GNU Linux-libre 4.9.309-gnu1
[releases.git] / drivers / tty / vt / vc_screen.c
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
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
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 *
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_inode(file)) & 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*
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
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
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_inode(file));
188         console_unlock();
189         if (size < 0)
190                 return size;
191         return fixed_size_llseek(file, offset, orig, size);
192 }
193
194
195 static ssize_t
196 vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
197 {
198         struct inode *inode = file_inode(file);
199         unsigned int currcons = iminor(inode);
200         struct vc_data *vc;
201         struct vcs_poll_data *poll;
202         long pos;
203         long attr, read;
204         int col, maxcol, viewed;
205         unsigned short *org = NULL;
206         ssize_t ret;
207         char *con_buf;
208
209         con_buf = (char *) __get_free_page(GFP_KERNEL);
210         if (!con_buf)
211                 return -ENOMEM;
212
213         pos = *ppos;
214
215         /* Select the proper current console and verify
216          * sanity of the situation under the console lock.
217          */
218         console_lock();
219
220         attr = (currcons & 128);
221         ret = -ENXIO;
222         vc = vcs_vc(inode, &viewed);
223         if (!vc)
224                 goto unlock_out;
225
226         ret = -EINVAL;
227         if (pos < 0)
228                 goto unlock_out;
229         poll = file->private_data;
230         if (count && poll)
231                 poll->seen_last_update = true;
232         read = 0;
233         ret = 0;
234         while (count) {
235                 char *con_buf0, *con_buf_start;
236                 long this_round, size;
237                 ssize_t orig_count;
238                 long p = pos;
239
240                 /* Check whether we are above size each round,
241                  * as copy_to_user at the end of this loop
242                  * could sleep.
243                  */
244                 size = vcs_size(inode);
245                 if (size < 0) {
246                         if (read)
247                                 break;
248                         ret = size;
249                         goto unlock_out;
250                 }
251                 if (pos >= size)
252                         break;
253                 if (count > size - pos)
254                         count = size - pos;
255
256                 this_round = count;
257                 if (this_round > CON_BUF_SIZE)
258                         this_round = CON_BUF_SIZE;
259
260                 /* Perform the whole read into the local con_buf.
261                  * Then we can drop the console spinlock and safely
262                  * attempt to move it to userspace.
263                  */
264
265                 con_buf_start = con_buf0 = con_buf;
266                 orig_count = this_round;
267                 maxcol = vc->vc_cols;
268                 if (!attr) {
269                         org = screen_pos(vc, p, viewed);
270                         col = p % maxcol;
271                         p += maxcol - col;
272                         while (this_round-- > 0) {
273                                 *con_buf0++ = (vcs_scr_readw(vc, org++) & 0xff);
274                                 if (++col == maxcol) {
275                                         org = screen_pos(vc, p, viewed);
276                                         col = 0;
277                                         p += maxcol;
278                                 }
279                         }
280                 } else {
281                         if (p < HEADER_SIZE) {
282                                 size_t tmp_count;
283
284                                 con_buf0[0] = (char)vc->vc_rows;
285                                 con_buf0[1] = (char)vc->vc_cols;
286                                 getconsxy(vc, con_buf0 + 2);
287
288                                 con_buf_start += p;
289                                 this_round += p;
290                                 if (this_round > CON_BUF_SIZE) {
291                                         this_round = CON_BUF_SIZE;
292                                         orig_count = this_round - p;
293                                 }
294
295                                 tmp_count = HEADER_SIZE;
296                                 if (tmp_count > this_round)
297                                         tmp_count = this_round;
298
299                                 /* Advance state pointers and move on. */
300                                 this_round -= tmp_count;
301                                 p = HEADER_SIZE;
302                                 con_buf0 = con_buf + HEADER_SIZE;
303                                 /* If this_round >= 0, then p is even... */
304                         } else if (p & 1) {
305                                 /* Skip first byte for output if start address is odd
306                                  * Update region sizes up/down depending on free
307                                  * space in buffer.
308                                  */
309                                 con_buf_start++;
310                                 if (this_round < CON_BUF_SIZE)
311                                         this_round++;
312                                 else
313                                         orig_count--;
314                         }
315                         if (this_round > 0) {
316                                 unsigned short *tmp_buf = (unsigned short *)con_buf0;
317
318                                 p -= HEADER_SIZE;
319                                 p /= 2;
320                                 col = p % maxcol;
321
322                                 org = screen_pos(vc, p, viewed);
323                                 p += maxcol - col;
324
325                                 /* Buffer has even length, so we can always copy
326                                  * character + attribute. We do not copy last byte
327                                  * to userspace if this_round is odd.
