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, 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         sema_init(&p->sem, 1);
  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         down(&m->sem);
  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         up(&m->sem);
 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;
 181         int error = 0;
 182         void *p;
 183
 184         m->version = 0;
 185         m->index = 0;
 186         m->count = m->from = 0;
 187         if (!offset)
 188                 return 0;
 189         if (!m->buf) {
 190                 m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
 191                 if (!m->buf)
 192                         return -ENOMEM;
 193         }
 194         p = m->op->start(m, &m->index);
 195         while (p) {
 196                 error = PTR_ERR(p);
 197                 if (IS_ERR(p))
 198                         break;
 199                 error = m->op->show(m, p);
 200                 if (error)
 201                         break;
 202                 if (m->count == m->size)
 203                         goto Eoverflow;
 204                 if (pos + m->count > offset) {
 205                         m->from = offset - pos;
 206                         m->count -= m->from;
 207                         break;
 208                 }
 209                 pos += m->count;
 210                 m->count = 0;
 211                 if (pos == offset) {
 212                         m->index++;
 213                         break;
 214                 }
 215                 p = m->op->next(m, p, &m->index);
 216         }
 217         m->op->stop(m, p);
 218         return error;
 219
 220 Eoverflow:
 221         m->op->stop(m, p);
 222         kfree(m->buf);
 223         m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
 224         return !m->buf ? -ENOMEM : -EAGAIN;
 225 }
 226
 227 /**
 228  *      seq_lseek -     ->llseek() method for sequential files.
 229  *      @file: the file in question
 230  *      @offset: new position
 231  *      @origin: 0 for absolute, 1 for relative position
 232  *
 233  *      Ready-made ->f_op->llseek()
 234  */
 235 loff_t seq_lseek(struct file *file, loff_t offset, int origin)
 236 {
 237         struct seq_file *m = (struct seq_file *)file->private_data;
 238         long long retval = -EINVAL;
 239
 240         down(&m->sem);
 241         m->version = file->f_version;
 242         switch (origin) {
 243                 case 1:
 244                         offset += file->f_pos;
 245                 case 0:
 246                         if (offset < 0)
 247                                 break;
 248                         retval = offset;
 249                         if (offset != file->f_pos) {
 250                                 while ((retval=traverse(m, offset)) == -EAGAIN)
 251                                         ;
 252                                 if (retval) {
 253                                         /* with extreme prejudice... */
 254                                         file->f_pos = 0;
 255                                         m->version = 0;
 256                                         m->index = 0;
 257                                         m->count = 0;
 258                                 } else {
 259                                         retval = file->f_pos = offset;
 260                                 }
 261                         }
 262         }
 263         up(&m->sem);
 264         file->f_version = m->version;
 265         return retval;
 266 }
 267 EXPORT_SYMBOL(seq_lseek);
 268
 269 /**
 270  *      seq_release -   free the structures associated with sequential file.
 271  *      @file: file in question
 272  *      @inode: file->f_dentry->d_inode
 273  *
 274  *      Frees the structures associated with sequential file; can be used
 275  *      as ->f_op->release() if you don't have private data to destroy.
 276  */
 277 int seq_release(struct inode *inode, struct file *file)
 278 {
 279         struct seq_file *m = (struct seq_file *)file->private_data;
 280         kfree(m->buf);
 281         kfree(m);
 282         return 0;
 283 }
 284 EXPORT_SYMBOL(seq_release);
 285
 286 /**
 287  *      seq_escape -    print string into buffer, escaping some characters
 288  *      @m:     target buffer
 289  *      @s:     string
 290  *      @esc:   set of characters that need escaping
 291  *
 292  *      Puts string into buffer, replacing each occurrence of character from
 293  *      @esc with usual octal escape.  Returns 0 in case of success, -1 - in
 294  *      case of overflow.
 295  */
 296 int seq_escape(struct seq_file *m, const char *s, const char *esc)
 297 {
 298         char *end = m->buf + m->size;
 299         char *p;
 300         char c;
 301
 302         for (p = m->buf + m->count; (c = *s) != '\0' && p < end; s++) {
 303                 if (!strchr(esc, c)) {
 304                         *p++ = c;
 305                         continue;
 306                 }
 307                 if (p + 3 < end) {
 308                         *p++ = '\\';
 309                         *p++ = '0' + ((c & 0300) >> 6);
 310                         *p++ = '0' + ((c & 070) >> 3);
 311                         *p++ = '0' + (c & 07);
 312                         continue;
 313                 }
 314                 m->count = m->size;
 315                 return -1;
 316         }
 317         m->count = p - m->buf;
 318         return 0;
 319 }
 320 EXPORT_SYMBOL(seq_escape);
 321
 322 int seq_printf(struct seq_file *m, const char *f, ...)
