1 /* vi: set sw=4 ts=4: */
3 * mkfs_ext2: utility to create EXT2 filesystem
4 * inspired by genext2fs
6 * Busybox'ed (2009) by Vladimir Dronnikov <dronnikov@gmail.com>
8 * Licensed under GPLv2, see file LICENSE in this tarball for details.
12 #include <linux/ext2_fs.h>
13 #include <sys/user.h> /* PAGE_SIZE */
15 # define PAGE_SIZE 4096
17 #include "volume_id/volume_id_internal.h"
19 #define ENABLE_FEATURE_MKFS_EXT2_RESERVED_GDT 0
20 #define ENABLE_FEATURE_MKFS_EXT2_DIR_INDEX 1
23 #define s_reserved_gdt_blocks s_padding1
24 #define s_mkfs_time s_reserved[0]
25 #define s_flags s_reserved[22]
26 #define EXT2_HASH_HALF_MD4 1
27 #define EXT2_FLAGS_SIGNED_HASH 0x0001
29 // whiteout: for writable overlays
30 //#define LINUX_S_IFWHT 0160000
31 //#define EXT2_FEATURE_INCOMPAT_WHITEOUT 0x0020
34 char BUG_wrong_field_size(void);
35 #define STORE_LE(field, value) \
37 if (sizeof(field) == 4) \
38 field = cpu_to_le32(value); \
39 else if (sizeof(field) == 2) \
40 field = cpu_to_le16(value); \
41 else if (sizeof(field) == 1) \
44 BUG_wrong_field_size(); \
47 #define FETCH_LE32(field) \
48 (sizeof(field) == 4 ? cpu_to_le32(field) : BUG_wrong_field_size())
50 // All fields are little-endian
69 static unsigned int_log2(unsigned arg)
72 while ((arg >>= 1) != 0)
77 // taken from mkfs_minix.c. libbb candidate?
78 // why "uint64_t size"? we never use it for anything >32 bits
79 static uint32_t div_roundup(uint64_t size, uint32_t n)
82 uint32_t res = size / n;
88 static void allocate(uint8_t *bitmap, uint32_t blocksize, uint32_t start, uint32_t end)
92 //bb_info_msg("ALLOC: [%u][%u][%u]: [%u-%u]:=[%x],[%x]", blocksize, start, end, start/8, blocksize - end/8 - 1, (1 << (start & 7)) - 1, (uint8_t)(0xFF00 >> (end & 7)));
93 memset(bitmap, 0, blocksize);
95 memset(bitmap, 0xFF, i);
96 bitmap[i] = (1 << (start & 7)) - 1; //0..7 => 00000000..01111111
98 bitmap[blocksize - i - 1] |= 0x7F00 >> (end & 7); //0..7 => 00000000..11111110
99 memset(bitmap + blocksize - i, 0xFF, i); // N.B. no overflow here!
102 static uint32_t has_super(uint32_t x)
104 // 0, 1 and powers of 3, 5, 7 up to 2^32 limit
105 static const uint32_t supers[] = {
106 0, 1, 3, 5, 7, 9, 25, 27, 49, 81, 125, 243, 343, 625, 729,
107 2187, 2401, 3125, 6561, 15625, 16807, 19683, 59049, 78125,
108 117649, 177147, 390625, 531441, 823543, 1594323, 1953125,
109 4782969, 5764801, 9765625, 14348907, 40353607, 43046721,
110 48828125, 129140163, 244140625, 282475249, 387420489,
111 1162261467, 1220703125, 1977326743, 3486784401/* >2^31 */,
113 const uint32_t *sp = supers + ARRAY_SIZE(supers);
123 /* Standard mke2fs 1.41.9:
124 * Usage: mke2fs [-c|-l filename] [-b block-size] [-f fragment-size]
125 * [-i bytes-per-inode] [-I inode-size] [-J journal-options]
126 * [-G meta group size] [-N number-of-inodes]
127 * [-m reserved-blocks-percentage] [-o creator-os]
128 * [-g blocks-per-group] [-L volume-label] [-M last-mounted-directory]
129 * [-O feature[,...]] [-r fs-revision] [-E extended-option[,...]]
