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/vt_kern.h>
  32 #include <linux/selection.h>
  33 #include <linux/kbd_kern.h>
  34 #include <linux/console.h>
  35 #include <linux/smp_lock.h>
  36 #include <linux/device.h>
  37 #include <asm/uaccess.h>
  38 #include <asm/byteorder.h>
  39 #include <asm/unaligned.h>
  40
  41 #undef attr
  42 #undef org
  43 #undef addr
  44 #define HEADER_SIZE     4
  45
  46 static int
  47 vcs_size(struct inode *inode)
  48 {
  49         int size;
  50         int minor = iminor(inode);
  51         int currcons = minor & 127;
  52         struct vc_data *vc;
  53
  54         if (currcons == 0)
  55                 currcons = fg_console;
  56         else
  57                 currcons--;
  58         if (!vc_cons_allocated(currcons))
  59                 return -ENXIO;
  60         vc = vc_cons[currcons].d;
  61
  62         size = vc->vc_rows * vc->vc_cols;
  63
  64         if (minor & 128)
  65                 size = 2*size + HEADER_SIZE;
  66         return size;
  67 }
  68
  69 static loff_t vcs_lseek(struct file *file, loff_t offset, int orig)
  70 {
  71         int size;
  72
  73         down(&con_buf_sem);
  74         size = vcs_size(file->f_path.dentry->d_inode);
  75         switch (orig) {
  76                 default:
  77                         up(&con_buf_sem);
  78                         return -EINVAL;
  79                 case 2:
  80                         offset += size;
  81                         break;
  82                 case 1:
  83                         offset += file->f_pos;
  84                 case 0:
  85                         break;
  86         }
  87         if (offset < 0 || offset > size) {
  88                 up(&con_buf_sem);
  89                 return -EINVAL;
  90         }
  91         file->f_pos = offset;
  92         up(&con_buf_sem);
  93         return file->f_pos;
  94 }
  95
  96
  97 static ssize_t
  98 vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
  99 {
 100         struct inode *inode = file->f_path.dentry->d_inode;
 101         unsigned int currcons = iminor(inode);
 102         struct vc_data *vc;
 103         long pos;
 104         long viewed, attr, read;
 105         int col, maxcol;
 106         unsigned short *org = NULL;
 107         ssize_t ret;
 108
 109         down(&con_buf_sem);
 110
 111         pos = *ppos;
 112
 113         /* Select the proper current console and verify
 114          * sanity of the situation under the console lock.
 115          */
 116         acquire_console_sem();
 117
 118         attr = (currcons & 128);
 119         currcons = (currcons & 127);
 120         if (currcons == 0) {
 121                 currcons = fg_console;
 122                 viewed = 1;
 123         } else {
 124                 currcons--;
 125                 viewed = 0;
 126         }
 127         ret = -ENXIO;
 128         if (!vc_cons_allocated(currcons))
 129                 goto unlock_out;
 130         vc = vc_cons[currcons].d;
 131
 132         ret = -EINVAL;
 133         if (pos < 0)
 134                 goto unlock_out;
 135         read = 0;
 136         ret = 0;
 137         while (count) {
 138                 char *con_buf0, *con_buf_start;
 139                 long this_round, size;
 140                 ssize_t orig_count;
 141                 long p = pos;
 142
 143                 /* Check whether we are above size each round,
 144                  * as copy_to_user at the end of this loop
 145                  * could sleep.
 146                  */
 147                 size = vcs_size(inode);
 148                 if (pos >= size)
 149                         break;
 150                 if (count > size - pos)
 151                         count = size - pos;
 152
 153                 this_round = count;
 154                 if (this_round > CON_BUF_SIZE)
 155                         this_round = CON_BUF_SIZE;
 156
 157                 /* Perform the whole read into the local con_buf.
 158                  * Then we can drop the console spinlock and safely
 159                  * attempt to move it to userspace.
