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         lock_kernel();
  74         size = vcs_size(file->f_dentry->d_inode);
  75         switch (orig) {
  76                 default:
  77                         unlock_kernel();
  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                 unlock_kernel();
  89                 return -EINVAL;
  90         }
  91         file->f_pos = offset;
  92         unlock_kernel();
  93         return file->f_pos;
  94 }
  95
  96 /* We share this temporary buffer with the console write code
  97  * so that we can easily avoid touching user space while holding the
  98  * console spinlock.
  99  */
 100 extern char con_buf[PAGE_SIZE];
 101 #define CON_BUF_SIZE    PAGE_SIZE
 102 extern struct semaphore con_buf_sem;
 103
 104 static ssize_t
 105 vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 106 {
 107         struct inode *inode = file->f_dentry->d_inode;
 108         unsigned int currcons = iminor(inode);
 109         long pos = *ppos;
 110         long viewed, attr, read;
 111         int col, maxcol;
 112         unsigned short *org = NULL;
 113         ssize_t ret;
 114
 115         down(&con_buf_sem);
 116
 117         /* Select the proper current console and verify
 118          * sanity of the situation under the console lock.
 119          */
 120         acquire_console_sem();
 121
 122         attr = (currcons & 128);
 123         currcons = (currcons & 127);
 124         if (currcons == 0) {
 125                 currcons = fg_console;
 126                 viewed = 1;
 127         } else {
 128                 currcons--;
 129                 viewed = 0;
 130         }
 131         ret = -ENXIO;
 132         if (!vc_cons_allocated(currcons))
 133                 goto unlock_out;
 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 = video_num_columns;
 168                 if (!attr) {
 169                         org = screen_pos(currcons, p, viewed);
 170                         col = p % maxcol;
 171                         p += maxcol - col;
 172                         while (this_round-- > 0) {
 173                                 *con_buf0++ = (vcs_scr_readw(currcons, org++) & 0xff);
 174                                 if (++col == maxcol) {
 175                                         org = screen_pos(currcons, 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) video_num_lines;
 185                                 con_buf0[1] = (char) video_num_columns;
 186                                 getconsxy(currcons, 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(currcons, 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(currcons, org++);
 233                                         this_round --;
 234                                         if (++col == maxcol) {
 235                                                 org = screen_pos(currcons, 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         long pos = *ppos;
 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         down(&con_buf_sem);
 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
 306         size = vcs_size(inode);
 307         ret = -EINVAL;
 308         if (pos < 0 || pos > size)
 309                 goto unlock_out;
 310         if (count > size - pos)
 311                 count = size - pos;
 312         written = 0;
 313         while (count) {
 314                 long this_round = count;
 315                 size_t orig_count;
 316                 long p;
 317
 318                 if (this_round > CON_BUF_SIZE)
 319                         this_round = CON_BUF_SIZE;
 320
 321                 /* Temporarily drop the console lock so that we can read
 322                  * in the write data from userspace safely.
 323                  */
 324                 release_console_sem();
 325                 ret = copy_from_user(con_buf, buf, this_round);
 326                 acquire_console_sem();
 327
 328                 if (ret) {
 329                         this_round -= ret;
 330                         if (!this_round) {
 331                                 /* Abort loop if no data were copied. Otherwise
 332                                  * fail with -EFAULT.
 333                                  */
 334                                 if (written)
 335                                         break;
 336                                 ret = -EFAULT;
 337                                 goto unlock_out;
 338                         }
 339                 }
 340
 341                 /* The vcs_size might have changed while we slept to grab
 342                  * the user buffer, so recheck.
 343                  * Return data written up to now on failure.
 344                  */
 345                 size = vcs_size(inode);
 346                 if (pos >= size)
 347                         break;
 348                 if (this_round > size - pos)
 349                         this_round = size - pos;
 350
 351                 /* OK, now actually push the write to the console
 352                  * under the lock using the local kernel buffer.
