fs/romfs/super.c

   1 /* Block- or MTD-based romfs
   2  *
   3  * Copyright © 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * Derived from: ROMFS file system, Linux implementation
   7  *
   8  * Copyright © 1997-1999  Janos Farkas <chexum@shadow.banki.hu>
   9  *
  10  * Using parts of the minix filesystem
  11  * Copyright © 1991, 1992  Linus Torvalds
  12  *
  13  * and parts of the affs filesystem additionally
  14  * Copyright © 1993  Ray Burr
  15  * Copyright © 1996  Hans-Joachim Widmaier
  16  *
  17  * Changes
  18  *                                      Changed for 2.1.19 modules
  19  *      Jan 1997                        Initial release
  20  *      Jun 1997                        2.1.43+ changes
  21  *                                      Proper page locking in readpage
  22  *                                      Changed to work with 2.1.45+ fs
  23  *      Jul 1997                        Fixed follow_link
  24  *                      2.1.47
  25  *                                      lookup shouldn't return -ENOENT
  26  *                                      from Horst von Brand:
  27  *                                        fail on wrong checksum
  28  *                                        double unlock_super was possible
  29  *                                        correct namelen for statfs
  30  *                                      spotted by Bill Hawes:
  31  *                                        readlink shouldn't iput()
  32  *      Jun 1998        2.1.106         from Avery Pennarun: glibc scandir()
  33  *                                        exposed a problem in readdir
  34  *                      2.1.107         code-freeze spellchecker run
  35  *      Aug 1998                        2.1.118+ VFS changes
  36  *      Sep 1998        2.1.122         another VFS change (follow_link)
  37  *      Apr 1999        2.2.7           no more EBADF checking in
  38  *                                        lookup/readdir, use ERR_PTR
  39  *      Jun 1999        2.3.6           d_alloc_root use changed
  40  *                      2.3.9           clean up usage of ENOENT/negative
  41  *                                        dentries in lookup
  42  *                                      clean up page flags setting
  43  *                                        (error, uptodate, locking) in
  44  *                                        in readpage
  45  *                                      use init_special_inode for
  46  *                                        fifos/sockets (and streamline) in
  47  *                                        read_inode, fix _ops table order
  48  *      Aug 1999        2.3.16          __initfunc() => __init change
  49  *      Oct 1999        2.3.24          page->owner hack obsoleted
  50  *      Nov 1999        2.3.27          2.3.25+ page->offset => index change
  51  *
  52  *
  53  * This program is free software; you can redistribute it and/or
  54  * modify it under the terms of the GNU General Public Licence
  55  * as published by the Free Software Foundation; either version
  56  * 2 of the Licence, or (at your option) any later version.
  57  */
  58
  59 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  60
  61 #include <linux/module.h>
  62 #include <linux/string.h>
  63 #include <linux/fs.h>
  64 #include <linux/time.h>
  65 #include <linux/slab.h>
  66 #include <linux/init.h>
  67 #include <linux/blkdev.h>
  68 #include <linux/parser.h>
  69 #include <linux/mount.h>
  70 #include <linux/namei.h>
  71 #include <linux/statfs.h>
  72 #include <linux/mtd/super.h>
  73 #include <linux/ctype.h>
  74 #include <linux/highmem.h>
  75 #include <linux/pagemap.h>
  76 #include <linux/uaccess.h>
  77 #include "internal.h"
  78
  79 static struct kmem_cache *romfs_inode_cachep;
  80
  81 static const umode_t romfs_modemap[8] = {
  82         0,                      /* hard link */
  83         S_IFDIR  | 0644,        /* directory */
  84         S_IFREG  | 0644,        /* regular file */
  85         S_IFLNK  | 0777,        /* symlink */
  86         S_IFBLK  | 0600,        /* blockdev */
  87         S_IFCHR  | 0600,        /* chardev */
  88         S_IFSOCK | 0644,        /* socket */
  89         S_IFIFO  | 0644         /* FIFO */
  90 };
  91
  92 static const unsigned char romfs_dtype_table[] = {
  93         DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO
  94 };
  95
  96 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos);
  97
  98 /*
  99  * read a page worth of data from the image
 100  */
 101 static int romfs_readpage(struct file *file, struct page *page)
 102 {
 103         struct inode *inode = page->mapping->host;
 104         loff_t offset, size;
 105         unsigned long fillsize, pos;
 106         void *buf;
 107         int ret;
 108
 109         buf = kmap(page);
 110         if (!buf)
 111                 return -ENOMEM;
 112
 113         /* 32 bit warning -- but not for us :) */
 114         offset = page_offset(page);
 115         size = i_size_read(inode);
 116         fillsize = 0;
 117         ret = 0;
 118         if (offset < size) {
 119                 size -= offset;
 120                 fillsize = size > PAGE_SIZE ? PAGE_SIZE : size;
 121
 122                 pos = ROMFS_I(inode)->i_dataoffset + offset;
 123