130 * [-T fs-type] [-U UUID] [-jnqvFSV] device [blocks-count]
132 // N.B. not commented below options are taken and silently ignored
136 OPT_b = 1 << 2, // block size, in bytes
138 OPT_i = 1 << 4, // bytes per inode
143 OPT_m = 1 << 9, // percentage of blocks reserved for superuser
146 OPT_L = 1 << 12, // label
154 OPT_n = 1 << 20, // dry run: do not write anything
159 //OPT_V = 1 << 25, // -V version. bbox applets don't support that
162 #define fd 3 /* predefined output descriptor */
164 static void PUT(uint64_t off, void *buf, uint32_t size)
166 // bb_info_msg("PUT[%llu]:[%u]", off, size);
167 xlseek(fd, off, SEEK_SET);
168 xwrite(fd, buf, size);
171 int mkfs_ext2_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
172 int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv)
176 unsigned blocksize, blocksize_log2;
177 unsigned reserved_percent = 5;
178 unsigned long long kilobytes;
179 uint32_t nblocks, nblocks_full, nreserved;
181 uint32_t bytes_per_inode;
182 uint32_t first_data_block;
183 uint32_t inodes_per_group;
184 uint32_t gdtsz, itsz;
187 const char *label = "";
189 struct ext2_super_block *sb; // superblock
190 struct ext2_group_desc *gd; // group descriptors
191 struct ext2_inode *inode;
192 struct ext2_dir *dir;
195 opt_complementary = "-1:b+:m+:i+";
196 opts = getopt32(argv, "cl:b:f:i:I:J:G:N:m:o:g:L:M:O:r:E:T:U:jnqvFS",
197 NULL, &bs, NULL, &bpi, NULL, NULL, NULL, NULL,
198 &reserved_percent, NULL, NULL, &label, NULL, NULL, NULL, NULL, NULL, NULL);
199 argv += optind; // argv[0] -- device
201 // check the device is a block device
202 xmove_fd(xopen(argv[0], O_WRONLY), fd);
204 if (!S_ISBLK(st.st_mode) && !(opts & OPT_F))
205 bb_error_msg_and_die("not a block device");
207 // check if it is mounted
208 // N.B. what if we format a file? find_mount_point will return false negative since
209 // it is loop block device which mounted!
210 if (find_mount_point(argv[0], 0))
211 bb_error_msg_and_die("can't format mounted filesystem");
213 // open the device, get size in kbytes
215 kilobytes = xatoull(argv[1]);
217 kilobytes = (uoff_t)xlseek(fd, 0, SEEK_END) / 1024;
220 bytes_per_inode = 16384;
221 if (kilobytes < 512*1024)
222 bytes_per_inode = 4096;
223 if (kilobytes < 3*1024)
224 bytes_per_inode = 8192;
226 bytes_per_inode = bpi;
228 // Determine block size
229 // block size is a multiple of 1024
231 if (kilobytes >= 512*1024) // mke2fs 1.41.9 compat
233 if (EXT2_MAX_BLOCK_SIZE > 4096) {
234 // kilobytes >> 22 == size in 4gigabyte chunks.
235 // if size >= 16k gigs, blocksize must be increased.
236 // Try "mke2fs -F image $((16 * 1024*1024*1024))"
237 while ((kilobytes >> 22) >= blocksize)
242 if (blocksize < EXT2_MIN_BLOCK_SIZE
243 || blocksize > EXT2_MAX_BLOCK_SIZE
244 || (blocksize & (blocksize - 1)) // not power of 2
246 bb_error_msg_and_die("blocksize %u is bad", blocksize);
248 // number of bits in one block, i.e. 8*blocksize
249 #define blocks_per_group (8 * blocksize)
250 first_data_block = (EXT2_MIN_BLOCK_SIZE == blocksize);
251 blocksize_log2 = int_log2(blocksize);
253 // Determine number of blocks
254 kilobytes >>= (blocksize_log2 - EXT2_MIN_BLOCK_LOG_SIZE);
256 if (nblocks != kilobytes)
257 bb_error_msg_and_die("block count doesn't fit in 32 bits");
258 #define kilobytes kilobytes_unused_after_this
260 // if (blocksize < PAGE_SIZE)
261 // nblocks &= ~((PAGE_SIZE >> blocksize_log2)-1);
262 // Experimentally, standard mke2fs won't work on images smaller than 60k
264 bb_error_msg_and_die("need >= 60 blocks");
266 // How many reserved blocks?
