crypto: xts: add interface for parallelized cipher implementations

Add xts_crypt() function that can be used by cipher implementations that can
benefit from parallelized cipher operations.

Signed-off-by: Jussi Kivilinna <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>

crypto/xts.c

···
 #include <linux/scatterlist.h>
 #include <linux/slab.h>
 
+#include <crypto/xts.h>
 #include <crypto/b128ops.h>
 #include <crypto/gf128mul.h>
-
-#define XTS_BLOCK_SIZE 16
 
 struct priv {
 	struct crypto_cipher *child;
···
 	return crypt(desc, &w, ctx, crypto_cipher_alg(ctx->tweak)->cia_encrypt,
 		     crypto_cipher_alg(ctx->child)->cia_decrypt);
 }
+
+int xts_crypt(struct blkcipher_desc *desc, struct scatterlist *sdst,
+	      struct scatterlist *ssrc, unsigned int nbytes,
+	      struct xts_crypt_req *req)
+{
+	const unsigned int bsize = XTS_BLOCK_SIZE;
+	const unsigned int max_blks = req->tbuflen / bsize;
+	struct blkcipher_walk walk;
+	unsigned int nblocks;
+	be128 *src, *dst, *t;
+	be128 *t_buf = req->tbuf;
+	int err, i;
+
+	BUG_ON(max_blks < 1);
+
+	blkcipher_walk_init(&walk, sdst, ssrc, nbytes);
+
+	err = blkcipher_walk_virt(desc, &walk);
+	nbytes = walk.nbytes;
+	if (!nbytes)
+		return err;
+
+	nblocks = min(nbytes / bsize, max_blks);
+	src = (be128 *)walk.src.virt.addr;
+	dst = (be128 *)walk.dst.virt.addr;
+
+	/* calculate first value of T */
+	req->tweak_fn(req->tweak_ctx, (u8 *)&t_buf[0], walk.iv);
+
+	i = 0;
+	goto first;
+
+	for (;;) {
+		do {
+			for (i = 0; i < nblocks; i++) {
+				gf128mul_x_ble(&t_buf[i], t);
+first:
+				t = &t_buf[i];
+
+				/* PP <- T xor P */
+				be128_xor(dst + i, t, src + i);
+			}
+
+			/* CC <- E(Key2,PP) */
+			req->crypt_fn(req->crypt_ctx, (u8 *)dst,
+				      nblocks * bsize);
+
+			/* C <- T xor CC */
+			for (i = 0; i < nblocks; i++)
+				be128_xor(dst + i, dst + i, &t_buf[i]);
+
+			src += nblocks;
+			dst += nblocks;
+			nbytes -= nblocks * bsize;
+			nblocks = min(nbytes / bsize, max_blks);
+		} while (nblocks > 0);
+
+		*(be128 *)walk.iv = *t;
+
+		err = blkcipher_walk_done(desc, &walk, nbytes);
+		nbytes = walk.nbytes;
+		if (!nbytes)
+			break;
+
+		nblocks = min(nbytes / bsize, max_blks);
+		src = (be128 *)walk.src.virt.addr;
+		dst = (be128 *)walk.dst.virt.addr;
+	}
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(xts_crypt);
 
 static int init_tfm(struct crypto_tfm *tfm)
 {

include/crypto/xts.h

···
+#ifndef _CRYPTO_XTS_H
+#define _CRYPTO_XTS_H
+
+#include <crypto/b128ops.h>
+
+struct scatterlist;
+struct blkcipher_desc;
+
+#define XTS_BLOCK_SIZE 16
+
+struct xts_crypt_req {
+	be128 *tbuf;
+	unsigned int tbuflen;
+
+	void *tweak_ctx;
+	void (*tweak_fn)(void *ctx, u8* dst, const u8* src);
+	void *crypt_ctx;
+	void (*crypt_fn)(void *ctx, u8 *blks, unsigned int nbytes);
+};
+
+#define XTS_TWEAK_CAST(x) ((void (*)(void *, u8*, const u8*))(x))
+
+int xts_crypt(struct blkcipher_desc *desc, struct scatterlist *dst,
+	      struct scatterlist *src, unsigned int nbytes,
+	      struct xts_crypt_req *req);
+
+#endif  /* _CRYPTO_XTS_H */