Merge "defconfig: msm: Enable FEC feature for DM-VERITY"

    0 is the original format used in the Chromium OS.

      The salt is appended when hashing, digests are stored continuously and

      the rest of the block is padded with zeros.

      the rest of the block is padded with zeroes.

    1 is the current format that should be used for new devices.

      The salt is prepended when hashing and each digest is

      padded with zeros to the power of two.

      padded with zeroes to the power of two.

<dev>

    This is the device containing data, the integrity of which needs to be

      notify user space.

ignore_zero_blocks

    Do not verify blocks that are expected to contain zeroes and always return

    zeroes instead. This may be useful if the partition contains unused blocks

    that are not guaranteed to contain zeroes.

use_fec_from_device <fec_dev>

    Use forward error correction (FEC) to recover from corruption if hash

    verification fails. Use encoding data from the specified device. This

    may be the same device where data and hash blocks reside, in which case

    fec_start must be outside data and hash areas.

    If the encoding data covers additional metadata, it must be accessible

    on the hash device after the hash blocks.

    Note: block sizes for data and hash devices must match. Also, if the

    verity <dev> is encrypted the <fec_dev> should be too.

fec_roots <num>

    Number of generator roots. This equals to the number of parity bytes in

    the encoding data. For example, in RS(M, N) encoding, the number of roots

    is M-N.

fec_blocks <num>

    The number of encoding data blocks on the FEC device. The block size for

    the FEC device is <data_block_size>.

fec_start <offset>

    This is the offset, in <data_block_size> blocks, from the start of the

    FEC device to the beginning of the encoding data.

Theory of operation

===================

into the page cache. Block hashes are stored linearly, aligned to the nearest

block size.

If forward error correction (FEC) support is enabled any recovery of

corrupted data will be verified using the cryptographic hash of the

corresponding data. This is why combining error correction with

integrity checking is essential.

Hash Tree

---------

CONFIG_MD=y

CONFIG_BLK_DEV_DM=y

CONFIG_DM_VERITY=y

CONFIG_DM_VERITY_FEC=y

CONFIG_NETDEVICES=y

CONFIG_DUMMY=y

CONFIG_TUN=y

CONFIG_MD=y

CONFIG_BLK_DEV_DM=y

CONFIG_DM_VERITY=y

CONFIG_DM_VERITY_FEC=y

CONFIG_NETDEVICES=y

CONFIG_DUMMY=y

CONFIG_TUN=y

CONFIG_MD=y

CONFIG_BLK_DEV_DM=y

CONFIG_DM_VERITY=y

CONFIG_DM_VERITY_FEC=y

CONFIG_NETDEVICES=y

CONFIG_DUMMY=y

CONFIG_IFB=y

CONFIG_MD=y

CONFIG_BLK_DEV_DM=y

CONFIG_DM_VERITY=y

CONFIG_DM_VERITY_FEC=y

CONFIG_NETDEVICES=y

CONFIG_DUMMY=y

CONFIG_IFB=y