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  */
  29 int seq_open(struct file *file, const struct seq_operations *op)
  30 {
  31         struct seq_file *p = file->private_data;
  32
  33         if (!p) {
  34                 p = kmalloc(sizeof(*p), GFP_KERNEL);
  35                 if (!p)
  36                         return -ENOMEM;
  37                 file->private_data = p;
  38         }
  39         memset(p, 0, sizeof(*p));
  40         mutex_init(&p->lock);
  41         p->op = op;
  42
  43         /*
  44          * Wrappers around seq_open(e.g. swaps_open) need to be
  45          * aware of this. If they set f_version themselves, they
  46          * should call seq_open first and then set f_version.
  47          */
  48         file->f_version = 0;
  49
  50         /* SEQ files support lseek, but not pread/pwrite */
  51         file->f_mode &= ~(FMODE_PREAD | FMODE_PWRITE);
  52         return 0;
  53 }
  54 EXPORT_SYMBOL(seq_open);
  55
  56 /**
  57  *      seq_read -      ->read() method for sequential files.
  58  *      @file: the file to read from
  59  *      @buf: the buffer to read to
  60  *      @size: the maximum number of bytes to read
  61  *      @ppos: the current position in the file
  62  *
  63  *      Ready-made ->f_op->read()
  64  */
  65 ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
  66 {
  67         struct seq_file *m = (struct seq_file *)file->private_data;
  68         size_t copied = 0;
  69         loff_t pos;
  70         size_t n;
  71         void *p;
  72         int err = 0;
  73
  74         mutex_lock(&m->lock);
  75         /*
  76          * seq_file->op->..m_start/m_stop/m_next may do special actions
  77          * or optimisations based on the file->f_version, so we want to
  78          * pass the file->f_version to those methods.
  79          *
  80          * seq_file->version is just copy of f_version, and seq_file
  81          * methods can treat it simply as file version.
  82          * It is copied in first and copied out after all operations.
  83          * It is convenient to have it as  part of structure to avoid the
  84          * need of passing another argument to all the seq_file methods.
  85          */
  86         m->version = file->f_version;
  87         /* grab buffer if we didn't have one */
  88         if (!m->buf) {
  89                 m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
  90                 if (!m->buf)
  91                         goto Enomem;
  92         }
  93         /* if not empty - flush it first */
  94         if (m->count) {
  95                 n = min(m->count, size);
  96                 err = copy_to_user(buf, m->buf + m->from, n);
  97                 if (err)
  98                         goto Efault;
  99                 m->count -= n;
 100                 m->from += n;
 101                 size -= n;
 102                 buf += n;
 103                 copied += n;
 104                 if (!m->count)
 105                         m->index++;
 106                 if (!size)
 107                         goto Done;
 108         }
 109         /* we need at least one record in buffer */
 110         while (1) {
 111                 pos = m->index;
 112                 p = m->op->start(m, &pos);
 113                 err = PTR_ERR(p);
 114                 if (!p || IS_ERR(p))
 115                         break;
 116                 err = m->op->show(m, p);
 117                 if (err)
 118                         break;
 119                 if (m->count < m->size)
 120                         goto Fill;
 121                 m->op->stop(m, p);
 122                 kfree(m->buf);
 123                 m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
 124                 if (!m->buf)
 125                         goto Enomem;
 126                 m->count = 0;
 127                 m->version = 0;
 128         }
 129         m->op->stop(m, p);
 130         m->count = 0;
 131         goto Done;
 132 Fill:
 133         /* they want more? let's try to get some more */
 134         while (m->count < size) {
 135                 size_t offs = m->count;
 136                 loff_t next = pos;
 137                 p = m->op->next(m, p, &next);
 138                 if (!p || IS_ERR(p)) {
 139                         err = PTR_ERR(p);
 140                         break;
 141                 }
 142                 err = m->op->show(m, p);
 143                 if (err || m->count == m->size) {
 144                         m->count = offs;
 145                         break;
 146                 }
 147                 pos = next;
 148         }
 149         m->op->stop(m, p);
 150         n = min(m->count, size);
 151         err = copy_to_user(buf, m->buf, n);
 152         if (err)
 153                 goto Efault;
 154         copied += n;
 155         m->count -= n;
 156         if (m->count)
 157                 m->from = n;
 158         else
 159                 pos++;
 160         m->index = pos;
 161 Done:
 162         if (!copied)
 163                 copied = err;
 164         else
 165                 *ppos += copied;
 166         file->f_version = m->version;
 167         mutex_unlock(&m->lock);
 168         return copied;
 169 Enomem:
 170         err = -ENOMEM;
 171         goto Done;
 172 Efault:
 173         err = -EFAULT;
 174         goto Done;
 175 }
 176 EXPORT_SYMBOL(seq_read);
 177
 178 static int traverse(struct seq_file *m, loff_t offset)
