crypto: algapi - make crypto_xor() and crypto_inc() alignment agnostic

Instead of unconditionally forcing 4 byte alignment for all generic
chaining modes that rely on crypto_xor() or crypto_inc() (which may
result in unnecessary copying of data when the underlying hardware
can perform unaligned accesses efficiently), make those functions
deal with unaligned input explicitly, but only if the Kconfig symbol
HAVE_EFFICIENT_UNALIGNED_ACCESS is set. This will allow us to drop
the alignmasks from the CBC, CMAC, CTR, CTS, PCBC and SEQIV drivers.

For crypto_inc(), this simply involves making the 4-byte stride
conditional on HAVE_EFFICIENT_UNALIGNED_ACCESS being set, given that
it typically operates on 16 byte buffers.

For crypto_xor(), an algorithm is implemented that simply runs through
the input using the largest strides possible if unaligned accesses are
allowed. If they are not, an optimal sequence of memory accesses is
emitted that takes the relative alignment of the input buffers into
account, e.g., if the relative misalignment of dst and src is 4 bytes,
the entire xor operation will be completed using 4 byte loads and stores
(modulo unaligned bits at the start and end). Note that all expressions
involving misalign are simply eliminated by the compiler when
HAVE_EFFICIENT_UNALIGNED_ACCESS is defined.

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

1 files changed, 0 insertions, 3 deletions

diff --git a/crypto/cbc.c b/crypto/cbc.c
index 68f751a41a84..bc160a3186dc 100644
--- a/crypto/cbc.c
+++ b/crypto/cbc.c
@@ -145,9 +145,6 @@ static int crypto_cbc_create(struct crypto_template *tmpl, struct rtattr **tb)
 	inst->alg.base.cra_blocksize = alg->cra_blocksize;
 	inst->alg.base.cra_alignmask = alg->cra_alignmask;
 
-	/* We access the data as u32s when xoring. */
-	inst->alg.base.cra_alignmask |= __alignof__(u32) - 1;
-
 	inst->alg.ivsize = alg->cra_blocksize;
 	inst->alg.min_keysize = alg->cra_cipher.cia_min_keysize;
 	inst->alg.max_keysize = alg->cra_cipher.cia_max_keysize;