crypto: algapi - make crypto_xor() take separate dst and src arguments

There are quite a number of occurrences in the kernel of the pattern

  if (dst != src)
          memcpy(dst, src, walk.total % AES_BLOCK_SIZE);
  crypto_xor(dst, final, walk.total % AES_BLOCK_SIZE);

or

  crypto_xor(keystream, src, nbytes);
  memcpy(dst, keystream, nbytes);

where crypto_xor() is preceded or followed by a memcpy() invocation
that is only there because crypto_xor() uses its output parameter as
one of the inputs. To avoid having to add new instances of this pattern
in the arm64 code, which will be refactored to implement non-SIMD
fallbacks, add an alternative implementation called crypto_xor_cpy(),
taking separate input and output arguments. This removes the need for
the separate memcpy().

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

1 files changed, 5 insertions, 6 deletions

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index cdf6b1e12460..fa17e5452796 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -758,9 +758,8 @@ static int crypt_iv_tcw_whitening(struct crypt_config *cc,
 	int i, r;
 
 	/* xor whitening with sector number */
-	memcpy(buf, tcw->whitening, TCW_WHITENING_SIZE);
-	crypto_xor(buf, (u8 *)&sector, 8);
-	crypto_xor(&buf[8], (u8 *)&sector, 8);
+	crypto_xor_cpy(buf, tcw->whitening, (u8 *)&sector, 8);
+	crypto_xor_cpy(&buf[8], tcw->whitening + 8, (u8 *)&sector, 8);
 
 	/* calculate crc32 for every 32bit part and xor it */
 	desc->tfm = tcw->crc32_tfm;
@@ -805,10 +804,10 @@ static int crypt_iv_tcw_gen(struct crypt_config *cc, u8 *iv,
 	}
 
 	/* Calculate IV */
-	memcpy(iv, tcw->iv_seed, cc->iv_size);
-	crypto_xor(iv, (u8 *)&sector, 8);
+	crypto_xor_cpy(iv, tcw->iv_seed, (u8 *)&sector, 8);
 	if (cc->iv_size > 8)
-		crypto_xor(&iv[8], (u8 *)&sector, cc->iv_size - 8);
+		crypto_xor_cpy(&iv[8], tcw->iv_seed + 8, (u8 *)&sector,
+			       cc->iv_size - 8);
 
 	return r;
 }