/*
 * Glue code for AES implementation for SPE instructions (PPC)
 *
 * Based on generic implementation. The assembler module takes care
 * about the SPE registers so it can run from interrupt context.
 *
 * Copyright (c) 2015 Markus Stockhausen <stockhausen@collogia.de>
 *
 * 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; either version 2 of the License, or (at your option)
 * any later version.
 *
 */

#include <crypto/aes.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/crypto.h>
#include <asm/byteorder.h>
#include <asm/switch_to.h>
#include <crypto/algapi.h>
#include <crypto/xts.h>

/*
 * MAX_BYTES defines the number of bytes that are allowed to be processed
 * between preempt_disable() and preempt_enable(). e500 cores can issue two
 * instructions per clock cycle using one 32/64 bit unit (SU1) and one 32
 * bit unit (SU2). One of these can be a memory access that is executed via
 * a single load and store unit (LSU). XTS-AES-256 takes ~780 operations per
 * 16 byte block block or 25 cycles per byte. Thus 768 bytes of input data
 * will need an estimated maximum of 20,000 cycles. Headroom for cache misses
 * included. Even with the low end model clocked at 667 MHz this equals to a
 * critical time window of less than 30us. The value has been chosen to
 * process a 512 byte disk block in one or a large 1400 bytes IPsec network
 * packet in two runs.
 *
 */
#define MAX_BYTES 768

struct ppc_aes_ctx {
	u32 key_enc[AES_MAX_KEYLENGTH_U32];
	u32 key_dec[AES_MAX_KEYLENGTH_U32];
	u32 rounds;
};

struct ppc_xts_ctx {
	u32 key_enc[AES_MAX_KEYLENGTH_U32];
	u32 key_dec[AES_MAX_KEYLENGTH_U32];
	u32 key_twk[AES_MAX_KEYLENGTH_U32];
	u32 rounds;
};

extern void ppc_encrypt_aes(u8 *out, const u8 *in, u32 *key_enc, u32 rounds);
extern void ppc_decrypt_aes(u8 *out, const u8 *in, u32 *key_dec, u32 rounds);
extern void ppc_encrypt_ecb(u8 *out, const u8 *in, u32 *key_enc, u32 rounds,
			    u32 bytes);
extern void ppc_decrypt_ecb(u8 *out, const u8 *in, u32 *key_dec, u32 rounds,
			    u32 bytes);
extern void ppc_encrypt_cbc(u8 *out, const u8 *in, u32 *key_enc, u32 rounds,
			    u32 bytes, u8 *iv);
extern void ppc_decrypt_cbc(u8 *out, const u8 *in, u32 *key_dec, u32 rounds,
			    u32 bytes, u8 *iv);
extern void ppc_crypt_ctr  (u8 *out, const u8 *in, u32 *key_enc, u32 rounds,
			    u32 bytes, u8 *iv);
extern void ppc_encrypt_xts(u8 *out, const u8 *in, u32 *key_enc, u32 rounds,
			    u32 bytes, u8 *iv, u32 *key_twk);
extern void ppc_decrypt_xts(u8 *out, const u8 *in, u32 *key_dec, u32 rounds,
			    u32 bytes, u8 *iv, u32 *key_twk);

extern void ppc_expand_key_128(u32 *key_enc, const u8 *key);
extern void ppc_expand_key_192(u32 *key_enc, const u8 *key);
extern void ppc_expand_key_256(u32 *key_enc, const u8 *key);

extern void ppc_generate_decrypt_key(u32 *key_dec,u32 *key_enc,
				     unsigned int key_len);

static void spe_begin(void)
{
	/* disable preemption and save users SPE registers if required */
	preempt_disable();
	enable_kernel_spe();
}

static void spe_end(void)
{
	disable_kernel_spe();
	/* reenable preemption */
	preempt_enable();
}

static int ppc_aes_setkey(struct crypto_tfm *tfm, const u8 *in_key,
		unsigned int key_len)
{
	struct ppc_aes_ctx *ctx = crypto_tfm_ctx(tfm);

