/*
 * Accelerated GHASH implementation with ARMv8 PMULL instructions.
 *
 * Copyright (C) 2014 Linaro Ltd. <ard.biesheuvel@linaro.org>
 *
 * 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 <asm/neon.h>
#include <asm/unaligned.h>
#include <crypto/internal/hash.h>
#include <linux/cpufeature.h>
#include <linux/crypto.h>
#include <linux/module.h>

MODULE_DESCRIPTION("GHASH secure hash using ARMv8 Crypto Extensions");
MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
MODULE_LICENSE("GPL v2");

#define GHASH_BLOCK_SIZE	16
#define GHASH_DIGEST_SIZE	16

struct ghash_key {
	u64 a;
	u64 b;
};

struct ghash_desc_ctx {
	u64 digest[GHASH_DIGEST_SIZE/sizeof(u64)];
	u8 buf[GHASH_BLOCK_SIZE];
	u32 count;
};

asmlinkage void pmull_ghash_update(int blocks, u64 dg[], const char *src,
				   struct ghash_key const *k, const char *head);

static int ghash_init(struct shash_desc *desc)
{
	struct ghash_desc_ctx *ctx = shash_desc_ctx(desc);

	*ctx = (struct ghash_desc_ctx){};
	return 0;
}

static int ghash_update(struct shash_desc *desc, const u8 *src,
			unsigned int len)
{
	struct ghash_desc_ctx *ctx = shash_desc_ctx(desc);
	unsigned int partial = ctx->count % GHASH_BLOCK_SIZE;

	ctx->count += len;

	if ((partial + len) >= GHASH_BLOCK_SIZE) {
		struct ghash_key *key = crypto_shash_ctx(desc->tfm);
		int blocks;

		if (partial) {
			int p = GHASH_BLOCK_SIZE - partial;

			memcpy(ctx->buf + partial, src, p);
			src += p;
			len -= p;
		}

		blocks = len / GHASH_BLOCK_SIZE;
		len %= GHASH_BLOCK_SIZE;

		kernel_neon_begin(8);
		pmull_ghash_update(blocks, ctx->digest, src, key,
				   partial ? ctx->buf : NULL);
		kernel_neon_end();
		src += blocks * GHASH_BLOCK_SIZE;
		partial = 0;
	}
	if (len)
		memcpy(ctx->buf + partial, src, len);
	return 0;
}

static int ghash_final(struct shash_desc *desc, u8 *dst)
{
	struct ghash_desc_ctx *ctx = shash_desc_ctx(desc);
	unsigned int partial = ctx->count % GHASH_BLOCK_SIZE;

	if (partial) {
		struct ghash_key *key = crypto_shash_ctx(desc->tfm);

		memset(ctx->buf + partial, 0, GHASH_BLOCK_SIZE - partial);

		kernel_neon_begin(8);
		pmull_ghash_update(1, ctx->digest, ctx->buf, key, NULL);
		kernel_neon_end();
	}
	put_unaligned_be64(ctx->digest[1], dst);
	put_unaligned_be64(ctx->digest[0], dst + 8);

	*ctx = (struct ghash_desc_ctx){};
	return 0;
}

static int ghash_setkey(struct crypto_shash *tfm,
			const u8 *inkey, unsigned int keylen)
{
	struct ghash_key *key = crypto_shash_ctx(tfm);
	u64 a, b;

	if (keylen != GHASH_BLOCK_SIZE) {
		crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
		return -EINVAL;
	}

	/* perform multiplication by 'x' in GF(2^128) */
	b = get_unaligned_be64(inkey);
	a = get_unaligned_be64(inkey + 8);

	key->a = (a << 1) | (b >> 63);
	key->b = (b << 1) | (a >> 63);

	if (b >> 63)
		key->b ^= 0xc200000000000000UL;

	return 0;
}

static struct shash_alg ghash_alg = {
	.digestsize	= GHASH_DIGEST_SIZE,
	.init		= ghash_init,
	.update		= ghash_update,
	.final		= ghash_final,
	.setkey		= ghash_setkey,
	.descsize	= sizeof(struct ghash_desc_ctx),
	.base		= {
		.cra_name		= "ghash",
		.cra_driver_name	= "ghash-ce",
		.cra_priority		= 200,
		.cra_flags		= CRYPTO_ALG_TYPE_SHASH,
		.cra_blocksize		= GHASH_BLOCK_SIZE,
		.cra_ctxsize		= sizeof(struct ghash_key),
		.cra_module		= THIS_MODULE,
	},
};

static int __init ghash_ce_mod_init(void)
{
	return crypto_register_shash(&ghash_alg);
}

static void __exit ghash_ce_mod_exit(void)
{
	crypto_unregister_shash(&ghash_alg);
}

module_cpu_feature_match(PMULL, ghash_ce_mod_init);
module_exit(ghash_ce_mod_exit);