328                                  */
329                                 this_round = (this_round + 1) >> 1;
330
331                                 while (this_round) {
332                                         *tmp_buf++ = vcs_scr_readw(vc, org++);
333                                         this_round --;
334                                         if (++col == maxcol) {
335                                                 org = screen_pos(vc, p, viewed);
336                                                 col = 0;
337                                                 p += maxcol;
338                                         }
339                                 }
340                         }
341                 }
342
343                 /* Finally, release the console semaphore while we push
344                  * all the data to userspace from our temporary buffer.
345                  *
346                  * AKPM: Even though it's a semaphore, we should drop it because
347                  * the pagefault handling code may want to call printk().
348                  */
349
350                 console_unlock();
351                 ret = copy_to_user(buf, con_buf_start, orig_count);
352                 console_lock();
353
354                 if (ret) {
355                         read += (orig_count - ret);
356                         ret = -EFAULT;
357                         break;
358                 }
359                 buf += orig_count;
360                 pos += orig_count;
361                 read += orig_count;
362                 count -= orig_count;
363         }
364         *ppos += read;
365         if (read)
366                 ret = read;
367 unlock_out:
368         console_unlock();
369         free_page((unsigned long) con_buf);
370         return ret;
371 }
372
373 static ssize_t
374 vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
375 {
376         struct inode *inode = file_inode(file);
377         unsigned int currcons = iminor(inode);
378         struct vc_data *vc;
379         long pos;
380         long attr, size, written;
381         char *con_buf0;
382         int col, maxcol, viewed;
383         u16 *org0 = NULL, *org = NULL;
384         size_t ret;
385         char *con_buf;
386
387         con_buf = (char *) __get_free_page(GFP_KERNEL);
388         if (!con_buf)
389                 return -ENOMEM;
390
391         pos = *ppos;
392
393         /* Select the proper current console and verify
394          * sanity of the situation under the console lock.
395          */
396         console_lock();
397
398         attr = (currcons & 128);
399         ret = -ENXIO;
400         vc = vcs_vc(inode, &viewed);
401         if (!vc)
402                 goto unlock_out;
403
404         size = vcs_size(inode);
405         ret = -EINVAL;
406         if (pos < 0 || pos > size)
407                 goto unlock_out;
408         if (count > size - pos)
409                 count = size - pos;
410         written = 0;
411         while (count) {
412                 long this_round = count;
413                 size_t orig_count;
414                 long p;
415
416                 if (this_round > CON_BUF_SIZE)
417                         this_round = CON_BUF_SIZE;
418
419                 /* Temporarily drop the console lock so that we can read
420                  * in the write data from userspace safely.
421                  */
422                 console_unlock();
423                 ret = copy_from_user(con_buf, buf, this_round);
424                 console_lock();
425
426                 if (ret) {
427                         this_round -= ret;
428                         if (!this_round) {
429                                 /* Abort loop if no data were copied. Otherwise
430                                  * fail with -EFAULT.
431                                  */
432                                 if (written)
433                                         break;
434                                 ret = -EFAULT;
435                                 goto unlock_out;
436                         }
437                 }
438
439                 /* The vcs_size might have changed while we slept to grab
440                  * the user buffer, so recheck.
441                  * Return data written up to now on failure.
442                  */
443                 size = vcs_size(inode);
444                 if (size < 0) {
445                         if (written)
446                                 break;
447                         ret = size;
448                         goto unlock_out;
449                 }
450                 if (pos >= size)
451                         break;
452                 if (this_round > size - pos)
453                         this_round = size - pos;
454
455                 /* OK, now actually push the write to the console
456                  * under the lock using the local kernel buffer.
