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/seq_file.h>
  10 #include <linux/slab.h>
  11
  12 #include <asm/uaccess.h>
  13 #include <asm/page.h>
  14
  15 /**
  16  *      seq_open -      initialize sequential file
  17  *      @file: file we initialize
  18  *      @op: method table describing the sequence
  19  *
  20  *      seq_open() sets @file, associating it with a sequence described
  21  *      by @op.  @op->start() sets the iterator up and returns the first
  22  *      element of sequence. @op->stop() shuts it down.  @op->next()
  23  *      returns the next element of sequence.  @op->show() prints element
  24  *      into the buffer.  In case of error ->start() and ->next() return
  25  *      ERR_PTR(error).  In the end of sequence they return %NULL. ->show()
  26  *      returns 0 in case of success and negative number in case of error.
  27  */
  28 int seq_open(struct file *file, struct seq_operations *op)
  29 {
  30         struct seq_file *p = kmalloc(sizeof(*p), GFP_KERNEL);
  31         if (!p)
  32                 return -ENOMEM;
  33         memset(p, 0, sizeof(*p));
  34         sema_init(&p->sem, 1);
  35         p->op = op;
  36         file->private_data = p;
  37         return 0;
  38 }
  39
  40 /**
  41  *      seq_read -      ->read() method for sequential files.
  42  *      @file, @buf, @size, @ppos: see file_operations method
  43  *
  44  *      Ready-made ->f_op->read()
  45  */
  46 ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
  47 {
  48         struct seq_file *m = (struct seq_file *)file->private_data;
  49         size_t copied = 0;
  50         loff_t pos;
  51         size_t n;
  52         void *p;
  53         int err = 0;
  54
  55         if (ppos != &file->f_pos)
  56                 return -EPIPE;
  57
  58         down(&m->sem);
  59         /* grab buffer if we didn't have one */
  60         if (!m->buf) {
  61                 m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
  62                 if (!m->buf)
  63                         goto Enomem;
  64         }
  65         /* if not empty - flush it first */
  66         if (m->count) {
  67                 n = min(m->count, size);
  68                 err = copy_to_user(buf, m->buf + m->from, n);
  69                 if (err)
  70                         goto Efault;
  71                 m->count -= n;
  72                 m->from += n;
  73                 size -= n;
  74                 buf += n;
  75                 copied += n;
  76                 if (!m->count)
  77                         m->index++;
  78                 if (!size)
  79                         goto Done;
  80         }
  81         /* we need at least one record in buffer */
  82         while (1) {
  83                 pos = m->index;
  84                 p = m->op->start(m, &pos);
  85                 err = PTR_ERR(p);
  86                 if (!p || IS_ERR(p))
  87                         break;
  88                 err = m->op->show(m, p);
  89                 if (err)
  90                         break;
  91                 if (m->count < m->size)
  92                         goto Fill;
  93                 m->op->stop(m, p);
  94                 kfree(m->buf);
  95                 m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
  96                 if (!m->buf)
  97                         goto Enomem;
  98                 m->count = 0;
  99         }
 100         m->op->stop(m, p);
 101         m->count = 0;
 102         goto Done;
 103 Fill:
 104         /* they want more? let's try to get some more */
 105         while (m->count < size) {
 106                 size_t offs = m->count;
 107                 loff_t next = pos;
 108                 p = m->op->next(m, p, &next);
 109                 if (!p || IS_ERR(p)) {
 110                         err = PTR_ERR(p);
 111                         break;
 112                 }
 113                 err = m->op->show(m, p);
 114                 if (err || m->count == m->size) {
 115                         m->count = offs;
 116                         break;
 117                 }
 118                 pos = next;
 119         }
 120         m->op->stop(m, p);
 121         n = min(m->count, size);
 122         err = copy_to_user(buf, m->buf, n);
 123         if (err)
 124                 goto Efault;
 125         copied += n;
 126         m->count -= n;
 127         if (m->count)
 128                 m->from = n;
 129         else
