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/kernel.h>
  25 #include <linux/major.h>
  26 #include <linux/errno.h>
  27 #include <linux/tty.h>
  28 #include <linux/interrupt.h>
  29 #include <linux/mm.h>
  30 #include <linux/init.h>
  31 #include <linux/mutex.h>
  32 #include <linux/vt_kern.h>
  33 #include <linux/selection.h>
  34 #include <linux/kbd_kern.h>
  35 #include <linux/console.h>
  36 #include <linux/device.h>
  37 #include <linux/smp_lock.h>
  38
  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 minor = iminor(inode);
  53         int currcons = minor & 127;
  54         struct vc_data *vc;
  55
  56         if (currcons == 0)
  57                 currcons = fg_console;
  58         else
  59                 currcons--;
  60         if (!vc_cons_allocated(currcons))
  61                 return -ENXIO;
  62         vc = vc_cons[currcons].d;
  63
  64         size = vc->vc_rows * vc->vc_cols;
  65
  66         if (minor & 128)
  67                 size = 2*size + HEADER_SIZE;
  68         return size;
  69 }
  70
  71 static loff_t vcs_lseek(struct file *file, loff_t offset, int orig)
  72 {
  73         int size;
  74
  75         mutex_lock(&con_buf_mtx);
  76         size = vcs_size(file->f_path.dentry->d_inode);
  77         switch (orig) {
  78                 default:
  79                         mutex_unlock(&con_buf_mtx);
  80                         return -EINVAL;
  81                 case 2:
  82                         offset += size;
  83                         break;
  84                 case 1:
  85                         offset += file->f_pos;
  86                 case 0:
  87                         break;
  88         }
  89         if (offset < 0 || offset > size) {
  90                 mutex_unlock(&con_buf_mtx);
  91                 return -EINVAL;
  92         }
  93         file->f_pos = offset;
  94         mutex_unlock(&con_buf_mtx);
  95         return file->f_pos;
  96 }
  97
  98
  99 static ssize_t
 100 vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 101 {
 102         struct inode *inode = file->f_path.dentry->d_inode;
 103         unsigned int currcons = iminor(inode);
 104         struct vc_data *vc;
 105         long pos;
 106         long viewed, attr, read;
 107         int col, maxcol;
 108         unsigned short *org = NULL;
 109         ssize_t ret;
 110
 111         mutex_lock(&con_buf_mtx);
 112
 113         pos = *ppos;
 114
 115         /* Select the proper current console and verify
 116          * sanity of the situation under the console lock.
 117          */
 118         acquire_console_sem();
 119
 120         attr = (currcons & 128);
 121         currcons = (currcons & 127);
 122         if (currcons == 0) {
 123                 currcons = fg_console;
 124                 viewed = 1;
 125         } else {
 126                 currcons--;
 127                 viewed = 0;
 128         }
 129         ret = -ENXIO;
 130         if (!vc_cons_allocated(currcons))
 131                 goto unlock_out;
 132         vc = vc_cons[currcons].d;
 133
 134         ret = -EINVAL;
 135         if (pos < 0)
 136                 goto unlock_out;
 137         read = 0;
 138         ret = 0;
 139         while (count) {
 140                 char *con_buf0, *con_buf_start;
 141                 long this_round, size;
 142                 ssize_t orig_count;
 143                 long p = pos;
 144
 145                 /* Check whether we are above size each round,
 146                  * as copy_to_user at the end of this loop
 147                  * could sleep.
 148                  */
 149                 size = vcs_size(inode);
 150                 if (pos >= size)
 151                         break;
 152                 if (count > size - pos)
 153                         count = size - pos;
 154
 155                 this_round = count;
 156                 if (this_round > CON_BUF_SIZE)
 157                         this_round = CON_BUF_SIZE;
 158
 159                 /* Perform the whole read into the local con_buf.
 160                  * Then we can drop the console spinlock and safely
 161                  * attempt to move it to userspace.
