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/tty.h>
  26 #include <linux/interrupt.h>
  27 #include <linux/mm.h>
  28 #include <linux/init.h>
  29 #include <linux/vt_kern.h>
  30 #include <linux/selection.h>
  31 #include <linux/kbd_kern.h>
  32 #include <linux/console.h>
  33 #include <linux/device.h>
  34 #include <linux/sched.h>
  35 #include <linux/fs.h>
  36 #include <linux/poll.h>
  37 #include <linux/signal.h>
  38 #include <linux/slab.h>
  39 #include <linux/notifier.h>
  40
  41 #include <asm/uaccess.h>
  42 #include <asm/byteorder.h>
  43 #include <asm/unaligned.h>
  44
  45 #undef attr
  46 #undef org
  47 #undef addr
  48 #define HEADER_SIZE     4
  49
  50 #define CON_BUF_SIZE (CONFIG_BASE_SMALL ? 256 : PAGE_SIZE)
  51
  52 struct vcs_poll_data {
  53         struct notifier_block notifier;
  54         unsigned int cons_num;
  55         bool seen_last_update;
  56         wait_queue_head_t waitq;
  57         struct fasync_struct *fasync;
  58 };
  59
  60 static int
  61 vcs_notifier(struct notifier_block *nb, unsigned long code, void *_param)
  62 {
  63         struct vt_notifier_param *param = _param;
  64         struct vc_data *vc = param->vc;
  65         struct vcs_poll_data *poll =
  66                 container_of(nb, struct vcs_poll_data, notifier);
  67         int currcons = poll->cons_num;
  68
  69         if (code != VT_UPDATE)
  70                 return NOTIFY_DONE;
  71
  72         if (currcons == 0)
  73                 currcons = fg_console;
  74         else
  75                 currcons--;
  76         if (currcons != vc->vc_num)
  77                 return NOTIFY_DONE;
  78
  79         poll->seen_last_update = false;
  80         wake_up_interruptible(&poll->waitq);
  81         kill_fasync(&poll->fasync, SIGIO, POLL_IN);
  82         return NOTIFY_OK;
  83 }
  84
  85 static void
  86 vcs_poll_data_free(struct vcs_poll_data *poll)
  87 {
  88         unregister_vt_notifier(&poll->notifier);
  89         kfree(poll);
  90 }
  91
  92 static struct vcs_poll_data *
  93 vcs_poll_data_get(struct file *file)
  94 {
  95         struct vcs_poll_data *poll = file->private_data;
  96
  97         if (poll)
  98                 return poll;
  99
 100         poll = kzalloc(sizeof(*poll), GFP_KERNEL);
 101         if (!poll)
 102                 return NULL;
 103         poll->cons_num = iminor(file->f_path.dentry->d_inode) & 127;
 104         init_waitqueue_head(&poll->waitq);
 105         poll->notifier.notifier_call = vcs_notifier;
 106         if (register_vt_notifier(&poll->notifier) != 0) {
 107                 kfree(poll);
 108                 return NULL;
 109         }
 110
 111         /*
 112          * This code may be called either through ->poll() or ->fasync().
 113          * If we have two threads using the same file descriptor, they could
 114          * both enter this function, both notice that the structure hasn't
 115          * been allocated yet and go ahead allocating it in parallel, but
 116          * only one of them must survive and be shared otherwise we'd leak
 117          * memory with a dangling notifier callback.
 118          */
 119         spin_lock(&file->f_lock);
 120         if (!file->private_data) {
 121                 file->private_data = poll;
 122         } else {
 123                 /* someone else raced ahead of us */
 124                 vcs_poll_data_free(poll);
 125                 poll = file->private_data;
 126         }
 127         spin_unlock(&file->f_lock);
 128
 129         return poll;
 130 }
 131
 132 /*
 133  * Returns VC for inode.
 134  * Must be called with console_lock.
 135  */
 136 static struct vc_data*
 137 vcs_vc(struct inode *inode, int *viewed)
 138 {
 139         unsigned int currcons = iminor(inode) & 127;
 140
 141         WARN_CONSOLE_UNLOCKED();
 142
 143         if (currcons == 0) {
 144                 currcons = fg_console;
 145                 if (viewed)
 146                         *viewed = 1;
 147         } else {
 148                 currcons--;
 149                 if (viewed)
 150                         *viewed = 0;
 151         }
 152         return vc_cons[currcons].d;
 153 }
 154
 155 /*
 156  * Returns size for VC carried by inode.
