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 read_folio
  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 read_folio
  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/fs_context.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 <linux/major.h>
  78 #include "internal.h"
  79
  80 static struct kmem_cache *romfs_inode_cachep;
  81
  82 static const umode_t romfs_modemap[8] = {
  83         0,                      /* hard link */
  84         S_IFDIR  | 0644,        /* directory */
  85         S_IFREG  | 0644,        /* regular file */
  86         S_IFLNK  | 0777,        /* symlink */
  87         S_IFBLK  | 0600,        /* blockdev */
  88         S_IFCHR  | 0600,        /* chardev */
  89         S_IFSOCK | 0644,        /* socket */
  90         S_IFIFO  | 0644         /* FIFO */
  91 };
  92
  93 static const unsigned char romfs_dtype_table[] = {
  94         DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO
  95 };
  96
  97 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos);
  98
  99 /*
 100  * read a page worth of data from the image
 101  */
 102 static int romfs_read_folio(struct file *file, struct folio *folio)
 103 {
 104         struct inode *inode = folio->mapping->host;
 105         loff_t offset, size;
 106         unsigned long fillsize, pos;
 107         void *buf;
 108         int ret;
 109
 110         buf = kmap_local_folio(folio, 0);
 111
 112         offset = folio_pos(folio);
 113         size = i_size_read(inode);
 114         fillsize = 0;
 115         ret = 0;
 116         if (offset < size) {
 117                 size -= offset;
 118                 fillsize = size > PAGE_SIZE ? PAGE_SIZE : size;
 119
 120                 pos = ROMFS_I(inode)->i_dataoffset + offset;
 121
 122                 ret = romfs_dev_read(inode->i_sb, pos, buf, fillsize);
 123                 if (ret < 0) {
 124                         fillsize = 0;
 125                         ret = -EIO;
 126                 }
 127         }
 128
 129         buf = folio_zero_tail(folio, fillsize, buf + fillsize);
 130         kunmap_local(buf);
 131         folio_end_read(folio, ret == 0);
 132         return ret;
 133 }
 134
 135 static const struct address_space_operations romfs_aops = {
 136         .read_folio     = romfs_read_folio
 137 };
 138
 139 /*
 140  * read the entries from a directory
 141  */
 142 static int romfs_readdir(struct file *file, struct dir_context *ctx)
 143 {
 144         struct inode *i = file_inode(file);
 145         struct romfs_inode ri;
 146         unsigned long offset, maxoff;
 147         int j, ino, nextfh;
 148         char fsname[ROMFS_MAXFN];       /* XXX dynamic? */
 149         int ret;
 150
 151         maxoff = romfs_maxsize(i->i_sb);
 152
 153         offset = ctx->pos;
 154         if (!offset) {
 155                 offset = i->i_ino & ROMFH_MASK;
 156                 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
 157                 if (ret < 0)
 158                         goto out;
 159                 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 160         }
 161
 162         /* Not really failsafe, but we are read-only... */
 163         for (;;) {
 164                 if (!offset || offset >= maxoff) {
 165                         offset = maxoff;
 166                         ctx->pos = offset;
 167                         goto out;
 168                 }
 169                 ctx->pos = offset;
 170
 171                 /* Fetch inode info */
 172                 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
 173                 if (ret < 0)
 174                         goto out;
 175
 176                 j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE,
 177                                       sizeof(fsname) - 1);
 178                 if (j < 0)
 179                         goto out;
 180
 181                 ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j);
 182                 if (ret < 0)
 183                         goto out;
 184                 fsname[j] = '\0';
 185
 186                 ino = offset;
 187                 nextfh = be32_to_cpu(ri.next);
 188                 if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