	if (key_len != AES_KEYSIZE_128 &&
	    key_len != AES_KEYSIZE_192 &&
	    key_len != AES_KEYSIZE_256) {
		tfm->crt_flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
		return -EINVAL;
	}

	switch (key_len) {
	case AES_KEYSIZE_128:
		ctx->rounds = 4;
		ppc_expand_key_128(ctx->key_enc, in_key);
		break;
	case AES_KEYSIZE_192:
		ctx->rounds = 5;
		ppc_expand_key_192(ctx->key_enc, in_key);
		break;
	case AES_KEYSIZE_256:
		ctx->rounds = 6;
		ppc_expand_key_256(ctx->key_enc, in_key);
		break;
	}

	ppc_generate_decrypt_key(ctx->key_dec, ctx->key_enc, key_len);

	return 0;
}

static int ppc_xts_setkey(struct crypto_tfm *tfm, const u8 *in_key,
		   unsigned int key_len)
{
	struct ppc_xts_ctx *ctx = crypto_tfm_ctx(tfm);
	int err;

	err = xts_check_key(tfm, in_key, key_len);
	if (err)
		return err;

	key_len >>= 1;

	if (key_len != AES_KEYSIZE_128 &&
	    key_len != AES_KEYSIZE_192 &&
	    key_len != AES_KEYSIZE_256) {
		tfm->crt_flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
		return -EINVAL;
	}

	switch (key_len) {
	case AES_KEYSIZE_128:
		ctx->rounds = 4;
		ppc_expand_key_128(ctx->key_enc, in_key);
		ppc_expand_key_128(ctx->key_twk, in_key + AES_KEYSIZE_128);
		break;
	case AES_KEYSIZE_192:
		ctx->rounds = 5;
		ppc_expand_key_192(ctx->key_enc, in_key);
		ppc_expand_key_192(ctx->key_twk, in_key + AES_KEYSIZE_192);
		break;
	case AES_KEYSIZE_256:
		ctx->rounds = 6;
		ppc_expand_key_256(ctx->key_enc, in_key);
		ppc_expand_key_256(ctx->key_twk, in_key + AES_KEYSIZE_256);
		break;
	}

	ppc_generate_decrypt_key(ctx->key_dec, ctx->key_enc, key_len);

	return 0;
}

static void ppc_aes_encrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
{
	struct ppc_aes_ctx *ctx = crypto_tfm_ctx(tfm);

	spe_begin();
	ppc_encrypt_aes(out, in, ctx->key_enc, ctx->rounds);
	spe_end();
}

static void ppc_aes_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
{
	struct ppc_aes_ctx *ctx = crypto_tfm_ctx(tfm);

	spe_begin();
	ppc_decrypt_aes(out, in, ctx->key_dec, ctx->rounds);
	spe_end();
}

static int ppc_ecb_encrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
			   struct scatterlist *src, unsigned int nbytes)
{
	struct ppc_aes_ctx *ctx = crypto_blkcipher_ctx(desc->tfm);
	struct blkcipher_walk walk;
	unsigned int ubytes;
	int err;

	desc->flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
	blkcipher_walk_init(&walk, dst, src, nbytes);
	err = blkcipher_walk_virt(desc, &walk);

	while ((nbytes = walk.nbytes)) {
		ubytes = nbytes > MAX_BYTES ?
			 nbytes - MAX_BYTES : nbytes & (AES_BLOCK_SIZE - 1);
		nbytes -= ubytes;

		spe_begin();
		ppc_encrypt_ecb(walk.dst.virt.addr, walk.src.virt.addr,
				ctx->key_enc, ctx->rounds, nbytes);
		spe_end();

		err = blkcipher_walk_done(desc, &walk, ubytes);
	}

	return err;
}

static int ppc_ecb_decrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
			   struct scatterlist *src, unsigned int nbytes)
{
	struct ppc_aes_ctx *ctx = crypto_blkcipher_ctx(desc->tfm);
	struct blkcipher_walk walk;
	unsigned int ubytes;
	int err;

