drivers/char/vc_screen.c

   1 /*
   2  * linux/drivers/char/vc_screen.c
   3  *
   4  * Provide access to virtual console memory.
   5  * /dev/vcs0: the screen as it is being viewed right now (possibly scrolled)
   6  * /dev/vcsN: the screen of /dev/ttyN (1 <= N <= 63)
   7  *            [minor: N]
   8  *
   9  * /dev/vcsaN: idem, but including attributes, and prefixed with
  10  *      the 4 bytes lines,columns,x,y (as screendump used to give).
  11  *      Attribute/character pair is in native endianity.
  12  *            [minor: N+128]
  13  *
  14  * This replaces screendump and part of selection, so that the system
  15  * administrator can control access using file system permissions.
  16  *
  17  * aeb@cwi.nl - efter Friedas begravelse - 950211
  18  *
  19  * machek@k332.feld.cvut.cz - modified not to send characters to wrong console
  20  *       - fixed some fatal off-by-one bugs (0-- no longer == -1 -> looping and looping and looping...)
  21  *       - making it shorter - scr_readw are macros which expand in PRETTY long code
  22  */
  23
  24 #include <linux/config.h>
  25 #include <linux/kernel.h>
  26 #include <linux/major.h>
  27 #include <linux/errno.h>
  28 #include <linux/tty.h>
  29 #include <linux/devfs_fs_kernel.h>
  30 #include <linux/sched.h>
  31 #include <linux/interrupt.h>
  32 #include <linux/mm.h>
  33 #include <linux/init.h>
  34 #include <linux/vt_kern.h>
  35 #include <linux/console_struct.h>
  36 #include <linux/selection.h>
  37 #include <linux/kbd_kern.h>
  38 #include <linux/console.h>
  39 #include <asm/uaccess.h>
  40 #include <asm/byteorder.h>
  41
  42 #undef attr
  43 #undef org
  44 #undef addr
  45 #define HEADER_SIZE     4
  46
  47 static int
  48 vcs_size(struct inode *inode)
  49 {
  50         int size;
  51         int currcons = MINOR(inode->i_rdev) & 127;
  52         if (currcons == 0)
  53                 currcons = fg_console;
  54         else
  55                 currcons--;
  56         if (!vc_cons_allocated(currcons))
  57                 return -ENXIO;
  58
  59         size = video_num_lines * video_num_columns;
  60
  61         if (MINOR(inode->i_rdev) & 128)
  62                 size = 2*size + HEADER_SIZE;
  63         return size;
  64 }
  65
  66 static loff_t vcs_lseek(struct file *file, loff_t offset, int orig)
  67 {
  68         int size = vcs_size(file->f_dentry->d_inode);
  69
  70         switch (orig) {
  71                 default:
  72                         return -EINVAL;
  73                 case 2:
  74                         offset += size;
  75                         break;
  76                 case 1:
  77                         offset += file->f_pos;
  78                 case 0:
  79                         break;
  80         }
  81         if (offset < 0 || offset > size)
  82                 return -EINVAL;
  83         file->f_pos = offset;
  84         return file->f_pos;
  85 }
  86
  87 /* We share this temporary buffer with the console write code
  88  * so that we can easily avoid touching user space while holding the
  89  * console spinlock.
  90  */
  91 extern char con_buf[PAGE_SIZE];
  92 #define CON_BUF_SIZE    PAGE_SIZE
  93 extern struct semaphore con_buf_sem;
  94
  95 static ssize_t
  96 vcs_read(struct file *file, char *buf, size_t count, loff_t *ppos)
  97 {
  98         struct inode *inode = file->f_dentry->d_inode;
  99         unsigned int currcons = MINOR(inode->i_rdev);
 100         long pos = *ppos;
 101         long viewed, attr, read;
 102         int col, maxcol;
 103         unsigned short *org = NULL;
 104         ssize_t ret;
 105
 106         down(&con_buf_sem);
 107
 108         /* Select the proper current console and verify
 109          * sanity of the situation under the console lock.
 110          */
 111         spin_lock_irq(&console_lock);
 112
 113         attr = (currcons & 128);
 114         currcons = (currcons & 127);
 115         if (currcons == 0) {
 116                 currcons = fg_console;
 117                 viewed = 1;
 118         } else {
 119                 currcons--;
 120                 viewed = 0;
 121         }
 122         ret = -ENXIO;
 123         if (!vc_cons_allocated(currcons))
 124                 goto unlock_out;
 125
 126         ret = -EINVAL;
 127         if (pos < 0)
 128                 goto unlock_out;
 129         read = 0;
 130         ret = 0;
 131         while (count) {
 132                 char *con_buf0, *con_buf_start;
 133                 long this_round, size;
 134                 ssize_t orig_count;
 135                 long p = pos;
 136
 137                 /* Check whether we are above size each round,
 138                  * as copy_to_user at the end of this loop
 139                  * could sleep.