 162                  */
 163
 164                 con_buf_start = con_buf0 = con_buf;
 165                 orig_count = this_round;
 166                 maxcol = vc->vc_cols;
 167                 if (!attr) {
 168                         org = screen_pos(vc, p, viewed);
 169                         col = p % maxcol;
 170                         p += maxcol - col;
 171                         while (this_round-- > 0) {
 172                                 *con_buf0++ = (vcs_scr_readw(vc, org++) & 0xff);
 173                                 if (++col == maxcol) {
 174                                         org = screen_pos(vc, p, viewed);
 175                                         col = 0;
 176                                         p += maxcol;
 177                                 }
 178                         }
 179                 } else {
 180                         if (p < HEADER_SIZE) {
 181                                 size_t tmp_count;
 182
 183                                 con_buf0[0] = (char)vc->vc_rows;
 184                                 con_buf0[1] = (char)vc->vc_cols;
 185                                 getconsxy(vc, con_buf0 + 2);
 186
 187                                 con_buf_start += p;
 188                                 this_round += p;
 189                                 if (this_round > CON_BUF_SIZE) {
 190                                         this_round = CON_BUF_SIZE;
 191                                         orig_count = this_round - p;
 192                                 }
 193
 194                                 tmp_count = HEADER_SIZE;
 195                                 if (tmp_count > this_round)
 196                                         tmp_count = this_round;
 197
 198                                 /* Advance state pointers and move on. */
 199                                 this_round -= tmp_count;
 200                                 p = HEADER_SIZE;
 201                                 con_buf0 = con_buf + HEADER_SIZE;
 202                                 /* If this_round >= 0, then p is even... */
 203                         } else if (p & 1) {
 204                                 /* Skip first byte for output if start address is odd
 205                                  * Update region sizes up/down depending on free
 206                                  * space in buffer.
 207                                  */
 208                                 con_buf_start++;
 209                                 if (this_round < CON_BUF_SIZE)
 210                                         this_round++;
 211                                 else
 212                                         orig_count--;
 213                         }
 214                         if (this_round > 0) {
 215                                 unsigned short *tmp_buf = (unsigned short *)con_buf0;
 216
 217                                 p -= HEADER_SIZE;
 218                                 p /= 2;
 219                                 col = p % maxcol;
 220
 221                                 org = screen_pos(vc, p, viewed);
 222                                 p += maxcol - col;
 223
 224                                 /* Buffer has even length, so we can always copy
 225                                  * character + attribute. We do not copy last byte
 226                                  * to userspace if this_round is odd.
 227                                  */
 228                                 this_round = (this_round + 1) >> 1;
 229
 230                                 while (this_round) {
 231                                         *tmp_buf++ = vcs_scr_readw(vc, org++);
 232                                         this_round --;
 233                                         if (++col == maxcol) {
 234                                                 org = screen_pos(vc, p, viewed);
 235                                                 col = 0;
 236                                                 p += maxcol;
 237                                         }
 238                                 }
 239                         }
 240                 }
 241
 242                 /* Finally, release the console semaphore while we push
 243                  * all the data to userspace from our temporary buffer.
 244                  *
 245                  * AKPM: Even though it's a semaphore, we should drop it because
 246                  * the pagefault handling code may want to call printk().
 247                  */
 248
 249                 release_console_sem();
 250                 ret = copy_to_user(buf, con_buf_start, orig_count);
 251                 acquire_console_sem();
 252
 253                 if (ret) {
 254                         read += (orig_count - ret);
 255                         ret = -EFAULT;
 256                         break;
 257                 }
 258                 buf += orig_count;
 259                 pos += orig_count;
 260                 read += orig_count;
 261                 count -= orig_count;
 262         }
 263         *ppos += read;
 264         if (read)
 265                 ret = read;
 266 unlock_out:
 267         release_console_sem();
 268         mutex_unlock(&con_buf_mtx);
 269         return ret;
 270 }
 271
 272 static ssize_t
 273 vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 274 {
 275         struct inode *inode = file->f_path.dentry->d_inode;
 276         unsigned int currcons = iminor(inode);
 277         struct vc_data *vc;
 278         long pos;
 279         long viewed, attr, size, written;
 280         char *con_buf0;
 281         int col, maxcol;
 282         u16 *org0 = NULL, *org = NULL;
 283         size_t ret;
 284
 285         mutex_lock(&con_buf_mtx);
 286
 287         pos = *ppos;
 288
 289         /* Select the proper current console and verify
 290          * sanity of the situation under the console lock.
