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