 140                  */
 141                 size = vcs_size(inode);
 142                 if (pos >= size)
 143                         break;
 144                 if (count > size - pos)
 145                         count = size - pos;
 146
 147                 this_round = count;
 148                 if (this_round > CON_BUF_SIZE)
 149                         this_round = CON_BUF_SIZE;
 150
 151                 /* Perform the whole read into the local con_buf.
 152                  * Then we can drop the console spinlock and safely
 153                  * attempt to move it to userspace.
 154                  */
 155
 156                 con_buf_start = con_buf0 = con_buf;
 157                 orig_count = this_round;
 158                 maxcol = video_num_columns;
 159                 if (!attr) {
 160                         org = screen_pos(currcons, p, viewed);
 161                         col = p % maxcol;
 162                         p += maxcol - col;
 163                         while (this_round-- > 0) {
 164                                 *con_buf0++ = (vcs_scr_readw(currcons, org++) & 0xff);
 165                                 if (++col == maxcol) {
 166                                         org = screen_pos(currcons, p, viewed);
 167                                         col = 0;
 168                                         p += maxcol;
 169                                 }
 170                         }
 171                 } else {
 172                         if (p < HEADER_SIZE) {
 173                                 size_t tmp_count;
 174
 175                                 con_buf0[0] = (char) video_num_lines;
 176                                 con_buf0[1] = (char) video_num_columns;
 177                                 getconsxy(currcons, con_buf0 + 2);
 178
 179                                 tmp_count = HEADER_SIZE - p;
 180                                 if (tmp_count > this_round)
 181                                         tmp_count = this_round;
 182
 183                                 /* Advance state pointers and move on. */
 184                                 this_round -= tmp_count;
 185                                 con_buf_start += p;
 186                                 orig_count -= p;
 187                                 p += tmp_count;
 188                                 con_buf0 = con_buf + p;
 189                         }
 190                         p -= HEADER_SIZE;
 191                         col = (p/2) % maxcol;
 192                         if (this_round > 0) {
 193                                 char tmp_byte;
 194
 195                                 org = screen_pos(currcons, p/2, viewed);
 196                                 if ((p & 1) && this_round > 0) {
 197 #ifdef __BIG_ENDIAN
 198                                         tmp_byte = vcs_scr_readw(currcons, org++) & 0xff;
 199 #else
 200                                         tmp_byte = vcs_scr_readw(currcons, org++) >> 8;
 201 #endif
 202
 203                                         *con_buf0++ = tmp_byte;
 204
 205                                         this_round--;
 206                                         p++;
 207                                         if (++col == maxcol) {
 208                                                 org = screen_pos(currcons, p/2, viewed);
 209                                                 col = 0;
 210                                         }
 211                                 }
 212                                 p /= 2;
 213                                 p += maxcol - col;
 214                         }
 215
 216                         if (this_round > 1) {
 217                                 size_t tmp_count = this_round;
 218                                 unsigned short *tmp_buf = (unsigned short *)con_buf0;
 219
 220                                 while (tmp_count > 1) {
 221                                         *tmp_buf++ = vcs_scr_readw(currcons, org++);
 222                                         tmp_count -= 2;
 223                                         if (++col == maxcol) {
 224                                                 org = screen_pos(currcons, p, viewed);
 225                                                 col = 0;
 226                                                 p += maxcol;
 227                                         }
 228                                 }
 229
 230                                 /* Advance pointers, and move on. */
 231                                 this_round = tmp_count;
 232                                 con_buf0 = (char*)tmp_buf;
 233                         }
 234                         if (this_round > 0) {
 235                                 char tmp_byte;
 236
 237 #ifdef __BIG_ENDIAN
 238                                 tmp_byte = vcs_scr_readw(currcons, org) >> 8;
 239 #else
 240                                 tmp_byte = vcs_scr_readw(currcons, org) & 0xff;
 241 #endif
 242
 243                                 *con_buf0++ = tmp_byte;
 244                         }
 245                 }
 246
 247                 /* Finally, temporarily drop the console lock and push
 248                  * all the data to userspace from our temporary buffer.
