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