Linux kernel内核调用crypto算法的方法

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说明: 在无特别的说明下，本文讲述得都是armv8-aarch64体系、linux kernel 4.14 arm64软件环境！

1、定义一个算法

Linux Kernel中crypto算法的定义是以crypto_alg结构体来实现的

 {
	.cra_name		= "__ecb-aes-" MODE,
	.cra_driver_name	= "__driver-ecb-aes-" MODE,
	.cra_priority		= 0,
	.cra_flags		= CRYPTO_ALG_TYPE_BLKCIPHER |
				  CRYPTO_ALG_INTERNAL,
	.cra_blocksize		= AES_BLOCK_SIZE,
	.cra_ctxsize		= sizeof(struct crypto_aes_ctx),
	.cra_alignmask		= 7,
	.cra_type		= &crypto_blkcipher_type,
	.cra_module		= THIS_MODULE,
	.cra_blkcipher = {
		.min_keysize	= AES_MIN_KEY_SIZE,
		.max_keysize	= AES_MAX_KEY_SIZE,
		.ivsize		= 0,
		.setkey		= aes_setkey,
		.encrypt	= ecb_encrypt,
		.decrypt	= ecb_decrypt,
	},

2、注册crypto算法

注册一个算法(algapi.c)，crypto_alg_list链表维护着一些列crypto_alg结构体

int crypto_register_alg(struct crypto_alg *alg)
{
	struct crypto_larval *larval;
	int err;

	alg->cra_flags &= ~CRYPTO_ALG_DEAD;
	err = crypto_check_alg(alg);
	if (err)
		return err;

	down_write(&crypto_alg_sem);
	larval = __crypto_register_alg(alg);
	up_write(&crypto_alg_sem);

	if (IS_ERR(larval))
		return PTR_ERR(larval);

	crypto_wait_for_test(larval);
	return 0;
}
EXPORT_SYMBOL_GPL(crypto_register_alg);

3、crypto算法的查找

根据名字查询一个算法(api.c)，返回crypto_alg

struct crypto_alg *crypto_alg_lookup(const char *name, u32 type, u32 mask)
{
	struct crypto_alg *alg;

	down_read(&crypto_alg_sem);
	alg = __crypto_alg_lookup(name, type, mask);
	up_read(&crypto_alg_sem);

	return alg;
}
EXPORT_SYMBOL_GPL(crypto_alg_lookup);

4、算法调用的示例

（以tcrypt为例）
而在tcrypt.c的测试模块中，可根据名字，直接调用crypto_alg接口模块

		test_cipher_speed("ecb(aes)", ENCRYPT, sec, NULL, 0,
				speed_template_16_24_32);
		test_cipher_speed("ecb(aes)", DECRYPT, sec, NULL, 0,
				speed_template_16_24_32);
		test_cipher_speed("cbc(aes)", ENCRYPT, sec, NULL, 0,
				speed_template_16_24_32);
		test_cipher_speed("cbc(aes)", DECRYPT, sec, NULL, 0,
				speed_template_16_24_32);
		test_cipher_speed("lrw(aes)", ENCRYPT, sec, NULL, 0,
				speed_template_32_40_48);
		test_cipher_speed("lrw(aes)", DECRYPT, sec, NULL, 0,
				speed_template_32_40_48);
		test_cipher_speed("xts(aes)", ENCRYPT, sec, NULL, 0,
				speed_template_32_48_64);
		test_cipher_speed("xts(aes)", DECRYPT, sec, NULL, 0,
				speed_template_32_48_64);
		test_cipher_speed("ctr(aes)", ENCRYPT, sec, NULL, 0,
				speed_template_16_24_32);
		test_cipher_speed("ctr(aes)", DECRYPT, sec, NULL, 0,
				speed_template_16_24_32);