问在系统调用实现中测试否定或失败案例

EN

struct new_struct
{
   void *p;  //set this pointer which you want to send...
};
    //from user-application...

    int main()
    {
       ....
       struct new_struct req_kernel;
       your_system_call_function(...,(void *)&req_kernel,...);
    }

    //this is inside your kernel...
         your_system_call(...,char __user optval,...)
         {
                .....
                struct new_struct req;
                if (copy_from_user(&req, optval, sizeof(req)))

                return -EFAULT;
                //now you have the address or pointer which you want in kernel with struct req...
        }