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/selection.h>
  36 #include <linux/kbd_kern.h>
  37 #include <linux/console.h>
  38 #include <linux/smp_lock.h>
  39 #include <linux/device.h>
  40 #include <asm/uaccess.h>
  41 #include <asm/byteorder.h>
  42 #include <asm/unaligned.h>
  43
  44 #undef attr
  45 #undef org
  46 #undef addr
  47 #define HEADER_SIZE     4
  48
  49 static int
  50 vcs_size(struct inode *inode)
  51 {
  52         int size;
  53         int minor = iminor(inode);
  54         int currcons = minor & 127;
  55         struct vc_data *vc;
  56
  57         if (currcons == 0)
  58                 currcons = fg_console;
  59         else
  60                 currcons--;
  61         if (!vc_cons_allocated(currcons))
  62                 return -ENXIO;
  63         vc = vc_cons[currcons].d;
  64
  65         size = vc->vc_rows * vc->vc_cols;
  66
  67         if (minor & 128)
  68                 size = 2*size + HEADER_SIZE;
  69         return size;
  70 }
  71
  72 static loff_t vcs_lseek(struct file *file, loff_t offset, int orig)
  73 {
  74         int size;
  75
  76         down(&con_buf_sem);
  77         size = vcs_size(file->f_dentry->d_inode);
  78         switch (orig) {
  79                 default:
  80                         up(&con_buf_sem);
  81                         return -EINVAL;
  82                 case 2:
  83                         offset += size;
  84                         break;
  85                 case 1:
  86                         offset += file->f_pos;
  87                 case 0:
  88                         break;
  89         }
  90         if (offset < 0 || offset > size) {
  91                 up(&con_buf_sem);
  92                 return -EINVAL;
  93         }
  94         file->f_pos = offset;
  95         up(&con_buf_sem);
  96         return file->f_pos;
  97 }
  98
  99
 100 static ssize_t
 101 vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 102 {
 103         struct inode *inode = file->f_dentry->d_inode;
 104         unsigned int currcons = iminor(inode);
 105         struct vc_data *vc;
 106         long pos;
 107         long viewed, attr, read;
 108         int col, maxcol;
 109         unsigned short *org = NULL;
 110         ssize_t ret;
 111
 112         down(&con_buf_sem);
 113
 114         pos = *ppos;
 115
 116         /* Select the proper current console and verify
 117          * sanity of the situation under the console lock.
 118          */
 119         acquire_console_sem();
 120
 121         attr = (currcons & 128);
 122         currcons = (currcons & 127);
 123         if (currcons == 0) {
 124                 currcons = fg_console;
 125                 viewed = 1;
 126         } else {
 127                 currcons--;
 128                 viewed = 0;
 129         }
 130         ret = -ENXIO;
 131         if (!vc_cons_allocated(currcons))
 132                 goto unlock_out;
 133         vc = vc_cons[currcons].d;
 134
 135         ret = -EINVAL;
 136         if (pos < 0)
 137                 goto unlock_out;
 138         read = 0;
 139         ret = 0;
 140         while (count) {
 141                 char *con_buf0, *con_buf_start;
 142                 long this_round, size;
 143                 ssize_t orig_count;
 144                 long p = pos;
 145
 146                 /* Check whether we are above size each round,
 147                  * as copy_to_user at the end of this loop
 148                  * could sleep.
 149                  */
 150                 size = vcs_size(inode);
 151                 if (pos >= size)
 152                         break;
 153                 if (count > size - pos)
 154                         count = size - pos;
 155
 156                 this_round = count;
 157                 if (this_round > CON_BUF_SIZE)
 158                         this_round = CON_BUF_SIZE;
 159
 160                 /* Perform the whole read into the local con_buf.
 161                  * Then we can drop the console spinlock and safely
 162                  * attempt to move it to userspace.