 124                 ret = romfs_dev_read(inode->i_sb, pos, buf, fillsize);
 125                 if (ret < 0) {
 126                         SetPageError(page);
 127                         fillsize = 0;
 128                         ret = -EIO;
 129                 }
 130         }
 131
 132         if (fillsize < PAGE_SIZE)
 133                 memset(buf + fillsize, 0, PAGE_SIZE - fillsize);
 134         if (ret == 0)
 135                 SetPageUptodate(page);
 136
 137         flush_dcache_page(page);
 138         kunmap(page);
 139         unlock_page(page);
 140         return ret;
 141 }
 142
 143 static const struct address_space_operations romfs_aops = {
 144         .readpage       = romfs_readpage
 145 };
 146
 147 /*
 148  * read the entries from a directory
 149  */
 150 static int romfs_readdir(struct file *file, struct dir_context *ctx)
 151 {
 152         struct inode *i = file_inode(file);
 153         struct romfs_inode ri;
 154         unsigned long offset, maxoff;
 155         int j, ino, nextfh;
 156         char fsname[ROMFS_MAXFN];       /* XXX dynamic? */
 157         int ret;
 158
 159         maxoff = romfs_maxsize(i->i_sb);
 160
 161         offset = ctx->pos;
 162         if (!offset) {
 163                 offset = i->i_ino & ROMFH_MASK;
 164                 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
 165                 if (ret < 0)
 166                         goto out;
 167                 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 168         }
 169
 170         /* Not really failsafe, but we are read-only... */
 171         for (;;) {
 172                 if (!offset || offset >= maxoff) {
 173                         offset = maxoff;
 174                         ctx->pos = offset;
 175                         goto out;
 176                 }
 177                 ctx->pos = offset;
 178
 179                 /* Fetch inode info */
 180                 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
 181                 if (ret < 0)
 182                         goto out;
 183
 184                 j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE,
 185                                       sizeof(fsname) - 1);
 186                 if (j < 0)
 187                         goto out;
 188
 189                 ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j);
 190                 if (ret < 0)
 191                         goto out;
 192                 fsname[j] = '\0';
 193
 194                 ino = offset;
 195                 nextfh = be32_to_cpu(ri.next);
 196                 if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
 197                         ino = be32_to_cpu(ri.spec);
 198                 if (!dir_emit(ctx, fsname, j, ino,
 199                             romfs_dtype_table[nextfh & ROMFH_TYPE]))
 200                         goto out;
 201
 202                 offset = nextfh & ROMFH_MASK;
 203         }
 204 out:
 205         return 0;
 206 }
 207
 208 /*
 209  * look up an entry in a directory
 210  */
 211 static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,
 212                                    unsigned int flags)
 213 {
 214         unsigned long offset, maxoff;
 215         struct inode *inode;
 216         struct romfs_inode ri;
 217         const char *name;               /* got from dentry */
 218         int len, ret;
 219
 220         offset = dir->i_ino & ROMFH_MASK;
 221         ret = romfs_dev_read(dir->i_sb, offset, &ri, ROMFH_SIZE);
 222         if (ret < 0)
 223                 goto error;
 224
 225         /* search all the file entries in the list starting from the one
 226          * pointed to by the directory's special data */
 227         maxoff = romfs_maxsize(dir->i_sb);
 228         offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 229
 230         name = dentry->d_name.name;
 231         len = dentry->d_name.len;
 232
 233         for (;;) {
 234                 if (!offset || offset >= maxoff)
 235                         goto out0;
 236
 237                 ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri));
 238                 if (ret < 0)
 239                         goto error;
 240
 241                 /* try to match the first 16 bytes of name */
 242                 ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name,
 243                                        len);
 244                 if (ret < 0)
 245                         goto error;
 246                 if (ret == 1)
 247                         break;
 248
 249                 /* next entry */
 250                 offset = be32_to_cpu(ri.next) & ROMFH_MASK;
 251         }
 252
 253         /* Hard link handling */
 254         if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
 255                 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 256
 257         inode = romfs_iget(dir->i_sb, offset);
 258         if (IS_ERR(inode)) {
 259                 ret = PTR_ERR(inode);
 260                 goto error;
 261         }
 262         goto outi;
 263
 264         /*
 265          * it's a bit funky, _lookup needs to return an error code
 266          * (negative) or a NULL, both as a dentry.  ENOENT should not
 267          * be returned, instead we need to create a negative dentry by
 268          * d_add(dentry, NULL); and return 0 as no error.
