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        = romfs_readdir,
 284         .llseek         = default_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                 i->i_data.a_ops = &romfs_aops;
 364                 mode |= S_IRWXUGO;
 365                 break;
 366         default:
 367                 /* depending on MBZ for sock/fifos */
 368                 nextfh = be32_to_cpu(ri.spec);
 369                 init_special_inode(i, mode, MKDEV(nextfh >> 16,
 370                                                   nextfh & 0xffff));
 371                 break;
 372         }
 373
 374         i->i_mode = mode;
 375
 376         unlock_new_inode(i);
 377         return i;
 378
 379 eio:
 380         ret = -EIO;
 381 error:
 382         pr_err("read error for inode 0x%lx\n", pos);
 383         return ERR_PTR(ret);
 384 }
 385
 386 /*
 387  * allocate a new inode
 388  */
 389 static struct inode *romfs_alloc_inode(struct super_block *sb)
 390 {
 391         struct romfs_inode_info *inode;
 392
 393         inode = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL);
 394         return inode ? &inode->vfs_inode : NULL;
 395 }
 396
 397 /*
 398  * return a spent inode to the slab cache
 399  */
 400 static void romfs_i_callback(struct rcu_head *head)
 401 {
 402         struct inode *inode = container_of(head, struct inode, i_rcu);
 403
 404         kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
 405 }
 406
 407 static void romfs_destroy_inode(struct inode *inode)
 408 {
 409         call_rcu(&inode->i_rcu, romfs_i_callback);
 410 }
 411
 412 /*
 413  * get filesystem statistics
 414  */
 415 static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 416 {
 417         struct super_block *sb = dentry->d_sb;
 418         u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
 419
 420         buf->f_type = ROMFS_MAGIC;
 421         buf->f_namelen = ROMFS_MAXFN;
 422         buf->f_bsize = ROMBSIZE;
 423         buf->f_bfree = buf->f_bavail = buf->f_ffree;
 424         buf->f_blocks =
 425                 (romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS;
 426         buf->f_fsid.val[0] = (u32)id;
 427         buf->f_fsid.val[1] = (u32)(id >> 32);
 428         return 0;
 429 }
 430
 431 /*
 432  * remounting must involve read-only
 433  */
 434 static int romfs_remount(struct super_block *sb, int *flags, char *data)
 435 {
 436         sync_filesystem(sb);
 437         *flags |= MS_RDONLY;
 438         return 0;
 439 }
 440
 441 static const struct super_operations romfs_super_ops = {
 442         .alloc_inode    = romfs_alloc_inode,
 443         .destroy_inode  = romfs_destroy_inode,
 444         .statfs         = romfs_statfs,
 445         .remount_fs     = romfs_remount,
 446 };
 447
 448 /*
 449  * checksum check on part of a romfs filesystem
 450  */
 451 static __u32 romfs_checksum(const void *data, int size)
 452 {
 453         const __be32 *ptr = data;
 454         __u32 sum;
 455
 456         sum = 0;
 457         size >>= 2;
 458         while (size > 0) {
 459                 sum += be32_to_cpu(*ptr++);
 460                 size--;
 461         }
 462         return sum;
 463 }
 464
 465 /*
 466  * fill in the superblock
 467  */
 468 static int romfs_fill_super(struct super_block *sb, void *data, int silent)
 469 {
 470         struct romfs_super_block *rsb;
 471         struct inode *root;
 472         unsigned long pos, img_size;
 473         const char *storage;
 474         size_t len;
 475         int ret;
 476
 477 #ifdef CONFIG_BLOCK
 478         if (!sb->s_mtd) {
 479                 sb_set_blocksize(sb, ROMBSIZE);
 480         } else {
 481                 sb->s_blocksize = ROMBSIZE;
 482                 sb->s_blocksize_bits = blksize_bits(ROMBSIZE);
 483         }
 484 #endif
 485
 486         sb->s_maxbytes = 0xFFFFFFFF;
 487         sb->s_magic = ROMFS_MAGIC;
 488         sb->s_flags |= MS_RDONLY | MS_NOATIME;
 489         sb->s_op = &romfs_super_ops;
 490
 491         /* read the image superblock and check it */
 492         rsb = kmalloc(512, GFP_KERNEL);
 493         if (!rsb)
 494                 return -ENOMEM;
 495
 496         sb->s_fs_info = (void *) 512;
 497         ret = romfs_dev_read(sb, 0, rsb, 512);
 498         if (ret < 0)
 499                 goto error_rsb;
 500
 501         img_size = be32_to_cpu(rsb->size);
 502
 503         if (sb->s_mtd && img_size > sb->s_mtd->size)
 504                 goto error_rsb_inval;
 505
 506         sb->s_fs_info = (void *) img_size;
 507
 508         if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 ||
 509             img_size < ROMFH_SIZE) {
