drivers/char/vc_screen.c

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