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         __u16 crc = 0;
  36         struct ext2_group_desc *desc;
  37         size_t size;
  38
  39         size = fs->super->s_desc_size;
  40         if (size < EXT2_MIN_DESC_SIZE)
  41                 size = EXT2_MIN_DESC_SIZE;
  42         if (size > sizeof(struct ext4_group_desc)) {
  43                 printf("%s: illegal s_desc_size(%zd)\n", __func__, size);
  44                 size = sizeof(struct ext4_group_desc);
  45         }
  46
  47         desc = ext2fs_group_desc(fs, fs->group_desc, group);
  48
  49         if (fs->super->s_feature_ro_compat & EXT4_FEATURE_RO_COMPAT_GDT_CSUM) {
  50                 size_t offset = offsetof(struct ext2_group_desc, bg_checksum);
  51
  52 #ifdef WORDS_BIGENDIAN
  53                 struct ext4_group_desc swabdesc;
  54
  55                 /* Have to swab back to little-endian to do the checksum */
  56                 memcpy(&swabdesc, desc, size);
  57                 ext2fs_swap_group_desc2(fs,
  58                                         (struct ext2_group_desc *) &swabdesc);
  59                 desc = (struct ext2_group_desc *) &swabdesc;
  60
  61                 group = ext2fs_swab32(group);
  62 #endif
  63                 crc = ext2fs_crc16(~0, fs->super->s_uuid,
  64                                    sizeof(fs->super->s_uuid));
  65                 crc = ext2fs_crc16(crc, &group, sizeof(group));
  66                 crc = ext2fs_crc16(crc, desc, offset);
  67                 offset += sizeof(desc->bg_checksum); /* skip checksum */
  68                 /* for checksum of struct ext4_group_desc do the rest...*/
  69                 if (offset < size) {
  70                         crc = ext2fs_crc16(crc, (char *)desc + offset,
  71                                            size - offset);
  72                 }
  73         }
  74
  75         return crc;
  76 }
  77
  78 int ext2fs_group_desc_csum_verify(ext2_filsys fs, dgrp_t group)
  79 {
  80         if (EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
  81                                        EXT4_FEATURE_RO_COMPAT_GDT_CSUM) &&
  82             (ext2fs_bg_checksum(fs, group) !=
  83              ext2fs_group_desc_csum(fs, group)))
  84                 return 0;
  85
  86         return 1;
  87 }
  88
  89 void ext2fs_group_desc_csum_set(ext2_filsys fs, dgrp_t group)
  90 {
  91         if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
  92                                         EXT4_FEATURE_RO_COMPAT_GDT_CSUM))
  93                 return;
  94
  95         /* ext2fs_bg_checksum_set() sets the actual checksum field but
  96          * does not calculate the checksum itself. */
  97         ext2fs_bg_checksum_set(fs, group, ext2fs_group_desc_csum(fs, group));
  98 }
  99
 100 static __u32 find_last_inode_ingrp(ext2fs_inode_bitmap bitmap,
 101                                    __u32 inodes_per_grp, dgrp_t grp_no)
 102 {
 103         ext2_ino_t i, start_ino, end_ino;
 104
 105         start_ino = grp_no * inodes_per_grp + 1;
 106         end_ino = start_ino + inodes_per_grp - 1;
 107
 108         for (i = end_ino; i >= start_ino; i--) {
 109                 if (ext2fs_fast_test_inode_bitmap2(bitmap, i))
 110                         return i - start_ino + 1;
 111         }
 112         return inodes_per_grp;
 113 }
 114
 115 /* update the bitmap flags, set the itable high watermark, and calculate
 116  * checksums for the group descriptors */
 117 errcode_t ext2fs_set_gdt_csum(ext2_filsys fs)
 118 {
 119         struct ext2_super_block *sb = fs->super;
 120         int dirty = 0;
 121         dgrp_t i;