 189                         ino = be32_to_cpu(ri.spec);
 190                 if (!dir_emit(ctx, fsname, j, ino,
 191                             romfs_dtype_table[nextfh & ROMFH_TYPE]))
 192                         goto out;
 193
 194                 offset = nextfh & ROMFH_MASK;
 195         }
 196 out:
 197         return 0;
 198 }
 199
 200 /*
 201  * look up an entry in a directory
 202  */
 203 static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,
 204                                    unsigned int flags)
 205 {
 206         unsigned long offset, maxoff;
 207         struct inode *inode = NULL;
 208         struct romfs_inode ri;
 209         const char *name;               /* got from dentry */
 210         int len, ret;
 211
 212         offset = dir->i_ino & ROMFH_MASK;
 213         ret = romfs_dev_read(dir->i_sb, offset, &ri, ROMFH_SIZE);
 214         if (ret < 0)
 215                 goto error;
 216
 217         /* search all the file entries in the list starting from the one
 218          * pointed to by the directory's special data */
 219         maxoff = romfs_maxsize(dir->i_sb);
 220         offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 221
 222         name = dentry->d_name.name;
 223         len = dentry->d_name.len;
 224
 225         for (;;) {
 226                 if (!offset || offset >= maxoff)
 227                         break;
 228
 229                 ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri));
 230                 if (ret < 0)
 231                         goto error;
 232
 233                 /* try to match the first 16 bytes of name */
 234                 ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name,
 235                                        len);
 236                 if (ret < 0)
 237                         goto error;
 238                 if (ret == 1) {
 239                         /* Hard link handling */
 240                         if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
 241                                 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 242                         inode = romfs_iget(dir->i_sb, offset);
 243                         break;
 244                 }
 245
 246                 /* next entry */
 247                 offset = be32_to_cpu(ri.next) & ROMFH_MASK;
 248         }
 249
 250         return d_splice_alias(inode, dentry);
 251 error:
 252         return ERR_PTR(ret);
 253 }
 254
 255 static const struct file_operations romfs_dir_operations = {
 256         .read           = generic_read_dir,
 257         .iterate_shared = romfs_readdir,
 258         .llseek         = generic_file_llseek,
 259 };
 260
 261 static const struct inode_operations romfs_dir_inode_operations = {
 262         .lookup         = romfs_lookup,
 263 };
 264
 265 /*
 266  * get a romfs inode based on its position in the image (which doubles as the
 267  * inode number)
 268  */
 269 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos)
 270 {
 271         struct romfs_inode_info *inode;
 272         struct romfs_inode ri;
 273         struct inode *i;
 274         unsigned long nlen;
 275         unsigned nextfh;
 276         int ret;
 277         umode_t mode;
 278
 279         /* we might have to traverse a chain of "hard link" file entries to get
 280          * to the actual file */
 281         for (;;) {
 282                 ret = romfs_dev_read(sb, pos, &ri, sizeof(ri));
 283                 if (ret < 0)
 284                         goto error;
 285
 286                 /* XXX: do romfs_checksum here too (with name) */
 287
 288                 nextfh = be32_to_cpu(ri.next);
 289                 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
 290                         break;
 291
 292                 pos = be32_to_cpu(ri.spec) & ROMFH_MASK;
 293         }
 294
 295         /* determine the length of the filename */
 296         nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN);
 297         if (IS_ERR_VALUE(nlen))
 298                 goto eio;
 299
 300         /* get an inode for this image position */
 301         i = iget_locked(sb, pos);
 302         if (!i)
 303                 return ERR_PTR(-ENOMEM);
 304
 305         if (!(i->i_state & I_NEW))
