aes-spe-glue.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * 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 <[email protected]>
 */

#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/internal/skcipher.h>
#include <crypto/xts.h>
#include <crypto/gf128mul.h>
#include <crypto/scatterwalk.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 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;
};

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_skcipher(struct crypto_skcipher *tfm,
				   const u8 *in_key, unsigned int key_len)
{
	struct ppc_aes_ctx *ctx = crypto_skcipher_ctx(tfm);

	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;
	default:
		return -EINVAL;
	}

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

	return 0;
}

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

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

	key_len >>= 1;

	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;
	default:
		return -EINVAL;
	}

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

	return 0;
}

static int ppc_ecb_crypt(struct skcipher_request *req, bool enc)
{
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	struct ppc_aes_ctx *ctx = crypto_skcipher_ctx(tfm);
	struct skcipher_walk walk;
	unsigned int nbytes;
	int err;

	err = skcipher_walk_virt(&walk, req, false);

	while ((nbytes = walk.nbytes) != 0) {
		nbytes = min_t(unsigned int, nbytes, MAX_BYTES);
		nbytes = round_down(nbytes, AES_BLOCK_SIZE);

		spe_begin();
		if (enc)
			ppc_encrypt_ecb(walk.dst.virt.addr, walk.src.virt.addr,
					ctx->key_enc, ctx->rounds, nbytes);
		else
			ppc_decrypt_ecb(walk.dst.virt.addr, walk.src.virt.addr,
					ctx->key_dec, ctx->rounds, nbytes);
		spe_end();

		err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
	}

	return err;
}

static int ppc_ecb_encrypt(struct skcipher_request *req)
{
	return ppc_ecb_crypt(req, true);
}

static int ppc_ecb_decrypt(struct skcipher_request *req)
{
	return ppc_ecb_crypt(req, false);
}

static int ppc_cbc_crypt(struct skcipher_request *req, bool enc)
{
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	struct ppc_aes_ctx *ctx = crypto_skcipher_ctx(tfm);
	struct skcipher_walk walk;
	unsigned int nbytes;
	int err;

	err = skcipher_walk_virt(&walk, req, false);

	while ((nbytes = walk.nbytes) != 0) {
		nbytes = min_t(unsigned int, nbytes, MAX_BYTES);
		nbytes = round_down(nbytes, AES_BLOCK_SIZE);

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

		err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
	}

	return err;
}

static int ppc_cbc_encrypt(struct skcipher_request *req)
{
	return ppc_cbc_crypt(req, true);
}

static int ppc_cbc_decrypt(struct skcipher_request *req)
{
	return ppc_cbc_crypt(req, false);
}

static int ppc_ctr_crypt(struct skcipher_request *req)
{
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	struct ppc_aes_ctx *ctx = crypto_skcipher_ctx(tfm);
	struct skcipher_walk walk;
	unsigned int nbytes;
	int err;

	err = skcipher_walk_virt(&walk, req, false);

	while ((nbytes = walk.nbytes) != 0) {
		nbytes = min_t(unsigned int, nbytes, MAX_BYTES);
		if (nbytes < walk.total)
			nbytes = round_down(nbytes, AES_BLOCK_SIZE);

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

		err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
	}

	return err;
}

static int ppc_xts_crypt(struct skcipher_request *req, bool enc)
{
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	struct ppc_xts_ctx *ctx = crypto_skcipher_ctx(tfm);
	struct skcipher_walk walk;
	unsigned int nbytes;
	int err;
	u32 *twk;

	err = skcipher_walk_virt(&walk, req, false);
	twk = ctx->key_twk;

	while ((nbytes = walk.nbytes) != 0) {
		nbytes = min_t(unsigned int, nbytes, MAX_BYTES);
		nbytes = round_down(nbytes, AES_BLOCK_SIZE);

		spe_begin();
		if (enc)
			ppc_encrypt_xts(walk.dst.virt.addr, walk.src.virt.addr,
					ctx->key_enc, ctx->rounds, nbytes,
					walk.iv, twk);
		else
			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 = skcipher_walk_done(&walk, walk.nbytes - nbytes);
	}

	return err;
}

static int ppc_xts_encrypt(struct skcipher_request *req)
{
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	struct ppc_xts_ctx *ctx = crypto_skcipher_ctx(tfm);
	int tail = req->cryptlen % AES_BLOCK_SIZE;
	int offset = req->cryptlen - tail - AES_BLOCK_SIZE;
	struct skcipher_request subreq;
	u8 b[2][AES_BLOCK_SIZE];
	int err;

	if (req->cryptlen < AES_BLOCK_SIZE)
		return -EINVAL;

	if (tail) {
		subreq = *req;
		skcipher_request_set_crypt(&subreq, req->src, req->dst,
					   req->cryptlen - tail, req->iv);
		req = &subreq;
	}

	err = ppc_xts_crypt(req, true);
	if (err || !tail)
		return err;

	scatterwalk_map_and_copy(b[0], req->dst, offset, AES_BLOCK_SIZE, 0);
	memcpy(b[1], b[0], tail);
	scatterwalk_map_and_copy(b[0], req->src, offset + AES_BLOCK_SIZE, tail, 0);

