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* Copyright (C) 2012 Red Hat, Inc.
* Copyright (C) 2015 Google, Inc.
* Author: Mikulas Patocka <>
* Based on Chromium dm-verity driver (C) 2011 The Chromium OS Authors
* This file is released under the GPLv2.
#ifndef DM_VERITY_H
#define DM_VERITY_H
#include "dm-bufio.h"
#include <linux/device-mapper.h>
#include <crypto/hash.h>
#include <linux/notifier.h>
enum verity_mode {
enum verity_block_type {
struct dm_verity_fec;
struct dm_verity {
struct dm_dev *data_dev;
struct dm_dev *hash_dev;
struct dm_target *ti;
struct dm_bufio_client *bufio;
char *alg_name;
struct crypto_ahash *tfm;
u8 *root_digest; /* digest of the root block */
u8 *salt; /* salt: its size is salt_size */
u8 *zero_digest; /* digest for a zero block */
unsigned salt_size;
sector_t data_start; /* data offset in 512-byte sectors */
sector_t hash_start; /* hash start in blocks */
sector_t data_blocks; /* the number of data blocks */
sector_t hash_blocks; /* the number of hash blocks */
unsigned char data_dev_block_bits; /* log2(data blocksize) */
unsigned char hash_dev_block_bits; /* log2(hash blocksize) */
unsigned char hash_per_block_bits; /* log2(hashes in hash block) */
unsigned char levels; /* the number of tree levels */
unsigned char version;
unsigned digest_size; /* digest size for the current hash algorithm */
unsigned int ahash_reqsize;/* the size of temporary space for crypto */
int hash_failed; /* set to 1 if hash of any block failed */
enum verity_mode mode; /* mode for handling verification errors */
unsigned corrupted_errs;/* Number of errors for corrupted blocks */
int error_behavior; /* selects error behavior on io errors */
struct workqueue_struct *verify_wq;
/* starting blocks for each tree level. 0 is the lowest level. */
sector_t hash_level_block[DM_VERITY_MAX_LEVELS];
struct dm_verity_fec *fec; /* forward error correction */
struct dm_verity_io {
struct dm_verity *v;
/* original value of bio->bi_end_io */
bio_end_io_t *orig_bi_end_io;
sector_t block;
unsigned n_blocks;
struct bvec_iter iter;
struct work_struct work;
* Three variably-size fields follow this struct:
* u8 hash_req[v->ahash_reqsize];
* u8 real_digest[v->digest_size];
* u8 want_digest[v->digest_size];
* To access them use: verity_io_hash_req(), verity_io_real_digest()
* and verity_io_want_digest().
struct verity_result {
struct completion completion;
int err;
struct dm_verity_error_state {
int code;
int transient; /* Likely to not happen after a reboot */
u64 block;
const char *message;
sector_t dev_start;
sector_t dev_len;
struct block_device *dev;
sector_t hash_dev_start;
sector_t hash_dev_len;
struct block_device *hash_dev;
/* Final behavior after all notifications are completed. */
int behavior;
/* This enum must be matched to allowed_error_behaviors in dm-verity.c */
enum dm_verity_error_behavior {
int dm_verity_register_error_notifier(struct notifier_block *nb);
int dm_verity_unregister_error_notifier(struct notifier_block *nb);
static inline struct ahash_request *verity_io_hash_req(struct dm_verity *v,
struct dm_verity_io *io)
return (struct ahash_request *)(io + 1);
static inline u8 *verity_io_real_digest(struct dm_verity *v,
struct dm_verity_io *io)
return (u8 *)(io + 1) + v->ahash_reqsize;
static inline u8 *verity_io_want_digest(struct dm_verity *v,
struct dm_verity_io *io)
return (u8 *)(io + 1) + v->ahash_reqsize + v->digest_size;
static inline u8 *verity_io_digest_end(struct dm_verity *v,
struct dm_verity_io *io)
return verity_io_want_digest(v, io) + v->digest_size;
extern 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));
extern int verity_hash(struct dm_verity *v, struct ahash_request *req,
const u8 *data, size_t len, u8 *digest);
extern int verity_hash_for_block(struct dm_verity *v, struct dm_verity_io *io,
sector_t block, u8 *digest, bool *is_zero);
extern void verity_status(struct dm_target *ti, status_type_t type,
unsigned status_flags, char *result, unsigned maxlen);
extern int verity_prepare_ioctl(struct dm_target *ti,
struct block_device **bdev, fmode_t *mode);
extern int verity_iterate_devices(struct dm_target *ti,
iterate_devices_callout_fn fn, void *data);
extern void verity_io_hints(struct dm_target *ti, struct queue_limits *limits);
extern void verity_dtr(struct dm_target *ti);
extern int verity_ctr(struct dm_target *ti, unsigned argc, char **argv);
extern int verity_map(struct dm_target *ti, struct bio *bio);
#endif /* DM_VERITY_H */