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/slab.h>
  71 #include <linux/romfs_fs.h>
  72 #include <linux/fs.h>
  73 #include <linux/init.h>
  74 #include <linux/pagemap.h>
  75 #include <linux/smp_lock.h>
  76 #include <linux/buffer_head.h>
  77 #include <linux/vfs.h>
  78
  79 #include <asm/uaccess.h>
  80
  81 struct romfs_inode_info {
  82         unsigned long i_metasize;       /* size of non-data area */
  83         unsigned long i_dataoffset;     /* from the start of fs */
  84         struct inode vfs_inode;
  85 };
  86
  87 /* instead of private superblock data */
  88 static inline unsigned long romfs_maxsize(struct super_block *sb)
  89 {
  90         return (unsigned long)sb->s_fs_info;
  91 }
  92
  93 static inline struct romfs_inode_info *ROMFS_I(struct inode *inode)
  94 {
  95         return list_entry(inode, struct romfs_inode_info, vfs_inode);
  96 }
  97
  98 static __u32
  99 romfs_checksum(void *data, int size)
 100 {
 101         __u32 sum;
 102         __be32 *ptr;
 103
 104         sum = 0; ptr = data;
 105         size>>=2;
 106         while (size>0) {
 107                 sum += be32_to_cpu(*ptr++);
 108                 size--;
 109         }
 110         return sum;
 111 }
 112
 113 static const struct super_operations romfs_ops;
 114
 115 static int romfs_fill_super(struct super_block *s, void *data, int silent)
 116 {
 117         struct buffer_head *bh;
 118         struct romfs_super_block *rsb;
 119         struct inode *root;
 120         int sz;
 121
 122         /* I would parse the options here, but there are none.. :) */
 123
 124         sb_set_blocksize(s, ROMBSIZE);
 125         s->s_maxbytes = 0xFFFFFFFF;
 126
 127         bh = sb_bread(s, 0);
 128         if (!bh) {
 129                 /* XXX merge with other printk? */
 130                 printk ("romfs: unable to read superblock\n");
 131                 goto outnobh;
 132         }
 133
 134         rsb = (struct romfs_super_block *)bh->b_data;
 135         sz = be32_to_cpu(rsb->size);
 136         if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1
 137            || sz < ROMFH_SIZE) {
 138                 if (!silent)
 139                         printk ("VFS: Can't find a romfs filesystem on dev "
 140                                 "%s.\n", s->s_id);
 141                 goto out;
 142         }
 143         if (romfs_checksum(rsb, min_t(int, sz, 512))) {
 144                 printk ("romfs: bad initial checksum on dev "
 145                         "%s.\n", s->s_id);
 146                 goto out;
 147         }
 148
 149         s->s_magic = ROMFS_MAGIC;
 150         s->s_fs_info = (void *)(long)sz;
 151
 152         s->s_flags |= MS_RDONLY;
 153
 154         /* Find the start of the fs */
 155         sz = (ROMFH_SIZE +
 156               strnlen(rsb->name, ROMFS_MAXFN) + 1 + ROMFH_PAD)
 157              & ROMFH_MASK;
 158
 159         s->s_op = &romfs_ops;
 160         root = iget(s, sz);
 161         if (!root)
 162                 goto out;
 163
 164         s->s_root = d_alloc_root(root);
 165         if (!s->s_root)
 166                 goto outiput;
 167
 168         brelse(bh);
 169         return 0;
 170
 171 outiput:
 172         iput(root);
 173 out:
 174         brelse(bh);
 175 outnobh:
 176         return -EINVAL;
 177 }
 178
 179 /* That's simple too. */
 180
 181 static int
 182 romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 183 {
 184         buf->f_type = ROMFS_MAGIC;
 185         buf->f_bsize = ROMBSIZE;
 186         buf->f_bfree = buf->f_bavail = buf->f_ffree;
 187         buf->f_blocks = (romfs_maxsize(dentry->d_sb)+ROMBSIZE-1)>>ROMBSBITS;
 188         buf->f_namelen = ROMFS_MAXFN;
 189         return 0;
 190 }
 191
 192 /* some helper routines */
 193
 194 static int
 195 romfs_strnlen(struct inode *i, unsigned long offset, unsigned long count)
 196 {
 197         struct buffer_head *bh;
 198         unsigned long avail, maxsize, res;
 199
 200         maxsize = romfs_maxsize(i->i_sb);
 201         if (offset >= maxsize)
 202                 return -1;
 203
 204         /* strnlen is almost always valid */
