/*
   * Copyright (C) 2012 Red Hat, Inc.
   *
   * Author: Mikulas Patocka <mpatocka@redhat.com>
   *
   * Based on Chromium dm-verity driver (C) 2011 The Chromium OS Authors
   *
   * This file is released under the GPLv2.
   *
   * In the file "/sys/module/dm_verity/parameters/prefetch_cluster" you can set
   * default prefetch value. Data are read in "prefetch_cluster" chunks from the
   * hash device. Setting this greatly improves performance when data and hash
   * are on the same disk on different partitions on devices with poor random
   * access behavior.
   */

  #include "dm-verity.h"

  #include "dm-verity-fec.h"

  
  #include <linux/module.h>

  #include <linux/reboot.h>

  
  #define DM_MSG_PREFIX			"verity"

  #define DM_VERITY_ENV_LENGTH		42
  #define DM_VERITY_ENV_VAR_NAME		"DM_VERITY_ERR_BLOCK_NR"

  #define DM_VERITY_DEFAULT_PREFETCH_SIZE	262144

  #define DM_VERITY_MAX_CORRUPTED_ERRS	100
  
  #define DM_VERITY_OPT_LOGGING		"ignore_corruption"
  #define DM_VERITY_OPT_RESTART		"restart_on_corruption"

  #define DM_VERITY_OPT_IGN_ZEROES	"ignore_zero_blocks"

  #define DM_VERITY_OPTS_MAX		(2 + DM_VERITY_OPTS_FEC)

  static unsigned dm_verity_prefetch_cluster = DM_VERITY_DEFAULT_PREFETCH_SIZE;
  
  module_param_named(prefetch_cluster, dm_verity_prefetch_cluster, uint, S_IRUGO | S_IWUSR);

  struct dm_verity_prefetch_work {
  	struct work_struct work;
  	struct dm_verity *v;
  	sector_t block;
  	unsigned n_blocks;
  };

  /*
   * Auxiliary structure appended to each dm-bufio buffer. If the value
   * hash_verified is nonzero, hash of the block has been verified.
   *
   * The variable hash_verified is set to 0 when allocating the buffer, then
   * it can be changed to 1 and it is never reset to 0 again.
   *
   * There is no lock around this value, a race condition can at worst cause
   * that multiple processes verify the hash of the same buffer simultaneously
   * and write 1 to hash_verified simultaneously.
   * This condition is harmless, so we don't need locking.
   */
  struct buffer_aux {
  	int hash_verified;
  };
  
  /*
   * Initialize struct buffer_aux for a freshly created buffer.
   */
  static void dm_bufio_alloc_callback(struct dm_buffer *buf)
  {
  	struct buffer_aux *aux = dm_bufio_get_aux_data(buf);
  
  	aux->hash_verified = 0;
  }
  
  /*
   * Translate input sector number to the sector number on the target device.
   */
  static sector_t verity_map_sector(struct dm_verity *v, sector_t bi_sector)
  {
  	return v->data_start + dm_target_offset(v->ti, bi_sector);
  }
  
  /*
   * Return hash position of a specified block at a specified tree level
   * (0 is the lowest level).
   * The lowest "hash_per_block_bits"-bits of the result denote hash position
   * inside a hash block. The remaining bits denote location of the hash block.
   */
  static sector_t verity_position_at_level(struct dm_verity *v, sector_t block,
  					 int level)
  {
  	return block >> (level * v->hash_per_block_bits);
  }

  /*

   * Callback function for asynchrnous crypto API completion notification

   */

  static void verity_op_done(struct crypto_async_request *base, int err)

  {

  	struct verity_result *res = (struct verity_result *)base->data;

  	if (err == -EINPROGRESS)
  		return;

  	res->err = err;
  	complete(&res->completion);
  }

  /*
   * Wait for async crypto API callback
   */
  static inline int verity_complete_op(struct verity_result *res, int ret)
  {
  	switch (ret) {
  	case 0:
  		break;

  	case -EINPROGRESS:
  	case -EBUSY:
  		ret = wait_for_completion_interruptible(&res->completion);
  		if (!ret)
  			ret = res->err;
  		reinit_completion(&res->completion);
  		break;

  	default:
  		DMERR("verity_wait_hash: crypto op submission failed: %d", ret);

  	}

  	if (unlikely(ret < 0))
  		DMERR("verity_wait_hash: crypto op failed: %d", ret);
  
  	return ret;

  }

  static int verity_hash_update(struct dm_verity *v, struct ahash_request *req,
  				const u8 *data, size_t len,
  				struct verity_result *res)