 160                  */
 161
 162                 con_buf_start = con_buf0 = con_buf;
 163                 orig_count = this_round;
 164                 maxcol = vc->vc_cols;
 165                 if (!attr) {
 166                         org = screen_pos(vc, p, viewed);
 167                         col = p % maxcol;
 168                         p += maxcol - col;
 169                         while (this_round-- > 0) {
 170                                 *con_buf0++ = (vcs_scr_readw(vc, org++) & 0xff);
 171                                 if (++col == maxcol) {
 172                                         org = screen_pos(vc, p, viewed);
 173                                         col = 0;
 174                                         p += maxcol;
 175                                 }
 176                         }
 177                 } else {
 178                         if (p < HEADER_SIZE) {
 179                                 size_t tmp_count;
 180
 181                                 con_buf0[0] = (char)vc->vc_rows;
 182                                 con_buf0[1] = (char)vc->vc_cols;
 183                                 getconsxy(vc, con_buf0 + 2);
 184
 185                                 con_buf_start += p;
 186                                 this_round += p;
 187                                 if (this_round > CON_BUF_SIZE) {
 188                                         this_round = CON_BUF_SIZE;
 189                                         orig_count = this_round - p;
 190                                 }
 191
 192                                 tmp_count = HEADER_SIZE;
 193                                 if (tmp_count > this_round)
 194                                         tmp_count = this_round;
 195
 196                                 /* Advance state pointers and move on. */
 197                                 this_round -= tmp_count;
 198                                 p = HEADER_SIZE;
 199                                 con_buf0 = con_buf + HEADER_SIZE;
 200                                 /* If this_round >= 0, then p is even... */
 201                         } else if (p & 1) {
 202                                 /* Skip first byte for output if start address is odd
 203                                  * Update region sizes up/down depending on free
 204                                  * space in buffer.
 205                                  */
 206                                 con_buf_start++;
 207                                 if (this_round < CON_BUF_SIZE)
 208                                         this_round++;
 209                                 else
 210                                         orig_count--;
 211                         }
 212                         if (this_round > 0) {
 213                                 unsigned short *tmp_buf = (unsigned short *)con_buf0;
 214
 215                                 p -= HEADER_SIZE;
 216                                 p /= 2;
 217                                 col = p % maxcol;
 218
 219                                 org = screen_pos(vc, p, viewed);
 220                                 p += maxcol - col;
 221
 222                                 /* Buffer has even length, so we can always copy
 223                                  * character + attribute. We do not copy last byte
 224                                  * to userspace if this_round is odd.
 225                                  */
 226                                 this_round = (this_round + 1) >> 1;
 227
 228                                 while (this_round) {
 229                                         *tmp_buf++ = vcs_scr_readw(vc, org++);
 230                                         this_round --;
 231                                         if (++col == maxcol) {
 232                                                 org = screen_pos(vc, p, viewed);
 233                                                 col = 0;
 234                                                 p += maxcol;
 235                                         }
 236                                 }
 237                         }
 238                 }
 239
 240                 /* Finally, release the console semaphore while we push
 241                  * all the data to userspace from our temporary buffer.
 242                  *
 243                  * AKPM: Even though it's a semaphore, we should drop it because
 244                  * the pagefault handling code may want to call printk().
 245                  */
 246
 247                 release_console_sem();
 248                 ret = copy_to_user(buf, con_buf_start, orig_count);
 249                 acquire_console_sem();
 250
 251                 if (ret) {
 252                         read += (orig_count - ret);
 253                         ret = -EFAULT;
 254                         break;
 255                 }
 256                 buf += orig_count;
 257                 pos += orig_count;
 258                 read += orig_count;
 259                 count -= orig_count;
 260         }
 261         *ppos += read;
 262         if (read)
 263                 ret = read;
 264 unlock_out:
 265         release_console_sem();
 266         up(&con_buf_sem);
 267         return ret;
 268 }
 269
 270 static ssize_t
 271 vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 272 {
 273         struct inode *inode = file->f_path.dentry->d_inode;
 274         unsigned int currcons = iminor(inode);
 275         struct vc_data *vc;
 276         long pos;
 277         long viewed, attr, size, written;
 278         char *con_buf0;
 279         int col, maxcol;
 280         u16 *org0 = NULL, *org = NULL;
 281         size_t ret;
 282
 283         down(&con_buf_sem);
 284
 285         pos = *ppos;
 286
 287         /* Select the proper current console and verify
 288          * sanity of the situation under the console lock.