267 if (reserved_percent > 50)
268 bb_error_msg_and_die("-%c is bad", 'm');
269 //nreserved = div_roundup((uint64_t) nblocks * reserved_percent, 100);
270 nreserved = (uint64_t)nblocks * reserved_percent / 100;
272 // N.B. killing e2fsprogs feature! Unused blocks don't account in calculations
273 nblocks_full = nblocks;
275 // If last block group is too small, nblocks may be decreased in order
276 // to discard it, and control returns here to recalculate some
278 // Note: blocksize and bytes_per_inode are never recalculated.
280 // N.B. a block group can have no more than blocks_per_group blocks
281 ngroups = div_roundup(nblocks - first_data_block, blocks_per_group);
283 bb_error_msg_and_die("ngroups");
285 gdtsz = div_roundup(ngroups, blocksize / sizeof(*gd));
286 // TODO: reserved blocks must be marked as such in the bitmaps,
287 // or resulting filesystem is corrupt
288 if (ENABLE_FEATURE_MKFS_EXT2_RESERVED_GDT) {
290 * From e2fsprogs: Calculate the number of GDT blocks to reserve for online
292 * The absolute maximum number of GDT blocks we can reserve is determined by
293 * the number of block pointers that can fit into a single block.
294 * We set it at 1024x the current filesystem size, or
295 * the upper block count limit (2^32), whichever is lower.
297 uint32_t rgdtsz = 0xFFFFFFFF; // maximum block number
298 if (nblocks < rgdtsz / 1024)
299 rgdtsz = nblocks * 1024;
300 rgdtsz = div_roundup(rgdtsz - first_data_block, blocks_per_group);
301 rgdtsz = div_roundup(rgdtsz, blocksize / sizeof(*gd)) - gdtsz;
302 if (rgdtsz > blocksize / sizeof(uint32_t))
303 rgdtsz = blocksize / sizeof(uint32_t);
304 //TODO: STORE_LE(sb->s_reserved_gdt_blocks, rgdtsz);
309 // N.B. e2fsprogs does as follows!
310 // ninodes is the total number of inodes (files) in the file system
311 uint32_t ninodes = ((uint64_t) nblocks_full * blocksize) / bytes_per_inode;
312 uint32_t overhead, remainder;
313 if (ninodes < EXT2_GOOD_OLD_FIRST_INO+1)
314 ninodes = EXT2_GOOD_OLD_FIRST_INO+1;
315 inodes_per_group = div_roundup(ninodes, ngroups);
316 // minimum number because the first EXT2_GOOD_OLD_FIRST_INO-1 are reserved
317 if (inodes_per_group < 16)
318 inodes_per_group = 16;
320 // a block group can have no more than 8*blocksize inodes
321 if (inodes_per_group > blocks_per_group)
322 inodes_per_group = blocks_per_group;
323 // adjust inodes per group so they completely fill the inode table blocks in the descriptor
324 inodes_per_group = (div_roundup(inodes_per_group * sizeof(*inode), blocksize) * blocksize) / sizeof(*inode);
325 // make sure the number of inodes per group is a multiple of 8
326 inodes_per_group &= ~7;
327 itsz = div_roundup(inodes_per_group * sizeof(*inode), blocksize);
329 // the last group needs more attention: isn't it too small for possible overhead?
