lib/ext2fs/csum.c

   1 /*
   2  * csum.c --- checksumming of ext3 structures
   3  *
   4  * Copyright (C) 2006 Cluster File Systems, Inc.
   5  * Copyright (C) 2006, 2007 by Andreas Dilger <adilger@clusterfs.com>
   6  *
   7  * %Begin-Header%
   8  * This file may be redistributed under the terms of the GNU Library
   9  * General Public License, version 2.
  10  * %End-Header%
  11  */
  12
  13 #include "config.h"
  14 #if HAVE_SYS_TYPES_H
  15 #include <sys/types.h>
  16 #endif
  17
  18 #include "ext2_fs.h"
  19 #include "ext2fs.h"
  20 #include "crc16.h"
  21 #include <assert.h>
  22
  23 #ifndef offsetof
  24 #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
  25 #endif
  26
  27 #ifdef DEBUG
  28 #define STATIC
  29 #else
  30 #define STATIC static
  31 #endif
  32
  33 __u16 ext2fs_group_desc_csum(ext2_filsys fs, dgrp_t group)
  34 {
  35         struct ext2_group_desc *desc = ext2fs_group_desc(fs, fs->group_desc,
  36                                                          group);
  37         size_t size = EXT2_DESC_SIZE(fs->super);
  38         size_t offset;
  39         __u16 crc = 0;
  40
  41         if (fs->super->s_feature_ro_compat & EXT4_FEATURE_RO_COMPAT_GDT_CSUM) {
  42                 size_t offset = offsetof(struct ext2_group_desc, bg_checksum);
  43
  44 #ifdef WORDS_BIGENDIAN
  45                 struct ext4_group_desc swabdesc;
  46                 size_t save_size = size;
  47                 const size_t ext4_bg_size = sizeof(struct ext4_group_desc);
  48                 struct ext2_group_desc *save_desc = desc;
  49
  50                 /* Have to swab back to little-endian to do the checksum */
  51                 if (size > ext4_bg_size)
  52                         size = ext4_bg_size;
  53                 memcpy(&swabdesc, desc, size);
  54                 ext2fs_swap_group_desc2(fs,
  55                                         (struct ext2_group_desc *) &swabdesc);
  56                 desc = (struct ext2_group_desc *) &swabdesc;
  57
  58                 group = ext2fs_swab32(group);
  59 #endif
  60                 crc = ext2fs_crc16(~0, fs->super->s_uuid,
  61                                    sizeof(fs->super->s_uuid));
  62                 crc = ext2fs_crc16(crc, &group, sizeof(group));
  63                 crc = ext2fs_crc16(crc, desc, offset);
  64                 offset += sizeof(desc->bg_checksum); /* skip checksum */
  65                 /* for checksum of struct ext4_group_desc do the rest...*/
  66                 if (offset < size) {
  67                         crc = ext2fs_crc16(crc, (char *)desc + offset,
  68                                            size - offset);
  69                 }
  70 #ifdef WORDS_BIGENDIAN
  71                 /*
  72                  * If the size of the bg descriptor is greater than 64
  73                  * bytes, which is the size of the traditional ext4 bg
  74                  * descriptor, checksum the rest of the descriptor here
  75                  */
  76                 if (save_size > ext4_bg_size)
  77                         crc = ext2fs_crc16(crc,
  78                                            (char *)save_desc + ext4_bg_size,
  79                                            save_size - ext4_bg_size);
  80 #endif
  81         }
  82
  83         return crc;
  84 }
  85
  86 int ext2fs_group_desc_csum_verify(ext2_filsys fs, dgrp_t group)
  87 {
  88         if (EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
  89                                        EXT4_FEATURE_RO_COMPAT_GDT_CSUM) &&
  90             (ext2fs_bg_checksum(fs, group) !=
  91              ext2fs_group_desc_csum(fs, group)))
  92                 return 0;
  93
  94         return 1;
  95 }
  96
  97 void ext2fs_group_desc_csum_set(ext2_filsys fs, dgrp_t group)
  98 {
  99         if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
 100                                         EXT4_FEATURE_RO_COMPAT_GDT_CSUM))
 101                 return;
 102
 103         /* ext2fs_bg_checksum_set() sets the actual checksum field but
 104          * does not calculate the checksum itself. */
 105         ext2fs_bg_checksum_set(fs, group, ext2fs_group_desc_csum(fs, group));
 106 }
 107
 108 static __u32 find_last_inode_ingrp(ext2fs_inode_bitmap bitmap,
 109                                    __u32 inodes_per_grp, dgrp_t grp_no)
 110 {
 111         ext2_ino_t i, start_ino, end_ino;
 112
 113         start_ino = grp_no * inodes_per_grp + 1;
 114         end_ino = start_ino + inodes_per_grp - 1;
 115
 116         for (i = end_ino; i >= start_ino; i--) {
 117                 if (ext2fs_fast_test_inode_bitmap2(bitmap, i))
 118                         return i - start_ino + 1;
 119         }
 120         return inodes_per_grp;
 121 }
 122
 123 /* update the bitmap flags, set the itable high watermark, and calculate
 124  * checksums for the group descriptors */
 125 errcode_t ext2fs_set_gdt_csum(ext2_filsys fs)
 126 {
 127         struct ext2_super_block *sb = fs->super;
 128         int dirty = 0;
 129         dgrp_t i;
 130
 131         if (!fs->inode_map)
 132                 return EXT2_ET_NO_INODE_BITMAP;
 133
 134         if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
 135                                         EXT4_FEATURE_RO_COMPAT_GDT_CSUM))
 136                 return 0;
 137
 138         for (i = 0; i < fs->group_desc_count; i++) {
 139                 __u32 old_csum = ext2fs_bg_checksum(fs, i);
 140                 __u32 old_unused = ext2fs_bg_itable_unused(fs, i);
 141                 __u32 old_flags = ext2fs_bg_flags(fs, i);
 142                 __u32 old_free_inodes_count = ext2fs_bg_free_inodes_count(fs, i);
 143
 144                 if (old_free_inodes_count == sb->s_inodes_per_group) {
 145                         ext2fs_bg_flags_set(fs, i, EXT2_BG_INODE_UNINIT);
 146                         ext2fs_bg_itable_unused_set(fs, i, sb->s_inodes_per_group);
 147                 } else {
 148                         int unused =
 149                                 sb->s_inodes_per_group -
 150                                 find_last_inode_ingrp(fs->inode_map,
 151                                                       sb->s_inodes_per_group, i);
 152
 153                         ext2fs_bg_flags_clear(fs, i, EXT2_BG_INODE_UNINIT);
 154                         ext2fs_bg_itable_unused_set(fs, i, unused);
 155                 }
 156
 157                 ext2fs_group_desc_csum_set(fs, i);
 158                 if (old_flags != ext2fs_bg_flags(fs, i))
 159                         dirty = 1;
 160                 if (old_unused != ext2fs_bg_itable_unused(fs, i))
 161                         dirty = 1;
 162                 if (old_csum != ext2fs_bg_checksum(fs, i))
 163                         dirty = 1;
 164         }
 165         if (dirty)
 166                 ext2fs_mark_super_dirty(fs);
 167         return 0;
 168 }
 169
 170 #ifdef DEBUG
 171 #include "e2p/e2p.h"
 172
 173 void print_csum(const char *msg, ext2_filsys fs, dgrp_t group)
 174 {
 175         __u16 crc1, crc2, crc3;
 176         dgrp_t swabgroup;
 177         struct ext2_group_desc *desc = ext2fs_group_desc(fs, fs->group_desc,
 178                                                          group);
 179         size_t size = EXT2_DESC_SIZE(fs->super);
 180         struct ext2_super_block *sb = fs->super;
 181         int offset = offsetof(struct ext2_group_desc, bg_checksum);
 182 #ifdef WORDS_BIGENDIAN
 183         struct ext4_group_desc swabdesc;
 184         struct ext2_group_desc *save_desc = desc;
 185         const size_t ext4_bg_size = sizeof(struct ext4_group_desc);
 186         size_t save_size = size;
 187 #endif
 188
 189 #ifdef WORDS_BIGENDIAN
 190         /* Have to swab back to little-endian to do the checksum */
 191         if (size > ext4_bg_size)
 192                 size = ext4_bg_size;
 193         memcpy(&swabdesc, desc, size);
 194         ext2fs_swap_group_desc2(fs, (struct ext2_group_desc *) &swabdesc);
 195         desc = (struct ext2_group_desc *) &swabdesc;
 196
 197         swabgroup = ext2fs_swab32(group);
 198 #else
 199         swabgroup = group;
 200 #endif
 201
 202         crc1 = ext2fs_crc16(~0, sb->s_uuid, sizeof(fs->super->s_uuid));
 203         crc2 = ext2fs_crc16(crc1, &swabgroup, sizeof(swabgroup));
 204         crc3 = ext2fs_crc16(crc2, desc, offset);
 205         offset += sizeof(desc->bg_checksum); /* skip checksum */
 206         /* for checksum of struct ext4_group_desc do the rest...*/
 207         if (offset < size)
 208                 crc3 = ext2fs_crc16(crc3, (char *)desc + offset, size - offset);
 209 #ifdef WORDS_BIGENDIAN
 210         if (save_size > ext4_bg_size)
 211                 crc3 = ext2fs_crc16(crc3, (char *)save_desc + ext4_bg_size,
 212                                     save_size - ext4_bg_size);
 213 #endif
 214
 215         printf("%s UUID %s=%04x, grp %u=%04x: %04x=%04x\n",
 216                msg, e2p_uuid2str(sb->s_uuid), crc1, group, crc2, crc3,
 217                ext2fs_group_desc_csum(fs, group));
 218 }
 219
 220 unsigned char sb_uuid[16] = { 0x4f, 0x25, 0xe8, 0xcf, 0xe7, 0x97, 0x48, 0x23,
 221                               0xbe, 0xfa, 0xa7, 0x88, 0x4b, 0xae, 0xec, 0xdb };
 222
 223 int main(int argc, char **argv)
 224 {
 225         struct ext2_super_block param;
 226         errcode_t               retval;
 227         ext2_filsys             fs;
 228         int                     i;
 229         __u16 csum1, csum2, csum_known = 0xd3a4;
 230
 231         memset(&param, 0, sizeof(param));
 232         ext2fs_blocks_count_set(&param, 32768);
 233 #if 0
 234         param.s_feature_incompat |= EXT4_FEATURE_INCOMPAT_64BIT;
 235         param.s_desc_size = 128;
 236         csum_known = 0x5b6e;
 237 #endif
 238
 239         retval = ext2fs_initialize("test fs", EXT2_FLAG_64BITS, &param,
 240                                    test_io_manager, &fs);
 241         if (retval) {
 242                 com_err("setup", retval,
 243                         "While initializing filesystem");
 244                 exit(1);
 245         }
 246         memcpy(fs->super->s_uuid, sb_uuid, 16);
 247         fs->super->s_feature_ro_compat = EXT4_FEATURE_RO_COMPAT_GDT_CSUM;
 248
 249         for (i=0; i < fs->group_desc_count; i++) {
 250                 ext2fs_block_bitmap_loc_set(fs, i, 124);
 251                 ext2fs_inode_bitmap_loc_set(fs, i, 125);
 252                 ext2fs_inode_table_loc_set(fs, i, 126);
 253                 ext2fs_bg_free_blocks_count_set(fs, i, 31119);
 254                 ext2fs_bg_free_inodes_count_set(fs, i, 15701);
 255                 ext2fs_bg_used_dirs_count_set(fs, i, 2);
 256                 ext2fs_bg_flags_zap(fs, i);
 257         };
 258
 259         csum1 = ext2fs_group_desc_csum(fs, 0);
 260         print_csum("csum0000", fs, 0);
 261
 262         if (csum1 != csum_known) {
 263                 printf("checksum for group 0 should be %04x\n", csum_known);
 264                 exit(1);
 265         }
 266         csum2 = ext2fs_group_desc_csum(fs, 1);
 267         print_csum("csum0001", fs, 1);
 268         if (csum1 == csum2) {
 269                 printf("checksums for different groups shouldn't match\n");
 270                 exit(1);
 271         }
 272         csum2 = ext2fs_group_desc_csum(fs, 2);
 273         print_csum("csumffff", fs, 2);
 274         if (csum1 == csum2) {
 275                 printf("checksums for different groups shouldn't match\n");
 276                 exit(1);
 277         }
 278         ext2fs_bg_checksum_set(fs, 0, csum1);
 279         csum2 = ext2fs_group_desc_csum(fs, 0);
 280         print_csum("csum_set", fs, 0);
 281         if (csum1 != csum2) {
 282                 printf("checksums should not depend on checksum field\n");
 283                 exit(1);
 284         }
 285         if (!ext2fs_group_desc_csum_verify(fs, 0)) {
 286                 printf("checksums should verify against gd_checksum\n");
 287                 exit(1);
 288         }
 289         memset(fs->super->s_uuid, 0x30, sizeof(fs->super->s_uuid));
 290         print_csum("new_uuid", fs, 0);
 291         if (ext2fs_group_desc_csum_verify(fs, 0) != 0) {
 292                 printf("checksums for different filesystems shouldn't match\n");
 293                 exit(1);
 294         }
 295         csum1 = ext2fs_group_desc_csum(fs, 0);
 296         ext2fs_bg_checksum_set(fs, 0, csum1);
 297         print_csum("csum_new", fs, 0);
 298         ext2fs_bg_free_blocks_count_set(fs, 0, 1);
 299         csum2 = ext2fs_group_desc_csum(fs, 0);
 300         print_csum("csum_blk", fs, 0);
 301         if (csum1 == csum2) {
 302                 printf("checksums for different data shouldn't match\n");
 303                 exit(1);
 304         }
 305
 306         return 0;
 307 }
 308 #endif