drivers/tty/vt/vc_screen.c

   1 /*
   2  * Provide access to virtual console memory.
   3  * /dev/vcs0: the screen as it is being viewed right now (possibly scrolled)
   4  * /dev/vcsN: the screen of /dev/ttyN (1 <= N <= 63)
   5  *            [minor: N]
   6  *
   7  * /dev/vcsaN: idem, but including attributes, and prefixed with
   8  *      the 4 bytes lines,columns,x,y (as screendump used to give).
   9  *      Attribute/character pair is in native endianity.
  10  *            [minor: N+128]
  11  *
  12  * This replaces screendump and part of selection, so that the system
  13  * administrator can control access using file system permissions.
  14  *
  15  * aeb@cwi.nl - efter Friedas begravelse - 950211
  16  *
  17  * machek@k332.feld.cvut.cz - modified not to send characters to wrong console
  18  *       - fixed some fatal off-by-one bugs (0-- no longer == -1 -> looping and looping and looping...)
  19  *       - making it shorter - scr_readw are macros which expand in PRETTY long code
  20  */
  21
  22 #include <linux/kernel.h>
  23 #include <linux/major.h>
  24 #include <linux/errno.h>
  25 #include <linux/export.h>
  26 #include <linux/tty.h>
  27 #include <linux/interrupt.h>
  28 #include <linux/mm.h>
  29 #include <linux/init.h>
  30 #include <linux/vt_kern.h>
  31 #include <linux/selection.h>
  32 #include <linux/kbd_kern.h>
  33 #include <linux/console.h>
  34 #include <linux/device.h>
  35 #include <linux/sched.h>
  36 #include <linux/fs.h>
  37 #include <linux/poll.h>
  38 #include <linux/signal.h>
  39 #include <linux/slab.h>
  40 #include <linux/notifier.h>
  41
  42 #include <asm/uaccess.h>
  43 #include <asm/byteorder.h>
  44 #include <asm/unaligned.h>
  45
  46 #undef attr
  47 #undef org
  48 #undef addr
  49 #define HEADER_SIZE     4
  50
  51 #define CON_BUF_SIZE (CONFIG_BASE_SMALL ? 256 : PAGE_SIZE)
  52
  53 struct vcs_poll_data {
  54         struct notifier_block notifier;
  55         unsigned int cons_num;
  56         bool seen_last_update;
  57         wait_queue_head_t waitq;
  58         struct fasync_struct *fasync;
  59 };
  60
  61 static int
  62 vcs_notifier(struct notifier_block *nb, unsigned long code, void *_param)
  63 {
  64         struct vt_notifier_param *param = _param;
  65         struct vc_data *vc = param->vc;
  66         struct vcs_poll_data *poll =
  67                 container_of(nb, struct vcs_poll_data, notifier);
  68         int currcons = poll->cons_num;
  69
  70         if (code != VT_UPDATE)
  71                 return NOTIFY_DONE;
  72
  73         if (currcons == 0)
  74                 currcons = fg_console;
  75         else
  76                 currcons--;
  77         if (currcons != vc->vc_num)
  78                 return NOTIFY_DONE;
  79
  80         poll->seen_last_update = false;
  81         wake_up_interruptible(&poll->waitq);
  82         kill_fasync(&poll->fasync, SIGIO, POLL_IN);
  83         return NOTIFY_OK;
  84 }
  85
  86 static void
  87 vcs_poll_data_free(struct vcs_poll_data *poll)
  88 {
  89         unregister_vt_notifier(&poll->notifier);
  90         kfree(poll);
  91 }
  92
  93 static struct vcs_poll_data *
  94 vcs_poll_data_get(struct file *file)
  95 {
  96         struct vcs_poll_data *poll = file->private_data, *kill = NULL;
  97
  98         if (poll)
  99                 return poll;
 100
 101         poll = kzalloc(sizeof(*poll), GFP_KERNEL);
 102         if (!poll)
 103                 return NULL;
 104         poll->cons_num = iminor(file_inode(file)) & 127;
 105         init_waitqueue_head(&poll->waitq);
 106         poll->notifier.notifier_call = vcs_notifier;
 107         if (register_vt_notifier(&poll->notifier) != 0) {
 108                 kfree(poll);
 109                 return NULL;
 110         }
 111
 112         /*
 113          * This code may be called either through ->poll() or ->fasync().
 114          * If we have two threads using the same file descriptor, they could
 115          * both enter this function, both notice that the structure hasn't
 116          * been allocated yet and go ahead allocating it in parallel, but
 117          * only one of them must survive and be shared otherwise we'd leak
 118          * memory with a dangling notifier callback.
 119          */
 120         spin_lock(&file->f_lock);
 121         if (!file->private_data) {
 122                 file->private_data = poll;
 123         } else {
 124                 /* someone else raced ahead of us */
 125                 kill = poll;
 126                 poll = file->private_data;
 127         }
 128         spin_unlock(&file->f_lock);
 129         if (kill)
 130                 vcs_poll_data_free(kill);
 131
 132         return poll;
 133 }
 134
 135 /*
 136  * Returns VC for inode.
 137  * Must be called with console_lock.
 138  */
 139 static struct vc_data*
 140 vcs_vc(struct inode *inode, int *viewed)
 141 {
 142         unsigned int currcons = iminor(inode) & 127;
 143
 144         WARN_CONSOLE_UNLOCKED();
 145
 146         if (currcons == 0) {
 147                 currcons = fg_console;
 148                 if (viewed)
 149                         *viewed = 1;
 150         } else {
 151                 currcons--;
 152                 if (viewed)
 153                         *viewed = 0;
 154         }
 155         return vc_cons[currcons].d;
 156 }
 157
 158 /*
 159  * Returns size for VC carried by inode.
 160  * Must be called with console_lock.
 161  */
 162 static int
 163 vcs_size(struct inode *inode)
 164 {
 165         int size;
 166         int minor = iminor(inode);
 167         struct vc_data *vc;
 168
 169         WARN_CONSOLE_UNLOCKED();
 170
 171         vc = vcs_vc(inode, NULL);
 172         if (!vc)
 173                 return -ENXIO;
 174
 175         size = vc->vc_rows * vc->vc_cols;
 176
 177         if (minor & 128)
 178                 size = 2*size + HEADER_SIZE;
 179         return size;
 180 }
 181
 182 static loff_t vcs_lseek(struct file *file, loff_t offset, int orig)
 183 {
 184         int size;
 185
 186         console_lock();
 187         size = vcs_size(file_inode(file));
 188         console_unlock();
 189         if (size < 0)
 190                 return size;
 191         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_inode(file);
 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_inode(file);
 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 }