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 /**
 361  *      mangle_path -   mangle and copy path to buffer beginning
 362  *      @s: buffer start
 363  *      @p: beginning of path in above buffer
 364  *      @esc: set of characters that need escaping
 365  *
 366  *      Copy the path from @p to @s, replacing each occurrence of character from
 367  *      @esc with usual octal escape.
 368  *      Returns pointer past last written character in @s, or NULL in case of
 369  *      failure.
 370  */
 371 char *mangle_path(char *s, char *p, char *esc)
 372 {
 373         while (s <= p) {
 374                 char c = *p++;
 375                 if (!c) {
 376                         return s;
 377                 } else if (!strchr(esc, c)) {
 378                         *s++ = c;
 379                 } else if (s + 4 > p) {
 380                         break;
 381                 } else {
 382                         *s++ = '\\';
 383                         *s++ = '0' + ((c & 0300) >> 6);
 384                         *s++ = '0' + ((c & 070) >> 3);
 385                         *s++ = '0' + (c & 07);
 386                 }
 387         }
 388         return NULL;
 389 }
 390 EXPORT_SYMBOL(mangle_path);
 391
 392 /**
 393  * seq_path - seq_file interface to print a pathname
 394  * @m: the seq_file handle
 395  * @path: the struct path to print
 396  * @esc: set of characters to escape in the output
 397  *
 398  * return the absolute path of 'path', as represented by the
 399  * dentry / mnt pair in the path parameter.
 400  */
 401 int seq_path(struct seq_file *m, struct path *path, char *esc)
 402 {
 403         if (m->count < m->size) {
 404                 char *s = m->buf + m->count;
 405                 char *p = d_path(path, s, m->size - m->count);
 406                 if (!IS_ERR(p)) {
 407                         s = mangle_path(s, p, esc);
 408                         if (s) {
 409                                 p = m->buf + m->count;
 410                                 m->count = s - m->buf;
 411                                 return s - p;
 412                         }
 413                 }
 414         }
 415         m->count = m->size;
 416         return -1;
 417 }
 418 EXPORT_SYMBOL(seq_path);
 419
 420 /*
 421  * Same as seq_path, but relative to supplied root.
 422  *
 423  * root may be changed, see __d_path().
 424  */
 425 int seq_path_root(struct seq_file *m, struct path *path, struct path *root,
 426                   char *esc)
 427 {
 428         int err = -ENAMETOOLONG;
 429         if (m->count < m->size) {
 430                 char *s = m->buf + m->count;
 431                 char *p;
 432
 433                 spin_lock(&dcache_lock);
 434                 p = __d_path(path, root, s, m->size - m->count);
 435                 spin_unlock(&dcache_lock);
 436                 err = PTR_ERR(p);
 437                 if (!IS_ERR(p)) {
 438                         s = mangle_path(s, p, esc);
 439                         if (s) {
 440                                 p = m->buf + m->count;
 441                                 m->count = s - m->buf;
 442                                 return 0;
 443                         }
 444                 }
 445         }
 446         m->count = m->size;
 447         return err;
 448 }
 449
 450 /*
 451  * returns the path of the 'dentry' from the root of its filesystem.
 452  */
 453 int seq_dentry(struct seq_file *m, struct dentry *dentry, char *esc)
 454 {
 455         if (m->count < m->size) {
 456                 char *s = m->buf + m->count;
 457                 char *p = dentry_path(dentry, s, m->size - m->count);
 458                 if (!IS_ERR(p)) {
 459                         s = mangle_path(s, p, esc);
 460                         if (s) {
 461                                 p = m->buf + m->count;
 462                                 m->count = s - m->buf;
 463                                 return s - p;
 464                         }
 465                 }
 466         }
 467         m->count = m->size;
 468         return -1;
 469 }
 470
 471 int seq_bitmap(struct seq_file *m, const unsigned long *bits,
 472                                    unsigned int nr_bits)
 473 {
 474         if (m->count < m->size) {
 475                 int len = bitmap_scnprintf(m->buf + m->count,
 476                                 m->size - m->count, bits, nr_bits);
 477                 if (m->count + len < m->size) {
 478                         m->count += len;
 479                         return 0;
 480                 }
 481         }
 482         m->count = m->size;
 483         return -1;
 484 }
 485 EXPORT_SYMBOL(seq_bitmap);
