lvm2/lib/label/lvm2_label.c

/*
 * Copyright (C) 2001-2002 Sistina Software
 *
 * This file is released under the LGPL.
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>

#include "device.h"
#include "dev-cache.h"
#include "log.h"
#include "pool.h"
#include "dbg_malloc.h"
#include "filter.h"
#include "label.h"
#include "lvm2_label.h"
#include "xlate.h"

/* Label Magic is "LnXl" - error: imagination failure */
#define LABEL_MAGIC 0x6c586e4c

/* Size of blocks that dev_get_size() returns the number of */
#define BLOCK_SIZE 512

/* This is just the "struct lvm2_label" with the data pointer removed */
struct label_ondisk {
	uint32_t magic;
	uint32_t crc;
	uint64_t label1_loc;
	uint64_t label2_loc;
	uint16_t datalen;
	uint16_t pad;

	uint32_t version[3];
	char disk_type[32];
};

struct filter_private {
	void *mem;
	char disk_type[32];
	uint32_t version[3];
	int version_match;
};

/* Calculate CRC32 of a buffer */
static uint32_t crc32(uint32_t initial, const unsigned char *databuf,
		      size_t datalen)
{
	static const u_int crctab[] = {
		0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac,
		0x76dc4190, 0x6b6b51f4, 0x4db26158, 0x5005713c,
		0xedb88320, 0xf00f9344, 0xd6d6a3e8, 0xcb61b38c,
		0x9b64c2b0, 0x86d3d2d4, 0xa00ae278, 0xbdbdf21c
	};
	uint32_t idx, crc = initial;

	for (idx = 0; idx < datalen; idx++) {
		crc ^= *databuf++;
		crc = (crc >> 4) ^ crctab[crc & 0xf];
		crc = (crc >> 4) ^ crctab[crc & 0xf];
	}
	return crc;
}

/* Calculate crc */
static uint32_t calc_crc(struct label_ondisk *label, char *data)
{
	uint32_t crcval = 0xffffffff;

	crcval = crc32(crcval, (char *) &label->magic, sizeof(label->magic));
	crcval =
	    crc32(crcval, (char *) &label->label1_loc,
		  sizeof(label->label1_loc));
	crcval =
	    crc32(crcval, (char *) &label->label2_loc,
		  sizeof(label->label2_loc));
	crcval =
	    crc32(crcval, (char *) &label->datalen, sizeof(label->datalen));
	crcval =
	    crc32(crcval, (char *) &label->version, sizeof(label->version));
	crcval =
	    crc32(crcval, (char *) label->disk_type, strlen(label->disk_type));
	crcval = crc32(crcval, (char *) data, label->datalen);

	return crcval;
}

/* Calculate the locations we should find the labels in */
static inline void get_label_locations(uint64_t size, uint32_t sectsize,
				       long *first, long *second)
{
	*first = sectsize;
	*second = size * BLOCK_SIZE - sectsize;
}

/* Read a label off disk */
static int lvm2_label_read(struct labeller *l, struct device *dev,
			   struct label **label)
{
	uint64_t size;
	uint32_t sectsize;
	char *block;
	struct label_ondisk *ondisk;
	int status;
	int iter;
	long offset[2];

	if (!dev_get_size(dev, &size))
		return 0;

	if (!dev_get_sectsize(dev, &sectsize))
		return 0;

	if (!dev_open(dev, O_RDONLY))
		return 0;

	block = dbg_malloc(sectsize);
	if (!block) {
		stack;
		return 0;
	}
	ondisk = (struct label_ondisk *) block;
	get_label_locations(size, sectsize, &offset[0], &offset[1]);

	/* If the first label is bad then use the second */
	for (iter = 0; iter <= 1; iter++) {
		status = dev_read(dev, offset[iter], sectsize, block);
		if (status) {
			struct label *incore;
			int i;
			int found_nul;

			/* If the MAGIC doesn't match there's no point in
			   carrying on */
			if (xlate32(ondisk->magic) != LABEL_MAGIC)
				continue;

