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 <linux/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 }