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;
  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                 vcs_poll_data_free(poll);
 126                 poll = file->private_data;
 127         }
 128         spin_unlock(&file->f_lock);
 129
 130         return poll;
 131 }
 132
 133 /*
 134  * Returns VC for inode.
 135  * Must be called with console_lock.
 136  */
 137 static struct vc_data*
 138 vcs_vc(struct inode *inode, int *viewed)
 139 {
 140         unsigned int currcons = iminor(inode) & 127;
 141
 142         WARN_CONSOLE_UNLOCKED();
 143
 144         if (currcons == 0) {
 145                 currcons = fg_console;
 146                 if (viewed)
 147                         *viewed = 1;
 148         } else {
 149                 currcons--;
 150                 if (viewed)
 151                         *viewed = 0;
 152         }
 153         return vc_cons[currcons].d;
 154 }
 155
 156 /*
 157  * Returns size for VC carried by inode.
 158  * Must be called with console_lock.
 159  */
 160 static int
 161 vcs_size(struct inode *inode)
 162 {
 163         int size;
 164         int minor = iminor(inode);
 165         struct vc_data *vc;
 166
 167         WARN_CONSOLE_UNLOCKED();
 168
 169         vc = vcs_vc(inode, NULL);
 170         if (!vc)
 171                 return -ENXIO;
 172
 173         size = vc->vc_rows * vc->vc_cols;
 174
 175         if (minor & 128)
 176                 size = 2*size + HEADER_SIZE;
 177         return size;
 178 }
 179
 180 static loff_t vcs_lseek(struct file *file, loff_t offset, int orig)
 181 {
 182         int size;
 183
 184         console_lock();
 185         size = vcs_size(file->f_path.dentry->d_inode);
 186         console_unlock();
 187         if (size < 0)
 188                 return size;
 189         switch (orig) {
 190                 default:
 191                         return -EINVAL;
 192                 case 2:
 193                         offset += size;
 194                         break;
 195                 case 1:
 196                         offset += file->f_pos;
 197                 case 0:
 198                         break;
 199         }
 200         if (offset < 0 || offset > size) {
 201                 return -EINVAL;
 202         }
 203         file->f_pos = offset;
 204         return file->f_pos;
 205 }
 206
 207
 208 static ssize_t
 209 vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 210 {
 211         struct inode *inode = file->f_path.dentry->d_inode;
 212         unsigned int currcons = iminor(inode);
 213         struct vc_data *vc;
 214         struct vcs_poll_data *poll;
 215         long pos;
 216         long attr, read;
 217         int col, maxcol, viewed;
 218         unsigned short *org = NULL;
 219         ssize_t ret;
 220         char *con_buf;
 221
 222         con_buf = (char *) __get_free_page(GFP_KERNEL);
 223         if (!con_buf)
 224                 return -ENOMEM;
 225
 226         pos = *ppos;
 227
 228         /* Select the proper current console and verify
 229          * sanity of the situation under the console lock.
 230          */
 231         console_lock();
 232
 233         attr = (currcons & 128);
 234         ret = -ENXIO;
 235         vc = vcs_vc(inode, &viewed);
 236         if (!vc)
 237                 goto unlock_out;
 238
 239         ret = -EINVAL;
 240         if (pos < 0)
 241                 goto unlock_out;
 242         poll = file->private_data;
 243         if (count && poll)
 244                 poll->seen_last_update = true;
 245         read = 0;
 246         ret = 0;
 247         while (count) {
 248                 char *con_buf0, *con_buf_start;
 249                 long this_round, size;
 250                 ssize_t orig_count;
 251                 long p = pos;
 252
 253                 /* Check whether we are above size each round,
 254                  * as copy_to_user at the end of this loop
 255                  * could sleep.
 256                  */
 257                 size = vcs_size(inode);
 258                 if (size < 0) {
 259                         if (read)
 260                                 break;
 261                         ret = size;
 262                         goto unlock_out;
 263                 }
 264                 if (pos >= size)
 265                         break;
 266                 if (count > size - pos)
 267                         count = size - pos;
 268
 269                 this_round = count;
 270                 if (this_round > CON_BUF_SIZE)
 271                         this_round = CON_BUF_SIZE;
 272
 273                 /* Perform the whole read into the local con_buf.
 274                  * Then we can drop the console spinlock and safely
 275                  * attempt to move it to userspace.