 205         if (count > maxsize || offset+count > maxsize)
 206                 count = maxsize-offset;
 207
 208         bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
 209         if (!bh)
 210                 return -1;              /* error */
 211
 212         avail = ROMBSIZE - (offset & ROMBMASK);
 213         maxsize = min_t(unsigned long, count, avail);
 214         res = strnlen(((char *)bh->b_data)+(offset&ROMBMASK), maxsize);
 215         brelse(bh);
 216
 217         if (res < maxsize)
 218                 return res;             /* found all of it */
 219
 220         while (res < count) {
 221                 offset += maxsize;
 222
 223                 bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
 224                 if (!bh)
 225                         return -1;
 226                 maxsize = min_t(unsigned long, count - res, ROMBSIZE);
 227                 avail = strnlen(bh->b_data, maxsize);
 228                 res += avail;
 229                 brelse(bh);
 230                 if (avail < maxsize)
 231                         return res;
 232         }
 233         return res;
 234 }
 235
 236 static int
 237 romfs_copyfrom(struct inode *i, void *dest, unsigned long offset, unsigned long count)
 238 {
 239         struct buffer_head *bh;
 240         unsigned long avail, maxsize, res;
 241
 242         maxsize = romfs_maxsize(i->i_sb);
 243         if (offset >= maxsize || count > maxsize || offset+count>maxsize)
 244                 return -1;
 245
 246         bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
 247         if (!bh)
 248                 return -1;              /* error */
 249
 250         avail = ROMBSIZE - (offset & ROMBMASK);
 251         maxsize = min_t(unsigned long, count, avail);
 252         memcpy(dest, ((char *)bh->b_data) + (offset & ROMBMASK), maxsize);
 253         brelse(bh);
 254
 255         res = maxsize;                  /* all of it */
 256
 257         while (res < count) {
 258                 offset += maxsize;
 259                 dest += maxsize;
 260
 261                 bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
 262                 if (!bh)
 263                         return -1;
 264                 maxsize = min_t(unsigned long, count - res, ROMBSIZE);
 265                 memcpy(dest, bh->b_data, maxsize);
 266                 brelse(bh);
 267                 res += maxsize;
 268         }
 269         return res;
 270 }
 271
 272 static unsigned char romfs_dtype_table[] = {
 273         DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO
 274 };
 275
 276 static int
 277 romfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 278 {
 279         struct inode *i = filp->f_path.dentry->d_inode;
 280         struct romfs_inode ri;
 281         unsigned long offset, maxoff;
 282         int j, ino, nextfh;
 283         int stored = 0;
 284         char fsname[ROMFS_MAXFN];       /* XXX dynamic? */
 285
 286         lock_kernel();
 287
 288         maxoff = romfs_maxsize(i->i_sb);
 289
 290         offset = filp->f_pos;
 291         if (!offset) {
 292                 offset = i->i_ino & ROMFH_MASK;
 293                 if (romfs_copyfrom(i, &ri, offset, ROMFH_SIZE) <= 0)
 294                         goto out;
 295                 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 296         }
 297
 298         /* Not really failsafe, but we are read-only... */
 299         for(;;) {
 300                 if (!offset || offset >= maxoff) {
 301                         offset = maxoff;
 302                         filp->f_pos = offset;
 303                         goto out;
 304                 }
 305                 filp->f_pos = offset;
 306
 307                 /* Fetch inode info */
 308                 if (romfs_copyfrom(i, &ri, offset, ROMFH_SIZE) <= 0)
 309                         goto out;
 310
 311                 j = romfs_strnlen(i, offset+ROMFH_SIZE, sizeof(fsname)-1);
 312                 if (j < 0)
 313                         goto out;
 314
 315                 fsname[j]=0;
