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When kernel mode NEON was first introduced on arm64, the preserve and restore of the userland NEON state was completely unoptimized, and involved saving all registers on each call to kernel_neon_begin(), and restoring them on each call to kernel_neon_end(). For this reason, the NEON crypto code that was introduced at the time keeps the NEON enabled throughout the execution of the crypto API methods, which may include calls back into the crypto API that could result in memory allocation or other actions that we should avoid when running with preemption disabled. Since then, we have optimized the kernel mode NEON handling, which now restores lazily (upon return to userland), and so the preserve action is only costly the first time it is called after entering the kernel. So let's put the kernel_neon_begin() and kernel_neon_end() calls around the actual invocations of the NEON crypto code, and run the remainder of the code with kernel mode NEON disabled (and preemption enabled) Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
134 lines
3.4 KiB
C
134 lines
3.4 KiB
C
/*
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* ChaCha20 256-bit cipher algorithm, RFC7539, arm64 NEON functions
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*
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* Copyright (C) 2016 - 2017 Linaro, Ltd. <ard.biesheuvel@linaro.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* Based on:
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* ChaCha20 256-bit cipher algorithm, RFC7539, SIMD glue code
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*
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* Copyright (C) 2015 Martin Willi
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*/
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#include <crypto/algapi.h>
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#include <crypto/chacha20.h>
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#include <crypto/internal/skcipher.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <asm/hwcap.h>
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#include <asm/neon.h>
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#include <asm/simd.h>
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asmlinkage void chacha20_block_xor_neon(u32 *state, u8 *dst, const u8 *src);
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asmlinkage void chacha20_4block_xor_neon(u32 *state, u8 *dst, const u8 *src);
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static void chacha20_doneon(u32 *state, u8 *dst, const u8 *src,
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unsigned int bytes)
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{
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u8 buf[CHACHA20_BLOCK_SIZE];
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while (bytes >= CHACHA20_BLOCK_SIZE * 4) {
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kernel_neon_begin();
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chacha20_4block_xor_neon(state, dst, src);
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kernel_neon_end();
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bytes -= CHACHA20_BLOCK_SIZE * 4;
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src += CHACHA20_BLOCK_SIZE * 4;
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dst += CHACHA20_BLOCK_SIZE * 4;
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state[12] += 4;
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}
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if (!bytes)
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return;
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kernel_neon_begin();
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while (bytes >= CHACHA20_BLOCK_SIZE) {
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chacha20_block_xor_neon(state, dst, src);
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bytes -= CHACHA20_BLOCK_SIZE;
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src += CHACHA20_BLOCK_SIZE;
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dst += CHACHA20_BLOCK_SIZE;
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state[12]++;
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}
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if (bytes) {
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memcpy(buf, src, bytes);
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chacha20_block_xor_neon(state, buf, buf);
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memcpy(dst, buf, bytes);
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}
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kernel_neon_end();
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}
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static int chacha20_neon(struct skcipher_request *req)
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{
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struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
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struct chacha20_ctx *ctx = crypto_skcipher_ctx(tfm);
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struct skcipher_walk walk;
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u32 state[16];
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int err;
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if (!may_use_simd() || req->cryptlen <= CHACHA20_BLOCK_SIZE)
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return crypto_chacha20_crypt(req);
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err = skcipher_walk_virt(&walk, req, false);
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crypto_chacha20_init(state, ctx, walk.iv);
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while (walk.nbytes > 0) {
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unsigned int nbytes = walk.nbytes;
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if (nbytes < walk.total)
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nbytes = round_down(nbytes, walk.stride);
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chacha20_doneon(state, walk.dst.virt.addr, walk.src.virt.addr,
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nbytes);
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err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
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}
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return err;
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}
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static struct skcipher_alg alg = {
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.base.cra_name = "chacha20",
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.base.cra_driver_name = "chacha20-neon",
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.base.cra_priority = 300,
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.base.cra_blocksize = 1,
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.base.cra_ctxsize = sizeof(struct chacha20_ctx),
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.base.cra_module = THIS_MODULE,
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.min_keysize = CHACHA20_KEY_SIZE,
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.max_keysize = CHACHA20_KEY_SIZE,
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.ivsize = CHACHA20_IV_SIZE,
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.chunksize = CHACHA20_BLOCK_SIZE,
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.walksize = 4 * CHACHA20_BLOCK_SIZE,
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.setkey = crypto_chacha20_setkey,
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.encrypt = chacha20_neon,
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.decrypt = chacha20_neon,
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};
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static int __init chacha20_simd_mod_init(void)
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{
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if (!(elf_hwcap & HWCAP_ASIMD))
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return -ENODEV;
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return crypto_register_skcipher(&alg);
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}
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static void __exit chacha20_simd_mod_fini(void)
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{
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crypto_unregister_skcipher(&alg);
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}
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module_init(chacha20_simd_mod_init);
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module_exit(chacha20_simd_mod_fini);
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MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
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MODULE_LICENSE("GPL v2");
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MODULE_ALIAS_CRYPTO("chacha20");
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