 130                 pos++;
 131         m->index = pos;
 132 Done:
 133         if (!copied)
 134                 copied = err;
 135         else
 136                 *ppos += copied;
 137         up(&m->sem);
 138         return copied;
 139 Enomem:
 140         err = -ENOMEM;
 141         goto Done;
 142 Efault:
 143         err = -EFAULT;
 144         goto Done;
 145 }
 146
 147 static int traverse(struct seq_file *m, loff_t offset)
 148 {
 149         loff_t pos = 0;
 150         int error = 0;
 151         void *p;
 152
 153         m->index = 0;
 154         m->count = m->from = 0;
 155         if (!offset)
 156                 return 0;
 157         if (!m->buf) {
 158                 m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
 159                 if (!m->buf)
 160                         return -ENOMEM;
 161         }
 162         p = m->op->start(m, &m->index);
 163         while (p) {
 164                 error = PTR_ERR(p);
 165                 if (IS_ERR(p))
 166                         break;
 167                 error = m->op->show(m, p);
 168                 if (error)
 169                         break;
 170                 if (m->count == m->size)
 171                         goto Eoverflow;
 172                 if (pos + m->count > offset) {
 173                         m->from = offset - pos;
 174                         m->count -= m->from;
 175                         break;
 176                 }
 177                 pos += m->count;
 178                 m->count = 0;
 179                 if (pos == offset) {
 180                         m->index++;
 181                         break;
 182                 }
 183                 p = m->op->next(m, p, &m->index);
 184         }
 185         m->op->stop(m, p);
 186         return error;
 187
 188 Eoverflow:
 189         m->op->stop(m, p);
 190         kfree(m->buf);
 191         m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
 192         return !m->buf ? -ENOMEM : -EAGAIN;
 193 }
 194
 195 /**
 196  *      seq_lseek -     ->llseek() method for sequential files.
 197  *      @file, @offset, @origin: see file_operations method
 198  *
 199  *      Ready-made ->f_op->llseek()
 200  */
 201 loff_t seq_lseek(struct file *file, loff_t offset, int origin)
 202 {
 203         struct seq_file *m = (struct seq_file *)file->private_data;
 204         long long retval = -EINVAL;
 205
 206         down(&m->sem);
 207         switch (origin) {
 208                 case 1:
 209                         offset += file->f_pos;
 210                 case 0:
 211                         if (offset < 0)
 212                                 break;
 213                         retval = offset;
 214                         if (offset != file->f_pos) {
 215                                 while ((retval=traverse(m, offset)) == -EAGAIN)
 216                                         ;
 217                                 if (retval) {
 218                                         /* with extreme prejudice... */
 219                                         file->f_pos = 0;
 220                                         m->index = 0;
 221                                         m->count = 0;
 222                                 } else {
 223                                         retval = file->f_pos = offset;
 224                                 }
 225                         }
 226         }
 227         up(&m->sem);
 228         return retval;
 229 }
 230
 231 /**
 232  *      seq_release -   free the structures associated with sequential file.
 233  *      @file: file in question
 234  *      @inode: file->f_dentry->d_inode
 235  *
 236  *      Frees the structures associated with sequential file; can be used
 237  *      as ->f_op->release() if you don't have private data to destroy.
 238  */
 239 int seq_release(struct inode *inode, struct file *file)
 240 {
 241         struct seq_file *m = (struct seq_file *)file->private_data;
 242         kfree(m->buf);
 243         kfree(m);
 244         return 0;
 245 }
 246
 247 /**
 248  *      seq_escape -    print string into buffer, escaping some characters
 249  *      @m:     target buffer
 250  *      @s:     string
 251  *      @esc:   set of characters that need escaping
 252  *
 253  *      Puts string into buffer, replacing each occurrence of character from
 254  *      @esc with usual octal escape.  Returns 0 in case of success, -1 - in
 255  *      case of overflow.
