text: // SPDX-License-Identifier: GPL-2.0
  /*
   * ARM NEON accelerated ChaCha and XChaCha stream ciphers,
   * including ChaCha20 (RFC7539)
   *
   * Copyright (C) 2016-2019 Linaro, Ltd. <ard.biesheuvel@linaro.org>
   * Copyright (C) 2015 Martin Willi
   */
  
  #include <crypto/algapi.h>
  #include <crypto/internal/chacha.h>
  #include <crypto/internal/simd.h>
  #include <crypto/internal/skcipher.h>
  #include <linux/jump_label.h>
  #include <linux/kernel.h>
  #include <linux/module.h>
  
  #include <asm/cputype.h>
  #include <asm/hwcap.h>
  #include <asm/neon.h>
  #include <asm/simd.h>
  
  asmlinkage void chacha_block_xor_neon(const u32 *state, u8 *dst, const u8 *src,
  				      int nrounds);
  asmlinkage void chacha_4block_xor_neon(const u32 *state, u8 *dst, const u8 *src,
  				       int nrounds, unsigned int nbytes);
  asmlinkage void hchacha_block_arm(const u32 *state, u32 *out, int nrounds);
  asmlinkage void hchacha_block_neon(const u32 *state, u32 *out, int nrounds);
  
  asmlinkage void chacha_doarm(u8 *dst, const u8 *src, unsigned int bytes,
  			     const u32 *state, int nrounds);
  
  static __ro_after_init DEFINE_STATIC_KEY_FALSE(use_neon);
  
  static inline bool neon_usable(void)
  {
  	return static_branch_likely(&use_neon) && crypto_simd_usable();
  }
  
  static void chacha_doneon(u32 *state, u8 *dst, const u8 *src,
  			  unsigned int bytes, int nrounds)
  {
  	u8 buf[CHACHA_BLOCK_SIZE];
  
  	while (bytes > CHACHA_BLOCK_SIZE) {
  		unsigned int l = min(bytes, CHACHA_BLOCK_SIZE * 4U);
  
  		chacha_4block_xor_neon(state, dst, src, nrounds, l);
  		bytes -= l;
  		src += l;
  		dst += l;
  		state[12] += DIV_ROUND_UP(l, CHACHA_BLOCK_SIZE);
  	}
  	if (bytes) {
  		const u8 *s = src;
  		u8 *d = dst;
  
  		if (bytes != CHACHA_BLOCK_SIZE)
  			s = d = memcpy(buf, src, bytes);
  		chacha_block_xor_neon(state, d, s, nrounds);
  		if (d != dst)
  			memcpy(dst, buf, bytes);
  		state[12]++;
  	}
  }
  
  void hchacha_block_arch(const u32 *state, u32 *stream, int nrounds)
  {
  	if (!IS_ENABLED(CONFIG_KERNEL_MODE_NEON) || !neon_usable()) {
  		hchacha_block_arm(state, stream, nrounds);
  	} else {
  		kernel_neon_begin();
  		hchacha_block_neon(state, stream, nrounds);
  		kernel_neon_end();
  	}
  }
  EXPORT_SYMBOL(hchacha_block_arch);
  
  void chacha_init_arch(u32 *state, const u32 *key, const u8 *iv)
  {
  	chacha_init_generic(state, key, iv);
  }
  EXPORT_SYMBOL(chacha_init_arch);
  
  void chacha_crypt_arch(u32 *state, u8 *dst, const u8 *src, unsigned int bytes,
  		       int nrounds)
  {
  	if (!IS_ENABLED(CONFIG_KERNEL_MODE_NEON) || !neon_usable() ||
  	    bytes <= CHACHA_BLOCK_SIZE) {
  		chacha_doarm(dst, src, bytes, state, nrounds);
  		state[12] += DIV_ROUND_UP(bytes, CHACHA_BLOCK_SIZE);
  		return;
  	}
  
  	do {
  		unsigned int todo = min_t(unsigned int, bytes, SZ_4K);
  
  		kernel_neon_begin();
  		chacha_doneon(state, dst, src, todo, nrounds);
  		kernel_neon_end();
  
  		bytes -= todo;
  		src += todo;
  		dst += todo;
  	} while (bytes);
  }
  EXPORT_SYMBOL(chacha_crypt_arch);
  
  static int chacha_stream_xor(struct skcipher_request *req,
  			     const struct chacha_ctx *ctx, const u8 *iv,
  			     bool neon)
  {
  	struct skcipher_walk walk;
  	u32 state[16];
  	int err;
  
  	err = skcipher_walk_virt(&walk, req, false);
  
  	chacha_init_generic(state, ctx->key, iv);
  
  	while (walk.nbytes > 0) {
  		unsigned int nbytes = walk.nbytes;
  
  		if (nbytes < walk.total)
  			nbytes = round_down(nbytes, walk.stride);
  
