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      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 (at) 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 #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_bitmap(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 #include "e2p/e2p.h"
    147 
    148 void print_csum(const char *msg, ext2_filsys fs, dgrp_t group)
    149 {
    150 	__u16 crc1, crc2, crc3;
    151 	dgrp_t swabgroup;
    152 	struct ext2_group_desc *desc = &fs->group_desc[group];
    153 	struct ext2_super_block *sb = fs->super;
    154 
    155 #ifdef WORDS_BIGENDIAN
    156 	struct ext2_group_desc swabdesc = fs->group_desc[group];
    157 
    158 	/* Have to swab back to little-endian to do the checksum */
    159 	ext2fs_swap_group_desc(&swabdesc);
    160 	desc = &swabdesc;
    161 
    162 	swabgroup = ext2fs_swab32(group);
    163 #else
    164 	swabgroup = group;
    165 #endif
    166 
    167 	crc1 = ext2fs_crc16(~0, sb->s_uuid, sizeof(fs->super->s_uuid));
    168 	crc2 = ext2fs_crc16(crc1, &swabgroup, sizeof(swabgroup));
    169 	crc3 = ext2fs_crc16(crc2, desc,
    170 			    offsetof(struct ext2_group_desc, bg_checksum));
    171 	printf("%s: UUID %s(%04x), grp %u(%04x): %04x=%04x\n",
    172 	       msg, e2p_uuid2str(sb->s_uuid), crc1, group, crc2,crc3,
    173 	       ext2fs_group_desc_csum(fs, group));
    174 }
    175 
    176 unsigned char sb_uuid[16] = { 0x4f, 0x25, 0xe8, 0xcf, 0xe7, 0x97, 0x48, 0x23,
    177 			      0xbe, 0xfa, 0xa7, 0x88, 0x4b, 0xae, 0xec, 0xdb };
    178 
    179 int main(int argc, char **argv)
    180 {
    181 	struct ext2_super_block param;
    182 	errcode_t		retval;
    183 	ext2_filsys		fs;
    184 	int			i;
    185 	__u16 csum1, csum2, csum_known = 0xd3a4;
    186 
    187 	memset(&param, 0, sizeof(param));
    188 	param.s_blocks_count = 32768;
    189 
    190 	retval = ext2fs_initialize("test fs", 0, &param,
    191 				   test_io_manager, &fs);
    192 	if (retval) {
    193 		com_err("setup", retval,
    194 			"While initializing filesystem");
    195 		exit(1);
    196 	}
    197 	memcpy(fs->super->s_uuid, sb_uuid, 16);
    198 	fs->super->s_feature_ro_compat = EXT4_FEATURE_RO_COMPAT_GDT_CSUM;
    199 
    200 	for (i=0; i < fs->group_desc_count; i++) {
    201 		fs->group_desc[i].bg_block_bitmap = 124;
    202 		fs->group_desc[i].bg_inode_bitmap = 125;
    203 		fs->group_desc[i].bg_inode_table = 126;
    204 		fs->group_desc[i].bg_free_blocks_count = 31119;
    205 		fs->group_desc[i].bg_free_inodes_count = 15701;
    206 		fs->group_desc[i].bg_used_dirs_count = 2;
    207 		fs->group_desc[i].bg_flags = 0;
    208 	};
    209 
    210 	csum1 = ext2fs_group_desc_csum(fs, 0);
    211 	print_csum("csum0000", fs, 0);
    212 
    213 	if (csum1 != csum_known) {
    214 		printf("checksum for group 0 should be %04x\n", csum_known);
    215 		exit(1);
    216 	}
    217 	csum2 = ext2fs_group_desc_csum(fs, 1);
    218 	print_csum("csum0001", fs, 1);
    219 	if (csum1 == csum2) {
    220 		printf("checksums for different groups shouldn't match\n");
    221 		exit(1);
    222 	}
    223 	csum2 = ext2fs_group_desc_csum(fs, 2);
    224 	print_csum("csumffff", fs, 2);
    225 	if (csum1 == csum2) {
    226 		printf("checksums for different groups shouldn't match\n");
    227 		exit(1);
    228 	}
    229 	fs->group_desc[0].bg_checksum = csum1;
    230 	csum2 = ext2fs_group_desc_csum(fs, 0);
    231 	print_csum("csum_set", fs, 0);
    232 	if (csum1 != csum2) {
    233 		printf("checksums should not depend on checksum field\n");
    234 		exit(1);
    235 	}
    236 	if (!ext2fs_group_desc_csum_verify(fs, 0)) {
    237 		printf("checksums should verify against gd_checksum\n");
    238 		exit(1);
    239 	}
    240 	memset(fs->super->s_uuid, 0x30, sizeof(fs->super->s_uuid));
    241 	print_csum("new_uuid", fs, 0);
    242 	if (ext2fs_group_desc_csum_verify(fs, 0) != 0) {
    243 		printf("checksums for different filesystems shouldn't match\n");
    244 		exit(1);
    245 	}
    246 	csum1 = fs->group_desc[0].bg_checksum = ext2fs_group_desc_csum(fs, 0);
    247 	print_csum("csum_new", fs, 0);
    248 	fs->group_desc[0].bg_free_blocks_count = 1;
    249 	csum2 = ext2fs_group_desc_csum(fs, 0);
    250 	print_csum("csum_blk", fs, 0);
    251 	if (csum1 == csum2) {
    252 		printf("checksums for different data shouldn't match\n");
    253 		exit(1);
    254 	}
    255 
    256 	return 0;
    257 }
    258 #endif
    259