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         /* SEQ files support lseek, but not pread/pwrite */
  41         file->f_mode &= ~(FMODE_PREAD | FMODE_PWRITE);
  42         return 0;
  43 }
  44 EXPORT_SYMBOL(seq_open);
  45
  46 /**
  47  *      seq_read -      ->read() method for sequential files.
  48  *      @file, @buf, @size, @ppos: see file_operations method
  49  *
  50  *      Ready-made ->f_op->read()
  51  */
  52 ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
  53 {
  54         struct seq_file *m = (struct seq_file *)file->private_data;
  55         size_t copied = 0;
  56         loff_t pos;
  57         size_t n;
  58         void *p;
  59         int err = 0;
  60
  61
  62         down(&m->sem);
  63         /* grab buffer if we didn't have one */
  64         if (!m->buf) {
  65                 m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
  66                 if (!m->buf)
  67                         goto Enomem;
  68         }
  69         /* if not empty - flush it first */
  70         if (m->count) {
  71                 n = min(m->count, size);
  72                 err = copy_to_user(buf, m->buf + m->from, n);
  73                 if (err)
  74                         goto Efault;
  75                 m->count -= n;
  76                 m->from += n;
  77                 size -= n;
  78                 buf += n;
  79                 copied += n;
  80                 if (!m->count)
  81                         m->index++;
  82                 if (!size)
  83                         goto Done;
  84         }
  85         /* we need at least one record in buffer */
  86         while (1) {
  87                 pos = m->index;
  88                 p = m->op->start(m, &pos);
  89                 err = PTR_ERR(p);
  90                 if (!p || IS_ERR(p))
  91                         break;
  92                 err = m->op->show(m, p);
  93                 if (err)
  94                         break;
  95                 if (m->count < m->size)
  96                         goto Fill;
  97                 m->op->stop(m, p);
  98                 kfree(m->buf);
  99                 m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
 100                 if (!m->buf)
 101                         goto Enomem;
 102                 m->count = 0;
 103         }
 104         m->op->stop(m, p);
 105         m->count = 0;
 106         goto Done;
 107 Fill:
 108         /* they want more? let's try to get some more */
 109         while (m->count < size) {
 110                 size_t offs = m->count;
 111                 loff_t next = pos;
 112                 p = m->op->next(m, p, &next);
 113                 if (!p || IS_ERR(p)) {
 114                         err = PTR_ERR(p);
 115                         break;
 116                 }
 117                 err = m->op->show(m, p);
 118                 if (err || m->count == m->size) {
 119                         m->count = offs;
 120                         break;
 121                 }
 122                 pos = next;
 123         }
 124         m->op->stop(m, p);
 125         n = min(m->count, size);
 126         err = copy_to_user(buf, m->buf, n);
 127         if (err)
 128                 goto Efault;
 129         copied += n;
 130         m->count -= n;
 131         if (m->count)
 132                 m->from = n;
 133         else
 134                 pos++;
 135         m->index = pos;
 136 Done:
 137         if (!copied)
 138                 copied = err;
 139         else
 140                 *ppos += copied;
 141         up(&m->sem);
 142         return copied;
 143 Enomem:
 144         err = -ENOMEM;
 145         goto Done;
 146 Efault:
 147         err = -EFAULT;
 148         goto Done;
 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 EXPORT_SYMBOL(seq_lseek);
 236
 237 /**
 238  *      seq_release -   free the structures associated with sequential file.
 239  *      @file: file in question
 240  *      @inode: file->f_dentry->d_inode
 241  *
 242  *      Frees the structures associated with sequential file; can be used
 243  *      as ->f_op->release() if you don't have private data to destroy.
 244  */
 245 int seq_release(struct inode *inode, struct file *file)
 246 {
 247         struct seq_file *m = (struct seq_file *)file->private_data;
 248         kfree(m->buf);
 249         kfree(m);
 250         return 0;
 251 }
 252 EXPORT_SYMBOL(seq_release);
 253
 254 /**
 255  *      seq_escape -    print string into buffer, escaping some characters
 256  *      @m:     target buffer
 257  *      @s:     string
 258  *      @esc:   set of characters that need escaping
 259  *
 260  *      Puts string into buffer, replacing each occurrence of character from
 261  *      @esc with usual octal escape.  Returns 0 in case of success, -1 - in
 262  *      case of overflow.