 269          * (Although as I see, it only matters on writable file
 270          * systems).
 271          */
 272 out0:
 273         inode = NULL;
 274 outi:
 275         d_add(dentry, inode);
 276         ret = 0;
 277 error:
 278         return ERR_PTR(ret);
 279 }
 280
 281 static const struct file_operations romfs_dir_operations = {
 282         .read           = generic_read_dir,
 283         .iterate_shared = romfs_readdir,
 284         .llseek         = generic_file_llseek,
 285 };
 286
 287 static const struct inode_operations romfs_dir_inode_operations = {
 288         .lookup         = romfs_lookup,
 289 };
 290
 291 /*
 292  * get a romfs inode based on its position in the image (which doubles as the
 293  * inode number)
 294  */
 295 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos)
 296 {
 297         struct romfs_inode_info *inode;
 298         struct romfs_inode ri;
 299         struct inode *i;
 300         unsigned long nlen;
 301         unsigned nextfh;
 302         int ret;
 303         umode_t mode;
 304
 305         /* we might have to traverse a chain of "hard link" file entries to get
 306          * to the actual file */
 307         for (;;) {
 308                 ret = romfs_dev_read(sb, pos, &ri, sizeof(ri));
 309                 if (ret < 0)
 310                         goto error;
 311
 312                 /* XXX: do romfs_checksum here too (with name) */
 313
 314                 nextfh = be32_to_cpu(ri.next);
 315                 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
 316                         break;
 317
 318                 pos = be32_to_cpu(ri.spec) & ROMFH_MASK;
 319         }
 320
 321         /* determine the length of the filename */
 322         nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN);
 323         if (IS_ERR_VALUE(nlen))
 324                 goto eio;
 325
 326         /* get an inode for this image position */
 327         i = iget_locked(sb, pos);
 328         if (!i)
 329                 return ERR_PTR(-ENOMEM);
 330
 331         if (!(i->i_state & I_NEW))
 332                 return i;
 333
 334         /* precalculate the data offset */
 335         inode = ROMFS_I(i);
 336         inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK;
 337         inode->i_dataoffset = pos + inode->i_metasize;
 338
 339         set_nlink(i, 1);                /* Hard to decide.. */
 340         i->i_size = be32_to_cpu(ri.size);
 341         i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0;
 342         i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0;
 343
 344         /* set up mode and ops */
 345         mode = romfs_modemap[nextfh & ROMFH_TYPE];
 346
 347         switch (nextfh & ROMFH_TYPE) {
 348         case ROMFH_DIR:
 349                 i->i_size = ROMFS_I(i)->i_metasize;
 350                 i->i_op = &romfs_dir_inode_operations;
 351                 i->i_fop = &romfs_dir_operations;
 352                 if (nextfh & ROMFH_EXEC)
 353                         mode |= S_IXUGO;
 354                 break;
 355         case ROMFH_REG:
 356                 i->i_fop = &romfs_ro_fops;
 357                 i->i_data.a_ops = &romfs_aops;
 358                 if (nextfh & ROMFH_EXEC)
 359                         mode |= S_IXUGO;
 360                 break;
 361         case ROMFH_SYM:
 362                 i->i_op = &page_symlink_inode_operations;
 363                 inode_nohighmem(i);
 364                 i->i_data.a_ops = &romfs_aops;
 365                 mode |= S_IRWXUGO;
 366                 break;
 367         default:
 368                 /* depending on MBZ for sock/fifos */
 369                 nextfh = be32_to_cpu(ri.spec);
 370                 init_special_inode(i, mode, MKDEV(nextfh >> 16,
 371                                                   nextfh & 0xffff));
 372                 break;
 373         }
 374
 375         i->i_mode = mode;
 376
 377         unlock_new_inode(i);
 378         return i;
 379
 380 eio:
 381         ret = -EIO;
 382 error:
 383         pr_err("read error for inode 0x%lx\n", pos);
 384         return ERR_PTR(ret);
 385 }
 386
 387 /*
 388  * allocate a new inode
 389  */