 486
 487 int seq_bitmap_list(struct seq_file *m, unsigned long *bits,
 488                 unsigned int nr_bits)
 489 {
 490         if (m->count < m->size) {
 491                 int len = bitmap_scnlistprintf(m->buf + m->count,
 492                                 m->size - m->count, bits, nr_bits);
 493                 if (m->count + len < m->size) {
 494                         m->count += len;
 495                         return 0;
 496                 }
 497         }
 498         m->count = m->size;
 499         return -1;
 500 }
 501 EXPORT_SYMBOL(seq_bitmap_list);
 502
 503 static void *single_start(struct seq_file *p, loff_t *pos)
 504 {
 505         return NULL + (*pos == 0);
 506 }
 507
 508 static void *single_next(struct seq_file *p, void *v, loff_t *pos)
 509 {
 510         ++*pos;
 511         return NULL;
 512 }
 513
 514 static void single_stop(struct seq_file *p, void *v)
 515 {
 516 }
 517
 518 int single_open(struct file *file, int (*show)(struct seq_file *, void *),
 519                 void *data)
 520 {
 521         struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL);
 522         int res = -ENOMEM;
 523
 524         if (op) {
 525                 op->start = single_start;
 526                 op->next = single_next;
 527                 op->stop = single_stop;
 528                 op->show = show;
 529                 res = seq_open(file, op);
 530                 if (!res)
 531                         ((struct seq_file *)file->private_data)->private = data;
 532                 else
 533                         kfree(op);
 534         }
 535         return res;
 536 }
 537 EXPORT_SYMBOL(single_open);
 538
 539 int single_release(struct inode *inode, struct file *file)
 540 {
 541         const struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
 542         int res = seq_release(inode, file);
 543         kfree(op);
 544         return res;
 545 }
 546 EXPORT_SYMBOL(single_release);
 547
 548 int seq_release_private(struct inode *inode, struct file *file)
 549 {
 550         struct seq_file *seq = file->private_data;
 551
 552         kfree(seq->private);
 553         seq->private = NULL;
 554         return seq_release(inode, file);
 555 }
 556 EXPORT_SYMBOL(seq_release_private);
 557
 558 void *__seq_open_private(struct file *f, const struct seq_operations *ops,
 559                 int psize)
 560 {
 561         int rc;
 562         void *private;
 563         struct seq_file *seq;
 564
 565         private = kzalloc(psize, GFP_KERNEL);
 566         if (private == NULL)
 567                 goto out;
 568
 569         rc = seq_open(f, ops);
 570         if (rc < 0)
 571                 goto out_free;
 572
 573         seq = f->private_data;
 574         seq->private = private;
 575         return private;
 576
 577 out_free:
 578         kfree(private);
 579 out:
 580         return NULL;
 581 }
 582 EXPORT_SYMBOL(__seq_open_private);
 583
 584 int seq_open_private(struct file *filp, const struct seq_operations *ops,
 585                 int psize)
 586 {
 587         return __seq_open_private(filp, ops, psize) ? 0 : -ENOMEM;
 588 }
 589 EXPORT_SYMBOL(seq_open_private);
 590
 591 int seq_putc(struct seq_file *m, char c)
 592 {
 593         if (m->count < m->size) {
 594                 m->buf[m->count++] = c;
 595                 return 0;
 596         }
 597         return -1;
 598 }
 599 EXPORT_SYMBOL(seq_putc);
 600
 601 int seq_puts(struct seq_file *m, const char *s)
 602 {
 603         int len = strlen(s);
 604         if (m->count + len < m->size) {
 605                 memcpy(m->buf + m->count, s, len);
 606                 m->count += len;
 607                 return 0;
 608         }
 609         m->count = m->size;
 610         return -1;
 611 }
 612 EXPORT_SYMBOL(seq_puts);
 613
 614 struct list_head *seq_list_start(struct list_head *head, loff_t pos)
 615 {
 616         struct list_head *lh;
 617
 618         list_for_each(lh, head)
 619                 if (pos-- == 0)
 620                         return lh;
 621
 622         return NULL;
 623 }
 624
 625 EXPORT_SYMBOL(seq_list_start);
 626
 627 struct list_head *seq_list_start_head(struct list_head *head, loff_t pos)
 628 {
 629         if (!pos)
 630                 return head;
 631
 632         return seq_list_start(head, pos - 1);
 633 }
 634
 635 EXPORT_SYMBOL(seq_list_start_head);
 636
 637 struct list_head *seq_list_next(void *v, struct list_head *head, loff_t *ppos)
 638 {
 639         struct list_head *lh;
 640
 641         lh = ((struct list_head *)v)->next;
 642         ++*ppos;
 643         return lh == head ? NULL : lh;
 644 }
 645
 646 EXPORT_SYMBOL(seq_list_next);