linux/fs/romfs/super.c
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   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#include <linux/module.h>
  60#include <linux/string.h>
  61#include <linux/fs.h>
  62#include <linux/time.h>
  63#include <linux/slab.h>
  64#include <linux/init.h>
  65#include <linux/blkdev.h>
  66#include <linux/parser.h>
  67#include <linux/mount.h>
  68#include <linux/namei.h>
  69#include <linux/statfs.h>
  70#include <linux/mtd/super.h>
  71#include <linux/ctype.h>
  72#include <linux/highmem.h>
  73#include <linux/pagemap.h>
  74#include <linux/uaccess.h>
  75#include "internal.h"
  76
  77static struct kmem_cache *romfs_inode_cachep;
  78
  79static const umode_t romfs_modemap[8] = {
  80        0,                      /* hard link */
  81        S_IFDIR  | 0644,        /* directory */
  82        S_IFREG  | 0644,        /* regular file */
  83        S_IFLNK  | 0777,        /* symlink */
  84        S_IFBLK  | 0600,        /* blockdev */
  85        S_IFCHR  | 0600,        /* chardev */
  86        S_IFSOCK | 0644,        /* socket */
  87        S_IFIFO  | 0644         /* FIFO */
  88};
  89
  90static const unsigned char romfs_dtype_table[] = {
  91        DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO
  92};
  93
  94static struct inode *romfs_iget(struct super_block *sb, unsigned long pos);
  95
  96/*
  97 * read a page worth of data from the image
  98 */
  99static int romfs_readpage(struct file *file, struct page *page)
 100{
 101        struct inode *inode = page->mapping->host;
 102        loff_t offset, size;
 103        unsigned long fillsize, pos;
 104        void *buf;
 105        int ret;
 106
 107        buf = kmap(page);
 108        if (!buf)
 109                return -ENOMEM;
 110
 111        /* 32 bit warning -- but not for us :) */
 112        offset = page_offset(page);
 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                        SetPageError(page);
 125                        fillsize = 0;
 126                        ret = -EIO;
 127                }
 128        }
 129
 130        if (fillsize < PAGE_SIZE)
 131                memset(buf + fillsize, 0, PAGE_SIZE - fillsize);
 132        if (ret == 0)
 133                SetPageUptodate(page);
 134
 135        flush_dcache_page(page);
 136        kunmap(page);
 137        unlock_page(page);
 138        return ret;
 139}
 140
 141static const struct address_space_operations romfs_aops = {
 142        .readpage       = romfs_readpage
 143};
 144
 145/*
 146 * read the entries from a directory
 147 */
 148static int romfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 149{
 150        struct inode *i = filp->f_dentry->d_inode;
 151        struct romfs_inode ri;
 152        unsigned long offset, maxoff;
 153        int j, ino, nextfh;
 154        int stored = 0;
 155        char fsname[ROMFS_MAXFN];       /* XXX dynamic? */
 156        int ret;
 157
 158        maxoff = romfs_maxsize(i->i_sb);
 159
 160        offset = filp->f_pos;
 161        if (!offset) {
 162                offset = i->i_ino & ROMFH_MASK;
 163                ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
 164                if (ret < 0)
 165                        goto out;
 166                offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 167        }
 168
 169        /* Not really failsafe, but we are read-only... */
 170        for (;;) {
 171                if (!offset || offset >= maxoff) {
 172                        offset = maxoff;
 173                        filp->f_pos = offset;
 174                        goto out;
 175                }
 176                filp->f_pos = offset;
 177
 178                /* Fetch inode info */
 179                ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
 180                if (ret < 0)
 181                        goto out;
 182
 183                j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE,
 184                                      sizeof(fsname) - 1);
 185                if (j < 0)
 186                        goto out;
 187
 188                ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j);
 189                if (ret < 0)
 190                        goto out;
 191                fsname[j] = '\0';
 192
 193                ino = offset;
 194                nextfh = be32_to_cpu(ri.next);
 195                if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
