Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1530 insertions, 0 deletions

diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
new file mode 100644
index 000000000..24df610a2
--- /dev/null
+++ b/drivers/md/dm-verity-target.c
@@ -0,0 +1,1530 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2012 Red Hat, Inc.
+ *
+ * Author: Mikulas Patocka <mpatocka@redhat.com>
+ *
+ * Based on Chromium dm-verity driver (C) 2011 The Chromium OS Authors
+ *
+ * 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 "dm-verity-verify-sig.h"
+#include <linux/module.h>
+#include <linux/reboot.h>
+#include <linux/scatterlist.h>
+#include <linux/string.h>
+#include <linux/jump_label.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_PANIC		"panic_on_corruption"
+#define DM_VERITY_OPT_IGN_ZEROES	"ignore_zero_blocks"
+#define DM_VERITY_OPT_AT_MOST_ONCE	"check_at_most_once"
+#define DM_VERITY_OPT_TASKLET_VERIFY	"try_verify_in_tasklet"
+
+#define DM_VERITY_OPTS_MAX		(4 + DM_VERITY_OPTS_FEC + \
+					 DM_VERITY_ROOT_HASH_VERIFICATION_OPTS)
+
+static unsigned int dm_verity_prefetch_cluster = DM_VERITY_DEFAULT_PREFETCH_SIZE;
+
+module_param_named(prefetch_cluster, dm_verity_prefetch_cluster, uint, S_IRUGO | S_IWUSR);
+
+static DEFINE_STATIC_KEY_FALSE(use_tasklet_enabled);
+
+struct dm_verity_prefetch_work {
+	struct work_struct work;
+	struct dm_verity *v;
+	sector_t block;
+	unsigned int 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);
+}
+
+static int verity_hash_update(struct dm_verity *v, struct ahash_request *req,
+				const u8 *data, size_t len,
+				struct crypto_wait *wait)
+{
+	struct scatterlist sg;
+
+	if (likely(!is_vmalloc_addr(data))) {
+		sg_init_one(&sg, data, len);
+		ahash_request_set_crypt(req, &sg, NULL, len);
+		return crypto_wait_req(crypto_ahash_update(req), wait);
+	} 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 = crypto_wait_req(crypto_ahash_update(req), wait);
+			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 crypto_wait *wait, bool may_sleep)
+{
+	int r;
+
+	ahash_request_set_tfm(req, v->tfm);
+	ahash_request_set_callback(req,
+		may_sleep ? CRYPTO_TFM_REQ_MAY_SLEEP | CRYPTO_TFM_REQ_MAY_BACKLOG : 0,
+		crypto_req_done, (void *)wait);
+	crypto_init_wait(wait);
+
+	r = crypto_wait_req(crypto_ahash_init(req), wait);
+
+	if (unlikely(r < 0)) {
+		if (r != -ENOMEM)
+			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, wait);
+
+	return r;
+}
+
+static int verity_hash_final(struct dm_verity *v, struct ahash_request *req,
+			     u8 *digest, struct crypto_wait *wait)
+{
+	int r;
+
+	if (unlikely(v->salt_size && (!v->version))) {
+		r = verity_hash_update(v, req, v->salt, v->salt_size, wait);
+
+		if (r < 0) {
+			DMERR("verity_hash_final failed updating salt: %d", r);
+			goto out;
+		}
+	}
+
+	ahash_request_set_crypt(req, NULL, digest, 0);
+	r = crypto_wait_req(crypto_ahash_final(req), wait);
+out:
+	return r;
+}
+
+int verity_hash(struct dm_verity *v, struct ahash_request *req,
+		const u8 *data, size_t len, u8 *digest, bool may_sleep)
+{
+	int r;
+	struct crypto_wait wait;
+
+	r = verity_hash_init(v, req, &wait, may_sleep);
+	if (unlikely(r < 0))
+		goto out;
+
+	r = verity_hash_update(v, req, data, len, &wait);
+	if (unlikely(r < 0))
+		goto out;
+
+	r = verity_hash_final(v, req, digest, &wait);
+
+out:
+	return r;
+}
+
+static void verity_hash_at_level(struct dm_verity *v, sector_t block, int level,
+				 sector_t *hash_block, unsigned int *offset)
+{
+	sector_t position = verity_position_at_level(v, block, level);
+	unsigned int 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 = true;
+
+	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_LIMIT("%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");
+
+	if (v->mode == DM_VERITY_MODE_PANIC)
+		panic("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 int offset;
+
+	verity_hash_at_level(v, block, level, &hash_block, &offset);
+
+	if (static_branch_unlikely(&use_tasklet_enabled) && io->in_tasklet) {
+		data = dm_bufio_get(v->bufio, hash_block, &buf);
+		if (data == NULL) {
+			/*
+			 * In tasklet and the hash was not in the bufio cache.
