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