Hi.
     I've build (gentoo) cryptsetup with support of kernel level 
encryption (instead of openssl/gcrypt etc...). The kernel configuration 
(custom kernel) is attached.

Cryptsetup complaints 'Cannot initialize crypto backend'

dm-crypt is present, aes modules are loaded, urandom is there.

lsmod
Module                  Size  Used by
algif_skcipher          4984  0
ablk_helper             1336  0
cryptd                  4864  1 ablk_helper
xts                     2296  0
gf128mul                4664  1 xts
ecb                     1336  0
cbc                     2040  0
aes_x86_64              6904  0
crypto_null             2040  0
algif_hash              2552  0
af_alg                  3712  2 algif_hash,algif_skcipher
loop                   15048  1
dm_crypt               13696  0
dm_mod                 61312  1 dm_crypt
sr_mod                 12548  0
cdrom                  23039  1 sr_mod
desktopminer linux-3.17.1-gentoo # cryptsetup --debug -c aes-cbc-null 
--key-size 256 create burn /dev/loop0
# cryptsetup 1.6.5 processing "cryptsetup --debug -c aes-cbc-null 
--key-size 256 create burn /dev/loop0"
# Running command open.
# Locking memory.
# Installing SIGINT/SIGTERM handler.
# Unblocking interruption on signal.
# Allocating crypt device /dev/loop0 context.
# Trying to open and read device /dev/loop0.
# Initialising device-mapper backend library.
# Timeout set to 0 miliseconds.
# Password retry count set to 3.
# Formatting device /dev/loop0 as type PLAIN.
Cannot initialize crypto backend.
# Crypto backend () initialized.
# Releasing crypt device /dev/loop0 context.
# Releasing device-mapper backend.
# Unlocking memory.
Command failed with code 22: Cannot initialize crypto backend.

Thanks for any help!