  {

  	struct scatterlist sg;

  	if (likely(!is_vmalloc_addr(data))) {
  		sg_init_one(&sg, data, len);
  		ahash_request_set_crypt(req, &sg, NULL, len);
  		return verity_complete_op(res, crypto_ahash_update(req));
  	} else {
  		do {
  			int r;
  			size_t this_step = min_t(size_t, len, PAGE_SIZE - offset_in_page(data));
  			flush_kernel_vmap_range((void *)data, this_step);
  			sg_init_table(&sg, 1);
  			sg_set_page(&sg, vmalloc_to_page(data), this_step, offset_in_page(data));
  			ahash_request_set_crypt(req, &sg, NULL, this_step);
  			r = verity_complete_op(res, crypto_ahash_update(req));
  			if (unlikely(r))
  				return r;
  			data += this_step;
  			len -= this_step;
  		} while (len);
  		return 0;
  	}

  }
  
  /*
   * Wrapper for crypto_ahash_init, which handles verity salting.
   */
  static int verity_hash_init(struct dm_verity *v, struct ahash_request *req,
  				struct verity_result *res)
  {
  	int r;
  
  	ahash_request_set_tfm(req, v->tfm);
  	ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP |
  					CRYPTO_TFM_REQ_MAY_BACKLOG,
  					verity_op_done, (void *)res);
  	init_completion(&res->completion);
  
  	r = verity_complete_op(res, crypto_ahash_init(req));
  
  	if (unlikely(r < 0)) {
  		DMERR("crypto_ahash_init failed: %d", r);
  		return r;
  	}

  	if (likely(v->salt_size && (v->version >= 1)))

  		r = verity_hash_update(v, req, v->salt, v->salt_size, res);

  
  	return r;
  }

  static int verity_hash_final(struct dm_verity *v, struct ahash_request *req,
  			     u8 *digest, struct verity_result *res)

  {
  	int r;

  	if (unlikely(v->salt_size && (!v->version))) {

  		r = verity_hash_update(v, req, v->salt, v->salt_size, res);

  
  		if (r < 0) {

  			DMERR("verity_hash_final failed updating salt: %d", r);
  			goto out;

  		}
  	}

  	ahash_request_set_crypt(req, NULL, digest, 0);
  	r = verity_complete_op(res, crypto_ahash_final(req));
  out:

  	return r;
  }

  int verity_hash(struct dm_verity *v, struct ahash_request *req,

  		const u8 *data, size_t len, u8 *digest)

  {
  	int r;

  	struct verity_result res;

  	r = verity_hash_init(v, req, &res);

  	if (unlikely(r < 0))

  		goto out;

  	r = verity_hash_update(v, req, data, len, &res);

  	if (unlikely(r < 0))

  		goto out;
  
  	r = verity_hash_final(v, req, digest, &res);

  out:
  	return r;

  }

  static void verity_hash_at_level(struct dm_verity *v, sector_t block, int level,
  				 sector_t *hash_block, unsigned *offset)
  {
  	sector_t position = verity_position_at_level(v, block, level);
  	unsigned idx;
  
  	*hash_block = v->hash_level_block[level] + (position >> v->hash_per_block_bits);
  
  	if (!offset)
  		return;
  
  	idx = position & ((1 << v->hash_per_block_bits) - 1);
  	if (!v->version)
  		*offset = idx * v->digest_size;
  	else
  		*offset = idx << (v->hash_dev_block_bits - v->hash_per_block_bits);
  }
  
  /*

   * Handle verification errors.
   */
  static int verity_handle_err(struct dm_verity *v, enum verity_block_type type,
  			     unsigned long long block)
  {
  	char verity_env[DM_VERITY_ENV_LENGTH];
  	char *envp[] = { verity_env, NULL };
  	const char *type_str = "";
  	struct mapped_device *md = dm_table_get_md(v->ti->table);
  
  	/* Corruption should be visible in device status in all modes */
  	v->hash_failed = 1;
  
  	if (v->corrupted_errs >= DM_VERITY_MAX_CORRUPTED_ERRS)
  		goto out;
  
  	v->corrupted_errs++;
  
  	switch (type) {
  	case DM_VERITY_BLOCK_TYPE_DATA:
  		type_str = "data";
  		break;
  	case DM_VERITY_BLOCK_TYPE_METADATA:
  		type_str = "metadata";
  		break;
  	default:
  		BUG();
  	}
  
  	DMERR("%s: %s block %llu is corrupted", v->data_dev->name, type_str,
  		block);
  
  	if (v->corrupted_errs == DM_VERITY_MAX_CORRUPTED_ERRS)
  		DMERR("%s: reached maximum errors", v->data_dev->name);
  
  	snprintf(verity_env, DM_VERITY_ENV_LENGTH, "%s=%d,%llu",
  		DM_VERITY_ENV_VAR_NAME, type, block);
  
  	kobject_uevent_env(&disk_to_dev(dm_disk(md))->kobj, KOBJ_CHANGE, envp);
  
  out:
  	if (v->mode == DM_VERITY_MODE_LOGGING)
  		return 0;
  
  	if (v->mode == DM_VERITY_MODE_RESTART)
  		kernel_restart("dm-verity device corrupted");
  
  	return 1;
  }
  
  /*

   * Verify hash of a metadata block pertaining to the specified data block
   * ("block" argument) at a specified level ("level" argument).
   *

   * On successful return, verity_io_want_digest(v, io) contains the hash value
   * for a lower tree level or for the data block (if we're at the lowest level).

