// 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 <stockhausen@collogia.de>
 */

#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");