	spe_begin();
	ppc_encrypt_xts(b[0], b[0], ctx->key_enc, ctx->rounds, AES_BLOCK_SIZE,
			req->iv, NULL);
	spe_end();

	scatterwalk_map_and_copy(b[0], req->dst, offset, AES_BLOCK_SIZE + tail, 1);

	return 0;
}

static int ppc_xts_decrypt(struct skcipher_request *req)
{
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	struct ppc_xts_ctx *ctx = crypto_skcipher_ctx(tfm);
	int tail = req->cryptlen % AES_BLOCK_SIZE;
	int offset = req->cryptlen - tail - AES_BLOCK_SIZE;
	struct skcipher_request subreq;
	u8 b[3][AES_BLOCK_SIZE];
	le128 twk;
	int err;

	if (req->cryptlen < AES_BLOCK_SIZE)
		return -EINVAL;

	if (tail) {
		subreq = *req;
		skcipher_request_set_crypt(&subreq, req->src, req->dst,
					   offset, req->iv);
		req = &subreq;
	}

	err = ppc_xts_crypt(req, false);
	if (err || !tail)
		return err;

	scatterwalk_map_and_copy(b[1], req->src, offset, AES_BLOCK_SIZE + tail, 0);

	spe_begin();
	if (!offset)
		ppc_encrypt_ecb(req->iv, req->iv, ctx->key_twk, ctx->rounds,
				AES_BLOCK_SIZE);

	gf128mul_x_ble(&twk, (le128 *)req->iv);

	ppc_decrypt_xts(b[1], b[1], ctx->key_dec, ctx->rounds, AES_BLOCK_SIZE,
			(u8 *)&twk, NULL);
	memcpy(b[0], b[2], tail);
	memcpy(b[0] + tail, b[1] + tail, AES_BLOCK_SIZE - tail);
	ppc_decrypt_xts(b[0], b[0], ctx->key_dec, ctx->rounds, AES_BLOCK_SIZE,
			req->iv, NULL);
	spe_end();

	scatterwalk_map_and_copy(b[0], req->dst, offset, AES_BLOCK_SIZE + tail, 1);

	return 0;
}

/*
 * Algorithm definitions. Disabling alignment (cra_alignmask=0) was chosen
 * because the e500 platform can handle unaligned reads/writes very efficiently.
 * 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 skcipher_alg aes_skcipher_algs[] = {
	{
		.base.cra_name		=	"ecb(aes)",
		.base.cra_driver_name	=	"ecb-ppc-spe",
		.base.cra_priority	=	300,
		.base.cra_blocksize	=	AES_BLOCK_SIZE,
		.base.cra_ctxsize	=	sizeof(struct ppc_aes_ctx),
		.base.cra_module	=	THIS_MODULE,
		.min_keysize		=	AES_MIN_KEY_SIZE,
		.max_keysize		=	AES_MAX_KEY_SIZE,
		.setkey			=	ppc_aes_setkey_skcipher,
		.encrypt		=	ppc_ecb_encrypt,
		.decrypt		=	ppc_ecb_decrypt,
	}, {
		.base.cra_name		=	"cbc(aes)",
		.base.cra_driver_name	=	"cbc-ppc-spe",
		.base.cra_priority	=	300,
		.base.cra_blocksize	=	AES_BLOCK_SIZE,
		.base.cra_ctxsize	=	sizeof(struct ppc_aes_ctx),
		.base.cra_module	=	THIS_MODULE,
		.min_keysize		=	AES_MIN_KEY_SIZE,
		.max_keysize		=	AES_MAX_KEY_SIZE,
		.ivsize			=	AES_BLOCK_SIZE,
		.setkey			=	ppc_aes_setkey_skcipher,
		.encrypt		=	ppc_cbc_encrypt,
		.decrypt		=	ppc_cbc_decrypt,
	}, {
		.base.cra_name		=	"ctr(aes)",
		.base.cra_driver_name	=	"ctr-ppc-spe",
		.base.cra_priority	=	300,
		.base.cra_blocksize	=	1,
		.base.cra_ctxsize	=	sizeof(struct ppc_aes_ctx),
		.base.cra_module	=	THIS_MODULE,
		.min_keysize		=	AES_MIN_KEY_SIZE,
		.max_keysize		=	AES_MAX_KEY_SIZE,
		.ivsize			=	AES_BLOCK_SIZE,
		.setkey			=	ppc_aes_setkey_skcipher,
		.encrypt		=	ppc_ctr_crypt,
		.decrypt		=	ppc_ctr_crypt,
		.chunksize		=	AES_BLOCK_SIZE,
	}, {
		.base.cra_name		=	"xts(aes)",
		.base.cra_driver_name	=	"xts-ppc-spe",
		.base.cra_priority	=	300,
		.base.cra_blocksize	=	AES_BLOCK_SIZE,
		.base.cra_ctxsize	=	sizeof(struct ppc_xts_ctx),
		.base.cra_module	=	THIS_MODULE,
		.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_skciphers(aes_skcipher_algs,
					 ARRAY_SIZE(aes_skcipher_algs));
}

static void __exit ppc_aes_mod_fini(void)
{
	crypto_unregister_skciphers(aes_skcipher_algs,
				    ARRAY_SIZE(aes_skcipher_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");