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         while (1) {
 112                 pos = m->index;
 113                 p = m->op->start(m, &pos);
 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 (m->count < m->size)
 123                         goto Fill;
 124                 m->op->stop(m, p);
 125                 kfree(m->buf);
 126                 m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
 127                 if (!m->buf)
 128                         goto Enomem;
 129                 m->count = 0;
 130                 m->version = 0;
 131         }
 132         m->op->stop(m, p);
 133         m->count = 0;
 134         goto Done;
 135 Fill:
 136         /* they want more? let's try to get some more */
 137         while (m->count < size) {
 138                 size_t offs = m->count;
 139                 loff_t next = pos;
 140                 p = m->op->next(m, p, &next);
 141                 if (!p || IS_ERR(p)) {
 142                         err = PTR_ERR(p);
 143                         break;
 144                 }
 145                 err = m->op->show(m, p);
 146                 if (m->count == m->size || err) {
 147                         m->count = offs;
 148                         if (likely(err <= 0))
 149                                 break;
 150                 }
 151                 pos = next;
 152         }
 153         m->op->stop(m, p);
 154         n = min(m->count, size);
 155         err = copy_to_user(buf, m->buf, n);
 156         if (err)
 157                 goto Efault;
 158         copied += n;
 159         m->count -= n;
 160         if (m->count)
 161                 m->from = n;
 162         else
 163                 pos++;
 164         m->index = pos;
 165 Done:
 166         if (!copied)
 167                 copied = err;
 168         else
 169                 *ppos += copied;
 170         file->f_version = m->version;
 171         mutex_unlock(&m->lock);
 172         return copied;
 173 Enomem:
 174         err = -ENOMEM;
 175         goto Done;
 176 Efault:
 177         err = -EFAULT;
 178         goto Done;
 179 }
 180 EXPORT_SYMBOL(seq_read);
 181
 182 static int traverse(struct seq_file *m, loff_t offset)
 183 {
 184         loff_t pos = 0, index;
 185         int error = 0;
 186         void *p;
 187
 188         m->version = 0;
 189         index = 0;
 190         m->count = m->from = 0;
 191         if (!offset) {
 192                 m->index = index;
 193                 return 0;
 194         }
 195         if (!m->buf) {
 196                 m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
 197                 if (!m->buf)
 198                         return -ENOMEM;
 199         }
 200         p = m->op->start(m, &index);
 201         while (p) {
 202                 error = PTR_ERR(p);
 203                 if (IS_ERR(p))
 204                         break;
 205                 error = m->op->show(m, p);
 206                 if (error < 0)
 207                         break;
 208                 if (unlikely(error)) {
 209                         error = 0;
 210                         m->count = 0;
 211                 }
 212                 if (m->count == m->size)
 213                         goto Eoverflow;
 214                 if (pos + m->count > offset) {
 215                         m->from = offset - pos;
 216                         m->count -= m->from;
 217                         m->index = index;
 218                         break;
 219                 }
 220                 pos += m->count;
 221                 m->count = 0;
 222                 if (pos == offset) {
 223                         index++;
 224                         m->index = index;
 225                         break;
 226                 }
 227                 p = m->op->next(m, p, &index);
 228         }
 229         m->op->stop(m, p);
 230         return error;
 231
 232 Eoverflow:
 233         m->op->stop(m, p);
 234         kfree(m->buf);
 235         m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
 236         return !m->buf ? -ENOMEM : -EAGAIN;
 237 }
 238
 239 /**
 240  *      seq_lseek -     ->llseek() method for sequential files.
 241  *      @file: the file in question
 242  *      @offset: new position
 243  *      @origin: 0 for absolute, 1 for relative position
 244  *
 245  *      Ready-made ->f_op->llseek()
 246  */
 247 loff_t seq_lseek(struct file *file, loff_t offset, int origin)
 248 {
 249         struct seq_file *m = (struct seq_file *)file->private_data;
 250         loff_t retval = -EINVAL;
 251
 252         mutex_lock(&m->lock);
 253         m->version = file->f_version;
 254         switch (origin) {
 255                 case 1:
 256                         offset += file->f_pos;
 257                 case 0:
 258                         if (offset < 0)
 259                                 break;
 260                         retval = offset;
 261                         if (offset != file->f_pos) {
 262                                 while ((retval=traverse(m, offset)) == -EAGAIN)
 263                                         ;
 264                                 if (retval) {
 265                                         /* with extreme prejudice... */
 266                                         file->f_pos = 0;
 267                                         m->version = 0;
 268                                         m->index = 0;
 269                                         m->count = 0;
 270                                 } else {
 271                                         retval = file->f_pos = offset;
 272                                 }
 273                         }
 274         }
 275         file->f_version = m->version;
 276         mutex_unlock(&m->lock);
 277         return retval;
 278 }
 279 EXPORT_SYMBOL(seq_lseek);
 280
 281 /**
 282  *      seq_release -   free the structures associated with sequential file.
