VCS_MAJOR, index + 1), NULL,
644 "vcs%u", index + 1);
645 device_create(vc_class, NULL, MKDEV(VCS_MAJOR, index + 129), NULL,
646 "vcsa%u", index + 1);
647 }
648
vcs_remove_sysfs(int index)649 void vcs_remove_sysfs(int index)
650 {
651 device_destroy(vc_class, MKDEV(VCS_MAJOR, index + 1));
652 device_destroy(vc_class, MKDEV(VCS_MAJOR, index + 129));
653 }
654
vcs_init(void)655 int __init vcs_init(void)
656 {
657 unsigned int i;
658
659 if (register_chrdev(VCS_MAJOR, "vcs", &vcs_fops))
660 panic("unable to get major %d for vcs device", VCS_MAJOR);
661 vc_class = class_create(THIS_MODULE, "vc");
662
663 device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 0), NULL, "vcs");
664 device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 128), NULL, "vcsa");
665 for (i = 0; i < MIN_NR_CONSOLES; i++)
666 vcs_make_sysfs(i);
667 return 0;
668 }
669