			/* Look for a NUL in the disk_type string so we don't
			   SEGV is something has gone horribly wrong */
			found_nul = 0;
			for (i = 0; i < sizeof(ondisk->disk_type); i++)
				if (ondisk->disk_type[i] == '\0')
					found_nul = 1;

			if (!found_nul)
				continue;

			incore = dbg_malloc(sizeof(struct label));
			if (incore == NULL) {
				return 0;
			}

			/* Copy and convert endianness */
			strncpy(incore->volume_type, ondisk->disk_type,
				sizeof(incore->volume_type));
			incore->version[0] = xlate32(ondisk->version[0]);
			incore->version[1] = xlate32(ondisk->version[1]);
			incore->version[2] = xlate32(ondisk->version[2]);
			incore->extra_len = xlate16(ondisk->datalen);
			incore->extra_info =
			    block + sizeof(struct label_ondisk);

			/* Make sure datalen is a sensible size too */
			if (incore->extra_len > sectsize)
				continue;

			/* Check Crc */
			if (xlate32(ondisk->crc) !=
			    calc_crc(ondisk, incore->extra_info)) {
				log_error
				    ("Crc %d on device %s does not match. got %x, expected %x",
				     iter, dev_name(dev), xlate32(ondisk->crc),
				     calc_crc(ondisk, incore->extra_info));
				continue;
			}

			/* Check label locations match our view of the device */
			if (xlate64(ondisk->label1_loc) != offset[0])
				log_error
				    ("Label 1 location is wrong in label %d - check block size of the device\n",
				     iter);
			if (xlate64(ondisk->label2_loc) != offset[1])
				log_error
				    ("Label 2 location is wrong in label %d - the size of the device must have changed\n",
				     iter);

			/* Copy to user's data area */
			*label = incore;
			incore->extra_info = dbg_malloc(incore->extra_len);
			if (!incore->extra_info) {
				stack;
				return 0;
			}
			memcpy(incore->extra_info,
			       block + sizeof(struct label_ondisk),
			       incore->extra_len);

			dbg_free(block);
			dev_close(dev);
			return 1;
		}
	}

	dbg_free(block);
	dev_close(dev);

	return 0;
}

/* Write a label to a device */
static int lvm2_label_write(struct labeller *l, struct device *dev,
			    struct label *label)
{
	uint64_t size;
	uint32_t sectsize;
	char *block;
	struct label_ondisk *ondisk;
	int status1, status2;
	long offset[2];

	if (!dev_get_size(dev, &size))
		return 0;

	if (!dev_get_sectsize(dev, &sectsize))
		return 0;

	/* Can the metata fit in the remaining space ? */
	if (label->extra_len > sectsize - sizeof(struct label_ondisk))
		return 0;

	block = dbg_malloc(sizeof(struct label_ondisk) + label->extra_len);
	if (!block) {
		stack;
		return 0;
	}
	ondisk = (struct label_ondisk *) block;

	get_label_locations(size, sectsize, &offset[0], &offset[1]);

	/* Make into ondisk format */
	ondisk->magic = xlate32(LABEL_MAGIC);
	ondisk->version[0] = xlate32(label->version[0]);
	ondisk->version[1] = xlate32(label->version[1]);
	ondisk->version[2] = xlate32(label->version[2]);
	ondisk->label1_loc = xlate64(offset[0]);
	ondisk->label2_loc = xlate64(offset[1]);
	ondisk->datalen = xlate16(label->extra_len);
	strncpy(ondisk->disk_type, label->volume_type,
		sizeof(ondisk->disk_type));
	memcpy(block + sizeof(struct label_ondisk), label->extra_info,
	       label->extra_len);
	ondisk->crc = xlate32(calc_crc(ondisk, label->extra_info));

	/* Write metadata to disk */
	if (!dev_open(dev, O_RDWR)) {
		dbg_free(block);
		return 0;
	}

	status1 =
	    dev_write(dev, offset[0],
		      sizeof(struct label_ondisk) + label->extra_len, block);
	if (!status1)
		log_error("Error writing label 1\n");

