crypto: sha512 - implement base layer for SHA-512

To reduce the number of copies of boilerplate code throughout
the tree, this patch implements generic glue for the SHA-512
algorithm. This allows a specific arch or hardware implementation
to only implement the special handling that it needs.

The users need to supply an implementation of

void (sha512_block_fn)(struct sha512_state *sst, u8 const *src, int blocks)

and pass it to the SHA-512 base functions. For easy casting between the
prototype above and existing block functions that take a 'u64 state[]'
as their first argument, the 'state' member of struct sha512_state is
moved to the base of the struct.

Signed-off-by: Ard Biesheuvel <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>

include/crypto/sha.h

···
 };
 
 struct sha512_state {
-	u64 count[2];
 	u64 state[SHA512_DIGEST_SIZE / 8];
+	u64 count[2];
 	u8 buf[SHA512_BLOCK_SIZE];
 };
 

include/crypto/sha512_base.h

···
+/*
+ * sha512_base.h - core logic for SHA-512 implementations
+ *
+ * Copyright (C) 2015 Linaro Ltd <[e-mail]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <crypto/internal/hash.h>
+#include <crypto/sha.h>
+#include <linux/crypto.h>
+#include <linux/module.h>
+
+#include <asm/unaligned.h>
+
+typedef void (sha512_block_fn)(struct sha512_state *sst, u8 const *src,
+			       int blocks);
+
+static inline int sha384_base_init(struct shash_desc *desc)
+{
+	struct sha512_state *sctx = shash_desc_ctx(desc);
+
+	sctx->state[0] = SHA384_H0;
+	sctx->state[1] = SHA384_H1;
+	sctx->state[2] = SHA384_H2;
+	sctx->state[3] = SHA384_H3;
+	sctx->state[4] = SHA384_H4;
+	sctx->state[5] = SHA384_H5;
+	sctx->state[6] = SHA384_H6;
+	sctx->state[7] = SHA384_H7;
+	sctx->count[0] = sctx->count[1] = 0;
+
+	return 0;
+}
+
+static inline int sha512_base_init(struct shash_desc *desc)
+{
+	struct sha512_state *sctx = shash_desc_ctx(desc);
+
+	sctx->state[0] = SHA512_H0;
+	sctx->state[1] = SHA512_H1;
+	sctx->state[2] = SHA512_H2;
+	sctx->state[3] = SHA512_H3;
+	sctx->state[4] = SHA512_H4;
+	sctx->state[5] = SHA512_H5;
+	sctx->state[6] = SHA512_H6;
+	sctx->state[7] = SHA512_H7;
+	sctx->count[0] = sctx->count[1] = 0;
+
+	return 0;
+}
+
+static inline int sha512_base_do_update(struct shash_desc *desc,
+					const u8 *data,
+					unsigned int len,
+					sha512_block_fn *block_fn)
+{
+	struct sha512_state *sctx = shash_desc_ctx(desc);
+	unsigned int partial = sctx->count[0] % SHA512_BLOCK_SIZE;
+
+	sctx->count[0] += len;
+	if (sctx->count[0] < len)
+		sctx->count[1]++;
+
+	if (unlikely((partial + len) >= SHA512_BLOCK_SIZE)) {
+		int blocks;
+
+		if (partial) {
+			int p = SHA512_BLOCK_SIZE - partial;
+
+			memcpy(sctx->buf + partial, data, p);
+			data += p;
+			len -= p;
+
+			block_fn(sctx, sctx->buf, 1);
+		}
+
+		blocks = len / SHA512_BLOCK_SIZE;
+		len %= SHA512_BLOCK_SIZE;
+
+		if (blocks) {
+			block_fn(sctx, data, blocks);
+			data += blocks * SHA512_BLOCK_SIZE;
+		}
+		partial = 0;
+	}
+	if (len)
+		memcpy(sctx->buf + partial, data, len);
+
+	return 0;
+}
+
+static inline int sha512_base_do_finalize(struct shash_desc *desc,
+					  sha512_block_fn *block_fn)
+{
+	const int bit_offset = SHA512_BLOCK_SIZE - sizeof(__be64[2]);
+	struct sha512_state *sctx = shash_desc_ctx(desc);
+	__be64 *bits = (__be64 *)(sctx->buf + bit_offset);
+	unsigned int partial = sctx->count[0] % SHA512_BLOCK_SIZE;
+
+	sctx->buf[partial++] = 0x80;
+	if (partial > bit_offset) {
+		memset(sctx->buf + partial, 0x0, SHA512_BLOCK_SIZE - partial);
+		partial = 0;
+
+		block_fn(sctx, sctx->buf, 1);
+	}
+
+	memset(sctx->buf + partial, 0x0, bit_offset - partial);
+	bits[0] = cpu_to_be64(sctx->count[1] << 3 | sctx->count[0] >> 61);
+	bits[1] = cpu_to_be64(sctx->count[0] << 3);
+	block_fn(sctx, sctx->buf, 1);
+
+	return 0;
+}
+
+static inline int sha512_base_finish(struct shash_desc *desc, u8 *out)
+{
+	unsigned int digest_size = crypto_shash_digestsize(desc->tfm);
+	struct sha512_state *sctx = shash_desc_ctx(desc);
+	__be64 *digest = (__be64 *)out;
+	int i;
+
+	for (i = 0; digest_size > 0; i++, digest_size -= sizeof(__be64))
+		put_unaligned_be64(sctx->state[i], digest++);
+
+	*sctx = (struct sha512_state){};
+	return 0;
+}