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 Public
   9  * License.
  10  * %End-Header%
  11  */
  12
  13 #if HAVE_SYS_TYPES_H
  14 #include <sys/types.h>
  15 #endif
  16
  17 #include "ext2_fs.h"
  18 #include "ext2fs.h"
  19 #include "crc16.h"
  20 #include <assert.h>
  21
  22 #ifndef offsetof
  23 #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
  24 #endif
  25
  26 #ifdef DEBUG
  27 #define STATIC
  28 #else
  29 #define STATIC static
  30 #endif
  31
  32 STATIC __u16 ext2fs_group_desc_csum(ext2_filsys fs, dgrp_t group)
  33 {
  34         __u16 crc = 0;
  35         struct ext2_group_desc *desc;
  36
  37         desc = &fs->group_desc[group];
  38
  39         if (fs->super->s_feature_ro_compat & EXT4_FEATURE_RO_COMPAT_GDT_CSUM) {
  40                 int offset = offsetof(struct ext2_group_desc, bg_checksum);
  41
  42 #ifdef WORDS_BIGENDIAN
  43                 struct ext2_group_desc swabdesc = *desc;
  44
  45                 /* Have to swab back to little-endian to do the checksum */
  46                 ext2fs_swap_group_desc(&swabdesc);
  47                 desc = &swabdesc;
  48
  49                 group = ext2fs_swab32(group);
  50 #endif
  51                 crc = ext2fs_crc16(~0, fs->super->s_uuid,
  52                                    sizeof(fs->super->s_uuid));
  53                 crc = ext2fs_crc16(crc, &group, sizeof(group));
  54                 crc = ext2fs_crc16(crc, desc, offset);
  55                 offset += sizeof(desc->bg_checksum); /* skip checksum */
  56                 assert(offset == sizeof(*desc));
  57                 /* for checksum of struct ext4_group_desc do the rest...*/
  58                 if (offset < fs->super->s_desc_size) {
  59                         crc = ext2fs_crc16(crc, (char *)desc + offset,
  60                                     fs->super->s_desc_size - offset);
  61                 }
  62         }
  63
  64         return crc;
  65 }
  66
  67 int ext2fs_group_desc_csum_verify(ext2_filsys fs, dgrp_t group)
  68 {
  69         if (EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
  70                                        EXT4_FEATURE_RO_COMPAT_GDT_CSUM) &&
  71             (fs->group_desc[group].bg_checksum !=
  72              ext2fs_group_desc_csum(fs, group)))
  73                 return 0;
  74
  75         return 1;
  76 }
  77
  78 void ext2fs_group_desc_csum_set(ext2_filsys fs, dgrp_t group)
  79 {
  80         if (EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
  81                                        EXT4_FEATURE_RO_COMPAT_GDT_CSUM))
  82                 fs->group_desc[group].bg_checksum =
  83                         ext2fs_group_desc_csum(fs, group);
  84 }
  85
  86 static __u32 find_last_inode_ingrp(ext2fs_inode_bitmap bitmap,
  87                                    __u32 inodes_per_grp, dgrp_t grp_no)
  88 {
  89         ext2_ino_t i, start_ino, end_ino;
  90
  91         start_ino = grp_no * inodes_per_grp + 1;
  92         end_ino = start_ino + inodes_per_grp - 1;
  93
  94         for (i = end_ino; i >= start_ino; i--) {
  95                 if (ext2fs_fast_test_inode_bitmap2(bitmap, i))
  96                         return i - start_ino + 1;
  97         }
  98         return inodes_per_grp;
  99 }
 100
 101 /* update the bitmap flags, set the itable high watermark, and calculate
 102  * checksums for the group descriptors */
 103 errcode_t ext2fs_set_gdt_csum(ext2_filsys fs)
 104 {
 105         struct ext2_super_block *sb = fs->super;
 106         struct ext2_group_desc *bg = fs->group_desc;
 107         int dirty = 0;
 108         dgrp_t i;
 109
 110         if (!fs->inode_map)
 111                 return EXT2_ET_NO_INODE_BITMAP;
 112
 113         if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
 114                                         EXT4_FEATURE_RO_COMPAT_GDT_CSUM))
 115                 return 0;
 116
 117         for (i = 0; i < fs->group_desc_count; i++, bg++) {
 118                 int old_csum = bg->bg_checksum;
 119                 int old_unused = bg->bg_itable_unused;
 120                 int old_flags = bg->bg_flags;
 121
 122                 if (bg->bg_free_inodes_count == sb->s_inodes_per_group) {
 123                         bg->bg_flags |= EXT2_BG_INODE_UNINIT;
 124                         bg->bg_itable_unused = sb->s_inodes_per_group;
 125                 } else {
 126                         bg->bg_flags &= ~EXT2_BG_INODE_UNINIT;
 127                         bg->bg_itable_unused = sb->s_inodes_per_group -
 128                                 find_last_inode_ingrp(fs->inode_map,
 129                                                       sb->s_inodes_per_group,i);
 130                 }
 131
 132                 ext2fs_group_desc_csum_set(fs, i);
 133                 if (old_flags != bg->bg_flags)
 134                         dirty = 1;
 135                 if (old_unused != bg->bg_itable_unused)
 136                         dirty = 1;
