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 static struct inode *romfs_iget(struct super_block *, unsigned long);
  88
  89 /* instead of private superblock data */
  90 static inline unsigned long romfs_maxsize(struct super_block *sb)
  91 {
  92         return (unsigned long)sb->s_fs_info;
  93 }
  94
  95 static inline struct romfs_inode_info *ROMFS_I(struct inode *inode)
  96 {
  97         return container_of(inode, struct romfs_inode_info, vfs_inode);
  98 }
  99
 100 static __u32
 101 romfs_checksum(void *data, int size)
 102 {
 103         __u32 sum;
 104         __be32 *ptr;
 105
 106         sum = 0; ptr = data;
 107         size>>=2;
 108         while (size>0) {
 109                 sum += be32_to_cpu(*ptr++);
 110                 size--;
 111         }
 112         return sum;
 113 }
 114
 115 static const struct super_operations romfs_ops;
 116
 117 static int romfs_fill_super(struct super_block *s, void *data, int silent)
 118 {
 119         struct buffer_head *bh;
 120         struct romfs_super_block *rsb;
 121         struct inode *root;
 122         int sz, ret = -EINVAL;
 123
 124         /* I would parse the options here, but there are none.. :) */
 125
 126         sb_set_blocksize(s, ROMBSIZE);
 127         s->s_maxbytes = 0xFFFFFFFF;
 128
 129         bh = sb_bread(s, 0);
 130         if (!bh) {
 131                 /* XXX merge with other printk? */
 132                 printk ("romfs: unable to read superblock\n");
 133                 goto outnobh;
 134         }
 135
 136         rsb = (struct romfs_super_block *)bh->b_data;
 137         sz = be32_to_cpu(rsb->size);
 138         if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1
 139            || sz < ROMFH_SIZE) {
 140                 if (!silent)
 141                         printk ("VFS: Can't find a romfs filesystem on dev "
 142                                 "%s.\n", s->s_id);
 143                 goto out;
 144         }
 145         if (romfs_checksum(rsb, min_t(int, sz, 512))) {
 146                 printk ("romfs: bad initial checksum on dev "
 147                         "%s.\n", s->s_id);
 148                 goto out;
 149         }
 150
 151         s->s_magic = ROMFS_MAGIC;
 152         s->s_fs_info = (void *)(long)sz;
 153
 154         s->s_flags |= MS_RDONLY;
 155
 156         /* Find the start of the fs */
 157         sz = (ROMFH_SIZE +
 158               strnlen(rsb->name, ROMFS_MAXFN) + 1 + ROMFH_PAD)
 159              & ROMFH_MASK;
 160
 161         s->s_op = &romfs_ops;
 162         root = romfs_iget(s, sz);
 163         if (IS_ERR(root)) {
 164                 ret = PTR_ERR(root);
 165                 goto out;
 166         }
 167
 168         ret = -ENOMEM;
 169         s->s_root = d_alloc_root(root);
 170         if (!s->s_root)
 171                 goto outiput;
 172
 173         brelse(bh);
 174         return 0;
 175
 176 outiput:
 177         iput(root);
 178 out:
 179         brelse(bh);
 180 outnobh:
 181         return ret;
 182 }
 183
 184 /* That's simple too. */
 185
 186 static int
 187 romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 188 {
 189         buf->f_type = ROMFS_MAGIC;
 190         buf->f_bsize = ROMBSIZE;
 191         buf->f_bfree = buf->f_bavail = buf->f_ffree;
 192         buf->f_blocks = (romfs_maxsize(dentry->d_sb)+ROMBSIZE-1)>>ROMBSBITS;
 193         buf->f_namelen = ROMFS_MAXFN;
 194         return 0;
 195 }
 196
 197 /* some helper routines */
 198
 199 static int
 200 romfs_strnlen(struct inode *i, unsigned long offset, unsigned long count)
 201 {
 202         struct buffer_head *bh;
 203         unsigned long avail, maxsize, res;
 204
 205         maxsize = romfs_maxsize(i->i_sb);
 206         if (offset >= maxsize)
 207                 return -1;
 208
 209         /* strnlen is almost always valid */
 210         if (count > maxsize || offset+count > maxsize)
 211                 count = maxsize-offset;
 212
 213         bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
 214         if (!bh)
 215                 return -1;              /* error */
 216
 217         avail = ROMBSIZE - (offset & ROMBMASK);
 218         maxsize = min_t(unsigned long, count, avail);
 219         res = strnlen(((char *)bh->b_data)+(offset&ROMBMASK), maxsize);
 220         brelse(bh);
 221
 222         if (res < maxsize)
 223                 return res;             /* found all of it */
 224
 225         while (res < count) {
 226                 offset += maxsize;
