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/device.h>
  36 #include <asm/uaccess.h>
  37 #include <asm/byteorder.h>
  38 #include <asm/unaligned.h>
  39
  40 #undef attr
  41 #undef org
  42 #undef addr
  43 #define HEADER_SIZE     4
  44
  45 static int
  46 vcs_size(struct inode *inode)
  47 {
  48         int size;
  49         int minor = iminor(inode);
  50         int currcons = minor & 127;
  51         struct vc_data *vc;
  52
  53         if (currcons == 0)
  54                 currcons = fg_console;
  55         else
  56                 currcons--;
  57         if (!vc_cons_allocated(currcons))
  58                 return -ENXIO;
  59         vc = vc_cons[currcons].d;
  60
  61         size = vc->vc_rows * vc->vc_cols;
  62
  63         if (minor & 128)
  64                 size = 2*size + HEADER_SIZE;
  65         return size;
  66 }
  67
  68 static loff_t vcs_lseek(struct file *file, loff_t offset, int orig)
  69 {
  70         int size;
  71
  72         down(&con_buf_sem);
  73         size = vcs_size(file->f_path.dentry->d_inode);
  74         switch (orig) {
  75                 default:
  76                         up(&con_buf_sem);
  77                         return -EINVAL;
  78                 case 2:
  79                         offset += size;
  80                         break;
  81                 case 1:
  82                         offset += file->f_pos;
  83                 case 0:
  84                         break;
  85         }
  86         if (offset < 0 || offset > size) {
  87                 up(&con_buf_sem);
  88                 return -EINVAL;
  89         }
  90         file->f_pos = offset;
  91         up(&con_buf_sem);
  92         return file->f_pos;
  93 }
  94
  95
  96 static ssize_t
  97 vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
  98 {
  99         struct inode *inode = file->f_path.dentry->d_inode;
 100         unsigned int currcons = iminor(inode);
 101         struct vc_data *vc;
 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         vc = vc_cons[currcons].d;
 130
 131         ret = -EINVAL;
 132         if (pos < 0)
 133                 goto unlock_out;
 134         read = 0;
 135         ret = 0;
 136         while (count) {
 137                 char *con_buf0, *con_buf_start;
 138                 long this_round, size;
 139                 ssize_t orig_count;
 140                 long p = pos;
 141
 142                 /* Check whether we are above size each round,
 143                  * as copy_to_user at the end of this loop
 144                  * could sleep.
 145                  */
 146                 size = vcs_size(inode);
 147                 if (pos >= size)
 148                         break;
 149                 if (count > size - pos)
 150                         count = size - pos;
 151
 152                 this_round = count;
 153                 if (this_round > CON_BUF_SIZE)
 154                         this_round = CON_BUF_SIZE;
 155
 156                 /* Perform the whole read into the local con_buf.
 157                  * Then we can drop the console spinlock and safely
 158                  * attempt to move it to userspace.
 159                  */
 160
 161                 con_buf_start = con_buf0 = con_buf;
 162                 orig_count = this_round;
 163                 maxcol = vc->vc_cols;
 164                 if (!attr) {
 165                         org = screen_pos(vc, p, viewed);
 166                         col = p % maxcol;
 167                         p += maxcol - col;
 168                         while (this_round-- > 0) {
 169                                 *con_buf0++ = (vcs_scr_readw(vc, org++) & 0xff);
 170                                 if (++col == maxcol) {
 171                                         org = screen_pos(vc, p, viewed);
 172                                         col = 0;
 173                                         p += maxcol;
 174                                 }
 175                         }
 176                 } else {
 177                         if (p < HEADER_SIZE) {
 178                                 size_t tmp_count;
 179
 180                                 con_buf0[0] = (char)vc->vc_rows;
 181                                 con_buf0[1] = (char)vc->vc_cols;
 182                                 getconsxy(vc, con_buf0 + 2);
 183
 184                                 con_buf_start += p;
 185                                 this_round += p;
 186                                 if (this_round > CON_BUF_SIZE) {
 187                                         this_round = CON_BUF_SIZE;
 188                                         orig_count = this_round - p;
 189                                 }
 190
 191                                 tmp_count = HEADER_SIZE;
 192                                 if (tmp_count > this_round)
 193                                         tmp_count = this_round;
 194
 195                                 /* Advance state pointers and move on. */
 196                                 this_round -= tmp_count;
 197                                 p = HEADER_SIZE;
 198                                 con_buf0 = con_buf + HEADER_SIZE;
 199                                 /* If this_round >= 0, then p is even... */
 200                         } else if (p & 1) {
 201                                 /* Skip first byte for output if start address is odd
 202                                  * Update region sizes up/down depending on free
 203                                  * space in buffer.
 204                                  */
 205                                 con_buf_start++;
 206                                 if (this_round < CON_BUF_SIZE)
 207                                         this_round++;
 208                                 else
 209                                         orig_count--;
 210                         }
 211                         if (this_round > 0) {
 212                                 unsigned short *tmp_buf = (unsigned short *)con_buf0;
 213
 214                                 p -= HEADER_SIZE;
 215                                 p /= 2;
 216                                 col = p % maxcol;
 217
 218                                 org = screen_pos(vc, p, viewed);
 219                                 p += maxcol - col;
 220
 221                                 /* Buffer has even length, so we can always copy
 222                                  * character + attribute. We do not copy last byte
 223                                  * to userspace if this_round is odd.