 196                        ino = be32_to_cpu(ri.spec);
 197                if (filldir(dirent, fsname, j, offset, ino,
 198                            romfs_dtype_table[nextfh & ROMFH_TYPE]) < 0)
 199                        goto out;
 200
 201                stored++;
 202                offset = nextfh & ROMFH_MASK;
 203        }
 204
 205out:
 206        return stored;
 207}
 208
 209/*
 210 * look up an entry in a directory
 211 */
 212static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,
 213                                   unsigned int flags)
 214{
 215        unsigned long offset, maxoff;
 216        struct inode *inode;
 217        struct romfs_inode ri;
 218        const char *name;               /* got from dentry */
 219        int len, ret;
 220
 221        offset = dir->i_ino & ROMFH_MASK;
 222        ret = romfs_dev_read(dir->i_sb, offset, &ri, ROMFH_SIZE);
 223        if (ret < 0)
 224                goto error;
 225
 226        /* search all the file entries in the list starting from the one
 227         * pointed to by the directory's special data */
 228        maxoff = romfs_maxsize(dir->i_sb);
 229        offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 230
 231        name = dentry->d_name.name;
 232        len = dentry->d_name.len;
 233
 234        for (;;) {
 235                if (!offset || offset >= maxoff)
 236                        goto out0;
 237
 238                ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri));
 239                if (ret < 0)
 240                        goto error;
 241
 242                /* try to match the first 16 bytes of name */
 243                ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name,
 244                                       len);
 245                if (ret < 0)
 246                        goto error;
 247                if (ret == 1)
 248                        break;
 249
 250                /* next entry */
 251                offset = be32_to_cpu(ri.next) & ROMFH_MASK;
 252        }
 253
 254        /* Hard link handling */
 255        if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
 256                offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 257
 258        inode = romfs_iget(dir->i_sb, offset);
 259        if (IS_ERR(inode)) {
 260                ret = PTR_ERR(inode);
 261                goto error;
 262        }
 263        goto outi;
 264
 265        /*
 266         * it's a bit funky, _lookup needs to return an error code
 267         * (negative) or a NULL, both as a dentry.  ENOENT should not
 268         * be returned, instead we need to create a negative dentry by
 269         * d_add(dentry, NULL); and return 0 as no error.
 270         * (Although as I see, it only matters on writable file
 271         * systems).
 272         */
 273out0:
 274        inode = NULL;
 275outi:
 276        d_add(dentry, inode);
 277        ret = 0;
 278error:
 279        return ERR_PTR(ret);
 280}
 281
 282static const struct file_operations romfs_dir_operations = {
 283        .read           = generic_read_dir,
 284        .readdir        = romfs_readdir,
 285        .llseek         = default_llseek,
 286};
 287
 288static const struct inode_operations romfs_dir_inode_operations = {
 289        .lookup         = romfs_lookup,
 290};
 291
 292/*
 293 * get a romfs inode based on its position in the image (which doubles as the
 294 * inode number)
 295 */
 296static struct inode *romfs_iget(struct super_block *sb, unsigned long pos)
 297{
 298        struct romfs_inode_info *inode;
 299        struct romfs_inode ri;
 300        struct inode *i;
 301        unsigned long nlen;
 302        unsigned nextfh;
 303        int ret;
 304        umode_t mode;
 305
 306        /* we might have to traverse a chain of "hard link" file entries to get
 307         * to the actual file */
 308        for (;;) {
 309                ret = romfs_dev_read(sb, pos, &ri, sizeof(ri));
 310                if (ret < 0)
 311                        goto error;
 312
 313                /* XXX: do romfs_checksum here too (with name) */
 314
 315                nextfh = be32_to_cpu(ri.next);
 316                if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
 317                        break;
 318
 319                pos = be32_to_cpu(ri.spec) & ROMFH_MASK;
 320        }
 321
