/*
 * 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 <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_MEMPOOL_SIZE          4
#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_OPTS_MAX              1

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);
}

/*
 * Wrapper for crypto_shash_init, which handles verity salting.
 */
static int verity_hash_init(struct dm_verity *v, struct shash_desc *desc)
{
        int r;

        desc->tfm = v->tfm;
        desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;

        r = crypto_shash_init(desc);

        if (unlikely(r < 0)) {
                DMERR("crypto_shash_init failed: %d", r);
                return r;
        }

        if (likely(v->version >= 1)) {
                r = crypto_shash_update(desc, v->salt, v->salt_size);

                if (unlikely(r < 0)) {
                        DMERR("crypto_shash_update failed: %d", r);
                        return r;
                }
        }

        return 0;
}

static int verity_hash_update(struct dm_verity *v, struct shash_desc *desc,
                              const u8 *data, size_t len)
{
        int r = crypto_shash_update(desc, data, len);

        if (unlikely(r < 0))
                DMERR("crypto_shash_update failed: %d", r);

        return r;
}

static int verity_hash_final(struct dm_verity *v, struct shash_desc *desc,
                             u8 *digest)
{
        int r;

        if (unlikely(!v->version)) {
                r = crypto_shash_update(desc, v->salt, v->salt_size);

                if (r < 0) {
                        DMERR("crypto_shash_update failed: %d", r);
                        return r;
                }
        }

        r = crypto_shash_final(desc, digest);

        if (unlikely(r < 0))
                DMERR("crypto_shash_final failed: %d", r);

        return r;
}

int verity_hash(struct dm_verity *v, struct shash_desc *desc,
                const u8 *data, size_t len, u8 *digest)
{
        int r;

        r = verity_hash_init(v, desc);
        if (unlikely(r < 0))
                return r;

        r = verity_hash_update(v, desc, data, len);
        if (unlikely(r < 0))
                return r;

        return verity_hash_final(v, desc, digest);
}

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_desc(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_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)
{
        int i;
        int r;

        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))
                        return r;
        }

        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))
                        return r;
        }

        return 0;
}

/*
 * Verify one "dm_verity_io" structure.
 */
static int verity_verify_io(struct dm_verity_io *io)
{
        struct dm_verity *v = io->v;
        unsigned b;
        unsigned vector = 0, offset = 0;

        for (b = 0; b < io->n_blocks; b++) {
                int r;
                unsigned todo;
                struct shash_desc *desc = verity_io_hash_desc(v, io);

                r = verity_hash_for_block(v, io, io->block + b,
                                          verity_io_want_digest(v, io));
                if (unlikely(r < 0))
                        return r;

                r = verity_hash_init(v, desc);
                if (unlikely(r < 0))
                        return r;

                todo = 1 << v->data_dev_block_bits;
                do {
                        struct bio_vec *bv;
                        u8 *page;
                        unsigned len;

                        BUG_ON(vector >= io->io_vec_size);
                        bv = &io->io_vec[vector];
                        page = kmap_atomic(bv->bv_page);
                        len = bv->bv_len - offset;
                        if (likely(len >= todo))
                                len = todo;
                        r = verity_hash_update(v, desc,
                                        page + bv->bv_offset + offset, len);
                        kunmap_atomic(page);

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

                        offset += len;
                        if (likely(offset == bv->bv_len)) {
                                offset = 0;
                                vector++;
                        }
                        todo -= len;
                } while (todo);

                r = verity_hash_final(v, desc, verity_io_real_digest(v, io));
                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_handle_err(v, DM_VERITY_BLOCK_TYPE_DATA,
                                io->block + b))
                        return -EIO;
        }
        BUG_ON(vector != io->io_vec_size);
        BUG_ON(offset);

        return 0;
}

/*
 * End one "io" structure with a given error.
 */
static void verity_finish_io(struct dm_verity_io *io, int error)
{
        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;

        if (io->io_vec != io->io_vec_inline)
                mempool_free(io->io_vec, v->vec_mempool);

        bio_endio(bio, error);
}

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, verity_verify_io(io));
}

static void verity_end_io(struct bio *bio, int error)
{
        struct dm_verity_io *io = bio->bi_private;

        if (error) {
                verity_finish_io(io, error);
                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->bi_bdev = v->data_dev->bdev;
        bio->bi_sector = verity_map_sector(v, bio->bi_sector);

        if (((unsigned)bio->bi_sector | bio_sectors(bio)) &
            ((1 << (v->data_dev_block_bits - SECTOR_SHIFT)) - 1)) {
                DMERR_LIMIT("unaligned io");
                return -EIO;
        }

        if (bio_end_sector(bio) >>
            (v->data_dev_block_bits - SECTOR_SHIFT) > v->data_blocks) {
                DMERR_LIMIT("io out of range");
                return -EIO;
        }

        if (bio_data_dir(bio) == WRITE)
                return -EIO;

        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_sector >> (v->data_dev_block_bits - SECTOR_SHIFT);
        io->n_blocks = bio->bi_size >> v->data_dev_block_bits;

        bio->bi_end_io = verity_end_io;
        bio->bi_private = io;
        io->io_vec_size = bio_segments(bio);
        if (io->io_vec_size < DM_VERITY_IO_VEC_INLINE)
                io->io_vec = io->io_vec_inline;
        else
                io->io_vec = mempool_alloc(v->vec_mempool, GFP_NOIO);
        memcpy(io->io_vec, bio_iovec(bio),
               io->io_vec_size * sizeof(struct bio_vec));

        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 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) {
                        DMEMIT(" 1 ");
                        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();
                        }
                }
                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 != i_size_read(v->data_dev->bdev->bd_inode) >> SECTOR_SHIFT)
                return 1;
        return 0;
}

static int verity_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
                        struct bio_vec *biovec, int max_size)
{
        struct dm_verity *v = ti->private;
        struct request_queue *q = bdev_get_queue(v->data_dev->bdev);

        if (!q->merge_bvec_fn)
                return max_size;

        bvm->bi_bdev = v->data_dev->bdev;
        bvm->bi_sector = verity_map_sector(v, bvm->bi_sector);

        return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
}

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->vec_mempool)
                mempool_destroy(v->vec_mempool);

        if (v->bufio)
                dm_bufio_client_destroy(v->bufio);

        kfree(v->salt);
        kfree(v->root_digest);

        if (v->tfm)
                crypto_free_shash(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);

        kfree(v);
}

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;
                }

                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;

        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_shash(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_shash_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->shash_descsize =
                sizeof(struct shash_desc) + crypto_shash_descsize(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;
        }

        ti->per_io_data_size = roundup(sizeof(struct dm_verity_io) + v->shash_descsize + v->digest_size * 2, __alignof__(struct dm_verity_io));

        v->vec_mempool = mempool_create_kmalloc_pool(DM_VERITY_MEMPOOL_SIZE,
                                        BIO_MAX_PAGES * sizeof(struct bio_vec));
        if (!v->vec_mempool) {
                ti->error = "Cannot allocate vector mempool";
                r = -ENOMEM;
                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;
        }

        return 0;

bad:
        verity_dtr(ti);

        return r;
}

static struct target_type verity_target = {
        .name           = "verity",
        .version        = {1, 2, 0},
        .module         = THIS_MODULE,
        .ctr            = verity_ctr,
        .dtr            = verity_dtr,
        .map            = verity_map,
        .status         = verity_status,
        .prepare_ioctl  = verity_prepare_ioctl,
        .merge          = verity_merge,
        .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");