+			 * Return early and resume execution from a work-queue
+			 * to read the hash from disk.
+			 */
+			return -EAGAIN;
+		}
+	} else
+		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), !io->in_tasklet);
+		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 (static_branch_unlikely(&use_tasklet_enabled) &&
+			 io->in_tasklet) {
+			/*
+			 * Error handling code (FEC included) cannot be run in a
+			 * tasklet since it may sleep, so fallback to work-queue.
+			 */
+			r = -EAGAIN;
+			goto release_ret_r;
+		}
+		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
+ */
+static int verity_for_io_block(struct dm_verity *v, struct dm_verity_io *io,
+			       struct bvec_iter *iter, struct crypto_wait *wait)
+{
+	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 = crypto_wait_req(crypto_ahash_update(req), wait);
+
+		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 int 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 int len;
+		struct bio_vec bv = bio_iter_iovec(bio, *iter);
+
+		page = bvec_kmap_local(&bv);
+		len = bv.bv_len;
+
+		if (likely(len >= todo))
+			len = todo;
+
+		r = process(v, io, page, len);
+		kunmap_local(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;
+}
+
+/*
+ * Moves the bio iter one data block forward.
+ */
+static inline void verity_bv_skip_block(struct dm_verity *v,
+					struct dm_verity_io *io,
+					struct bvec_iter *iter)
+{
+	struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
+
+	bio_advance_iter(bio, iter, 1 << v->data_dev_block_bits);
+}
+
+/*
+ * 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;
+#if defined(CONFIG_DM_VERITY_FEC)
+	struct bvec_iter start;
+#endif
+	struct bvec_iter iter_copy;
+	struct bvec_iter *iter;
+	struct crypto_wait wait;
+	struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
+	unsigned int b;
+
+	if (static_branch_unlikely(&use_tasklet_enabled) && io->in_tasklet) {
+		/*
+		 * Copy the iterator in case we need to restart
+		 * verification in a work-queue.
+		 */
+		iter_copy = io->iter;
+		iter = &iter_copy;
+	} else
+		iter = &io->iter;
+
+	for (b = 0; b < io->n_blocks; b++) {
+		int r;
+		sector_t cur_block = io->block + b;
+		struct ahash_request *req = verity_io_hash_req(v, io);
+
+		if (v->validated_blocks && bio->bi_status == BLK_STS_OK &&
+		    likely(test_bit(cur_block, v->validated_blocks))) {
+			verity_bv_skip_block(v, io, iter);
+			continue;
+		}
+
+		r = verity_hash_for_block(v, io, cur_block,
+					  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, iter,
+						verity_bv_zero);
+			if (unlikely(r < 0))
+				return r;
+
+			continue;
+		}
+
+		r = verity_hash_init(v, req, &wait, !io->in_tasklet);
+		if (unlikely(r < 0))
+			return r;
+
+#if defined(CONFIG_DM_VERITY_FEC)
+		if (verity_fec_is_enabled(v))
+			start = *iter;
+#endif
+		r = verity_for_io_block(v, io, iter, &wait);
+		if (unlikely(r < 0))
+			return r;
+
+		r = verity_hash_final(v, req, verity_io_real_digest(v, io),
+					&wait);
+		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)) {
+			if (v->validated_blocks)
+				set_bit(cur_block, v->validated_blocks);
+			continue;
+		} else if (static_branch_unlikely(&use_tasklet_enabled) &&
+			   io->in_tasklet) {
+			/*
+			 * Error handling code (FEC included) cannot be run in a
+			 * tasklet since it may sleep, so fallback to work-queue.
+			 */
+			return -EAGAIN;
+#if defined(CONFIG_DM_VERITY_FEC)
+		} else if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_DATA,
+					     cur_block, NULL, &start) == 0) {
+			continue;
+#endif
+		} else {
+			if (bio->bi_status) {
+				/*
+				 * Error correction failed; Just return error
+				 */
+				return -EIO;
+			}
+			if (verity_handle_err(v, DM_VERITY_BLOCK_TYPE_DATA,
+					      cur_block))
+				return -EIO;
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * Skip verity work in response to I/O error when system is shutting down.
