fs/romfs/inode.c

   1 /*
   2  * ROMFS file system, Linux implementation
   3  *
   4  * Copyright (C) 1997-1999  Janos Farkas <chexum@shadow.banki.hu>
   5  *
   6  * Using parts of the minix filesystem
   7  * Copyright (C) 1991, 1992  Linus Torvalds
   8  *
   9  * and parts of the affs filesystem additionally
  10  * Copyright (C) 1993  Ray Burr
  11  * Copyright (C) 1996  Hans-Joachim Widmaier
  12  *
  13  * This program is free software; you can redistribute it and/or
  14  * modify it under the terms of the GNU General Public License
  15  * as published by the Free Software Foundation; either version
  16  * 2 of the License, or (at your option) any later version.
  17  *
  18  * Changes
  19  *                                      Changed for 2.1.19 modules
  20  *      Jan 1997                        Initial release
  21  *      Jun 1997                        2.1.43+ changes
  22  *                                      Proper page locking in readpage
  23  *                                      Changed to work with 2.1.45+ fs
  24  *      Jul 1997                        Fixed follow_link
  25  *                      2.1.47
  26  *                                      lookup shouldn't return -ENOENT
  27  *                                      from Horst von Brand:
  28  *                                        fail on wrong checksum
  29  *                                        double unlock_super was possible
  30  *                                        correct namelen for statfs
  31  *                                      spotted by Bill Hawes:
  32  *                                        readlink shouldn't iput()
  33  *      Jun 1998        2.1.106         from Avery Pennarun: glibc scandir()
  34  *                                        exposed a problem in readdir
  35  *                      2.1.107         code-freeze spellchecker run
  36  *      Aug 1998                        2.1.118+ VFS changes
  37  *      Sep 1998        2.1.122         another VFS change (follow_link)
  38  *      Apr 1999        2.2.7           no more EBADF checking in
  39  *                                        lookup/readdir, use ERR_PTR
  40  *      Jun 1999        2.3.6           d_alloc_root use changed
  41  *                      2.3.9           clean up usage of ENOENT/negative
  42  *                                        dentries in lookup
  43  *                                      clean up page flags setting
  44  *                                        (error, uptodate, locking) in
  45  *                                        in readpage
  46  *                                      use init_special_inode for
  47  *                                        fifos/sockets (and streamline) in
  48  *                                        read_inode, fix _ops table order
  49  *      Aug 1999        2.3.16          __initfunc() => __init change
  50  *      Oct 1999        2.3.24          page->owner hack obsoleted
  51  *      Nov 1999        2.3.27          2.3.25+ page->offset => index change
  52  */
  53
  54 /* todo:
  55  *      - see Documentation/filesystems/romfs.txt
  56  *      - use allocated, not stack memory for file names?
  57  *      - considering write access...
  58  *      - network (tftp) files?
  59  *      - merge back some _op tables
  60  */
  61
  62 /*
  63  * Sorry about some optimizations and for some goto's.  I just wanted
  64  * to squeeze some more bytes out of this code.. :)
  65  */
  66
  67 #include <linux/module.h>
  68 #include <linux/types.h>
  69 #include <linux/errno.h>
  70 #include <linux/malloc.h>
  71 #include <linux/romfs_fs.h>
  72 #include <linux/fs.h>
  73 #include <linux/locks.h>
  74 #include <linux/init.h>
  75 #include <linux/smp_lock.h>
  76
  77 #include <asm/uaccess.h>
  78
  79 static int inline min(int a, int b)
  80 {
  81         return a<b ? a : b;
  82 }
  83
  84 static __s32
  85 romfs_checksum(void *data, int size)
  86 {
  87         __s32 sum, *ptr;
  88
  89         sum = 0; ptr = data;
  90         size>>=2;
  91         while (size>0) {
  92                 sum += ntohl(*ptr++);