 137                 if (old_csum != bg->bg_checksum)
 138                         dirty = 1;
 139         }
 140         if (dirty)
 141                 ext2fs_mark_super_dirty(fs);
 142         return 0;
 143 }
 144
 145 #ifdef DEBUG
 146 void print_csum(const char *msg, ext2_filsys fs, dgrp_t group)
 147 {
 148         __u16 crc1, crc2, crc3;
 149         dgrp_t swabgroup;
 150         struct ext2_group_desc *desc = &fs->group_desc[group];
 151         struct ext2_super_block *sb = fs->super;
 152
 153 #ifdef WORDS_BIGENDIAN
 154         struct ext2_group_desc swabdesc = fs->group_desc[group];
 155
 156         /* Have to swab back to little-endian to do the checksum */
 157         ext2fs_swap_group_desc(&swabdesc);
 158         desc = &swabdesc;
 159
 160         swabgroup = ext2fs_swab32(group);
 161 #else
 162         swabgroup = group;
 163 #endif
 164
 165         crc1 = ext2fs_crc16(~0, sb->s_uuid, sizeof(fs->super->s_uuid));
 166         crc2 = ext2fs_crc16(crc1, &swabgroup, sizeof(swabgroup));
 167         crc3 = ext2fs_crc16(crc2, desc,
 168                             offsetof(struct ext2_group_desc, bg_checksum));
 169         printf("%s: UUID %016Lx%016Lx(%04x), grp %u(%04x): %04x=%04x\n",
 170                msg, *(long long *)&sb->s_uuid, *(long long *)&sb->s_uuid[8],
 171                crc1, group, crc2, crc3, ext2fs_group_desc_csum(fs, group));
 172 }
 173
 174 unsigned char sb_uuid[16] = { 0x4f, 0x25, 0xe8, 0xcf, 0xe7, 0x97, 0x48, 0x23,
 175                               0xbe, 0xfa, 0xa7, 0x88, 0x4b, 0xae, 0xec, 0xdb };
 176
 177 int main(int argc, char **argv)
 178 {
 179         struct ext2_super_block param;
 180         errcode_t               retval;
 181         ext2_filsys             fs;
 182         int                     i;
 183         __u16 csum1, csum2, csum_known = 0xd3a4;
 184
 185         memset(&param, 0, sizeof(param));
 186         ext2fs_blocks_count_set(&param, 32768);
 187
 188         retval = ext2fs_initialize("test fs", EXT2_FLAG_64BITS, &param,
 189                                    test_io_manager, &fs);
 190         if (retval) {
 191                 com_err("setup", retval,
 192                         "While initializing filesystem");
 193                 exit(1);
 194         }
 195         memcpy(fs->super->s_uuid, sb_uuid, 16);
 196         fs->super->s_feature_ro_compat = EXT4_FEATURE_RO_COMPAT_GDT_CSUM;
 197
 198         for (i=0; i < fs->group_desc_count; i++) {
 199                 fs->group_desc[i].bg_block_bitmap = 124;
 200                 fs->group_desc[i].bg_inode_bitmap = 125;
 201                 fs->group_desc[i].bg_inode_table = 126;
 202                 fs->group_desc[i].bg_free_blocks_count = 31119;
 203                 fs->group_desc[i].bg_free_inodes_count = 15701;
 204                 fs->group_desc[i].bg_used_dirs_count = 2;
 205                 fs->group_desc[i].bg_flags = 0;
 206         };
 207
 208         csum1 = ext2fs_group_desc_csum(fs, 0);
 209         print_csum("csum0000", fs, 0);
 210
 211         if (csum1 != csum_known) {
 212                 printf("checksum for group 0 should be %04x\n", csum_known);
 213                 exit(1);
 214         }
 215         csum2 = ext2fs_group_desc_csum(fs, 1);
 216         print_csum("csum0001", fs, 1);
 217         if (csum1 == csum2) {
 218                 printf("checksums for different groups shouldn't match\n");
 219                 exit(1);
 220         }
 221         csum2 = ext2fs_group_desc_csum(fs, 2);
 222         print_csum("csumffff", fs, 2);
 223         if (csum1 == csum2) {
 224                 printf("checksums for different groups shouldn't match\n");
 225                 exit(1);
 226         }
 227         fs->group_desc[0].bg_checksum = csum1;
 228         csum2 = ext2fs_group_desc_csum(fs, 0);
 229         print_csum("csum_set", fs, 0);
 230         if (csum1 != csum2) {
 231                 printf("checksums should not depend on checksum field\n");
 232                 exit(1);
 233         }
 234         if (!ext2fs_group_desc_csum_verify(fs, 0)) {
 235                 printf("checksums should verify against gd_checksum\n");
 236                 exit(1);
 237         }
 238         memset(fs->super->s_uuid, 0x30, sizeof(fs->super->s_uuid));
 239         print_csum("new_uuid", fs, 0);
 240         if (ext2fs_group_desc_csum_verify(fs, 0) != 0) {
 241                 printf("checksums for different filesystems shouldn't match\n");
 242                 exit(1);
 243         }
 244         csum1 = fs->group_desc[0].bg_checksum = ext2fs_group_desc_csum(fs, 0);
 245         print_csum("csum_new", fs, 0);
 246         fs->group_desc[0].bg_free_blocks_count = 1;
 247         csum2 = ext2fs_group_desc_csum(fs, 0);
 248         print_csum("csum_blk", fs, 0);
 249         if (csum1 == csum2) {
 250                 printf("checksums for different data shouldn't match\n");
 251                 exit(1);
 252         }
 253
 254         return 0;
 255 }
 256 #endif