/*
 * Using hardware provided CRC32 instruction to accelerate the CRC32 disposal.
 * CRC32C polynomial:0x1EDC6F41(BE)/0x82F63B78(LE)
 * CRC32 is a new instruction in Intel SSE4.2, the reference can be found at:
 * http://www.intel.com/products/processor/manuals/
 * Intel(R) 64 and IA-32 Architectures Software Developer's Manual
 * Volume 2A: Instruction Set Reference, A-M
 *
 * Copyright (C) 2008 Intel Corporation
 * Authors: Austin Zhang <austin_zhang@linux.intel.com>
 *          Kent Liu <kent.liu@intel.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope 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 for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
 *
 */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <crypto/internal/hash.h>

#include <asm/cpufeature.h>
#include <asm/cpu_device_id.h>
#include <asm/i387.h>
#include <asm/fpu-internal.h>

#define CHKSUM_BLOCK_SIZE	1
#define CHKSUM_DIGEST_SIZE	4

#define SCALE_F	sizeof(unsigned long)

#ifdef CONFIG_X86_64
#define REX_PRE "0x48, "
#else
#define REX_PRE
#endif

#ifdef CONFIG_X86_64
/*
 * use carryless multiply version of crc32c when buffer
 * size is >= 512 (when eager fpu is enabled) or
 * >= 1024 (when eager fpu is disabled) to account
 * for fpu state save/restore overhead.
 */
#define CRC32C_PCL_BREAKEVEN_EAGERFPU	512
#define CRC32C_PCL_BREAKEVEN_NOEAGERFPU	1024

asmlinkage unsigned int crc_pcl(const u8 *buffer, int len,
				unsigned int crc_init);
static int crc32c_pcl_breakeven = CRC32C_PCL_BREAKEVEN_EAGERFPU;
#if defined(X86_FEATURE_EAGER_FPU)
#define set_pcl_breakeven_point()					\
do {									\
	if (!use_eager_fpu())						\
		crc32c_pcl_breakeven = CRC32C_PCL_BREAKEVEN_NOEAGERFPU;	\
} while (0)
#else
#define set_pcl_breakeven_point()					\
	(crc32c_pcl_breakeven = CRC32C_PCL_BREAKEVEN_NOEAGERFPU)
#endif
#endif /* CONFIG_X86_64 */

static u32 crc32c_intel_le_hw_byte(u32 crc, unsigned char const *data, size_t length)
{
	while (length--) {
		__asm__ __volatile__(
			".byte 0xf2, 0xf, 0x38, 0xf0, 0xf1"
			:"=S"(crc)
			:"0"(crc), "c"(*data)
		);
		data++;
	}

	return crc;
}

static u32 __pure crc32c_intel_le_hw(u32 crc, unsigned char const *p, size_t len)
{
	unsigned int iquotient = len / SCALE_F;
	unsigned int iremainder = len % SCALE_F;
	unsigned long *ptmp = (unsigned long *)p;

	while (iquotient--) {
		__asm__ __volatile__(
			".byte 0xf2, " REX_PRE "0xf, 0x38, 0xf1, 0xf1;"
			:"=S"(crc)
			:"0"(crc), "c"(*ptmp)
		);
		ptmp++;
	}

	if (iremainder)
		crc = crc32c_intel_le_hw_byte(crc, (unsigned char *)ptmp,
				 iremainder);

	return crc;
}

/*
 * Setting the seed allows arbitrary accumulators and flexible XOR policy
 * If your algorithm starts with ~0, then XOR with ~0 before you set
 * the seed.
 */
static int crc32c_intel_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 crc32c_intel_init(struct shash_desc *desc)
{
	u32 *mctx = crypto_shash_ctx(desc->tfm);
	u32 *crcp = shash_desc_ctx(desc);

	*crcp = *mctx;

	return 0;
}

static int crc32c_intel_update(struct shash_desc *desc, const u8 *data,
			       unsigned int len)
{
	u32 *crcp = shash_desc_ctx(desc);

	*crcp = crc32c_intel_le_hw(*crcp, data, len);
	return 0;
}

static int __crc32c_intel_finup(u32 *crcp, const u8 *data, unsigned int len,
				u8 *out)
{
	*(__le32 *)out = ~cpu_to_le32(crc32c_intel_le_hw(*crcp, data, len));
	return 0;
}

static int crc32c_intel_finup(struct shash_desc *desc, const u8 *data,
			      unsigned int len, u8 *out)
{
	return __crc32c_intel_finup(shash_desc_ctx(desc), data, len, out);
}

static int crc32c_intel_final(struct shash_desc *desc, u8 *out)
{
	u32 *crcp = shash_desc_ctx(desc);