 316                 romfs_copyfrom(i, fsname, offset+ROMFH_SIZE, j);
 317
 318                 ino = offset;
 319                 nextfh = be32_to_cpu(ri.next);
 320                 if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
 321                         ino = be32_to_cpu(ri.spec);
 322                 if (filldir(dirent, fsname, j, offset, ino,
 323                             romfs_dtype_table[nextfh & ROMFH_TYPE]) < 0) {
 324                         goto out;
 325                 }
 326                 stored++;
 327                 offset = nextfh & ROMFH_MASK;
 328         }
 329 out:
 330         unlock_kernel();
 331         return stored;
 332 }
 333
 334 static struct dentry *
 335 romfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 336 {
 337         unsigned long offset, maxoff;
 338         int fslen, res;
 339         struct inode *inode;
 340         char fsname[ROMFS_MAXFN];       /* XXX dynamic? */
 341         struct romfs_inode ri;
 342         const char *name;               /* got from dentry */
 343         int len;
 344
 345         res = -EACCES;                  /* placeholder for "no data here" */
 346         offset = dir->i_ino & ROMFH_MASK;
 347         lock_kernel();
 348         if (romfs_copyfrom(dir, &ri, offset, ROMFH_SIZE) <= 0)
 349                 goto out;
 350
 351         maxoff = romfs_maxsize(dir->i_sb);
 352         offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 353
 354         /* OK, now find the file whose name is in "dentry" in the
 355          * directory specified by "dir".  */
 356
 357         name = dentry->d_name.name;
 358         len = dentry->d_name.len;
 359
 360         for(;;) {
 361                 if (!offset || offset >= maxoff)
 362                         goto out0;
 363                 if (romfs_copyfrom(dir, &ri, offset, ROMFH_SIZE) <= 0)
 364                         goto out;
 365
 366                 /* try to match the first 16 bytes of name */
 367                 fslen = romfs_strnlen(dir, offset+ROMFH_SIZE, ROMFH_SIZE);
 368                 if (len < ROMFH_SIZE) {
 369                         if (len == fslen) {
 370                                 /* both are shorter, and same size */
 371                                 romfs_copyfrom(dir, fsname, offset+ROMFH_SIZE, len+1);
 372                                 if (strncmp (name, fsname, len) == 0)
 373                                         break;
 374                         }
 375                 } else if (fslen >= ROMFH_SIZE) {
 376                         /* both are longer; XXX optimize max size */
 377                         fslen = romfs_strnlen(dir, offset+ROMFH_SIZE, sizeof(fsname)-1);
 378                         if (len == fslen) {
 379                                 romfs_copyfrom(dir, fsname, offset+ROMFH_SIZE, len+1);
 380                                 if (strncmp(name, fsname, len) == 0)
 381                                         break;
 382                         }
 383                 }
 384                 /* next entry */
 385                 offset = be32_to_cpu(ri.next) & ROMFH_MASK;
 386         }
 387
 388         /* Hard link handling */
 389         if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
 390                 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 391
 392         if ((inode = iget(dir->i_sb, offset)))
 393                 goto outi;
 394
 395         /*
 396          * it's a bit funky, _lookup needs to return an error code
 397          * (negative) or a NULL, both as a dentry.  ENOENT should not
 398          * be returned, instead we need to create a negative dentry by
 399          * d_add(dentry, NULL); and return 0 as no error.
 400          * (Although as I see, it only matters on writable file
 401          * systems).
 402          */
 403
 404 out0:   inode = NULL;
 405 outi:   res = 0;
 406         d_add (dentry, inode);
 407
 408 out:    unlock_kernel();
 409         return ERR_PTR(res);
 410 }
 411
 412 /*
 413  * Ok, we do readpage, to be able to execute programs.  Unfortunately,
 414  * we can't use bmap, since we may have looser alignments.
