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         if (currcons == 0)
  56                 currcons = fg_console;
  57         else
  58                 currcons--;
  59         if (!vc_cons_allocated(currcons))
  60                 return -ENXIO;
  61
  62         size = video_num_lines * video_num_columns;
  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_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_dentry->d_inode;
 101         unsigned int currcons = iminor(inode);
 102         long pos;
 103         long viewed, attr, read;
 104         int col, maxcol;
 105         unsigned short *org = NULL;
 106         ssize_t ret;
 107
 108         down(&con_buf_sem);
 109
 110         pos = *ppos;
 111
 112         /* Select the proper current console and verify
 113          * sanity of the situation under the console lock.
 114          */
 115         acquire_console_sem();
 116
 117         attr = (currcons & 128);
 118         currcons = (currcons & 127);
 119         if (currcons == 0) {
 120                 currcons = fg_console;
 121                 viewed = 1;
 122         } else {
 123                 currcons--;
 124                 viewed = 0;
 125         }
 126         ret = -ENXIO;
 127         if (!vc_cons_allocated(currcons))
 128                 goto unlock_out;
 129
 130         ret = -EINVAL;
 131         if (pos < 0)
 132                 goto unlock_out;
 133         read = 0;
 134         ret = 0;
 135         while (count) {
 136                 char *con_buf0, *con_buf_start;
 137                 long this_round, size;
 138                 ssize_t orig_count;
 139                 long p = pos;
 140
 141                 /* Check whether we are above size each round,
 142                  * as copy_to_user at the end of this loop
 143                  * could sleep.
 144                  */
 145                 size = vcs_size(inode);
 146                 if (pos >= size)
 147                         break;
 148                 if (count > size - pos)
 149                         count = size - pos;
 150
 151                 this_round = count;
 152                 if (this_round > CON_BUF_SIZE)
 153                         this_round = CON_BUF_SIZE;
 154
 155                 /* Perform the whole read into the local con_buf.
 156                  * Then we can drop the console spinlock and safely
 157                  * attempt to move it to userspace.
 158                  */
 159
 160                 con_buf_start = con_buf0 = con_buf;
 161                 orig_count = this_round;
 162                 maxcol = video_num_columns;
 163                 if (!attr) {
 164                         org = screen_pos(currcons, p, viewed);
 165                         col = p % maxcol;
 166                         p += maxcol - col;
 167                         while (this_round-- > 0) {
 168                                 *con_buf0++ = (vcs_scr_readw(currcons, org++) & 0xff);
 169                                 if (++col == maxcol) {
 170                                         org = screen_pos(currcons, p, viewed);
 171                                         col = 0;
 172                                         p += maxcol;
 173                                 }
 174                         }
 175                 } else {
 176                         if (p < HEADER_SIZE) {
 177                                 size_t tmp_count;
 178
 179                                 con_buf0[0] = (char) video_num_lines;
 180                                 con_buf0[1] = (char) video_num_columns;
 181                                 getconsxy(currcons, con_buf0 + 2);
 182
 183                                 con_buf_start += p;
 184                                 this_round += p;
 185                                 if (this_round > CON_BUF_SIZE) {
 186                                         this_round = CON_BUF_SIZE;
 187                                         orig_count = this_round - p;
 188                                 }
 189
 190                                 tmp_count = HEADER_SIZE;
 191                                 if (tmp_count > this_round)
 192                                         tmp_count = this_round;
 193
 194                                 /* Advance state pointers and move on. */
 195                                 this_round -= tmp_count;
 196                                 p = HEADER_SIZE;
 197                                 con_buf0 = con_buf + HEADER_SIZE;
 198                                 /* If this_round >= 0, then p is even... */
 199                         } else if (p & 1) {
 200                                 /* Skip first byte for output if start address is odd
 201                                  * Update region sizes up/down depending on free
 202                                  * space in buffer.
 203                                  */
 204                                 con_buf_start++;
 205                                 if (this_round < CON_BUF_SIZE)
 206                                         this_round++;
 207                                 else
 208                                         orig_count--;
 209                         }
 210                         if (this_round > 0) {
 211                                 unsigned short *tmp_buf = (unsigned short *)con_buf0;
 212
 213                                 p -= HEADER_SIZE;
 214                                 p /= 2;
 215                                 col = p % maxcol;
 216
 217                                 org = screen_pos(currcons, p, viewed);
 218                                 p += maxcol - col;
 219
 220                                 /* Buffer has even length, so we can always copy
 221                                  * character + attribute. We do not copy last byte
 222                                  * to userspace if this_round is odd.
 223                                  */
 224                                 this_round = (this_round + 1) >> 1;
 225
 226                                 while (this_round) {
 227                                         *tmp_buf++ = vcs_scr_readw(currcons, org++);
 228                                         this_round --;
 229                                         if (++col == maxcol) {
 230                                                 org = screen_pos(currcons, p, viewed);
 231                                                 col = 0;
 232                                                 p += maxcol;
 233                                         }
 234                                 }
 235                         }
 236                 }
 237
 238                 /* Finally, release the console semaphore while we push
 239                  * all the data to userspace from our temporary buffer.