 249                  */
 250
 251                 spin_unlock_irq(&console_lock);
 252                 ret = copy_to_user(buf, con_buf_start, orig_count);
 253                 spin_lock_irq(&console_lock);
 254
 255                 if (ret) {
 256                         read += (orig_count - ret);
 257                         ret = -EFAULT;
 258                         break;
 259                 }
 260                 buf += orig_count;
 261                 pos += orig_count;
 262                 read += orig_count;
 263                 count -= orig_count;
 264         }
 265         *ppos += read;
 266         if (read)
 267                 ret = read;
 268 unlock_out:
 269         spin_unlock_irq(&console_lock);
 270         up(&con_buf_sem);
 271         return ret;
 272 }
 273
 274 static ssize_t
 275 vcs_write(struct file *file, const char *buf, size_t count, loff_t *ppos)
 276 {
 277         struct inode *inode = file->f_dentry->d_inode;
 278         unsigned int currcons = MINOR(inode->i_rdev);
 279         long pos = *ppos;
 280         long viewed, attr, size, written;
 281         char *con_buf0;
 282         int col, maxcol;
 283         u16 *org0 = NULL, *org = NULL;
 284         size_t ret;
 285
 286         down(&con_buf_sem);
 287
 288         /* Select the proper current console and verify
 289          * sanity of the situation under the console lock.
 290          */
 291         spin_lock_irq(&console_lock);
 292
 293         attr = (currcons & 128);
 294         currcons = (currcons & 127);
 295
 296         if (currcons == 0) {
 297                 currcons = fg_console;
 298                 viewed = 1;
 299         } else {
 300                 currcons--;
 301                 viewed = 0;
 302         }
 303         ret = -ENXIO;
 304         if (!vc_cons_allocated(currcons))
 305                 goto unlock_out;
 306
 307         size = vcs_size(inode);
 308         ret = -EINVAL;
 309         if (pos < 0 || pos > size)
 310                 goto unlock_out;
 311         if (count > size - pos)
 312                 count = size - pos;
 313         written = 0;
 314         while (count) {
 315                 long this_round = count;
 316                 size_t orig_count;
 317                 long p;
 318
 319                 if (this_round > CON_BUF_SIZE)
 320                         this_round = CON_BUF_SIZE;
 321
 322                 /* Temporarily drop the console lock so that we can read
 323                  * in the write data from userspace safely.
 324                  */
 325                 spin_unlock_irq(&console_lock);
 326                 ret = copy_from_user(con_buf, buf, this_round);
 327                 spin_lock_irq(&console_lock);
 328
 329                 if (ret) {
 330                         this_round -= ret;
 331                         if (!this_round) {
 332                                 /* Abort loop if no data were copied. Otherwise
 333                                  * fail with -EFAULT.
 334                                  */
 335                                 if (written)
 336                                         break;
 337                                 ret = -EFAULT;
 338                                 goto unlock_out;
 339                         }
 340                 }
 341
 342                 /* The vcs_size might have changed while we slept to grab
 343                  * the user buffer, so recheck.
 344                  * Return data written up to now on failure.
 345                  */
 346                 size = vcs_size(inode);
 347                 if (pos >= size)
 348                         break;
 349                 if (this_round > size - pos)
 350                         this_round = size - pos;
 351
 352                 /* OK, now actually push the write to the console
 353                  * under the lock using the local kernel buffer.
 354                  */
 355
 356                 con_buf0 = con_buf;
 357                 orig_count = this_round;
 358                 maxcol = video_num_columns;
 359                 p = pos;
 360                 if (!attr) {
 361                         org0 = org = screen_pos(currcons, p, viewed);
 362                         col = p % maxcol;
 363                         p += maxcol - col;
 364
 365                         while (this_round > 0) {
 366                                 unsigned char c = *con_buf0++;
 367
 368                                 this_round--;
 369                                 vcs_scr_writew(currcons,
 370                                                (vcs_scr_readw(currcons, org) & 0xff00) | c, org);
 371                                 org++;
 372                                 if (++col == maxcol) {
 373                                         org = screen_pos(currcons, p, viewed);
 374                                         col = 0;
 375                                         p += maxcol;
 376                                 }
 377                         }
 378                 } else {
 379                         if (p < HEADER_SIZE) {
 380                                 char header[HEADER_SIZE];
 381
 382                                 getconsxy(currcons, header + 2);
 383                                 while (p < HEADER_SIZE && this_round > 0) {
 384                                         this_round--;
 385                                         header[p++] = *con_buf0++;
 386                                 }
 387                                 if (!viewed)