  93                 size--;
  94         }
  95         return sum;
  96 }
  97
  98 static struct super_operations romfs_ops;
  99
 100 static struct super_block *
 101 romfs_read_super(struct super_block *s, void *data, int silent)
 102 {
 103         struct buffer_head *bh;
 104         kdev_t dev = s->s_dev;
 105         struct romfs_super_block *rsb;
 106         int sz;
 107
 108         /* I would parse the options here, but there are none.. :) */
 109
 110         set_blocksize(dev, ROMBSIZE);
 111         s->s_blocksize = ROMBSIZE;
 112         s->s_blocksize_bits = ROMBSBITS;
 113         bh = bread(dev, 0, ROMBSIZE);
 114         if (!bh) {
 115                 /* XXX merge with other printk? */
 116                 printk ("romfs: unable to read superblock\n");
 117                 goto outnobh;
 118         }
 119
 120         rsb = (struct romfs_super_block *)bh->b_data;
 121         sz = ntohl(rsb->size);
 122         if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1
 123            || sz < ROMFH_SIZE) {
 124                 if (!silent)
 125                         printk ("VFS: Can't find a romfs filesystem on dev "
 126                                 "%s.\n", kdevname(dev));
 127                 goto out;
 128         }
 129         if (romfs_checksum(rsb, min(sz,512))) {
 130                 printk ("romfs: bad initial checksum on dev "
 131                         "%s.\n", kdevname(dev));
 132                 goto out;
 133         }
 134
 135         s->s_magic = ROMFS_MAGIC;
 136         s->u.romfs_sb.s_maxsize = sz;
 137
 138         s->s_flags |= MS_RDONLY;
 139
 140         /* Find the start of the fs */
 141         sz = (ROMFH_SIZE +
 142               strnlen(rsb->name, ROMFS_MAXFN) + 1 + ROMFH_PAD)
 143              & ROMFH_MASK;
 144
 145         brelse(bh);
 146
 147         s->s_op = &romfs_ops;
 148         s->s_root = d_alloc_root(iget(s, sz));
 149
 150         if (!s->s_root)
 151                 goto outnobh;
 152
 153         /* Ehrhm; sorry.. :)  And thanks to Hans-Joachim Widmaier  :) */
 154         if (0) {
 155 out:
 156                 brelse(bh);
 157 outnobh:
 158                 s = NULL;
 159         }
 160
 161         return s;
 162 }
 163
 164 /* That's simple too. */
 165
 166 static int
 167 romfs_statfs(struct super_block *sb, struct statfs *buf)
 168 {
 169         buf->f_type = ROMFS_MAGIC;
 170         buf->f_bsize = ROMBSIZE;
 171         buf->f_bfree = buf->f_bavail = buf->f_ffree;
 172         buf->f_blocks = (sb->u.romfs_sb.s_maxsize+ROMBSIZE-1)>>ROMBSBITS;
 173         buf->f_namelen = ROMFS_MAXFN;
 174         return 0;
 175 }
 176
 177 /* some helper routines */
 178
 179 static int
 180 romfs_strnlen(struct inode *i, unsigned long offset, unsigned long count)
 181 {
 182         struct buffer_head *bh;
 183         unsigned long avail, maxsize, res;
 184
 185         maxsize = i->i_sb->u.romfs_sb.s_maxsize;
 186         if (offset >= maxsize)
 187                 return -1;
 188
 189         /* strnlen is almost always valid */
 190         if (count > maxsize || offset+count > maxsize)
 191                 count = maxsize-offset;
 192
 193         bh = bread(i->i_dev, offset>>ROMBSBITS, ROMBSIZE);
 194         if (!bh)
 195                 return -1;              /* error */
 196
 197         avail = ROMBSIZE - (offset & ROMBMASK);
 198         maxsize = min(count, avail);
 199         res = strnlen(((char *)bh->b_data)+(offset&ROMBMASK), maxsize);
 200         brelse(bh);
 201
 202         if (res < maxsize)
 203                 return res;             /* found all of it */
 204
 205         while (res < count) {
 206                 offset += maxsize;
 207
 208                 bh = bread(i->i_dev, offset>>ROMBSBITS, ROMBSIZE);
 209                 if (!bh)
 210                         return -1;
 211                 maxsize = min(count-res, ROMBSIZE);
 212                 avail = strnlen(bh->b_data, maxsize);
 213                 res += avail;
 214                 brelse(bh);
 215                 if (avail < maxsize)
 216                         return res;
 217         }
