tree 1a103154cb5c0edd70c5fd50ba323abec1634662
parent f1b4d6b369fdd7d067a5a57f0b88fbf09f3d54a5
author Ard Biesheuvel <ard.biesheuvel@linaro.org> 1500892099 +0100
committer Eric Biggers <ebiggers@google.com> 1544722498 -0800

UPSTREAM: crypto: arm/aes - avoid expanded lookup tables in the final round

For the final round, avoid the expanded and padded lookup tables
exported by the generic AES driver. Instead, for encryption, we can
perform byte loads from the same table we used for the inner rounds,
which will still be hot in the caches. For decryption, use the inverse
AES Sbox directly, which is 4x smaller than the inverse lookup table
exported by the generic driver.

This should significantly reduce the Dcache footprint of our code,
which makes the code more robust against timing attacks. It does not
introduce any additional module dependencies, given that we already
rely on the core AES module for the shared key expansion routines.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

(cherry picked from commit 0d149ce67d4409d7ff13c2d08c3474f3319e1b7e)
Bug: 112008522
Test: As series, see Ic61c13b53facfd2173065be715a7ee5f3af8760b
Change-Id: I7014d89fae758633b7a7d63bd605e0197015b499
Signed-off-by: Eric Biggers <ebiggers@google.com>