 256  */
 257 int seq_escape(struct seq_file *m, const char *s, const char *esc)
 258 {
 259         char *end = m->buf + m->size;
 260         char *p;
 261         char c;
 262
 263         for (p = m->buf + m->count; (c = *s) != '\0' && p < end; s++) {
 264                 if (!strchr(esc, c)) {
 265                         *p++ = c;
 266                         continue;
 267                 }
 268                 if (p + 3 < end) {
 269                         *p++ = '\\';
 270                         *p++ = '0' + ((c & 0300) >> 6);
 271                         *p++ = '0' + ((c & 070) >> 3);
 272                         *p++ = '0' + (c & 07);
 273                         continue;
 274                 }
 275                 m->count = m->size;
 276                 return -1;
 277         }
 278         m->count = p - m->buf;
 279         return 0;
 280 }
 281
 282 int seq_printf(struct seq_file *m, const char *f, ...)
 283 {
 284         va_list args;
 285         int len;
 286
 287         if (m->count < m->size) {
 288                 va_start(args, f);
 289                 len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
 290                 va_end(args);
 291                 if (m->count + len < m->size) {
 292                         m->count += len;
 293                         return 0;
 294                 }
 295         }
 296         m->count = m->size;
 297         return -1;
 298 }
 299
 300 int seq_path(struct seq_file *m,
 301                 struct vfsmount *mnt, struct dentry *dentry,
 302                 char *esc)
 303 {
 304         if (m->count < m->size) {
 305                 char *s = m->buf + m->count;
 306                 char *p = d_path(dentry, mnt, s, m->size - m->count);
 307                 if (!IS_ERR(p)) {
 308                         while (s <= p) {
 309                                 char c = *p++;
 310                                 if (!c) {
 311                                         p = m->buf + m->count;
 312                                         m->count = s - m->buf;
 313                                         return s - p;
 314                                 } else if (!strchr(esc, c)) {
 315                                         *s++ = c;
 316                                 } else if (s + 4 > p) {
 317                                         break;
 318                                 } else {
 319                                         *s++ = '\\';
 320                                         *s++ = '0' + ((c & 0300) >> 6);
 321                                         *s++ = '0' + ((c & 070) >> 3);
 322                                         *s++ = '0' + (c & 07);
 323                                 }
 324                         }
 325                 }
 326         }
 327         m->count = m->size;
 328         return -1;
 329 }
 330
 331 static void *single_start(struct seq_file *p, loff_t *pos)
 332 {
 333         return NULL + (*pos == 0);
 334 }
 335
 336 static void *single_next(struct seq_file *p, void *v, loff_t *pos)
 337 {
 338         ++*pos;
 339         return NULL;
 340 }
 341
 342 static void single_stop(struct seq_file *p, void *v)
 343 {
 344 }
 345
 346 int single_open(struct file *file, int (*show)(struct seq_file *, void*), void *data)
 347 {
 348         struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL);
 349         int res = -ENOMEM;
 350
 351         if (op) {
 352                 op->start = single_start;
 353                 op->next = single_next;
 354                 op->stop = single_stop;
 355                 op->show = show;
 356                 res = seq_open(file, op);
 357                 if (!res)
 358                         ((struct seq_file *)file->private_data)->private = data;
 359                 else
 360                         kfree(op);
 361         }
 362         return res;
 363 }
 364
 365 int single_release(struct inode *inode, struct file *file)
 366 {
 367         struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
 368         int res = seq_release(inode, file);
 369         kfree(op);
 370         return res;
 371 }
 372
 373 int seq_release_private(struct inode *inode, struct file *file)
 374 {
 375         struct seq_file *seq = file->private_data;
 376
 377         kfree(seq->private);
 378         seq->private = NULL;
 379         return seq_release(inode, file);
 380 }
 381