 240                  *
 241                  * AKPM: Even though it's a semaphore, we should drop it because
 242                  * the pagefault handling code may want to call printk().
 243                  */
 244
 245                 release_console_sem();
 246                 ret = copy_to_user(buf, con_buf_start, orig_count);
 247                 acquire_console_sem();
 248
 249                 if (ret) {
 250                         read += (orig_count - ret);
 251                         ret = -EFAULT;
 252                         break;
 253                 }
 254                 buf += orig_count;
 255                 pos += orig_count;
 256                 read += orig_count;
 257                 count -= orig_count;
 258         }
 259         *ppos += read;
 260         if (read)
 261                 ret = read;
 262 unlock_out:
 263         release_console_sem();
 264         up(&con_buf_sem);
 265         return ret;
 266 }
 267
 268 static ssize_t
 269 vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 270 {
 271         struct inode *inode = file->f_dentry->d_inode;
 272         unsigned int currcons = iminor(inode);
 273         long pos;
 274         long viewed, attr, size, written;
 275         char *con_buf0;
 276         int col, maxcol;
 277         u16 *org0 = NULL, *org = NULL;
 278         size_t ret;
 279
 280         down(&con_buf_sem);
 281
 282         pos = *ppos;
 283
 284         /* Select the proper current console and verify
 285          * sanity of the situation under the console lock.
 286          */
 287         acquire_console_sem();
 288
 289         attr = (currcons & 128);
 290         currcons = (currcons & 127);
 291
 292         if (currcons == 0) {
 293                 currcons = fg_console;
 294                 viewed = 1;
 295         } else {
 296                 currcons--;
 297                 viewed = 0;
 298         }
 299         ret = -ENXIO;
 300         if (!vc_cons_allocated(currcons))
 301                 goto unlock_out;
 302
 303         size = vcs_size(inode);
 304         ret = -EINVAL;
 305         if (pos < 0 || pos > size)
 306                 goto unlock_out;
 307         if (count > size - pos)
 308                 count = size - pos;
 309         written = 0;
 310         while (count) {
 311                 long this_round = count;
 312                 size_t orig_count;
 313                 long p;
 314
 315                 if (this_round > CON_BUF_SIZE)
 316                         this_round = CON_BUF_SIZE;
 317
 318                 /* Temporarily drop the console lock so that we can read
 319                  * in the write data from userspace safely.
 320                  */
 321                 release_console_sem();
 322                 ret = copy_from_user(con_buf, buf, this_round);
 323                 acquire_console_sem();
 324
 325                 if (ret) {
 326                         this_round -= ret;
 327                         if (!this_round) {
 328                                 /* Abort loop if no data were copied. Otherwise
 329                                  * fail with -EFAULT.
 330                                  */
 331                                 if (written)
 332                                         break;
 333                                 ret = -EFAULT;
 334                                 goto unlock_out;
 335                         }
 336                 }
 337
 338                 /* The vcs_size might have changed while we slept to grab
 339                  * the user buffer, so recheck.
 340                  * Return data written up to now on failure.
 341                  */
 342                 size = vcs_size(inode);
 343                 if (pos >= size)
 344                         break;
 345                 if (this_round > size - pos)
 346                         this_round = size - pos;
 347
 348                 /* OK, now actually push the write to the console
 349                  * under the lock using the local kernel buffer.