 283  *      @file: file in question
 284  *      @inode: file->f_path.dentry->d_inode
 285  *
 286  *      Frees the structures associated with sequential file; can be used
 287  *      as ->f_op->release() if you don't have private data to destroy.
 288  */
 289 int seq_release(struct inode *inode, struct file *file)
 290 {
 291         struct seq_file *m = (struct seq_file *)file->private_data;
 292         kfree(m->buf);
 293         kfree(m);
 294         return 0;
 295 }
 296 EXPORT_SYMBOL(seq_release);
 297
 298 /**
 299  *      seq_escape -    print string into buffer, escaping some characters
 300  *      @m:     target buffer
 301  *      @s:     string
 302  *      @esc:   set of characters that need escaping
 303  *
 304  *      Puts string into buffer, replacing each occurrence of character from
 305  *      @esc with usual octal escape.  Returns 0 in case of success, -1 - in
 306  *      case of overflow.
 307  */
 308 int seq_escape(struct seq_file *m, const char *s, const char *esc)
 309 {
 310         char *end = m->buf + m->size;
 311         char *p;
 312         char c;
 313
 314         for (p = m->buf + m->count; (c = *s) != '\0' && p < end; s++) {
 315                 if (!strchr(esc, c)) {
 316                         *p++ = c;
 317                         continue;
 318                 }
 319                 if (p + 3 < end) {
 320                         *p++ = '\\';
 321                         *p++ = '0' + ((c & 0300) >> 6);
 322                         *p++ = '0' + ((c & 070) >> 3);
 323                         *p++ = '0' + (c & 07);
 324                         continue;
 325                 }
 326                 m->count = m->size;
 327                 return -1;
 328         }
 329         m->count = p - m->buf;
 330         return 0;
 331 }
 332 EXPORT_SYMBOL(seq_escape);
 333
 334 int seq_printf(struct seq_file *m, const char *f, ...)
 335 {
 336         va_list args;
 337         int len;
 338
 339         if (m->count < m->size) {
 340                 va_start(args, f);
 341                 len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
 342                 va_end(args);
 343                 if (m->count + len < m->size) {
 344                         m->count += len;
 345                         return 0;
 346                 }
 347         }
 348         m->count = m->size;
 349         return -1;
 350 }
 351 EXPORT_SYMBOL(seq_printf);
 352
 353 static char *mangle_path(char *s, char *p, char *esc)
 354 {
 355         while (s <= p) {
 356                 char c = *p++;
 357                 if (!c) {
 358                         return s;
 359                 } else if (!strchr(esc, c)) {
 360                         *s++ = c;
 361                 } else if (s + 4 > p) {
 362                         break;
 363                 } else {
 364                         *s++ = '\\';
 365                         *s++ = '0' + ((c & 0300) >> 6);
 366                         *s++ = '0' + ((c & 070) >> 3);
 367                         *s++ = '0' + (c & 07);
 368                 }
 369         }
 370         return NULL;
 371 }
 372
 373 /*
 374  * return the absolute path of 'dentry' residing in mount 'mnt'.
 375  */
 376 int seq_path(struct seq_file *m, struct path *path, char *esc)
 377 {
 378         if (m->count < m->size) {
 379                 char *s = m->buf + m->count;
 380                 char *p = d_path(path, s, m->size - m->count);
 381                 if (!IS_ERR(p)) {
 382                         s = mangle_path(s, p, esc);
 383                         if (s) {
 384                                 p = m->buf + m->count;
 385                                 m->count = s - m->buf;
 386                                 return s - p;
 387                         }
 388                 }
 389         }
 390         m->count = m->size;
 391         return -1;
 392 }
 393 EXPORT_SYMBOL(seq_path);
 394
 395 /*
 396  * Same as seq_path, but relative to supplied root.
 397  *
 398  * root may be changed, see __d_path().
 399  */
 400 int seq_path_root(struct seq_file *m, struct path *path, struct path *root,
 401                   char *esc)
 402 {
 403         int err = -ENAMETOOLONG;
 404         if (m->count < m->size) {
 405                 char *s = m->buf + m->count;
 406                 char *p;
 407
 408                 spin_lock(&dcache_lock);
 409                 p = __d_path(path, root, s, m->size - m->count);
 410                 spin_unlock(&dcache_lock);
 411                 err = PTR_ERR(p);
 412                 if (!IS_ERR(p)) {
 413                         s = mangle_path(s, p, esc);
 414                         if (s) {
 415                                 p = m->buf + m->count;
 416                                 m->count = s - m->buf;
 417                                 return 0;
 418                         }
 419                 }
 420         }
 421         m->count = m->size;
 422         return err;
 423 }
 424
 425 /*
 426  * returns the path of the 'dentry' from the root of its filesystem.
