fs/seq_file.c

   1 /*
   2  * linux/fs/seq_file.c
   3  *
   4  * helper functions for making synthetic files from sequences of records.
   5  * initial implementation -- AV, Oct 2001.
   6  */
   7
   8 #include <linux/fs.h>
   9 #include <linux/module.h>
  10 #include <linux/seq_file.h>
  11 #include <linux/slab.h>
  12
  13 #include <asm/uaccess.h>
  14 #include <asm/page.h>
  15
  16 /**
  17  *      seq_open -      initialize sequential file
  18  *      @file: file we initialize
  19  *      @op: method table describing the sequence
  20  *
  21  *      seq_open() sets @file, associating it with a sequence described
  22  *      by @op.  @op->start() sets the iterator up and returns the first
  23  *      element of sequence. @op->stop() shuts it down.  @op->next()
  24  *      returns the next element of sequence.  @op->show() prints element
  25  *      into the buffer.  In case of error ->start() and ->next() return
  26  *      ERR_PTR(error).  In the end of sequence they return %NULL. ->show()
  27  *      returns 0 in case of success and negative number in case of error.
  28  *      Returning SEQ_SKIP means "discard this element and move on".
  29  */
  30 int seq_open(struct file *file, const struct seq_operations *op)
  31 {
  32         struct seq_file *p = file->private_data;
  33
  34         if (!p) {
  35                 p = kmalloc(sizeof(*p), GFP_KERNEL);
  36                 if (!p)
  37                         return -ENOMEM;
  38                 file->private_data = p;
  39         }
  40         memset(p, 0, sizeof(*p));
  41         mutex_init(&p->lock);
  42         p->op = op;
  43
  44         /*
  45          * Wrappers around seq_open(e.g. swaps_open) need to be
  46          * aware of this. If they set f_version themselves, they
  47          * should call seq_open first and then set f_version.
  48          */
  49         file->f_version = 0;
  50
  51         /* SEQ files support lseek, but not pread/pwrite */
  52         file->f_mode &= ~(FMODE_PREAD | FMODE_PWRITE);
  53         return 0;
  54 }
  55 EXPORT_SYMBOL(seq_open);
  56
  57 /**
  58  *      seq_read -      ->read() method for sequential files.
  59  *      @file: the file to read from
  60  *      @buf: the buffer to read to
  61  *      @size: the maximum number of bytes to read
  62  *      @ppos: the current position in the file
  63  *
  64  *      Ready-made ->f_op->read()
  65  */
  66 ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
  67 {
  68         struct seq_file *m = (struct seq_file *)file->private_data;
  69         size_t copied = 0;
  70         loff_t pos;
  71         size_t n;
  72         void *p;
  73         int err = 0;
  74
  75         mutex_lock(&m->lock);
  76         /*
  77          * seq_file->op->..m_start/m_stop/m_next may do special actions
  78          * or optimisations based on the file->f_version, so we want to
  79          * pass the file->f_version to those methods.
  80          *
  81          * seq_file->version is just copy of f_version, and seq_file
  82          * methods can treat it simply as file version.
  83          * It is copied in first and copied out after all operations.
  84          * It is convenient to have it as  part of structure to avoid the
  85          * need of passing another argument to all the seq_file methods.
