/**
 * AES CTR routines supporting VMX instructions on the Power 8
 *
 * Copyright (C) 2015 International Business Machines Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2 only.
 *
 * 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 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * Author: Marcelo Henrique Cerri <mhcerri@br.ibm.com>
 */

#include <linux/types.h>
#include <linux/err.h>
#include <linux/crypto.h>
#include <linux/delay.h>
#include <linux/hardirq.h>
#include <asm/switch_to.h>
#include <crypto/aes.h>
#include <crypto/scatterwalk.h>
#include "aesp8-ppc.h"

struct p8_aes_ctr_ctx {
    struct crypto_blkcipher *fallback;
    struct aes_key enc_key;
};

static int p8_aes_ctr_init(struct crypto_tfm *tfm)
{
    const char *alg;
    struct crypto_blkcipher *fallback;
    struct p8_aes_ctr_ctx *ctx = crypto_tfm_ctx(tfm);

    if (!(alg = crypto_tfm_alg_name(tfm))) {
        printk(KERN_ERR "Failed to get algorithm name.\n");
        return -ENOENT;
    }

    fallback = crypto_alloc_blkcipher(alg, 0 ,CRYPTO_ALG_NEED_FALLBACK);
    if (IS_ERR(fallback)) {
        printk(KERN_ERR "Failed to allocate transformation for '%s': %ld\n",
                alg, PTR_ERR(fallback));
        return PTR_ERR(fallback);
    }
    printk(KERN_INFO "Using '%s' as fallback implementation.\n",
            crypto_tfm_alg_driver_name((struct crypto_tfm *) fallback));

    crypto_blkcipher_set_flags(fallback,
            crypto_blkcipher_get_flags((struct crypto_blkcipher *) tfm));
    ctx->fallback = fallback;

    return 0;
}

static void p8_aes_ctr_exit(struct crypto_tfm *tfm)
{
    struct p8_aes_ctr_ctx *ctx = crypto_tfm_ctx(tfm);

    if (ctx->fallback) {
        crypto_free_blkcipher(ctx->fallback);
        ctx->fallback = NULL;
    }
}

static int p8_aes_ctr_setkey(struct crypto_tfm *tfm, const u8 *key,
    unsigned int keylen)
{
    int ret;
    struct p8_aes_ctr_ctx *ctx = crypto_tfm_ctx(tfm);

    pagefault_disable();
    enable_kernel_altivec();
    enable_kernel_vsx();
    ret = aes_p8_set_encrypt_key(key, keylen * 8, &ctx->enc_key);
    pagefault_enable();

    ret += crypto_blkcipher_setkey(ctx->fallback, key, keylen);
    return ret;
}

static void p8_aes_ctr_final(struct p8_aes_ctr_ctx *ctx,
                struct blkcipher_walk *walk)
{
    u8 *ctrblk = walk->iv;
    u8 keystream[AES_BLOCK_SIZE];
    u8 *src = walk->src.virt.addr;
    u8 *dst = walk->dst.virt.addr;
    unsigned int nbytes = walk->nbytes;

    pagefault_disable();
    enable_kernel_altivec();
    enable_kernel_vsx();
    aes_p8_encrypt(ctrblk, keystream, &ctx->enc_key);
    pagefault_enable();

    crypto_xor(keystream, src, nbytes);
    memcpy(dst, keystream, nbytes);
    crypto_inc(ctrblk, AES_BLOCK_SIZE);
}

static int p8_aes_ctr_crypt(struct blkcipher_desc *desc,
    struct scatterlist *dst, struct scatterlist *src,
    unsigned int nbytes)
{
    int ret;
    struct blkcipher_walk walk;
    struct p8_aes_ctr_ctx *ctx = crypto_tfm_ctx(
            crypto_blkcipher_tfm(desc->tfm));
    struct blkcipher_desc fallback_desc = {
        .tfm = ctx->fallback,
        .info = desc->info,
        .flags = desc->flags
    };

    if (in_interrupt()) {
        ret = crypto_blkcipher_encrypt(&fallback_desc, dst, src, nbytes);
    } else {
        blkcipher_walk_init(&walk, dst, src, nbytes);
        ret = blkcipher_walk_virt_block(desc, &walk, AES_BLOCK_SIZE);
        while ((nbytes = walk.nbytes) >= AES_BLOCK_SIZE) {
            pagefault_disable();
            enable_kernel_altivec();
            enable_kernel_vsx();
            aes_p8_ctr32_encrypt_blocks(walk.src.virt.addr, walk.dst.virt.addr,
                (nbytes & AES_BLOCK_MASK)/AES_BLOCK_SIZE, &ctx->enc_key, walk.iv);
            pagefault_enable();

            crypto_inc(walk.iv, AES_BLOCK_SIZE);
            nbytes &= AES_BLOCK_SIZE - 1;
            ret = blkcipher_walk_done(desc, &walk, nbytes);
        }
        if (walk.nbytes) {
            p8_aes_ctr_final(ctx, &walk);
            ret = blkcipher_walk_done(desc, &walk, 0);
        }
    }

    return ret;
}

struct crypto_alg p8_aes_ctr_alg = {
    .cra_name = "ctr(aes)",
    .cra_driver_name = "p8_aes_ctr",
    .cra_module = THIS_MODULE,
    .cra_priority = 1000,
    .cra_type = &crypto_blkcipher_type,
    .cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER | CRYPTO_ALG_NEED_FALLBACK,
    .cra_alignmask = 0,
    .cra_blocksize = 1,
    .cra_ctxsize = sizeof(struct p8_aes_ctr_ctx),
    .cra_init = p8_aes_ctr_init,
    .cra_exit = p8_aes_ctr_exit,
    .cra_blkcipher = {
        .ivsize = 0,
        .min_keysize = AES_MIN_KEY_SIZE,
        .max_keysize = AES_MAX_KEY_SIZE,
        .setkey = p8_aes_ctr_setkey,
        .encrypt = p8_aes_ctr_crypt,
        .decrypt = p8_aes_ctr_crypt,
    },
};