findsuper.c revision 598ff01414fc01bc12be69c0fa1e852c4a93864d 
1/*
2 * findsuper --- quick hacked up program to find ext2 superblocks.
3 *
4 * This is a hack, and really shouldn't be installed anywhere.  If you
5 * need a program which does this sort of functionality, please try
6 * using gpart program.
7 *
8 * Portions Copyright 1998-2000, Theodore Ts'o.
9 *
10 * Well, here's my linux version of findsuper.
11 * I'm sure you coulda done it faster.  :)
12 * IMHO there isn't as much interesting data to print in the
13 * linux superblock as there is in the SunOS superblock--disk geometry is
14 * not there...and linux seems to update the dates in all the superblocks.
15 * SunOS doesn't ever touch the backup superblocks after the fs is created,
16 * as far as I can tell, so the date is more interesting IMHO and certainly
17 * marks which superblocks are backup ones.
18 *
19 * I wanted to add msdos support, but I couldn't make heads or tails
20 * of the kernel include files to find anything I could look for in msdos.
21 *
22 * Reading every block of a Sun partition is fairly quick.  Doing the
23 * same under linux (slower hardware I suppose) just isn't the same.
24 * It might be more useful to default to reading the first (second?) block
25 * on each cyl; however, if the disk geometry is wrong, this is useless.
26 * But ya could still get the cyl size to print the numbers as cyls instead
27 * of blocks...
28 *
29 * run this as (for example)
30 *   findsuper /dev/hda
31 *   findsuper /dev/hda 437760 1024   (my disk has cyls of 855*512)
32 *
33 * I suppose the next step is to figgure out a way to determine if
34 * the block found is the first superblock somehow, and if so, build
35 * a partition table from the superblocks found... but this is still
36 * useful as is.
37 *
38 *		Steve
39 * ssd@nevets.oau.org
40 * ssd@mae.engr.ucf.edu
41 *
42 * Additional notes by Andreas Dilger <adilger@turbolinux.com>:
43 * - fixed to support > 2G devices by using lseek64
44 * - add reliability checking for the superblock to avoid random garbage
45 * - add adaptive progress meter
46 *
47 * It _should_ also handle signals and tell you the ending block, so
48 * that you can resume at a later time, but it doesn't yet...
49 *
50 * Note that gpart does not appear to find all superblocks that aren't aligned
51 * with the start of a possible partition, so it is not useful in systems
52 * with LVM or similar setups which don't use fat partition alignment.
53 *
54 * %Begin-Header%
55 * This file may be redistributed under the terms of the GNU Public
56 * License.
57 * %End-Header%
58 */
59
60/*
61 * Documentation addendum added by Andreas dwguest@win.tue.nl/aeb@cwi.nl
62 *
63 * The program findsuper is a utility that scans a disk and finds
64 * copies of ext2 superblocks (by checking for the ext2 signature).
65 *
66 * For each superblock found, it prints the offset in bytes, the
67 * offset in 1024-byte blocks, the size of the ext2 partition in fs
68 * blocks, the filesystem blocksize (in bytes), the block group number
69 * (always 0 for older ext2 systems), and a timestamp (s_mtime).
70 *
71 * This program can be used to retrieve partitions that have been
72 * lost.  The superblock for block group 0 is found 1 block (2
73 * sectors) after the partition start.
74 *
75 * For new systems that have a block group number in the superblock it
76 * is immediately clear which superblock is the first of a partition.
77 * For old systems where no group numbers are given, the first
78 * superblock can be recognised by the timestamp: all superblock
79 * copies have the creation time in s_mtime, except the first, which
80 * has the last time e2fsck or tune2fs wrote to the filesystem.