 227
 228                 bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
 229                 if (!bh)
 230                         return -1;
 231                 maxsize = min_t(unsigned long, count - res, ROMBSIZE);
 232                 avail = strnlen(bh->b_data, maxsize);
 233                 res += avail;
 234                 brelse(bh);
 235                 if (avail < maxsize)
 236                         return res;
 237         }
 238         return res;
 239 }
 240
 241 static int
 242 romfs_copyfrom(struct inode *i, void *dest, unsigned long offset, unsigned long count)
 243 {
 244         struct buffer_head *bh;
 245         unsigned long avail, maxsize, res;
 246
 247         maxsize = romfs_maxsize(i->i_sb);
 248         if (offset >= maxsize || count > maxsize || offset+count>maxsize)
 249                 return -1;
 250
 251         bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
 252         if (!bh)
 253                 return -1;              /* error */
 254
 255         avail = ROMBSIZE - (offset & ROMBMASK);
 256         maxsize = min_t(unsigned long, count, avail);
 257         memcpy(dest, ((char *)bh->b_data) + (offset & ROMBMASK), maxsize);
 258         brelse(bh);
 259
 260         res = maxsize;                  /* all of it */
 261
 262         while (res < count) {
 263                 offset += maxsize;
 264                 dest += maxsize;
 265
 266                 bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
 267                 if (!bh)
 268                         return -1;
 269                 maxsize = min_t(unsigned long, count - res, ROMBSIZE);
 270                 memcpy(dest, bh->b_data, maxsize);
 271                 brelse(bh);
 272                 res += maxsize;
 273         }
 274         return res;
 275 }
 276
 277 static unsigned char romfs_dtype_table[] = {
 278         DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO
 279 };
 280
 281 static int
 282 romfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 283 {
 284         struct inode *i = filp->f_path.dentry->d_inode;
 285         struct romfs_inode ri;
 286         unsigned long offset, maxoff;
 287         int j, ino, nextfh;
 288         int stored = 0;
 289         char fsname[ROMFS_MAXFN];       /* XXX dynamic? */
 290
 291         lock_kernel();
 292
 293         maxoff = romfs_maxsize(i->i_sb);
 294
 295         offset = filp->f_pos;
 296         if (!offset) {
 297                 offset = i->i_ino & ROMFH_MASK;
 298                 if (romfs_copyfrom(i, &ri, offset, ROMFH_SIZE) <= 0)
 299                         goto out;
 300                 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 301         }
 302
 303         /* Not really failsafe, but we are read-only... */
 304         for(;;) {
 305                 if (!offset || offset >= maxoff) {
 306                         offset = maxoff;
 307                         filp->f_pos = offset;
 308                         goto out;
 309                 }
 310                 filp->f_pos = offset;
 311
 312                 /* Fetch inode info */
 313                 if (romfs_copyfrom(i, &ri, offset, ROMFH_SIZE) <= 0)
 314                         goto out;
 315
 316                 j = romfs_strnlen(i, offset+ROMFH_SIZE, sizeof(fsname)-1);
 317                 if (j < 0)
 318                         goto out;
 319
 320                 fsname[j]=0;
 321                 romfs_copyfrom(i, fsname, offset+ROMFH_SIZE, j);
 322
 323                 ino = offset;
 324                 nextfh = be32_to_cpu(ri.next);
 325                 if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
 326                         ino = be32_to_cpu(ri.spec);
 327                 if (filldir(dirent, fsname, j, offset, ino,
 328                             romfs_dtype_table[nextfh & ROMFH_TYPE]) < 0) {
 329                         goto out;
 330                 }
 331                 stored++;
 332                 offset = nextfh & ROMFH_MASK;
 333         }
 334 out:
 335         unlock_kernel();
 336         return stored;
 337 }
 338
 339 static struct dentry *
 340 romfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 341 {
 342         unsigned long offset, maxoff;
 343         long res;
 344         int fslen;
 345         struct inode *inode = NULL;
 346         char fsname[ROMFS_MAXFN];       /* XXX dynamic? */
 347         struct romfs_inode ri;
 348         const char *name;               /* got from dentry */
