Linux加密API SHA1

Question

我尝试使用Linux Crypto API在内核模块中计算sha1哈希，但是我找不到有关如何设置异步请求使用的分散列表的信息。另外，我应该如何等待异步操作完成？

static int plaintext_to_sha1(void) {

    struct scatterlist sg[8];
    struct crypto_ahash *tfm;
    struct ahash_request *req;

    char *plaintext = "TEST!\0";
    unsigned char *result = kmalloc(sizeof(unsigned char) * SHA1_LENGTH, GFP_KERNEL);
    unsigned int len = strlen(plaintext);

    tfm = crypto_alloc_ahash("sha1", 0, CRYPTO_ALG_ASYNC);
    if (IS_ERR(tfm)) {
        printk(KERN_ERR "tfm allocation failed\n");
        return -1;
    }

    /* ... set up the scatterlists ... */

    req = ahash_request_alloc(tfm, GFP_ATOMIC);
    if (!req) {
        printk(KERN_ERR "request allocation failed\n");
        return -1;
    }

    ahash_request_set_callback(req, 0, NULL, NULL);
    ahash_request_set_crypt(req, sg, result, 2);

    if (crypto_ahash_digest(req)) {
        printk(KERN_ERR "digest failed\n");
        return -1;
    }

    ahash_request_free(req);
    crypto_free_ahash(tfm);

    return 0;
}