457                  */
458
459                 con_buf0 = con_buf;
460                 orig_count = this_round;
461                 maxcol = vc->vc_cols;
462                 p = pos;
463                 if (!attr) {
464                         org0 = org = screen_pos(vc, p, viewed);
465                         col = p % maxcol;
466                         p += maxcol - col;
467
468                         while (this_round > 0) {
469                                 unsigned char c = *con_buf0++;
470
471                                 this_round--;
472                                 vcs_scr_writew(vc,
473                                                (vcs_scr_readw(vc, org) & 0xff00) | c, org);
474                                 org++;
475                                 if (++col == maxcol) {
476                                         org = screen_pos(vc, p, viewed);
477                                         col = 0;
478                                         p += maxcol;
479                                 }
480                         }
481                 } else {
482                         if (p < HEADER_SIZE) {
483                                 char header[HEADER_SIZE];
484
485                                 getconsxy(vc, header + 2);
486                                 while (p < HEADER_SIZE && this_round > 0) {
487                                         this_round--;
488                                         header[p++] = *con_buf0++;
489                                 }
490                                 if (!viewed)
491                                         putconsxy(vc, header + 2);
492                         }
493                         p -= HEADER_SIZE;
494                         col = (p/2) % maxcol;
495                         if (this_round > 0) {
496                                 org0 = org = screen_pos(vc, p/2, viewed);
497                                 if ((p & 1) && this_round > 0) {
498                                         char c;
499
500                                         this_round--;
501                                         c = *con_buf0++;
502 #ifdef __BIG_ENDIAN
503                                         vcs_scr_writew(vc, c |
504                                              (vcs_scr_readw(vc, org) & 0xff00), org);
505 #else
506                                         vcs_scr_writew(vc, (c << 8) |
507                                              (vcs_scr_readw(vc, org) & 0xff), org);
508 #endif
509                                         org++;
510                                         p++;
511                                         if (++col == maxcol) {
512                                                 org = screen_pos(vc, p/2, viewed);
513                                                 col = 0;
514                                         }
515                                 }
516                                 p /= 2;
517                                 p += maxcol - col;
518                         }
519                         while (this_round > 1) {
520                                 unsigned short w;
521
522                                 w = get_unaligned(((unsigned short *)con_buf0));
523                                 vcs_scr_writew(vc, w, org++);
524                                 con_buf0 += 2;
525                                 this_round -= 2;
526                                 if (++col == maxcol) {
527                                         org = screen_pos(vc, p, viewed);
528                                         col = 0;
529                                         p += maxcol;
530                                 }
531                         }
532                         if (this_round > 0) {
533                                 unsigned char c;
534
535                                 c = *con_buf0++;
536 #ifdef __BIG_ENDIAN
537                                 vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff) | (c << 8), org);
538 #else
539                                 vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff00) | c, org);
540 #endif
541                         }
542                 }
543                 count -= orig_count;
544                 written += orig_count;
545                 buf += orig_count;
546                 pos += orig_count;
547                 if (org0)
548                         update_region(vc, (unsigned long)(org0), org - org0);
549         }
550         *ppos += written;
551         ret = written;
552         if (written)
553                 vcs_scr_updated(vc);
554
555 unlock_out:
556         console_unlock();
557         free_page((unsigned long) con_buf);
558         return ret;
559 }
560
561 static unsigned int
562 vcs_poll(struct file *file, poll_table *wait)
563 {
564         struct vcs_poll_data *poll = vcs_poll_data_get(file);
565         int ret = DEFAULT_POLLMASK|POLLERR|POLLPRI;
566
567         if (poll) {
568                 poll_wait(file, &poll->waitq, wait);
569                 if (poll->seen_last_update)
570                         ret = DEFAULT_POLLMASK;
571         }
572         return ret;
573 }
574
575 static int
576 vcs_fasync(int fd, struct file *file, int on)
577 {
578         struct vcs_poll_data *poll = file->private_data;
579
580         if (!poll) {
581                 /* don't allocate anything if all we want is disable fasync */
582                 if (!on)
583                         return 0;
584                 poll = vcs_poll_data_get(file);
585                 if (!poll)
586                         return -ENOMEM;
587         }
588
589         return fasync_helper(fd, file, on, &poll->fasync);
590 }
591
592 static int
593 vcs_open(struct inode *inode, struct file *filp)
594 {
595         unsigned int currcons = iminor(inode) & 127;
596         int ret = 0;
597         
598         console_lock();
599         if(currcons && !vc_cons_allocated(currcons-1))
600                 ret = -ENXIO;
601         console_unlock();
602         return ret;
603 }
604
605 static int vcs_release(struct inode *inode, struct file *file)
606 {
607         struct vcs_poll_data *poll = file->private_data;
608
609         if (poll)
610                 vcs_poll_data_free(poll);
611         return 0;
612 }
613
614 static const struct file_operations vcs_fops = {
615         .llseek         = vcs_lseek,
616         .read           = vcs_read,
617         .write          = vcs_write,
618         .poll           = vcs_poll,
619         .fasync         = vcs_fasync,
620         .open           = vcs_open,
621         .release        = vcs_release,
622 };
623
624 static struct class *vc_class;
625
626 void vcs_make_sysfs(int index)
627 {
628         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, index + 1), NULL,
629                       "vcs%u", index + 1);
630         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, index + 129), NULL,
631                       "vcsa%u", index + 1);
632 }
633
634 void vcs_remove_sysfs(int index)
635 {
636         device_destroy(vc_class, MKDEV(VCS_MAJOR, index + 1));
637         device_destroy(vc_class, MKDEV(VCS_MAJOR, index + 129));
638 }
639
640 int __init vcs_init(void)
641 {
642         unsigned int i;
643
644         if (register_chrdev(VCS_MAJOR, "vcs", &vcs_fops))
645                 panic("unable to get major %d for vcs device", VCS_MAJOR);
646         vc_class = class_create(THIS_MODULE, "vc");
647
648         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 0), NULL, "vcs");
649         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 128), NULL, "vcsa");
650         for (i = 0; i < MIN_NR_CONSOLES; i++)
651                 vcs_make_sysfs(i);
652         return 0;
653 }