 218         return res;
 219 }
 220
 221 static int
 222 romfs_copyfrom(struct inode *i, void *dest, unsigned long offset, unsigned long count)
 223 {
 224         struct buffer_head *bh;
 225         unsigned long avail, maxsize, res;
 226
 227         maxsize = i->i_sb->u.romfs_sb.s_maxsize;
 228         if (offset >= maxsize || count > maxsize || offset+count>maxsize)
 229                 return -1;
 230
 231         bh = bread(i->i_dev, offset>>ROMBSBITS, ROMBSIZE);
 232         if (!bh)
 233                 return -1;              /* error */
 234
 235         avail = ROMBSIZE - (offset & ROMBMASK);
 236         maxsize = min(count, avail);
 237         memcpy(dest, ((char *)bh->b_data) + (offset & ROMBMASK), maxsize);
 238         brelse(bh);
 239
 240         res = maxsize;                  /* all of it */
 241
 242         while (res < count) {
 243                 offset += maxsize;
 244                 dest += maxsize;
 245
 246                 bh = bread(i->i_dev, offset>>ROMBSBITS, ROMBSIZE);
 247                 if (!bh)
 248                         return -1;
 249                 maxsize = min(count-res, ROMBSIZE);
 250                 memcpy(dest, bh->b_data, maxsize);
 251                 brelse(bh);
 252                 res += maxsize;
 253         }
 254         return res;
 255 }
 256
 257 static unsigned char romfs_dtype_table[] = {
 258         DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO
 259 };
 260
 261 static int
 262 romfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 263 {
 264         struct inode *i = filp->f_dentry->d_inode;
 265         struct romfs_inode ri;
 266         unsigned long offset, maxoff;
 267         int j, ino, nextfh;
 268         int stored = 0;
 269         char fsname[ROMFS_MAXFN];       /* XXX dynamic? */
 270
 271         maxoff = i->i_sb->u.romfs_sb.s_maxsize;
 272
 273         offset = filp->f_pos;
 274         if (!offset) {
 275                 offset = i->i_ino & ROMFH_MASK;
 276                 if (romfs_copyfrom(i, &ri, offset, ROMFH_SIZE) <= 0)
 277                         return stored;
 278                 offset = ntohl(ri.spec) & ROMFH_MASK;
 279         }
 280
 281         /* Not really failsafe, but we are read-only... */
 282         for(;;) {
 283                 if (!offset || offset >= maxoff) {
 284                         offset = maxoff;
 285                         filp->f_pos = offset;
 286                         return stored;
 287                 }
 288                 filp->f_pos = offset;
 289
 290                 /* Fetch inode info */
 291                 if (romfs_copyfrom(i, &ri, offset, ROMFH_SIZE) <= 0)
 292                         return stored;
 293
 294                 j = romfs_strnlen(i, offset+ROMFH_SIZE, sizeof(fsname)-1);
 295                 if (j < 0)
 296                         return stored;
 297
 298                 fsname[j]=0;
 299                 romfs_copyfrom(i, fsname, offset+ROMFH_SIZE, j);
 300
 301                 ino = offset;
 302                 nextfh = ntohl(ri.next);
 303                 if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
 304                         ino = ntohl(ri.spec);
 305                 if (filldir(dirent, fsname, j, offset, ino,
 306                             romfs_dtype_table[nextfh & ROMFH_TYPE]) < 0) {
 307                         return stored;
 308                 }
 309                 stored++;
 310                 offset = nextfh & ROMFH_MASK;
 311         }
 312 }
 313
 314 static struct dentry *
 315 romfs_lookup(struct inode *dir, struct dentry *dentry)
 316 {
 317         unsigned long offset, maxoff;
 318         int fslen, res;
 319         struct inode *inode;
 320         char fsname[ROMFS_MAXFN];       /* XXX dynamic? */
 321         struct romfs_inode ri;
 322         const char *name;               /* got from dentry */
 323         int len;
 324
 325         res = -EACCES;                  /* placeholder for "no data here" */
 326         offset = dir->i_ino & ROMFH_MASK;
 327         if (romfs_copyfrom(dir, &ri, offset, ROMFH_SIZE) <= 0)
 328                 goto out;
 329