	desc->flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
	blkcipher_walk_init(&walk, dst, src, nbytes);
	err = blkcipher_walk_virt(desc, &walk);

	while ((nbytes = walk.nbytes)) {
		ubytes = nbytes > MAX_BYTES ?
			 nbytes - MAX_BYTES : nbytes & (AES_BLOCK_SIZE - 1);
		nbytes -= ubytes;

		spe_begin();
		ppc_decrypt_ecb(walk.dst.virt.addr, walk.src.virt.addr,
				ctx->key_dec, ctx->rounds, nbytes);
		spe_end();

		err = blkcipher_walk_done(desc, &walk, ubytes);
	}

	return err;
}

static int ppc_cbc_encrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
			   struct scatterlist *src, unsigned int nbytes)
{
	struct ppc_aes_ctx *ctx = crypto_blkcipher_ctx(desc->tfm);
	struct blkcipher_walk walk;
	unsigned int ubytes;
	int err;

	desc->flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
	blkcipher_walk_init(&walk, dst, src, nbytes);
	err = blkcipher_walk_virt(desc, &walk);

	while ((nbytes = walk.nbytes)) {
		ubytes = nbytes > MAX_BYTES ?
			 nbytes - MAX_BYTES : nbytes & (AES_BLOCK_SIZE - 1);
		nbytes -= ubytes;

		spe_begin();
		ppc_encrypt_cbc(walk.dst.virt.addr, walk.src.virt.addr,
				ctx->key_enc, ctx->rounds, nbytes, walk.iv);
		spe_end();

		err = blkcipher_walk_done(desc, &walk, ubytes);
	}

	return err;
}

static int ppc_cbc_decrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
			   struct scatterlist *src, unsigned int nbytes)
{
	struct ppc_aes_ctx *ctx = crypto_blkcipher_ctx(desc->tfm);
	struct blkcipher_walk walk;
	unsigned int ubytes;
	int err;

	desc->flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
	blkcipher_walk_init(&walk, dst, src, nbytes);
	err = blkcipher_walk_virt(desc, &walk);

	while ((nbytes = walk.nbytes)) {
		ubytes = nbytes > MAX_BYTES ?
			 nbytes - MAX_BYTES : nbytes & (AES_BLOCK_SIZE - 1);
		nbytes -= ubytes;

		spe_begin();
		ppc_decrypt_cbc(walk.dst.virt.addr, walk.src.virt.addr,
				ctx->key_dec, ctx->rounds, nbytes, walk.iv);
		spe_end();

		err = blkcipher_walk_done(desc, &walk, ubytes);
	}

	return err;
}

static int ppc_ctr_crypt(struct blkcipher_desc *desc, struct scatterlist *dst,
			 struct scatterlist *src, unsigned int nbytes)
{
	struct ppc_aes_ctx *ctx = crypto_blkcipher_ctx(desc->tfm);
	struct blkcipher_walk walk;
	unsigned int pbytes, ubytes;
	int err;

	desc->flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
	blkcipher_walk_init(&walk, dst, src, nbytes);
	err = blkcipher_walk_virt_block(desc, &walk, AES_BLOCK_SIZE);

	while ((pbytes = walk.nbytes)) {
		pbytes = pbytes > MAX_BYTES ? MAX_BYTES : pbytes;
		pbytes = pbytes == nbytes ?
			 nbytes : pbytes & ~(AES_BLOCK_SIZE - 1);
		ubytes = walk.nbytes - pbytes;

		spe_begin();
		ppc_crypt_ctr(walk.dst.virt.addr, walk.src.virt.addr,
			      ctx->key_enc, ctx->rounds, pbytes , walk.iv);
		spe_end();

