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         /*
  52          * seq_files support lseek() and pread().  They do not implement
  53          * write() at all, but we clear FMODE_PWRITE here for historical
  54          * reasons.
  55          *
  56          * If a client of seq_files a) implements file.write() and b) wishes to
  57          * support pwrite() then that client will need to implement its own
  58          * file.open() which calls seq_open() and then sets FMODE_PWRITE.
  59          */
  60         file->f_mode &= ~FMODE_PWRITE;
  61         return 0;
  62 }
  63 EXPORT_SYMBOL(seq_open);
  64
  65 static int traverse(struct seq_file *m, loff_t offset)
  66 {
  67         loff_t pos = 0, index;
  68         int error = 0;
  69         void *p;
  70
  71         m->version = 0;
  72         index = 0;
  73         m->count = m->from = 0;
  74         if (!offset) {
  75                 m->index = index;
  76                 return 0;
  77         }
  78         if (!m->buf) {
  79                 m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
  80                 if (!m->buf)
  81                         return -ENOMEM;
  82         }
  83         p = m->op->start(m, &index);
  84         while (p) {
  85                 error = PTR_ERR(p);
  86                 if (IS_ERR(p))
  87                         break;
  88                 error = m->op->show(m, p);
  89                 if (error < 0)
  90                         break;
  91                 if (unlikely(error)) {
  92                         error = 0;
  93                         m->count = 0;
  94                 }
  95                 if (m->count == m->size)
  96                         goto Eoverflow;
  97                 if (pos + m->count > offset) {
  98                         m->from = offset - pos;
  99                         m->count -= m->from;
 100                         m->index = index;
 101                         break;
 102                 }
 103                 pos += m->count;
 104                 m->count = 0;
 105                 if (pos == offset) {
 106                         index++;
 107                         m->index = index;
 108                         break;
 109                 }
 110                 p = m->op->next(m, p, &index);
 111         }
 112         m->op->stop(m, p);
 113         m->index = index;
 114         return error;
 115
 116 Eoverflow:
 117         m->op->stop(m, p);
 118         kfree(m->buf);
 119         m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
 120         return !m->buf ? -ENOMEM : -EAGAIN;
 121 }
 122
 123 /**
 124  *      seq_read -      ->read() method for sequential files.
 125  *      @file: the file to read from
 126  *      @buf: the buffer to read to
 127  *      @size: the maximum number of bytes to read
 128  *      @ppos: the current position in the file
 129  *
 130  *      Ready-made ->f_op->read()
 131  */
 132 ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
 133 {
 134         struct seq_file *m = (struct seq_file *)file->private_data;
 135         size_t copied = 0;
 136         loff_t pos;
 137         size_t n;
 138         void *p;
 139         int err = 0;
 140
 141         mutex_lock(&m->lock);
 142
 143         /* Don't assume *ppos is where we left it */
 144         if (unlikely(*ppos != m->read_pos)) {
 145                 m->read_pos = *ppos;
 146                 while ((err = traverse(m, *ppos)) == -EAGAIN)
 147                         ;
 148                 if (err) {
 149                         /* With prejudice... */
 150                         m->read_pos = 0;
 151                         m->version = 0;
 152                         m->index = 0;
 153                         m->count = 0;
 154                         goto Done;
 155                 }
 156         }
 157
 158         /*
 159          * seq_file->op->..m_start/m_stop/m_next may do special actions
 160          * or optimisations based on the file->f_version, so we want to
 161          * pass the file->f_version to those methods.
 162          *
 163          * seq_file->version is just copy of f_version, and seq_file
 164          * methods can treat it simply as file version.
 165          * It is copied in first and copied out after all operations.
 166          * It is convenient to have it as  part of structure to avoid the
 167          * need of passing another argument to all the seq_file methods.