 390 static struct inode *romfs_alloc_inode(struct super_block *sb)
 391 {
 392         struct romfs_inode_info *inode;
 393
 394         inode = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL);
 395         return inode ? &inode->vfs_inode : NULL;
 396 }
 397
 398 /*
 399  * return a spent inode to the slab cache
 400  */
 401 static void romfs_i_callback(struct rcu_head *head)
 402 {
 403         struct inode *inode = container_of(head, struct inode, i_rcu);
 404
 405         kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
 406 }
 407
 408 static void romfs_destroy_inode(struct inode *inode)
 409 {
 410         call_rcu(&inode->i_rcu, romfs_i_callback);
 411 }
 412
 413 /*
 414  * get filesystem statistics
 415  */
 416 static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 417 {
 418         struct super_block *sb = dentry->d_sb;
 419         u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
 420
 421         buf->f_type = ROMFS_MAGIC;
 422         buf->f_namelen = ROMFS_MAXFN;
 423         buf->f_bsize = ROMBSIZE;
 424         buf->f_bfree = buf->f_bavail = buf->f_ffree;
 425         buf->f_blocks =
 426                 (romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS;
 427         buf->f_fsid.val[0] = (u32)id;
 428         buf->f_fsid.val[1] = (u32)(id >> 32);
 429         return 0;
 430 }
 431
 432 /*
 433  * remounting must involve read-only
 434  */
 435 static int romfs_remount(struct super_block *sb, int *flags, char *data)
 436 {
 437         sync_filesystem(sb);
 438         *flags |= MS_RDONLY;
 439         return 0;
 440 }
 441
 442 static const struct super_operations romfs_super_ops = {
 443         .alloc_inode    = romfs_alloc_inode,
 444         .destroy_inode  = romfs_destroy_inode,
 445         .statfs         = romfs_statfs,
 446         .remount_fs     = romfs_remount,
 447 };
 448
 449 /*
 450  * checksum check on part of a romfs filesystem
 451  */
 452 static __u32 romfs_checksum(const void *data, int size)
 453 {
 454         const __be32 *ptr = data;
 455         __u32 sum;
 456
 457         sum = 0;
 458         size >>= 2;
 459         while (size > 0) {
 460                 sum += be32_to_cpu(*ptr++);
 461                 size--;
 462         }
 463         return sum;
 464 }
 465
 466 /*
 467  * fill in the superblock
 468  */
 469 static int romfs_fill_super(struct super_block *sb, void *data, int silent)
 470 {
 471         struct romfs_super_block *rsb;
 472         struct inode *root;
 473         unsigned long pos, img_size;
 474         const char *storage;
 475         size_t len;
 476         int ret;
 477
 478 #ifdef CONFIG_BLOCK
 479         if (!sb->s_mtd) {
 480                 sb_set_blocksize(sb, ROMBSIZE);
 481         } else {
 482                 sb->s_blocksize = ROMBSIZE;
 483                 sb->s_blocksize_bits = blksize_bits(ROMBSIZE);
 484         }
 485 #endif
 486
 487         sb->s_maxbytes = 0xFFFFFFFF;
 488         sb->s_magic = ROMFS_MAGIC;
 489         sb->s_flags |= MS_RDONLY | MS_NOATIME;
 490         sb->s_op = &romfs_super_ops;
 491
 492         /* read the image superblock and check it */
 493         rsb = kmalloc(512, GFP_KERNEL);
 494         if (!rsb)
 495                 return -ENOMEM;
 496
 497         sb->s_fs_info = (void *) 512;
 498         ret = romfs_dev_read(sb, 0, rsb, 512);
 499         if (ret < 0)
 500                 goto error_rsb;
 501
 502         img_size = be32_to_cpu(rsb->size);
 503
 504         if (sb->s_mtd && img_size > sb->s_mtd->size)
 505                 goto error_rsb_inval;
 506
 507         sb->s_fs_info = (void *) img_size;
 508
 509         if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 ||
 510             img_size < ROMFH_SIZE) {
 511                 if (!silent)
 512                         pr_warn("VFS: Can't find a romfs filesystem on dev %s.\n",
 513                                sb->s_id);
 514                 goto error_rsb_inval;
 515         }
 516
 517         if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) {
 518                 pr_err("bad initial checksum on dev %s.\n", sb->s_id);
 519                 goto error_rsb_inval;
 520         }
 521