  		if (!IS_ENABLED(CONFIG_KERNEL_MODE_NEON) || !neon) {
  			chacha_doarm(walk.dst.virt.addr, walk.src.virt.addr,
  				     nbytes, state, ctx->nrounds);
  			state[12] += DIV_ROUND_UP(nbytes, CHACHA_BLOCK_SIZE);
  		} else {
  			kernel_neon_begin();
  			chacha_doneon(state, walk.dst.virt.addr,
  				      walk.src.virt.addr, nbytes, ctx->nrounds);
  			kernel_neon_end();
  		}
  		err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
  	}
  
  	return err;
  }
  
  static int do_chacha(struct skcipher_request *req, bool neon)
  {
  	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
  	struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
  
  	return chacha_stream_xor(req, ctx, req->iv, neon);
  }
  
  static int chacha_arm(struct skcipher_request *req)
  {
  	return do_chacha(req, false);
  }
  
  static int chacha_neon(struct skcipher_request *req)
  {
  	return do_chacha(req, neon_usable());
  }
  
  static int do_xchacha(struct skcipher_request *req, bool neon)
  {
  	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
  	struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
  	struct chacha_ctx subctx;
  	u32 state[16];
  	u8 real_iv[16];
  
  	chacha_init_generic(state, ctx->key, req->iv);
  
  	if (!IS_ENABLED(CONFIG_KERNEL_MODE_NEON) || !neon) {
  		hchacha_block_arm(state, subctx.key, ctx->nrounds);
  	} else {
  		kernel_neon_begin();
  		hchacha_block_neon(state, subctx.key, ctx->nrounds);
  		kernel_neon_end();
  	}
  	subctx.nrounds = ctx->nrounds;
  
  	memcpy(&real_iv[0], req->iv + 24, 8);
  	memcpy(&real_iv[8], req->iv + 16, 8);
  	return chacha_stream_xor(req, &subctx, real_iv, neon);
  }
  
  static int xchacha_arm(struct skcipher_request *req)
  {
  	return do_xchacha(req, false);
  }
  
  static int xchacha_neon(struct skcipher_request *req)
  {
  	return do_xchacha(req, neon_usable());
  }
  
  static struct skcipher_alg arm_algs[] = {
  	{
  		.base.cra_name		= "chacha20",
  		.base.cra_driver_name	= "chacha20-arm",
  		.base.cra_priority	= 200,
  		.base.cra_blocksize	= 1,
  		.base.cra_ctxsize	= sizeof(struct chacha_ctx),
  		.base.cra_module	= THIS_MODULE,
  
  		.min_keysize		= CHACHA_KEY_SIZE,
  		.max_keysize		= CHACHA_KEY_SIZE,
  		.ivsize			= CHACHA_IV_SIZE,
  		.chunksize		= CHACHA_BLOCK_SIZE,
  		.setkey			= chacha20_setkey,
  		.encrypt		= chacha_arm,
  		.decrypt		= chacha_arm,
  	}, {
  		.base.cra_name		= "xchacha20",
  		.base.cra_driver_name	= "xchacha20-arm",
  		.base.cra_priority	= 200,
  		.base.cra_blocksize	= 1,
  		.base.cra_ctxsize	= sizeof(struct chacha_ctx),
  		.base.cra_module	= THIS_MODULE,
  
  		.min_keysize		= CHACHA_KEY_SIZE,
  		.max_keysize		= CHACHA_KEY_SIZE,
  		.ivsize			= XCHACHA_IV_SIZE,
  		.chunksize		= CHACHA_BLOCK_SIZE,
  		.setkey			= chacha20_setkey,
  		.encrypt		= xchacha_arm,
  		.decrypt		= xchacha_arm,
  	}, {
  		.base.cra_name		= "xchacha12",
  		.base.cra_driver_name	= "xchacha12-arm",
  		.base.cra_priority	= 200,
  		.base.cra_blocksize	= 1,
  		.base.cra_ctxsize	= sizeof(struct chacha_ctx),
  		.base.cra_module	= THIS_MODULE,
  
  		.min_keysize		= CHACHA_KEY_SIZE,
  		.max_keysize		= CHACHA_KEY_SIZE,
  		.ivsize			= XCHACHA_IV_SIZE,
  		.chunksize		= CHACHA_BLOCK_SIZE,
  		.setkey			= chacha12_setkey,
  		.encrypt		= xchacha_arm,
  		.decrypt		= xchacha_arm,
  	},
  };
  
  static struct skcipher_alg neon_algs[] = {
  	{
  		.base.cra_name		= "chacha20",
  		.base.cra_driver_name	= "chacha20-neon",
  		.base.cra_priority	= 300,
  		.base.cra_blocksize	= 1,
  		.base.cra_ctxsize	= sizeof(struct chacha_ctx),
  		.base.cra_module	= THIS_MODULE,
  