330 overhead = (has_super(ngroups - 1) ? (1/*sb*/ + gdtsz) : 0) + 1/*bbmp*/ + 1/*ibmp*/ + itsz;
331 remainder = (nblocks - first_data_block) % blocks_per_group;
332 if ((1 == ngroups) && remainder && (remainder < overhead))
333 bb_error_msg_and_die("way small device");
334 if (remainder && (remainder < overhead + 50/* e2fsprogs hardcoded */)) {
335 //bb_info_msg("CHOP[%u]", remainder);
336 nblocks -= remainder;
342 if (nblocks_full - nblocks)
343 printf("warning: %u blocks unused\n\n", nblocks_full - nblocks);
345 "Filesystem label=%s\n"
347 "Block size=%u (log=%u)\n"
348 "Fragment size=%u (log=%u)\n"
349 "%u inodes, %u blocks\n"
350 "%u blocks (%u%%) reserved for the super user\n"
351 "First data block=%u\n"
352 "Maximum filesystem blocks=%u\n"
354 "%u blocks per group, %u fragments per group\n"
355 "%u inodes per group"
357 , blocksize, blocksize_log2 - EXT2_MIN_BLOCK_LOG_SIZE
358 , blocksize, blocksize_log2 - EXT2_MIN_BLOCK_LOG_SIZE
359 , inodes_per_group * ngroups, nblocks
360 , nreserved, reserved_percent
362 , gdtsz * (blocksize / sizeof(*gd)) * blocks_per_group
364 , blocks_per_group, blocks_per_group
368 const char *fmt = "\nSuperblock backups stored on blocks:\n"
370 pos = first_data_block;
371 for (i = 1; i < ngroups; i++) {
372 pos += blocks_per_group;
374 printf(fmt, (unsigned)pos);
381 // dry run? -> we are done
385 // TODO: 3/5 refuse if mounted
386 // TODO: 4/5 compat options
387 // TODO: 1/5 sanity checks
388 // TODO: 0/5 more verbose error messages
389 // TODO: 4/5 bigendianness: recheck, wait for ARM reporters
390 // TODO: 2/5 reserved GDT: how to mark but not allocate?
391 // TODO: 3/5 dir_index?
393 // fill the superblock
394 sb = xzalloc(blocksize);
395 STORE_LE(sb->s_rev_level, 1); // revision 1 filesystem
396 STORE_LE(sb->s_magic, EXT2_SUPER_MAGIC);
397 STORE_LE(sb->s_inode_size, sizeof(*inode));
398 STORE_LE(sb->s_first_ino, EXT2_GOOD_OLD_FIRST_INO);
399 STORE_LE(sb->s_log_block_size, blocksize_log2 - EXT2_MIN_BLOCK_LOG_SIZE);
400 STORE_LE(sb->s_log_frag_size, blocksize_log2 - EXT2_MIN_BLOCK_LOG_SIZE);
401 // first 1024 bytes of the device are for boot record. If block size is 1024 bytes, then
402 // the first block available for data is 1, otherwise 0
403 STORE_LE(sb->s_first_data_block, first_data_block); // 0 or 1
404 // block and inode bitmaps occupy no more than one block, so maximum number of blocks is
405 STORE_LE(sb->s_blocks_per_group, blocks_per_group);
406 STORE_LE(sb->s_frags_per_group, blocks_per_group);
408 STORE_LE(sb->s_blocks_count, nblocks);
409 // reserve blocks for superuser
410 STORE_LE(sb->s_r_blocks_count, nreserved);
412 STORE_LE(sb->s_inodes_per_group, inodes_per_group);
413 STORE_LE(sb->s_inodes_count, inodes_per_group * ngroups);
414 STORE_LE(sb->s_free_inodes_count, inodes_per_group * ngroups - EXT2_GOOD_OLD_FIRST_INO);
416 timestamp = time(NULL);