 157  * Must be called with console_lock.
 158  */
 159 static int
 160 vcs_size(struct inode *inode)
 161 {
 162         int size;
 163         int minor = iminor(inode);
 164         struct vc_data *vc;
 165
 166         WARN_CONSOLE_UNLOCKED();
 167
 168         vc = vcs_vc(inode, NULL);
 169         if (!vc)
 170                 return -ENXIO;
 171
 172         size = vc->vc_rows * vc->vc_cols;
 173
 174         if (minor & 128)
 175                 size = 2*size + HEADER_SIZE;
 176         return size;
 177 }
 178
 179 static loff_t vcs_lseek(struct file *file, loff_t offset, int orig)
 180 {
 181         int size;
 182
 183         console_lock();
 184         size = vcs_size(file->f_path.dentry->d_inode);
 185         console_unlock();
 186         if (size < 0)
 187                 return size;
 188         switch (orig) {
 189                 default:
 190                         return -EINVAL;
 191                 case 2:
 192                         offset += size;
 193                         break;
 194                 case 1:
 195                         offset += file->f_pos;
 196                 case 0:
 197                         break;
 198         }
 199         if (offset < 0 || offset > size) {
 200                 return -EINVAL;
 201         }
 202         file->f_pos = offset;
 203         return file->f_pos;
 204 }
 205
 206
 207 static ssize_t
 208 vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 209 {
 210         struct inode *inode = file->f_path.dentry->d_inode;
 211         unsigned int currcons = iminor(inode);
 212         struct vc_data *vc;
 213         struct vcs_poll_data *poll;
 214         long pos;
 215         long attr, read;
 216         int col, maxcol, viewed;
 217         unsigned short *org = NULL;
 218         ssize_t ret;
 219         char *con_buf;
 220
 221         con_buf = (char *) __get_free_page(GFP_KERNEL);
 222         if (!con_buf)
 223                 return -ENOMEM;
 224
 225         pos = *ppos;
 226
 227         /* Select the proper current console and verify
 228          * sanity of the situation under the console lock.
 229          */
 230         console_lock();
 231
 232         attr = (currcons & 128);
 233         ret = -ENXIO;
 234         vc = vcs_vc(inode, &viewed);
 235         if (!vc)
 236                 goto unlock_out;
 237
 238         ret = -EINVAL;
 239         if (pos < 0)
 240                 goto unlock_out;
 241         poll = file->private_data;
 242         if (count && poll)
 243                 poll->seen_last_update = true;
 244         read = 0;
 245         ret = 0;
 246         while (count) {
 247                 char *con_buf0, *con_buf_start;
 248                 long this_round, size;
 249                 ssize_t orig_count;
 250                 long p = pos;
 251
 252                 /* Check whether we are above size each round,
 253                  * as copy_to_user at the end of this loop
 254                  * could sleep.
 255                  */
 256                 size = vcs_size(inode);
 257                 if (size < 0) {
 258                         if (read)
 259                                 break;
 260                         ret = size;
 261                         goto unlock_out;
 262                 }
 263                 if (pos >= size)
 264                         break;
 265                 if (count > size - pos)
 266                         count = size - pos;
 267
 268                 this_round = count;
 269                 if (this_round > CON_BUF_SIZE)
 270                         this_round = CON_BUF_SIZE;
 271
 272                 /* Perform the whole read into the local con_buf.
 273                  * Then we can drop the console spinlock and safely
 274                  * attempt to move it to userspace.