 276                  */
 277
 278                 con_buf_start = con_buf0 = con_buf;
 279                 orig_count = this_round;
 280                 maxcol = vc->vc_cols;
 281                 if (!attr) {
 282                         org = screen_pos(vc, p, viewed);
 283                         col = p % maxcol;
 284                         p += maxcol - col;
 285                         while (this_round-- > 0) {
 286                                 *con_buf0++ = (vcs_scr_readw(vc, org++) & 0xff);
 287                                 if (++col == maxcol) {
 288                                         org = screen_pos(vc, p, viewed);
 289                                         col = 0;
 290                                         p += maxcol;
 291                                 }
 292                         }
 293                 } else {
 294                         if (p < HEADER_SIZE) {
 295                                 size_t tmp_count;
 296
 297                                 con_buf0[0] = (char)vc->vc_rows;
 298                                 con_buf0[1] = (char)vc->vc_cols;
 299                                 getconsxy(vc, con_buf0 + 2);
 300
 301                                 con_buf_start += p;
 302                                 this_round += p;
 303                                 if (this_round > CON_BUF_SIZE) {
 304                                         this_round = CON_BUF_SIZE;
 305                                         orig_count = this_round - p;
 306                                 }
 307
 308                                 tmp_count = HEADER_SIZE;
 309                                 if (tmp_count > this_round)
 310                                         tmp_count = this_round;
 311
 312                                 /* Advance state pointers and move on. */
 313                                 this_round -= tmp_count;
 314                                 p = HEADER_SIZE;
 315                                 con_buf0 = con_buf + HEADER_SIZE;
 316                                 /* If this_round >= 0, then p is even... */
 317                         } else if (p & 1) {
 318                                 /* Skip first byte for output if start address is odd
 319                                  * Update region sizes up/down depending on free
 320                                  * space in buffer.
 321                                  */
 322                                 con_buf_start++;
 323                                 if (this_round < CON_BUF_SIZE)
 324                                         this_round++;
 325                                 else
 326                                         orig_count--;
 327                         }
 328                         if (this_round > 0) {
 329                                 unsigned short *tmp_buf = (unsigned short *)con_buf0;
 330
 331                                 p -= HEADER_SIZE;
 332                                 p /= 2;
 333                                 col = p % maxcol;
 334
 335                                 org = screen_pos(vc, p, viewed);
 336                                 p += maxcol - col;
 337
 338                                 /* Buffer has even length, so we can always copy
 339                                  * character + attribute. We do not copy last byte
 340                                  * to userspace if this_round is odd.
 341                                  */
 342                                 this_round = (this_round + 1) >> 1;
 343
 344                                 while (this_round) {
 345                                         *tmp_buf++ = vcs_scr_readw(vc, org++);
 346                                         this_round --;
 347                                         if (++col == maxcol) {
 348                                                 org = screen_pos(vc, p, viewed);
 349                                                 col = 0;
 350                                                 p += maxcol;
 351                                         }
 352                                 }
 353                         }
 354                 }
 355
 356                 /* Finally, release the console semaphore while we push
 357                  * all the data to userspace from our temporary buffer.
 358                  *
 359                  * AKPM: Even though it's a semaphore, we should drop it because
 360                  * the pagefault handling code may want to call printk().
 361                  */
 362
 363                 console_unlock();
 364                 ret = copy_to_user(buf, con_buf_start, orig_count);
 365                 console_lock();
 366
 367                 if (ret) {
 368                         read += (orig_count - ret);
 369                         ret = -EFAULT;
 370                         break;
 371                 }
 372                 buf += orig_count;
 373                 pos += orig_count;
 374                 read += orig_count;
 375                 count -= orig_count;
 376         }
 377         *ppos += read;
 378         if (read)
 379                 ret = read;
 380 unlock_out:
 381         console_unlock();
 382         free_page((unsigned long) con_buf);
 383         return ret;
 384 }
 385
 386 static ssize_t
 387 vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 388 {
 389         struct inode *inode = file->f_path.dentry->d_inode;
 390         unsigned int currcons = iminor(inode);
 391         struct vc_data *vc;
 392         long pos;
 393         long attr, size, written;
 394         char *con_buf0;
 395         int col, maxcol, viewed;
 396         u16 *org0 = NULL, *org = NULL;
 397         size_t ret;
 398         char *con_buf;
 399
 400         con_buf = (char *) __get_free_page(GFP_KERNEL);
 401         if (!con_buf)
 402                 return -ENOMEM;
 403
 404         pos = *ppos;
 405
 406         /* Select the proper current console and verify
 407          * sanity of the situation under the console lock.