		nbytes -= pbytes;
		err = blkcipher_walk_done(desc, &walk, ubytes);
	}

	return err;
}

static int ppc_xts_encrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
			   struct scatterlist *src, unsigned int nbytes)
{
	struct ppc_xts_ctx *ctx = crypto_blkcipher_ctx(desc->tfm);
	struct blkcipher_walk walk;
	unsigned int ubytes;
	int err;
	u32 *twk;

	desc->flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
	blkcipher_walk_init(&walk, dst, src, nbytes);
	err = blkcipher_walk_virt(desc, &walk);
	twk = ctx->key_twk;

	while ((nbytes = walk.nbytes)) {
		ubytes = nbytes > MAX_BYTES ?
			 nbytes - MAX_BYTES : nbytes & (AES_BLOCK_SIZE - 1);
		nbytes -= ubytes;

		spe_begin();
		ppc_encrypt_xts(walk.dst.virt.addr, walk.src.virt.addr,
				ctx->key_enc, ctx->rounds, nbytes, walk.iv, twk);
		spe_end();

		twk = NULL;
		err = blkcipher_walk_done(desc, &walk, ubytes);
	}

	return err;
}

static int ppc_xts_decrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
			   struct scatterlist *src, unsigned int nbytes)
{
	struct ppc_xts_ctx *ctx = crypto_blkcipher_ctx(desc->tfm);
	struct blkcipher_walk walk;
	unsigned int ubytes;
	int err;
	u32 *twk;

	desc->flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
	blkcipher_walk_init(&walk, dst, src, nbytes);
	err = blkcipher_walk_virt(desc, &walk);
	twk = ctx->key_twk;

	while ((nbytes = walk.nbytes)) {
		ubytes = nbytes > MAX_BYTES ?
			 nbytes - MAX_BYTES : nbytes & (AES_BLOCK_SIZE - 1);
		nbytes -= ubytes;

		spe_begin();
		ppc_decrypt_xts(walk.dst.virt.addr, walk.src.virt.addr,
				ctx->key_dec, ctx->rounds, nbytes, walk.iv, twk);
		spe_end();