   *
   * If "skip_unverified" is true, unverified buffer is skipped and 1 is returned.
   * If "skip_unverified" is false, unverified buffer is hashed and verified

   * against current value of verity_io_want_digest(v, io).

   */

  static int verity_verify_level(struct dm_verity *v, struct dm_verity_io *io,
  			       sector_t block, int level, bool skip_unverified,
  			       u8 *want_digest)

  {

  	struct dm_buffer *buf;
  	struct buffer_aux *aux;
  	u8 *data;
  	int r;
  	sector_t hash_block;
  	unsigned offset;
  
  	verity_hash_at_level(v, block, level, &hash_block, &offset);
  
  	data = dm_bufio_read(v->bufio, hash_block, &buf);

  	if (IS_ERR(data))

  		return PTR_ERR(data);
  
  	aux = dm_bufio_get_aux_data(buf);
  
  	if (!aux->hash_verified) {

  		if (skip_unverified) {
  			r = 1;
  			goto release_ret_r;
  		}

  		r = verity_hash(v, verity_io_hash_req(v, io),

  				data, 1 << v->hash_dev_block_bits,

  				verity_io_real_digest(v, io));

  		if (unlikely(r < 0))

  			goto release_ret_r;

  		if (likely(memcmp(verity_io_real_digest(v, io), want_digest,

  				  v->digest_size) == 0))
  			aux->hash_verified = 1;

  		else if (verity_fec_decode(v, io,
  					   DM_VERITY_BLOCK_TYPE_METADATA,
  					   hash_block, data, NULL) == 0)
  			aux->hash_verified = 1;

  		else if (verity_handle_err(v,
  					   DM_VERITY_BLOCK_TYPE_METADATA,
  					   hash_block)) {
  			r = -EIO;

  			goto release_ret_r;
  		}

  	}
  
  	data += offset;

  	memcpy(want_digest, data, v->digest_size);
  	r = 0;

  
  release_ret_r:
  	dm_bufio_release(buf);

  	return r;
  }
  
  /*

   * Find a hash for a given block, write it to digest and verify the integrity
   * of the hash tree if necessary.
   */

  int verity_hash_for_block(struct dm_verity *v, struct dm_verity_io *io,

  			  sector_t block, u8 *digest, bool *is_zero)

  {

  	int r = 0, i;

  
  	if (likely(v->levels)) {
  		/*
  		 * First, we try to get the requested hash for
  		 * the current block. If the hash block itself is
  		 * verified, zero is returned. If it isn't, this
  		 * function returns 1 and we fall back to whole
  		 * chain verification.
  		 */
  		r = verity_verify_level(v, io, block, 0, true, digest);
  		if (likely(r <= 0))

  			goto out;

  	}
  
  	memcpy(digest, v->root_digest, v->digest_size);
  
  	for (i = v->levels - 1; i >= 0; i--) {
  		r = verity_verify_level(v, io, block, i, false, digest);
  		if (unlikely(r))

  			goto out;

  	}

  out:
  	if (!r && v->zero_digest)
  		*is_zero = !memcmp(v->zero_digest, digest, v->digest_size);
  	else
  		*is_zero = false;

  	return r;

  }
  
  /*

   * Calculates the digest for the given bio
   */
  int verity_for_io_block(struct dm_verity *v, struct dm_verity_io *io,
  			struct bvec_iter *iter, struct verity_result *res)
  {
  	unsigned int todo = 1 << v->data_dev_block_bits;
  	struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
  	struct scatterlist sg;
  	struct ahash_request *req = verity_io_hash_req(v, io);
  
  	do {
  		int r;
  		unsigned int len;
  		struct bio_vec bv = bio_iter_iovec(bio, *iter);
  
  		sg_init_table(&sg, 1);
  
  		len = bv.bv_len;
  
  		if (likely(len >= todo))
  			len = todo;
  		/*
  		 * Operating on a single page at a time looks suboptimal
  		 * until you consider the typical block size is 4,096B.
  		 * Going through this loops twice should be very rare.
  		 */
  		sg_set_page(&sg, bv.bv_page, len, bv.bv_offset);
  		ahash_request_set_crypt(req, &sg, NULL, len);
  		r = verity_complete_op(res, crypto_ahash_update(req));
  
  		if (unlikely(r < 0)) {
  			DMERR("verity_for_io_block crypto op failed: %d", r);
  			return r;
  		}
  
  		bio_advance_iter(bio, iter, len);
  		todo -= len;
  	} while (todo);
  
