misc/findsuper.c

/*
 * findsuper --- quick hacked up program to find ext2 superblocks.
 *
 * This is a hack, and really shouldn't be installed anywhere.  If you
 * need a program which does this sort of functionality, please try
 * using gpart program.
 *
 * Portions Copyright 1998-2000, Theodore Ts'o.
 * 
 * Well, here's my linux version of findsuper.
 * I'm sure you coulda done it faster.  :)
 * IMHO there isn't as much interesting data to print in the
 * linux superblock as there is in the SunOS superblock--disk geometry is
 * not there...and linux seems to update the dates in all the superblocks.
 * SunOS doesn't ever touch the backup superblocks after the fs is created,
 * as far as I can tell, so the date is more interesting IMHO and certainly
 * marks which superblocks are backup ones.
 *
 * I wanted to add msdos support, but I couldn't make heads or tails
 * of the kernel include files to find anything I could look for in msdos.
 * 
 * Reading every block of a Sun partition is fairly quick.  Doing the
 * same under linux (slower hardware I suppose) just isn't the same.
 * It might be more useful to default to reading the first (second?) block
 * on each cyl; however, if the disk geometry is wrong, this is useless.
 * But ya could still get the cyl size to print the numbers as cyls instead
 * of blocks...
 *
 * run this as (for example)
 *   findsuper /dev/hda
 *   findsuper /dev/hda 437760 1024   (my disk has cyls of 855*512)
 *
 * I suppose the next step is to figgure out a way to determine if
 * the block found is the first superblock somehow, and if so, build
 * a partition table from the superblocks found... but this is still
 * useful as is.
 *
 *		Steve
 * ssd@nevets.oau.org
 * ssd@mae.engr.ucf.edu
 *
 * Additional notes by Andreas Dilger <adilger@turbolinux.com>:
 * - fixed to support > 2G devices by using lseek64
 * - add reliability checking for the superblock to avoid random garbage
 * - add adaptive progress meter
 *
 * It _should_ also handle signals and tell you the ending block, so
 * that you can resume at a later time, but it doesn't yet...
 *
 * Note that gpart does not appear to find all superblocks that aren't aligned
 * with the start of a possible partition, so it is not useful in systems
 * with LVM or similar setups which don't use fat partition alignment.
 *
 * %Begin-Header%
 * This file may be redistributed under the terms of the GNU Public
 * License.
 * %End-Header%
 */

/*
 * Documentation addendum added by Andreas dwguest@win.tue.nl/aeb@cwi.nl
 * 
 * The program findsuper is a utility that scans a disk and finds
 * copies of ext2 superblocks (by checking for the ext2 signature
 * 
 * For each superblock found, it prints the offset in bytes, the
 * offset in 1024-byte blocks, the size of ext2 partition in fs
 * blocks, the filesystem blocksize (in bytes), the block group number
 * (always 0 for older ext2 systems), and a timestamp (s_mtime).
 * 
 * This program can be used to retrieve partitions that have been
 * lost.  The superblock for block group 0 is found 1 block (2
 * sectors) after the partition start.
 * 
 * For new systems that have a block group number in the superblock it
 * is immediately clear which superblock is the first of a partition.
 * For old systems where no group numbers are given, the first
 * superblock can be recognised by the timestamp: all superblock
 * copies have the creation time in s_mtime, except the first, which
 * has the last time e2fsck or tune2fs wrote to the filesystem.
 * 
 */

#define _FILE_OFFSET_BITS 64

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <time.h>

#include "ext2fs/ext2_fs.h"
#include "nls-enable.h"

#undef DEBUG

#ifdef DEBUG
#define WHY(fmt, arg...) { printf("\r%Ld: " fmt, sk, ##arg) ; continue; }
#else
#define WHY(fmt, arg...) { continue; }
#endif

int main(int argc, char *argv[])
{
	int skiprate=512;		/* one sector */
	loff_t sk=0, skl=0;
	int fd;
	char *s;
	time_t tm, last = time(0);
	loff_t interval = 1024 * 1024;

	struct ext2_super_block ext2;
	/* interesting fields: EXT2_SUPER_MAGIC
	 *      s_blocks_count s_log_block_size s_mtime s_magic s_lastcheck */

#ifdef ENABLE_NLS
	setlocale(LC_MESSAGES, "");
	setlocale(LC_CTYPE, "");
	bindtextdomain(NLS_CAT_NAME, LOCALEDIR);
	textdomain(NLS_CAT_NAME);
#endif
	if (argc<2) {
		fprintf(stderr,
			_("Usage:  findsuper device [skipbytes [startkb]]\n"));
		exit(1);
	}
	if (argc>2)
		skiprate = strtol(argv[2], &s, 0);
	if (s == argv[2]) {
		fprintf(stderr,_("skiprate should be a number, not %s\n"), s);
		exit(1);
	}
	if (skiprate & 0x1ff) {
		fprintf(stderr,
			_("skipbytes must be a multiple of the sector size\n"));
		exit(2);
	}
	if (argc>3)
		sk = skl = strtoll(argv[3], &s, 0) << 10;
	if (s == argv[3]) {
		fprintf(stderr,_("startkb should be a number, not %s\n"), s);
		exit(1);
	}
	if (sk < 0) {
		fprintf(stderr,_("startkb should be positive, not %Ld\n"), sk);
		exit(1);
	}
	fd = open(argv[1], O_RDONLY);
	if (fd < 0) {
		perror(argv[1]);
		exit(1);
	}
 
	/* Now, go looking for the superblock ! */
	printf(_("starting at %Ld, with %d byte increments\n"), sk, skiprate);
	printf(_("       thisoff     block fs_blk_sz  blksz grp last_mount\n"));
	for (; lseek64(fd, sk, SEEK_SET) != -1 &&
	       read(fd, &ext2, 512) == 512; sk += skiprate) {

		if (sk && !(sk & (interval - 1))) {
			time_t now, diff;

			now = time(0);
			diff = now - last;

			if (diff > 0) {
				s = ctime(&now);
				s[24] = 0;
				printf("\r%14Ld: %8LdkB/s @ %s", sk,
				       (((sk - skl)) / diff) >> 10, s);
				fflush(stdout);
			}
			if (diff < 5)
				interval <<= 1;
			else if (diff > 20)
				interval >>= 1;
			last = now;
			skl = sk;
		}
		if (ext2.s_magic != EXT2_SUPER_MAGIC)
			continue;
		if (ext2.s_log_block_size > 4)
			WHY("log block size > 4 (%d)\n", ext2.s_log_block_size);
		if (ext2.s_r_blocks_count > ext2.s_blocks_count)
			WHY("r_blocks_count > blocks_count (%d > %d)\n",
			    ext2.s_r_blocks_count, ext2.s_blocks_count);
		if (ext2.s_free_blocks_count > ext2.s_blocks_count)
			WHY("free_blocks_count > blocks_count\n (%d > %d)\n",
			    ext2.s_free_blocks_count, ext2.s_blocks_count);
		if (ext2.s_free_inodes_count > ext2.s_inodes_count)
			WHY("free_inodes_count > inodes_count (%d > %d)\n",
			    ext2.s_free_inodes_count, ext2.s_inodes_count);

		tm = ext2.s_mtime;
		s=ctime(&tm);
		s[24]=0;
		printf("\r%14Ld %9Ld %9d %5d %4d %s\n",
		       sk, sk >> 10, ext2.s_blocks_count,
		       1 << (ext2.s_log_block_size + 10),
		       ext2.s_block_group_nr, s);
	}
	printf(_("\n%14Ld: finished with errno %d\n"), sk, errno);
	close(fd);

	return errno;
}