+ */
+static inline bool verity_is_system_shutting_down(void)
+{
+	return system_state == SYSTEM_HALT || system_state == SYSTEM_POWER_OFF
+		|| system_state == SYSTEM_RESTART;
+}
+
+/*
+ * 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;
+
+	if (!static_branch_unlikely(&use_tasklet_enabled) || !io->in_tasklet)
+		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);
+
+	io->in_tasklet = false;
+
+	verity_finish_io(io, errno_to_blk_status(verity_verify_io(io)));
+}
+
+static void verity_tasklet(unsigned long data)
+{
+	struct dm_verity_io *io = (struct dm_verity_io *)data;
+	int err;
+
+	io->in_tasklet = true;
+	err = verity_verify_io(io);
+	if (err == -EAGAIN || err == -ENOMEM) {
+		/* fallback to retrying with work-queue */
+		INIT_WORK(&io->work, verity_work);
+		queue_work(io->v->verify_wq, &io->work);
+		return;
+	}
+
+	verity_finish_io(io, errno_to_blk_status(err));
+}
+
+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_is_system_shutting_down() ||
+	     (bio->bi_opf & REQ_RAHEAD))) {
+		verity_finish_io(io, bio->bi_status);
+		return;
+	}
+
+	if (static_branch_unlikely(&use_tasklet_enabled) && io->v->use_tasklet) {
+		tasklet_init(&io->tasklet, verity_tasklet, (unsigned long)io);
+		tasklet_schedule(&io->tasklet);
+	} else {
+		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 int cluster = READ_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)
+{
+	sector_t block = io->block;
+	unsigned int n_blocks = io->n_blocks;
+	struct dm_verity_prefetch_work *pw;
+
+	if (v->validated_blocks) {
+		while (n_blocks && test_bit(block, v->validated_blocks)) {
+			block++;
+			n_blocks--;
+		}
+		while (n_blocks && test_bit(block + n_blocks - 1,
+					    v->validated_blocks))
+			n_blocks--;
+		if (!n_blocks)
+			return;
+	}
+
+	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 = block;
+	pw->n_blocks = 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 int)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);
+
+	submit_bio_noacct(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 int status_flags, char *result, unsigned int maxlen)
+{
+	struct dm_verity *v = ti->private;
+	unsigned int args = 0;
+	unsigned int sz = 0;
+	unsigned int 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 (v->validated_blocks)
+			args++;
+		if (v->use_tasklet)
+			args++;
+		if (v->signature_key_desc)
+			args += DM_VERITY_ROOT_HASH_VERIFICATION_OPTS;
+		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;
+			case DM_VERITY_MODE_PANIC:
+				DMEMIT(DM_VERITY_OPT_PANIC);
+				break;
+			default:
+				BUG();
+			}
+		}
+		if (v->zero_digest)
+			DMEMIT(" " DM_VERITY_OPT_IGN_ZEROES);
+		if (v->validated_blocks)
+			DMEMIT(" " DM_VERITY_OPT_AT_MOST_ONCE);
+		if (v->use_tasklet)
+			DMEMIT(" " DM_VERITY_OPT_TASKLET_VERIFY);
+		sz = verity_fec_status_table(v, sz, result, maxlen);
+		if (v->signature_key_desc)
+			DMEMIT(" " DM_VERITY_ROOT_HASH_VERIFICATION_OPT_SIG_KEY
+				" %s", v->signature_key_desc);
+		break;
+
+	case STATUSTYPE_IMA:
+		DMEMIT_TARGET_NAME_VERSION(ti->type);
+		DMEMIT(",hash_failed=%c", v->hash_failed ? 'C' : 'V');
+		DMEMIT(",verity_version=%u", v->version);
+		DMEMIT(",data_device_name=%s", v->data_dev->name);
+		DMEMIT(",hash_device_name=%s", v->hash_dev->name);
+		DMEMIT(",verity_algorithm=%s", v->alg_name);
+
+		DMEMIT(",root_digest=");
+		for (x = 0; x < v->digest_size; x++)
+			DMEMIT("%02x", v->root_digest[x]);
+
+		DMEMIT(",salt=");
+		if (!v->salt_size)
+			DMEMIT("-");
+		else
+			for (x = 0; x < v->salt_size; x++)
+				DMEMIT("%02x", v->salt[x]);
+
+		DMEMIT(",ignore_zero_blocks=%c", v->zero_digest ? 'y' : 'n');
+		DMEMIT(",check_at_most_once=%c", v->validated_blocks ? 'y' : 'n');
+		if (v->signature_key_desc)
+			DMEMIT(",root_hash_sig_key_desc=%s", v->signature_key_desc);
