/**
 * 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();
	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();
	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();
			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,
	},
};