  	return 0;
  }
  
  /*

   * Calls function process for 1 << v->data_dev_block_bits bytes in the bio_vec
   * starting from iter.
   */
  int verity_for_bv_block(struct dm_verity *v, struct dm_verity_io *io,
  			struct bvec_iter *iter,
  			int (*process)(struct dm_verity *v,
  				       struct dm_verity_io *io, u8 *data,
  				       size_t len))
  {
  	unsigned todo = 1 << v->data_dev_block_bits;

  	struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);

  
  	do {
  		int r;
  		u8 *page;
  		unsigned len;
  		struct bio_vec bv = bio_iter_iovec(bio, *iter);
  
  		page = kmap_atomic(bv.bv_page);
  		len = bv.bv_len;
  
  		if (likely(len >= todo))
  			len = todo;
  
  		r = process(v, io, page + bv.bv_offset, len);
  		kunmap_atomic(page);
  
  		if (r < 0)
  			return r;
  
  		bio_advance_iter(bio, iter, len);
  		todo -= len;
  	} while (todo);
  
  	return 0;
  }

  static int verity_bv_zero(struct dm_verity *v, struct dm_verity_io *io,
  			  u8 *data, size_t len)
  {
  	memset(data, 0, len);
  	return 0;
  }

  /*

   * Verify one "dm_verity_io" structure.
   */
  static int verity_verify_io(struct dm_verity_io *io)
  {

  	bool is_zero;

  	struct dm_verity *v = io->v;

  	struct bvec_iter start;

  	unsigned b;

  	struct verity_result res;

  
  	for (b = 0; b < io->n_blocks; b++) {

  		int r;

  		struct ahash_request *req = verity_io_hash_req(v, io);

  		r = verity_hash_for_block(v, io, io->block + b,

  					  verity_io_want_digest(v, io),
  					  &is_zero);

  		if (unlikely(r < 0))
  			return r;

  		if (is_zero) {
  			/*
  			 * If we expect a zero block, don't validate, just
  			 * return zeros.
  			 */
  			r = verity_for_bv_block(v, io, &io->iter,
  						verity_bv_zero);
  			if (unlikely(r < 0))
  				return r;
  
  			continue;
  		}

  		r = verity_hash_init(v, req, &res);

  		if (unlikely(r < 0))

  			return r;

  		start = io->iter;

  		r = verity_for_io_block(v, io, &io->iter, &res);

  		if (unlikely(r < 0))
  			return r;

  		r = verity_hash_final(v, req, verity_io_real_digest(v, io),
  					&res);

  		if (unlikely(r < 0))

  			return r;

  		if (likely(memcmp(verity_io_real_digest(v, io),
  				  verity_io_want_digest(v, io), v->digest_size) == 0))

  			continue;

  		else if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_DATA,
  					   io->block + b, NULL, &start) == 0)
  			continue;

  		else if (verity_handle_err(v, DM_VERITY_BLOCK_TYPE_DATA,

  					   io->block + b))

  			return -EIO;

  	}

  
  	return 0;
  }
  
  /*
   * End one "io" structure with a given error.
   */

  static void verity_finish_io(struct dm_verity_io *io, blk_status_t status)

  {

  	struct dm_verity *v = io->v;

  	struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);

  
  	bio->bi_end_io = io->orig_bi_end_io;

  	bio->bi_status = status;

  	verity_fec_finish_io(io);

  	bio_endio(bio);

  }
  
  static void verity_work(struct work_struct *w)
  {
  	struct dm_verity_io *io = container_of(w, struct dm_verity_io, work);

  	verity_finish_io(io, errno_to_blk_status(verity_verify_io(io)));

  }

  static void verity_end_io(struct bio *bio)

  {
  	struct dm_verity_io *io = bio->bi_private;

  	if (bio->bi_status && !verity_fec_is_enabled(io->v)) {
  		verity_finish_io(io, bio->bi_status);

  		return;
  	}
  
  	INIT_WORK(&io->work, verity_work);
  	queue_work(io->v->verify_wq, &io->work);
  }
  
  /*
   * Prefetch buffers for the specified io.
   * The root buffer is not prefetched, it is assumed that it will be cached
   * all the time.
   */

  static void verity_prefetch_io(struct work_struct *work)