 275                  */
 276
 277                 con_buf_start = con_buf0 = con_buf;
 278                 orig_count = this_round;
 279                 maxcol = vc->vc_cols;
 280                 if (!attr) {
 281                         org = screen_pos(vc, p, viewed);
 282                         col = p % maxcol;
 283                         p += maxcol - col;
 284                         while (this_round-- > 0) {
 285                                 *con_buf0++ = (vcs_scr_readw(vc, org++) & 0xff);
 286                                 if (++col == maxcol) {
 287                                         org = screen_pos(vc, p, viewed);
 288                                         col = 0;
 289                                         p += maxcol;
 290                                 }
 291                         }
 292                 } else {
 293                         if (p < HEADER_SIZE) {
 294                                 size_t tmp_count;
 295
 296                                 con_buf0[0] = (char)vc->vc_rows;
 297                                 con_buf0[1] = (char)vc->vc_cols;
 298                                 getconsxy(vc, con_buf0 + 2);
 299
 300                                 con_buf_start += p;
 301                                 this_round += p;
 302                                 if (this_round > CON_BUF_SIZE) {
 303                                         this_round = CON_BUF_SIZE;
 304                                         orig_count = this_round - p;
 305                                 }
 306
 307                                 tmp_count = HEADER_SIZE;
 308                                 if (tmp_count > this_round)
 309                                         tmp_count = this_round;
 310
 311                                 /* Advance state pointers and move on. */
 312                                 this_round -= tmp_count;
 313                                 p = HEADER_SIZE;
 314                                 con_buf0 = con_buf + HEADER_SIZE;
 315                                 /* If this_round >= 0, then p is even... */
 316                         } else if (p & 1) {
 317                                 /* Skip first byte for output if start address is odd
 318                                  * Update region sizes up/down depending on free
 319                                  * space in buffer.
 320                                  */
 321                                 con_buf_start++;
 322                                 if (this_round < CON_BUF_SIZE)
 323                                         this_round++;
 324                                 else
 325                                         orig_count--;
 326                         }
 327                         if (this_round > 0) {
 328                                 unsigned short *tmp_buf = (unsigned short *)con_buf0;
 329
 330                                 p -= HEADER_SIZE;
 331                                 p /= 2;
 332                                 col = p % maxcol;
 333
 334                                 org = screen_pos(vc, p, viewed);
 335                                 p += maxcol - col;
 336
 337                                 /* Buffer has even length, so we can always copy
 338                                  * character + attribute. We do not copy last byte
 339                                  * to userspace if this_round is odd.
 340                                  */
 341                                 this_round = (this_round + 1) >> 1;
 342
 343                                 while (this_round) {
 344                                         *tmp_buf++ = vcs_scr_readw(vc, org++);
 345                                         this_round --;
 346                                         if (++col == maxcol) {
 347                                                 org = screen_pos(vc, p, viewed);
 348                                                 col = 0;
 349                                                 p += maxcol;
 350                                         }
 351                                 }
 352                         }
 353                 }
 354
 355                 /* Finally, release the console semaphore while we push
 356                  * all the data to userspace from our temporary buffer.
 357                  *
 358                  * AKPM: Even though it's a semaphore, we should drop it because
 359                  * the pagefault handling code may want to call printk().
 360                  */
 361
 362                 console_unlock();
 363                 ret = copy_to_user(buf, con_buf_start, orig_count);
 364                 console_lock();
 365
 366                 if (ret) {
 367                         read += (orig_count - ret);
 368                         ret = -EFAULT;
 369                         break;
 370                 }
 371                 buf += orig_count;
 372                 pos += orig_count;
 373                 read += orig_count;
 374                 count -= orig_count;
 375         }
 376         *ppos += read;
 377         if (read)
 378                 ret = read;
 379 unlock_out:
 380         console_unlock();
 381         free_page((unsigned long) con_buf);
 382         return ret;
 383 }
 384
 385 static ssize_t
 386 vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 387 {
 388         struct inode *inode = file->f_path.dentry->d_inode;
 389         unsigned int currcons = iminor(inode);
 390         struct vc_data *vc;
 391         long pos;
 392         long attr, size, written;
 393         char *con_buf0;
 394         int col, maxcol, viewed;
 395         u16 *org0 = NULL, *org = NULL;
 396         size_t ret;
 397         char *con_buf;
 398
 399         con_buf = (char *) __get_free_page(GFP_KERNEL);
 400         if (!con_buf)
 401                 return -ENOMEM;
 402
 403         pos = *ppos;
 404
 405         /* Select the proper current console and verify
 406          * sanity of the situation under the console lock.