417 STORE_LE(sb->s_mkfs_time, timestamp);
418 STORE_LE(sb->s_wtime, timestamp);
419 STORE_LE(sb->s_lastcheck, timestamp);
421 STORE_LE(sb->s_state, 1); // TODO: what's 1?
422 STORE_LE(sb->s_creator_os, EXT2_OS_LINUX);
423 STORE_LE(sb->s_checkinterval, 24*60*60 * 180); // 180 days
424 STORE_LE(sb->s_errors, EXT2_ERRORS_DEFAULT);
425 STORE_LE(sb->s_feature_compat, EXT2_FEATURE_COMPAT_SUPP
426 | (EXT2_FEATURE_COMPAT_RESIZE_INO * ENABLE_FEATURE_MKFS_EXT2_RESERVED_GDT)
427 | (EXT2_FEATURE_COMPAT_DIR_INDEX * ENABLE_FEATURE_MKFS_EXT2_DIR_INDEX)
429 // e2fsck from 1.41.9 doesn't like EXT2_FEATURE_INCOMPAT_WHITEOUT
430 STORE_LE(sb->s_feature_incompat, EXT2_FEATURE_INCOMPAT_FILETYPE);// | EXT2_FEATURE_INCOMPAT_WHITEOUT;
431 STORE_LE(sb->s_feature_ro_compat, EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER);
432 STORE_LE(sb->s_flags, EXT2_FLAGS_SIGNED_HASH * ENABLE_FEATURE_MKFS_EXT2_DIR_INDEX);
433 generate_uuid(sb->s_uuid);
434 if (ENABLE_FEATURE_MKFS_EXT2_DIR_INDEX) {
435 STORE_LE(sb->s_def_hash_version, EXT2_HASH_HALF_MD4);
436 generate_uuid((uint8_t *)sb->s_hash_seed);
439 * From e2fsprogs: add "jitter" to the superblock's check interval so that we
440 * don't check all the filesystems at the same time. We use a
441 * kludgy hack of using the UUID to derive a random jitter value.
443 STORE_LE(sb->s_max_mnt_count, EXT2_DFL_MAX_MNT_COUNT
444 + (sb->s_uuid[ARRAY_SIZE(sb->s_uuid)-1] % EXT2_DFL_MAX_MNT_COUNT));
447 safe_strncpy((char *)sb->s_volume_name, label, sizeof(sb->s_volume_name));
449 // fill group descriptors
450 gd = xzalloc(gdtsz * blocksize);
451 buf = xmalloc(blocksize);
452 sb->s_free_blocks_count = 0;
453 for (i = 0, pos = first_data_block, n = nblocks - first_data_block;
455 i++, pos += blocks_per_group, n -= blocks_per_group
457 uint32_t overhead = pos + (has_super(i) ? (1/*sb*/ + gdtsz) : 0);
459 STORE_LE(gd[i].bg_block_bitmap, overhead + 0);
460 STORE_LE(gd[i].bg_inode_bitmap, overhead + 1);
461 STORE_LE(gd[i].bg_inode_table, overhead + 2);
462 overhead = overhead - pos + 1/*bbmp*/ + 1/*ibmp*/ + itsz;
463 gd[i].bg_free_inodes_count = inodes_per_group;
464 //STORE_LE(gd[i].bg_used_dirs_count, 0);
465 // N.B. both root and lost+found dirs are within the first block group, thus +2
468 STORE_LE(gd[i].bg_used_dirs_count, 2);
469 gd[i].bg_free_inodes_count -= EXT2_GOOD_OLD_FIRST_INO;
472 // mark preallocated blocks as allocated
473 fb = (n < blocks_per_group ? n : blocks_per_group) - overhead;
474 //bb_info_msg("ALLOC: [%u][%u][%u]", blocksize, overhead, blocks_per_group - (fb + overhead));
475 allocate(buf, blocksize,
477 blocks_per_group - (fb + overhead)
480 PUT((uint64_t)(FETCH_LE32(gd[i].bg_block_bitmap)) * blocksize, buf, blocksize);
481 STORE_LE(gd[i].bg_free_blocks_count, fb);
483 // mark preallocated inodes as allocated
484 allocate(buf, blocksize,
485 inodes_per_group - gd[i].bg_free_inodes_count,
486 blocks_per_group - inodes_per_group
489 //PUT((uint64_t)(FETCH_LE32(gd[i].bg_block_bitmap)) * blocksize, buf, blocksize);
490 //but it's right after block bitmap, so we can just:
491 xwrite(fd, buf, blocksize);