 306                 return i;
 307
 308         /* precalculate the data offset */
 309         inode = ROMFS_I(i);
 310         inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK;
 311         inode->i_dataoffset = pos + inode->i_metasize;
 312
 313         set_nlink(i, 1);                /* Hard to decide.. */
 314         i->i_size = be32_to_cpu(ri.size);
 315         inode_set_mtime_to_ts(i,
 316                               inode_set_atime_to_ts(i, inode_set_ctime(i, 0, 0)));
 317
 318         /* set up mode and ops */
 319         mode = romfs_modemap[nextfh & ROMFH_TYPE];
 320
 321         switch (nextfh & ROMFH_TYPE) {
 322         case ROMFH_DIR:
 323                 i->i_size = ROMFS_I(i)->i_metasize;
 324                 i->i_op = &romfs_dir_inode_operations;
 325                 i->i_fop = &romfs_dir_operations;
 326                 if (nextfh & ROMFH_EXEC)
 327                         mode |= S_IXUGO;
 328                 break;
 329         case ROMFH_REG:
 330                 i->i_fop = &romfs_ro_fops;
 331                 i->i_data.a_ops = &romfs_aops;
 332                 if (nextfh & ROMFH_EXEC)
 333                         mode |= S_IXUGO;
 334                 break;
 335         case ROMFH_SYM:
 336                 i->i_op = &page_symlink_inode_operations;
 337                 inode_nohighmem(i);
 338                 i->i_data.a_ops = &romfs_aops;
 339                 mode |= S_IRWXUGO;
 340                 break;
 341         default:
 342                 /* depending on MBZ for sock/fifos */
 343                 nextfh = be32_to_cpu(ri.spec);
 344                 init_special_inode(i, mode, MKDEV(nextfh >> 16,
 345                                                   nextfh & 0xffff));
 346                 break;
 347         }
 348
 349         i->i_mode = mode;
 350         i->i_blocks = (i->i_size + 511) >> 9;
 351
 352         unlock_new_inode(i);
 353         return i;
 354
 355 eio:
 356         ret = -EIO;
 357 error:
 358         pr_err("read error for inode 0x%lx\n", pos);
 359         return ERR_PTR(ret);
 360 }
 361
 362 /*
 363  * allocate a new inode
 364  */
 365 static struct inode *romfs_alloc_inode(struct super_block *sb)
 366 {
 367         struct romfs_inode_info *inode;
 368
 369         inode = alloc_inode_sb(sb, romfs_inode_cachep, GFP_KERNEL);
 370         return inode ? &inode->vfs_inode : NULL;
 371 }
 372
 373 /*
 374  * return a spent inode to the slab cache
 375  */
 376 static void romfs_free_inode(struct inode *inode)
 377 {
 378         kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
 379 }
 380
 381 /*
 382  * get filesystem statistics
 383  */
 384 static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 385 {
 386         struct super_block *sb = dentry->d_sb;
 387         u64 id = 0;
 388
 389         /* When calling huge_encode_dev(),
 390          * use sb->s_bdev->bd_dev when,
 391          *   - CONFIG_ROMFS_ON_BLOCK defined
 392          * use sb->s_dev when,
 393          *   - CONFIG_ROMFS_ON_BLOCK undefined and
 394          *   - CONFIG_ROMFS_ON_MTD defined
 395          * leave id as 0 when,
 396          *   - CONFIG_ROMFS_ON_BLOCK undefined and
 397          *   - CONFIG_ROMFS_ON_MTD undefined
 398          */
 399         if (sb->s_bdev)
 400                 id = huge_encode_dev(sb->s_bdev->bd_dev);
 401         else if (sb->s_dev)
 402                 id = huge_encode_dev(sb->s_dev);
 403
 404         buf->f_type = ROMFS_MAGIC;
 405         buf->f_namelen = ROMFS_MAXFN;
 406         buf->f_bsize = ROMBSIZE;
 407         buf->f_bfree = buf->f_bavail = buf->f_ffree;
 408         buf->f_blocks =
 409                 (romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS;
 410         buf->f_fsid = u64_to_fsid(id);
 411         return 0;
 412 }
 413
 414 /*
 415  * remounting must involve read-only
 416  */
 417 static int romfs_reconfigure(struct fs_context *fc)
 418 {
 419         sync_filesystem(fc->root->d_sb);
 420         fc->sb_flags |= SB_RDONLY;
 421         return 0;
 422 }
 423
 424 static const struct super_operations romfs_super_ops = {
 425         .alloc_inode    = romfs_alloc_inode,
 426         .free_inode     = romfs_free_inode,
