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