/* GPL HEADER START
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 only,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License version 2 for more details (a copy is included
 * in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this program; If not, see http://www.gnu.org/licenses
 *
 * Please  visit http://www.xyratex.com/contact if you need additional
 * information or have any questions.
 *
 * GPL HEADER END
 */

/*
 * Copyright 2012 Xyratex Technology Limited
 *
 * Wrappers for kernel crypto shash api to pclmulqdq crc32 imlementation.
 */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/crc32.h>
#include <crypto/internal/hash.h>

#include <asm/cpufeatures.h>
#include <asm/cpu_device_id.h>
#include <asm/fpu/api.h>

#define CHKSUM_BLOCK_SIZE	1
#define CHKSUM_DIGEST_SIZE	4

#define PCLMUL_MIN_LEN		64L     /* minimum size of buffer
					 * for crc32_pclmul_le_16 */
#define SCALE_F			16L	/* size of xmm register */
#define SCALE_F_MASK		(SCALE_F - 1)

u32 crc32_pclmul_le_16(unsigned char const *buffer, size_t len, u32 crc32);

static u32 __attribute__((pure))
	crc32_pclmul_le(u32 crc, unsigned char const *p, size_t len)
{
	unsigned int iquotient;
	unsigned int iremainder;
	unsigned int prealign;

	if (len < PCLMUL_MIN_LEN + SCALE_F_MASK || !irq_fpu_usable())
		return crc32_le(crc, p, len);

	if ((long)p & SCALE_F_MASK) {
		/* align p to 16 byte */
		prealign = SCALE_F - ((long)p & SCALE_F_MASK);

		crc = crc32_le(crc, p, prealign);
		len -= prealign;
		p = (unsigned char *)(((unsigned long)p + SCALE_F_MASK) &
				     ~SCALE_F_MASK);
	}
	iquotient = len & (~SCALE_F_MASK);
	iremainder = len & SCALE_F_MASK;

	kernel_fpu_begin();
	crc = crc32_pclmul_le_16(p, iquotient, crc);
	kernel_fpu_end();

	if (iremainder)
		crc = crc32_le(crc, p + iquotient, iremainder);

	return crc;
}

static int crc32_pclmul_cra_init(struct crypto_tfm *tfm)
{
	u32 *key = crypto_tfm_ctx(tfm);

	*key = 0;

	return 0;
}

static int crc32_pclmul_setkey(struct crypto_shash *hash, const u8 *key,
			unsigned int keylen)
{
	u32 *mctx = crypto_shash_ctx(hash);

	if (keylen != sizeof(u32)) {
		crypto_shash_set_flags(hash, CRYPTO_TFM_RES_BAD_KEY_LEN);
		return -EINVAL;
	}
	*mctx = le32_to_cpup((__le32 *)key);
	return 0;
}

static int crc32_pclmul_init(struct shash_desc *desc)
{
	u32 *mctx = crypto_shash_ctx(desc->tfm);
	u32 *crcp = shash_desc_ctx(desc);

	*crcp = *mctx;

	return 0;
}

static int crc32_pclmul_update(struct shash_desc *desc, const u8 *data,
			       unsigned int len)
{
	u32 *crcp = shash_desc_ctx(desc);

	*crcp = crc32_pclmul_le(*crcp, data, len);
	return 0;
}

/* No final XOR 0xFFFFFFFF, like crc32_le */
static int __crc32_pclmul_finup(u32 *crcp, const u8 *data, unsigned int len,
				u8 *out)
{
	*(__le32 *)out = cpu_to_le32(crc32_pclmul_le(*crcp, data, len));
	return 0;
}

static int crc32_pclmul_finup(struct shash_desc *desc, const u8 *data,
			      unsigned int len, u8 *out)
{
	return __crc32_pclmul_finup(shash_desc_ctx(desc), data, len, out);
}

static int crc32_pclmul_final(struct shash_desc *desc, u8 *out)
{
	u32 *crcp = shash_desc_ctx(desc);

	*(__le32 *)out = cpu_to_le32p(crcp);
	return 0;
}

static int crc32_pclmul_digest(struct shash_desc *desc, const u8 *data,
			       unsigned int len, u8 *out)
{
	return __crc32_pclmul_finup(crypto_shash_ctx(desc->tfm), data, len,
				    out);
}

static struct shash_alg alg = {
	.setkey		= crc32_pclmul_setkey,
	.init		= crc32_pclmul_init,
	.update		= crc32_pclmul_update,
	.final		= crc32_pclmul_final,
	.finup		= crc32_pclmul_finup,
	.digest		= crc32_pclmul_digest,
	.descsize	= sizeof(u32),
	.digestsize	= CHKSUM_DIGEST_SIZE,
	.base		= {
			.cra_name		= "crc32",
			.cra_driver_name	= "crc32-pclmul",
			.cra_priority		= 200,
			.cra_flags		= CRYPTO_ALG_OPTIONAL_KEY,
			.cra_blocksize		= CHKSUM_BLOCK_SIZE,
			.cra_ctxsize		= sizeof(u32),
			.cra_module		= THIS_MODULE,
			.cra_init		= crc32_pclmul_cra_init,
	}
};

static const struct x86_cpu_id crc32pclmul_cpu_id[] = {
	X86_FEATURE_MATCH(X86_FEATURE_PCLMULQDQ),
	{}
};
MODULE_DEVICE_TABLE(x86cpu, crc32pclmul_cpu_id);


static int __init crc32_pclmul_mod_init(void)
{

	if (!x86_match_cpu(crc32pclmul_cpu_id)) {
		pr_info("PCLMULQDQ-NI instructions are not detected.\n");
		return -ENODEV;
	}
	return crypto_register_shash(&alg);
}

static void __exit crc32_pclmul_mod_fini(void)
{
	crypto_unregister_shash(&alg);
}

module_init(crc32_pclmul_mod_init);
module_exit(crc32_pclmul_mod_fini);

MODULE_AUTHOR("Alexander Boyko <alexander_boyko@xyratex.com>");
MODULE_LICENSE("GPL");

MODULE_ALIAS_CRYPTO("crc32");
MODULE_ALIAS_CRYPTO("crc32-pclmul");