	/* Write another at the end of the device */
	status2 =
	    dev_write(dev, offset[1],
		      sizeof(struct label_ondisk) + label->extra_len, block);
	if (!status2) {
		char zerobuf[sizeof(struct label_ondisk)];
		log_error("Error writing label 2\n");

		/* Wipe the first label so it doesn't get confusing */
		memset(zerobuf, 0, sizeof(struct label_ondisk));
		if (!dev_write
		    (dev, offset[0], sizeof(struct label_ondisk),
		     zerobuf)) log_error("Error erasing label 1\n");
	}

	dbg_free(block);
	dev_close(dev);

	return ((status1 != 0) && (status2 != 0));
}

/* Return 1 for Yes, 0 for No */
static int lvm2_is_labelled(struct labeller *l, struct device *dev)
{
	struct label *label;
	int status;

	status = lvm2_label_read(l, dev, &label);
	if (status)
		label_free(label);

	return status;
}

/* Check the device is labelled and has the right format_type */
static int _accept_format(struct dev_filter *f, struct device *dev)
{
	struct label *l;
	int status;
	struct filter_private *fp = (struct filter_private *) f->private;

	status = lvm2_label_read(NULL, dev, &l);

	if (status) {
		if (strcmp(l->volume_type, fp->disk_type) == 0) {
			switch (fp->version_match) {
			case VERSION_MATCH_EQUAL:
				if (l->version[0] == fp->version[0] &&
				    l->version[1] == fp->version[1] &&
				    l->version[2] == fp->version[2])
					return 1;
				break;

			case VERSION_MATCH_LESSTHAN:
				if (l->version[0] == fp->version[0] &&
				    l->version[1] < fp->version[1])
					return 1;
				break;

			case VERSION_MATCH_LESSEQUAL:
				if (l->version[0] == fp->version[0] &&
				    l->version[1] <= fp->version[1])
					return 1;
				break;

			case VERSION_MATCH_ANY:
				return 1;
			}
		}
		label_free(l);
	}
	return 0;
}

/* We just want to know if it's labelled or not */
static int _accept_label(struct dev_filter *f, struct device *dev)
{
	return lvm2_is_labelled(NULL, dev);
}

static void _destroy(struct dev_filter *f)
{
	struct filter_private *fp = (struct filter_private *) f->private;
}

/* A filter to find devices with a particular label type on them */
struct dev_filter *lvm2_label_format_filter_create(char *disk_type,
						   uint32_t version[3],
						   int match_type)
{
	struct pool *mem;
	struct filter_private *fp;
	struct dev_filter *f;

	/* Validate the match type */
	if (match_type != VERSION_MATCH_EQUAL &&
	    match_type != VERSION_MATCH_LESSTHAN &&
	    match_type != VERSION_MATCH_LESSEQUAL &&
	    match_type != VERSION_MATCH_ANY)
		return 0;

	mem = pool_create(10 * 1024);
	if (!mem) {
		stack;
		return NULL;
	}

	if (!(f = pool_zalloc(mem, sizeof(*f)))) {
		stack;
		goto bad;
	}

	if (!(fp = pool_zalloc(mem, sizeof(*fp)))) {
		stack;
		goto bad;
	}

	fp->mem = mem;
	strcpy(fp->disk_type, disk_type);
	fp->version[0] = version[0];
	fp->version[1] = version[1];
	fp->version[2] = version[2];
	fp->version_match = match_type;
	f->passes_filter = _accept_format;
	f->destroy = _destroy;
	f->private = fp;

	return f;

      bad:
	pool_destroy(mem);
	return NULL;
}

/* A filter to find devices with any label on them */
struct dev_filter *lvm2_label_filter_create()
{
	struct pool *mem = pool_create(10 * 1024);
	struct filter_private *fp;
	struct dev_filter *f;

