/* 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_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");