  86          */
  87         m->version = file->f_version;
  88         /* grab buffer if we didn't have one */
  89         if (!m->buf) {
  90                 m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
  91                 if (!m->buf)
  92                         goto Enomem;
  93         }
  94         /* if not empty - flush it first */
  95         if (m->count) {
  96                 n = min(m->count, size);
  97                 err = copy_to_user(buf, m->buf + m->from, n);
  98                 if (err)
  99                         goto Efault;
 100                 m->count -= n;
 101                 m->from += n;
 102                 size -= n;
 103                 buf += n;
 104                 copied += n;
 105                 if (!m->count)
 106                         m->index++;
 107                 if (!size)
 108                         goto Done;
 109         }
 110         /* we need at least one record in buffer */
 111         pos = m->index;
 112         p = m->op->start(m, &pos);
 113         while (1) {
 114                 err = PTR_ERR(p);
 115                 if (!p || IS_ERR(p))
 116                         break;
 117                 err = m->op->show(m, p);
 118                 if (err < 0)
 119                         break;
 120                 if (unlikely(err))
 121                         m->count = 0;
 122                 if (unlikely(!m->count)) {
 123                         p = m->op->next(m, p, &pos);
 124                         m->index = pos;
 125                         continue;
 126                 }
 127                 if (m->count < m->size)
 128                         goto Fill;
 129                 m->op->stop(m, p);
 130                 kfree(m->buf);
 131                 m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
 132                 if (!m->buf)
 133                         goto Enomem;
 134                 m->count = 0;
 135                 m->version = 0;
 136                 pos = m->index;
 137                 p = m->op->start(m, &pos);
 138         }
 139         m->op->stop(m, p);
 140         m->count = 0;
 141         goto Done;
 142 Fill:
 143         /* they want more? let's try to get some more */
 144         while (m->count < size) {
 145                 size_t offs = m->count;
 146                 loff_t next = pos;
 147                 p = m->op->next(m, p, &next);
 148                 if (!p || IS_ERR(p)) {
 149                         err = PTR_ERR(p);
 150                         break;
 151                 }
 152                 err = m->op->show(m, p);
 153                 if (m->count == m->size || err) {
 154                         m->count = offs;
 155                         if (likely(err <= 0))
 156                                 break;
 157                 }
 158                 pos = next;
 159         }
 160         m->op->stop(m, p);
 161         n = min(m->count, size);
 162         err = copy_to_user(buf, m->buf, n);
 163         if (err)
 164                 goto Efault;
 165         copied += n;
 166         m->count -= n;
 167         if (m->count)
 168                 m->from = n;
 169         else
 170                 pos++;
 171         m->index = pos;
 172 Done:
 173         if (!copied)
 174                 copied = err;
 175         else
 176                 *ppos += copied;
 177         file->f_version = m->version;
 178         mutex_unlock(&m->lock);
 179         return copied;
 180 Enomem:
 181         err = -ENOMEM;
 182         goto Done;
 183 Efault:
 184         err = -EFAULT;
 185         goto Done;
 186 }
 187 EXPORT_SYMBOL(seq_read);
 188
 189 static int traverse(struct seq_file *m, loff_t offset)
 190 {
 191         loff_t pos = 0, index;
 192         int error = 0;
 193         void *p;
 194
 195         m->version = 0;
 196         index = 0;
 197         m->count = m->from = 0;
 198         if (!offset) {
 199                 m->index = index;
 200                 return 0;
 201         }
 202         if (!m->buf) {
 203                 m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
 204                 if (!m->buf)
 205                         return -ENOMEM;
 206         }
 207         p = m->op->start(m, &index);
 208         while (p) {
 209                 error = PTR_ERR(p);
 210                 if (IS_ERR(p))
 211                         break;
 212                 error = m->op->show(m, p);
 213                 if (error < 0)
 214                         break;
 215                 if (unlikely(error)) {
 216                         error = 0;
 217                         m->count = 0;
 218                 }
 219                 if (m->count == m->size)
 220                         goto Eoverflow;
 221                 if (pos + m->count > offset) {
 222                         m->from = offset - pos;
 223                         m->count -= m->from;
 224                         m->index = index;
 225                         break;
 226                 }
 227                 pos += m->count;
 228                 m->count = 0;
 229                 if (pos == offset) {
 230                         index++;
 231                         m->index = index;
 232                         break;
 233                 }
 234                 p = m->op->next(m, p, &index);
 235         }
 236         m->op->stop(m, p);
 237         return error;
 238
 239 Eoverflow:
 240         m->op->stop(m, p);
 241         kfree(m->buf);
 242         m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
 243         return !m->buf ? -ENOMEM : -EAGAIN;
 244 }
 245
 246 /**
 247  *      seq_lseek -     ->llseek() method for sequential files.
