vt: synchronize_rcu() under spinlock is not nice...
[linux-2.6.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->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*
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->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
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
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
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
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
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
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
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
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
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 }