 291          */
 292         acquire_console_sem();
 293
 294         attr = (currcons & 128);
 295         currcons = (currcons & 127);
 296
 297         if (currcons == 0) {
 298                 currcons = fg_console;
 299                 viewed = 1;
 300         } else {
 301                 currcons--;
 302                 viewed = 0;
 303         }
 304         ret = -ENXIO;
 305         if (!vc_cons_allocated(currcons))
 306                 goto unlock_out;
 307         vc = vc_cons[currcons].d;
 308
 309         size = vcs_size(inode);
 310         ret = -EINVAL;
 311         if (pos < 0 || pos > size)
 312                 goto unlock_out;
 313         if (count > size - pos)
 314                 count = size - pos;
 315         written = 0;
 316         while (count) {
 317                 long this_round = count;
 318                 size_t orig_count;
 319                 long p;
 320
 321                 if (this_round > CON_BUF_SIZE)
 322                         this_round = CON_BUF_SIZE;
 323
 324                 /* Temporarily drop the console lock so that we can read
 325                  * in the write data from userspace safely.
 326                  */
 327                 release_console_sem();
 328                 ret = copy_from_user(con_buf, buf, this_round);
 329                 acquire_console_sem();
 330
 331                 if (ret) {
 332                         this_round -= ret;
 333                         if (!this_round) {
 334                                 /* Abort loop if no data were copied. Otherwise
 335                                  * fail with -EFAULT.
 336                                  */
 337                                 if (written)
 338                                         break;
 339                                 ret = -EFAULT;
 340                                 goto unlock_out;
 341                         }
 342                 }
 343
 344                 /* The vcs_size might have changed while we slept to grab
 345                  * the user buffer, so recheck.
 346                  * Return data written up to now on failure.
 347                  */
 348                 size = vcs_size(inode);
 349                 if (pos >= size)
 350                         break;
 351                 if (this_round > size - pos)
 352                         this_round = size - pos;
 353
 354                 /* OK, now actually push the write to the console
 355                  * under the lock using the local kernel buffer.
 356                  */
 357
 358                 con_buf0 = con_buf;
 359                 orig_count = this_round;
 360                 maxcol = vc->vc_cols;
 361                 p = pos;
 362                 if (!attr) {
 363                         org0 = org = screen_pos(vc, p, viewed);
 364                         col = p % maxcol;
 365                         p += maxcol - col;
 366
 367                         while (this_round > 0) {
 368                                 unsigned char c = *con_buf0++;
 369
 370                                 this_round--;
 371                                 vcs_scr_writew(vc,
 372                                                (vcs_scr_readw(vc, org) & 0xff00) | c, org);
 373                                 org++;
 374                                 if (++col == maxcol) {
 375                                         org = screen_pos(vc, p, viewed);
 376                                         col = 0;
 377                                         p += maxcol;
 378                                 }
 379                         }
 380                 } else {
 381                         if (p < HEADER_SIZE) {
 382                                 char header[HEADER_SIZE];
 383
 384                                 getconsxy(vc, header + 2);
 385                                 while (p < HEADER_SIZE && this_round > 0) {
 386                                         this_round--;
 387                                         header[p++] = *con_buf0++;
 388                                 }
 389                                 if (!viewed)
 390                                         putconsxy(vc, header + 2);
 391                         }
 392                         p -= HEADER_SIZE;
 393                         col = (p/2) % maxcol;
 394                         if (this_round > 0) {
 395                                 org0 = org = screen_pos(vc, p/2, viewed);