 163                  */
 164
 165                 con_buf_start = con_buf0 = con_buf;
 166                 orig_count = this_round;
 167                 maxcol = vc->vc_cols;
 168                 if (!attr) {
 169                         org = screen_pos(vc, p, viewed);
 170                         col = p % maxcol;
 171                         p += maxcol - col;
 172                         while (this_round-- > 0) {
 173                                 *con_buf0++ = (vcs_scr_readw(vc, org++) & 0xff);
 174                                 if (++col == maxcol) {
 175                                         org = screen_pos(vc, p, viewed);
 176                                         col = 0;
 177                                         p += maxcol;
 178                                 }
 179                         }
 180                 } else {
 181                         if (p < HEADER_SIZE) {
 182                                 size_t tmp_count;
 183
 184                                 con_buf0[0] = (char)vc->vc_rows;
 185                                 con_buf0[1] = (char)vc->vc_cols;
 186                                 getconsxy(vc, con_buf0 + 2);
 187
 188                                 con_buf_start += p;
 189                                 this_round += p;
 190                                 if (this_round > CON_BUF_SIZE) {
 191                                         this_round = CON_BUF_SIZE;
 192                                         orig_count = this_round - p;
 193                                 }
 194
 195                                 tmp_count = HEADER_SIZE;
 196                                 if (tmp_count > this_round)
 197                                         tmp_count = this_round;
 198
 199                                 /* Advance state pointers and move on. */
 200                                 this_round -= tmp_count;
 201                                 p = HEADER_SIZE;
 202                                 con_buf0 = con_buf + HEADER_SIZE;
 203                                 /* If this_round >= 0, then p is even... */
 204                         } else if (p & 1) {
 205                                 /* Skip first byte for output if start address is odd
 206                                  * Update region sizes up/down depending on free
 207                                  * space in buffer.
 208                                  */
 209                                 con_buf_start++;
 210                                 if (this_round < CON_BUF_SIZE)
 211                                         this_round++;
 212                                 else
 213                                         orig_count--;
 214                         }
 215                         if (this_round > 0) {
 216                                 unsigned short *tmp_buf = (unsigned short *)con_buf0;
 217
 218                                 p -= HEADER_SIZE;
 219                                 p /= 2;
 220                                 col = p % maxcol;
 221
 222                                 org = screen_pos(vc, p, viewed);
 223                                 p += maxcol - col;
 224
 225                                 /* Buffer has even length, so we can always copy
 226                                  * character + attribute. We do not copy last byte
 227                                  * to userspace if this_round is odd.
 228                                  */
 229                                 this_round = (this_round + 1) >> 1;
 230
 231                                 while (this_round) {
 232                                         *tmp_buf++ = vcs_scr_readw(vc, org++);
 233                                         this_round --;
 234                                         if (++col == maxcol) {
 235                                                 org = screen_pos(vc, p, viewed);
 236                                                 col = 0;
 237                                                 p += maxcol;
 238                                         }
 239                                 }
 240                         }
 241                 }
 242
 243                 /* Finally, release the console semaphore while we push
 244                  * all the data to userspace from our temporary buffer.
 245                  *
 246                  * AKPM: Even though it's a semaphore, we should drop it because
 247                  * the pagefault handling code may want to call printk().
 248                  */
 249
 250                 release_console_sem();
 251                 ret = copy_to_user(buf, con_buf_start, orig_count);
 252                 acquire_console_sem();
 253
 254                 if (ret) {
 255                         read += (orig_count - ret);
 256                         ret = -EFAULT;
 257                         break;
 258                 }
 259                 buf += orig_count;
 260                 pos += orig_count;
 261                 read += orig_count;
 262                 count -= orig_count;
 263         }
 264         *ppos += read;
 265         if (read)
 266                 ret = read;
 267 unlock_out:
 268         release_console_sem();
 269         up(&con_buf_sem);
 270         return ret;
 271 }
 272
 273 static ssize_t
 274 vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 275 {
 276         struct inode *inode = file->f_dentry->d_inode;
 277         unsigned int currcons = iminor(inode);
 278         struct vc_data *vc;
 279         long pos;
 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         pos = *ppos;
 289
 290         /* Select the proper current console and verify
 291          * sanity of the situation under the console lock.