 224                                  */
 225                                 this_round = (this_round + 1) >> 1;
 226
 227                                 while (this_round) {
 228                                         *tmp_buf++ = vcs_scr_readw(vc, org++);
 229                                         this_round --;
 230                                         if (++col == maxcol) {
 231                                                 org = screen_pos(vc, p, viewed);
 232                                                 col = 0;
 233                                                 p += maxcol;
 234                                         }
 235                                 }
 236                         }
 237                 }
 238
 239                 /* Finally, release the console semaphore while we push
 240                  * all the data to userspace from our temporary buffer.
 241                  *
 242                  * AKPM: Even though it's a semaphore, we should drop it because
 243                  * the pagefault handling code may want to call printk().
 244                  */
 245
 246                 release_console_sem();
 247                 ret = copy_to_user(buf, con_buf_start, orig_count);
 248                 acquire_console_sem();
 249
 250                 if (ret) {
 251                         read += (orig_count - ret);
 252                         ret = -EFAULT;
 253                         break;
 254                 }
 255                 buf += orig_count;
 256                 pos += orig_count;
 257                 read += orig_count;
 258                 count -= orig_count;
 259         }
 260         *ppos += read;
 261         if (read)
 262                 ret = read;
 263 unlock_out:
 264         release_console_sem();
 265         up(&con_buf_sem);
 266         return ret;
 267 }
 268
 269 static ssize_t
 270 vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 271 {
 272         struct inode *inode = file->f_path.dentry->d_inode;
 273         unsigned int currcons = iminor(inode);
 274         struct vc_data *vc;
 275         long pos;
 276         long viewed, attr, size, written;
 277         char *con_buf0;
 278         int col, maxcol;
 279         u16 *org0 = NULL, *org = NULL;
 280         size_t ret;
 281
 282         down(&con_buf_sem);
 283
 284         pos = *ppos;
 285
 286         /* Select the proper current console and verify
 287          * sanity of the situation under the console lock.
 288          */
 289         acquire_console_sem();
 290
 291         attr = (currcons & 128);
 292         currcons = (currcons & 127);
 293
 294         if (currcons == 0) {
 295                 currcons = fg_console;
 296                 viewed = 1;
 297         } else {
 298                 currcons--;
 299                 viewed = 0;
 300         }
 301         ret = -ENXIO;
 302         if (!vc_cons_allocated(currcons))
 303                 goto unlock_out;
 304         vc = vc_cons[currcons].d;
 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 = vc->vc_cols;
 358                 p = pos;
 359                 if (!attr) {
 360                         org0 = org = screen_pos(vc, 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(vc,
 369                                                (vcs_scr_readw(vc, org) & 0xff00) | c, org);
 370                                 org++;
 371                                 if (++col == maxcol) {
 372                                         org = screen_pos(vc, 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(vc, header + 2);
 382                                 while (p < HEADER_SIZE && this_round > 0) {
 383                                         this_round--;
 384                                         header[p++] = *con_buf0++;
 385                                 }
 386                                 if (!viewed)
 387                                         putconsxy(vc, header + 2);
 388                         }
 389                         p -= HEADER_SIZE;
 390                         col = (p/2) % maxcol;
 391                         if (this_round > 0) {
 392                                 org0 = org = screen_pos(vc, 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(vc, c |
 400                                              (vcs_scr_readw(vc, org) & 0xff00), org);
 401 #else
 402                                         vcs_scr_writew(vc, (c << 8) |
 403                                              (vcs_scr_readw(vc, org) & 0xff), org);
 404 #endif
 405                                         org++;
 406                                         p++;
 407                                         if (++col == maxcol) {
 408                                                 org = screen_pos(vc, 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(((unsigned short *)con_buf0));
 419                                 vcs_scr_writew(vc, w, org++);
 420                                 con_buf0 += 2;
 421                                 this_round -= 2;
 422                                 if (++col == maxcol) {
 423                                         org = screen_pos(vc, 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(vc, (vcs_scr_readw(vc, org) & 0xff) | (c << 8), org);
 434 #else
 435                                 vcs_scr_writew(vc, (vcs_scr_readw(vc, 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(vc, (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 const 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 *vc_class;
 474
 475 void vcs_make_sysfs(struct tty_struct *tty)
 476 {
 477         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, tty->index + 1),
 478                         "vcs%u", tty->index + 1);
 479         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, tty->index + 129),
 480                         "vcsa%u", tty->index + 1);
 481 }
 482
 483 void vcs_remove_sysfs(struct tty_struct *tty)
 484 {
 485         device_destroy(vc_class, MKDEV(VCS_MAJOR, tty->index + 1));
 486         device_destroy(vc_class, MKDEV(VCS_MAJOR, tty->index + 129));
 487 }
 488
 489 int __init vcs_init(void)
 490 {
 491         if (register_chrdev(VCS_MAJOR, "vcs", &vcs_fops))
 492                 panic("unable to get major %d for vcs device", VCS_MAJOR);
 493         vc_class = class_create(THIS_MODULE, "vc");
 494
 495         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 0), "vcs");
 496         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 128), "vcsa");
 497         return 0;
 498 }