 415  */
 416
 417 static int
 418 romfs_readpage(struct file *file, struct page * page)
 419 {
 420         struct inode *inode = page->mapping->host;
 421         loff_t offset, avail, readlen;
 422         void *buf;
 423         int result = -EIO;
 424
 425         page_cache_get(page);
 426         lock_kernel();
 427         buf = kmap(page);
 428         if (!buf)
 429                 goto err_out;
 430
 431         /* 32 bit warning -- but not for us :) */
 432         offset = page_offset(page);
 433         if (offset < i_size_read(inode)) {
 434                 avail = inode->i_size-offset;
 435                 readlen = min_t(unsigned long, avail, PAGE_SIZE);
 436                 if (romfs_copyfrom(inode, buf, ROMFS_I(inode)->i_dataoffset+offset, readlen) == readlen) {
 437                         if (readlen < PAGE_SIZE) {
 438                                 memset(buf + readlen,0,PAGE_SIZE-readlen);
 439                         }
 440                         SetPageUptodate(page);
 441                         result = 0;
 442                 }
 443         }
 444         if (result) {
 445                 memset(buf, 0, PAGE_SIZE);
 446                 SetPageError(page);
 447         }
 448         flush_dcache_page(page);
 449
 450         unlock_page(page);
 451
 452         kunmap(page);
 453 err_out:
 454         page_cache_release(page);
 455         unlock_kernel();
 456
 457         return result;
 458 }
 459
 460 /* Mapping from our types to the kernel */
 461
 462 static const struct address_space_operations romfs_aops = {
 463         .readpage = romfs_readpage
 464 };
 465
 466 static const struct file_operations romfs_dir_operations = {
 467         .read           = generic_read_dir,
 468         .readdir        = romfs_readdir,
 469 };
 470
 471 static const struct inode_operations romfs_dir_inode_operations = {
 472         .lookup         = romfs_lookup,
 473 };
 474
 475 static mode_t romfs_modemap[] =
 476 {
 477         0, S_IFDIR+0644, S_IFREG+0644, S_IFLNK+0777,
 478         S_IFBLK+0600, S_IFCHR+0600, S_IFSOCK+0644, S_IFIFO+0644
 479 };
 480
 481 static void
 482 romfs_read_inode(struct inode *i)
 483 {
 484         int nextfh, ino;
 485         struct romfs_inode ri;
 486
 487         ino = i->i_ino & ROMFH_MASK;
 488         i->i_mode = 0;
 489
 490         /* Loop for finding the real hard link */
 491         for(;;) {
 492                 if (romfs_copyfrom(i, &ri, ino, ROMFH_SIZE) <= 0) {
 493                         printk("romfs: read error for inode 0x%x\n", ino);
 494                         return;
 495                 }
 496                 /* XXX: do romfs_checksum here too (with name) */
 497
 498                 nextfh = be32_to_cpu(ri.next);
 499                 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
 500                         break;
 501
 502                 ino = be32_to_cpu(ri.spec) & ROMFH_MASK;
 503         }
 504
 505         i->i_nlink = 1;         /* Hard to decide.. */
 506         i->i_size = be32_to_cpu(ri.size);
 507         i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0;
 508         i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0;
 509         i->i_uid = i->i_gid = 0;
 510
 511         /* Precalculate the data offset */
 512         ino = romfs_strnlen(i, ino+ROMFH_SIZE, ROMFS_MAXFN);
 513         if (ino >= 0)
 514                 ino = ((ROMFH_SIZE+ino+1+ROMFH_PAD)&ROMFH_MASK);
 515         else
 516                 ino = 0;
 517
 518         ROMFS_I(i)->i_metasize = ino;
 519         ROMFS_I(i)->i_dataoffset = ino+(i->i_ino&ROMFH_MASK);
 520
 521         /* Compute permissions */
 522         ino = romfs_modemap[nextfh & ROMFH_TYPE];
 523         /* only "normal" files have ops */
 524         switch (nextfh & ROMFH_TYPE) {
 525                 case 1:
 526                         i->i_size = ROMFS_I(i)->i_metasize;
 527                         i->i_op = &romfs_dir_inode_operations;
 528                         i->i_fop = &romfs_dir_operations;
 529                         if (nextfh & ROMFH_EXEC)
