• Ard Biesheuvel's avatar
    crypto: algapi - make crypto_xor() and crypto_inc() alignment agnostic · db91af0f
    Ard Biesheuvel authored
    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: 's avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
    Signed-off-by: 's avatarHerbert Xu <herbert@gondor.apana.org.au>
    db91af0f