lib/ext2fs/openfs.c

   1 /*
   2  * openfs.c --- open an ext2 filesystem
   3  *
   4  * Copyright (C) 1993, 1994, 1995, 1996 Theodore Ts'o.
   5  *
   6  * %Begin-Header%
   7  * This file may be redistributed under the terms of the GNU Public
   8  * License.
   9  * %End-Header%
  10  */
  11
  12 #include <stdio.h>
  13 #include <string.h>
  14 #if HAVE_UNISTD_H
  15 #include <unistd.h>
  16 #endif
  17 #include <fcntl.h>
  18 #include <time.h>
  19 #if HAVE_SYS_STAT_H
  20 #include <sys/stat.h>
  21 #endif
  22 #if HAVE_SYS_TYPES_H
  23 #include <sys/types.h>
  24 #endif
  25
  26 #include "ext2_fs.h"
  27
  28
  29 #include "ext2fs.h"
  30 #include "e2image.h"
  31
  32 blk_t ext2fs_descriptor_block_loc(ext2_filsys fs, blk_t group_block, dgrp_t i)
  33 {
  34         int     bg;
  35         int     has_super = 0;
  36
  37         if (!(fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG) ||
  38             (i < fs->super->s_first_meta_bg))
  39                 return (group_block + i + 1);
  40
  41         bg = (fs->blocksize / sizeof (struct ext2_group_desc)) * i;
  42         if (ext2fs_bg_has_super(fs, bg))
  43                 has_super = 1;
  44         return (fs->super->s_first_data_block + has_super +
  45                 (bg * fs->super->s_blocks_per_group));
  46 }
  47
  48 /*
  49  *  Note: if superblock is non-zero, block-size must also be non-zero.
  50  *      Superblock and block_size can be zero to use the default size.
  51  *
  52  * Valid flags for ext2fs_open()
  53  *
  54  *      EXT2_FLAG_RW    - Open the filesystem for read/write.
  55  *      EXT2_FLAG_FORCE - Open the filesystem even if some of the
  56  *                              features aren't supported.
  57  *      EXT2_FLAG_JOURNAL_DEV_OK - Open an ext3 journal device
  58  */
  59 errcode_t ext2fs_open(const char *name, int flags, int superblock,
  60                       int block_size, io_manager manager, ext2_filsys *ret_fs)
  61 {
  62         ext2_filsys     fs;
  63         errcode_t       retval;
  64         int             i, j, groups_per_block, blocks_per_group;
  65         blk_t           group_block, blk;
  66         char            *dest;
  67         struct ext2_group_desc *gdp;
  68
  69         EXT2_CHECK_MAGIC(manager, EXT2_ET_MAGIC_IO_MANAGER);
  70
  71         retval = ext2fs_get_mem(sizeof(struct struct_ext2_filsys),
  72                                 (void **) &fs);
  73         if (retval)
  74                 return retval;
  75
  76         memset(fs, 0, sizeof(struct struct_ext2_filsys));
  77         fs->magic = EXT2_ET_MAGIC_EXT2FS_FILSYS;
  78         fs->flags = flags;
  79         fs->umask = 022;
  80         retval = manager->open(name, (flags & EXT2_FLAG_RW) ? IO_FLAG_RW : 0,
  81                                &fs->io);
  82         if (retval)
  83                 goto cleanup;
  84         fs->io->app_data = fs;
  85         retval = ext2fs_get_mem(strlen(name)+1, (void **) &fs->device_name);
  86         if (retval)
  87                 goto cleanup;
  88         strcpy(fs->device_name, name);
  89         retval = ext2fs_get_mem(SUPERBLOCK_SIZE, (void **) &fs->super);
  90         if (retval)
  91                 goto cleanup;
  92         if (flags & EXT2_FLAG_IMAGE_FILE) {
  93                 retval = ext2fs_get_mem(sizeof(struct ext2_image_hdr),
  94                                         (void **) &fs->image_header);
  95                 if (retval)
  96                         goto cleanup;
  97                 retval = io_channel_read_blk(fs->io, 0,
  98                                              -sizeof(struct ext2_image_hdr),
  99                                              fs->image_header);
 100                 if (retval)
 101                         goto cleanup;
 102                 if (fs->image_header->magic_number != EXT2_ET_MAGIC_E2IMAGE)
 103                         return EXT2_ET_MAGIC_E2IMAGE;
 104                 superblock = 1;
 105                 block_size = fs->image_header->fs_blocksize;
 106         }
 107
 108         /*
 109          * If the user specifies a specific block # for the
 110          * superblock, then he/she must also specify the block size!
 111          * Otherwise, read the master superblock located at offset
 112          * SUPERBLOCK_OFFSET from the start of the partition.
 113          *
 114          * Note: we only save a backup copy of the superblock if we
 115          * are reading the superblock from the primary superblock location.