  {

  	struct dm_verity_prefetch_work *pw =
  		container_of(work, struct dm_verity_prefetch_work, work);
  	struct dm_verity *v = pw->v;

  	int i;
  
  	for (i = v->levels - 2; i >= 0; i--) {
  		sector_t hash_block_start;
  		sector_t hash_block_end;

  		verity_hash_at_level(v, pw->block, i, &hash_block_start, NULL);
  		verity_hash_at_level(v, pw->block + pw->n_blocks - 1, i, &hash_block_end, NULL);

  		if (!i) {

  			unsigned cluster = ACCESS_ONCE(dm_verity_prefetch_cluster);

  
  			cluster >>= v->data_dev_block_bits;
  			if (unlikely(!cluster))
  				goto no_prefetch_cluster;
  
  			if (unlikely(cluster & (cluster - 1)))

  				cluster = 1 << __fls(cluster);

  
  			hash_block_start &= ~(sector_t)(cluster - 1);
  			hash_block_end |= cluster - 1;
  			if (unlikely(hash_block_end >= v->hash_blocks))
  				hash_block_end = v->hash_blocks - 1;
  		}
  no_prefetch_cluster:
  		dm_bufio_prefetch(v->bufio, hash_block_start,
  				  hash_block_end - hash_block_start + 1);
  	}

  
  	kfree(pw);
  }
  
  static void verity_submit_prefetch(struct dm_verity *v, struct dm_verity_io *io)
  {
  	struct dm_verity_prefetch_work *pw;
  
  	pw = kmalloc(sizeof(struct dm_verity_prefetch_work),
  		GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
  
  	if (!pw)
  		return;
  
  	INIT_WORK(&pw->work, verity_prefetch_io);
  	pw->v = v;
  	pw->block = io->block;
  	pw->n_blocks = io->n_blocks;
  	queue_work(v->verify_wq, &pw->work);

  }
  
  /*
   * Bio map function. It allocates dm_verity_io structure and bio vector and
   * fills them. Then it issues prefetches and the I/O.
   */

  static int verity_map(struct dm_target *ti, struct bio *bio)

  {
  	struct dm_verity *v = ti->private;
  	struct dm_verity_io *io;

  	bio_set_dev(bio, v->data_dev->bdev);

  	bio->bi_iter.bi_sector = verity_map_sector(v, bio->bi_iter.bi_sector);

  	if (((unsigned)bio->bi_iter.bi_sector | bio_sectors(bio)) &

  	    ((1 << (v->data_dev_block_bits - SECTOR_SHIFT)) - 1)) {
  		DMERR_LIMIT("unaligned io");

  		return DM_MAPIO_KILL;

  	}

  	if (bio_end_sector(bio) >>

  	    (v->data_dev_block_bits - SECTOR_SHIFT) > v->data_blocks) {
  		DMERR_LIMIT("io out of range");

  		return DM_MAPIO_KILL;

  	}
  
  	if (bio_data_dir(bio) == WRITE)

  		return DM_MAPIO_KILL;

  	io = dm_per_bio_data(bio, ti->per_io_data_size);

  	io->v = v;

  	io->orig_bi_end_io = bio->bi_end_io;

  	io->block = bio->bi_iter.bi_sector >> (v->data_dev_block_bits - SECTOR_SHIFT);
  	io->n_blocks = bio->bi_iter.bi_size >> v->data_dev_block_bits;

  
  	bio->bi_end_io = verity_end_io;
  	bio->bi_private = io;

  	io->iter = bio->bi_iter;

  	verity_fec_init_io(io);

  	verity_submit_prefetch(v, io);

  
  	generic_make_request(bio);
  
  	return DM_MAPIO_SUBMITTED;
  }
  
  /*
   * Status: V (valid) or C (corruption found)
   */

  static void verity_status(struct dm_target *ti, status_type_t type,
  			  unsigned status_flags, char *result, unsigned maxlen)

  {
  	struct dm_verity *v = ti->private;

  	unsigned args = 0;

  	unsigned sz = 0;
  	unsigned x;
  
  	switch (type) {
  	case STATUSTYPE_INFO:
  		DMEMIT("%c", v->hash_failed ? 'C' : 'V');
  		break;
  	case STATUSTYPE_TABLE:
  		DMEMIT("%u %s %s %u %u %llu %llu %s ",
  			v->version,
  			v->data_dev->name,
  			v->hash_dev->name,
  			1 << v->data_dev_block_bits,
  			1 << v->hash_dev_block_bits,
  			(unsigned long long)v->data_blocks,
  			(unsigned long long)v->hash_start,
  			v->alg_name
  			);
  		for (x = 0; x < v->digest_size; x++)
  			DMEMIT("%02x", v->root_digest[x]);
  		DMEMIT(" ");
  		if (!v->salt_size)
  			DMEMIT("-");
  		else
  			for (x = 0; x < v->salt_size; x++)
  				DMEMIT("%02x", v->salt[x]);

  		if (v->mode != DM_VERITY_MODE_EIO)
  			args++;
  		if (verity_fec_is_enabled(v))
  			args += DM_VERITY_OPTS_FEC;

  		if (v->zero_digest)
  			args++;

  		if (!args)
  			return;
  		DMEMIT(" %u", args);

  		if (v->mode != DM_VERITY_MODE_EIO) {

  			DMEMIT(" ");

  			switch (v->mode) {
  			case DM_VERITY_MODE_LOGGING:
  				DMEMIT(DM_VERITY_OPT_LOGGING);
  				break;
  			case DM_VERITY_MODE_RESTART:
  				DMEMIT(DM_VERITY_OPT_RESTART);
  				break;
  			default:
  				BUG();
  			}
  		}

  		if (v->zero_digest)
  			DMEMIT(" " DM_VERITY_OPT_IGN_ZEROES);

  		sz = verity_fec_status_table(v, sz, result, maxlen);

  		break;
  	}

  }

  static int verity_prepare_ioctl(struct dm_target *ti,
  		struct block_device **bdev, fmode_t *mode)