+
+		if (v->mode != DM_VERITY_MODE_EIO) {
+			DMEMIT(",verity_mode=");
+			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;
+			case DM_VERITY_MODE_PANIC:
+				DMEMIT(DM_VERITY_OPT_PANIC);
+				break;
+			default:
+				DMEMIT("invalid");
+			}
+		}
+		DMEMIT(";");
+		break;
+	}
+}
+
+static int verity_prepare_ioctl(struct dm_target *ti, struct block_device **bdev)
+{
+	struct dm_verity *v = ti->private;
+
+	*bdev = v->data_dev->bdev;
+
+	if (v->data_start || ti->len != bdev_nr_sectors(v->data_dev->bdev))
+		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);
+
+	kvfree(v->validated_blocks);
+	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->signature_key_desc);
+
+	if (v->use_tasklet)
+		static_branch_dec(&use_tasklet_enabled);
+
+	kfree(v);
+}
+
+static int verity_alloc_most_once(struct dm_verity *v)
+{
+	struct dm_target *ti = v->ti;
+
+	/* the bitset can only handle INT_MAX blocks */
+	if (v->data_blocks > INT_MAX) {
+		ti->error = "device too large to use check_at_most_once";
+		return -E2BIG;
+	}
+
+	v->validated_blocks = kvcalloc(BITS_TO_LONGS(v->data_blocks),
+				       sizeof(unsigned long),
+				       GFP_KERNEL);
+	if (!v->validated_blocks) {
+		ti->error = "failed to allocate bitset for check_at_most_once";
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+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, true);
+
+out:
+	kfree(req);
+	kfree(zero_data);
+
+	return r;
+}
+
+static inline bool verity_is_verity_mode(const char *arg_name)
+{
+	return (!strcasecmp(arg_name, DM_VERITY_OPT_LOGGING) ||
+		!strcasecmp(arg_name, DM_VERITY_OPT_RESTART) ||
+		!strcasecmp(arg_name, DM_VERITY_OPT_PANIC));
+}
+
+static int verity_parse_verity_mode(struct dm_verity *v, const char *arg_name)
+{
+	if (v->mode)
+		return -EINVAL;
+
+	if (!strcasecmp(arg_name, DM_VERITY_OPT_LOGGING))
+		v->mode = DM_VERITY_MODE_LOGGING;
+	else if (!strcasecmp(arg_name, DM_VERITY_OPT_RESTART))
+		v->mode = DM_VERITY_MODE_RESTART;
+	else if (!strcasecmp(arg_name, DM_VERITY_OPT_PANIC))
+		v->mode = DM_VERITY_MODE_PANIC;
+
+	return 0;
+}
+
+static int verity_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v,
+				 struct dm_verity_sig_opts *verify_args,
+				 bool only_modifier_opts)
+{
+	int r = 0;
+	unsigned int 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 (verity_is_verity_mode(arg_name)) {
+			if (only_modifier_opts)
+				continue;
+			r = verity_parse_verity_mode(v, arg_name);
+			if (r) {
+				ti->error = "Conflicting error handling parameters";
+				return r;
+			}
+			continue;
+
+		} else if (!strcasecmp(arg_name, DM_VERITY_OPT_IGN_ZEROES)) {
+			if (only_modifier_opts)
+				continue;
+			r = verity_alloc_zero_digest(v);
+			if (r) {
+				ti->error = "Cannot allocate zero digest";
+				return r;
+			}
+			continue;
+
+		} else if (!strcasecmp(arg_name, DM_VERITY_OPT_AT_MOST_ONCE)) {
+			if (only_modifier_opts)
+				continue;
+			r = verity_alloc_most_once(v);
+			if (r)
+				return r;
+			continue;
+
+		} else if (!strcasecmp(arg_name, DM_VERITY_OPT_TASKLET_VERIFY)) {
+			v->use_tasklet = true;
+			static_branch_inc(&use_tasklet_enabled);
+			continue;
+
+		} else if (verity_is_fec_opt_arg(arg_name)) {
+			if (only_modifier_opts)
+				continue;
+			r = verity_fec_parse_opt_args(as, v, &argc, arg_name);
+			if (r)
+				return r;
+			continue;
+
+		} else if (verity_verify_is_sig_opt_arg(arg_name)) {
+			if (only_modifier_opts)
+				continue;
+			r = verity_verify_sig_parse_opt_args(as, v,
+							     verify_args,
+							     &argc, arg_name);
+			if (r)
+				return r;
+			continue;
+
+		} else if (only_modifier_opts) {
+			/*
+			 * Ignore unrecognized opt, could easily be an extra
+			 * argument to an option whose parsing was skipped.