 530                                 ino |= S_IXUGO;
 531                         i->i_mode = ino;
 532                         break;
 533                 case 2:
 534                         i->i_fop = &generic_ro_fops;
 535                         i->i_data.a_ops = &romfs_aops;
 536                         if (nextfh & ROMFH_EXEC)
 537                                 ino |= S_IXUGO;
 538                         i->i_mode = ino;
 539                         break;
 540                 case 3:
 541                         i->i_op = &page_symlink_inode_operations;
 542                         i->i_data.a_ops = &romfs_aops;
 543                         i->i_mode = ino | S_IRWXUGO;
 544                         break;
 545                 default:
 546                         /* depending on MBZ for sock/fifos */
 547                         nextfh = be32_to_cpu(ri.spec);
 548                         init_special_inode(i, ino,
 549                                         MKDEV(nextfh>>16,nextfh&0xffff));
 550         }
 551 }
 552
 553 static struct kmem_cache * romfs_inode_cachep;
 554
 555 static struct inode *romfs_alloc_inode(struct super_block *sb)
 556 {
 557         struct romfs_inode_info *ei;
 558         ei = (struct romfs_inode_info *)kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL);
 559         if (!ei)
 560                 return NULL;
 561         return &ei->vfs_inode;
 562 }
 563
 564 static void romfs_destroy_inode(struct inode *inode)
 565 {
 566         kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
 567 }
 568
 569 static void init_once(void *foo, struct kmem_cache *cachep, unsigned long flags)
 570 {
 571         struct romfs_inode_info *ei = foo;
 572
 573         inode_init_once(&ei->vfs_inode);
 574 }
 575
 576 static int init_inodecache(void)
 577 {
 578         romfs_inode_cachep = kmem_cache_create("romfs_inode_cache",
 579                                              sizeof(struct romfs_inode_info),
 580                                              0, (SLAB_RECLAIM_ACCOUNT|
 581                                                 SLAB_MEM_SPREAD),
 582                                              init_once);
 583         if (romfs_inode_cachep == NULL)
 584                 return -ENOMEM;
 585         return 0;
 586 }
 587
 588 static void destroy_inodecache(void)
 589 {
 590         kmem_cache_destroy(romfs_inode_cachep);
 591 }
 592
 593 static int romfs_remount(struct super_block *sb, int *flags, char *data)
 594 {
 595         *flags |= MS_RDONLY;
 596         return 0;
 597 }
 598
 599 static const struct super_operations romfs_ops = {
 600         .alloc_inode    = romfs_alloc_inode,
 601         .destroy_inode  = romfs_destroy_inode,
 602         .read_inode     = romfs_read_inode,
 603         .statfs         = romfs_statfs,
 604         .remount_fs     = romfs_remount,
 605 };
 606
 607 static int romfs_get_sb(struct file_system_type *fs_type,
 608         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 609 {
 610         return get_sb_bdev(fs_type, flags, dev_name, data, romfs_fill_super,
 611                            mnt);
 612 }
 613
 614 static struct file_system_type romfs_fs_type = {
 615         .owner          = THIS_MODULE,
 616         .name           = "romfs",
 617         .get_sb         = romfs_get_sb,
 618         .kill_sb        = kill_block_super,
 619         .fs_flags       = FS_REQUIRES_DEV,
 620 };
 621
 622 static int __init init_romfs_fs(void)
 623 {
 624         int err = init_inodecache();
 625         if (err)
 626                 goto out1;
 627         err = register_filesystem(&romfs_fs_type);
 628         if (err)
 629                 goto out;
 630         return 0;
 631 out:
 632         destroy_inodecache();
 633 out1:
 634         return err;
 635 }
 636
 637 static void __exit exit_romfs_fs(void)
 638 {
 639         unregister_filesystem(&romfs_fs_type);
 640         destroy_inodecache();
 641 }
 642
 643 /* Yes, works even as a module... :) */
 644
 645 module_init(init_romfs_fs)
 646 module_exit(exit_romfs_fs)
 647 MODULE_LICENSE("GPL");