 248  *      @file: the file in question
 249  *      @offset: new position
 250  *      @origin: 0 for absolute, 1 for relative position
 251  *
 252  *      Ready-made ->f_op->llseek()
 253  */
 254 loff_t seq_lseek(struct file *file, loff_t offset, int origin)
 255 {
 256         struct seq_file *m = (struct seq_file *)file->private_data;
 257         loff_t retval = -EINVAL;
 258
 259         mutex_lock(&m->lock);
 260         m->version = file->f_version;
 261         switch (origin) {
 262                 case 1:
 263                         offset += file->f_pos;
 264                 case 0:
 265                         if (offset < 0)
 266                                 break;
 267                         retval = offset;
 268                         if (offset != file->f_pos) {
 269                                 while ((retval=traverse(m, offset)) == -EAGAIN)
 270                                         ;
 271                                 if (retval) {
 272                                         /* with extreme prejudice... */
 273                                         file->f_pos = 0;
 274                                         m->version = 0;
 275                                         m->index = 0;
 276                                         m->count = 0;
 277                                 } else {
 278                                         retval = file->f_pos = offset;
 279                                 }
 280                         }
 281         }
 282         file->f_version = m->version;
 283         mutex_unlock(&m->lock);
 284         return retval;
 285 }
 286 EXPORT_SYMBOL(seq_lseek);
 287
 288 /**
 289  *      seq_release -   free the structures associated with sequential file.
 290  *      @file: file in question
 291  *      @inode: file->f_path.dentry->d_inode
 292  *
 293  *      Frees the structures associated with sequential file; can be used
 294  *      as ->f_op->release() if you don't have private data to destroy.
 295  */
 296 int seq_release(struct inode *inode, struct file *file)
 297 {
 298         struct seq_file *m = (struct seq_file *)file->private_data;
 299         kfree(m->buf);
 300         kfree(m);
 301         return 0;
 302 }
 303 EXPORT_SYMBOL(seq_release);
 304
 305 /**
 306  *      seq_escape -    print string into buffer, escaping some characters
 307  *      @m:     target buffer
 308  *      @s:     string
 309  *      @esc:   set of characters that need escaping
 310  *
 311  *      Puts string into buffer, replacing each occurrence of character from
 312  *      @esc with usual octal escape.  Returns 0 in case of success, -1 - in
 313  *      case of overflow.
 314  */
 315 int seq_escape(struct seq_file *m, const char *s, const char *esc)
 316 {
 317         char *end = m->buf + m->size;
 318         char *p;
 319         char c;
 320
 321         for (p = m->buf + m->count; (c = *s) != '\0' && p < end; s++) {
 322                 if (!strchr(esc, c)) {
 323                         *p++ = c;
 324                         continue;
 325                 }
 326                 if (p + 3 < end) {
 327                         *p++ = '\\';
 328                         *p++ = '0' + ((c & 0300) >> 6);
 329                         *p++ = '0' + ((c & 070) >> 3);
 330                         *p++ = '0' + (c & 07);
 331                         continue;
 332                 }
 333                 m->count = m->size;
 334                 return -1;
 335         }
 336         m->count = p - m->buf;
 337         return 0;
 338 }
 339 EXPORT_SYMBOL(seq_escape);
 340
 341 int seq_printf(struct seq_file *m, const char *f, ...)