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

static int crc32c_intel_digest(struct shash_desc *desc, const u8 *data,
			       unsigned int len, u8 *out)
{
	return __crc32c_intel_finup(crypto_shash_ctx(desc->tfm), data, len,
				    out);
}

static int crc32c_intel_cra_init(struct crypto_tfm *tfm)
{
	u32 *key = crypto_tfm_ctx(tfm);

	*key = ~0;

	return 0;
}

#ifdef CONFIG_X86_64
static int crc32c_pcl_intel_update(struct shash_desc *desc, const u8 *data,
			       unsigned int len)
{
	u32 *crcp = shash_desc_ctx(desc);

	/*
	 * use faster PCL version if datasize is large enough to
	 * overcome kernel fpu state save/restore overhead
	 */
	if (len >= crc32c_pcl_breakeven && irq_fpu_usable()) {
		kernel_fpu_begin();
		*crcp = crc_pcl(data, len, *crcp);
		kernel_fpu_end();
	} else
		*crcp = crc32c_intel_le_hw(*crcp, data, len);
	return 0;
}

static int __crc32c_pcl_intel_finup(u32 *crcp, const u8 *data, unsigned int len,
				u8 *out)
{
	if (len >= crc32c_pcl_breakeven && irq_fpu_usable()) {
		kernel_fpu_begin();
		*(__le32 *)out = ~cpu_to_le32(crc_pcl(data, len, *crcp));
		kernel_fpu_end();
	} else
		*(__le32 *)out =
			~cpu_to_le32(crc32c_intel_le_hw(*crcp, data, len));
	return 0;
}

static int crc32c_pcl_intel_finup(struct shash_desc *desc, const u8 *data,
			      unsigned int len, u8 *out)
{
	return __crc32c_pcl_intel_finup(shash_desc_ctx(desc), data, len, out);
}

static int crc32c_pcl_intel_digest(struct shash_desc *desc, const u8 *data,
			       unsigned int len, u8 *out)
{
	return __crc32c_pcl_intel_finup(crypto_shash_ctx(desc->tfm), data, len,
				    out);
}
#endif /* CONFIG_X86_64 */

static struct shash_alg alg = {
	.setkey			=	crc32c_intel_setkey,
	.init			=	crc32c_intel_init,
	.update			=	crc32c_intel_update,
	.final			=	crc32c_intel_final,
	.finup			=	crc32c_intel_finup,
	.digest			=	crc32c_intel_digest,
	.descsize		=	sizeof(u32),
	.digestsize		=	CHKSUM_DIGEST_SIZE,
	.base			=	{
		.cra_name		=	"crc32c",
		.cra_driver_name	=	"crc32c-intel",
		.cra_priority		=	200,
		.cra_blocksize		=	CHKSUM_BLOCK_SIZE,
		.cra_ctxsize		=	sizeof(u32),
		.cra_module		=	THIS_MODULE,
		.cra_init		=	crc32c_intel_cra_init,
	}
};

static const struct x86_cpu_id crc32c_cpu_id[] = {
	X86_FEATURE_MATCH(X86_FEATURE_XMM4_2),
	{}
};
MODULE_DEVICE_TABLE(x86cpu, crc32c_cpu_id);

static int __init crc32c_intel_mod_init(void)
{
	if (!x86_match_cpu(crc32c_cpu_id))
		return -ENODEV;
#ifdef CONFIG_X86_64
	if (cpu_has_pclmulqdq) {
		alg.update = crc32c_pcl_intel_update;
		alg.finup = crc32c_pcl_intel_finup;
		alg.digest = crc32c_pcl_intel_digest;
		set_pcl_breakeven_point();
	}
#endif
	return crypto_register_shash(&alg);
}

static void __exit crc32c_intel_mod_fini(void)
{
	crypto_unregister_shash(&alg);
}

module_init(crc32c_intel_mod_init);
module_exit(crc32c_intel_mod_fini);

MODULE_AUTHOR("Austin Zhang <austin.zhang@intel.com>, Kent Liu <kent.liu@intel.com>");
MODULE_DESCRIPTION("CRC32c (Castagnoli) optimization using Intel Hardware.");
MODULE_LICENSE("GPL");

MODULE_ALIAS("crc32c");
MODULE_ALIAS("crc32c-intel");