Re: [PATCH] crypto: crypto_xor - use helpers for unaligned accesses

From: Ard Biesheuvel <ardb@kernel.org>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
	Eric Biggers <ebiggers@kernel.org>
Subject: Re: [PATCH] crypto: crypto_xor - use helpers for unaligned accesses
Date: Wed, 23 Feb 2022 07:44:56 +0100	[thread overview]
Message-ID: <CAMj1kXGKtLagHZsZV2KMGNqp3Cn8V6c8CJvLhrFJ63ND33XNqQ@mail.gmail.com> (raw)
In-Reply-To: <YhWg246ql3Xa0MRR@gondor.apana.org.au>

On Wed, 23 Feb 2022 at 03:50, Herbert Xu <herbert@gondor.apana.org.au> wrote:
>
> On Tue, Feb 15, 2022 at 11:57:17AM +0100, Ard Biesheuvel wrote:
> > Dereferencing a misaligned pointer is undefined behavior in C, and may
> > result in codegen on architectures such as ARM that trigger alignments
> > traps and expensive fixups in software.
> >
> > Instead, use the get_aligned()/put_aligned() accessors, which are cheap
> > or even completely free when CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y.
> >
> > In the converse case, the prior alignment checks ensure that the casts
> > are safe, and so no unaligned accessors are necessary.
> >
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > ---
> >  crypto/algapi.c         | 24 +++++++++++++++++++++---
> >  include/crypto/algapi.h | 11 +++++++++--
> >  2 files changed, 30 insertions(+), 5 deletions(-)
>
> Ard, could you please take a look at the two kbuild reports and
> see if there is an issue that needs to be resolved?
>

My patch is flawed - I'll fix it and send a v2.