 349         int len;
 350
 351         res = -EACCES;                  /* placeholder for "no data here" */
 352         offset = dir->i_ino & ROMFH_MASK;
 353         lock_kernel();
 354         if (romfs_copyfrom(dir, &ri, offset, ROMFH_SIZE) <= 0)
 355                 goto error;
 356
 357         maxoff = romfs_maxsize(dir->i_sb);
 358         offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 359
 360         /* OK, now find the file whose name is in "dentry" in the
 361          * directory specified by "dir".  */
 362
 363         name = dentry->d_name.name;
 364         len = dentry->d_name.len;
 365
 366         for(;;) {
 367                 if (!offset || offset >= maxoff)
 368                         goto success; /* negative success */
 369                 if (romfs_copyfrom(dir, &ri, offset, ROMFH_SIZE) <= 0)
 370                         goto error;
 371
 372                 /* try to match the first 16 bytes of name */
 373                 fslen = romfs_strnlen(dir, offset+ROMFH_SIZE, ROMFH_SIZE);
 374                 if (len < ROMFH_SIZE) {
 375                         if (len == fslen) {
 376                                 /* both are shorter, and same size */
 377                                 romfs_copyfrom(dir, fsname, offset+ROMFH_SIZE, len+1);
 378                                 if (strncmp (name, fsname, len) == 0)
 379                                         break;
 380                         }
 381                 } else if (fslen >= ROMFH_SIZE) {
 382                         /* both are longer; XXX optimize max size */
 383                         fslen = romfs_strnlen(dir, offset+ROMFH_SIZE, sizeof(fsname)-1);
 384                         if (len == fslen) {
 385                                 romfs_copyfrom(dir, fsname, offset+ROMFH_SIZE, len+1);
 386                                 if (strncmp(name, fsname, len) == 0)
 387                                         break;
 388                         }
 389                 }
 390                 /* next entry */
 391                 offset = be32_to_cpu(ri.next) & ROMFH_MASK;
 392         }
 393
 394         /* Hard link handling */
 395         if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
 396                 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 397
 398         inode = romfs_iget(dir->i_sb, offset);
 399         if (IS_ERR(inode)) {
 400                 res = PTR_ERR(inode);
 401                 goto error;
 402         }
 403
 404 success:
 405         d_add(dentry, inode);
 406         res = 0;
 407 error:
 408         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 struct inode *
 482 romfs_iget(struct super_block *sb, unsigned long ino)
 483 {
 484         int nextfh;
 485         struct romfs_inode ri;
 486         struct inode *i;
 487
 488         ino &= ROMFH_MASK;
 489         i = iget_locked(sb, ino);
 490         if (!i)
 491                 return ERR_PTR(-ENOMEM);
 492         if (!(i->i_state & I_NEW))
 493                 return i;
 494
 495         i->i_mode = 0;
 496
 497         /* Loop for finding the real hard link */
 498         for(;;) {
 499                 if (romfs_copyfrom(i, &ri, ino, ROMFH_SIZE) <= 0) {
 500                         printk(KERN_ERR "romfs: read error for inode 0x%lx\n",
 501                                 ino);
 502                         iget_failed(i);
 503                         return ERR_PTR(-EIO);
 504                 }
 505                 /* XXX: do romfs_checksum here too (with name) */
 506
 507                 nextfh = be32_to_cpu(ri.next);
 508                 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
 509                         break;
 510
 511                 ino = be32_to_cpu(ri.spec) & ROMFH_MASK;
 512         }
 513
 514         i->i_nlink = 1;         /* Hard to decide.. */
 515         i->i_size = be32_to_cpu(ri.size);
 516         i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0;
 517         i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0;
 518         i->i_uid = i->i_gid = 0;
 519
 520         /* Precalculate the data offset */
 521         ino = romfs_strnlen(i, ino+ROMFH_SIZE, ROMFS_MAXFN);
 522         if (ino >= 0)
 523                 ino = ((ROMFH_SIZE+ino+1+ROMFH_PAD)&ROMFH_MASK);
 524         else
 525                 ino = 0;
 526
 527         ROMFS_I(i)->i_metasize = ino;
 528         ROMFS_I(i)->i_dataoffset = ino+(i->i_ino&ROMFH_MASK);
 529
 530         /* Compute permissions */