 330         maxoff = dir->i_sb->u.romfs_sb.s_maxsize;
 331         offset = ntohl(ri.spec) & ROMFH_MASK;
 332
 333         /* OK, now find the file whose name is in "dentry" in the
 334          * directory specified by "dir".  */
 335
 336         name = dentry->d_name.name;
 337         len = dentry->d_name.len;
 338
 339         for(;;) {
 340                 if (!offset || offset >= maxoff)
 341                         goto out0;
 342                 if (romfs_copyfrom(dir, &ri, offset, ROMFH_SIZE) <= 0)
 343                         goto out;
 344
 345                 /* try to match the first 16 bytes of name */
 346                 fslen = romfs_strnlen(dir, offset+ROMFH_SIZE, ROMFH_SIZE);
 347                 if (len < ROMFH_SIZE) {
 348                         if (len == fslen) {
 349                                 /* both are shorter, and same size */
 350                                 romfs_copyfrom(dir, fsname, offset+ROMFH_SIZE, len+1);
 351                                 if (strncmp (name, fsname, len) == 0)
 352                                         break;
 353                         }
 354                 } else if (fslen >= ROMFH_SIZE) {
 355                         /* both are longer; XXX optimize max size */
 356                         fslen = romfs_strnlen(dir, offset+ROMFH_SIZE, sizeof(fsname)-1);
 357                         if (len == fslen) {
 358                                 romfs_copyfrom(dir, fsname, offset+ROMFH_SIZE, len+1);
 359                                 if (strncmp(name, fsname, len) == 0)
 360                                         break;
 361                         }
 362                 }
 363                 /* next entry */
 364                 offset = ntohl(ri.next) & ROMFH_MASK;
 365         }
 366
 367         /* Hard link handling */
 368         if ((ntohl(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
 369                 offset = ntohl(ri.spec) & ROMFH_MASK;
 370
 371         if ((inode = iget(dir->i_sb, offset)))
 372                 goto outi;
 373
 374         /*
 375          * it's a bit funky, _lookup needs to return an error code
 376          * (negative) or a NULL, both as a dentry.  ENOENT should not
 377          * be returned, instead we need to create a negative dentry by
 378          * d_add(dentry, NULL); and return 0 as no error.
 379          * (Although as I see, it only matters on writable file
 380          * systems).
 381          */
 382
 383 out0:   inode = NULL;
 384 outi:   res = 0;
 385         d_add (dentry, inode);
 386
 387 out:    return ERR_PTR(res);
 388 }
 389
 390 /*
 391  * Ok, we do readpage, to be able to execute programs.  Unfortunately,
 392  * we can't use bmap, since we may have looser alignments.
 393  */
 394
 395 static int
 396 romfs_readpage(struct file *file, struct page * page)
 397 {
 398         struct inode *inode = (struct inode*)page->mapping->host;
 399         unsigned long offset, avail, readlen;
 400         void *buf;
 401         int result = -EIO;
 402
 403         lock_kernel();
 404         get_page(page);
 405         buf = page_address(page);
 406
 407         /* 32 bit warning -- but not for us :) */
 408         offset = page->index << PAGE_CACHE_SHIFT;
 409         if (offset < inode->i_size) {
 410                 avail = inode->i_size-offset;
 411                 readlen = min(avail, PAGE_SIZE);
 412                 if (romfs_copyfrom(inode, buf, inode->u.romfs_i.i_dataoffset+offset, readlen) == readlen) {
 413                         if (readlen < PAGE_SIZE) {
 414                                 memset(buf + readlen,0,PAGE_SIZE-readlen);
 415                         }
 416                         SetPageUptodate(page);
 417                         result = 0;
 418                 }
 419         }
 420         if (result) {
 421                 memset(buf, 0, PAGE_SIZE);
 422                 SetPageError(page);
 423         }
 424         flush_dcache_page(page);
 425
 426         UnlockPage(page);
 427
 428         __free_page(page);
 429         unlock_kernel();
 430
 431         return result;
 432 }
 433