 263  */
 264 int seq_escape(struct seq_file *m, const char *s, const char *esc)
 265 {
 266         char *end = m->buf + m->size;
 267         char *p;
 268         char c;
 269
 270         for (p = m->buf + m->count; (c = *s) != '\0' && p < end; s++) {
 271                 if (!strchr(esc, c)) {
 272                         *p++ = c;
 273                         continue;
 274                 }
 275                 if (p + 3 < end) {
 276                         *p++ = '\\';
 277                         *p++ = '0' + ((c & 0300) >> 6);
 278                         *p++ = '0' + ((c & 070) >> 3);
 279                         *p++ = '0' + (c & 07);
 280                         continue;
 281                 }
 282                 m->count = m->size;
 283                 return -1;
 284         }
 285         m->count = p - m->buf;
 286         return 0;
 287 }
 288 EXPORT_SYMBOL(seq_escape);
 289
 290 int seq_printf(struct seq_file *m, const char *f, ...)
 291 {
 292         va_list args;
 293         int len;
 294
 295         if (m->count < m->size) {
 296                 va_start(args, f);
 297                 len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
 298                 va_end(args);
 299                 if (m->count + len < m->size) {
 300                         m->count += len;
 301                         return 0;
 302                 }
 303         }
 304         m->count = m->size;
 305         return -1;
 306 }
 307 EXPORT_SYMBOL(seq_printf);
 308
 309 int seq_path(struct seq_file *m,
 310              struct vfsmount *mnt, struct dentry *dentry,
 311              char *esc)
 312 {
 313         if (m->count < m->size) {
 314                 char *s = m->buf + m->count;
 315                 char *p = d_path(dentry, mnt, s, m->size - m->count);
 316                 if (!IS_ERR(p)) {
 317                         while (s <= p) {
 318                                 char c = *p++;
 319                                 if (!c) {
 320                                         p = m->buf + m->count;
 321                                         m->count = s - m->buf;
 322                                         return s - p;
 323                                 } else if (!strchr(esc, c)) {
 324                                         *s++ = c;
 325                                 } else if (s + 4 > p) {
 326                                         break;
 327                                 } else {
 328                                         *s++ = '\\';
 329                                         *s++ = '0' + ((c & 0300) >> 6);
 330                                         *s++ = '0' + ((c & 070) >> 3);
 331                                         *s++ = '0' + (c & 07);
 332                                 }
 333                         }
 334                 }
 335         }
 336         m->count = m->size;
 337         return -1;
 338 }
 339 EXPORT_SYMBOL(seq_path);
 340
 341 static void *single_start(struct seq_file *p, loff_t *pos)
 342 {
 343         return NULL + (*pos == 0);
 344 }
 345
 346 static void *single_next(struct seq_file *p, void *v, loff_t *pos)
 347 {
 348         ++*pos;
 349         return NULL;
 350 }
 351
 352 static void single_stop(struct seq_file *p, void *v)
 353 {
 354 }
 355
 356 int single_open(struct file *file, int (*show)(struct seq_file *, void *),
 357                 void *data)
 358 {
 359         struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL);
 360         int res = -ENOMEM;
 361
 362         if (op) {
 363                 op->start = single_start;
 364                 op->next = single_next;
 365                 op->stop = single_stop;
 366                 op->show = show;
 367                 res = seq_open(file, op);
 368                 if (!res)
 369                         ((struct seq_file *)file->private_data)->private = data;
 370                 else
 371                         kfree(op);
 372         }
 373         return res;
 374 }
 375 EXPORT_SYMBOL(single_open);
 376
 377 int single_release(struct inode *inode, struct file *file)
 378 {
 379         struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
 380         int res = seq_release(inode, file);
 381         kfree(op);
 382         return res;
 383 }
 384 EXPORT_SYMBOL(single_release);
 385
 386 int seq_release_private(struct inode *inode, struct file *file)
 387 {
 388         struct seq_file *seq = file->private_data;
 389
 390         kfree(seq->private);
 391         seq->private = NULL;
 392         return seq_release(inode, file);
 393 }
 394 EXPORT_SYMBOL(seq_release_private);
 395
 396 int seq_putc(struct seq_file *m, char c)
 397 {
 398         if (m->count < m->size) {
 399                 m->buf[m->count++] = c;
 400                 return 0;
 401         }
 402         return -1;
 403 }
 404 EXPORT_SYMBOL(seq_putc);
 405
 406 int seq_puts(struct seq_file *m, const char *s)
 407 {
 408         int len = strlen(s);
 409         if (m->count + len < m->size) {
 410                 memcpy(m->buf + m->count, s, len);
 411                 m->count += len;
 412                 return 0;
 413         }
 414         m->count = m->size;
 415         return -1;
 416 }
 417 EXPORT_SYMBOL(seq_puts);