 408          */
 409         console_lock();
 410
 411         attr = (currcons & 128);
 412         ret = -ENXIO;
 413         vc = vcs_vc(inode, &viewed);
 414         if (!vc)
 415                 goto unlock_out;
 416
 417         size = vcs_size(inode);
 418         ret = -EINVAL;
 419         if (pos < 0 || pos > size)
 420                 goto unlock_out;
 421         if (count > size - pos)
 422                 count = size - pos;
 423         written = 0;
 424         while (count) {
 425                 long this_round = count;
 426                 size_t orig_count;
 427                 long p;
 428
 429                 if (this_round > CON_BUF_SIZE)
 430                         this_round = CON_BUF_SIZE;
 431
 432                 /* Temporarily drop the console lock so that we can read
 433                  * in the write data from userspace safely.
 434                  */
 435                 console_unlock();
 436                 ret = copy_from_user(con_buf, buf, this_round);
 437                 console_lock();
 438
 439                 if (ret) {
 440                         this_round -= ret;
 441                         if (!this_round) {
 442                                 /* Abort loop if no data were copied. Otherwise
 443                                  * fail with -EFAULT.
 444                                  */
 445                                 if (written)
 446                                         break;
 447                                 ret = -EFAULT;
 448                                 goto unlock_out;
 449                         }
 450                 }
 451
 452                 /* The vcs_size might have changed while we slept to grab
 453                  * the user buffer, so recheck.
 454                  * Return data written up to now on failure.
 455                  */
 456                 size = vcs_size(inode);
 457                 if (size < 0) {
 458                         if (written)
 459                                 break;
 460                         ret = size;
 461                         goto unlock_out;
 462                 }
 463                 if (pos >= size)
 464                         break;
 465                 if (this_round > size - pos)
 466                         this_round = size - pos;
 467
 468                 /* OK, now actually push the write to the console
 469                  * under the lock using the local kernel buffer.
 470                  */
 471
 472                 con_buf0 = con_buf;
 473                 orig_count = this_round;
 474                 maxcol = vc->vc_cols;
 475                 p = pos;
 476                 if (!attr) {
 477                         org0 = org = screen_pos(vc, p, viewed);
 478                         col = p % maxcol;
 479                         p += maxcol - col;
 480
 481                         while (this_round > 0) {
 482                                 unsigned char c = *con_buf0++;
 483
 484                                 this_round--;
 485                                 vcs_scr_writew(vc,
 486                                                (vcs_scr_readw(vc, org) & 0xff00) | c, org);
 487                                 org++;
 488                                 if (++col == maxcol) {
 489                                         org = screen_pos(vc, p, viewed);
 490                                         col = 0;
 491                                         p += maxcol;
 492                                 }
 493                         }
 494                 } else {
 495                         if (p < HEADER_SIZE) {
 496                                 char header[HEADER_SIZE];
 497
 498                                 getconsxy(vc, header + 2);
 499                                 while (p < HEADER_SIZE && this_round > 0) {
 500                                         this_round--;
 501                                         header[p++] = *con_buf0++;
 502                                 }
 503                                 if (!viewed)
 504                                         putconsxy(vc, header + 2);
 505                         }
 506                         p -= HEADER_SIZE;
 507                         col = (p/2) % maxcol;
 508                         if (this_round > 0) {
 509                                 org0 = org = screen_pos(vc, p/2, viewed);
 510                                 if ((p & 1) && this_round > 0) {
 511                                         char c;
 512
 513                                         this_round--;
 514                                         c = *con_buf0++;
 515 #ifdef __BIG_ENDIAN
 516                                         vcs_scr_writew(vc, c |
 517                                              (vcs_scr_readw(vc, org) & 0xff00), org);
 518 #else
 519                                         vcs_scr_writew(vc, (c << 8) |
 520                                              (vcs_scr_readw(vc, org) & 0xff), org);
 521 #endif
 522                                         org++;
 523                                         p++;
 524                                         if (++col == maxcol) {