  		.min_keysize		= CHACHA_KEY_SIZE,
  		.max_keysize		= CHACHA_KEY_SIZE,
  		.ivsize			= CHACHA_IV_SIZE,
  		.chunksize		= CHACHA_BLOCK_SIZE,
  		.walksize		= 4 * CHACHA_BLOCK_SIZE,
  		.setkey			= chacha20_setkey,
  		.encrypt		= chacha_neon,
  		.decrypt		= chacha_neon,
  	}, {
  		.base.cra_name		= "xchacha20",
  		.base.cra_driver_name	= "xchacha20-neon",
  		.base.cra_priority	= 300,
  		.base.cra_blocksize	= 1,
  		.base.cra_ctxsize	= sizeof(struct chacha_ctx),
  		.base.cra_module	= THIS_MODULE,
  
  		.min_keysize		= CHACHA_KEY_SIZE,
  		.max_keysize		= CHACHA_KEY_SIZE,
  		.ivsize			= XCHACHA_IV_SIZE,
  		.chunksize		= CHACHA_BLOCK_SIZE,
  		.walksize		= 4 * CHACHA_BLOCK_SIZE,
  		.setkey			= chacha20_setkey,
  		.encrypt		= xchacha_neon,
  		.decrypt		= xchacha_neon,
  	}, {
  		.base.cra_name		= "xchacha12",
  		.base.cra_driver_name	= "xchacha12-neon",
  		.base.cra_priority	= 300,
  		.base.cra_blocksize	= 1,
  		.base.cra_ctxsize	= sizeof(struct chacha_ctx),
  		.base.cra_module	= THIS_MODULE,
  
  		.min_keysize		= CHACHA_KEY_SIZE,
  		.max_keysize		= CHACHA_KEY_SIZE,
  		.ivsize			= XCHACHA_IV_SIZE,
  		.chunksize		= CHACHA_BLOCK_SIZE,
  		.walksize		= 4 * CHACHA_BLOCK_SIZE,
  		.setkey			= chacha12_setkey,
  		.encrypt		= xchacha_neon,
  		.decrypt		= xchacha_neon,
  	}
  };
  
  static int __init chacha_simd_mod_init(void)
  {
  	int err = 0;
  
  	if (IS_REACHABLE(CONFIG_CRYPTO_SKCIPHER)) {
  		err = crypto_register_skciphers(arm_algs, ARRAY_SIZE(arm_algs));
  		if (err)
  			return err;
  	}
  
  	if (IS_ENABLED(CONFIG_KERNEL_MODE_NEON) && (elf_hwcap & HWCAP_NEON)) {
  		int i;
  
  		switch (read_cpuid_part()) {
  		case ARM_CPU_PART_CORTEX_A7:
  		case ARM_CPU_PART_CORTEX_A5:
  			/*
  			 * The Cortex-A7 and Cortex-A5 do not perform well with
  			 * the NEON implementation but do incredibly with the
  			 * scalar one and use less power.
  			 */
  			for (i = 0; i < ARRAY_SIZE(neon_algs); i++)
  				neon_algs[i].base.cra_priority = 0;
  			break;
  		default:
  			static_branch_enable(&use_neon);
  		}
  
  		if (IS_REACHABLE(CONFIG_CRYPTO_SKCIPHER)) {
  			err = crypto_register_skciphers(neon_algs, ARRAY_SIZE(neon_algs));
  			if (err)
  				crypto_unregister_skciphers(arm_algs, ARRAY_SIZE(arm_algs));
  		}
  	}
  	return err;
  }
  
  static void __exit chacha_simd_mod_fini(void)
  {
  	if (IS_REACHABLE(CONFIG_CRYPTO_SKCIPHER)) {
  		crypto_unregister_skciphers(arm_algs, ARRAY_SIZE(arm_algs));
  		if (IS_ENABLED(CONFIG_KERNEL_MODE_NEON) && (elf_hwcap & HWCAP_NEON))
  			crypto_unregister_skciphers(neon_algs, ARRAY_SIZE(neon_algs));
  	}
  }
  
  module_init(chacha_simd_mod_init);
  module_exit(chacha_simd_mod_fini);
  
  MODULE_DESCRIPTION("ChaCha and XChaCha stream ciphers (scalar and NEON accelerated)");
  MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
  MODULE_LICENSE("GPL v2");
  MODULE_ALIAS_CRYPTO("chacha20");
  MODULE_ALIAS_CRYPTO("chacha20-arm");
  MODULE_ALIAS_CRYPTO("xchacha20");
  MODULE_ALIAS_CRYPTO("xchacha20-arm");
  MODULE_ALIAS_CRYPTO("xchacha12");
  MODULE_ALIAS_CRYPTO("xchacha12-arm");
  #ifdef CONFIG_KERNEL_MODE_NEON
  MODULE_ALIAS_CRYPTO("chacha20-neon");
  MODULE_ALIAS_CRYPTO("xchacha20-neon");
  MODULE_ALIAS_CRYPTO("xchacha12-neon");
  #endif
  