 388                                         putconsxy(currcons, header + 2);
 389                         }
 390                         p -= HEADER_SIZE;
 391                         col = (p/2) % maxcol;
 392                         if (this_round > 0) {
 393                                 org0 = org = screen_pos(currcons, p/2, viewed);
 394                                 if ((p & 1) && this_round > 0) {
 395                                         char c;
 396
 397                                         this_round--;
 398                                         c = *con_buf0++;
 399 #ifdef __BIG_ENDIAN
 400                                         vcs_scr_writew(currcons, c |
 401                                              (vcs_scr_readw(currcons, org) & 0xff00), org);
 402 #else
 403                                         vcs_scr_writew(currcons, (c << 8) |
 404                                              (vcs_scr_readw(currcons, org) & 0xff), org);
 405 #endif
 406                                         org++;
 407                                         p++;
 408                                         if (++col == maxcol) {
 409                                                 org = screen_pos(currcons, p/2, viewed);
 410                                                 col = 0;
 411                                         }
 412                                 }
 413                                 p /= 2;
 414                                 p += maxcol - col;
 415                         }
 416                         while (this_round > 1) {
 417                                 unsigned short w;
 418
 419                                 w = *((const unsigned short *)con_buf0);
 420                                 vcs_scr_writew(currcons, w, org++);
 421                                 con_buf0 += 2;
 422                                 this_round -= 2;
 423                                 if (++col == maxcol) {
 424                                         org = screen_pos(currcons, p, viewed);
 425                                         col = 0;
 426                                         p += maxcol;
 427                                 }
 428                         }
 429                         if (this_round > 0) {
 430                                 unsigned char c;
 431
 432                                 c = *con_buf0++;
 433 #ifdef __BIG_ENDIAN
 434                                 vcs_scr_writew(currcons, (vcs_scr_readw(currcons, org) & 0xff) | (c << 8), org);
 435 #else
 436                                 vcs_scr_writew(currcons, (vcs_scr_readw(currcons, org) & 0xff00) | c, org);
 437 #endif
 438                         }
 439                 }
 440                 count -= orig_count;
 441                 written += orig_count;
 442                 buf += orig_count;
 443                 pos += orig_count;
 444                 if (org0)
 445                         update_region(currcons, (unsigned long)(org0), org-org0);
 446         }
 447         *ppos += written;
 448         ret = written;
 449
 450 unlock_out:
 451         spin_unlock_irq(&console_lock);
 452
 453         up(&con_buf_sem);
 454
 455         return ret;
 456 }
 457
 458 static int
 459 vcs_open(struct inode *inode, struct file *filp)
 460 {
 461         unsigned int currcons = (MINOR(inode->i_rdev) & 127);
 462         if(currcons && !vc_cons_allocated(currcons-1))
 463                 return -ENXIO;
 464         return 0;
 465 }
 466
 467 static struct file_operations vcs_fops = {
 468         llseek:         vcs_lseek,
 469         read:           vcs_read,
 470         write:          vcs_write,
 471         open:           vcs_open,
 472 };
 473
 474 static devfs_handle_t devfs_handle = NULL;
 475
 476 void vcs_make_devfs (unsigned int index, int unregister)
 477 {
 478 #ifdef CONFIG_DEVFS_FS
 479     char name[8];
 480
 481     sprintf (name, "a%u", index + 1);
 482     if (unregister)
 483     {
 484         devfs_unregister ( devfs_find_handle (devfs_handle, name + 1, 0, 0, 0,
 485                                               DEVFS_SPECIAL_CHR, 0) );
 486         devfs_unregister ( devfs_find_handle (devfs_handle, name, 0, 0, 0,
 487                                               DEVFS_SPECIAL_CHR, 0) );
 488     }
 489     else
 490     {
 491         devfs_register (devfs_handle, name + 1, 0, DEVFS_FL_DEFAULT,
 492                         VCS_MAJOR, index + 1,
 493                         S_IFCHR | S_IRUSR | S_IWUSR, 0, 0, &vcs_fops, NULL);
 494         devfs_register (devfs_handle, name, 0, DEVFS_FL_DEFAULT,
 495                         VCS_MAJOR, index + 129,
 496                         S_IFCHR | S_IRUSR | S_IWUSR, 0, 0, &vcs_fops, NULL);
 497     }
 498 #endif /* CONFIG_DEVFS_FS */
 499 }
 500
 501 int __init vcs_init(void)
 502 {
 503         int error;
 504
 505         error = devfs_register_chrdev(VCS_MAJOR, "vcs", &vcs_fops);
 506
 507         if (error)
 508                 printk("unable to get major %d for vcs device", VCS_MAJOR);
 509
 510         devfs_handle = devfs_mk_dir (NULL, "vcc", 3, NULL);
 511         devfs_register (devfs_handle, "0", 1, DEVFS_FL_DEFAULT,
 512                         VCS_MAJOR, 0,
 513                         S_IFCHR | S_IRUSR | S_IWUSR, 0, 0, &vcs_fops, NULL);
 514         devfs_register (devfs_handle, "a", 1, DEVFS_FL_DEFAULT,
 515                         VCS_MAJOR, 128,
 516                         S_IFCHR | S_IRUSR | S_IWUSR, 0, 0, &vcs_fops, NULL);
 517
 518         return error;
 519 }