 322        /* determine the length of the filename */
 323        nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN);
 324        if (IS_ERR_VALUE(nlen))
 325                goto eio;
 326
 327        /* get an inode for this image position */
 328        i = iget_locked(sb, pos);
 329        if (!i)
 330                return ERR_PTR(-ENOMEM);
 331
 332        if (!(i->i_state & I_NEW))
 333                return i;
 334
 335        /* precalculate the data offset */
 336        inode = ROMFS_I(i);
 337        inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK;
 338        inode->i_dataoffset = pos + inode->i_metasize;
 339
 340        set_nlink(i, 1);                /* Hard to decide.. */
 341        i->i_size = be32_to_cpu(ri.size);
 342        i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0;
 343        i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0;
 344
 345        /* set up mode and ops */
 346        mode = romfs_modemap[nextfh & ROMFH_TYPE];
 347
 348        switch (nextfh & ROMFH_TYPE) {
 349        case ROMFH_DIR:
 350                i->i_size = ROMFS_I(i)->i_metasize;
 351                i->i_op = &romfs_dir_inode_operations;
 352                i->i_fop = &romfs_dir_operations;
 353                if (nextfh & ROMFH_EXEC)
 354                        mode |= S_IXUGO;
 355                break;
 356        case ROMFH_REG:
 357                i->i_fop = &romfs_ro_fops;
 358                i->i_data.a_ops = &romfs_aops;
 359                if (i->i_sb->s_mtd)
 360                        i->i_data.backing_dev_info =
 361                                i->i_sb->s_mtd->backing_dev_info;
 362                if (nextfh & ROMFH_EXEC)
 363                        mode |= S_IXUGO;
 364                break;
 365        case ROMFH_SYM:
 366                i->i_op = &page_symlink_inode_operations;
 367                i->i_data.a_ops = &romfs_aops;
 368                mode |= S_IRWXUGO;
 369                break;
 370        default:
 371                /* depending on MBZ for sock/fifos */
 372                nextfh = be32_to_cpu(ri.spec);
 373                init_special_inode(i, mode, MKDEV(nextfh >> 16,
 374                                                  nextfh & 0xffff));
 375                break;
 376        }
 377
 378        i->i_mode = mode;
 379
 380        unlock_new_inode(i);
 381        return i;
 382
 383eio:
 384        ret = -EIO;
 385error:
 386        printk(KERN_ERR "ROMFS: read error for inode 0x%lx\n", pos);
 387        return ERR_PTR(ret);
 388}
 389
 390/*
 391 * allocate a new inode
 392 */
 393static struct inode *romfs_alloc_inode(struct super_block *sb)
 394{
 395        struct romfs_inode_info *inode;
 396        inode = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL);
 397        return inode ? &inode->vfs_inode : NULL;
 398}
 399
 400/*
 401 * return a spent inode to the slab cache
 402 */
 403static void romfs_i_callback(struct rcu_head *head)
 404{
 405        struct inode *inode = container_of(head, struct inode, i_rcu);
 406        kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
 407}
 408
 409static void romfs_destroy_inode(struct inode *inode)
 410{
 411        call_rcu(&inode->i_rcu, romfs_i_callback);
 412}
 413
 414/*
 415 * get filesystem statistics
 416 */
 417static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 418{
 419        struct super_block *sb = dentry->d_sb;
 420        u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
 421
 422        buf->f_type = ROMFS_MAGIC;
 423        buf->f_namelen = ROMFS_MAXFN;
 424        buf->f_bsize = ROMBSIZE;
 425        buf->f_bfree = buf->f_bavail = buf->f_ffree;
 426        buf->f_blocks =
 427                (romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS;
 428        buf->f_fsid.val[0] = (u32)id;
 429        buf->f_fsid.val[1] = (u32)(id >> 32);
 430        return 0;
 431}
 432
 433/*
 434 * remounting must involve read-only
 435 */
 436static int romfs_remount(struct super_block *sb, int *flags, char *data)
 437{
 438        *flags |= MS_RDONLY;
 439        return 0;
 440}
 441
 442static 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 */
 452static __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 */
 469static 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                        printk(KERN_WARNING "VFS:"
 513                               " Can't find a romfs filesystem on dev %s.\n",