 122
 123         if (!fs->inode_map)
 124                 return EXT2_ET_NO_INODE_BITMAP;
 125
 126         if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
 127                                         EXT4_FEATURE_RO_COMPAT_GDT_CSUM))
 128                 return 0;
 129
 130         for (i = 0; i < fs->group_desc_count; i++) {
 131                 __u32 old_csum = ext2fs_bg_checksum(fs, i);
 132                 __u32 old_unused = ext2fs_bg_itable_unused(fs, i);
 133                 __u32 old_flags = ext2fs_bg_flags(fs, i);
 134                 __u32 old_free_inodes_count = ext2fs_bg_free_inodes_count(fs, i);
 135
 136                 if (old_free_inodes_count == sb->s_inodes_per_group) {
 137                         ext2fs_bg_flags_set(fs, i, EXT2_BG_INODE_UNINIT);
 138                         ext2fs_bg_itable_unused_set(fs, i, sb->s_inodes_per_group);
 139                 } else {
 140                         int unused =
 141                                 sb->s_inodes_per_group -
 142                                 find_last_inode_ingrp(fs->inode_map,
 143                                                       sb->s_inodes_per_group, i);
 144
 145                         ext2fs_bg_flags_clear(fs, i, EXT2_BG_INODE_UNINIT);
 146                         ext2fs_bg_itable_unused_set(fs, i, unused);
 147                 }
 148
 149                 ext2fs_group_desc_csum_set(fs, i);
 150                 if (old_flags != ext2fs_bg_flags(fs, i))
 151                         dirty = 1;
 152                 if (old_unused != ext2fs_bg_itable_unused(fs, i))
 153                         dirty = 1;
 154                 if (old_csum != ext2fs_bg_checksum(fs, i))
 155                         dirty = 1;
 156         }
 157         if (dirty)
 158                 ext2fs_mark_super_dirty(fs);
 159         return 0;
 160 }
 161
 162 #ifdef DEBUG
 163 #include "e2p/e2p.h"
 164
 165 void print_csum(const char *msg, ext2_filsys fs, dgrp_t group)
 166 {
 167         __u16 crc1, crc2, crc3;
 168         dgrp_t swabgroup;
 169         struct ext2_group_desc *desc = ext2fs_group_desc(fs, fs->group_desc, group);
 170         size_t size;
 171         struct ext2_super_block *sb = fs->super;
 172         int offset = offsetof(struct ext2_group_desc, bg_checksum);
 173 #ifdef WORDS_BIGENDIAN
 174         struct ext4_group_desc swabdesc;
 175 #endif
 176
 177         size = fs->super->s_desc_size;
 178         if (size < EXT2_MIN_DESC_SIZE)
 179                 size = EXT2_MIN_DESC_SIZE;
 180         if (size > sizeof(struct ext4_group_desc))
 181                 size = sizeof(struct ext4_group_desc);
 182 #ifdef WORDS_BIGENDIAN
 183         /* Have to swab back to little-endian to do the checksum */
 184         memcpy(&swabdesc, desc, size);
 185         ext2fs_swap_group_desc2(fs, (struct ext2_group_desc *) &swabdesc);
 186         desc = (struct ext2_group_desc *) &swabdesc;
 187
 188         swabgroup = ext2fs_swab32(group);
 189 #else
 190         swabgroup = group;
 191 #endif
 192
 193         crc1 = ext2fs_crc16(~0, sb->s_uuid, sizeof(fs->super->s_uuid));
 194         crc2 = ext2fs_crc16(crc1, &swabgroup, sizeof(swabgroup));
 195         crc3 = ext2fs_crc16(crc2, desc, offset);
 196         offset += sizeof(desc->bg_checksum); /* skip checksum */
 197         /* for checksum of struct ext4_group_desc do the rest...*/
 198         if (offset < size)
 199                 crc3 = ext2fs_crc16(crc3, (char *)desc + offset, size - offset);
 200
 201         printf("%s: UUID %s(%04x), grp %u(%04x): %04x=%04x\n",
 202                msg, e2p_uuid2str(sb->s_uuid), crc1, group, crc2, crc3,