 168          */
 169         m->version = file->f_version;
 170         /* grab buffer if we didn't have one */
 171         if (!m->buf) {
 172                 m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
 173                 if (!m->buf)
 174                         goto Enomem;
 175         }
 176         /* if not empty - flush it first */
 177         if (m->count) {
 178                 n = min(m->count, size);
 179                 err = copy_to_user(buf, m->buf + m->from, n);
 180                 if (err)
 181                         goto Efault;
 182                 m->count -= n;
 183                 m->from += n;
 184                 size -= n;
 185                 buf += n;
 186                 copied += n;
 187                 if (!m->count)
 188                         m->index++;
 189                 if (!size)
 190                         goto Done;
 191         }
 192         /* we need at least one record in buffer */
 193         pos = m->index;
 194         p = m->op->start(m, &pos);
 195         while (1) {
 196                 err = PTR_ERR(p);
 197                 if (!p || IS_ERR(p))
 198                         break;
 199                 err = m->op->show(m, p);
 200                 if (err < 0)
 201                         break;
 202                 if (unlikely(err))
 203                         m->count = 0;
 204                 if (unlikely(!m->count)) {
 205                         p = m->op->next(m, p, &pos);
 206                         m->index = pos;
 207                         continue;
 208                 }
 209                 if (m->count < m->size)
 210                         goto Fill;
 211                 m->op->stop(m, p);
 212                 kfree(m->buf);
 213                 m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
 214                 if (!m->buf)
 215                         goto Enomem;
 216                 m->count = 0;
 217                 m->version = 0;
 218                 pos = m->index;
 219                 p = m->op->start(m, &pos);
 220         }
 221         m->op->stop(m, p);
 222         m->count = 0;
 223         goto Done;
 224 Fill:
 225         /* they want more? let's try to get some more */
 226         while (m->count < size) {
 227                 size_t offs = m->count;
 228                 loff_t next = pos;
 229                 p = m->op->next(m, p, &next);
 230                 if (!p || IS_ERR(p)) {
 231                         err = PTR_ERR(p);
 232                         break;
 233                 }
 234                 err = m->op->show(m, p);
 235                 if (m->count == m->size || err) {
 236                         m->count = offs;
 237                         if (likely(err <= 0))
 238                                 break;
 239                 }
 240                 pos = next;
 241         }
 242         m->op->stop(m, p);
 243         n = min(m->count, size);
 244         err = copy_to_user(buf, m->buf, n);
 245         if (err)
 246                 goto Efault;
 247         copied += n;
 248         m->count -= n;
 249         if (m->count)
 250                 m->from = n;
 251         else
 252                 pos++;
 253         m->index = pos;
 254 Done:
 255         if (!copied)
 256                 copied = err;
 257         else {
 258                 *ppos += copied;
 259                 m->read_pos += copied;
 260         }
 261         file->f_version = m->version;
 262         mutex_unlock(&m->lock);
 263         return copied;
 264 Enomem:
 265         err = -ENOMEM;
 266         goto Done;
 267 Efault:
 268         err = -EFAULT;
 269         goto Done;
 270 }
 271 EXPORT_SYMBOL(seq_read);
 272
 273 /**
 274  *      seq_lseek -     ->llseek() method for sequential files.
 275  *      @file: the file in question
 276  *      @offset: new position
 277  *      @origin: 0 for absolute, 1 for relative position
 278  *
 279  *      Ready-made ->f_op->llseek()
 280  */
 281 loff_t seq_lseek(struct file *file, loff_t offset, int origin)
 282 {
 283         struct seq_file *m = (struct seq_file *)file->private_data;
 284         loff_t retval = -EINVAL;
 285
 286         mutex_lock(&m->lock);
 287         m->version = file->f_version;
 288         switch (origin) {
 289                 case 1:
 290                         offset += file->f_pos;
 291                 case 0:
 292                         if (offset < 0)
 293                                 break;
 294                         retval = offset;
 295                         if (offset != m->read_pos) {
 296                                 while ((retval=traverse(m, offset)) == -EAGAIN)
 297                                         ;
 298                                 if (retval) {
 299                                         /* with extreme prejudice... */
 300                                         file->f_pos = 0;
 301                                         m->read_pos = 0;
 302                                         m->version = 0;
 303                                         m->index = 0;
 304                                         m->count = 0;
 305                                 } else {
 306                                         m->read_pos = offset;
 307                                         retval = file->f_pos = offset;
 308                                 }
 309                         }
 310         }
 311         file->f_version = m->version;
 312         mutex_unlock(&m->lock);
 313         return retval;
 314 }
 315 EXPORT_SYMBOL(seq_lseek);
 316
 317 /**
 318  *      seq_release -   free the structures associated with sequential file.
 319  *      @file: file in question
 320  *      @inode: file->f_path.dentry->d_inode
 321  *
 322  *      Frees the structures associated with sequential file; can be used
 323  *      as ->f_op->release() if you don't have private data to destroy.
 324  */
 325 int seq_release(struct inode *inode, struct file *file)
 326 {
 327         struct seq_file *m = (struct seq_file *)file->private_data;
 328         kfree(m->buf);
 329         kfree(m);
 330         return 0;
 331 }
 332 EXPORT_SYMBOL(seq_release);
 333
 334 /**
 335  *      seq_escape -    print string into buffer, escaping some characters
 336  *      @m:     target buffer
 337  *      @s:     string
 338  *      @esc:   set of characters that need escaping
 339  *
 340  *      Puts string into buffer, replacing each occurrence of character from
 341  *      @esc with usual octal escape.  Returns 0 in case of success, -1 - in
 342  *      case of overflow.