 522         storage = sb->s_mtd ? "MTD" : "the block layer";
 523
 524         len = strnlen(rsb->name, ROMFS_MAXFN);
 525         if (!silent)
 526                 pr_notice("Mounting image '%*.*s' through %s\n",
 527                           (unsigned) len, (unsigned) len, rsb->name, storage);
 528
 529         kfree(rsb);
 530         rsb = NULL;
 531
 532         /* find the root directory */
 533         pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;
 534
 535         root = romfs_iget(sb, pos);
 536         if (IS_ERR(root))
 537                 return PTR_ERR(root);
 538
 539         sb->s_root = d_make_root(root);
 540         if (!sb->s_root)
 541                 return -ENOMEM;
 542
 543         return 0;
 544
 545 error_rsb_inval:
 546         ret = -EINVAL;
 547 error_rsb:
 548         kfree(rsb);
 549         return ret;
 550 }
 551
 552 /*
 553  * get a superblock for mounting
 554  */
 555 static struct dentry *romfs_mount(struct file_system_type *fs_type,
 556                         int flags, const char *dev_name,
 557                         void *data)
 558 {
 559         struct dentry *ret = ERR_PTR(-EINVAL);
 560
 561 #ifdef CONFIG_ROMFS_ON_MTD
 562         ret = mount_mtd(fs_type, flags, dev_name, data, romfs_fill_super);
 563 #endif
 564 #ifdef CONFIG_ROMFS_ON_BLOCK
 565         if (ret == ERR_PTR(-EINVAL))
 566                 ret = mount_bdev(fs_type, flags, dev_name, data,
 567                                   romfs_fill_super);
 568 #endif
 569         return ret;
 570 }
 571
 572 /*
 573  * destroy a romfs superblock in the appropriate manner
 574  */
 575 static void romfs_kill_sb(struct super_block *sb)
 576 {
 577 #ifdef CONFIG_ROMFS_ON_MTD
 578         if (sb->s_mtd) {
 579                 kill_mtd_super(sb);
 580                 return;
 581         }
 582 #endif
 583 #ifdef CONFIG_ROMFS_ON_BLOCK
 584         if (sb->s_bdev) {
 585                 kill_block_super(sb);
 586                 return;
 587         }
 588 #endif
 589 }
 590
 591 static struct file_system_type romfs_fs_type = {
 592         .owner          = THIS_MODULE,
 593         .name           = "romfs",
 594         .mount          = romfs_mount,
 595         .kill_sb        = romfs_kill_sb,
 596         .fs_flags       = FS_REQUIRES_DEV,
 597 };
 598 MODULE_ALIAS_FS("romfs");
 599
 600 /*
 601  * inode storage initialiser
 602  */
 603 static void romfs_i_init_once(void *_inode)
 604 {
 605         struct romfs_inode_info *inode = _inode;
 606
 607         inode_init_once(&inode->vfs_inode);
 608 }
 609
 610 /*
 611  * romfs module initialisation
 612  */
 613 static int __init init_romfs_fs(void)
 614 {
 615         int ret;
 616
 617         pr_info("ROMFS MTD (C) 2007 Red Hat, Inc.\n");
 618
 619         romfs_inode_cachep =
 620                 kmem_cache_create("romfs_i",
 621                                   sizeof(struct romfs_inode_info), 0,
 622                                   SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD |
 623                                   SLAB_ACCOUNT, romfs_i_init_once);
 624
 625         if (!romfs_inode_cachep) {
 626                 pr_err("Failed to initialise inode cache\n");
 627                 return -ENOMEM;
 628         }
 629         ret = register_filesystem(&romfs_fs_type);
 630         if (ret) {
 631                 pr_err("Failed to register filesystem\n");
 632                 goto error_register;
 633         }
 634         return 0;
 635
 636 error_register:
 637         kmem_cache_destroy(romfs_inode_cachep);
 638         return ret;
 639 }
 640
 641 /*
 642  * romfs module removal
 643  */
 644 static void __exit exit_romfs_fs(void)
 645 {
 646         unregister_filesystem(&romfs_fs_type);
 647         /*
 648          * Make sure all delayed rcu free inodes are flushed before we
 649          * destroy cache.
 650          */
 651         rcu_barrier();
 652         kmem_cache_destroy(romfs_inode_cachep);
 653 }
 654
 655 module_init(init_romfs_fs);
 656 module_exit(exit_romfs_fs);
 657
 658 MODULE_DESCRIPTION("Direct-MTD Capable RomFS");
 659 MODULE_AUTHOR("Red Hat, Inc.");
 660 MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */