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 /**
 390  *      mangle_path -   mangle and copy path to buffer beginning
 391  *      @s: buffer start
 392  *      @p: beginning of path in above buffer
 393  *      @esc: set of characters that need escaping
 394  *
 395  *      Copy the path from @p to @s, replacing each occurrence of character from
 396  *      @esc with usual octal escape.
 397  *      Returns pointer past last written character in @s, or NULL in case of
 398  *      failure.
 399  */
 400 char *mangle_path(char *s, char *p, char *esc)
 401 {
 402         while (s <= p) {
 403                 char c = *p++;
 404                 if (!c) {
 405                         return s;
 406                 } else if (!strchr(esc, c)) {
 407                         *s++ = c;
 408                 } else if (s + 4 > p) {
 409                         break;
 410                 } else {
 411                         *s++ = '\\';
 412                         *s++ = '0' + ((c & 0300) >> 6);
 413                         *s++ = '0' + ((c & 070) >> 3);
 414                         *s++ = '0' + (c & 07);
 415                 }
 416         }
 417         return NULL;
 418 }
 419 EXPORT_SYMBOL(mangle_path);
 420
 421 /**
 422  * seq_path - seq_file interface to print a pathname
 423  * @m: the seq_file handle
 424  * @path: the struct path to print
 425  * @esc: set of characters to escape in the output
 426  *
 427  * return the absolute path of 'path', as represented by the
 428  * dentry / mnt pair in the path parameter.
 429  */
 430 int seq_path(struct seq_file *m, struct path *path, char *esc)
 431 {
 432         if (m->count < m->size) {
 433                 char *s = m->buf + m->count;
 434                 char *p = d_path(path, s, m->size - m->count);
 435                 if (!IS_ERR(p)) {
 436                         s = mangle_path(s, p, esc);
 437                         if (s) {
 438                                 p = m->buf + m->count;
 439                                 m->count = s - m->buf;
 440                                 return s - p;
 441                         }
 442                 }
 443         }
 444         m->count = m->size;
 445         return -1;
 446 }
 447 EXPORT_SYMBOL(seq_path);
 448
 449 /*
 450  * Same as seq_path, but relative to supplied root.
 451  *
 452  * root may be changed, see __d_path().
 453  */
 454 int seq_path_root(struct seq_file *m, struct path *path, struct path *root,
 455                   char *esc)
 456 {
 457         int err = -ENAMETOOLONG;
 458         if (m->count < m->size) {
 459                 char *s = m->buf + m->count;
 460                 char *p;
 461
 462                 spin_lock(&dcache_lock);
 463                 p = __d_path(path, root, s, m->size - m->count);
 464                 spin_unlock(&dcache_lock);
 465                 err = PTR_ERR(p);
 466                 if (!IS_ERR(p)) {
 467                         s = mangle_path(s, p, esc);
 468                         if (s) {
 469                                 p = m->buf + m->count;
 470                                 m->count = s - m->buf;
 471                                 return 0;
 472                         }
 473                 }
 474         }
 475         m->count = m->size;
 476         return err;
 477 }
 478
 479 /*
 480  * returns the path of the 'dentry' from the root of its filesystem.
 481  */
 482 int seq_dentry(struct seq_file *m, struct dentry *dentry, char *esc)
 483 {
 484         if (m->count < m->size) {
 485                 char *s = m->buf + m->count;
 486                 char *p = dentry_path(dentry, s, m->size - m->count);
 487                 if (!IS_ERR(p)) {
 488                         s = mangle_path(s, p, esc);
 489                         if (s) {
 490                                 p = m->buf + m->count;
 491                                 m->count = s - m->buf;
 492                                 return s - p;
 493                         }
 494                 }
 495         }
 496         m->count = m->size;
 497         return -1;
 498 }
 499
 500 int seq_bitmap(struct seq_file *m, const unsigned long *bits,
 501                                    unsigned int nr_bits)
 502 {
 503         if (m->count < m->size) {
 504                 int len = bitmap_scnprintf(m->buf + m->count,
 505                                 m->size - m->count, bits, nr_bits);
 506                 if (m->count + len < m->size) {
 507                         m->count += len;
 508                         return 0;
 509                 }
 510         }
 511         m->count = m->size;
 512         return -1;
 513 }
 514 EXPORT_SYMBOL(seq_bitmap);