 427  */
 428 int seq_dentry(struct seq_file *m, struct dentry *dentry, char *esc)
 429 {
 430         if (m->count < m->size) {
 431                 char *s = m->buf + m->count;
 432                 char *p = dentry_path(dentry, s, m->size - m->count);
 433                 if (!IS_ERR(p)) {
 434                         s = mangle_path(s, p, esc);
 435                         if (s) {
 436                                 p = m->buf + m->count;
 437                                 m->count = s - m->buf;
 438                                 return s - p;
 439                         }
 440                 }
 441         }
 442         m->count = m->size;
 443         return -1;
 444 }
 445
 446 static void *single_start(struct seq_file *p, loff_t *pos)
 447 {
 448         return NULL + (*pos == 0);
 449 }
 450
 451 static void *single_next(struct seq_file *p, void *v, loff_t *pos)
 452 {
 453         ++*pos;
 454         return NULL;
 455 }
 456
 457 static void single_stop(struct seq_file *p, void *v)
 458 {
 459 }
 460
 461 int single_open(struct file *file, int (*show)(struct seq_file *, void *),
 462                 void *data)
 463 {
 464         struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL);
 465         int res = -ENOMEM;
 466
 467         if (op) {
 468                 op->start = single_start;
 469                 op->next = single_next;
 470                 op->stop = single_stop;
 471                 op->show = show;
 472                 res = seq_open(file, op);
 473                 if (!res)
 474                         ((struct seq_file *)file->private_data)->private = data;
 475                 else
 476                         kfree(op);
 477         }
 478         return res;
 479 }
 480 EXPORT_SYMBOL(single_open);
 481
 482 int single_release(struct inode *inode, struct file *file)
 483 {
 484         const struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
 485         int res = seq_release(inode, file);
 486         kfree(op);
 487         return res;
 488 }
 489 EXPORT_SYMBOL(single_release);
 490
 491 int seq_release_private(struct inode *inode, struct file *file)
 492 {
 493         struct seq_file *seq = file->private_data;
 494
 495         kfree(seq->private);
 496         seq->private = NULL;
 497         return seq_release(inode, file);
 498 }
 499 EXPORT_SYMBOL(seq_release_private);
 500
 501 void *__seq_open_private(struct file *f, const struct seq_operations *ops,
 502                 int psize)
 503 {
 504         int rc;
 505         void *private;
 506         struct seq_file *seq;
 507
 508         private = kzalloc(psize, GFP_KERNEL);
 509         if (private == NULL)
 510                 goto out;
 511
 512         rc = seq_open(f, ops);
 513         if (rc < 0)
 514                 goto out_free;
 515
 516         seq = f->private_data;
 517         seq->private = private;
 518         return private;
 519
 520 out_free:
 521         kfree(private);
 522 out:
 523         return NULL;
 524 }
 525 EXPORT_SYMBOL(__seq_open_private);
 526
 527 int seq_open_private(struct file *filp, const struct seq_operations *ops,
 528                 int psize)
 529 {
 530         return __seq_open_private(filp, ops, psize) ? 0 : -ENOMEM;
 531 }
 532 EXPORT_SYMBOL(seq_open_private);
 533
 534 int seq_putc(struct seq_file *m, char c)
 535 {
 536         if (m->count < m->size) {
 537                 m->buf[m->count++] = c;
 538                 return 0;
 539         }
 540         return -1;
 541 }
 542 EXPORT_SYMBOL(seq_putc);
 543
 544 int seq_puts(struct seq_file *m, const char *s)
 545 {
 546         int len = strlen(s);
 547         if (m->count + len < m->size) {
 548                 memcpy(m->buf + m->count, s, len);
 549                 m->count += len;
 550                 return 0;
 551         }
 552         m->count = m->size;
 553         return -1;
 554 }
 555 EXPORT_SYMBOL(seq_puts);
 556
 557 struct list_head *seq_list_start(struct list_head *head, loff_t pos)
 558 {
 559         struct list_head *lh;
 560
 561         list_for_each(lh, head)
 562                 if (pos-- == 0)
 563                         return lh;
 564
 565         return NULL;
 566 }
 567
 568 EXPORT_SYMBOL(seq_list_start);
 569
 570 struct list_head *seq_list_start_head(struct list_head *head, loff_t pos)
 571 {
 572         if (!pos)
 573                 return head;
 574
 575         return seq_list_start(head, pos - 1);
 576 }
 577
 578 EXPORT_SYMBOL(seq_list_start_head);
 579
 580 struct list_head *seq_list_next(void *v, struct list_head *head, loff_t *ppos)
 581 {
 582         struct list_head *lh;
 583
 584         lh = ((struct list_head *)v)->next;
 585         ++*ppos;
 586         return lh == head ? NULL : lh;
 587 }
 588
 589 EXPORT_SYMBOL(seq_list_next);