 179 {
 180         loff_t pos = 0, index;
 181         int error = 0;
 182         void *p;
 183
 184         m->version = 0;
 185         index = 0;
 186         m->count = m->from = 0;
 187         if (!offset) {
 188                 m->index = index;
 189                 return 0;
 190         }
 191         if (!m->buf) {
 192                 m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
 193                 if (!m->buf)
 194                         return -ENOMEM;
 195         }
 196         p = m->op->start(m, &index);
 197         while (p) {
 198                 error = PTR_ERR(p);
 199                 if (IS_ERR(p))
 200                         break;
 201                 error = m->op->show(m, p);
 202                 if (error)
 203                         break;
 204                 if (m->count == m->size)
 205                         goto Eoverflow;
 206                 if (pos + m->count > offset) {
 207                         m->from = offset - pos;
 208                         m->count -= m->from;
 209                         m->index = index;
 210                         break;
 211                 }
 212                 pos += m->count;
 213                 m->count = 0;
 214                 if (pos == offset) {
 215                         index++;
 216                         m->index = index;
 217                         break;
 218                 }
 219                 p = m->op->next(m, p, &index);
 220         }
 221         m->op->stop(m, p);
 222         return error;
 223
 224 Eoverflow:
 225         m->op->stop(m, p);
 226         kfree(m->buf);
 227         m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
 228         return !m->buf ? -ENOMEM : -EAGAIN;
 229 }
 230
 231 /**
 232  *      seq_lseek -     ->llseek() method for sequential files.
 233  *      @file: the file in question
 234  *      @offset: new position
 235  *      @origin: 0 for absolute, 1 for relative position
 236  *
 237  *      Ready-made ->f_op->llseek()
 238  */
 239 loff_t seq_lseek(struct file *file, loff_t offset, int origin)
 240 {
 241         struct seq_file *m = (struct seq_file *)file->private_data;
 242         long long retval = -EINVAL;
 243
 244         mutex_lock(&m->lock);
 245         m->version = file->f_version;
 246         switch (origin) {
 247                 case 1:
 248                         offset += file->f_pos;
 249                 case 0:
 250                         if (offset < 0)
 251                                 break;
 252                         retval = offset;
 253                         if (offset != file->f_pos) {
 254                                 while ((retval=traverse(m, offset)) == -EAGAIN)
 255                                         ;
 256                                 if (retval) {
 257                                         /* with extreme prejudice... */
 258                                         file->f_pos = 0;
 259                                         m->version = 0;
 260                                         m->index = 0;
 261                                         m->count = 0;
 262                                 } else {
 263                                         retval = file->f_pos = offset;
 264                                 }
 265                         }
 266         }
 267         file->f_version = m->version;
 268         mutex_unlock(&m->lock);
 269         return retval;
 270 }
 271 EXPORT_SYMBOL(seq_lseek);
 272
 273 /**
 274  *      seq_release -   free the structures associated with sequential file.
 275  *      @file: file in question
 276  *      @inode: file->f_path.dentry->d_inode
 277  *
 278  *      Frees the structures associated with sequential file; can be used
 279  *      as ->f_op->release() if you don't have private data to destroy.
 280  */
 281 int seq_release(struct inode *inode, struct file *file)
 282 {
 283         struct seq_file *m = (struct seq_file *)file->private_data;
 284         kfree(m->buf);
 285         kfree(m);
 286         return 0;
 287 }
 288 EXPORT_SYMBOL(seq_release);
 289
 290 /**
 291  *      seq_escape -    print string into buffer, escaping some characters
 292  *      @m:     target buffer
 293  *      @s:     string
 294  *      @esc:   set of characters that need escaping
 295  *
 296  *      Puts string into buffer, replacing each occurrence of character from
 297  *      @esc with usual octal escape.  Returns 0 in case of success, -1 - in
 298  *      case of overflow.
 299  */
 300 int seq_escape(struct seq_file *m, const char *s, const char *esc)
 301 {
 302         char *end = m->buf + m->size;
 303         char *p;
 304         char c;
 305
 306         for (p = m->buf + m->count; (c = *s) != '\0' && p < end; s++) {
 307                 if (!strchr(esc, c)) {
 308                         *p++ = c;
 309                         continue;
 310                 }
 311                 if (p + 3 < end) {
 312                         *p++ = '\\';
 313                         *p++ = '0' + ((c & 0300) >> 6);
 314                         *p++ = '0' + ((c & 070) >> 3);
 315                         *p++ = '0' + (c & 07);
 316                         continue;
 317                 }
 318                 m->count = m->size;
 319                 return -1;
 320         }
 321         m->count = p - m->buf;
 322         return 0;
 323 }
 324 EXPORT_SYMBOL(seq_escape);
 325
 326 int seq_printf(struct seq_file *m, const char *f, ...)