 342 {
 343         va_list args;
 344         int len;
 345
 346         if (m->count < m->size) {
 347                 va_start(args, f);
 348                 len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
 349                 va_end(args);
 350                 if (m->count + len < m->size) {
 351                         m->count += len;
 352                         return 0;
 353                 }
 354         }
 355         m->count = m->size;
 356         return -1;
 357 }
 358 EXPORT_SYMBOL(seq_printf);
 359
 360 static char *mangle_path(char *s, char *p, char *esc)
 361 {
 362         while (s <= p) {
 363                 char c = *p++;
 364                 if (!c) {
 365                         return s;
 366                 } else if (!strchr(esc, c)) {
 367                         *s++ = c;
 368                 } else if (s + 4 > p) {
 369                         break;
 370                 } else {
 371                         *s++ = '\\';
 372                         *s++ = '0' + ((c & 0300) >> 6);
 373                         *s++ = '0' + ((c & 070) >> 3);
 374                         *s++ = '0' + (c & 07);
 375                 }
 376         }
 377         return NULL;
 378 }
 379
 380 /*
 381  * return the absolute path of 'dentry' residing in mount 'mnt'.
 382  */
 383 int seq_path(struct seq_file *m, struct path *path, char *esc)
 384 {
 385         if (m->count < m->size) {
 386                 char *s = m->buf + m->count;
 387                 char *p = d_path(path, s, m->size - m->count);
 388                 if (!IS_ERR(p)) {
 389                         s = mangle_path(s, p, esc);
 390                         if (s) {
 391                                 p = m->buf + m->count;
 392                                 m->count = s - m->buf;
 393                                 return s - p;
 394                         }
 395                 }
 396         }
 397         m->count = m->size;
 398         return -1;
 399 }
 400 EXPORT_SYMBOL(seq_path);
 401
 402 /*
 403  * Same as seq_path, but relative to supplied root.
 404  *
 405  * root may be changed, see __d_path().
 406  */
 407 int seq_path_root(struct seq_file *m, struct path *path, struct path *root,
 408                   char *esc)
 409 {
 410         int err = -ENAMETOOLONG;
 411         if (m->count < m->size) {
 412                 char *s = m->buf + m->count;
 413                 char *p;
 414
 415                 spin_lock(&dcache_lock);
 416                 p = __d_path(path, root, s, m->size - m->count);
 417                 spin_unlock(&dcache_lock);
 418                 err = PTR_ERR(p);
 419                 if (!IS_ERR(p)) {
 420                         s = mangle_path(s, p, esc);
 421                         if (s) {
 422                                 p = m->buf + m->count;
 423                                 m->count = s - m->buf;
 424                                 return 0;
 425                         }
 426                 }
 427         }
 428         m->count = m->size;
 429         return err;
 430 }
 431
 432 /*
 433  * returns the path of the 'dentry' from the root of its filesystem.
 434  */
 435 int seq_dentry(struct seq_file *m, struct dentry *dentry, char *esc)
 436 {
 437         if (m->count < m->size) {
 438                 char *s = m->buf + m->count;
 439                 char *p = dentry_path(dentry, s, m->size - m->count);
 440                 if (!IS_ERR(p)) {
 441                         s = mangle_path(s, p, esc);
 442                         if (s) {
 443                                 p = m->buf + m->count;
 444                                 m->count = s - m->buf;
 445                                 return s - p;
 446                         }
 447                 }
 448         }
 449         m->count = m->size;
 450         return -1;
 451 }
 452
 453 int seq_bitmap(struct seq_file *m, unsigned long *bits, unsigned int nr_bits)
 454 {
 455         size_t len = bitmap_scnprintf_len(nr_bits);
 456
 457         if (m->count + len < m->size) {
 458                 bitmap_scnprintf(m->buf + m->count, m->size - m->count,
 459                                  bits, nr_bits);
 460                 m->count += len;