 203                ext2fs_group_desc_csum(fs, group));
 204 }
 205
 206 unsigned char sb_uuid[16] = { 0x4f, 0x25, 0xe8, 0xcf, 0xe7, 0x97, 0x48, 0x23,
 207                               0xbe, 0xfa, 0xa7, 0x88, 0x4b, 0xae, 0xec, 0xdb };
 208
 209 int main(int argc, char **argv)
 210 {
 211         struct ext2_super_block param;
 212         errcode_t               retval;
 213         ext2_filsys             fs;
 214         int                     i;
 215         __u16 csum1, csum2, csum_known = 0xd3a4;
 216
 217         memset(&param, 0, sizeof(param));
 218         ext2fs_blocks_count_set(&param, 32768);
 219
 220         retval = ext2fs_initialize("test fs", EXT2_FLAG_64BITS, &param,
 221                                    test_io_manager, &fs);
 222         if (retval) {
 223                 com_err("setup", retval,
 224                         "While initializing filesystem");
 225                 exit(1);
 226         }
 227         memcpy(fs->super->s_uuid, sb_uuid, 16);
 228         fs->super->s_feature_ro_compat = EXT4_FEATURE_RO_COMPAT_GDT_CSUM;
 229
 230         for (i=0; i < fs->group_desc_count; i++) {
 231                 ext2fs_block_bitmap_loc_set(fs, i, 124);
 232                 ext2fs_inode_bitmap_loc_set(fs, i, 125);
 233                 ext2fs_inode_table_loc_set(fs, i, 126);
 234                 ext2fs_bg_free_blocks_count_set(fs, i, 31119);
 235                 ext2fs_bg_free_inodes_count_set(fs, i, 15701);
 236                 ext2fs_bg_used_dirs_count_set(fs, i, 2);
 237                 ext2fs_bg_flags_zap(fs, i);
 238         };
 239
 240         csum1 = ext2fs_group_desc_csum(fs, 0);
 241         print_csum("csum0000", fs, 0);
 242
 243         if (csum1 != csum_known) {
 244                 printf("checksum for group 0 should be %04x\n", csum_known);
 245                 exit(1);
 246         }
 247         csum2 = ext2fs_group_desc_csum(fs, 1);
 248         print_csum("csum0001", fs, 1);
 249         if (csum1 == csum2) {
 250                 printf("checksums for different groups shouldn't match\n");
 251                 exit(1);
 252         }
 253         csum2 = ext2fs_group_desc_csum(fs, 2);
 254         print_csum("csumffff", fs, 2);
 255         if (csum1 == csum2) {
 256                 printf("checksums for different groups shouldn't match\n");
 257                 exit(1);
 258         }
 259         ext2fs_bg_checksum_set(fs, 0, csum1);
 260         csum2 = ext2fs_group_desc_csum(fs, 0);
 261         print_csum("csum_set", fs, 0);
 262         if (csum1 != csum2) {
 263                 printf("checksums should not depend on checksum field\n");
 264                 exit(1);
 265         }
 266         if (!ext2fs_group_desc_csum_verify(fs, 0)) {
 267                 printf("checksums should verify against gd_checksum\n");
 268                 exit(1);
 269         }
 270         memset(fs->super->s_uuid, 0x30, sizeof(fs->super->s_uuid));
 271         print_csum("new_uuid", fs, 0);
 272         if (ext2fs_group_desc_csum_verify(fs, 0) != 0) {
 273                 printf("checksums for different filesystems shouldn't match\n");
 274                 exit(1);
 275         }
 276         csum1 = ext2fs_group_desc_csum(fs, 0);
 277         ext2fs_bg_checksum_set(fs, 0, csum1);
 278         print_csum("csum_new", fs, 0);
 279         ext2fs_bg_free_blocks_count_set(fs, 0, 1);
 280         csum2 = ext2fs_group_desc_csum(fs, 0);
 281         print_csum("csum_blk", fs, 0);
 282         if (csum1 == csum2) {
 283                 printf("checksums for different data shouldn't match\n");
 284                 exit(1);
 285         }
 286
 287         return 0;
 288 }
 289 #endif