 353                  */
 354
 355                 con_buf0 = con_buf;
 356                 orig_count = this_round;
 357                 maxcol = video_num_columns;
 358                 p = pos;
 359                 if (!attr) {
 360                         org0 = org = screen_pos(currcons, p, viewed);
 361                         col = p % maxcol;
 362                         p += maxcol - col;
 363
 364                         while (this_round > 0) {
 365                                 unsigned char c = *con_buf0++;
 366
 367                                 this_round--;
 368                                 vcs_scr_writew(currcons,
 369                                                (vcs_scr_readw(currcons, org) & 0xff00) | c, org);
 370                                 org++;
 371                                 if (++col == maxcol) {
 372                                         org = screen_pos(currcons, p, viewed);
 373                                         col = 0;
 374                                         p += maxcol;
 375                                 }
 376                         }
 377                 } else {
 378                         if (p < HEADER_SIZE) {
 379                                 char header[HEADER_SIZE];
 380
 381                                 getconsxy(currcons, header + 2);
 382                                 while (p < HEADER_SIZE && this_round > 0) {
 383                                         this_round--;
 384                                         header[p++] = *con_buf0++;
 385                                 }
 386                                 if (!viewed)
 387                                         putconsxy(currcons, header + 2);
 388                         }
 389                         p -= HEADER_SIZE;
 390                         col = (p/2) % maxcol;
 391                         if (this_round > 0) {
 392                                 org0 = org = screen_pos(currcons, p/2, viewed);
 393                                 if ((p & 1) && this_round > 0) {
 394                                         char c;
 395
 396                                         this_round--;
 397                                         c = *con_buf0++;
 398 #ifdef __BIG_ENDIAN
 399                                         vcs_scr_writew(currcons, c |
 400                                              (vcs_scr_readw(currcons, org) & 0xff00), org);
 401 #else
 402                                         vcs_scr_writew(currcons, (c << 8) |
 403                                              (vcs_scr_readw(currcons, org) & 0xff), org);
 404 #endif
 405                                         org++;
 406                                         p++;
 407                                         if (++col == maxcol) {
 408                                                 org = screen_pos(currcons, p/2, viewed);
 409                                                 col = 0;
 410                                         }
 411                                 }
 412                                 p /= 2;
 413                                 p += maxcol - col;
 414                         }
 415                         while (this_round > 1) {
 416                                 unsigned short w;
 417
 418                                 w = get_unaligned(((const unsigned short *)con_buf0));
 419                                 vcs_scr_writew(currcons, w, org++);
 420                                 con_buf0 += 2;
 421                                 this_round -= 2;
 422                                 if (++col == maxcol) {
 423                                         org = screen_pos(currcons, p, viewed);
 424                                         col = 0;
 425                                         p += maxcol;
 426                                 }
 427                         }
 428                         if (this_round > 0) {
 429                                 unsigned char c;
 430
 431                                 c = *con_buf0++;
 432 #ifdef __BIG_ENDIAN
 433                                 vcs_scr_writew(currcons, (vcs_scr_readw(currcons, org) & 0xff) | (c << 8), org);
 434 #else
 435                                 vcs_scr_writew(currcons, (vcs_scr_readw(currcons, org) & 0xff00) | c, org);
 436 #endif
 437                         }
 438                 }
 439                 count -= orig_count;
 440                 written += orig_count;
 441                 buf += orig_count;
 442                 pos += orig_count;
 443                 if (org0)
 444                         update_region(currcons, (unsigned long)(org0), org-org0);
 445         }
 446         *ppos += written;
 447         ret = written;
 448
 449 unlock_out:
 450         release_console_sem();
 451
 452         up(&con_buf_sem);
 453
 454         return ret;
 455 }
 456
 457 static int
 458 vcs_open(struct inode *inode, struct file *filp)
 459 {
 460         unsigned int currcons = iminor(inode) & 127;
 461         if(currcons && !vc_cons_allocated(currcons-1))
 462                 return -ENXIO;
 463         return 0;
 464 }
 465
 466 static struct file_operations vcs_fops = {
 467         .llseek         = vcs_lseek,
 468         .read           = vcs_read,
 469         .write          = vcs_write,
 470         .open           = vcs_open,
 471 };
 472
 473 static struct class_simple *vc_class;
 474
 475 void vcs_make_devfs(struct tty_struct *tty)
 476 {
 477         devfs_mk_cdev(MKDEV(VCS_MAJOR, tty->index + 1),
 478                         S_IFCHR|S_IRUSR|S_IWUSR,
 479                         "vcc/%u", tty->index + 1);
 480         devfs_mk_cdev(MKDEV(VCS_MAJOR, tty->index + 129),
 481                         S_IFCHR|S_IRUSR|S_IWUSR,
 482                         "vcc/a%u", tty->index + 1);
 483         class_simple_device_add(vc_class, MKDEV(VCS_MAJOR, tty->index + 1), NULL, "vcs%u", tty->index + 1);
 484         class_simple_device_add(vc_class, MKDEV(VCS_MAJOR, tty->index + 129), NULL, "vcsa%u", tty->index + 1);
 485 }
 486 void vcs_remove_devfs(struct tty_struct *tty)
 487 {
 488         devfs_remove("vcc/%u", tty->index + 1);
 489         devfs_remove("vcc/a%u", tty->index + 1);
 490         class_simple_device_remove(MKDEV(VCS_MAJOR, tty->index + 1));
 491         class_simple_device_remove(MKDEV(VCS_MAJOR, tty->index + 129));
 492 }
 493
 494 int __init vcs_init(void)
 495 {
 496         if (register_chrdev(VCS_MAJOR, "vcs", &vcs_fops))
 497                 panic("unable to get major %d for vcs device", VCS_MAJOR);
 498         vc_class = class_simple_create(THIS_MODULE, "vc");
 499
 500         devfs_mk_cdev(MKDEV(VCS_MAJOR, 0), S_IFCHR|S_IRUSR|S_IWUSR, "vcc/0");
 501         devfs_mk_cdev(MKDEV(VCS_MAJOR, 128), S_IFCHR|S_IRUSR|S_IWUSR, "vcc/a0");
 502         class_simple_device_add(vc_class, MKDEV(VCS_MAJOR, 0), NULL, "vcs");
 503         class_simple_device_add(vc_class, MKDEV(VCS_MAJOR, 128), NULL, "vcsa");
 504         return 0;
 505 }