		twk = NULL;
		err = blkcipher_walk_done(desc, &walk, ubytes);
	}

	return err;
}

/*
 * Algorithm definitions. Disabling alignment (cra_alignmask=0) was chosen
 * because the e500 platform can handle unaligned reads/writes very efficently.
 * This improves IPsec thoughput by another few percent. Additionally we assume
 * that AES context is always aligned to at least 8 bytes because it is created
 * with kmalloc() in the crypto infrastructure
 *
 */
static struct crypto_alg aes_algs[] = { {
	.cra_name		=	"aes",
	.cra_driver_name	=	"aes-ppc-spe",
	.cra_priority		=	300,
	.cra_flags		=	CRYPTO_ALG_TYPE_CIPHER,
	.cra_blocksize		=	AES_BLOCK_SIZE,
	.cra_ctxsize		=	sizeof(struct ppc_aes_ctx),
	.cra_alignmask		=	0,
	.cra_module		=	THIS_MODULE,
	.cra_u			=	{
		.cipher = {
			.cia_min_keysize	=	AES_MIN_KEY_SIZE,
			.cia_max_keysize	=	AES_MAX_KEY_SIZE,
			.cia_setkey		=	ppc_aes_setkey,
			.cia_encrypt		=	ppc_aes_encrypt,
			.cia_decrypt		=	ppc_aes_decrypt
		}
	}
}, {
	.cra_name		=	"ecb(aes)",
	.cra_driver_name	=	"ecb-ppc-spe",
	.cra_priority		=	300,
	.cra_flags		=	CRYPTO_ALG_TYPE_BLKCIPHER,
	.cra_blocksize		=	AES_BLOCK_SIZE,
	.cra_ctxsize		=	sizeof(struct ppc_aes_ctx),
	.cra_alignmask		=	0,
	.cra_type		=	&crypto_blkcipher_type,
	.cra_module		=	THIS_MODULE,
	.cra_u = {
		.blkcipher = {
			.min_keysize		=	AES_MIN_KEY_SIZE,
			.max_keysize		=	AES_MAX_KEY_SIZE,
			.ivsize			=	AES_BLOCK_SIZE,
			.setkey			=	ppc_aes_setkey,
			.encrypt		=	ppc_ecb_encrypt,
			.decrypt		=	ppc_ecb_decrypt,
		}
	}
}, {
	.cra_name		=	"cbc(aes)",
	.cra_driver_name	=	"cbc-ppc-spe",
	.cra_priority		=	300,
	.cra_flags		=	CRYPTO_ALG_TYPE_BLKCIPHER,
	.cra_blocksize		=	AES_BLOCK_SIZE,
	.cra_ctxsize		=	sizeof(struct ppc_aes_ctx),
	.cra_alignmask		=	0,
	.cra_type		=	&crypto_blkcipher_type,
	.cra_module		=	THIS_MODULE,
	.cra_u = {
		.blkcipher = {
			.min_keysize		=	AES_MIN_KEY_SIZE,
			.max_keysize		=	AES_MAX_KEY_SIZE,
			.ivsize			=	AES_BLOCK_SIZE,
			.setkey			=	ppc_aes_setkey,
			.encrypt		=	ppc_cbc_encrypt,
			.decrypt		=	ppc_cbc_decrypt,
		}
	}
}, {
	.cra_name		=	"ctr(aes)",
	.cra_driver_name	=	"ctr-ppc-spe",
	.cra_priority		=	300,
	.cra_flags		=	CRYPTO_ALG_TYPE_BLKCIPHER,
	.cra_blocksize		=	1,
	.cra_ctxsize		=	sizeof(struct ppc_aes_ctx),
	.cra_alignmask		=	0,
	.cra_type		=	&crypto_blkcipher_type,
	.cra_module		=	THIS_MODULE,
	.cra_u = {
		.blkcipher = {
			.min_keysize		=	AES_MIN_KEY_SIZE,
			.max_keysize		=	AES_MAX_KEY_SIZE,
			.ivsize			=	AES_BLOCK_SIZE,
			.setkey			=	ppc_aes_setkey,
			.encrypt		=	ppc_ctr_crypt,
			.decrypt		=	ppc_ctr_crypt,
		}
	}
}, {
	.cra_name		=	"xts(aes)",
	.cra_driver_name	=	"xts-ppc-spe",
	.cra_priority		=	300,
	.cra_flags		=	CRYPTO_ALG_TYPE_BLKCIPHER,
	.cra_blocksize		=	AES_BLOCK_SIZE,
	.cra_ctxsize		=	sizeof(struct ppc_xts_ctx),
	.cra_alignmask		=	0,
	.cra_type		=	&crypto_blkcipher_type,
	.cra_module		=	THIS_MODULE,
	.cra_u = {
		.blkcipher = {
			.min_keysize		=	AES_MIN_KEY_SIZE * 2,
			.max_keysize		=	AES_MAX_KEY_SIZE * 2,
			.ivsize			=	AES_BLOCK_SIZE,
			.setkey			=	ppc_xts_setkey,
			.encrypt		=	ppc_xts_encrypt,
			.decrypt		=	ppc_xts_decrypt,
		}
	}
} };

static int __init ppc_aes_mod_init(void)
{
	return crypto_register_algs(aes_algs, ARRAY_SIZE(aes_algs));
}

static void __exit ppc_aes_mod_fini(void)
{
	crypto_unregister_algs(aes_algs, ARRAY_SIZE(aes_algs));
}

module_init(ppc_aes_mod_init);
module_exit(ppc_aes_mod_fini);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("AES-ECB/CBC/CTR/XTS, SPE optimized");

MODULE_ALIAS_CRYPTO("aes");
MODULE_ALIAS_CRYPTO("ecb(aes)");
MODULE_ALIAS_CRYPTO("cbc(aes)");
MODULE_ALIAS_CRYPTO("ctr(aes)");
MODULE_ALIAS_CRYPTO("xts(aes)");
MODULE_ALIAS_CRYPTO("aes-ppc-spe");