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 = kmalloc(sizeof(*p), GFP_KERNEL);
  32         if (!p)
  33                 return -ENOMEM;
  34         memset(p, 0, sizeof(*p));
  35         sema_init(&p->sem, 1);
  36         p->op = op;
  37         file->private_data = p;
  38
  39         /*
  40          * Wrappers around seq_open(e.g. swaps_open) need to be
  41          * aware of this. If they set f_version themselves, they
  42          * should call seq_open first and then set f_version.
  43          */
  44         file->f_version = 0;
  45
  46         /* SEQ files support lseek, but not pread/pwrite */
  47         file->f_mode &= ~(FMODE_PREAD | FMODE_PWRITE);
  48         return 0;
  49 }
  50 EXPORT_SYMBOL(seq_open);
  51
  52 /**
  53  *      seq_read -      ->read() method for sequential files.
  54  *      @file: the file to read from
  55  *      @buf: the buffer to read to
  56  *      @size: the maximum number of bytes to read
  57  *      @ppos: the current position in the file
  58  *
  59  *      Ready-made ->f_op->read()
  60  */
  61 ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
  62 {
  63         struct seq_file *m = (struct seq_file *)file->private_data;
  64         size_t copied = 0;
  65         loff_t pos;
  66         size_t n;
  67         void *p;
  68         int err = 0;
  69
  70         down(&m->sem);
  71         /*
  72          * seq_file->op->..m_start/m_stop/m_next may do special actions
  73          * or optimisations based on the file->f_version, so we want to
  74          * pass the file->f_version to those methods.
  75          *
  76          * seq_file->version is just copy of f_version, and seq_file
  77          * methods can treat it simply as file version.
  78          * It is copied in first and copied out after all operations.
  79          * It is convenient to have it as  part of structure to avoid the
  80          * need of passing another argument to all the seq_file methods.
  81          */
  82         m->version = file->f_version;
  83         /* grab buffer if we didn't have one */
  84         if (!m->buf) {
  85                 m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
  86                 if (!m->buf)
  87                         goto Enomem;
  88         }
  89         /* if not empty - flush it first */
  90         if (m->count) {
  91                 n = min(m->count, size);
  92                 err = copy_to_user(buf, m->buf + m->from, n);
  93                 if (err)
  94                         goto Efault;
  95                 m->count -= n;
  96                 m->from += n;
  97                 size -= n;
  98                 buf += n;
  99                 copied += n;
 100                 if (!m->count)
 101                         m->index++;
 102                 if (!size)
 103                         goto Done;
 104         }
 105         /* we need at least one record in buffer */
 106         while (1) {
 107                 pos = m->index;
 108                 p = m->op->start(m, &pos);
 109                 err = PTR_ERR(p);
 110                 if (!p || IS_ERR(p))
 111                         break;
 112                 err = m->op->show(m, p);
 113                 if (err)
 114                         break;
 115                 if (m->count < m->size)
 116                         goto Fill;
 117                 m->op->stop(m, p);
 118                 kfree(m->buf);
 119                 m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
 120                 if (!m->buf)
 121                         goto Enomem;
 122                 m->count = 0;
 123                 m->version = 0;
 124         }
 125         m->op->stop(m, p);
 126         m->count = 0;
 127         goto Done;
 128 Fill:
 129         /* they want more? let's try to get some more */
 130         while (m->count < size) {
 131                 size_t offs = m->count;
 132                 loff_t next = pos;
 133                 p = m->op->next(m, p, &next);
 134                 if (!p || IS_ERR(p)) {
 135                         err = PTR_ERR(p);
 136                         break;
 137                 }
 138                 err = m->op->show(m, p);
 139                 if (err || m->count == m->size) {
 140                         m->count = offs;
 141                         break;
 142                 }
 143                 pos = next;
 144         }
 145         m->op->stop(m, p);
 146         n = min(m->count, size);
 147         err = copy_to_user(buf, m->buf, n);
 148         if (err)
 149                 goto Efault;
 150         copied += n;
 151         m->count -= n;
 152         if (m->count)
 153                 m->from = n;
 154         else
 155                 pos++;
 156         m->index = pos;