 531         ino = romfs_modemap[nextfh & ROMFH_TYPE];
 532         /* only "normal" files have ops */
 533         switch (nextfh & ROMFH_TYPE) {
 534                 case 1:
 535                         i->i_size = ROMFS_I(i)->i_metasize;
 536                         i->i_op = &romfs_dir_inode_operations;
 537                         i->i_fop = &romfs_dir_operations;
 538                         if (nextfh & ROMFH_EXEC)
 539                                 ino |= S_IXUGO;
 540                         i->i_mode = ino;
 541                         break;
 542                 case 2:
 543                         i->i_fop = &generic_ro_fops;
 544                         i->i_data.a_ops = &romfs_aops;
 545                         if (nextfh & ROMFH_EXEC)
 546                                 ino |= S_IXUGO;
 547                         i->i_mode = ino;
 548                         break;
 549                 case 3:
 550                         i->i_op = &page_symlink_inode_operations;
 551                         i->i_data.a_ops = &romfs_aops;
 552                         i->i_mode = ino | S_IRWXUGO;
 553                         break;
 554                 default:
 555                         /* depending on MBZ for sock/fifos */
 556                         nextfh = be32_to_cpu(ri.spec);
 557                         init_special_inode(i, ino,
 558                                         MKDEV(nextfh>>16,nextfh&0xffff));
 559         }
 560         unlock_new_inode(i);
 561         return i;
 562 }
 563
 564 static struct kmem_cache * romfs_inode_cachep;
 565
 566 static struct inode *romfs_alloc_inode(struct super_block *sb)
 567 {
 568         struct romfs_inode_info *ei;
 569         ei = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL);
 570         if (!ei)
 571                 return NULL;
 572         return &ei->vfs_inode;
 573 }
 574
 575 static void romfs_destroy_inode(struct inode *inode)
 576 {
 577         kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
 578 }
 579
 580 static void init_once(struct kmem_cache *cachep, void *foo)
 581 {
 582         struct romfs_inode_info *ei = foo;
 583
 584         inode_init_once(&ei->vfs_inode);
 585 }
 586
 587 static int init_inodecache(void)
 588 {
 589         romfs_inode_cachep = kmem_cache_create("romfs_inode_cache",
 590                                              sizeof(struct romfs_inode_info),
 591                                              0, (SLAB_RECLAIM_ACCOUNT|
 592                                                 SLAB_MEM_SPREAD),
 593                                              init_once);
 594         if (romfs_inode_cachep == NULL)
 595                 return -ENOMEM;
 596         return 0;
 597 }
 598
 599 static void destroy_inodecache(void)
 600 {
 601         kmem_cache_destroy(romfs_inode_cachep);
 602 }
 603
 604 static int romfs_remount(struct super_block *sb, int *flags, char *data)
 605 {
 606         *flags |= MS_RDONLY;
 607         return 0;
 608 }
 609
 610 static const struct super_operations romfs_ops = {
 611         .alloc_inode    = romfs_alloc_inode,
 612         .destroy_inode  = romfs_destroy_inode,
 613         .statfs         = romfs_statfs,
 614         .remount_fs     = romfs_remount,
 615 };
 616
 617 static int romfs_get_sb(struct file_system_type *fs_type,
 618         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 619 {
 620         return get_sb_bdev(fs_type, flags, dev_name, data, romfs_fill_super,
 621                            mnt);
 622 }
 623
 624 static struct file_system_type romfs_fs_type = {
 625         .owner          = THIS_MODULE,
 626         .name           = "romfs",
 627         .get_sb         = romfs_get_sb,
 628         .kill_sb        = kill_block_super,
 629         .fs_flags       = FS_REQUIRES_DEV,
 630 };
 631
 632 static int __init init_romfs_fs(void)
 633 {
 634         int err = init_inodecache();
 635         if (err)
 636                 goto out1;
 637         err = register_filesystem(&romfs_fs_type);
 638         if (err)
 639                 goto out;
 640         return 0;
 641 out:
 642         destroy_inodecache();
 643 out1:
 644         return err;
 645 }
 646
 647 static void __exit exit_romfs_fs(void)
 648 {
 649         unregister_filesystem(&romfs_fs_type);
 650         destroy_inodecache();
 651 }
 652
 653 /* Yes, works even as a module... :) */
 654
 655 module_init(init_romfs_fs)
 656 module_exit(exit_romfs_fs)
 657 MODULE_LICENSE("GPL");