 434 /* Mapping from our types to the kernel */
 435
 436 static struct address_space_operations romfs_aops = {
 437         readpage: romfs_readpage
 438 };
 439
 440 static struct file_operations romfs_dir_operations = {
 441         read:           generic_read_dir,
 442         readdir:        romfs_readdir,
 443 };
 444
 445 static struct inode_operations romfs_dir_inode_operations = {
 446         lookup:         romfs_lookup,
 447 };
 448
 449 static mode_t romfs_modemap[] =
 450 {
 451         0, S_IFDIR+0644, S_IFREG+0644, S_IFLNK+0777,
 452         S_IFBLK+0600, S_IFCHR+0600, S_IFSOCK+0644, S_IFIFO+0644
 453 };
 454
 455 static void
 456 romfs_read_inode(struct inode *i)
 457 {
 458         int nextfh, ino;
 459         struct romfs_inode ri;
 460
 461         ino = i->i_ino & ROMFH_MASK;
 462         i->i_mode = 0;
 463
 464         /* Loop for finding the real hard link */
 465         for(;;) {
 466                 if (romfs_copyfrom(i, &ri, ino, ROMFH_SIZE) <= 0) {
 467                         printk("romfs: read error for inode 0x%x\n", ino);
 468                         return;
 469                 }
 470                 /* XXX: do romfs_checksum here too (with name) */
 471
 472                 nextfh = ntohl(ri.next);
 473                 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
 474                         break;
 475
 476                 ino = ntohl(ri.spec) & ROMFH_MASK;
 477         }
 478
 479         i->i_nlink = 1;         /* Hard to decide.. */
 480         i->i_size = ntohl(ri.size);
 481         i->i_mtime = i->i_atime = i->i_ctime = 0;
 482         i->i_uid = i->i_gid = 0;
 483
 484         /* Precalculate the data offset */
 485         ino = romfs_strnlen(i, ino+ROMFH_SIZE, ROMFS_MAXFN);
 486         if (ino >= 0)
 487                 ino = ((ROMFH_SIZE+ino+1+ROMFH_PAD)&ROMFH_MASK);
 488         else
 489                 ino = 0;
 490
 491         i->u.romfs_i.i_metasize = ino;
 492         i->u.romfs_i.i_dataoffset = ino+(i->i_ino&ROMFH_MASK);
 493
 494         /* Compute permissions */
 495         ino = romfs_modemap[nextfh & ROMFH_TYPE];
 496         /* only "normal" files have ops */
 497         switch (nextfh & ROMFH_TYPE) {
 498                 case 1:
 499                         i->i_size = i->u.romfs_i.i_metasize;
 500                         i->i_op = &romfs_dir_inode_operations;
 501                         i->i_fop = &romfs_dir_operations;
 502                         if (nextfh & ROMFH_EXEC)
 503                                 ino |= S_IXUGO;
 504                         i->i_mode = ino;
 505                         break;
 506                 case 2:
 507                         i->i_fop = &generic_ro_fops;
 508                         i->i_data.a_ops = &romfs_aops;
 509                         if (nextfh & ROMFH_EXEC)
 510                                 ino |= S_IXUGO;
 511                         i->i_mode = ino;
 512                         break;
 513                 case 3:
 514                         i->i_op = &page_symlink_inode_operations;
 515                         i->i_data.a_ops = &romfs_aops;
 516                         i->i_mode = ino | S_IRWXUGO;
 517                         break;
 518                 default:
 519                         /* depending on MBZ for sock/fifos */
 520                         nextfh = ntohl(ri.spec);
 521                         nextfh = kdev_t_to_nr(MKDEV(nextfh>>16,nextfh&0xffff));
 522                         init_special_inode(i, ino, nextfh);
 523         }
 524 }
 525
 526 static struct super_operations romfs_ops = {
 527         read_inode:     romfs_read_inode,
 528         statfs:         romfs_statfs,
 529 };
 530
 531 static DECLARE_FSTYPE_DEV(romfs_fs_type, "romfs", romfs_read_super);
 532
 533 static int __init init_romfs_fs(void)
 534 {
 535         return register_filesystem(&romfs_fs_type);
 536 }
 537
 538 static void __exit exit_romfs_fs(void)
 539 {
 540         unregister_filesystem(&romfs_fs_type);
 541 }
 542
 543 /* Yes, works even as a module... :) */
 544
 545 EXPORT_NO_SYMBOLS;
 546
 547 module_init(init_romfs_fs)
 548 module_exit(exit_romfs_fs)