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