 157 Done:
 158         if (!copied)
 159                 copied = err;
 160         else
 161                 *ppos += copied;
 162         file->f_version = m->version;
 163         up(&m->sem);
 164         return copied;
 165 Enomem:
 166         err = -ENOMEM;
 167         goto Done;
 168 Efault:
 169         err = -EFAULT;
 170         goto Done;
 171 }
 172 EXPORT_SYMBOL(seq_read);
 173
 174 static int traverse(struct seq_file *m, loff_t offset)
 175 {
 176         loff_t pos = 0;
 177         int error = 0;
 178         void *p;
 179
 180         m->version = 0;
 181         m->index = 0;
 182         m->count = m->from = 0;
 183         if (!offset)
 184                 return 0;
 185         if (!m->buf) {
 186                 m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
 187                 if (!m->buf)
 188                         return -ENOMEM;
 189         }
 190         p = m->op->start(m, &m->index);
 191         while (p) {
 192                 error = PTR_ERR(p);
 193                 if (IS_ERR(p))
 194                         break;
 195                 error = m->op->show(m, p);
 196                 if (error)
 197                         break;
 198                 if (m->count == m->size)
 199                         goto Eoverflow;
 200                 if (pos + m->count > offset) {
 201                         m->from = offset - pos;
 202                         m->count -= m->from;
 203                         break;
 204                 }
 205                 pos += m->count;
 206                 m->count = 0;
 207                 if (pos == offset) {
 208                         m->index++;
 209                         break;
 210                 }
 211                 p = m->op->next(m, p, &m->index);
 212         }
 213         m->op->stop(m, p);
 214         return error;
 215
 216 Eoverflow:
 217         m->op->stop(m, p);
 218         kfree(m->buf);
 219         m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
 220         return !m->buf ? -ENOMEM : -EAGAIN;
 221 }
 222
 223 /**
 224  *      seq_lseek -     ->llseek() method for sequential files.
 225  *      @file: the file in question
 226  *      @offset: new position
 227  *      @origin: 0 for absolute, 1 for relative position
 228  *
 229  *      Ready-made ->f_op->llseek()
 230  */
 231 loff_t seq_lseek(struct file *file, loff_t offset, int origin)
 232 {
 233         struct seq_file *m = (struct seq_file *)file->private_data;
 234         long long retval = -EINVAL;
 235
 236         down(&m->sem);
 237         m->version = file->f_version;
 238         switch (origin) {
 239                 case 1:
 240                         offset += file->f_pos;
 241                 case 0:
 242                         if (offset < 0)
 243                                 break;
 244                         retval = offset;
 245                         if (offset != file->f_pos) {
 246                                 while ((retval=traverse(m, offset)) == -EAGAIN)
 247                                         ;
 248                                 if (retval) {
 249                                         /* with extreme prejudice... */
 250                                         file->f_pos = 0;
 251                                         m->version = 0;
 252                                         m->index = 0;
 253                                         m->count = 0;
 254                                 } else {
 255                                         retval = file->f_pos = offset;
 256                                 }
 257                         }
 258         }
 259         up(&m->sem);
 260         file->f_version = m->version;
 261         return retval;
 262 }
 263 EXPORT_SYMBOL(seq_lseek);
 264
 265 /**
 266  *      seq_release -   free the structures associated with sequential file.
 267  *      @file: file in question
 268  *      @inode: file->f_dentry->d_inode
 269  *
 270  *      Frees the structures associated with sequential file; can be used
 271  *      as ->f_op->release() if you don't have private data to destroy.
 272  */
 273 int seq_release(struct inode *inode, struct file *file)
 274 {
 275         struct seq_file *m = (struct seq_file *)file->private_data;
 276         kfree(m->buf);
 277         kfree(m);
 278         return 0;
 279 }
 280 EXPORT_SYMBOL(seq_release);
 281
 282 /**
 283  *      seq_escape -    print string into buffer, escaping some characters
 284  *      @m:     target buffer
 285  *      @s:     string
 286  *      @esc:   set of characters that need escaping
 287  *
 288  *      Puts string into buffer, replacing each occurrence of character from
 289  *      @esc with usual octal escape.  Returns 0 in case of success, -1 - in
 290  *      case of overflow.