 289          */
 290         acquire_console_sem();
 291
 292         attr = (currcons & 128);
 293         currcons = (currcons & 127);
 294
 295         if (currcons == 0) {
 296                 currcons = fg_console;
 297                 viewed = 1;
 298         } else {
 299                 currcons--;
 300                 viewed = 0;
 301         }
 302         ret = -ENXIO;
 303         if (!vc_cons_allocated(currcons))
 304                 goto unlock_out;
 305         vc = vc_cons[currcons].d;
 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                 release_console_sem();
 326                 ret = copy_from_user(con_buf, buf, this_round);
 327                 acquire_console_sem();
 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 = vc->vc_cols;
 359                 p = pos;
 360                 if (!attr) {
 361                         org0 = org = screen_pos(vc, 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(vc,
 370                                                (vcs_scr_readw(vc, org) & 0xff00) | c, org);
 371                                 org++;
 372                                 if (++col == maxcol) {
 373                                         org = screen_pos(vc, 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(vc, header + 2);
 383                                 while (p < HEADER_SIZE && this_round > 0) {
 384                                         this_round--;
 385                                         header[p++] = *con_buf0++;
 386                                 }
 387                                 if (!viewed)
 388                                         putconsxy(vc, header + 2);
 389                         }
 390                         p -= HEADER_SIZE;
 391                         col = (p/2) % maxcol;
 392                         if (this_round > 0) {
 393                                 org0 = org = screen_pos(vc, 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(vc, c |
 401                                              (vcs_scr_readw(vc, org) & 0xff00), org);
 402 #else
 403                                         vcs_scr_writew(vc, (c << 8) |
 404                                              (vcs_scr_readw(vc, org) & 0xff), org);
 405 #endif
 406                                         org++;
 407                                         p++;
 408                                         if (++col == maxcol) {
 409                                                 org = screen_pos(vc, 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 = get_unaligned(((unsigned short *)con_buf0));
 420                                 vcs_scr_writew(vc, w, org++);
 421                                 con_buf0 += 2;
 422                                 this_round -= 2;
 423                                 if (++col == maxcol) {
 424                                         org = screen_pos(vc, 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(vc, (vcs_scr_readw(vc, org) & 0xff) | (c << 8), org);
 435 #else
 436                                 vcs_scr_writew(vc, (vcs_scr_readw(vc, 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(vc, (unsigned long)(org0), org - org0);
 446         }
 447         *ppos += written;
 448         ret = written;
 449
 450 unlock_out:
 451         release_console_sem();
 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 = iminor(inode) & 127;
 462         if(currcons && !vc_cons_allocated(currcons-1))
 463                 return -ENXIO;
 464         return 0;
 465 }
 466
 467 static const 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 struct class *vc_class;
 475
 476 void vcs_make_sysfs(struct tty_struct *tty)
 477 {
 478         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, tty->index + 1),
 479                         "vcs%u", tty->index + 1);
 480         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, tty->index + 129),
 481                         "vcsa%u", tty->index + 1);
 482 }
 483
 484 void vcs_remove_sysfs(struct tty_struct *tty)
 485 {
 486         device_destroy(vc_class, MKDEV(VCS_MAJOR, tty->index + 1));
 487         device_destroy(vc_class, MKDEV(VCS_MAJOR, tty->index + 129));
 488 }
 489
 490 int __init vcs_init(void)
 491 {
 492         if (register_chrdev(VCS_MAJOR, "vcs", &vcs_fops))
 493                 panic("unable to get major %d for vcs device", VCS_MAJOR);
 494         vc_class = class_create(THIS_MODULE, "vc");
 495
 496         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 0), "vcs");
 497         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 128), "vcsa");
 498         return 0;
 499 }