 292          */
 293         acquire_console_sem();
 294
 295         attr = (currcons & 128);
 296         currcons = (currcons & 127);
 297
 298         if (currcons == 0) {
 299                 currcons = fg_console;
 300                 viewed = 1;
 301         } else {
 302                 currcons--;
 303                 viewed = 0;
 304         }
 305         ret = -ENXIO;
 306         if (!vc_cons_allocated(currcons))
 307                 goto unlock_out;
 308         vc = vc_cons[currcons].d;
 309
 310         size = vcs_size(inode);
 311         ret = -EINVAL;
 312         if (pos < 0 || pos > size)
 313                 goto unlock_out;
 314         if (count > size - pos)
 315                 count = size - pos;
 316         written = 0;
 317         while (count) {
 318                 long this_round = count;
 319                 size_t orig_count;
 320                 long p;
 321
 322                 if (this_round > CON_BUF_SIZE)
 323                         this_round = CON_BUF_SIZE;
 324
 325                 /* Temporarily drop the console lock so that we can read
 326                  * in the write data from userspace safely.
 327                  */
 328                 release_console_sem();
 329                 ret = copy_from_user(con_buf, buf, this_round);
 330                 acquire_console_sem();
 331
 332                 if (ret) {
 333                         this_round -= ret;
 334                         if (!this_round) {
 335                                 /* Abort loop if no data were copied. Otherwise
 336                                  * fail with -EFAULT.
 337                                  */
 338                                 if (written)
 339                                         break;
 340                                 ret = -EFAULT;
 341                                 goto unlock_out;
 342                         }
 343                 }
 344
 345                 /* The vcs_size might have changed while we slept to grab
 346                  * the user buffer, so recheck.
 347                  * Return data written up to now on failure.
 348                  */
 349                 size = vcs_size(inode);
 350                 if (pos >= size)
 351                         break;
 352                 if (this_round > size - pos)
 353                         this_round = size - pos;
 354
 355                 /* OK, now actually push the write to the console
 356                  * under the lock using the local kernel buffer.
 357                  */
 358
 359                 con_buf0 = con_buf;
 360                 orig_count = this_round;
 361                 maxcol = vc->vc_cols;
 362                 p = pos;
 363                 if (!attr) {
 364                         org0 = org = screen_pos(vc, p, viewed);
 365                         col = p % maxcol;
 366                         p += maxcol - col;
 367
 368                         while (this_round > 0) {
 369                                 unsigned char c = *con_buf0++;
 370
 371                                 this_round--;
 372                                 vcs_scr_writew(vc,
 373                                                (vcs_scr_readw(vc, org) & 0xff00) | c, org);
 374                                 org++;
 375                                 if (++col == maxcol) {
 376                                         org = screen_pos(vc, p, viewed);
 377                                         col = 0;
 378                                         p += maxcol;
 379                                 }
 380                         }
 381                 } else {
 382                         if (p < HEADER_SIZE) {
 383                                 char header[HEADER_SIZE];
 384
 385                                 getconsxy(vc, header + 2);
 386                                 while (p < HEADER_SIZE && this_round > 0) {
 387                                         this_round--;
 388                                         header[p++] = *con_buf0++;
 389                                 }
 390                                 if (!viewed)
 391                                         putconsxy(vc, header + 2);
 392                         }
 393                         p -= HEADER_SIZE;
 394                         col = (p/2) % maxcol;
 395                         if (this_round > 0) {
 396                                 org0 = org = screen_pos(vc, p/2, viewed);
 397                                 if ((p & 1) && this_round > 0) {
 398                                         char c;
 399
 400                                         this_round--;
 401                                         c = *con_buf0++;
 402 #ifdef __BIG_ENDIAN