 343  */
 344 int seq_escape(struct seq_file *m, const char *s, const char *esc)
 345 {
 346         char *end = m->buf + m->size;
 347         char *p;
 348         char c;
 349
 350         for (p = m->buf + m->count; (c = *s) != '\0' && p < end; s++) {
 351                 if (!strchr(esc, c)) {
 352                         *p++ = c;
 353                         continue;
 354                 }
 355                 if (p + 3 < end) {
 356                         *p++ = '\\';
 357                         *p++ = '0' + ((c & 0300) >> 6);
 358                         *p++ = '0' + ((c & 070) >> 3);
 359                         *p++ = '0' + (c & 07);
 360                         continue;
 361                 }
 362                 m->count = m->size;
 363                 return -1;
 364         }
 365         m->count = p - m->buf;
 366         return 0;
 367 }
 368 EXPORT_SYMBOL(seq_escape);
 369
 370 int seq_printf(struct seq_file *m, const char *f, ...)
 371 {
 372         va_list args;
 373         int len;
 374
 375         if (m->count < m->size) {
 376                 va_start(args, f);
 377                 len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
 378                 va_end(args);
 379                 if (m->count + len < m->size) {
 380                         m->count += len;
 381                         return 0;
 382                 }
 383         }
 384         m->count = m->size;
 385         return -1;
 386 }
 387 EXPORT_SYMBOL(seq_printf);
 388
 389 static char *mangle_path(char *s, char *p, char *esc)
 390 {
 391         while (s <= p) {
 392                 char c = *p++;
 393                 if (!c) {
 394                         return s;
 395                 } else if (!strchr(esc, c)) {
 396                         *s++ = c;
 397                 } else if (s + 4 > p) {
 398                         break;
 399                 } else {
 400                         *s++ = '\\';
 401                         *s++ = '0' + ((c & 0300) >> 6);
 402                         *s++ = '0' + ((c & 070) >> 3);
 403                         *s++ = '0' + (c & 07);
 404                 }
 405         }
 406         return NULL;
 407 }
 408
 409 /*
 410  * return the absolute path of 'dentry' residing in mount 'mnt'.
 411  */
 412 int seq_path(struct seq_file *m, struct path *path, char *esc)
 413 {
 414         if (m->count < m->size) {
 415                 char *s = m->buf + m->count;
 416                 char *p = d_path(path, s, m->size - m->count);
 417                 if (!IS_ERR(p)) {
 418                         s = mangle_path(s, p, esc);
 419                         if (s) {
 420                                 p = m->buf + m->count;
 421                                 m->count = s - m->buf;
 422                                 return s - p;
 423                         }
 424                 }
 425         }
 426         m->count = m->size;
 427         return -1;
 428 }
 429 EXPORT_SYMBOL(seq_path);
 430
 431 /*
 432  * Same as seq_path, but relative to supplied root.
 433  *
 434  * root may be changed, see __d_path().
 435  */
 436 int seq_path_root(struct seq_file *m, struct path *path, struct path *root,
 437                   char *esc)
 438 {
 439         int err = -ENAMETOOLONG;
 440         if (m->count < m->size) {
 441                 char *s = m->buf + m->count;
 442                 char *p;
 443
 444                 spin_lock(&dcache_lock);
 445                 p = __d_path(path, root, s, m->size - m->count);
 446                 spin_unlock(&dcache_lock);
 447                 err = PTR_ERR(p);
 448                 if (!IS_ERR(p)) {
 449                         s = mangle_path(s, p, esc);
 450                         if (s) {
 451                                 p = m->buf + m->count;
 452                                 m->count = s - m->buf;
 453                                 return 0;
 454                         }
 455                 }
 456         }
 457         m->count = m->size;
 458         return err;
 459 }
 460
 461 /*
 462  * returns the path of the 'dentry' from the root of its filesystem.