 350                  */
 351
 352                 con_buf0 = con_buf;
 353                 orig_count = this_round;
 354                 maxcol = video_num_columns;
 355                 p = pos;
 356                 if (!attr) {
 357                         org0 = org = screen_pos(currcons, p, viewed);
 358                         col = p % maxcol;
 359                         p += maxcol - col;
 360
 361                         while (this_round > 0) {
 362                                 unsigned char c = *con_buf0++;
 363
 364                                 this_round--;
 365                                 vcs_scr_writew(currcons,
 366                                                (vcs_scr_readw(currcons, org) & 0xff00) | c, org);
 367                                 org++;
 368                                 if (++col == maxcol) {
 369                                         org = screen_pos(currcons, p, viewed);
 370                                         col = 0;
 371                                         p += maxcol;
 372                                 }
 373                         }
 374                 } else {
 375                         if (p < HEADER_SIZE) {
 376                                 char header[HEADER_SIZE];
 377
 378                                 getconsxy(currcons, header + 2);
 379                                 while (p < HEADER_SIZE && this_round > 0) {
 380                                         this_round--;
 381                                         header[p++] = *con_buf0++;
 382                                 }
 383                                 if (!viewed)
 384                                         putconsxy(currcons, header + 2);
 385                         }
 386                         p -= HEADER_SIZE;
 387                         col = (p/2) % maxcol;
 388                         if (this_round > 0) {
 389                                 org0 = org = screen_pos(currcons, p/2, viewed);
 390                                 if ((p & 1) && this_round > 0) {
 391                                         char c;
 392
 393                                         this_round--;
 394                                         c = *con_buf0++;
 395 #ifdef __BIG_ENDIAN
 396                                         vcs_scr_writew(currcons, c |
 397                                              (vcs_scr_readw(currcons, org) & 0xff00), org);
 398 #else
 399                                         vcs_scr_writew(currcons, (c << 8) |
 400                                              (vcs_scr_readw(currcons, org) & 0xff), org);
 401 #endif
 402                                         org++;
 403                                         p++;
 404                                         if (++col == maxcol) {
 405                                                 org = screen_pos(currcons, p/2, viewed);
 406                                                 col = 0;
 407                                         }
 408                                 }
 409                                 p /= 2;
 410                                 p += maxcol - col;
 411                         }
 412                         while (this_round > 1) {
 413                                 unsigned short w;
 414
 415                                 w = get_unaligned(((const unsigned short *)con_buf0));
 416                                 vcs_scr_writew(currcons, w, org++);
 417                                 con_buf0 += 2;
 418                                 this_round -= 2;
 419                                 if (++col == maxcol) {
 420                                         org = screen_pos(currcons, p, viewed);
 421                                         col = 0;
 422                                         p += maxcol;
 423                                 }
 424                         }
 425                         if (this_round > 0) {
 426                                 unsigned char c;
 427
 428                                 c = *con_buf0++;
 429 #ifdef __BIG_ENDIAN
 430                                 vcs_scr_writew(currcons, (vcs_scr_readw(currcons, org) & 0xff) | (c << 8), org);
 431 #else
 432                                 vcs_scr_writew(currcons, (vcs_scr_readw(currcons, org) & 0xff00) | c, org);
 433 #endif
 434                         }
 435                 }
 436                 count -= orig_count;
 437                 written += orig_count;
 438                 buf += orig_count;
 439                 pos += orig_count;
 440                 if (org0)
 441                         update_region(currcons, (unsigned long)(org0), org-org0);
 442         }
 443         *ppos += written;
 444         ret = written;
 445
 446 unlock_out:
 447         release_console_sem();
 448
 449         up(&con_buf_sem);
 450
 451         return ret;
 452 }
 453
 454 static int
 455 vcs_open(struct inode *inode, struct file *filp)
 456 {
 457         unsigned int currcons = iminor(inode) & 127;
 458         if(currcons && !vc_cons_allocated(currcons-1))
 459                 return -ENXIO;
 460         return 0;
 461 }
 462
 463 static struct file_operations vcs_fops = {
 464         .llseek         = vcs_lseek,
 465         .read           = vcs_read,
 466         .write          = vcs_write,
 467         .open           = vcs_open,
 468 };
 469
 470 static struct class_simple *vc_class;
 471
 472 void vcs_make_devfs(struct tty_struct *tty)
 473 {
 474         devfs_mk_cdev(MKDEV(VCS_MAJOR, tty->index + 1),
 475                         S_IFCHR|S_IRUSR|S_IWUSR,
 476                         "vcc/%u", tty->index + 1);
 477         devfs_mk_cdev(MKDEV(VCS_MAJOR, tty->index + 129),
 478                         S_IFCHR|S_IRUSR|S_IWUSR,
 479                         "vcc/a%u", tty->index + 1);
 480         class_simple_device_add(vc_class, MKDEV(VCS_MAJOR, tty->index + 1), NULL, "vcs%u", tty->index + 1);
 481         class_simple_device_add(vc_class, MKDEV(VCS_MAJOR, tty->index + 129), NULL, "vcsa%u", tty->index + 1);
 482 }
 483 void vcs_remove_devfs(struct tty_struct *tty)
 484 {
 485         devfs_remove("vcc/%u", tty->index + 1);
 486         devfs_remove("vcc/a%u", tty->index + 1);
 487         class_simple_device_remove(MKDEV(VCS_MAJOR, tty->index + 1));
 488         class_simple_device_remove(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_simple_create(THIS_MODULE, "vc");
 496
 497         devfs_mk_cdev(MKDEV(VCS_MAJOR, 0), S_IFCHR|S_IRUSR|S_IWUSR, "vcc/0");
 498         devfs_mk_cdev(MKDEV(VCS_MAJOR, 128), S_IFCHR|S_IRUSR|S_IWUSR, "vcc/a0");
 499         class_simple_device_add(vc_class, MKDEV(VCS_MAJOR, 0), NULL, "vcs");
 500         class_simple_device_add(vc_class, MKDEV(VCS_MAJOR, 128), NULL, "vcsa");
 501         return 0;
 502 }