 403                                         vcs_scr_writew(vc, c |
 404                                              (vcs_scr_readw(vc, org) & 0xff00), org);
 405 #else
 406                                         vcs_scr_writew(vc, (c << 8) |
 407                                              (vcs_scr_readw(vc, org) & 0xff), org);
 408 #endif
 409                                         org++;
 410                                         p++;
 411                                         if (++col == maxcol) {
 412                                                 org = screen_pos(vc, p/2, viewed);
 413                                                 col = 0;
 414                                         }
 415                                 }
 416                                 p /= 2;
 417                                 p += maxcol - col;
 418                         }
 419                         while (this_round > 1) {
 420                                 unsigned short w;
 421
 422                                 w = get_unaligned(((unsigned short *)con_buf0));
 423                                 vcs_scr_writew(vc, w, org++);
 424                                 con_buf0 += 2;
 425                                 this_round -= 2;
 426                                 if (++col == maxcol) {
 427                                         org = screen_pos(vc, p, viewed);
 428                                         col = 0;
 429                                         p += maxcol;
 430                                 }
 431                         }
 432                         if (this_round > 0) {
 433                                 unsigned char c;
 434
 435                                 c = *con_buf0++;
 436 #ifdef __BIG_ENDIAN
 437                                 vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff) | (c << 8), org);
 438 #else
 439                                 vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff00) | c, org);
 440 #endif
 441                         }
 442                 }
 443                 count -= orig_count;
 444                 written += orig_count;
 445                 buf += orig_count;
 446                 pos += orig_count;
 447                 if (org0)
 448                         update_region(vc, (unsigned long)(org0), org - org0);
 449         }
 450         *ppos += written;
 451         ret = written;
 452
 453 unlock_out:
 454         release_console_sem();
 455
 456         up(&con_buf_sem);
 457
 458         return ret;
 459 }
 460
 461 static int
 462 vcs_open(struct inode *inode, struct file *filp)
 463 {
 464         unsigned int currcons = iminor(inode) & 127;
 465         if(currcons && !vc_cons_allocated(currcons-1))
 466                 return -ENXIO;
 467         return 0;
 468 }
 469
 470 static struct file_operations vcs_fops = {
 471         .llseek         = vcs_lseek,
 472         .read           = vcs_read,
 473         .write          = vcs_write,
 474         .open           = vcs_open,
 475 };
 476
 477 static struct class *vc_class;
 478
 479 void vcs_make_devfs(struct tty_struct *tty)
 480 {
 481         devfs_mk_cdev(MKDEV(VCS_MAJOR, tty->index + 1),
 482                         S_IFCHR|S_IRUSR|S_IWUSR,
 483                         "vcc/%u", tty->index + 1);
 484         devfs_mk_cdev(MKDEV(VCS_MAJOR, tty->index + 129),
 485                         S_IFCHR|S_IRUSR|S_IWUSR,
 486                         "vcc/a%u", tty->index + 1);
 487         class_device_create(vc_class, NULL, MKDEV(VCS_MAJOR, tty->index + 1),
 488                         NULL, "vcs%u", tty->index + 1);
 489         class_device_create(vc_class, NULL, MKDEV(VCS_MAJOR, tty->index + 129),
 490                         NULL, "vcsa%u", tty->index + 1);
 491 }
 492 void vcs_remove_devfs(struct tty_struct *tty)
 493 {
 494         devfs_remove("vcc/%u", tty->index + 1);
 495         devfs_remove("vcc/a%u", tty->index + 1);
 496         class_device_destroy(vc_class, MKDEV(VCS_MAJOR, tty->index + 1));
 497         class_device_destroy(vc_class, MKDEV(VCS_MAJOR, tty->index + 129));
 498 }
 499
 500 int __init vcs_init(void)
 501 {
 502         if (register_chrdev(VCS_MAJOR, "vcs", &vcs_fops))
 503                 panic("unable to get major %d for vcs device", VCS_MAJOR);
 504         vc_class = class_create(THIS_MODULE, "vc");
 505
 506         devfs_mk_cdev(MKDEV(VCS_MAJOR, 0), S_IFCHR|S_IRUSR|S_IWUSR, "vcc/0");
 507         devfs_mk_cdev(MKDEV(VCS_MAJOR, 128), S_IFCHR|S_IRUSR|S_IWUSR, "vcc/a0");
 508         class_device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 0), NULL, "vcs");
 509         class_device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 128), NULL, "vcsa");
 510         return 0;
 511 }