 514                               sb->s_id);
 515                goto error_rsb_inval;
 516        }
 517
 518        if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) {
 519                printk(KERN_ERR "ROMFS: bad initial checksum on dev %s.\n",
 520                       sb->s_id);
 521                goto error_rsb_inval;
 522        }
 523
 524        storage = sb->s_mtd ? "MTD" : "the block layer";
 525
 526        len = strnlen(rsb->name, ROMFS_MAXFN);
 527        if (!silent)
 528                printk(KERN_NOTICE "ROMFS: Mounting image '%*.*s' through %s\n",
 529                       (unsigned) len, (unsigned) len, rsb->name, storage);
 530
 531        kfree(rsb);
 532        rsb = NULL;
 533
 534        /* find the root directory */
 535        pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;
 536
 537        root = romfs_iget(sb, pos);
 538        if (IS_ERR(root))
 539                goto error;
 540
 541        sb->s_root = d_make_root(root);
 542        if (!sb->s_root)
 543                goto error;
 544
 545        return 0;
 546
 547error:
 548        return -EINVAL;
 549error_rsb_inval:
 550        ret = -EINVAL;
 551error_rsb:
 552        kfree(rsb);
 553        return ret;
 554}
 555
 556/*
 557 * get a superblock for mounting
 558 */
 559static struct dentry *romfs_mount(struct file_system_type *fs_type,
 560                        int flags, const char *dev_name,
 561                        void *data)
 562{
 563        struct dentry *ret = ERR_PTR(-EINVAL);
 564
 565#ifdef CONFIG_ROMFS_ON_MTD
 566        ret = mount_mtd(fs_type, flags, dev_name, data, romfs_fill_super);
 567#endif
 568#ifdef CONFIG_ROMFS_ON_BLOCK
 569        if (ret == ERR_PTR(-EINVAL))
 570                ret = mount_bdev(fs_type, flags, dev_name, data,
 571                                  romfs_fill_super);
 572#endif
 573        return ret;
 574}
 575
 576/*
 577 * destroy a romfs superblock in the appropriate manner
 578 */
 579static void romfs_kill_sb(struct super_block *sb)
 580{
 581#ifdef CONFIG_ROMFS_ON_MTD
 582        if (sb->s_mtd) {
 583                kill_mtd_super(sb);
 584                return;
 585        }
 586#endif
 587#ifdef CONFIG_ROMFS_ON_BLOCK
 588        if (sb->s_bdev) {
 589                kill_block_super(sb);
 590                return;
 591        }
 592#endif
 593}
 594
 595static struct file_system_type romfs_fs_type = {
 596        .owner          = THIS_MODULE,
 597        .name           = "romfs",
 598        .mount          = romfs_mount,
 599        .kill_sb        = romfs_kill_sb,
 600        .fs_flags       = FS_REQUIRES_DEV,
 601};
 602
 603/*
 604 * inode storage initialiser
 605 */
 606static void romfs_i_init_once(void *_inode)
 607{
 608        struct romfs_inode_info *inode = _inode;
 609
 610        inode_init_once(&inode->vfs_inode);
 611}
 612
 613/*
 614 * romfs module initialisation
 615 */
 616static int __init init_romfs_fs(void)
 617{
 618        int ret;
 619
 620        printk(KERN_INFO "ROMFS MTD (C) 2007 Red Hat, Inc.\n");
 621
 622        romfs_inode_cachep =
 623                kmem_cache_create("romfs_i",
 624                                  sizeof(struct romfs_inode_info), 0,
 625                                  SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
 626                                  romfs_i_init_once);
 627
 628        if (!romfs_inode_cachep) {
 629                printk(KERN_ERR
 630                       "ROMFS error: Failed to initialise inode cache\n");
 631                return -ENOMEM;
 632        }
 633        ret = register_filesystem(&romfs_fs_type);
 634        if (ret) {
 635                printk(KERN_ERR "ROMFS error: Failed to register filesystem\n");
 636                goto error_register;
 637        }
 638        return 0;
 639
 640error_register:
 641        kmem_cache_destroy(romfs_inode_cachep);
 642        return ret;
 643}
 644
 645/*
 646 * romfs module removal
 647 */
 648static void __exit exit_romfs_fs(void)
 649{
 650        unregister_filesystem(&romfs_fs_type);
 651        kmem_cache_destroy(romfs_inode_cachep);
 652}
 653
 654module_init(init_romfs_fs);
 655module_exit(exit_romfs_fs);
 656
 657MODULE_DESCRIPTION("Direct-MTD Capable RomFS");
 658MODULE_AUTHOR("Red Hat, Inc.");
 659MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */
 660
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