  {
  	struct dm_verity *v = ti->private;

  
  	*bdev = v->data_dev->bdev;

  
  	if (v->data_start ||
  	    ti->len != i_size_read(v->data_dev->bdev->bd_inode) >> SECTOR_SHIFT)

  		return 1;
  	return 0;

  }

  static int verity_iterate_devices(struct dm_target *ti,
  				  iterate_devices_callout_fn fn, void *data)
  {
  	struct dm_verity *v = ti->private;
  
  	return fn(ti, v->data_dev, v->data_start, ti->len, data);
  }
  
  static void verity_io_hints(struct dm_target *ti, struct queue_limits *limits)
  {
  	struct dm_verity *v = ti->private;
  
  	if (limits->logical_block_size < 1 << v->data_dev_block_bits)
  		limits->logical_block_size = 1 << v->data_dev_block_bits;
  
  	if (limits->physical_block_size < 1 << v->data_dev_block_bits)
  		limits->physical_block_size = 1 << v->data_dev_block_bits;
  
  	blk_limits_io_min(limits, limits->logical_block_size);
  }
  
  static void verity_dtr(struct dm_target *ti)
  {
  	struct dm_verity *v = ti->private;
  
  	if (v->verify_wq)
  		destroy_workqueue(v->verify_wq);

  	if (v->bufio)
  		dm_bufio_client_destroy(v->bufio);
  
  	kfree(v->salt);
  	kfree(v->root_digest);

  	kfree(v->zero_digest);

  
  	if (v->tfm)

  		crypto_free_ahash(v->tfm);

  
  	kfree(v->alg_name);
  
  	if (v->hash_dev)
  		dm_put_device(ti, v->hash_dev);
  
  	if (v->data_dev)
  		dm_put_device(ti, v->data_dev);

  	verity_fec_dtr(v);

  	kfree(v);
  }

  static int verity_alloc_zero_digest(struct dm_verity *v)
  {
  	int r = -ENOMEM;

  	struct ahash_request *req;

  	u8 *zero_data;
  
  	v->zero_digest = kmalloc(v->digest_size, GFP_KERNEL);
  
  	if (!v->zero_digest)
  		return r;

  	req = kmalloc(v->ahash_reqsize, GFP_KERNEL);

  	if (!req)

  		return r; /* verity_dtr will free zero_digest */
  
  	zero_data = kzalloc(1 << v->data_dev_block_bits, GFP_KERNEL);
  
  	if (!zero_data)
  		goto out;

  	r = verity_hash(v, req, zero_data, 1 << v->data_dev_block_bits,

  			v->zero_digest);
  
  out:

  	kfree(req);

  	kfree(zero_data);
  
  	return r;
  }

  static int verity_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v)
  {
  	int r;
  	unsigned argc;
  	struct dm_target *ti = v->ti;
  	const char *arg_name;

  	static const struct dm_arg _args[] = {

  		{0, DM_VERITY_OPTS_MAX, "Invalid number of feature args"},
  	};
  
  	r = dm_read_arg_group(_args, as, &argc, &ti->error);
  	if (r)
  		return -EINVAL;
  
  	if (!argc)
  		return 0;
  
  	do {
  		arg_name = dm_shift_arg(as);
  		argc--;
  
  		if (!strcasecmp(arg_name, DM_VERITY_OPT_LOGGING)) {
  			v->mode = DM_VERITY_MODE_LOGGING;
  			continue;
  
  		} else if (!strcasecmp(arg_name, DM_VERITY_OPT_RESTART)) {
  			v->mode = DM_VERITY_MODE_RESTART;
  			continue;

  		} else if (!strcasecmp(arg_name, DM_VERITY_OPT_IGN_ZEROES)) {
  			r = verity_alloc_zero_digest(v);
  			if (r) {
  				ti->error = "Cannot allocate zero digest";
  				return r;
  			}
  			continue;

  		} else if (verity_is_fec_opt_arg(arg_name)) {
  			r = verity_fec_parse_opt_args(as, v, &argc, arg_name);
  			if (r)
  				return r;
  			continue;

