Re: [PATCH v3] crypto: algapi - make crypto_xor() and crypto_inc() alignment agnostic

[Herbert Xu <herbert@gondor.apana.org.au>]

On Sun, Feb 05, 2017 at 10:06:12AM +0000, Ard Biesheuvel wrote:
> 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>

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
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