 525                                                 org = screen_pos(vc, p/2, viewed);
 526                                                 col = 0;
 527                                         }
 528                                 }
 529                                 p /= 2;
 530                                 p += maxcol - col;
 531                         }
 532                         while (this_round > 1) {
 533                                 unsigned short w;
 534
 535                                 w = get_unaligned(((unsigned short *)con_buf0));
 536                                 vcs_scr_writew(vc, w, org++);
 537                                 con_buf0 += 2;
 538                                 this_round -= 2;
 539                                 if (++col == maxcol) {
 540                                         org = screen_pos(vc, p, viewed);
 541                                         col = 0;
 542                                         p += maxcol;
 543                                 }
 544                         }
 545                         if (this_round > 0) {
 546                                 unsigned char c;
 547
 548                                 c = *con_buf0++;
 549 #ifdef __BIG_ENDIAN
 550                                 vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff) | (c << 8), org);
 551 #else
 552                                 vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff00) | c, org);
 553 #endif
 554                         }
 555                 }
 556                 count -= orig_count;
 557                 written += orig_count;
 558                 buf += orig_count;
 559                 pos += orig_count;
 560                 if (org0)
 561                         update_region(vc, (unsigned long)(org0), org - org0);
 562         }
 563         *ppos += written;
 564         ret = written;
 565         if (written)
 566                 vcs_scr_updated(vc);
 567
 568 unlock_out:
 569         console_unlock();
 570         free_page((unsigned long) con_buf);
 571         return ret;
 572 }
 573
 574 static unsigned int
 575 vcs_poll(struct file *file, poll_table *wait)
 576 {
 577         struct vcs_poll_data *poll = vcs_poll_data_get(file);
 578         int ret = DEFAULT_POLLMASK|POLLERR|POLLPRI;
 579
 580         if (poll) {
 581                 poll_wait(file, &poll->waitq, wait);
 582                 if (poll->seen_last_update)
 583                         ret = DEFAULT_POLLMASK;
 584         }
 585         return ret;
 586 }
 587
 588 static int
 589 vcs_fasync(int fd, struct file *file, int on)
 590 {
 591         struct vcs_poll_data *poll = file->private_data;
 592
 593         if (!poll) {
 594                 /* don't allocate anything if all we want is disable fasync */
 595                 if (!on)
 596                         return 0;
 597                 poll = vcs_poll_data_get(file);
 598                 if (!poll)
 599                         return -ENOMEM;
 600         }
 601
 602         return fasync_helper(fd, file, on, &poll->fasync);
 603 }
 604
 605 static int
 606 vcs_open(struct inode *inode, struct file *filp)
 607 {
 608         unsigned int currcons = iminor(inode) & 127;
 609         int ret = 0;
 610
 611         tty_lock();
 612         if(currcons && !vc_cons_allocated(currcons-1))
 613                 ret = -ENXIO;
 614         tty_unlock();
 615         return ret;
 616 }
 617
 618 static int vcs_release(struct inode *inode, struct file *file)
 619 {
 620         struct vcs_poll_data *poll = file->private_data;
 621
 622         if (poll)
 623                 vcs_poll_data_free(poll);
 624         return 0;
 625 }
 626
 627 static const struct file_operations vcs_fops = {
 628         .llseek         = vcs_lseek,
 629         .read           = vcs_read,
 630         .write          = vcs_write,
 631         .poll           = vcs_poll,
 632         .fasync         = vcs_fasync,
 633         .open           = vcs_open,
 634         .release        = vcs_release,
 635 };
 636
 637 static struct class *vc_class;
 638
 639 void vcs_make_sysfs(int index)
 640 {
 641         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, index + 1), NULL,
 642                       "vcs%u", index + 1);
 643         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, index + 129), NULL,
 644                       "vcsa%u", index + 1);
 645 }
 646
 647 void vcs_remove_sysfs(int index)
 648 {
 649         device_destroy(vc_class, MKDEV(VCS_MAJOR, index + 1));
 650         device_destroy(vc_class, MKDEV(VCS_MAJOR, index + 129));
 651 }
 652
 653 int __init vcs_init(void)
 654 {
 655         unsigned int i;
 656
 657         if (register_chrdev(VCS_MAJOR, "vcs", &vcs_fops))
 658                 panic("unable to get major %d for vcs device", VCS_MAJOR);
 659         vc_class = class_create(THIS_MODULE, "vc");
 660
 661         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 0), NULL, "vcs");
 662         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 128), NULL, "vcsa");
 663         for (i = 0; i < MIN_NR_CONSOLES; i++)
 664                 vcs_make_sysfs(i);
 665         return 0;
 666 }