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>

2 files changed, 5 insertions, 10 deletions

diff --git a/crypto/ctr.c b/crypto/ctr.c
index 477d922..854d924 100644
--- a/crypto/ctr.c
+++ b/crypto/ctr.c
@@ -65,8 +65,7 @@ static void crypto_ctr_crypt_final(struct blkcipher_walk *walk,
 	unsigned int nbytes = walk->nbytes;
 
 	crypto_cipher_encrypt_one(tfm, keystream, ctrblk);
-	crypto_xor(keystream, src, nbytes);
-	memcpy(dst, keystream, nbytes);
+	crypto_xor_cpy(dst, keystream, src, nbytes);
 
 	crypto_inc(ctrblk, bsize);
 }
diff --git a/crypto/pcbc.c b/crypto/pcbc.c
index 29dd2b4..d9e45a9 100644
--- a/crypto/pcbc.c
+++ b/crypto/pcbc.c
@@ -55,8 +55,7 @@ static int crypto_pcbc_encrypt_segment(struct skcipher_request *req,
 	do {
 		crypto_xor(iv, src, bsize);
 		crypto_cipher_encrypt_one(tfm, dst, iv);
-		memcpy(iv, dst, bsize);
-		crypto_xor(iv, src, bsize);
+		crypto_xor_cpy(iv, dst, src, bsize);
 
 		src += bsize;
 		dst += bsize;
@@ -79,8 +78,7 @@ static int crypto_pcbc_encrypt_inplace(struct skcipher_request *req,
 		memcpy(tmpbuf, src, bsize);
 		crypto_xor(iv, src, bsize);
 		crypto_cipher_encrypt_one(tfm, src, iv);
-		memcpy(iv, tmpbuf, bsize);
-		crypto_xor(iv, src, bsize);
+		crypto_xor_cpy(iv, tmpbuf, src, bsize);
 
 		src += bsize;
 	} while ((nbytes -= bsize) >= bsize);
@@ -127,8 +125,7 @@ static int crypto_pcbc_decrypt_segment(struct skcipher_request *req,
 	do {
 		crypto_cipher_decrypt_one(tfm, dst, src);
 		crypto_xor(dst, iv, bsize);
-		memcpy(iv, src, bsize);
-		crypto_xor(iv, dst, bsize);
+		crypto_xor_cpy(iv, dst, src, bsize);
 
 		src += bsize;
 		dst += bsize;
@@ -153,8 +150,7 @@ static int crypto_pcbc_decrypt_inplace(struct skcipher_request *req,
 		memcpy(tmpbuf, src, bsize);
 		crypto_cipher_decrypt_one(tfm, src, src);
 		crypto_xor(src, iv, bsize);
-		memcpy(iv, tmpbuf, bsize);
-		crypto_xor(iv, src, bsize);
+		crypto_xor_cpy(iv, src, tmpbuf, bsize);
 
 		src += bsize;
 	} while ((nbytes -= bsize) >= bsize);