 396                                 if ((p & 1) && this_round > 0) {
 397                                         char c;
 398
 399                                         this_round--;
 400                                         c = *con_buf0++;
 401 #ifdef __BIG_ENDIAN
 402                                         vcs_scr_writew(vc, c |
 403                                              (vcs_scr_readw(vc, org) & 0xff00), org);
 404 #else
 405                                         vcs_scr_writew(vc, (c << 8) |
 406                                              (vcs_scr_readw(vc, org) & 0xff), org);
 407 #endif
 408                                         org++;
 409                                         p++;
 410                                         if (++col == maxcol) {
 411                                                 org = screen_pos(vc, p/2, viewed);
 412                                                 col = 0;
 413                                         }
 414                                 }
 415                                 p /= 2;
 416                                 p += maxcol - col;
 417                         }
 418                         while (this_round > 1) {
 419                                 unsigned short w;
 420
 421                                 w = get_unaligned(((unsigned short *)con_buf0));
 422                                 vcs_scr_writew(vc, w, org++);
 423                                 con_buf0 += 2;
 424                                 this_round -= 2;
 425                                 if (++col == maxcol) {
 426                                         org = screen_pos(vc, p, viewed);
 427                                         col = 0;
 428                                         p += maxcol;
 429                                 }
 430                         }
 431                         if (this_round > 0) {
 432                                 unsigned char c;
 433
 434                                 c = *con_buf0++;
 435 #ifdef __BIG_ENDIAN
 436                                 vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff) | (c << 8), org);
 437 #else
 438                                 vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff00) | c, org);
 439 #endif
 440                         }
 441                 }
 442                 count -= orig_count;
 443                 written += orig_count;
 444                 buf += orig_count;
 445                 pos += orig_count;
 446                 if (org0)
 447                         update_region(vc, (unsigned long)(org0), org - org0);
 448         }
 449         *ppos += written;
 450         ret = written;
 451
 452 unlock_out:
 453         release_console_sem();
 454
 455         mutex_unlock(&con_buf_mtx);
 456
 457         return ret;
 458 }
 459
 460 static int
 461 vcs_open(struct inode *inode, struct file *filp)
 462 {
 463         unsigned int currcons = iminor(inode) & 127;
 464         int ret = 0;
 465
 466         lock_kernel();
 467         if(currcons && !vc_cons_allocated(currcons-1))
 468                 ret = -ENXIO;
 469         unlock_kernel();
 470         return ret;
 471 }
 472
 473 static const struct file_operations vcs_fops = {
 474         .llseek         = vcs_lseek,
 475         .read           = vcs_read,
 476         .write          = vcs_write,
 477         .open           = vcs_open,
 478 };
 479
 480 static struct class *vc_class;
 481
 482 void vcs_make_sysfs(struct tty_struct *tty)
 483 {
 484         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, tty->index + 1), NULL,
 485                       "vcs%u", tty->index + 1);
 486         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, tty->index + 129), NULL,
 487                       "vcsa%u", tty->index + 1);
 488 }
 489
 490 void vcs_remove_sysfs(struct tty_struct *tty)
 491 {
 492         device_destroy(vc_class, MKDEV(VCS_MAJOR, tty->index + 1));
 493         device_destroy(vc_class, MKDEV(VCS_MAJOR, tty->index + 129));
 494 }
 495
 496 int __init vcs_init(void)
 497 {
 498         if (register_chrdev(VCS_MAJOR, "vcs", &vcs_fops))
 499                 panic("unable to get major %d for vcs device", VCS_MAJOR);
 500         vc_class = class_create(THIS_MODULE, "vc");
 501
 502         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 0), NULL, "vcs");
 503         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 128), NULL, "vcsa");
 504         return 0;
 505 }