 407          */
 408         console_lock();
 409
 410         attr = (currcons & 128);
 411         ret = -ENXIO;
 412         vc = vcs_vc(inode, &viewed);
 413         if (!vc)
 414                 goto unlock_out;
 415
 416         size = vcs_size(inode);
 417         ret = -EINVAL;
 418         if (pos < 0 || pos > size)
 419                 goto unlock_out;
 420         if (count > size - pos)
 421                 count = size - pos;
 422         written = 0;
 423         while (count) {
 424                 long this_round = count;
 425                 size_t orig_count;
 426                 long p;
 427
 428                 if (this_round > CON_BUF_SIZE)
 429                         this_round = CON_BUF_SIZE;
 430
 431                 /* Temporarily drop the console lock so that we can read
 432                  * in the write data from userspace safely.
 433                  */
 434                 console_unlock();
 435                 ret = copy_from_user(con_buf, buf, this_round);
 436                 console_lock();
 437
 438                 if (ret) {
 439                         this_round -= ret;
 440                         if (!this_round) {
 441                                 /* Abort loop if no data were copied. Otherwise
 442                                  * fail with -EFAULT.
 443                                  */
 444                                 if (written)
 445                                         break;
 446                                 ret = -EFAULT;
 447                                 goto unlock_out;
 448                         }
 449                 }
 450
 451                 /* The vcs_size might have changed while we slept to grab
 452                  * the user buffer, so recheck.
 453                  * Return data written up to now on failure.
 454                  */
 455                 size = vcs_size(inode);
 456                 if (size < 0) {
 457                         if (written)
 458                                 break;
 459                         ret = size;
 460                         goto unlock_out;
 461                 }
 462                 if (pos >= size)
 463                         break;
 464                 if (this_round > size - pos)
 465                         this_round = size - pos;
 466
 467                 /* OK, now actually push the write to the console
 468                  * under the lock using the local kernel buffer.
 469                  */
 470
 471                 con_buf0 = con_buf;
 472                 orig_count = this_round;
 473                 maxcol = vc->vc_cols;
 474                 p = pos;
 475                 if (!attr) {
 476                         org0 = org = screen_pos(vc, p, viewed);
 477                         col = p % maxcol;
 478                         p += maxcol - col;
 479
 480                         while (this_round > 0) {
 481                                 unsigned char c = *con_buf0++;
 482
 483                                 this_round--;
 484                                 vcs_scr_writew(vc,
 485                                                (vcs_scr_readw(vc, org) & 0xff00) | c, org);
 486                                 org++;
 487                                 if (++col == maxcol) {
 488                                         org = screen_pos(vc, p, viewed);
 489                                         col = 0;
 490                                         p += maxcol;
 491                                 }
 492                         }
 493                 } else {
 494                         if (p < HEADER_SIZE) {
 495                                 char header[HEADER_SIZE];
 496
 497                                 getconsxy(vc, header + 2);
 498                                 while (p < HEADER_SIZE && this_round > 0) {
 499                                         this_round--;
 500                                         header[p++] = *con_buf0++;
 501                                 }
 502                                 if (!viewed)
 503                                         putconsxy(vc, header + 2);
 504                         }
 505                         p -= HEADER_SIZE;
 506                         col = (p/2) % maxcol;
 507                         if (this_round > 0) {
 508                                 org0 = org = screen_pos(vc, p/2, viewed);
 509                                 if ((p & 1) && this_round > 0) {
 510                                         char c;
 511
 512                                         this_round--;
 513                                         c = *con_buf0++;
 514 #ifdef __BIG_ENDIAN
 515                                         vcs_scr_writew(vc, c |
 516                                              (vcs_scr_readw(vc, org) & 0xff00), org);
 517 #else
 518                                         vcs_scr_writew(vc, (c << 8) |
 519                                              (vcs_scr_readw(vc, org) & 0xff), org);
 520 #endif
 521                                         org++;
 522                                         p++;
 523                                         if (++col == maxcol) {