 116          */
 117         if (superblock) {
 118                 if (!block_size) {
 119                         retval = EXT2_ET_INVALID_ARGUMENT;
 120                         goto cleanup;
 121                 }
 122                 io_channel_set_blksize(fs->io, block_size);
 123                 group_block = superblock + 1;
 124                 fs->orig_super = 0;
 125         } else {
 126                 io_channel_set_blksize(fs->io, SUPERBLOCK_OFFSET);
 127                 superblock = 1;
 128                 group_block = 0;
 129                 retval = ext2fs_get_mem(SUPERBLOCK_SIZE,
 130                                         (void **) &fs->orig_super);
 131                 if (retval)
 132                         goto cleanup;
 133         }
 134         retval = io_channel_read_blk(fs->io, superblock, -SUPERBLOCK_SIZE,
 135                                      fs->super);
 136         if (retval)
 137                 goto cleanup;
 138         if (fs->orig_super)
 139                 memcpy(fs->orig_super, fs->super, SUPERBLOCK_SIZE);
 140
 141 #ifdef EXT2FS_ENABLE_SWAPFS
 142         if ((fs->super->s_magic == ext2fs_swab16(EXT2_SUPER_MAGIC)) ||
 143             (fs->flags & EXT2_FLAG_SWAP_BYTES)) {
 144                 fs->flags |= EXT2_FLAG_SWAP_BYTES;
 145
 146                 ext2fs_swap_super(fs->super);
 147         }
 148 #endif
 149
 150         if (fs->super->s_magic != EXT2_SUPER_MAGIC) {
 151                 retval = EXT2_ET_BAD_MAGIC;
 152                 goto cleanup;
 153         }
 154         if (fs->super->s_rev_level > EXT2_LIB_CURRENT_REV) {
 155                 retval = EXT2_ET_REV_TOO_HIGH;
 156                 goto cleanup;
 157         }
 158
 159         /*
 160          * Check for feature set incompatibility
 161          */
 162         if (!(flags & EXT2_FLAG_FORCE)) {
 163                 if (fs->super->s_feature_incompat &
 164                     ~EXT2_LIB_FEATURE_INCOMPAT_SUPP) {
 165                         retval = EXT2_ET_UNSUPP_FEATURE;
 166                         goto cleanup;
 167                 }
 168                 if ((flags & EXT2_FLAG_RW) &&
 169                     (fs->super->s_feature_ro_compat &
 170                      ~EXT2_LIB_FEATURE_RO_COMPAT_SUPP)) {
 171                         retval = EXT2_ET_RO_UNSUPP_FEATURE;
 172                         goto cleanup;
 173                 }
 174                 if (!(flags & EXT2_FLAG_JOURNAL_DEV_OK) &&
 175                     (fs->super->s_feature_incompat &
 176                      EXT3_FEATURE_INCOMPAT_JOURNAL_DEV)) {
 177                         retval = EXT2_ET_UNSUPP_FEATURE;
 178                         goto cleanup;
 179                 }
 180         }
 181
 182         fs->blocksize = EXT2_BLOCK_SIZE(fs->super);
 183         if (fs->blocksize == 0) {
 184                 retval = EXT2_ET_CORRUPT_SUPERBLOCK;
 185                 goto cleanup;
 186         }
 187         fs->fragsize = EXT2_FRAG_SIZE(fs->super);
 188         fs->inode_blocks_per_group = ((fs->super->s_inodes_per_group *
 189                                        EXT2_INODE_SIZE(fs->super) +
 190                                        EXT2_BLOCK_SIZE(fs->super) - 1) /
 191                                       EXT2_BLOCK_SIZE(fs->super));
 192         if (block_size) {
 193                 if (block_size != fs->blocksize) {
 194                         retval = EXT2_ET_UNEXPECTED_BLOCK_SIZE;
 195                         goto cleanup;
 196                 }
 197         }
 198         /*
 199          * Set the blocksize to the filesystem's blocksize.
 200          */
 201         io_channel_set_blksize(fs->io, fs->blocksize);
 202
 203         /*
 204          * If this is an external journal device, don't try to read
 205          * the group descriptors, because they're not there.
 206          */
 207         if (fs->super->s_feature_incompat &
 208             EXT3_FEATURE_INCOMPAT_JOURNAL_DEV) {
 209                 fs->group_desc_count = 0;
 210                 *ret_fs = fs;
 211                 return 0;
 212         }
 213
 214         /*
 215          * Read group descriptors
 216          */
 217         blocks_per_group = EXT2_BLOCKS_PER_GROUP(fs->super);
 218         if (blocks_per_group == 0 ||
 219             blocks_per_group > EXT2_MAX_BLOCKS_PER_GROUP(fs->super) ||
 220             fs->inode_blocks_per_group > EXT2_MAX_INODES_PER_GROUP(fs->super)) {
 221                 retval = EXT2_ET_CORRUPT_SUPERBLOCK;
 222                 goto cleanup;
 223         }
 224         fs->group_desc_count = (fs->super->s_blocks_count -
 225                                 fs->super->s_first_data_block +
 226                                 blocks_per_group - 1) / blocks_per_group;
 227         fs->desc_blocks = (fs->group_desc_count +
 228                            EXT2_DESC_PER_BLOCK(fs->super) - 1)
 229                 / EXT2_DESC_PER_BLOCK(fs->super);
 230         retval = ext2fs_get_mem(fs->desc_blocks * fs->blocksize,
 231                                 (void **) &fs->group_desc);
 232         if (retval)
 233                 goto cleanup;
 234         if (!group_block)
 235                 group_block = fs->super->s_first_data_block;
 236         dest = (char *) fs->group_desc;
 237         groups_per_block = fs->blocksize / sizeof(struct ext2_group_desc);
 238         for (i=0 ; i < fs->desc_blocks; i++) {
 239                 blk = ext2fs_descriptor_block_loc(fs, group_block, i);
 240                 retval = io_channel_read_blk(fs->io, blk, 1, dest);
 241                 if (retval)
 242                         goto cleanup;
 243 #ifdef EXT2FS_ENABLE_SWAPFS
 244                 if (fs->flags & EXT2_FLAG_SWAP_BYTES) {
 245                         gdp = (struct ext2_group_desc *) dest;
 246                         for (j=0; j < groups_per_block; j++)
 247                                 ext2fs_swap_group_desc(gdp++);
 248                 }
 249 #endif
 250                 dest += fs->blocksize;
 251         }
 252
 253         *ret_fs = fs;
 254         return 0;
 255 cleanup:
 256         ext2fs_free(fs);
 257         return retval;
 258 }
 259