81 *
82 */
83
84#define _FILE_OFFSET_BITS 64
85
86#include <stdio.h>
87#include <stdlib.h>
88#include <string.h>
89#include <unistd.h>
90#include <errno.h>
91#include <fcntl.h>
92#include <time.h>
93
94#include "ext2fs/ext2_fs.h"
95#include "nls-enable.h"
96
97#undef DEBUG
98
99#ifdef DEBUG
100#define WHY(fmt, arg...) { printf("\r%Ld: " fmt, sk, ##arg) ; continue; }
101#else
102#define WHY(fmt, arg...) { continue; }
103#endif
104
105int main(int argc, char *argv[])
106{
107	int skiprate=512;		/* one sector */
108	loff_t sk=0, skl=0;
109	int fd;
110	char *s;
111	time_t tm, last = time(0);
112	loff_t interval = 1024 * 1024;
113
114	struct ext2_super_block ext2;
115	/* interesting fields: EXT2_SUPER_MAGIC
116	 *      s_blocks_count s_log_block_size s_mtime s_magic s_lastcheck */
117
118#ifdef ENABLE_NLS
119	setlocale(LC_MESSAGES, "");
120	setlocale(LC_CTYPE, "");
121	bindtextdomain(NLS_CAT_NAME, LOCALEDIR);
122	textdomain(NLS_CAT_NAME);
123#endif
124	if (argc<2) {
125		fprintf(stderr,
126			_("Usage:  findsuper device [skipbytes [startkb]]\n"));
127		exit(1);
128	}
129	if (argc>2)
130		skiprate = strtol(argv[2], &s, 0);
131	if (s == argv[2]) {
132		fprintf(stderr,_("skipbytes should be a number, not %s\n"), s);
133		exit(1);
134	}
135	if (skiprate & 0x1ff) {
136		fprintf(stderr,
137			_("skipbytes must be a multiple of the sector size\n"));
138		exit(2);
139	}
140	if (argc>3)
141		sk = skl = strtoll(argv[3], &s, 0) << 10;
142	if (s == argv[3]) {
143		fprintf(stderr,_("startkb should be a number, not %s\n"), s);
144		exit(1);
145	}
146	if (sk < 0) {
147		fprintf(stderr,_("startkb should be positive, not %Ld\n"), sk);
148		exit(1);
149	}
150	fd = open(argv[1], O_RDONLY);
151	if (fd < 0) {
152		perror(argv[1]);
153		exit(1);
154	}
155
156	/* Now, go looking for the superblock! */
157	printf(_("starting at %Ld, with %d byte increments\n"), sk, skiprate);
158	printf(_("       thisoff     block fs_blk_sz  blksz grp last_mount\n"));
159	for (; lseek64(fd, sk, SEEK_SET) != -1 &&
160	       read(fd, &ext2, 512) == 512; sk += skiprate) {
161
162		if (sk && !(sk & (interval - 1))) {
163			time_t now, diff;
164
165			now = time(0);
166			diff = now - last;
167
168			if (diff > 0) {
169				s = ctime(&now);
170				s[24] = 0;
171				printf("\r%14Ld: %8LdkB/s @ %s", sk,
172				       (((sk - skl)) / diff) >> 10, s);
173				fflush(stdout);
174			}
175			if (diff < 5)
176				interval <<= 1;
177			else if (diff > 20)
178				interval >>= 1;
179			last = now;
180			skl = sk;
181		}
182		if (ext2.s_magic != EXT2_SUPER_MAGIC)
183			continue;
184		if (ext2.s_log_block_size > 4)
185			WHY("log block size > 4 (%d)\n", ext2.s_log_block_size);
186		if (ext2.s_r_blocks_count > ext2.s_blocks_count)
187			WHY("r_blocks_count > blocks_count (%d > %d)\n",
188			    ext2.s_r_blocks_count, ext2.s_blocks_count);
189		if (ext2.s_free_blocks_count > ext2.s_blocks_count)
190			WHY("free_blocks_count > blocks_count\n (%d > %d)\n",
191			    ext2.s_free_blocks_count, ext2.s_blocks_count);
192		if (ext2.s_free_inodes_count > ext2.s_inodes_count)
193			WHY("free_inodes_count > inodes_count (%d > %d)\n",
194			    ext2.s_free_inodes_count, ext2.s_inodes_count);
195
196		tm = ext2.s_mtime;
197		s=ctime(&tm);
198		s[24]=0;
199		printf("\r%14Ld %9Ld %9d %5d %4d %s\n",
200		       sk, sk >> 10, ext2.s_blocks_count,
201		       1 << (ext2.s_log_block_size + 10),
202		       ext2.s_block_group_nr, s);
203	}
204	printf(_("\n%14Ld: finished with errno %d\n"), sk, errno);
205	close(fd);
206
207	return errno;
208}
209