	if (!mem) {
		stack;
		return NULL;
	}

	if (!(f = pool_zalloc(mem, sizeof(*f)))) {
		stack;
		goto bad;
	}

	if (!(fp = pool_zalloc(mem, sizeof(*fp)))) {
		stack;
		goto bad;
	}

	fp->mem = mem;
	f->passes_filter = _accept_label;
	f->destroy = _destroy;
	f->private = fp;

	return f;

      bad:
	pool_destroy(mem);
	return NULL;
}

/* Return 1 if both labels are identical, 0 if not or there was an error */
static int lvm2_labels_match(struct labeller *l, struct device *dev)
{
	uint64_t size;
	uint32_t sectsize;
	char *block1;
	char *block2;
	struct label_ondisk *ondisk1;
	struct label_ondisk *ondisk2;
	int status = 0;
	long offset[2];

	if (!dev_get_size(dev, &size))
		return 0;

	if (!dev_get_sectsize(dev, &sectsize))
		return 0;

/* Allocate some space for the blocks we are going to read in */
	block1 = dbg_malloc(sectsize);
	if (!block1) {
		stack;
		return 0;
	}

	block2 = dbg_malloc(sectsize);
	if (!block2) {
		stack;
		dbg_free(block1);
		return 0;
	}
	ondisk1 = (struct label_ondisk *) block1;
	ondisk2 = (struct label_ondisk *) block2;

	get_label_locations(size, sectsize, &offset[0], &offset[1]);

	/* Fetch em */
	if (!dev_open(dev, O_RDONLY))
		goto finish;

	if (!dev_read(dev, offset[0], sectsize, block1))
		goto finish;

	if (!dev_read(dev, offset[1], sectsize, block2))
		goto finish;

	dev_close(dev);

	/* Is it labelled? */
	if (xlate32(ondisk1->magic) != LABEL_MAGIC)
		goto finish;

	/* Compare the whole structs */
	if (memcmp(ondisk1, ondisk2, sizeof(struct label_ondisk)) != 0)
		goto finish;

	/* OK, check the data area */
	if (memcmp(block1 + sizeof(struct label_ondisk),
		   block2 + sizeof(struct label_ondisk),
		   xlate16(ondisk1->datalen)) != 0)
		goto finish;

	/* They match !! */
	status = 1;

      finish:
	dbg_free(block2);
	dbg_free(block1);

	return status;
}

static int lvm2_label_remove(struct labeller *l, struct device *dev)
{
	uint64_t size;
	uint32_t sectsize;
	char block[BLOCK_SIZE];
	int status1, status2;
	long offset[2];

	if (!dev_get_size(dev, &size))
		return 0;

	if (!dev_get_sectsize(dev, &sectsize))
		return 0;

	if (!dev_open(dev, O_RDWR)) {
		dbg_free(block);
		return 0;
	}

	get_label_locations(size, sectsize, &offset[0], &offset[1]);
	memset(block, 0, BLOCK_SIZE);

	/* Blank out the first label */
	status1 = dev_write(dev, offset[0], BLOCK_SIZE, block);
	if (!status1)
		log_error("Error erasing label 1\n");

	/* ...and the other at the end of the device */
	status2 = dev_write(dev, offset[1], BLOCK_SIZE, block);
	if (!status2)
		log_error("Error erasing label 2\n");

	dev_close(dev);

	return ((status1 != 0) && (status2 != 0));
}

static void lvm2_label_destroy(struct labeller *l)
{
}

static struct label_ops handler_ops = {
	can_handle:	lvm2_is_labelled,
	write:		lvm2_label_write,
	remove:		lvm2_label_remove,
	read:		lvm2_label_read,
	verify:		lvm2_labels_match,
	destroy:	lvm2_label_destroy,
};

static struct labeller this_labeller = {
	private:	NULL,
	ops:		&handler_ops,
};

/* Don't know how this gets called... */
void lvm2_label_init()
{
	label_register_handler("LVM2", &this_labeller);
}