 510                 if (!silent)
 511                         pr_warn("VFS: Can't find a romfs filesystem on dev %s.\n",
 512                                sb->s_id);
 513                 goto error_rsb_inval;
 514         }
 515
 516         if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) {
 517                 pr_err("bad initial checksum on dev %s.\n", sb->s_id);
 518                 goto error_rsb_inval;
 519         }
 520
 521         storage = sb->s_mtd ? "MTD" : "the block layer";
 522
 523         len = strnlen(rsb->name, ROMFS_MAXFN);
 524         if (!silent)
 525                 pr_notice("Mounting image '%*.*s' through %s\n",
 526                           (unsigned) len, (unsigned) len, rsb->name, storage);
 527
 528         kfree(rsb);
 529         rsb = NULL;
 530
 531         /* find the root directory */
 532         pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;
 533
 534         root = romfs_iget(sb, pos);
 535         if (IS_ERR(root))
 536                 return PTR_ERR(root);
 537
 538         sb->s_root = d_make_root(root);
 539         if (!sb->s_root)
 540                 return -ENOMEM;
 541
 542         return 0;
 543
 544 error_rsb_inval:
 545         ret = -EINVAL;
 546 error_rsb:
 547         kfree(rsb);
 548         return ret;
 549 }
 550
 551 /*
 552  * get a superblock for mounting
 553  */
 554 static struct dentry *romfs_mount(struct file_system_type *fs_type,
 555                         int flags, const char *dev_name,
 556                         void *data)
 557 {
 558         struct dentry *ret = ERR_PTR(-EINVAL);
 559
 560 #ifdef CONFIG_ROMFS_ON_MTD
 561         ret = mount_mtd(fs_type, flags, dev_name, data, romfs_fill_super);
 562 #endif
 563 #ifdef CONFIG_ROMFS_ON_BLOCK
 564         if (ret == ERR_PTR(-EINVAL))
 565                 ret = mount_bdev(fs_type, flags, dev_name, data,
 566                                   romfs_fill_super);
 567 #endif
 568         return ret;
 569 }
 570
 571 /*
 572  * destroy a romfs superblock in the appropriate manner
 573  */
 574 static void romfs_kill_sb(struct super_block *sb)
 575 {
 576 #ifdef CONFIG_ROMFS_ON_MTD
 577         if (sb->s_mtd) {
 578                 kill_mtd_super(sb);
 579                 return;
 580         }
 581 #endif
 582 #ifdef CONFIG_ROMFS_ON_BLOCK
 583         if (sb->s_bdev) {
 584                 kill_block_super(sb);
 585                 return;
 586         }
 587 #endif
 588 }
 589
 590 static struct file_system_type romfs_fs_type = {
 591         .owner          = THIS_MODULE,
 592         .name           = "romfs",
 593         .mount          = romfs_mount,
 594         .kill_sb        = romfs_kill_sb,
 595         .fs_flags       = FS_REQUIRES_DEV,
 596 };
 597 MODULE_ALIAS_FS("romfs");
 598
 599 /*
 600  * inode storage initialiser
 601  */
 602 static void romfs_i_init_once(void *_inode)
 603 {
 604         struct romfs_inode_info *inode = _inode;
 605
 606         inode_init_once(&inode->vfs_inode);
 607 }
 608
 609 /*
 610  * romfs module initialisation
 611  */
 612 static int __init init_romfs_fs(void)
 613 {
 614         int ret;
 615
 616         pr_info("ROMFS MTD (C) 2007 Red Hat, Inc.\n");
 617
 618         romfs_inode_cachep =
 619                 kmem_cache_create("romfs_i",
 620                                   sizeof(struct romfs_inode_info), 0,
 621                                   SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
 622                                   romfs_i_init_once);
 623
 624         if (!romfs_inode_cachep) {
 625                 pr_err("Failed to initialise inode cache\n");
 626                 return -ENOMEM;
 627         }
 628         ret = register_filesystem(&romfs_fs_type);
 629         if (ret) {
 630                 pr_err("Failed to register filesystem\n");
 631                 goto error_register;
 632         }
 633         return 0;
 634
 635 error_register:
 636         kmem_cache_destroy(romfs_inode_cachep);
 637         return ret;
 638 }
 639
 640 /*
 641  * romfs module removal
 642  */
 643 static void __exit exit_romfs_fs(void)
 644 {
 645         unregister_filesystem(&romfs_fs_type);
 646         /*
 647          * Make sure all delayed rcu free inodes are flushed before we
 648          * destroy cache.
 649          */
 650         rcu_barrier();
 651         kmem_cache_destroy(romfs_inode_cachep);
 652 }
 653
 654 module_init(init_romfs_fs);
 655 module_exit(exit_romfs_fs);
 656
 657 MODULE_DESCRIPTION("Direct-MTD Capable RomFS");
 658 MODULE_AUTHOR("Red Hat, Inc.");
 659 MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */