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Message-ID: <CABqD9hYWK2czEKN87xDu7YPbRcp9xrumJ5PZ8aQTzBLafrnBMw@mail.gmail.com>
Date: Tue, 27 Sep 2011 14:02:05 -0500
From: Will Drewry <wad@...omium.org>
To: Mandeep Singh Baines <msb@...omium.org>,
Alasdair G Kergon <agk@...hat.com>,
Milan Broz <mbroz@...hat.com>
Cc: dm-devel@...hat.com, Elly Jones <ellyjones@...omium.org>,
Olof Johansson <olofj@...omium.org>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dm: verity target
Hi all!
I was just curious if there is any interest in pulling this change, or
if not, if there is any particular set of concerns, fixes, etc. I
realize it's not a small amount of code to digest (though it is
smaller than the post from last year[1]). Would re-posting with an
added blob explaining the name be useful, or, perhaps, a name change,
or is there anything further that would be beneficial to
consideration? Jonathan Corbet was kind enough to wade through the
docs and code to write an article[2] which may help. Additionally,
Mandeep and I presented[3] at the Security Summit and the Filesystems
track of Plumbers on the topic which I hope helped show the value of
this patch (everything from layering with EVM to providing tboot users
with a fast, efficient way to verify their system images without
requiring immutable media).
As usual, any and all guidance/feedback/flames will be appreciated - thanks!
will
1 - http://thread.gmane.org/gmane.linux.kernel/989307
2 - http://lwn.net/Articles/459420/
3 - http://selinuxproject.org/~jmorris/lss2011_slides/LSS_11_Integrity_checked_block_devices.pdf
On Thu, Sep 15, 2011 at 1:45 PM, Mandeep Singh Baines <msb@...omium.org> wrote:
> The verity target provides transparent integrity checking of block devices
> using a cryptographic digest.
>
> dm-verity is meant to be setup as part of a verified boot path. This
> may be anything ranging from a boot using tboot or trustedgrub to just
> booting from a known-good device (like a USB drive or CD).
>
> dm-verity is part of ChromeOS's verified boot path. It is used to verify
> the integrity of the root filesystem on boot. The root filesystem is
> mounted on a dm-verity partition which transparently verifies each block
> with a bootloader verified hash passed into the kernel at boot.
>
> Signed-off-by: Will Drewry <wad@...omium.org>
> Signed-off-by: Elly Jones <ellyjones@...omium.org>
> Signed-off-by: Mandeep Singh Baines <msb@...omium.org>
> Cc: Alasdair G Kergon <agk@...hat.com>
> Cc: Milan Broz <mbroz@...hat.com>
> Cc: Olof Johansson <olofj@...omium.org>
> Cc: dm-devel@...hat.com
> Cc: linux-kernel@...r.kernel.org
> ---
> Documentation/device-mapper/dm-bht.txt | 59 ++
> Documentation/device-mapper/dm-verity.txt | 76 +++
> drivers/md/Kconfig | 30 +
> drivers/md/Makefile | 2 +
> drivers/md/dm-bht.c | 541 +++++++++++++++
> drivers/md/dm-verity.c | 1043 +++++++++++++++++++++++++++++
> drivers/md/dm-verity.h | 45 ++
> include/linux/dm-bht.h | 166 +++++
> 8 files changed, 1962 insertions(+), 0 deletions(-)
> create mode 100644 Documentation/device-mapper/dm-bht.txt
> create mode 100644 Documentation/device-mapper/dm-verity.txt
> create mode 100644 drivers/md/dm-bht.c
> create mode 100644 drivers/md/dm-verity.c
> create mode 100644 drivers/md/dm-verity.h
> create mode 100644 include/linux/dm-bht.h
>
> diff --git a/Documentation/device-mapper/dm-bht.txt b/Documentation/device-mapper/dm-bht.txt
> new file mode 100644
> index 0000000..21d929f
> --- /dev/null
> +++ b/Documentation/device-mapper/dm-bht.txt
> @@ -0,0 +1,59 @@
> +dm-bht
> +======
> +
> +dm-bht provides a block hash tree implementation. The use of dm-bht allows
> +for integrity checking of a given block device without reading the entire
> +set of blocks into memory before use.
> +
> +In particular, dm-bht supplies an interface for creating and verifying a tree
> +of cryptographic digests with any algorithm supported by the kernel crypto API.
> +
> +The `verity' target is the motivating example.
> +
> +
> +Theory of operation
> +===================
> +
> +dm-bht is logically comprised of multiple nodes organized in a tree-like
> +structure. Each node in the tree is a cryptographic hash. If it is a leaf
> +node, the hash is of some block data on disk. If it is an intermediary node,
> +then the hash is of a number of child nodes.
> +
> +dm-bht has a given depth starting at 1 (ignoring the root node). Each level in
> +the tree is concretely made up of dm_bht_entry structs. Each entry in the tree
> +is a collection of neighboring nodes that fit in one page-sized block. The
> +number is determined based on PAGE_SIZE and the size of the selected
> +cryptographic digest algorithm. The hashes are linearly ordered in this entry
> +and any unaligned trailing space is ignored but included when calculating the
> +parent node.
> +
> +The tree looks something like:
> +
> +alg= sha256, num_blocks = 32767
> + [ root ]
> + / . . . \
> + [entry_0] [entry_1]
> + / . . . \ . . . \
> + [entry_0_0] . . . [entry_0_127] . . . . [entry_1_127]
> + / ... \ / . . . \ / \
> + blk_0 ... blk_127 blk_16256 blk_16383 blk_32640 . . . blk_32767
> +
> +root is treated independently from the depth and the blocks are expected to
> +be hashed and supplied to the dm-bht. hash blocks that make up the entry
> +contents are expected to be read from disk.
> +
> +dm-bht does not handle I/O directly but instead expects the consumer to
> +supply callbacks. The read callback will always receive a page-align value
> +to pass to the block device layer to read in a hash value.
> +
> +Usage
> +=====
> +
> +The API provides mechanisms for reading and verifying a tree. When reading, all
> +required data for the hash tree should be populated for a block before
> +attempting a verify. This can be done by calling dm_bht_populate(). When all
> +data is ready, a call to dm_bht_verify_block() with the expected hash value will
> +perform both the direct block hash check and the hashes of the parent and
> +neighboring nodes where needed to ensure validity up to the root hash. Note,
> +dm_bht_set_root_hexdigest() should be called before any verification attempts
> +occur.
> diff --git a/Documentation/device-mapper/dm-verity.txt b/Documentation/device-mapper/dm-verity.txt
> new file mode 100644
> index 0000000..f33b984
> --- /dev/null
> +++ b/Documentation/device-mapper/dm-verity.txt
> @@ -0,0 +1,76 @@
> +dm-verity
> +==========
> +
> +Device-Mapper's "verity" target provides transparent integrity checking of
> +block devices using a cryptographic digest provided by the kernel crypto API.
> +This target is read-only.
> +
> +Parameters: payload=<device path> hashtree=<hash device path> alg=<alg> \
> + salt=<salt> root_hexagiest=<root hash> \
> + [ hashstart=<hash start> error_behavior=<error behavior> ]
> +
> +<device path>
> + This is the device that is going to be integrity checked. It may be
> + a subset of the full device as specified to dmsetup (start sector and count)
> + It may be specified as a path, like /dev/sdaX, or a device number,
> + <major>:<minor>.
> +
> +<hash device path>
> + This is the device that that supplies the dm-bht hash data. It may be
> + specified similarly to the device path and may be the same device. If the
> + same device is used, the hash offset should be outside of the dm-verity
> + configured device size.
> +
> +<alg>
> + The cryptographic hash algorithm used for this device. This should
> + be the name of the algorithm, like "sha1".
> +
> +<salt>
> + Salt value (in hex).
> +
> +<root hash>
> + The hexadecimal encoding of the cryptographic hash of all of the
> + neighboring nodes at the first level of the tree. This hash should be
> + trusted as there is no other authenticity beyond this point.
> +
> +<hash start>
> + Start address of hashes (default 0).
> +
> +<error behavior>
> + 0 = return -EIO. 1 = panic. 2 = none. 3 = call notifier.
> +
> +Theory of operation
> +===================
> +
> +dm-verity is meant to be setup as part of a verified boot path. This
> +may be anything ranging from a boot using tboot or trustedgrub to just
> +booting from a known-good device (like a USB drive or CD).
> +
> +When a dm-verity device is configured, it is expected that the caller
> +has been authenticated in some way (cryptographic signatures, etc).
> +After instantiation, all hashes will be verified on-demand during
> +disk access. If they cannot be verified up to the root node of the
> +tree, the root hash, then the I/O will fail. This should identify
> +tampering with any data on the device and the hash data.
> +
> +Cryptographic hashes are used to assert the integrity of the device on a
> +per-block basis. This allows for a lightweight hash computation on first read
> +into the page cache. Block hashes are stored linearly aligned to the nearest
> +block the size of a page.
> +
> +For more information on the hashing process, see dm-bht.txt.
> +
> +
> +Example
> +=======
> +
> +Setup a device;
> +[[
> + dmsetup create vroot --table \
> + "0 204800 verity payload=/dev/sda1 hashtree=/dev/sda2 alg=sha1 "\
> + "root_hexdigest=9f74809a2ee7607b16fcc70d9399a4de9725a727"
> +]]
> +
> +A command line tool is available to compute the hash tree and return the
> +root hash value.
> + http://git.chromium.org/cgi-bin/gitweb.cgi?p=dm-verity.git;a=tree
> diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
> index f75a66e..cb5f425 100644
> --- a/drivers/md/Kconfig
> +++ b/drivers/md/Kconfig
> @@ -334,4 +334,34 @@ config DM_FLAKEY
> ---help---
> A target that intermittently fails I/O for debugging purposes.
>
> +config DM_BHT
> + tristate "Block hash tree support"
> + select CRYPTO
> + select CRYPTO_HASH
> + ---help---
> + Include support for device-mapper devices to use a block hash
> + tree for managing data integrity checks in a scalable way.
> +
> + Targets that use this functionality should include it
> + automatically.
> +
> + If unsure, say N.
> +
> +config DM_VERITY
> + tristate "Verity target support"
> + depends on BLK_DEV_DM
> + select DM_BHT
> + select CRYPTO
> + select CRYPTO_HASH
> + ---help---
> + This device-mapper target allows you to create a device that
> + transparently integrity checks the data on it. You'll need to
> + activate the digests you're going to use in the cryptoapi
> + configuration.
> +
> + To compile this code as a module, choose M here: the module will
> + be called dm-verity.
> +
> + If unsure, say N.
> +
> endif # MD
> diff --git a/drivers/md/Makefile b/drivers/md/Makefile
> index 448838b..58eb088 100644
> --- a/drivers/md/Makefile
> +++ b/drivers/md/Makefile
> @@ -36,6 +36,8 @@ obj-$(CONFIG_DM_MULTIPATH_ST) += dm-service-time.o
> obj-$(CONFIG_DM_SNAPSHOT) += dm-snapshot.o
> obj-$(CONFIG_DM_MIRROR) += dm-mirror.o dm-log.o dm-region-hash.o
> obj-$(CONFIG_DM_LOG_USERSPACE) += dm-log-userspace.o
> +obj-$(CONFIG_DM_BHT) += dm-bht.o
> +obj-$(CONFIG_DM_VERITY) += dm-verity.o
> obj-$(CONFIG_DM_ZERO) += dm-zero.o
> obj-$(CONFIG_DM_RAID) += dm-raid.o
>
> diff --git a/drivers/md/dm-bht.c b/drivers/md/dm-bht.c
> new file mode 100644
> index 0000000..32b8ccf
> --- /dev/null
> +++ b/drivers/md/dm-bht.c
> @@ -0,0 +1,541 @@
> + /*
> + * Copyright (C) 2011 The Chromium OS Authors <chromium-os-dev@...omium.org>
> + *
> + * Device-Mapper block hash tree interface.
> + * See Documentation/device-mapper/dm-bht.txt for details.
> + *
> + * This file is released under the GPLv2.
> + */
> +
> +#include <linux/atomic.h>
> +#include <linux/bitops.h>
> +#include <linux/bug.h>
> +#include <linux/cpumask.h>
> +#include <linux/device-mapper.h>
> +#include <linux/dm-bht.h>
> +#include <linux/err.h>
> +#include <linux/errno.h>
> +#include <linux/gfp.h>
> +#include <linux/kernel.h>
> +#include <linux/mm_types.h>
> +#include <linux/scatterlist.h>
> +#include <linux/slab.h>
> +#include <linux/string.h>
> +
> +#define DM_MSG_PREFIX "dm bht"
> +
> +
> +/*
> + * Utilities
> + */
> +
> +static u8 from_hex(u8 ch)
> +{
> + if ((ch >= '0') && (ch <= '9'))
> + return ch - '0';
> + if ((ch >= 'a') && (ch <= 'f'))
> + return ch - 'a' + 10;
> + if ((ch >= 'A') && (ch <= 'F'))
> + return ch - 'A' + 10;
> + return -1;
> +}
> +
> +/**
> + * dm_bht_bin_to_hex - converts a binary stream to human-readable hex
> + * @binary: a byte array of length @binary_len
> + * @hex: a byte array of length @binary_len * 2 + 1
> + */
> +static void dm_bht_bin_to_hex(u8 *binary, u8 *hex, unsigned int binary_len)
> +{
> + while (binary_len-- > 0) {
> + sprintf((char *)hex, "%02hhx", (int)*binary);
> + hex += 2;
> + binary++;
> + }
> +}
> +
> +/**
> + * dm_bht_hex_to_bin - converts a hex stream to binary
> + * @binary: a byte array of length @binary_len
> + * @hex: a byte array of length @binary_len * 2 + 1
> + */
> +static void dm_bht_hex_to_bin(u8 *binary, const u8 *hex,
> + unsigned int binary_len)
> +{
> + while (binary_len-- > 0) {
> + *binary = from_hex(*(hex++));
> + *binary *= 16;
> + *binary += from_hex(*(hex++));
> + binary++;
> + }
> +}
> +
> +static void dm_bht_log_mismatch(struct dm_bht *bht, u8 *given, u8 *computed)
> +{
> + u8 given_hex[DM_BHT_MAX_DIGEST_SIZE * 2 + 1];
> + u8 computed_hex[DM_BHT_MAX_DIGEST_SIZE * 2 + 1];
> +
> + dm_bht_bin_to_hex(given, given_hex, bht->digest_size);
> + dm_bht_bin_to_hex(computed, computed_hex, bht->digest_size);
> + DMERR_LIMIT("%s != %s", given_hex, computed_hex);
> +}
> +
> +/**
> + * dm_bht_compute_hash: hashes a page of data
> + */
> +static int dm_bht_compute_hash(struct dm_bht *bht, struct page *pg,
> + unsigned int offset, u8 *digest)
> +{
> + struct hash_desc *hash_desc = &bht->hash_desc[smp_processor_id()];
> + struct scatterlist sg;
> +
> + sg_init_table(&sg, 1);
> + sg_set_page(&sg, pg, bht->block_size, offset);
> + /* Note, this is synchronous. */
> + if (crypto_hash_init(hash_desc)) {
> + DMCRIT("failed to reinitialize crypto hash (proc:%d)",
> + smp_processor_id());
> + return -EINVAL;
> + }
> + if (crypto_hash_update(hash_desc, &sg, bht->block_size)) {
> + DMCRIT("crypto_hash_update failed");
> + return -EINVAL;
> + }
> + sg_set_buf(&sg, bht->salt, sizeof(bht->salt));
> + if (crypto_hash_update(hash_desc, &sg, sizeof(bht->salt))) {
> + DMCRIT("crypto_hash_update failed");
> + return -EINVAL;
> + }
> + if (crypto_hash_final(hash_desc, digest)) {
> + DMCRIT("crypto_hash_final failed");
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> +/*
> + * Implementation functions
> + */
> +
> +static int dm_bht_initialize_entries(struct dm_bht *bht)
> +{
> + /* last represents the index of the last digest store in the tree.
> + * By walking the tree with that index, it is possible to compute the
> + * total number of entries at each level.
> + *
> + * Since each entry will contain up to |node_count| nodes of the tree,
> + * it is possible that the last index may not be at the end of a given
> + * entry->nodes. In that case, it is assumed the value is padded.
> + *
> + * Note, we treat both the tree root (1 hash) and the tree leaves
> + * independently from the bht data structures. Logically, the root is
> + * depth=-1 and the block layer level is depth=bht->depth
> + */
> + unsigned int last = bht->block_count;
> + int depth;
> +
> + /* check that the largest level->count can't result in an int overflow
> + * on allocation or sector calculation.
> + */
> + if (((last >> bht->node_count_shift) + 1) >
> + UINT_MAX / max((unsigned int)sizeof(struct dm_bht_entry),
> + (unsigned int)to_sector(bht->block_size))) {
> + DMCRIT("required entries %u is too large", last + 1);
> + return -EINVAL;
> + }
> +
> + /* Track the current sector location for each level so we don't have to
> + * compute it during traversals.
> + */
> + bht->sectors = 0;
> + for (depth = 0; depth < bht->depth; ++depth) {
> + struct dm_bht_level *level = &bht->levels[depth];
> +
> + level->count = dm_bht_index_at_level(bht, depth, last) + 1;
> + level->entries = (struct dm_bht_entry *)
> + kcalloc(level->count,
> + sizeof(struct dm_bht_entry),
> + GFP_KERNEL);
> + if (!level->entries) {
> + DMERR("failed to allocate entries for depth %d", depth);
> + return -ENOMEM;
> + }
> + level->sector = bht->sectors;
> + bht->sectors += level->count * to_sector(bht->block_size);
> + }
> +
> + return 0;
> +}
> +
> +/**
> + * dm_bht_create - prepares @bht for us
> + * @bht: pointer to a dm_bht_create()d bht
> + * @depth: tree depth without the root; including block hashes
> + * @block_count:the number of block hashes / tree leaves
> + * @alg_name: crypto hash algorithm name
> + *
> + * Returns 0 on success.
> + *
> + * Callers can offset into devices by storing the data in the io callbacks.
> + */
> +int dm_bht_create(struct dm_bht *bht, unsigned int block_count,
> + unsigned int block_size, const char *alg_name)
> +{
> + int cpu, status;
> +
> + bht->block_size = block_size;
> + /* Verify that PAGE_SIZE >= block_size >= SECTOR_SIZE. */
> + if ((block_size > PAGE_SIZE) ||
> + (PAGE_SIZE % block_size) ||
> + (to_sector(block_size) == 0))
> + return -EINVAL;
> +
> + /* Setup the hash first. Its length determines much of the bht layout */
> + for (cpu = 0; cpu < nr_cpu_ids; ++cpu) {
> + bht->hash_desc[cpu].tfm = crypto_alloc_hash(alg_name, 0, 0);
> + if (IS_ERR(bht->hash_desc[cpu].tfm)) {
> + DMERR("failed to allocate crypto hash '%s'", alg_name);
> + status = -ENOMEM;
> + bht->hash_desc[cpu].tfm = NULL;
> + goto bad_arg;
> + }
> + }
> + bht->digest_size = crypto_hash_digestsize(bht->hash_desc[0].tfm);
> + /* We expect to be able to pack >=2 hashes into a block */
> + if (block_size / bht->digest_size < 2) {
> + DMERR("too few hashes fit in a block");
> + status = -EINVAL;
> + goto bad_arg;
> + }
> +
> + if (bht->digest_size > DM_BHT_MAX_DIGEST_SIZE) {
> + DMERR("DM_BHT_MAX_DIGEST_SIZE too small for chosen digest");
> + status = -EINVAL;
> + goto bad_arg;
> + }
> +
> + /* Configure the tree */
> + bht->block_count = block_count;
> + if (block_count == 0) {
> + DMERR("block_count must be non-zero");
> + status = -EINVAL;
> + goto bad_arg;
> + }
> +
> + /* Each dm_bht_entry->nodes is one block. The node code tracks
> + * how many nodes fit into one entry where a node is a single
> + * hash (message digest).
> + */
> + bht->node_count_shift = fls(block_size / bht->digest_size) - 1;
> + /* Round down to the nearest power of two. This makes indexing
> + * into the tree much less painful.
> + */
> + bht->node_count = 1 << bht->node_count_shift;
> +
> + /* This is unlikely to happen, but with 64k pages, who knows. */
> + if (bht->node_count > UINT_MAX / bht->digest_size) {
> + DMERR("node_count * hash_len exceeds UINT_MAX!");
> + status = -EINVAL;
> + goto bad_arg;
> + }
> +
> + bht->depth = DIV_ROUND_UP(fls(block_count - 1), bht->node_count_shift);
> +
> + /* Ensure that we can safely shift by this value. */
> + if (bht->depth * bht->node_count_shift >= sizeof(unsigned int) * 8) {
> + DMERR("specified depth and node_count_shift is too large");
> + status = -EINVAL;
> + goto bad_arg;
> + }
> +
> + /* Allocate levels. Each level of the tree may have an arbitrary number
> + * of dm_bht_entry structs. Each entry contains node_count nodes.
> + * Each node in the tree is a cryptographic digest of either node_count
> + * nodes on the subsequent level or of a specific block on disk.
> + */
> + bht->levels = (struct dm_bht_level *)
> + kcalloc(bht->depth,
> + sizeof(struct dm_bht_level), GFP_KERNEL);
> + if (!bht->levels) {
> + DMERR("failed to allocate tree levels");
> + status = -ENOMEM;
> + goto bad_level_alloc;
> + }
> +
> + bht->read_cb = NULL;
> +
> + status = dm_bht_initialize_entries(bht);
> + if (status)
> + goto bad_entries_alloc;
> +
> + /* We compute depth such that there is only be 1 block at level 0. */
> + BUG_ON(bht->levels[0].count != 1);
> +
> + return 0;
> +
> +bad_entries_alloc:
> + while (bht->depth-- > 0)
> + kfree(bht->levels[bht->depth].entries);
> + kfree(bht->levels);
> +bad_level_alloc:
> +bad_arg:
> + for (cpu = 0; cpu < nr_cpu_ids; ++cpu)
> + if (bht->hash_desc[cpu].tfm)
> + crypto_free_hash(bht->hash_desc[cpu].tfm);
> + return status;
> +}
> +EXPORT_SYMBOL(dm_bht_create);
> +
> +/**
> + * dm_bht_read_completed
> + * @entry: pointer to the entry that's been loaded
> + * @status: I/O status. Non-zero is failure.
> + * MUST always be called after a read_cb completes.
> + */
> +void dm_bht_read_completed(struct dm_bht_entry *entry, int status)
> +{
> + if (status) {
> + /* TODO(wad) add retry support */
> + DMCRIT("an I/O error occurred while reading entry");
> + atomic_set(&entry->state, DM_BHT_ENTRY_ERROR_IO);
> + /* entry->nodes will be freed later */
> + return;
> + }
> + BUG_ON(atomic_read(&entry->state) != DM_BHT_ENTRY_PENDING);
> + atomic_set(&entry->state, DM_BHT_ENTRY_READY);
> +}
> +EXPORT_SYMBOL(dm_bht_read_completed);
> +
> +/**
> + * dm_bht_verify_block - checks that all nodes in the path for @block are valid
> + * @bht: pointer to a dm_bht_create()d bht
> + * @block: specific block data is expected from
> + * @pg: page holding the block data
> + * @offset: offset into the page
> + *
> + * Returns 0 on success, DM_BHT_ENTRY_ERROR_MISMATCH on error.
> + */
> +int dm_bht_verify_block(struct dm_bht *bht, unsigned int block,
> + struct page *pg, unsigned int offset)
> +{
> + int state, depth = bht->depth;
> + u8 digest[DM_BHT_MAX_DIGEST_SIZE];
> + struct dm_bht_entry *entry;
> + void *node;
> +
> + do {
> + /* Need to check that the hash of the current block is accurate
> + * in its parent.
> + */
> + entry = dm_bht_get_entry(bht, depth - 1, block);
> + state = atomic_read(&entry->state);
> + /* This call is only safe if all nodes along the path
> + * are already populated (i.e. READY) via dm_bht_populate.
> + */
> + BUG_ON(state < DM_BHT_ENTRY_READY);
> + node = dm_bht_get_node(bht, entry, depth, block);
> +
> + if (dm_bht_compute_hash(bht, pg, offset, digest) ||
> + memcmp(digest, node, bht->digest_size))
> + goto mismatch;
> +
> + /* Keep the containing block of hashes to be verified in the
> + * next pass.
> + */
> + pg = virt_to_page(entry->nodes);
> + offset = offset_in_page(entry->nodes);
> + } while (--depth > 0 && state != DM_BHT_ENTRY_VERIFIED);
> +
> + if (depth == 0 && state != DM_BHT_ENTRY_VERIFIED) {
> + if (dm_bht_compute_hash(bht, pg, offset, digest) ||
> + memcmp(digest, bht->root_digest, bht->digest_size))
> + goto mismatch;
> + atomic_set(&entry->state, DM_BHT_ENTRY_VERIFIED);
> + }
> +
> + /* Mark path to leaf as verified. */
> + for (depth++; depth < bht->depth; depth++) {
> + entry = dm_bht_get_entry(bht, depth, block);
> + /* At this point, entry can only be in VERIFIED or READY state.
> + * So it is safe to use atomic_set instead of atomic_cmpxchg.
> + */
> + atomic_set(&entry->state, DM_BHT_ENTRY_VERIFIED);
> + }
> +
> + return 0;
> +
> +mismatch:
> + DMERR_LIMIT("verify_path: failed to verify hash (d=%d,bi=%u)",
> + depth, block);
> + dm_bht_log_mismatch(bht, node, digest);
> + return DM_BHT_ENTRY_ERROR_MISMATCH;
> +}
> +EXPORT_SYMBOL(dm_bht_verify_block);
> +
> +/**
> + * dm_bht_is_populated - check that entries from disk needed to verify a given
> + * block are all ready
> + * @bht: pointer to a dm_bht_create()d bht
> + * @block: specific block data is expected from
> + *
> + * Callers may wish to call dm_bht_is_populated() when checking an io
> + * for which entries were already pending.
> + */
> +bool dm_bht_is_populated(struct dm_bht *bht, unsigned int block)
> +{
> + int depth;
> +
> + for (depth = bht->depth - 1; depth >= 0; depth--) {
> + struct dm_bht_entry *entry = dm_bht_get_entry(bht, depth,
> + block);
> + if (atomic_read(&entry->state) < DM_BHT_ENTRY_READY)
> + return false;
> + }
> +
> + return true;
> +}
> +EXPORT_SYMBOL(dm_bht_is_populated);
> +
> +/**
> + * dm_bht_populate - reads entries from disk needed to verify a given block
> + * @bht: pointer to a dm_bht_create()d bht
> + * @ctx: context used for all read_cb calls on this request
> + * @block: specific block data is expected from
> + *
> + * Returns negative value on error. Returns 0 on success.
> + */
> +int dm_bht_populate(struct dm_bht *bht, void *ctx, unsigned int block)
> +{
> + int depth, state;
> +
> + BUG_ON(block >= bht->block_count);
> +
> + for (depth = bht->depth - 1; depth >= 0; --depth) {
> + unsigned int index = dm_bht_index_at_level(bht, depth, block);
> + struct dm_bht_level *level = &bht->levels[depth];
> + struct dm_bht_entry *entry = dm_bht_get_entry(bht, depth,
> + block);
> + state = atomic_cmpxchg(&entry->state,
> + DM_BHT_ENTRY_UNALLOCATED,
> + DM_BHT_ENTRY_PENDING);
> + if (state == DM_BHT_ENTRY_VERIFIED)
> + break;
> + if (state <= DM_BHT_ENTRY_ERROR)
> + goto error_state;
> + if (state != DM_BHT_ENTRY_UNALLOCATED)
> + continue;
> +
> + /* Current entry is claimed for allocation and loading */
> + entry->nodes = kmalloc(bht->block_size, GFP_NOIO);
> + if (!entry->nodes)
> + goto nomem;
> +
> + bht->read_cb(ctx,
> + level->sector + to_sector(index * bht->block_size),
> + entry->nodes, to_sector(bht->block_size), entry);
> + }
> +
> + return 0;
> +
> +error_state:
> + DMCRIT("block %u at depth %d is in an error state", block, depth);
> + return -EPERM;
> +
> +nomem:
> + DMCRIT("failed to allocate memory for entry->nodes");
> + return -ENOMEM;
> +}
> +EXPORT_SYMBOL(dm_bht_populate);
> +
> +/**
> + * dm_bht_destroy - cleans up all memory used by @bht
> + * @bht: pointer to a dm_bht_create()d bht
> + */
> +void dm_bht_destroy(struct dm_bht *bht)
> +{
> + int depth, cpu;
> +
> + for (depth = 0; depth < bht->depth; depth++) {
> + struct dm_bht_entry *entry = bht->levels[depth].entries;
> + struct dm_bht_entry *entry_end = entry +
> + bht->levels[depth].count;
> + for (; entry < entry_end; ++entry)
> + kfree(entry->nodes);
> + kfree(bht->levels[depth].entries);
> + }
> + kfree(bht->levels);
> + for (cpu = 0; cpu < nr_cpu_ids; ++cpu)
> + if (bht->hash_desc[cpu].tfm)
> + crypto_free_hash(bht->hash_desc[cpu].tfm);
> +}
> +EXPORT_SYMBOL(dm_bht_destroy);
> +
> +/*
> + * Accessors
> + */
> +
> +/**
> + * dm_bht_set_root_hexdigest - sets an unverified root digest hash from hex
> + * @bht: pointer to a dm_bht_create()d bht
> + * @hexdigest: array of u8s containing the new digest in binary
> + * Returns non-zero on error. hexdigest should be NUL terminated.
> + */
> +int dm_bht_set_root_hexdigest(struct dm_bht *bht, const u8 *hexdigest)
> +{
> + /* Make sure we have at least the bytes expected */
> + if (strnlen((char *)hexdigest, bht->digest_size * 2) !=
> + bht->digest_size * 2) {
> + DMERR("root digest length does not match hash algorithm");
> + return -1;
> + }
> + dm_bht_hex_to_bin(bht->root_digest, hexdigest, bht->digest_size);
> + return 0;
> +}
> +EXPORT_SYMBOL(dm_bht_set_root_hexdigest);
> +
> +/**
> + * dm_bht_root_hexdigest - returns root digest in hex
> + * @bht: pointer to a dm_bht_create()d bht
> + * @hexdigest: u8 array of size @available
> + * @available: must be bht->digest_size * 2 + 1
> + */
> +int dm_bht_root_hexdigest(struct dm_bht *bht, u8 *hexdigest, int available)
> +{
> + if (available < 0 ||
> + ((unsigned int) available) < bht->digest_size * 2 + 1) {
> + DMERR("hexdigest has too few bytes available");
> + return -EINVAL;
> + }
> + dm_bht_bin_to_hex(bht->root_digest, hexdigest, bht->digest_size);
> + return 0;
> +}
> +EXPORT_SYMBOL(dm_bht_root_hexdigest);
> +
> +/**
> + * dm_bht_set_salt - sets the salt used, in hex
> + * @bht: pointer to a dm_bht_create()d bht
> + * @hexsalt: salt string, as hex; will be zero-padded or truncated to
> + * DM_BHT_SALT_SIZE * 2 hex digits.
> + */
> +void dm_bht_set_salt(struct dm_bht *bht, const char *hexsalt)
> +{
> + size_t saltlen = min(strlen(hexsalt) / 2, sizeof(bht->salt));
> +
> + memset(bht->salt, 0, sizeof(bht->salt));
> + dm_bht_hex_to_bin(bht->salt, (const u8 *)hexsalt, saltlen);
> +}
> +EXPORT_SYMBOL(dm_bht_set_salt);
> +
> +/**
> + * dm_bht_salt - returns the salt used, in hex
> + * @bht: pointer to a dm_bht_create()d bht
> + * @hexsalt: buffer to put salt into, of length DM_BHT_SALT_SIZE * 2 + 1.
> + */
> +int dm_bht_salt(struct dm_bht *bht, char *hexsalt)
> +{
> + dm_bht_bin_to_hex(bht->salt, (u8 *)hexsalt, sizeof(bht->salt));
> + return 0;
> +}
> +EXPORT_SYMBOL(dm_bht_salt);
> +
> diff --git a/drivers/md/dm-verity.c b/drivers/md/dm-verity.c
> new file mode 100644
> index 0000000..a9bd0e8
> --- /dev/null
> +++ b/drivers/md/dm-verity.c
> @@ -0,0 +1,1043 @@
> +/*
> + * Originally based on dm-crypt.c,
> + * Copyright (C) 2003 Christophe Saout <christophe@...ut.de>
> + * Copyright (C) 2004 Clemens Fruhwirth <clemens@...orphin.org>
> + * Copyright (C) 2006-2008 Red Hat, Inc. All rights reserved.
> + * Copyright (C) 2011 The Chromium OS Authors <chromium-os-dev@...omium.org>
> + * All Rights Reserved.
> + *
> + * This file is released under the GPLv2.
> + *
> + * Implements a verifying transparent block device.
> + * See Documentation/device-mapper/dm-verity.txt
> + */
> +#include <linux/async.h>
> +#include <linux/atomic.h>
> +#include <linux/bio.h>
> +#include <linux/blkdev.h>
> +#include <linux/delay.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/genhd.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/mempool.h>
> +#include <linux/mm_types.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/workqueue.h>
> +#include <linux/device-mapper.h>
> +#include <linux/dm-bht.h>
> +
> +#include "dm-verity.h"
> +
> +#define DM_MSG_PREFIX "verity"
> +
> +/* Supports up to 512-bit digests */
> +#define VERITY_MAX_DIGEST_SIZE 64
> +
> +/* TODO(wad) make both of these report the error line/file to a
> + * verity_bug function.
> + */
> +#define VERITY_BUG(msg...) BUG()
> +#define VERITY_BUG_ON(cond, msg...) BUG_ON(cond)
> +
> +/* Helper for printing sector_t */
> +#define ULL(x) ((unsigned long long)(x))
> +
> +#define MIN_IOS 32
> +#define MIN_BIOS (MIN_IOS * 2)
> +#define VERITY_DEFAULT_BLOCK_SIZE 4096
> +
> +/* Provide a lightweight means of specifying the global default for
> + * error behavior: eio, reboot, or none
> + * Legacy support for 0 = eio, 1 = reboot/panic, 2 = none, 3 = notify.
> + * This is matched to the enum in dm-verity.h.
> + */
> +static const char * const allowed_error_behaviors[] = { "eio", "panic", "none",
> + "notify", NULL };
> +static char *error_behavior = "eio";
> +module_param(error_behavior, charp, 0644);
> +MODULE_PARM_DESC(error_behavior, "Behavior on error "
> + "(eio, panic, none, notify)");
> +
> +/* Controls whether verity_get_device will wait forever for a device. */
> +static int dev_wait;
> +module_param(dev_wait, bool, 0444);
> +MODULE_PARM_DESC(dev_wait, "Wait forever for a backing device");
> +
> +/* per-requested-bio private data */
> +enum verity_io_flags {
> + VERITY_IOFLAGS_CLONED = 0x1, /* original bio has been cloned */
> +};
> +
> +struct dm_verity_io {
> + struct dm_target *target;
> + struct bio *bio;
> + struct delayed_work work;
> + unsigned int flags;
> +
> + int error;
> + atomic_t pending;
> +
> + u64 block; /* aligned block index */
> + u64 count; /* aligned count in blocks */
> +};
> +
> +struct verity_config {
> + struct dm_dev *dev;
> + sector_t start;
> + sector_t size;
> +
> + struct dm_dev *hash_dev;
> + sector_t hash_start;
> +
> + struct dm_bht bht;
> +
> + /* Pool required for io contexts */
> + mempool_t *io_pool;
> + /* Pool and bios required for making sure that backing device reads are
> + * in PAGE_SIZE increments.
> + */
> + struct bio_set *bs;
> +
> + char hash_alg[CRYPTO_MAX_ALG_NAME];
> +
> + int error_behavior;
> +};
> +
> +static struct kmem_cache *_verity_io_pool;
> +static struct workqueue_struct *kveritydq, *kverityd_ioq;
> +
> +static void kverityd_verify(struct work_struct *work);
> +static void kverityd_io(struct work_struct *work);
> +static void kverityd_io_bht_populate(struct dm_verity_io *io);
> +static void kverityd_io_bht_populate_end(struct bio *, int error);
> +
> +static BLOCKING_NOTIFIER_HEAD(verity_error_notifier);
> +
> +/*
> + * Exported interfaces
> + */
> +
> +int dm_verity_register_error_notifier(struct notifier_block *nb)
> +{
> + return blocking_notifier_chain_register(&verity_error_notifier, nb);
> +}
> +EXPORT_SYMBOL_GPL(dm_verity_register_error_notifier);
> +
> +int dm_verity_unregister_error_notifier(struct notifier_block *nb)
> +{
> + return blocking_notifier_chain_unregister(&verity_error_notifier, nb);
> +}
> +EXPORT_SYMBOL_GPL(dm_verity_unregister_error_notifier);
> +
> +/*
> + * Allocation and utility functions
> + */
> +
> +static void kverityd_src_io_read_end(struct bio *clone, int error);
> +
> +/* Shared destructor for all internal bios */
> +static void dm_verity_bio_destructor(struct bio *bio)
> +{
> + struct dm_verity_io *io = bio->bi_private;
> + struct verity_config *vc = io->target->private;
> + bio_free(bio, vc->bs);
> +}
> +
> +static struct bio *verity_alloc_bioset(struct verity_config *vc, gfp_t gfp_mask,
> + int nr_iovecs)
> +{
> + return bio_alloc_bioset(gfp_mask, nr_iovecs, vc->bs);
> +}
> +
> +static struct dm_verity_io *verity_io_alloc(struct dm_target *ti,
> + struct bio *bio)
> +{
> + struct verity_config *vc = ti->private;
> + sector_t sector = bio->bi_sector - ti->begin;
> + struct dm_verity_io *io;
> +
> + io = mempool_alloc(vc->io_pool, GFP_NOIO);
> + if (unlikely(!io))
> + return NULL;
> + io->flags = 0;
> + io->target = ti;
> + io->bio = bio;
> + io->error = 0;
> +
> + /* Adjust the sector by the virtual starting sector */
> + io->block = to_bytes(sector) / vc->bht.block_size;
> + io->count = bio->bi_size / vc->bht.block_size;
> +
> + atomic_set(&io->pending, 0);
> +
> + return io;
> +}
> +
> +static struct bio *verity_bio_clone(struct dm_verity_io *io)
> +{
> + struct verity_config *vc = io->target->private;
> + struct bio *bio = io->bio;
> + struct bio *clone = verity_alloc_bioset(vc, GFP_NOIO, bio->bi_max_vecs);
> +
> + if (!clone)
> + return NULL;
> +
> + __bio_clone(clone, bio);
> + clone->bi_private = io;
> + clone->bi_end_io = kverityd_src_io_read_end;
> + clone->bi_bdev = vc->dev->bdev;
> + clone->bi_sector += vc->start - io->target->begin;
> + clone->bi_destructor = dm_verity_bio_destructor;
> +
> + return clone;
> +}
> +
> +/* If the request is not successful, this handler takes action.
> + * TODO make this call a registered handler.
> + */
> +static void verity_error(struct verity_config *vc, struct dm_verity_io *io,
> + int error)
> +{
> + const char *message;
> + int error_mode = DM_VERITY_ERROR_BEHAVIOR_PANIC;
> + dev_t devt = 0;
> + u64 block = ~0;
> + int transient = 1;
> + struct dm_verity_error_state error_state;
> +
> + if (vc) {
> + devt = vc->dev->bdev->bd_dev;
> + error_mode = vc->error_behavior;
> + }
> +
> + if (io) {
> + io->error = -EIO;
> + block = io->block;
> + }
> +
> + switch (error) {
> + case -ENOMEM:
> + message = "out of memory";
> + break;
> + case -EBUSY:
> + message = "pending data seen during verify";
> + break;
> + case -EFAULT:
> + message = "crypto operation failure";
> + break;
> + case -EACCES:
> + message = "integrity failure";
> + /* Image is bad. */
> + transient = 0;
> + break;
> + case -EPERM:
> + message = "hash tree population failure";
> + /* Should be dm-bht specific errors */
> + transient = 0;
> + break;
> + case -EINVAL:
> + message = "unexpected missing/invalid data";
> + /* The device was configured incorrectly - fallback. */
> + transient = 0;
> + break;
> + default:
> + /* Other errors can be passed through as IO errors */
> + message = "unknown or I/O error";
> + return;
> + }
> +
> + DMERR_LIMIT("verification failure occurred: %s", message);
> +
> + if (error_mode == DM_VERITY_ERROR_BEHAVIOR_NOTIFY) {
> + error_state.code = error;
> + error_state.transient = transient;
> + error_state.block = block;
> + error_state.message = message;
> + error_state.dev_start = vc->start;
> + error_state.dev_len = vc->size;
> + error_state.dev = vc->dev->bdev;
> + error_state.hash_dev_start = vc->hash_start;
> + error_state.hash_dev_len = vc->bht.sectors;
> + error_state.hash_dev = vc->hash_dev->bdev;
> +
> + /* Set default fallthrough behavior. */
> + error_state.behavior = DM_VERITY_ERROR_BEHAVIOR_PANIC;
> + error_mode = DM_VERITY_ERROR_BEHAVIOR_PANIC;
> +
> + if (!blocking_notifier_call_chain(
> + &verity_error_notifier, transient, &error_state)) {
> + error_mode = error_state.behavior;
> + }
> + }
> +
> + switch (error_mode) {
> + case DM_VERITY_ERROR_BEHAVIOR_EIO:
> + break;
> + case DM_VERITY_ERROR_BEHAVIOR_NONE:
> + if (error != -EIO && io)
> + io->error = 0;
> + break;
> + default:
> + goto do_panic;
> + }
> + return;
> +
> +do_panic:
> + panic("dm-verity failure: "
> + "device:%u:%u error:%d block:%llu message:%s",
> + MAJOR(devt), MINOR(devt), error, ULL(block), message);
> +}
> +
> +/**
> + * verity_parse_error_behavior - parse a behavior charp to the enum
> + * @behavior: NUL-terminated char array
> + *
> + * Checks if the behavior is valid either as text or as an index digit
> + * and returns the proper enum value or -1 on error.
> + */
> +static int verity_parse_error_behavior(const char *behavior)
> +{
> + const char * const *allowed = allowed_error_behaviors;
> + char index = '0';
> +
> + for (; *allowed; allowed++, index++)
> + if (!strcmp(*allowed, behavior) || behavior[0] == index)
> + break;
> +
> + if (!*allowed)
> + return -1;
> +
> + /* Convert to the integer index matching the enum. */
> + return allowed - allowed_error_behaviors;
> +}
> +
> +/*
> + * Reverse flow of requests into the device.
> + *
> + * (Start at the bottom with verity_map and work your way upward).
> + */
> +
> +static void verity_inc_pending(struct dm_verity_io *io);
> +
> +static void verity_return_bio_to_caller(struct dm_verity_io *io)
> +{
> + struct verity_config *vc = io->target->private;
> +
> + if (io->error)
> + verity_error(vc, io, io->error);
> +
> + bio_endio(io->bio, io->error);
> + mempool_free(io, vc->io_pool);
> +}
> +
> +/* Check for any missing bht hashes. */
> +static bool verity_is_bht_populated(struct dm_verity_io *io)
> +{
> + struct verity_config *vc = io->target->private;
> + u64 block;
> +
> + for (block = io->block; block < io->block + io->count; ++block)
> + if (!dm_bht_is_populated(&vc->bht, block))
> + return false;
> +
> + return true;
> +}
> +
> +/* verity_dec_pending manages the lifetime of all dm_verity_io structs.
> + * Non-bug error handling is centralized through this interface and
> + * all passage from workqueue to workqueue.
> + */
> +static void verity_dec_pending(struct dm_verity_io *io)
> +{
> + if (!atomic_dec_and_test(&io->pending))
> + goto done;
> +
> + if (unlikely(io->error))
> + goto io_error;
> +
> + /* I/Os that were pending may now be ready */
> + if (verity_is_bht_populated(io)) {
> + INIT_DELAYED_WORK(&io->work, kverityd_verify);
> + queue_delayed_work(kveritydq, &io->work, 0);
> + } else {
> + INIT_DELAYED_WORK(&io->work, kverityd_io);
> + queue_delayed_work(kverityd_ioq, &io->work, HZ/10);
> + }
> +
> +done:
> + return;
> +
> +io_error:
> + verity_return_bio_to_caller(io);
> +}
> +
> +/* Walks the data set and computes the hash of the data read from the
> + * untrusted source device. The computed hash is then passed to dm-bht
> + * for verification.
> + */
> +static int verity_verify(struct verity_config *vc,
> + struct dm_verity_io *io)
> +{
> + unsigned int block_size = vc->bht.block_size;
> + struct bio *bio = io->bio;
> + u64 block = io->block;
> + unsigned int idx;
> + int r;
> +
> + for (idx = bio->bi_idx; idx < bio->bi_vcnt; idx++) {
> + struct bio_vec *bv = bio_iovec_idx(bio, idx);
> + unsigned int offset = bv->bv_offset;
> + unsigned int len = bv->bv_len;
> +
> + VERITY_BUG_ON(offset % block_size);
> + VERITY_BUG_ON(len % block_size);
> +
> + while (len) {
> + r = dm_bht_verify_block(&vc->bht, block,
> + bv->bv_page, offset);
> + if (r)
> + goto bad_return;
> +
> + offset += block_size;
> + len -= block_size;
> + block++;
> + cond_resched();
> + }
> + }
> +
> + return 0;
> +
> +bad_return:
> + /* dm_bht functions aren't expected to return errno friendly
> + * values. They are converted here for uniformity.
> + */
> + if (r > 0) {
> + DMERR("Pending data for block %llu seen at verify", ULL(block));
> + r = -EBUSY;
> + } else {
> + DMERR_LIMIT("Block hash does not match!");
> + r = -EACCES;
> + }
> + return r;
> +}
> +
> +/* Services the verify workqueue */
> +static void kverityd_verify(struct work_struct *work)
> +{
> + struct delayed_work *dwork = container_of(work, struct delayed_work,
> + work);
> + struct dm_verity_io *io = container_of(dwork, struct dm_verity_io,
> + work);
> + struct verity_config *vc = io->target->private;
> +
> + io->error = verity_verify(vc, io);
> +
> + /* Free up the bio and tag with the return value */
> + verity_return_bio_to_caller(io);
> +}
> +
> +/* Asynchronously called upon the completion of dm-bht I/O. The status
> + * of the operation is passed back to dm-bht and the next steps are
> + * decided by verity_dec_pending.
> + */
> +static void kverityd_io_bht_populate_end(struct bio *bio, int error)
> +{
> + struct dm_bht_entry *entry = (struct dm_bht_entry *) bio->bi_private;
> + struct dm_verity_io *io = (struct dm_verity_io *) entry->io_context;
> +
> + /* Tell the tree to atomically update now that we've populated
> + * the given entry.
> + */
> + dm_bht_read_completed(entry, error);
> +
> + /* Clean up for reuse when reading data to be checked */
> + bio->bi_vcnt = 0;
> + bio->bi_io_vec->bv_offset = 0;
> + bio->bi_io_vec->bv_len = 0;
> + bio->bi_io_vec->bv_page = NULL;
> + /* Restore the private data to I/O so the destructor can be shared. */
> + bio->bi_private = (void *) io;
> + bio_put(bio);
> +
> + /* We bail but assume the tree has been marked bad. */
> + if (unlikely(error)) {
> + DMERR("Failed to read for sector %llu (%u)",
> + ULL(io->bio->bi_sector), io->bio->bi_size);
> + io->error = error;
> + /* Pass through the error to verity_dec_pending below */
> + }
> + /* When pending = 0, it will transition to reading real data */
> + verity_dec_pending(io);
> +}
> +
> +/* Called by dm-bht (via dm_bht_populate), this function provides
> + * the message digests to dm-bht that are stored on disk.
> + */
> +static int kverityd_bht_read_callback(void *ctx, sector_t start, u8 *dst,
> + sector_t count,
> + struct dm_bht_entry *entry)
> +{
> + struct dm_verity_io *io = ctx; /* I/O for this batch */
> + struct verity_config *vc;
> + struct bio *bio;
> +
> + vc = io->target->private;
> +
> + /* The I/O context is nested inside the entry so that we don't need one
> + * io context per page read.
> + */
> + entry->io_context = ctx;
> +
> + /* We should only get page size requests at present. */
> + verity_inc_pending(io);
> + bio = verity_alloc_bioset(vc, GFP_NOIO, 1);
> + if (unlikely(!bio)) {
> + DMCRIT("Out of memory at bio_alloc_bioset");
> + dm_bht_read_completed(entry, -ENOMEM);
> + return -ENOMEM;
> + }
> + bio->bi_private = (void *) entry;
> + bio->bi_idx = 0;
> + bio->bi_size = vc->bht.block_size;
> + bio->bi_sector = vc->hash_start + start;
> + bio->bi_bdev = vc->hash_dev->bdev;
> + bio->bi_end_io = kverityd_io_bht_populate_end;
> + bio->bi_rw = REQ_META;
> + /* Only need to free the bio since the page is managed by bht */
> + bio->bi_destructor = dm_verity_bio_destructor;
> + bio->bi_vcnt = 1;
> + bio->bi_io_vec->bv_offset = offset_in_page(dst);
> + bio->bi_io_vec->bv_len = to_bytes(count);
> + /* dst is guaranteed to be a page_pool allocation */
> + bio->bi_io_vec->bv_page = virt_to_page(dst);
> + /* Track that this I/O is in use. There should be no risk of the io
> + * being removed prior since this is called synchronously.
> + */
> + generic_make_request(bio);
> + return 0;
> +}
> +
> +/* Submits an io request for each missing block of block hashes.
> + * The last one to return will then enqueue this on the io workqueue.
> + */
> +static void kverityd_io_bht_populate(struct dm_verity_io *io)
> +{
> + struct verity_config *vc = io->target->private;
> + u64 block;
> +
> + for (block = io->block; block < io->block + io->count; ++block) {
> + int ret = dm_bht_populate(&vc->bht, io, block);
> +
> + if (ret < 0) {
> + /* verity_dec_pending will handle the error case. */
> + io->error = ret;
> + break;
> + }
> + }
> +}
> +
> +/* Asynchronously called upon the completion of I/O issued
> + * from kverityd_src_io_read. verity_dec_pending() acts as
> + * the scheduler/flow manager.
> + */
> +static void kverityd_src_io_read_end(struct bio *clone, int error)
> +{
> + struct dm_verity_io *io = clone->bi_private;
> +
> + if (unlikely(!bio_flagged(clone, BIO_UPTODATE) && !error))
> + error = -EIO;
> +
> + if (unlikely(error)) {
> + DMERR("Error occurred: %d (%llu, %u)",
> + error, ULL(clone->bi_sector), clone->bi_size);
> + io->error = error;
> + }
> +
> + /* Release the clone which just avoids the block layer from
> + * leaving offsets, etc in unexpected states.
> + */
> + bio_put(clone);
> +
> + verity_dec_pending(io);
> +}
> +
> +/* If not yet underway, an I/O request will be issued to the vc->dev
> + * device for the data needed. It is cloned to avoid unexpected changes
> + * to the original bio struct.
> + */
> +static void kverityd_src_io_read(struct dm_verity_io *io)
> +{
> + struct bio *clone;
> +
> + /* Check if the read is already issued. */
> + if (io->flags & VERITY_IOFLAGS_CLONED)
> + return;
> +
> + io->flags |= VERITY_IOFLAGS_CLONED;
> +
> + /* Clone the bio. The block layer may modify the bvec array. */
> + clone = verity_bio_clone(io);
> + if (unlikely(!clone)) {
> + io->error = -ENOMEM;
> + return;
> + }
> +
> + verity_inc_pending(io);
> +
> + generic_make_request(clone);
> +}
> +
> +/* kverityd_io services the I/O workqueue. For each pass through
> + * the I/O workqueue, a call to populate both the origin drive
> + * data and the hash tree data is made.
> + */
> +static void kverityd_io(struct work_struct *work)
> +{
> + struct delayed_work *dwork = container_of(work, struct delayed_work,
> + work);
> + struct dm_verity_io *io = container_of(dwork, struct dm_verity_io,
> + work);
> +
> + /* Issue requests asynchronously. */
> + verity_inc_pending(io);
> + kverityd_src_io_read(io);
> + kverityd_io_bht_populate(io);
> + verity_dec_pending(io);
> +}
> +
> +/* Paired with verity_dec_pending, the pending value in the io dictate the
> + * lifetime of a request and when it is ready to be processed on the
> + * workqueues.
> + */
> +static void verity_inc_pending(struct dm_verity_io *io)
> +{
> + atomic_inc(&io->pending);
> +}
> +
> +/* Block-level requests start here. */
> +static int verity_map(struct dm_target *ti, struct bio *bio,
> + union map_info *map_context)
> +{
> + struct dm_verity_io *io;
> + struct verity_config *vc;
> + struct request_queue *r_queue;
> +
> + if (unlikely(!ti)) {
> + DMERR("dm_target was NULL");
> + return -EIO;
> + }
> +
> + vc = ti->private;
> + r_queue = bdev_get_queue(vc->dev->bdev);
> +
> + if (bio_data_dir(bio) == WRITE) {
> + /* If we silently drop writes, then the VFS layer will cache
> + * the write and persist it in memory. While it doesn't change
> + * the underlying storage, it still may be contrary to the
> + * behavior expected by a verified, read-only device.
> + */
> + DMWARN_LIMIT("write request received. rejecting with -EIO.");
> + verity_error(vc, NULL, -EIO);
> + return -EIO;
> + } else {
> + /* Queue up the request to be verified */
> + io = verity_io_alloc(ti, bio);
> + if (!io) {
> + DMERR_LIMIT("Failed to allocate and init IO data");
> + return DM_MAPIO_REQUEUE;
> + }
> + INIT_DELAYED_WORK(&io->work, kverityd_io);
> + queue_delayed_work(kverityd_ioq, &io->work, 0);
> + }
> +
> + return DM_MAPIO_SUBMITTED;
> +}
> +
> +static void splitarg(char *arg, char **key, char **val)
> +{
> + *key = strsep(&arg, "=");
> + *val = strsep(&arg, "");
> +}
> +
> +/*
> + * Non-block interfaces and device-mapper specific code
> + */
> +
> +/**
> + * verity_ctr - Construct a verified mapping
> + * @ti: Target being created
> + * @argc: Number of elements in argv
> + * @argv: Vector of key-value pairs (see below).
> + *
> + * Accepts the following keys:
> + * @payload: hashed device
> + * @hashtree: device hashtree is stored on
> + * @hashstart: start address of hashes (default 0)
> + * @block_size: size of a hash block
> + * @alg: hash algorithm
> + * @root_hexdigest: toplevel hash of the tree
> + * @error_behavior: what to do when verification fails [optional]
> + * @salt: salt, in hex [optional]
> + *
> + * E.g.,
> + * payload=/dev/sda2 hashtree=/dev/sda3 alg=sha256
> + * root_hexdigest=f08aa4a3695290c569eb1b0ac032ae1040150afb527abbeb0a3da33d82fb2c6e
> + *
> + * TODO(wad):
> + * - Boot time addition
> + * - Track block verification to free block_hashes if memory use is a concern
> + * Testing needed:
> + * - Regular slub_debug tracing (on checkins)
> + * - Improper block hash padding
> + * - Improper bundle padding
> + * - Improper hash layout
> + * - Missing padding at end of device
> + * - Improperly sized underlying devices
> + * - Out of memory conditions (make sure this isn't too flaky under high load!)
> + * - Incorrect superhash
> + * - Incorrect block hashes
> + * - Incorrect bundle hashes
> + * - Boot-up read speed; sustained read speeds
> + */
> +static int verity_ctr(struct dm_target *ti, unsigned int argc, char **argv)
> +{
> + struct verity_config *vc = NULL;
> + int ret = 0;
> + sector_t blocks;
> + unsigned int block_size = VERITY_DEFAULT_BLOCK_SIZE;
> + const char *payload = NULL;
> + const char *hashtree = NULL;
> + unsigned long hashstart = 0;
> + const char *alg = NULL;
> + const char *root_hexdigest = NULL;
> + const char *dev_error_behavior = error_behavior;
> + const char *hexsalt = "";
> + int i;
> +
> + for (i = 0; i < argc; ++i) {
> + char *key, *val;
> + DMWARN("Argument %d: '%s'", i, argv[i]);
> + splitarg(argv[i], &key, &val);
> + if (!key) {
> + DMWARN("Bad argument %d: missing key?", i);
> + break;
> + }
> + if (!val) {
> + DMWARN("Bad argument %d='%s': missing value", i, key);
> + break;
> + }
> +
> + if (!strcmp(key, "alg")) {
> + alg = val;
> + } else if (!strcmp(key, "payload")) {
> + payload = val;
> + } else if (!strcmp(key, "hashtree")) {
> + hashtree = val;
> + } else if (!strcmp(key, "root_hexdigest")) {
> + root_hexdigest = val;
> + } else if (!strcmp(key, "hashstart")) {
> + if (strict_strtoul(val, 10, &hashstart)) {
> + ti->error = "Invalid hashstart";
> + return -EINVAL;
> + }
> + } else if (!strcmp(key, "block_size")) {
> + unsigned long tmp;
> + if (strict_strtoul(val, 10, &tmp) ||
> + (tmp > UINT_MAX)) {
> + ti->error = "Invalid block_size";
> + return -EINVAL;
> + }
> + block_size = (unsigned int)tmp;
> + } else if (!strcmp(key, "error_behavior")) {
> + dev_error_behavior = val;
> + } else if (!strcmp(key, "salt")) {
> + hexsalt = val;
> + } else if (!strcmp(key, "error_behavior")) {
> + dev_error_behavior = val;
> + }
> + }
> +
> +#define NEEDARG(n) \
> + if (!(n)) { \
> + ti->error = "Missing argument: " #n; \
> + return -EINVAL; \
> + }
> +
> + NEEDARG(alg);
> + NEEDARG(payload);
> + NEEDARG(hashtree);
> + NEEDARG(root_hexdigest);
> +
> +#undef NEEDARG
> +
> + /* The device mapper device should be setup read-only */
> + if ((dm_table_get_mode(ti->table) & ~FMODE_READ) != 0) {
> + ti->error = "Must be created readonly.";
> + return -EINVAL;
> + }
> +
> + vc = kzalloc(sizeof(*vc), GFP_KERNEL);
> + if (!vc) {
> + /* TODO(wad) if this is called from the setup helper, then we
> + * catch these errors and do a CrOS specific thing. if not, we
> + * need to have this call the error handler.
> + */
> + return -EINVAL;
> + }
> +
> + /* Calculate the blocks from the given device size */
> + vc->size = ti->len;
> + blocks = to_bytes(vc->size) / block_size;
> + if (dm_bht_create(&vc->bht, blocks, block_size, alg)) {
> + DMERR("failed to create required bht");
> + goto bad_bht;
> + }
> + if (dm_bht_set_root_hexdigest(&vc->bht, root_hexdigest)) {
> + DMERR("root hexdigest error");
> + goto bad_root_hexdigest;
> + }
> + dm_bht_set_salt(&vc->bht, hexsalt);
> + vc->bht.read_cb = kverityd_bht_read_callback;
> +
> + /* payload: device to verify */
> + vc->start = 0; /* TODO: should this support a starting offset? */
> + /* We only ever grab the device in read-only mode. */
> + ret = dm_get_device(ti, payload,
> + dm_table_get_mode(ti->table), &vc->dev);
> + if (ret) {
> + DMERR("Failed to acquire device '%s': %d", payload, ret);
> + ti->error = "Device lookup failed";
> + goto bad_verity_dev;
> + }
> +
> + if ((to_bytes(vc->start) % block_size) ||
> + (to_bytes(vc->size) % block_size)) {
> + ti->error = "Device must be block_size divisble/aligned";
> + goto bad_hash_start;
> + }
> +
> + vc->hash_start = (sector_t)hashstart;
> +
> + /* hashtree: device with hashes.
> + * Note, payload == hashtree is okay as long as the size of
> + * ti->len passed to device mapper does not include
> + * the hashes.
> + */
> + if (dm_get_device(ti, hashtree,
> + dm_table_get_mode(ti->table), &vc->hash_dev)) {
> + ti->error = "Hash device lookup failed";
> + goto bad_hash_dev;
> + }
> +
> + /* arg4: cryptographic digest algorithm */
> + if (snprintf(vc->hash_alg, CRYPTO_MAX_ALG_NAME, "%s", alg) >=
> + CRYPTO_MAX_ALG_NAME) {
> + ti->error = "Hash algorithm name is too long";
> + goto bad_hash;
> + }
> +
> + /* override with optional device-specific error behavior */
> + vc->error_behavior = verity_parse_error_behavior(dev_error_behavior);
> + if (vc->error_behavior == -1) {
> + ti->error = "Bad error_behavior supplied";
> + goto bad_err_behavior;
> + }
> +
> + /* TODO: Maybe issues a request on the io queue for block 0? */
> +
> + /* Argument processing is done, setup operational data */
> + /* Pool for dm_verity_io objects */
> + vc->io_pool = mempool_create_slab_pool(MIN_IOS, _verity_io_pool);
> + if (!vc->io_pool) {
> + ti->error = "Cannot allocate verity io mempool";
> + goto bad_slab_pool;
> + }
> +
> + /* Allocate the bioset used for request padding */
> + /* TODO(wad) allocate a separate bioset for the first verify maybe */
> + vc->bs = bioset_create(MIN_BIOS, 0);
> + if (!vc->bs) {
> + ti->error = "Cannot allocate verity bioset";
> + goto bad_bs;
> + }
> +
> + ti->num_flush_requests = 1;
> + ti->private = vc;
> +
> + /* TODO(wad) add device and hash device names */
> + {
> + char hashdev[BDEVNAME_SIZE], vdev[BDEVNAME_SIZE];
> + bdevname(vc->hash_dev->bdev, hashdev);
> + bdevname(vc->dev->bdev, vdev);
> + DMINFO("dev:%s hash:%s [sectors:%llu blocks:%llu]", vdev,
> + hashdev, ULL(vc->bht.sectors), ULL(blocks));
> + }
> + return 0;
> +
> +bad_bs:
> + mempool_destroy(vc->io_pool);
> +bad_slab_pool:
> +bad_err_behavior:
> +bad_hash:
> + dm_put_device(ti, vc->hash_dev);
> +bad_hash_dev:
> +bad_hash_start:
> + dm_put_device(ti, vc->dev);
> +bad_bht:
> +bad_root_hexdigest:
> +bad_verity_dev:
> + kfree(vc); /* hash is not secret so no need to zero */
> + return -EINVAL;
> +}
> +
> +static void verity_dtr(struct dm_target *ti)
> +{
> + struct verity_config *vc = (struct verity_config *) ti->private;
> +
> + bioset_free(vc->bs);
> + mempool_destroy(vc->io_pool);
> + dm_bht_destroy(&vc->bht);
> + dm_put_device(ti, vc->hash_dev);
> + dm_put_device(ti, vc->dev);
> + kfree(vc);
> +}
> +
> +static int verity_status(struct dm_target *ti, status_type_t type,
> + char *result, unsigned int maxlen)
> +{
> + struct verity_config *vc = (struct verity_config *) ti->private;
> + unsigned int sz = 0;
> + char hashdev[BDEVNAME_SIZE], vdev[BDEVNAME_SIZE];
> + u8 hexdigest[VERITY_MAX_DIGEST_SIZE * 2 + 1] = { 0 };
> +
> + dm_bht_root_hexdigest(&vc->bht, hexdigest, sizeof(hexdigest));
> +
> + switch (type) {
> + case STATUSTYPE_INFO:
> + break;
> + case STATUSTYPE_TABLE:
> + bdevname(vc->hash_dev->bdev, hashdev);
> + bdevname(vc->dev->bdev, vdev);
> + DMEMIT("/dev/%s /dev/%s %llu %u %s %s",
> + vdev,
> + hashdev,
> + ULL(vc->hash_start),
> + vc->bht.depth,
> + vc->hash_alg,
> + hexdigest);
> + break;
> + }
> + return 0;
> +}
> +
> +static int verity_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
> + struct bio_vec *biovec, int max_size)
> +{
> + struct verity_config *vc = ti->private;
> + struct request_queue *q = bdev_get_queue(vc->dev->bdev);
> +
> + if (!q->merge_bvec_fn)
> + return max_size;
> +
> + bvm->bi_bdev = vc->dev->bdev;
> + bvm->bi_sector = vc->start + bvm->bi_sector - ti->begin;
> +
> + /* Optionally, this could just return 0 to stick to single pages. */
> + 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 verity_config *vc = ti->private;
> +
> + return fn(ti, vc->dev, vc->start, ti->len, data);
> +}
> +
> +static void verity_io_hints(struct dm_target *ti,
> + struct queue_limits *limits)
> +{
> + struct verity_config *vc = ti->private;
> + unsigned int block_size = vc->bht.block_size;
> +
> + limits->logical_block_size = block_size;
> + limits->physical_block_size = block_size;
> + blk_limits_io_min(limits, block_size);
> +}
> +
> +static struct target_type verity_target = {
> + .name = "verity",
> + .version = {0, 1, 0},
> + .module = THIS_MODULE,
> + .ctr = verity_ctr,
> + .dtr = verity_dtr,
> + .map = verity_map,
> + .merge = verity_merge,
> + .status = verity_status,
> + .iterate_devices = verity_iterate_devices,
> + .io_hints = verity_io_hints,
> +};
> +
> +#define VERITY_WQ_FLAGS (WQ_CPU_INTENSIVE|WQ_HIGHPRI)
> +
> +static int __init dm_verity_init(void)
> +{
> + int r = -ENOMEM;
> +
> + _verity_io_pool = KMEM_CACHE(dm_verity_io, 0);
> + if (!_verity_io_pool) {
> + DMERR("failed to allocate pool dm_verity_io");
> + goto bad_io_pool;
> + }
> +
> + kverityd_ioq = alloc_workqueue("kverityd_io", VERITY_WQ_FLAGS, 1);
> + if (!kverityd_ioq) {
> + DMERR("failed to create workqueue kverityd_ioq");
> + goto bad_io_queue;
> + }
> +
> + kveritydq = alloc_workqueue("kverityd", VERITY_WQ_FLAGS, 1);
> + if (!kveritydq) {
> + DMERR("failed to create workqueue kveritydq");
> + goto bad_verify_queue;
> + }
> +
> + r = dm_register_target(&verity_target);
> + if (r < 0) {
> + DMERR("register failed %d", r);
> + goto register_failed;
> + }
> +
> + DMINFO("version %u.%u.%u loaded", verity_target.version[0],
> + verity_target.version[1], verity_target.version[2]);
> +
> + return r;
> +
> +register_failed:
> + destroy_workqueue(kveritydq);
> +bad_verify_queue:
> + destroy_workqueue(kverityd_ioq);
> +bad_io_queue:
> + kmem_cache_destroy(_verity_io_pool);
> +bad_io_pool:
> + return r;
> +}
> +
> +static void __exit dm_verity_exit(void)
> +{
> + destroy_workqueue(kveritydq);
> + destroy_workqueue(kverityd_ioq);
> +
> + dm_unregister_target(&verity_target);
> + kmem_cache_destroy(_verity_io_pool);
> +}
> +
> +module_init(dm_verity_init);
> +module_exit(dm_verity_exit);
> +
> +MODULE_AUTHOR("The Chromium OS Authors <chromium-os-dev@...omium.org>");
> +MODULE_DESCRIPTION(DM_NAME " target for transparent disk integrity checking");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h
> new file mode 100644
> index 0000000..e0664c9
> --- /dev/null
> +++ b/drivers/md/dm-verity.h
> @@ -0,0 +1,45 @@
> +/*
> + * Copyright (C) 2011 The Chromium OS Authors <chromium-os-dev@...omium.org>
> + * All Rights Reserved.
> + *
> + * This file is released under the GPLv2.
> + *
> + * Provide error types for use when creating a custom error handler.
> + * See Documentation/device-mapper/dm-verity.txt
> + */
> +#ifndef DM_VERITY_H
> +#define DM_VERITY_H
> +
> +#include <linux/notifier.h>
> +
> +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 {
> + DM_VERITY_ERROR_BEHAVIOR_EIO = 0,
> + DM_VERITY_ERROR_BEHAVIOR_PANIC,
> + DM_VERITY_ERROR_BEHAVIOR_NONE,
> + DM_VERITY_ERROR_BEHAVIOR_NOTIFY
> +};
> +
> +
> +int dm_verity_register_error_notifier(struct notifier_block *nb);
> +int dm_verity_unregister_error_notifier(struct notifier_block *nb);
> +
> +#endif /* DM_VERITY_H */
> diff --git a/include/linux/dm-bht.h b/include/linux/dm-bht.h
> new file mode 100644
> index 0000000..0595911
> --- /dev/null
> +++ b/include/linux/dm-bht.h
> @@ -0,0 +1,166 @@
> +/*
> + * Copyright (C) 2011 The Chromium OS Authors <chromium-os-dev@...omium.org>
> + *
> + * Device-Mapper block hash tree interface.
> + * See Documentation/device-mapper/dm-bht.txt for details.
> + *
> + * This file is released under the GPLv2.
> + */
> +#ifndef __LINUX_DM_BHT_H
> +#define __LINUX_DM_BHT_H
> +
> +#include <linux/compiler.h>
> +#include <linux/crypto.h>
> +#include <linux/types.h>
> +
> +/* To avoid allocating memory for digest tests, we just setup a
> + * max to use for now.
> + */
> +#define DM_BHT_MAX_DIGEST_SIZE 128 /* 1k hashes are unlikely for now */
> +#define DM_BHT_SALT_SIZE 32 /* 256 bits of salt is a lot */
> +
> +/* UNALLOCATED, PENDING, READY, and VERIFIED are valid states. All other
> + * values are entry-related return codes.
> + */
> +#define DM_BHT_ENTRY_VERIFIED 8 /* 'nodes' has been checked against parent */
> +#define DM_BHT_ENTRY_READY 4 /* 'nodes' is loaded and available */
> +#define DM_BHT_ENTRY_PENDING 2 /* 'nodes' is being loaded */
> +#define DM_BHT_ENTRY_UNALLOCATED 0 /* untouched */
> +#define DM_BHT_ENTRY_ERROR -1 /* entry is unsuitable for use */
> +#define DM_BHT_ENTRY_ERROR_IO -2 /* I/O error on load */
> +
> +/* Additional possible return codes */
> +#define DM_BHT_ENTRY_ERROR_MISMATCH -3 /* Digest mismatch */
> +
> +/* dm_bht_entry
> + * Contains dm_bht->node_count tree nodes at a given tree depth.
> + * state is used to transactionally assure that data is paged in
> + * from disk. Unless dm_bht kept running crypto contexts for each
> + * level, we need to load in the data for on-demand verification.
> + */
> +struct dm_bht_entry {
> + atomic_t state; /* see defines */
> + /* Keeping an extra pointer per entry wastes up to ~33k of
> + * memory if a 1m blocks are used (or 66 on 64-bit arch)
> + */
> + void *io_context; /* Reserve a pointer for use during io */
> + /* data should only be non-NULL if fully populated. */
> + void *nodes; /* The hash data used to verify the children.
> + * Guaranteed to be page-aligned.
> + */
> +};
> +
> +/* dm_bht_level
> + * Contains an array of entries which represent a page of hashes where
> + * each hash is a node in the tree at the given tree depth/level.
> + */
> +struct dm_bht_level {
> + struct dm_bht_entry *entries; /* array of entries of tree nodes */
> + unsigned int count; /* number of entries at this level */
> + sector_t sector; /* starting sector for this level */
> +};
> +
> +/* opaque context, start, databuf, sector_count */
> +typedef int(*dm_bht_callback)(void *, /* external context */
> + sector_t, /* start sector */
> + u8 *, /* destination page */
> + sector_t, /* num sectors */
> + struct dm_bht_entry *);
> +/* dm_bht - Device mapper block hash tree
> + * dm_bht provides a fixed interface for comparing data blocks
> + * against a cryptographic hashes stored in a hash tree. It
> + * optimizes the tree structure for storage on disk.
> + *
> + * The tree is built from the bottom up. A collection of data,
> + * external to the tree, is hashed and these hashes are stored
> + * as the blocks in the tree. For some number of these hashes,
> + * a parent node is created by hashing them. These steps are
> + * repeated.
> + *
> + * TODO(wad): All hash storage memory is pre-allocated and freed once an
> + * entire branch has been verified.
> + */
> +struct dm_bht {
> + /* Configured values */
> + int depth; /* Depth of the tree including the root */
> + unsigned int block_count; /* Number of blocks hashed */
> + unsigned int block_size; /* Size of a hash block */
> + char hash_alg[CRYPTO_MAX_ALG_NAME];
> + unsigned char salt[DM_BHT_SALT_SIZE];
> +
> + /* Computed values */
> + unsigned int node_count; /* Data size (in hashes) for each entry */
> + unsigned int node_count_shift; /* first bit set - 1 */
> + /* There is one per CPU so that verified can be simultaneous. */
> + struct hash_desc hash_desc[NR_CPUS]; /* Container for the hash alg */
> + unsigned int digest_size;
> + sector_t sectors; /* Number of disk sectors used */
> +
> + /* bool verified; Full tree is verified */
> + u8 root_digest[DM_BHT_MAX_DIGEST_SIZE];
> + struct dm_bht_level *levels; /* in reverse order */
> + /* Callback for reading from the hash device */
> + dm_bht_callback read_cb;
> +};
> +
> +/* Constructor for struct dm_bht instances. */
> +int dm_bht_create(struct dm_bht *bht,
> + unsigned int block_count,
> + unsigned int block_size,
> + const char *alg_name);
> +/* Destructor for struct dm_bht instances. Does not free @bht */
> +void dm_bht_destroy(struct dm_bht *bht);
> +
> +/* Basic accessors for struct dm_bht */
> +int dm_bht_set_root_hexdigest(struct dm_bht *bht, const u8 *hexdigest);
> +int dm_bht_root_hexdigest(struct dm_bht *bht, u8 *hexdigest, int available);
> +void dm_bht_set_salt(struct dm_bht *bht, const char *hexsalt);
> +int dm_bht_salt(struct dm_bht *bht, char *hexsalt);
> +
> +/* Functions for loading in data from disk for verification */
> +bool dm_bht_is_populated(struct dm_bht *bht, unsigned int block);
> +int dm_bht_populate(struct dm_bht *bht, void *read_cb_ctx,
> + unsigned int block);
> +int dm_bht_verify_block(struct dm_bht *bht, unsigned int block,
> + struct page *pg, unsigned int offset);
> +void dm_bht_read_completed(struct dm_bht_entry *entry, int status);
> +
> +/* Functions for converting indices to nodes. */
> +
> +static inline unsigned int dm_bht_get_level_shift(struct dm_bht *bht,
> + int depth)
> +{
> + return (bht->depth - depth) * bht->node_count_shift;
> +}
> +
> +/* For the given depth, this is the entry index. At depth+1 it is the node
> + * index for depth.
> + */
> +static inline unsigned int dm_bht_index_at_level(struct dm_bht *bht,
> + int depth,
> + unsigned int leaf)
> +{
> + return leaf >> dm_bht_get_level_shift(bht, depth);
> +}
> +
> +static inline struct dm_bht_entry *dm_bht_get_entry(struct dm_bht *bht,
> + int depth,
> + unsigned int block)
> +{
> + unsigned int index = dm_bht_index_at_level(bht, depth, block);
> + struct dm_bht_level *level = &bht->levels[depth];
> +
> + return &level->entries[index];
> +}
> +
> +static inline void *dm_bht_get_node(struct dm_bht *bht,
> + struct dm_bht_entry *entry,
> + int depth,
> + unsigned int block)
> +{
> + unsigned int index = dm_bht_index_at_level(bht, depth, block);
> + unsigned int node_index = index % bht->node_count;
> +
> + return entry->nodes + (node_index * bht->digest_size);
> +}
> +#endif /* __LINUX_DM_BHT_H */
> --
> 1.7.3.1
>
>
--
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