+			 * Normal parsing (@only_modifier_opts=false) will
+			 * properly parse all options (and their extra args).
+			 */
+			continue;
+		}
+
+		DMERR("Unrecognized verity feature request: %s", arg_name);
+		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 int argc, char **argv)
+{
+	struct dm_verity *v;
+	struct dm_verity_sig_opts verify_args = {0};
+	struct dm_arg_set as;
+	unsigned int num;
+	unsigned int wq_flags;
+	unsigned long long num_ll;
+	int r;
+	int i;
+	sector_t hash_position;
+	char dummy;
+	char *root_hash_digest_to_validate;
+
+	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;
+	}
+
+	/* Parse optional parameters that modify primary args */
+	if (argc > 10) {
+		as.argc = argc - 10;
+		as.argv = argv + 10;
+		r = verity_parse_opt_args(&as, v, &verify_args, true);
+		if (r < 0)
+			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,
+				    v->use_tasklet ? CRYPTO_ALG_ASYNC : 0);
+	if (IS_ERR(v->tfm)) {
+		ti->error = "Cannot initialize hash function";
+		r = PTR_ERR(v->tfm);
+		v->tfm = NULL;
+		goto bad;
+	}
+
+	/*
+	 * dm-verity performance can vary greatly depending on which hash
+	 * algorithm implementation is used.  Help people debug performance
+	 * problems by logging the ->cra_driver_name.
+	 */
+	DMINFO("%s using implementation \"%s\"", v->alg_name,
+	       crypto_hash_alg_common(v->tfm)->base.cra_driver_name);
+
+	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;
+	}
+	root_hash_digest_to_validate = argv[8];
+
+	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, &verify_args, false);
+		if (r < 0)
+			goto bad;
+	}
+
+	/* Root hash signature is  a optional parameter*/
+	r = verity_verify_root_hash(root_hash_digest_to_validate,
+				    strlen(root_hash_digest_to_validate),
+				    verify_args.sig,
+				    verify_args.sig_size);
+	if (r < 0) {
+		ti->error = "Root hash verification failed";
+		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,
+		v->use_tasklet ? DM_BUFIO_CLIENT_NO_SLEEP : 0);
+	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 */
+	wq_flags = WQ_MEM_RECLAIM | WQ_UNBOUND;
+	/*
+	 * Using WQ_HIGHPRI improves throughput and completion latency by
+	 * reducing wait times when reading from a dm-verity device.
+	 *
+	 * Also as required for the "try_verify_in_tasklet" feature: WQ_HIGHPRI
+	 * allows verify_wq to preempt softirq since verification in tasklet
+	 * will fall-back to using it for error handling (or if the bufio cache
+	 * doesn't have required hashes).
+	 */
+	wq_flags |= WQ_HIGHPRI;
+	v->verify_wq = alloc_workqueue("kverityd", wq_flags, 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));
+
+	verity_verify_sig_opts_cleanup(&verify_args);
+
+	return 0;
+
+bad:
+
+	verity_verify_sig_opts_cleanup(&verify_args);
+	verity_dtr(ti);
+
+	return r;
+}
+
+/*
+ * Check whether a DM target is a verity target.
+ */
+bool dm_is_verity_target(struct dm_target *ti)
+{
+	return ti->type->module == THIS_MODULE;
+}
+
+/*
+ * Get the verity mode (error behavior) of a verity target.
+ *
+ * Returns the verity mode of the target, or -EINVAL if 'ti' is not a verity
+ * target.
+ */
+int dm_verity_get_mode(struct dm_target *ti)
+{
+	struct dm_verity *v = ti->private;
+
+	if (!dm_is_verity_target(ti))
+		return -EINVAL;
+
+	return v->mode;
+}
+
+/*
+ * Get the root digest of a verity target.
+ *
+ * Returns a copy of the root digest, the caller is responsible for
+ * freeing the memory of the digest.
+ */
+int dm_verity_get_root_digest(struct dm_target *ti, u8 **root_digest, unsigned int *digest_size)
+{
+	struct dm_verity *v = ti->private;
+
+	if (!dm_is_verity_target(ti))
+		return -EINVAL;
+
+	*root_digest = kmemdup(v->root_digest, v->digest_size, GFP_KERNEL);
+	if (*root_digest == NULL)
+		return -ENOMEM;
+
+	*digest_size = v->digest_size;
+
+	return 0;
+}
+
+static struct target_type verity_target = {
+	.name		= "verity",
+	.features	= DM_TARGET_IMMUTABLE,
+	.version	= {1, 9, 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");