The non-bitsliced AES implementation using the NEON is highly sensitive
to micro-architectural details, and, as it turns out, the Cortex-A53 on
the Raspberry Pi 3 is a core that can benefit from this code, given that
its scalar AES performance is abysmal (32.9 cycles per byte).
The new bitsliced AES code manages 19.8 cycles per byte on this core,
but can only operate on 8 blocks at a time, which is not supported by
all chaining modes. With a bit of tweaking, we can get the plain NEON
code to run at 22.0 cycles per byte, making it useful for sequential
modes like CBC encryption. (Like bitsliced NEON, the plain NEON
implementation does not use any lookup tables, which makes it easy on
the D-cache, and invulnerable to cache timing attacks)
So tweak the plain NEON AES code to use tbl instructions rather than
shl/sri pairs, and to avoid the need to reload permutation vectors or
other constants from memory in every round. Also, improve the decryption
performance by switching to 16x8 pmul instructions for the performing
the multiplications in GF(2^8).
To allow the ECB and CBC encrypt routines to be reused by the bitsliced
NEON code in a subsequent patch, export them from the module.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The AES implementation using pure NEON instructions relies on the generic
AES key schedule generation routines, which store the round keys as arrays
of 32-bit quantities stored in memory using native endianness. This means
we should refer to these round keys using 4x4 loads rather than 16x1 loads.
In addition, the ShiftRows tables are loading using a single scalar load,
which is also affected by endianness, so emit these tables in the correct
order depending on whether we are building for big endian or not.
Fixes: 49788fe2a1 ("arm64/crypto: AES-ECB/CBC/CTR/XTS using ARMv8 NEON and Crypto Extensions")
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This adds ARMv8 implementations of AES in ECB, CBC, CTR and XTS modes,
both for ARMv8 with Crypto Extensions and for plain ARMv8 NEON.
The Crypto Extensions version can only run on ARMv8 implementations that
have support for these optional extensions.
The plain NEON version is a table based yet time invariant implementation.
All S-box substitutions are performed in parallel, leveraging the wide range
of ARMv8's tbl/tbx instructions, and the huge NEON register file, which can
comfortably hold the entire S-box and still have room to spare for doing the
actual computations.
The key expansion routines were borrowed from aes_generic.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