492 STORE_LE(gd[i].bg_free_inodes_count, gd[i].bg_free_inodes_count);
494 // count overall free blocks
495 sb->s_free_blocks_count += fb;
497 STORE_LE(sb->s_free_blocks_count, sb->s_free_blocks_count);
499 // dump filesystem skeleton structures
500 // printf("Writing superblocks and filesystem accounting information: ");
501 for (i = 0, pos = first_data_block; i < ngroups; i++, pos += blocks_per_group) {
502 // dump superblock and group descriptors and their backups
504 // N.B. 1024 byte blocks are special
505 PUT(((uint64_t)pos * blocksize) + ((0 == i && 0 == first_data_block) ? 1024 : 0), sb, 1024);//blocksize);
506 PUT(((uint64_t)pos * blocksize) + blocksize, gd, gdtsz * blocksize);
511 memset(buf, 0, blocksize);
512 PUT(0, buf, 1024); // N.B. 1024 <= blocksize, so buf[0..1023] contains zeros
514 for (i = 0; i < ngroups; ++i)
515 for (n = 0; n < itsz; ++n)
516 PUT((uint64_t)(FETCH_LE32(gd[i].bg_inode_table) + n) * blocksize, buf, blocksize);
518 // prepare directory inode
519 inode = (struct ext2_inode *)buf;
520 STORE_LE(inode->i_mode, S_IFDIR | S_IRWXU | S_IRGRP | S_IROTH | S_IXGRP | S_IXOTH);
521 STORE_LE(inode->i_mtime, timestamp);
522 STORE_LE(inode->i_atime, timestamp);
523 STORE_LE(inode->i_ctime, timestamp);
524 STORE_LE(inode->i_size, blocksize);
525 // N.B. inode->i_blocks stores the number of 512 byte data blocks. Why on Earth?!
526 STORE_LE(inode->i_blocks, blocksize / 512);
528 // dump root dir inode
529 STORE_LE(inode->i_links_count, 3); // "/.", "/..", "/lost+found/.." point to this inode
530 STORE_LE(inode->i_block[0], FETCH_LE32(gd[0].bg_inode_table) + itsz);
531 PUT(((uint64_t)FETCH_LE32(gd[0].bg_inode_table) * blocksize) + (EXT2_ROOT_INO-1) * sizeof(*inode), buf, sizeof(*inode));
533 // dump lost+found dir inode
534 STORE_LE(inode->i_links_count, 2); // both "/lost+found" and "/lost+found/." point to this inode
535 STORE_LE(inode->i_block[0], inode->i_block[0]+1); // use next block
536 PUT(((uint64_t)FETCH_LE32(gd[0].bg_inode_table) * blocksize) + (EXT2_GOOD_OLD_FIRST_INO-1) * sizeof(*inode), buf, sizeof(*inode));
539 memset(buf, 0, blocksize);
540 dir = (struct ext2_dir *)buf;
542 // dump lost+found dir block
543 STORE_LE(dir->inode1, EXT2_GOOD_OLD_FIRST_INO);
544 STORE_LE(dir->rec_len1, 12);
545 STORE_LE(dir->name_len1, 1);
546 STORE_LE(dir->file_type1, EXT2_FT_DIR);
548 STORE_LE(dir->inode2, EXT2_ROOT_INO);
549 STORE_LE(dir->rec_len2, blocksize - 12);
550 STORE_LE(dir->name_len2, 2);
551 STORE_LE(dir->file_type2, EXT2_FT_DIR);
552 dir->name2[0] = '.'; dir->name2[1] = '.';
553 PUT((uint64_t)(FETCH_LE32(gd[0].bg_inode_table) + itsz + 1) * blocksize, buf, blocksize);
555 // dump root dir block
556 STORE_LE(dir->inode1, EXT2_ROOT_INO);
557 STORE_LE(dir->rec_len2, 12);
558 STORE_LE(dir->inode3, EXT2_GOOD_OLD_FIRST_INO);
559 STORE_LE(dir->rec_len3, blocksize - 12 - 12);
560 STORE_LE(dir->name_len3, 10);
561 STORE_LE(dir->file_type3, EXT2_FT_DIR);
562 strcpy(dir->name3, "lost+found");
563 PUT((uint64_t)(FETCH_LE32(gd[0].bg_inode_table) + itsz + 0) * blocksize, buf, blocksize);
567 if (ENABLE_FEATURE_CLEAN_UP) {