 427         .statfs         = romfs_statfs,
 428 };
 429
 430 /*
 431  * checksum check on part of a romfs filesystem
 432  */
 433 static __u32 romfs_checksum(const void *data, int size)
 434 {
 435         const __be32 *ptr = data;
 436         __u32 sum;
 437
 438         sum = 0;
 439         size >>= 2;
 440         while (size > 0) {
 441                 sum += be32_to_cpu(*ptr++);
 442                 size--;
 443         }
 444         return sum;
 445 }
 446
 447 /*
 448  * fill in the superblock
 449  */
 450 static int romfs_fill_super(struct super_block *sb, struct fs_context *fc)
 451 {
 452         struct romfs_super_block *rsb;
 453         struct inode *root;
 454         unsigned long pos, img_size;
 455         const char *storage;
 456         size_t len;
 457         int ret;
 458
 459 #ifdef CONFIG_BLOCK
 460         if (!sb->s_mtd) {
 461                 sb_set_blocksize(sb, ROMBSIZE);
 462         } else {
 463                 sb->s_blocksize = ROMBSIZE;
 464                 sb->s_blocksize_bits = blksize_bits(ROMBSIZE);
 465         }
 466 #endif
 467
 468         sb->s_maxbytes = 0xFFFFFFFF;
 469         sb->s_magic = ROMFS_MAGIC;
 470         sb->s_flags |= SB_RDONLY | SB_NOATIME;
 471         sb->s_time_min = 0;
 472         sb->s_time_max = 0;
 473         sb->s_op = &romfs_super_ops;
 474
 475 #ifdef CONFIG_ROMFS_ON_MTD
 476         /* Use same dev ID from the underlying mtdblock device */
 477         if (sb->s_mtd)
 478                 sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, sb->s_mtd->index);
 479 #endif
 480         /* read the image superblock and check it */
 481         rsb = kmalloc(512, GFP_KERNEL);
 482         if (!rsb)
 483                 return -ENOMEM;
 484
 485         sb->s_fs_info = (void *) 512;
 486         ret = romfs_dev_read(sb, 0, rsb, 512);
 487         if (ret < 0)
 488                 goto error_rsb;
 489
 490         img_size = be32_to_cpu(rsb->size);
 491
 492         if (sb->s_mtd && img_size > sb->s_mtd->size)
 493                 goto error_rsb_inval;
 494
 495         sb->s_fs_info = (void *) img_size;
 496
 497         if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 ||
 498             img_size < ROMFH_SIZE) {
 499                 if (!(fc->sb_flags & SB_SILENT))
 500                         errorf(fc, "VFS: Can't find a romfs filesystem on dev %s.\n",
 501                                sb->s_id);
 502                 goto error_rsb_inval;
 503         }
 504
 505         if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) {
 506                 pr_err("bad initial checksum on dev %s.\n", sb->s_id);
 507                 goto error_rsb_inval;
 508         }
 509
 510         storage = sb->s_mtd ? "MTD" : "the block layer";
 511
 512         len = strnlen(rsb->name, ROMFS_MAXFN);
 513         if (!(fc->sb_flags & SB_SILENT))
 514                 pr_notice("Mounting image '%*.*s' through %s\n",
 515                           (unsigned) len, (unsigned) len, rsb->name, storage);
 516
 517         kfree(rsb);
 518         rsb = NULL;
 519
 520         /* find the root directory */
 521         pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;
 522
 523         root = romfs_iget(sb, pos);
 524         if (IS_ERR(root))
 525                 return PTR_ERR(root);
 526
 527         sb->s_root = d_make_root(root);
 528         if (!sb->s_root)
 529                 return -ENOMEM;
 530
 531         return 0;
 532
 533 error_rsb_inval:
 534         ret = -EINVAL;
 535 error_rsb:
 536         kfree(rsb);
 537         return ret;
 538 }
 539
 540 /*
 541  * get a superblock for mounting
 542  */
 543 static int romfs_get_tree(struct fs_context *fc)
 544 {
 545         int ret = -EINVAL;
 546
 547 #ifdef CONFIG_ROMFS_ON_MTD
 548         ret = get_tree_mtd(fc, romfs_fill_super);
 549 #endif
 550 #ifdef CONFIG_ROMFS_ON_BLOCK
 551         if (ret == -EINVAL)
 552                 ret = get_tree_bdev(fc, romfs_fill_super);
 553 #endif
 554         return ret;
 555 }
 556
 557 static const struct fs_context_operations romfs_context_ops = {
 558         .get_tree       = romfs_get_tree,
 559         .reconfigure    = romfs_reconfigure,
 560 };
 561
 562 /*
 563  * Set up the filesystem mount context.