 323 {
 324         va_list args;
 325         int len;
 326
 327         if (m->count < m->size) {
 328                 va_start(args, f);
 329                 len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
 330                 va_end(args);
 331                 if (m->count + len < m->size) {
 332                         m->count += len;
 333                         return 0;
 334                 }
 335         }
 336         m->count = m->size;
 337         return -1;
 338 }
 339 EXPORT_SYMBOL(seq_printf);
 340
 341 int seq_path(struct seq_file *m,
 342              struct vfsmount *mnt, struct dentry *dentry,
 343              char *esc)
 344 {
 345         if (m->count < m->size) {
 346                 char *s = m->buf + m->count;
 347                 char *p = d_path(dentry, mnt, s, m->size - m->count);
 348                 if (!IS_ERR(p)) {
 349                         while (s <= p) {
 350                                 char c = *p++;
 351                                 if (!c) {
 352                                         p = m->buf + m->count;
 353                                         m->count = s - m->buf;
 354                                         return s - p;
 355                                 } else if (!strchr(esc, c)) {
 356                                         *s++ = c;
 357                                 } else if (s + 4 > p) {
 358                                         break;
 359                                 } else {
 360                                         *s++ = '\\';
 361                                         *s++ = '0' + ((c & 0300) >> 6);
 362                                         *s++ = '0' + ((c & 070) >> 3);
 363                                         *s++ = '0' + (c & 07);
 364                                 }
 365                         }
 366                 }
 367         }
 368         m->count = m->size;
 369         return -1;
 370 }
 371 EXPORT_SYMBOL(seq_path);
 372
 373 static void *single_start(struct seq_file *p, loff_t *pos)
 374 {
 375         return NULL + (*pos == 0);
 376 }
 377
 378 static void *single_next(struct seq_file *p, void *v, loff_t *pos)
 379 {
 380         ++*pos;
 381         return NULL;
 382 }
 383
 384 static void single_stop(struct seq_file *p, void *v)
 385 {
 386 }
 387
 388 int single_open(struct file *file, int (*show)(struct seq_file *, void *),
 389                 void *data)
 390 {
 391         struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL);
 392         int res = -ENOMEM;
 393
 394         if (op) {
 395                 op->start = single_start;
 396                 op->next = single_next;
 397                 op->stop = single_stop;
 398                 op->show = show;
 399                 res = seq_open(file, op);
 400                 if (!res)
 401                         ((struct seq_file *)file->private_data)->private = data;
 402                 else
 403                         kfree(op);
 404         }
 405         return res;
 406 }
 407 EXPORT_SYMBOL(single_open);
 408
 409 int single_release(struct inode *inode, struct file *file)
 410 {
 411         struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
 412         int res = seq_release(inode, file);
 413         kfree(op);
 414         return res;
 415 }
 416 EXPORT_SYMBOL(single_release);
 417
 418 int seq_release_private(struct inode *inode, struct file *file)
 419 {
 420         struct seq_file *seq = file->private_data;
 421
 422         kfree(seq->private);
 423         seq->private = NULL;
 424         return seq_release(inode, file);
 425 }
 426 EXPORT_SYMBOL(seq_release_private);
 427
 428 int seq_putc(struct seq_file *m, char c)
 429 {
 430         if (m->count < m->size) {
 431                 m->buf[m->count++] = c;
 432                 return 0;
 433         }
 434         return -1;
 435 }
 436 EXPORT_SYMBOL(seq_putc);
 437
 438 int seq_puts(struct seq_file *m, const char *s)
 439 {
 440         int len = strlen(s);
 441         if (m->count + len < m->size) {
 442                 memcpy(m->buf + m->count, s, len);
 443                 m->count += len;
 444                 return 0;
 445         }
 446         m->count = m->size;
 447         return -1;
 448 }
 449 EXPORT_SYMBOL(seq_puts);