/*
 * aes-ce-cipher.c - core AES cipher using ARMv8 Crypto Extensions
 *
 * Copyright (C) 2013 - 2017 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/simd.h>
#include <asm/unaligned.h>
#include <crypto/aes.h>
#include <linux/cpufeature.h>
#include <linux/crypto.h>
#include <linux/module.h>

#include "aes-ce-setkey.h"

MODULE_DESCRIPTION("Synchronous AES cipher using ARMv8 Crypto Extensions");
MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
MODULE_LICENSE("GPL v2");

asmlinkage void __aes_arm64_encrypt(u32 *rk, u8 *out, const u8 *in, int rounds);
asmlinkage void __aes_arm64_decrypt(u32 *rk, u8 *out, const u8 *in, int rounds);

struct aes_block {
        u8 b[AES_BLOCK_SIZE];
};

asmlinkage void __aes_ce_encrypt(u32 *rk, u8 *out, const u8 *in, int rounds);
asmlinkage void __aes_ce_decrypt(u32 *rk, u8 *out, const u8 *in, int rounds);

asmlinkage u32 __aes_ce_sub(u32 l);
asmlinkage void __aes_ce_invert(struct aes_block *out,
                                const struct aes_block *in);

static int num_rounds(struct crypto_aes_ctx *ctx)
{
        /*
         * # of rounds specified by AES:
         * 128 bit key          10 rounds
         * 192 bit key          12 rounds
         * 256 bit key          14 rounds
         * => n byte key        => 6 + (n/4) rounds
         */
        return 6 + ctx->key_length / 4;
}

static void aes_cipher_encrypt(struct crypto_tfm *tfm, u8 dst[], u8 const src[])
{
        struct crypto_aes_ctx *ctx = crypto_tfm_ctx(tfm);

        if (!may_use_simd()) {
                __aes_arm64_encrypt(ctx->key_enc, dst, src, num_rounds(ctx));
                return;
        }

        kernel_neon_begin();
        __aes_ce_encrypt(ctx->key_enc, dst, src, num_rounds(ctx));
        kernel_neon_end();
}

static void aes_cipher_decrypt(struct crypto_tfm *tfm, u8 dst[], u8 const src[])
{
        struct crypto_aes_ctx *ctx = crypto_tfm_ctx(tfm);

        if (!may_use_simd()) {
                __aes_arm64_decrypt(ctx->key_dec, dst, src, num_rounds(ctx));
                return;
        }

        kernel_neon_begin();
        __aes_ce_decrypt(ctx->key_dec, dst, src, num_rounds(ctx));
        kernel_neon_end();
}

int ce_aes_expandkey(struct crypto_aes_ctx *ctx, const u8 *in_key,
                     unsigned int key_len)
{
        /*
         * The AES key schedule round constants
         */
        static u8 const rcon[] = {
                0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36,
        };

        u32 kwords = key_len / sizeof(u32);
        struct aes_block *key_enc, *key_dec;
        int i, j;

        if (key_len != AES_KEYSIZE_128 &&
            key_len != AES_KEYSIZE_192 &&
            key_len != AES_KEYSIZE_256)
                return -EINVAL;

        ctx->key_length = key_len;
        for (i = 0; i < kwords; i++)
                ctx->key_enc[i] = get_unaligned_le32(in_key + i * sizeof(u32));

        kernel_neon_begin();
        for (i = 0; i < sizeof(rcon); i++) {
                u32 *rki = ctx->key_enc + (i * kwords);
                u32 *rko = rki + kwords;

                rko[0] = ror32(__aes_ce_sub(rki[kwords - 1]), 8) ^ rcon[i] ^ rki[0];
                rko[1] = rko[0] ^ rki[1];
                rko[2] = rko[1] ^ rki[2];
                rko[3] = rko[2] ^ rki[3];

                if (key_len == AES_KEYSIZE_192) {
                        if (i >= 7)
                                break;
                        rko[4] = rko[3] ^ rki[4];
                        rko[5] = rko[4] ^ rki[5];
                } else if (key_len == AES_KEYSIZE_256) {
                        if (i >= 6)
                                break;
                        rko[4] = __aes_ce_sub(rko[3]) ^ rki[4];
                        rko[5] = rko[4] ^ rki[5];
                        rko[6] = rko[5] ^ rki[6];
                        rko[7] = rko[6] ^ rki[7];
                }
        }

        /*
         * Generate the decryption keys for the Equivalent Inverse Cipher.
         * This involves reversing the order of the round keys, and applying
         * the Inverse Mix Columns transformation on all but the first and
         * the last one.
         */
        key_enc = (struct aes_block *)ctx->key_enc;
        key_dec = (struct aes_block *)ctx->key_dec;
        j = num_rounds(ctx);

        key_dec[0] = key_enc[j];
        for (i = 1, j--; j > 0; i++, j--)
                __aes_ce_invert(key_dec + i, key_enc + j);
        key_dec[i] = key_enc[0];

        kernel_neon_end();
        return 0;
}
EXPORT_SYMBOL(ce_aes_expandkey);

int ce_aes_setkey(struct crypto_tfm *tfm, const u8 *in_key,
                  unsigned int key_len)
{
        struct crypto_aes_ctx *ctx = crypto_tfm_ctx(tfm);
        int ret;

        ret = ce_aes_expandkey(ctx, in_key, key_len);
        if (!ret)
                return 0;

        tfm->crt_flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
        return -EINVAL;
}
EXPORT_SYMBOL(ce_aes_setkey);

static struct crypto_alg aes_alg = {
        .cra_name               = "aes",
        .cra_driver_name        = "aes-ce",
        .cra_priority           = 250,
        .cra_flags              = CRYPTO_ALG_TYPE_CIPHER,
        .cra_blocksize          = AES_BLOCK_SIZE,
        .cra_ctxsize            = sizeof(struct crypto_aes_ctx),
        .cra_module             = THIS_MODULE,
        .cra_cipher = {
                .cia_min_keysize        = AES_MIN_KEY_SIZE,
                .cia_max_keysize        = AES_MAX_KEY_SIZE,
                .cia_setkey             = ce_aes_setkey,
                .cia_encrypt            = aes_cipher_encrypt,
                .cia_decrypt            = aes_cipher_decrypt
        }
};

static int __init aes_mod_init(void)
{
        return crypto_register_alg(&aes_alg);
}

static void __exit aes_mod_exit(void)
{
        crypto_unregister_alg(&aes_alg);
}

module_cpu_feature_match(AES, aes_mod_init);
module_exit(aes_mod_exit);