[CRYPTO] Add alignmask for low-level cipher implementations

The VIA Padlock device requires the input and output buffers to
be aligned on 16-byte boundaries.  This patch adds the alignmask
attribute for low-level cipher implementations to indicate their
alignment requirements.

The mid-level crypt() function will copy the input/output buffers
if they are not aligned correctly before they are passed to the
low-level implementation.

Strictly speaking, some of the software implementations require
the buffers to be aligned on 4-byte boundaries as they do 32-bit
loads.  However, it is not clear whether it is better to copy
the buffers or pay the penalty for unaligned loads/stores.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 0 deletions

diff --git a/crypto/scatterwalk.h b/crypto/scatterwalk.h
index 5495bb9..e79925c 100644
--- a/crypto/scatterwalk.h
+++ b/crypto/scatterwalk.h
@@ -55,6 +55,12 @@ static inline void scatterwalk_advance(struct scatter_walk *walk,
 	walk->len_this_segment -= nbytes;
 }
 
+static inline unsigned int scatterwalk_aligned(struct scatter_walk *walk,
+					       unsigned int alignmask)
+{
+	return !(walk->offset & alignmask);
+}
+
 void scatterwalk_start(struct scatter_walk *walk, struct scatterlist *sg);
 int scatterwalk_copychunks(void *buf, struct scatter_walk *walk, size_t nbytes, int out);
 void scatterwalk_map(struct scatter_walk *walk, int out);