 463  */
 464 int seq_dentry(struct seq_file *m, struct dentry *dentry, char *esc)
 465 {
 466         if (m->count < m->size) {
 467                 char *s = m->buf + m->count;
 468                 char *p = dentry_path(dentry, s, m->size - m->count);
 469                 if (!IS_ERR(p)) {
 470                         s = mangle_path(s, p, esc);
 471                         if (s) {
 472                                 p = m->buf + m->count;
 473                                 m->count = s - m->buf;
 474                                 return s - p;
 475                         }
 476                 }
 477         }
 478         m->count = m->size;
 479         return -1;
 480 }
 481
 482 int seq_bitmap(struct seq_file *m, unsigned long *bits, unsigned int nr_bits)
 483 {
 484         if (m->count < m->size) {
 485                 int len = bitmap_scnprintf(m->buf + m->count,
 486                                 m->size - m->count, bits, nr_bits);
 487                 if (m->count + len < m->size) {
 488                         m->count += len;
 489                         return 0;
 490                 }
 491         }
 492         m->count = m->size;
 493         return -1;
 494 }
 495 EXPORT_SYMBOL(seq_bitmap);
 496
 497 int seq_bitmap_list(struct seq_file *m, unsigned long *bits,
 498                 unsigned int nr_bits)
 499 {
 500         if (m->count < m->size) {
 501                 int len = bitmap_scnlistprintf(m->buf + m->count,
 502                                 m->size - m->count, bits, nr_bits);
 503                 if (m->count + len < m->size) {
 504                         m->count += len;
 505                         return 0;
 506                 }
 507         }
 508         m->count = m->size;
 509         return -1;
 510 }
 511 EXPORT_SYMBOL(seq_bitmap_list);
 512
 513 static void *single_start(struct seq_file *p, loff_t *pos)
 514 {
 515         return NULL + (*pos == 0);
 516 }
 517
 518 static void *single_next(struct seq_file *p, void *v, loff_t *pos)
 519 {
 520         ++*pos;
 521         return NULL;
 522 }
 523
 524 static void single_stop(struct seq_file *p, void *v)
 525 {
 526 }
 527
 528 int single_open(struct file *file, int (*show)(struct seq_file *, void *),
 529                 void *data)
 530 {
 531         struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL);
 532         int res = -ENOMEM;
 533
 534         if (op) {
 535                 op->start = single_start;
 536                 op->next = single_next;
 537                 op->stop = single_stop;
 538                 op->show = show;
 539                 res = seq_open(file, op);
 540                 if (!res)
 541                         ((struct seq_file *)file->private_data)->private = data;
 542                 else
 543                         kfree(op);
 544         }
 545         return res;
 546 }
 547 EXPORT_SYMBOL(single_open);
 548
 549 int single_release(struct inode *inode, struct file *file)
 550 {
 551         const struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
 552         int res = seq_release(inode, file);
 553         kfree(op);
 554         return res;
 555 }
 556 EXPORT_SYMBOL(single_release);
 557
 558 int seq_release_private(struct inode *inode, struct file *file)
 559 {
 560         struct seq_file *seq = file->private_data;
 561
 562         kfree(seq->private);
 563         seq->private = NULL;
 564         return seq_release(inode, file);
 565 }
 566 EXPORT_SYMBOL(seq_release_private);
 567
 568 void *__seq_open_private(struct file *f, const struct seq_operations *ops,
 569                 int psize)
 570 {
 571         int rc;
 572         void *private;
 573         struct seq_file *seq;
 574
 575         private = kzalloc(psize, GFP_KERNEL);
 576         if (private == NULL)
 577                 goto out;
 578
 579         rc = seq_open(f, ops);
 580         if (rc < 0)
 581                 goto out_free;
 582
 583         seq = f->private_data;
 584         seq->private = private;
 585         return private;
 586
 587 out_free:
 588         kfree(private);
 589 out:
 590         return NULL;
 591 }
 592 EXPORT_SYMBOL(__seq_open_private);
 593
 594 int seq_open_private(struct file *filp, const struct seq_operations *ops,
 595                 int psize)
 596 {
 597         return __seq_open_private(filp, ops, psize) ? 0 : -ENOMEM;
 598 }
 599 EXPORT_SYMBOL(seq_open_private);
 600
 601 int seq_putc(struct seq_file *m, char c)
 602 {
 603         if (m->count < m->size) {
 604                 m->buf[m->count++] = c;
 605                 return 0;
 606         }
 607         return -1;
 608 }
 609 EXPORT_SYMBOL(seq_putc);
 610
 611 int seq_puts(struct seq_file *m, const char *s)
 612 {
 613         int len = strlen(s);
 614         if (m->count + len < m->size) {
 615                 memcpy(m->buf + m->count, s, len);
 616                 m->count += len;
 617                 return 0;
 618         }
 619         m->count = m->size;
 620         return -1;
 621 }
 622 EXPORT_SYMBOL(seq_puts);
 623
 624 struct list_head *seq_list_start(struct list_head *head, loff_t pos)
 625 {
 626         struct list_head *lh;
 627
 628         list_for_each(lh, head)
 629                 if (pos-- == 0)
 630                         return lh;
 631
 632         return NULL;
 633 }
 634
 635 EXPORT_SYMBOL(seq_list_start);
 636
 637 struct list_head *seq_list_start_head(struct list_head *head, loff_t pos)
 638 {
 639         if (!pos)
 640                 return head;
 641
 642         return seq_list_start(head, pos - 1);
 643 }
 644
 645 EXPORT_SYMBOL(seq_list_start_head);
 646
 647 struct list_head *seq_list_next(void *v, struct list_head *head, loff_t *ppos)
 648 {
 649         struct list_head *lh;
 650
 651         lh = ((struct list_head *)v)->next;
 652         ++*ppos;
 653         return lh == head ? NULL : lh;
 654 }
 655
 656 EXPORT_SYMBOL(seq_list_next);