 291  */
 292 int seq_escape(struct seq_file *m, const char *s, const char *esc)
 293 {
 294         char *end = m->buf + m->size;
 295         char *p;
 296         char c;
 297
 298         for (p = m->buf + m->count; (c = *s) != '\0' && p < end; s++) {
 299                 if (!strchr(esc, c)) {
 300                         *p++ = c;
 301                         continue;
 302                 }
 303                 if (p + 3 < end) {
 304                         *p++ = '\\';
 305                         *p++ = '0' + ((c & 0300) >> 6);
 306                         *p++ = '0' + ((c & 070) >> 3);
 307                         *p++ = '0' + (c & 07);
 308                         continue;
 309                 }
 310                 m->count = m->size;
 311                 return -1;
 312         }
 313         m->count = p - m->buf;
 314         return 0;
 315 }
 316 EXPORT_SYMBOL(seq_escape);
 317
 318 int seq_printf(struct seq_file *m, const char *f, ...)
 319 {
 320         va_list args;
 321         int len;
 322
 323         if (m->count < m->size) {
 324                 va_start(args, f);
 325                 len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
 326                 va_end(args);
 327                 if (m->count + len < m->size) {
 328                         m->count += len;
 329                         return 0;
 330                 }
 331         }
 332         m->count = m->size;
 333         return -1;
 334 }
 335 EXPORT_SYMBOL(seq_printf);
 336
 337 int seq_path(struct seq_file *m,
 338              struct vfsmount *mnt, struct dentry *dentry,
 339              char *esc)
 340 {
 341         if (m->count < m->size) {
 342                 char *s = m->buf + m->count;
 343                 char *p = d_path(dentry, mnt, s, m->size - m->count);
 344                 if (!IS_ERR(p)) {
 345                         while (s <= p) {
 346                                 char c = *p++;
 347                                 if (!c) {
 348                                         p = m->buf + m->count;
 349                                         m->count = s - m->buf;
 350                                         return s - p;
 351                                 } else if (!strchr(esc, c)) {
 352                                         *s++ = c;
 353                                 } else if (s + 4 > p) {
 354                                         break;
 355                                 } else {
 356                                         *s++ = '\\';
 357                                         *s++ = '0' + ((c & 0300) >> 6);
 358                                         *s++ = '0' + ((c & 070) >> 3);
 359                                         *s++ = '0' + (c & 07);
 360                                 }
 361                         }
 362                 }
 363         }
 364         m->count = m->size;
 365         return -1;
 366 }
 367 EXPORT_SYMBOL(seq_path);
 368
 369 static void *single_start(struct seq_file *p, loff_t *pos)
 370 {
 371         return NULL + (*pos == 0);
 372 }
 373
 374 static void *single_next(struct seq_file *p, void *v, loff_t *pos)
 375 {
 376         ++*pos;
 377         return NULL;
 378 }
 379
 380 static void single_stop(struct seq_file *p, void *v)
 381 {
 382 }
 383
 384 int single_open(struct file *file, int (*show)(struct seq_file *, void *),
 385                 void *data)
 386 {
 387         struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL);
 388         int res = -ENOMEM;
 389
 390         if (op) {
 391                 op->start = single_start;
 392                 op->next = single_next;
 393                 op->stop = single_stop;
 394                 op->show = show;
 395                 res = seq_open(file, op);
 396                 if (!res)
 397                         ((struct seq_file *)file->private_data)->private = data;
 398                 else
 399                         kfree(op);
 400         }
 401         return res;
 402 }
 403 EXPORT_SYMBOL(single_open);
 404
 405 int single_release(struct inode *inode, struct file *file)
 406 {
 407         struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
 408         int res = seq_release(inode, file);
 409         kfree(op);
 410         return res;
 411 }
 412 EXPORT_SYMBOL(single_release);
 413
 414 int seq_release_private(struct inode *inode, struct file *file)
 415 {
 416         struct seq_file *seq = file->private_data;
 417
 418         kfree(seq->private);
 419         seq->private = NULL;
 420         return seq_release(inode, file);
 421 }
 422 EXPORT_SYMBOL(seq_release_private);
 423
 424 int seq_putc(struct seq_file *m, char c)
 425 {
 426         if (m->count < m->size) {
 427                 m->buf[m->count++] = c;
 428                 return 0;
 429         }
 430         return -1;
 431 }
 432 EXPORT_SYMBOL(seq_putc);
 433
 434 int seq_puts(struct seq_file *m, const char *s)
 435 {
 436         int len = strlen(s);
 437         if (m->count + len < m->size) {
 438                 memcpy(m->buf + m->count, s, len);
 439                 m->count += len;
 440                 return 0;
 441         }
 442         m->count = m->size;
 443         return -1;
 444 }
 445 EXPORT_SYMBOL(seq_puts);