 524                                                 org = screen_pos(vc, p/2, viewed);
 525                                                 col = 0;
 526                                         }
 527                                 }
 528                                 p /= 2;
 529                                 p += maxcol - col;
 530                         }
 531                         while (this_round > 1) {
 532                                 unsigned short w;
 533
 534                                 w = get_unaligned(((unsigned short *)con_buf0));
 535                                 vcs_scr_writew(vc, w, org++);
 536                                 con_buf0 += 2;
 537                                 this_round -= 2;
 538                                 if (++col == maxcol) {
 539                                         org = screen_pos(vc, p, viewed);
 540                                         col = 0;
 541                                         p += maxcol;
 542                                 }
 543                         }
 544                         if (this_round > 0) {
 545                                 unsigned char c;
 546
 547                                 c = *con_buf0++;
 548 #ifdef __BIG_ENDIAN
 549                                 vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff) | (c << 8), org);
 550 #else
 551                                 vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff00) | c, org);
 552 #endif
 553                         }
 554                 }
 555                 count -= orig_count;
 556                 written += orig_count;
 557                 buf += orig_count;
 558                 pos += orig_count;
 559                 if (org0)
 560                         update_region(vc, (unsigned long)(org0), org - org0);
 561         }
 562         *ppos += written;
 563         ret = written;
 564         if (written)
 565                 vcs_scr_updated(vc);
 566
 567 unlock_out:
 568         console_unlock();
 569         free_page((unsigned long) con_buf);
 570         return ret;
 571 }
 572
 573 static unsigned int
 574 vcs_poll(struct file *file, poll_table *wait)
 575 {
 576         struct vcs_poll_data *poll = vcs_poll_data_get(file);
 577         int ret = DEFAULT_POLLMASK|POLLERR|POLLPRI;
 578
 579         if (poll) {
 580                 poll_wait(file, &poll->waitq, wait);
 581                 if (poll->seen_last_update)
 582                         ret = DEFAULT_POLLMASK;
 583         }
 584         return ret;
 585 }
 586
 587 static int
 588 vcs_fasync(int fd, struct file *file, int on)
 589 {
 590         struct vcs_poll_data *poll = file->private_data;
 591
 592         if (!poll) {
 593                 /* don't allocate anything if all we want is disable fasync */
 594                 if (!on)
 595                         return 0;
 596                 poll = vcs_poll_data_get(file);
 597                 if (!poll)
 598                         return -ENOMEM;
 599         }
 600
 601         return fasync_helper(fd, file, on, &poll->fasync);
 602 }
 603
 604 static int
 605 vcs_open(struct inode *inode, struct file *filp)
 606 {
 607         unsigned int currcons = iminor(inode) & 127;
 608         int ret = 0;
 609
 610         tty_lock();
 611         if(currcons && !vc_cons_allocated(currcons-1))
 612                 ret = -ENXIO;
 613         tty_unlock();
 614         return ret;
 615 }
 616
 617 static int vcs_release(struct inode *inode, struct file *file)
 618 {
 619         struct vcs_poll_data *poll = file->private_data;
 620
 621         if (poll)
 622                 vcs_poll_data_free(poll);
 623         return 0;
 624 }
 625
 626 static const struct file_operations vcs_fops = {
 627         .llseek         = vcs_lseek,
 628         .read           = vcs_read,
 629         .write          = vcs_write,
 630         .poll           = vcs_poll,
 631         .fasync         = vcs_fasync,
 632         .open           = vcs_open,
 633         .release        = vcs_release,
 634 };
 635
 636 static struct class *vc_class;
 637
 638 void vcs_make_sysfs(int index)
 639 {
 640         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, index + 1), NULL,
 641                       "vcs%u", index + 1);
 642         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, index + 129), NULL,
 643                       "vcsa%u", index + 1);
 644 }
 645
 646 void vcs_remove_sysfs(int index)
 647 {
 648         device_destroy(vc_class, MKDEV(VCS_MAJOR, index + 1));
 649         device_destroy(vc_class, MKDEV(VCS_MAJOR, index + 129));
 650 }
 651
 652 int __init vcs_init(void)
 653 {
 654         unsigned int i;
 655
 656         if (register_chrdev(VCS_MAJOR, "vcs", &vcs_fops))
 657                 panic("unable to get major %d for vcs device", VCS_MAJOR);
 658         vc_class = class_create(THIS_MODULE, "vc");
 659
 660         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 0), NULL, "vcs");
 661         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 128), NULL, "vcsa");
 662         for (i = 0; i < MIN_NR_CONSOLES; i++)
 663                 vcs_make_sysfs(i);
 664         return 0;
 665 }