 327 {
 328         va_list args;
 329         int len;
 330
 331         if (m->count < m->size) {
 332                 va_start(args, f);
 333                 len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
 334                 va_end(args);
 335                 if (m->count + len < m->size) {
 336                         m->count += len;
 337                         return 0;
 338                 }
 339         }
 340         m->count = m->size;
 341         return -1;
 342 }
 343 EXPORT_SYMBOL(seq_printf);
 344
 345 int seq_path(struct seq_file *m,
 346              struct vfsmount *mnt, struct dentry *dentry,
 347              char *esc)
 348 {
 349         if (m->count < m->size) {
 350                 char *s = m->buf + m->count;
 351                 char *p = d_path(dentry, mnt, s, m->size - m->count);
 352                 if (!IS_ERR(p)) {
 353                         while (s <= p) {
 354                                 char c = *p++;
 355                                 if (!c) {
 356                                         p = m->buf + m->count;
 357                                         m->count = s - m->buf;
 358                                         return s - p;
 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                 }
 371         }
 372         m->count = m->size;
 373         return -1;
 374 }
 375 EXPORT_SYMBOL(seq_path);
 376
 377 static void *single_start(struct seq_file *p, loff_t *pos)
 378 {
 379         return NULL + (*pos == 0);
 380 }
 381
 382 static void *single_next(struct seq_file *p, void *v, loff_t *pos)
 383 {
 384         ++*pos;
 385         return NULL;
 386 }
 387
 388 static void single_stop(struct seq_file *p, void *v)
 389 {
 390 }
 391
 392 int single_open(struct file *file, int (*show)(struct seq_file *, void *),
 393                 void *data)
 394 {
 395         struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL);
 396         int res = -ENOMEM;
 397
 398         if (op) {
 399                 op->start = single_start;
 400                 op->next = single_next;
 401                 op->stop = single_stop;
 402                 op->show = show;
 403                 res = seq_open(file, op);
 404                 if (!res)
 405                         ((struct seq_file *)file->private_data)->private = data;
 406                 else
 407                         kfree(op);
 408         }
 409         return res;
 410 }
 411 EXPORT_SYMBOL(single_open);
 412
 413 int single_release(struct inode *inode, struct file *file)
 414 {
 415         const struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
 416         int res = seq_release(inode, file);
 417         kfree(op);
 418         return res;
 419 }
 420 EXPORT_SYMBOL(single_release);
 421
 422 int seq_release_private(struct inode *inode, struct file *file)
 423 {
 424         struct seq_file *seq = file->private_data;
 425
 426         kfree(seq->private);
 427         seq->private = NULL;
 428         return seq_release(inode, file);
 429 }
 430 EXPORT_SYMBOL(seq_release_private);
 431
 432 int seq_putc(struct seq_file *m, char c)
 433 {
 434         if (m->count < m->size) {
 435                 m->buf[m->count++] = c;
 436                 return 0;
 437         }
 438         return -1;
 439 }
 440 EXPORT_SYMBOL(seq_putc);
 441
 442 int seq_puts(struct seq_file *m, const char *s)
 443 {
 444         int len = strlen(s);
 445         if (m->count + len < m->size) {
 446                 memcpy(m->buf + m->count, s, len);
 447                 m->count += len;
 448                 return 0;
 449         }
 450         m->count = m->size;
 451         return -1;
 452 }
 453 EXPORT_SYMBOL(seq_puts);
 454
 455 struct list_head *seq_list_start(struct list_head *head, loff_t pos)
 456 {
 457         struct list_head *lh;
 458
 459         list_for_each(lh, head)
 460                 if (pos-- == 0)
 461                         return lh;
 462
 463         return NULL;
 464 }
 465
 466 EXPORT_SYMBOL(seq_list_start);
 467
 468 struct list_head *seq_list_start_head(struct list_head *head, loff_t pos)
 469 {
 470         if (!pos)
 471                 return head;
 472
 473         return seq_list_start(head, pos - 1);
 474 }
 475
 476 EXPORT_SYMBOL(seq_list_start_head);
 477
 478 struct list_head *seq_list_next(void *v, struct list_head *head, loff_t *ppos)
 479 {
 480         struct list_head *lh;
 481
 482         lh = ((struct list_head *)v)->next;
 483         ++*ppos;
 484         return lh == head ? NULL : lh;
 485 }
 486
 487 EXPORT_SYMBOL(seq_list_next);