 515
 516 int seq_bitmap_list(struct seq_file *m, const unsigned long *bits,
 517                 unsigned int nr_bits)
 518 {
 519         if (m->count < m->size) {
 520                 int len = bitmap_scnlistprintf(m->buf + m->count,
 521                                 m->size - m->count, bits, nr_bits);
 522                 if (m->count + len < m->size) {
 523                         m->count += len;
 524                         return 0;
 525                 }
 526         }
 527         m->count = m->size;
 528         return -1;
 529 }
 530 EXPORT_SYMBOL(seq_bitmap_list);
 531
 532 static void *single_start(struct seq_file *p, loff_t *pos)
 533 {
 534         return NULL + (*pos == 0);
 535 }
 536
 537 static void *single_next(struct seq_file *p, void *v, loff_t *pos)
 538 {
 539         ++*pos;
 540         return NULL;
 541 }
 542
 543 static void single_stop(struct seq_file *p, void *v)
 544 {
 545 }
 546
 547 int single_open(struct file *file, int (*show)(struct seq_file *, void *),
 548                 void *data)
 549 {
 550         struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL);
 551         int res = -ENOMEM;
 552
 553         if (op) {
 554                 op->start = single_start;
 555                 op->next = single_next;
 556                 op->stop = single_stop;
 557                 op->show = show;
 558                 res = seq_open(file, op);
 559                 if (!res)
 560                         ((struct seq_file *)file->private_data)->private = data;
 561                 else
 562                         kfree(op);
 563         }
 564         return res;
 565 }
 566 EXPORT_SYMBOL(single_open);
 567
 568 int single_release(struct inode *inode, struct file *file)
 569 {
 570         const struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
 571         int res = seq_release(inode, file);
 572         kfree(op);
 573         return res;
 574 }
 575 EXPORT_SYMBOL(single_release);
 576
 577 int seq_release_private(struct inode *inode, struct file *file)
 578 {
 579         struct seq_file *seq = file->private_data;
 580
 581         kfree(seq->private);
 582         seq->private = NULL;
 583         return seq_release(inode, file);
 584 }
 585 EXPORT_SYMBOL(seq_release_private);
 586
 587 void *__seq_open_private(struct file *f, const struct seq_operations *ops,
 588                 int psize)
 589 {
 590         int rc;
 591         void *private;
 592         struct seq_file *seq;
 593
 594         private = kzalloc(psize, GFP_KERNEL);
 595         if (private == NULL)
 596                 goto out;
 597
 598         rc = seq_open(f, ops);
 599         if (rc < 0)
 600                 goto out_free;
 601
 602         seq = f->private_data;
 603         seq->private = private;
 604         return private;
 605
 606 out_free:
 607         kfree(private);
 608 out:
 609         return NULL;
 610 }
 611 EXPORT_SYMBOL(__seq_open_private);
 612
 613 int seq_open_private(struct file *filp, const struct seq_operations *ops,
 614                 int psize)
 615 {
 616         return __seq_open_private(filp, ops, psize) ? 0 : -ENOMEM;
 617 }
 618 EXPORT_SYMBOL(seq_open_private);
 619
 620 int seq_putc(struct seq_file *m, char c)
 621 {
 622         if (m->count < m->size) {
 623                 m->buf[m->count++] = c;
 624                 return 0;
 625         }
 626         return -1;
 627 }
 628 EXPORT_SYMBOL(seq_putc);
 629
 630 int seq_puts(struct seq_file *m, const char *s)
 631 {
 632         int len = strlen(s);
 633         if (m->count + len < m->size) {
 634                 memcpy(m->buf + m->count, s, len);
 635                 m->count += len;
 636                 return 0;
 637         }
 638         m->count = m->size;
 639         return -1;
 640 }
 641 EXPORT_SYMBOL(seq_puts);
 642
 643 struct list_head *seq_list_start(struct list_head *head, loff_t pos)
 644 {
 645         struct list_head *lh;
 646
 647         list_for_each(lh, head)
 648                 if (pos-- == 0)
 649                         return lh;
 650
 651         return NULL;
 652 }
 653
 654 EXPORT_SYMBOL(seq_list_start);
 655
 656 struct list_head *seq_list_start_head(struct list_head *head, loff_t pos)
 657 {
 658         if (!pos)
 659                 return head;
 660
 661         return seq_list_start(head, pos - 1);
 662 }
 663
 664 EXPORT_SYMBOL(seq_list_start_head);
 665
 666 struct list_head *seq_list_next(void *v, struct list_head *head, loff_t *ppos)
 667 {
 668         struct list_head *lh;
 669
 670         lh = ((struct list_head *)v)->next;
 671         ++*ppos;
 672         return lh == head ? NULL : lh;
 673 }
 674
 675 EXPORT_SYMBOL(seq_list_next);