  		}
  
  		ti->error = "Unrecognized verity feature request";
  		return -EINVAL;
  	} while (argc && !r);
  
  	return r;
  }

  /*
   * Target parameters:
   *	<version>	The current format is version 1.
   *			Vsn 0 is compatible with original Chromium OS releases.
   *	<data device>
   *	<hash device>
   *	<data block size>
   *	<hash block size>
   *	<the number of data blocks>
   *	<hash start block>
   *	<algorithm>
   *	<digest>
   *	<salt>		Hex string or "-" if no salt.
   */
  static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
  {
  	struct dm_verity *v;

  	struct dm_arg_set as;

  	unsigned int num;

  	unsigned long long num_ll;
  	int r;
  	int i;
  	sector_t hash_position;
  	char dummy;
  
  	v = kzalloc(sizeof(struct dm_verity), GFP_KERNEL);
  	if (!v) {
  		ti->error = "Cannot allocate verity structure";
  		return -ENOMEM;
  	}
  	ti->private = v;
  	v->ti = ti;

  	r = verity_fec_ctr_alloc(v);
  	if (r)
  		goto bad;

  	if ((dm_table_get_mode(ti->table) & ~FMODE_READ)) {
  		ti->error = "Device must be readonly";
  		r = -EINVAL;
  		goto bad;
  	}

  	if (argc < 10) {
  		ti->error = "Not enough arguments";

  		r = -EINVAL;
  		goto bad;
  	}

  	if (sscanf(argv[0], "%u%c", &num, &dummy) != 1 ||
  	    num > 1) {

  		ti->error = "Invalid version";
  		r = -EINVAL;
  		goto bad;
  	}
  	v->version = num;
  
  	r = dm_get_device(ti, argv[1], FMODE_READ, &v->data_dev);
  	if (r) {
  		ti->error = "Data device lookup failed";
  		goto bad;
  	}
  
  	r = dm_get_device(ti, argv[2], FMODE_READ, &v->hash_dev);
  	if (r) {

  		ti->error = "Hash device lookup failed";

  		goto bad;
  	}
  
  	if (sscanf(argv[3], "%u%c", &num, &dummy) != 1 ||
  	    !num || (num & (num - 1)) ||
  	    num < bdev_logical_block_size(v->data_dev->bdev) ||
  	    num > PAGE_SIZE) {
  		ti->error = "Invalid data device block size";
  		r = -EINVAL;
  		goto bad;
  	}

  	v->data_dev_block_bits = __ffs(num);

  
  	if (sscanf(argv[4], "%u%c", &num, &dummy) != 1 ||
  	    !num || (num & (num - 1)) ||
  	    num < bdev_logical_block_size(v->hash_dev->bdev) ||
  	    num > INT_MAX) {
  		ti->error = "Invalid hash device block size";
  		r = -EINVAL;
  		goto bad;
  	}

  	v->hash_dev_block_bits = __ffs(num);

  
  	if (sscanf(argv[5], "%llu%c", &num_ll, &dummy) != 1 ||

  	    (sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT))
  	    >> (v->data_dev_block_bits - SECTOR_SHIFT) != num_ll) {

  		ti->error = "Invalid data blocks";
  		r = -EINVAL;
  		goto bad;
  	}
  	v->data_blocks = num_ll;
  
  	if (ti->len > (v->data_blocks << (v->data_dev_block_bits - SECTOR_SHIFT))) {
  		ti->error = "Data device is too small";
  		r = -EINVAL;
  		goto bad;
  	}
  
  	if (sscanf(argv[6], "%llu%c", &num_ll, &dummy) != 1 ||

  	    (sector_t)(num_ll << (v->hash_dev_block_bits - SECTOR_SHIFT))
  	    >> (v->hash_dev_block_bits - SECTOR_SHIFT) != num_ll) {

  		ti->error = "Invalid hash start";
  		r = -EINVAL;
  		goto bad;
  	}
  	v->hash_start = num_ll;
  
  	v->alg_name = kstrdup(argv[7], GFP_KERNEL);
  	if (!v->alg_name) {
  		ti->error = "Cannot allocate algorithm name";
  		r = -ENOMEM;
  		goto bad;
  	}

  	v->tfm = crypto_alloc_ahash(v->alg_name, 0, 0);

  	if (IS_ERR(v->tfm)) {
  		ti->error = "Cannot initialize hash function";
  		r = PTR_ERR(v->tfm);
  		v->tfm = NULL;
  		goto bad;
  	}

  	v->digest_size = crypto_ahash_digestsize(v->tfm);

  	if ((1 << v->hash_dev_block_bits) < v->digest_size * 2) {
  		ti->error = "Digest size too big";
  		r = -EINVAL;
  		goto bad;
  	}

  	v->ahash_reqsize = sizeof(struct ahash_request) +
  		crypto_ahash_reqsize(v->tfm);

  
  	v->root_digest = kmalloc(v->digest_size, GFP_KERNEL);
  	if (!v->root_digest) {
  		ti->error = "Cannot allocate root digest";
  		r = -ENOMEM;
  		goto bad;
  	}
  	if (strlen(argv[8]) != v->digest_size * 2 ||
  	    hex2bin(v->root_digest, argv[8], v->digest_size)) {
  		ti->error = "Invalid root digest";
  		r = -EINVAL;
  		goto bad;
  	}
  