 461                 return 0;
 462         }
 463         m->count = m->size;
 464         return -1;
 465 }
 466
 467 static void *single_start(struct seq_file *p, loff_t *pos)
 468 {
 469         return NULL + (*pos == 0);
 470 }
 471
 472 static void *single_next(struct seq_file *p, void *v, loff_t *pos)
 473 {
 474         ++*pos;
 475         return NULL;
 476 }
 477
 478 static void single_stop(struct seq_file *p, void *v)
 479 {
 480 }
 481
 482 int single_open(struct file *file, int (*show)(struct seq_file *, void *),
 483                 void *data)
 484 {
 485         struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL);
 486         int res = -ENOMEM;
 487
 488         if (op) {
 489                 op->start = single_start;
 490                 op->next = single_next;
 491                 op->stop = single_stop;
 492                 op->show = show;
 493                 res = seq_open(file, op);
 494                 if (!res)
 495                         ((struct seq_file *)file->private_data)->private = data;
 496                 else
 497                         kfree(op);
 498         }
 499         return res;
 500 }
 501 EXPORT_SYMBOL(single_open);
 502
 503 int single_release(struct inode *inode, struct file *file)
 504 {
 505         const struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
 506         int res = seq_release(inode, file);
 507         kfree(op);
 508         return res;
 509 }
 510 EXPORT_SYMBOL(single_release);
 511
 512 int seq_release_private(struct inode *inode, struct file *file)
 513 {
 514         struct seq_file *seq = file->private_data;
 515
 516         kfree(seq->private);
 517         seq->private = NULL;
 518         return seq_release(inode, file);
 519 }
 520 EXPORT_SYMBOL(seq_release_private);
 521
 522 void *__seq_open_private(struct file *f, const struct seq_operations *ops,
 523                 int psize)
 524 {
 525         int rc;
 526         void *private;
 527         struct seq_file *seq;
 528
 529         private = kzalloc(psize, GFP_KERNEL);
 530         if (private == NULL)
 531                 goto out;
 532
 533         rc = seq_open(f, ops);
 534         if (rc < 0)
 535                 goto out_free;
 536
 537         seq = f->private_data;
 538         seq->private = private;
 539         return private;
 540
 541 out_free:
 542         kfree(private);
 543 out:
 544         return NULL;
 545 }
 546 EXPORT_SYMBOL(__seq_open_private);
 547
 548 int seq_open_private(struct file *filp, const struct seq_operations *ops,
 549                 int psize)
 550 {
 551         return __seq_open_private(filp, ops, psize) ? 0 : -ENOMEM;
 552 }
 553 EXPORT_SYMBOL(seq_open_private);
 554
 555 int seq_putc(struct seq_file *m, char c)
 556 {
 557         if (m->count < m->size) {
 558                 m->buf[m->count++] = c;
 559                 return 0;
 560         }
 561         return -1;
 562 }
 563 EXPORT_SYMBOL(seq_putc);
 564
 565 int seq_puts(struct seq_file *m, const char *s)
 566 {
 567         int len = strlen(s);
 568         if (m->count + len < m->size) {
 569                 memcpy(m->buf + m->count, s, len);
 570                 m->count += len;
 571                 return 0;
 572         }
 573         m->count = m->size;
 574         return -1;
 575 }
 576 EXPORT_SYMBOL(seq_puts);
 577
 578 struct list_head *seq_list_start(struct list_head *head, loff_t pos)
 579 {
 580         struct list_head *lh;
 581
 582         list_for_each(lh, head)
 583                 if (pos-- == 0)
 584                         return lh;
 585
 586         return NULL;
 587 }
 588
 589 EXPORT_SYMBOL(seq_list_start);
 590
 591 struct list_head *seq_list_start_head(struct list_head *head, loff_t pos)
 592 {
 593         if (!pos)
 594                 return head;
 595
 596         return seq_list_start(head, pos - 1);
 597 }
 598
 599 EXPORT_SYMBOL(seq_list_start_head);
 600
 601 struct list_head *seq_list_next(void *v, struct list_head *head, loff_t *ppos)
 602 {
 603         struct list_head *lh;
 604
 605         lh = ((struct list_head *)v)->next;
 606         ++*ppos;
 607         return lh == head ? NULL : lh;
 608 }
 609
 610 EXPORT_SYMBOL(seq_list_next);