 564  */
 565 static int romfs_init_fs_context(struct fs_context *fc)
 566 {
 567         fc->ops = &romfs_context_ops;
 568         return 0;
 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         generic_shutdown_super(sb);
 577
 578 #ifdef CONFIG_ROMFS_ON_MTD
 579         if (sb->s_mtd) {
 580                 put_mtd_device(sb->s_mtd);
 581                 sb->s_mtd = NULL;
 582         }
 583 #endif
 584 #ifdef CONFIG_ROMFS_ON_BLOCK
 585         if (sb->s_bdev) {
 586                 sync_blockdev(sb->s_bdev);
 587                 bdev_fput(sb->s_bdev_file);
 588         }
 589 #endif
 590 }
 591
 592 static struct file_system_type romfs_fs_type = {
 593         .owner          = THIS_MODULE,
 594         .name           = "romfs",
 595         .init_fs_context = romfs_init_fs_context,
 596         .kill_sb        = romfs_kill_sb,
 597         .fs_flags       = FS_REQUIRES_DEV,
 598 };
 599 MODULE_ALIAS_FS("romfs");
 600
 601 /*
 602  * inode storage initialiser
 603  */
 604 static void romfs_i_init_once(void *_inode)
 605 {
 606         struct romfs_inode_info *inode = _inode;
 607
 608         inode_init_once(&inode->vfs_inode);
 609 }
 610
 611 /*
 612  * romfs module initialisation
 613  */
 614 static int __init init_romfs_fs(void)
 615 {
 616         int ret;
 617
 618         pr_info("ROMFS MTD (C) 2007 Red Hat, Inc.\n");
 619
 620         romfs_inode_cachep =
 621                 kmem_cache_create("romfs_i",
 622                                   sizeof(struct romfs_inode_info), 0,
 623                                   SLAB_RECLAIM_ACCOUNT | SLAB_ACCOUNT,
 624                                   romfs_i_init_once);
 625
 626         if (!romfs_inode_cachep) {
 627                 pr_err("Failed to initialise inode cache\n");
 628                 return -ENOMEM;
 629         }
 630         ret = register_filesystem(&romfs_fs_type);
 631         if (ret) {
 632                 pr_err("Failed to register filesystem\n");
 633                 goto error_register;
 634         }
 635         return 0;
 636
 637 error_register:
 638         kmem_cache_destroy(romfs_inode_cachep);
 639         return ret;
 640 }
 641
 642 /*
 643  * romfs module removal
 644  */
 645 static void __exit exit_romfs_fs(void)
 646 {
 647         unregister_filesystem(&romfs_fs_type);
 648         /*
 649          * Make sure all delayed rcu free inodes are flushed before we
 650          * destroy cache.
 651          */
 652         rcu_barrier();
 653         kmem_cache_destroy(romfs_inode_cachep);
 654 }
 655
 656 module_init(init_romfs_fs);
 657 module_exit(exit_romfs_fs);
 658
 659 MODULE_DESCRIPTION("Direct-MTD Capable RomFS");
 660 MODULE_AUTHOR("Red Hat, Inc.");
 661 MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */