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