  	if (strcmp(argv[9], "-")) {
  		v->salt_size = strlen(argv[9]) / 2;
  		v->salt = kmalloc(v->salt_size, GFP_KERNEL);
  		if (!v->salt) {
  			ti->error = "Cannot allocate salt";
  			r = -ENOMEM;
  			goto bad;
  		}
  		if (strlen(argv[9]) != v->salt_size * 2 ||
  		    hex2bin(v->salt, argv[9], v->salt_size)) {
  			ti->error = "Invalid salt";
  			r = -EINVAL;
  			goto bad;
  		}
  	}

  	argv += 10;
  	argc -= 10;
  
  	/* Optional parameters */
  	if (argc) {
  		as.argc = argc;
  		as.argv = argv;

  		r = verity_parse_opt_args(&as, v);
  		if (r < 0)

  			goto bad;

  	}

  	v->hash_per_block_bits =

  		__fls((1 << v->hash_dev_block_bits) / v->digest_size);

  
  	v->levels = 0;
  	if (v->data_blocks)
  		while (v->hash_per_block_bits * v->levels < 64 &&
  		       (unsigned long long)(v->data_blocks - 1) >>
  		       (v->hash_per_block_bits * v->levels))
  			v->levels++;
  
  	if (v->levels > DM_VERITY_MAX_LEVELS) {
  		ti->error = "Too many tree levels";
  		r = -E2BIG;
  		goto bad;
  	}
  
  	hash_position = v->hash_start;
  	for (i = v->levels - 1; i >= 0; i--) {
  		sector_t s;
  		v->hash_level_block[i] = hash_position;

  		s = (v->data_blocks + ((sector_t)1 << ((i + 1) * v->hash_per_block_bits)) - 1)
  					>> ((i + 1) * v->hash_per_block_bits);

  		if (hash_position + s < hash_position) {
  			ti->error = "Hash device offset overflow";
  			r = -E2BIG;
  			goto bad;
  		}
  		hash_position += s;
  	}
  	v->hash_blocks = hash_position;
  
  	v->bufio = dm_bufio_client_create(v->hash_dev->bdev,
  		1 << v->hash_dev_block_bits, 1, sizeof(struct buffer_aux),
  		dm_bufio_alloc_callback, NULL);
  	if (IS_ERR(v->bufio)) {
  		ti->error = "Cannot initialize dm-bufio";
  		r = PTR_ERR(v->bufio);
  		v->bufio = NULL;
  		goto bad;
  	}
  
  	if (dm_bufio_get_device_size(v->bufio) < v->hash_blocks) {
  		ti->error = "Hash device is too small";
  		r = -E2BIG;
  		goto bad;
  	}

  	/* WQ_UNBOUND greatly improves performance when running on ramdisk */
  	v->verify_wq = alloc_workqueue("kverityd", WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM | WQ_UNBOUND, num_online_cpus());
  	if (!v->verify_wq) {
  		ti->error = "Cannot allocate workqueue";
  		r = -ENOMEM;
  		goto bad;
  	}

  	ti->per_io_data_size = sizeof(struct dm_verity_io) +

  				v->ahash_reqsize + v->digest_size * 2;

  
  	r = verity_fec_ctr(v);
  	if (r)
  		goto bad;

  	ti->per_io_data_size = roundup(ti->per_io_data_size,
  				       __alignof__(struct dm_verity_io));

  	return 0;
  
  bad:
  	verity_dtr(ti);
  
  	return r;
  }
  
  static struct target_type verity_target = {
  	.name		= "verity",

  	.version	= {1, 3, 0},

  	.module		= THIS_MODULE,
  	.ctr		= verity_ctr,
  	.dtr		= verity_dtr,
  	.map		= verity_map,
  	.status		= verity_status,

  	.prepare_ioctl	= verity_prepare_ioctl,

  	.iterate_devices = verity_iterate_devices,
  	.io_hints	= verity_io_hints,
  };
  
  static int __init dm_verity_init(void)
  {
  	int r;
  
  	r = dm_register_target(&verity_target);
  	if (r < 0)
  		DMERR("register failed %d", r);
  
  	return r;
  }
  
  static void __exit dm_verity_exit(void)
  {
  	dm_unregister_target(&verity_target);
  }
  
  module_init(dm_verity_init);
  module_exit(dm_verity_exit);
  
  MODULE_AUTHOR("Mikulas Patocka <mpatocka@redhat.com>");
  MODULE_AUTHOR("Mandeep Baines <msb@chromium.org>");
  MODULE_AUTHOR("Will Drewry <wad@chromium.org>");
  MODULE_DESCRIPTION(DM_NAME " target for transparent disk integrity checking");
  MODULE_LICENSE("GPL");