crypto_kpp_reqsize
crypto_kpp_reqsize(tfm_ctx->dh_tfm));
sizeof(struct kpp_request) + crypto_kpp_reqsize(ctx->dh.soft_tfm));
sizeof(struct kpp_request) + crypto_kpp_reqsize(ctx->ftfm));
req = kmalloc(sizeof(*req) + crypto_kpp_reqsize(tfm), gfp);