From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264266AbUGIXcp (ORCPT ); Fri, 9 Jul 2004 19:32:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264278AbUGIXcp (ORCPT ); Fri, 9 Jul 2004 19:32:45 -0400 Received: from rproxy.gmail.com ([64.233.170.195]:59294 "HELO mproxy.gmail.com") by vger.kernel.org with SMTP id S264266AbUGIXcj convert rfc822-to-8bit (ORCPT ); Fri, 9 Jul 2004 19:32:39 -0400 Message-ID: Date: Fri, 9 Jul 2004 16:32:39 -0700 From: Qiuyu Zhang To: linux-kernel@vger.kernel.org Subject: Re: Strange about copy_from_user API Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Thx, I describe what I do and my code simply. I am try to do a module driver. So far I can insmod the module and config ip address etc. There is a existed queue in user space which is alloc by a user application. When I send a ping packet by the device I create, it will call dev->hard_start_xmit. In this function I need put the data into user space queue. Similarly, I also need read the data from queue when user put a data into queue. That's what I want to do. Code description: struct Queue { int read; int write; int length; char *data; }; At first, the module driver is inserted into kernel by calling insmod. And then user space application call a function to tell (register) module driver what is the pointer of the queue. The function be called by user application is as following int regQ2kernel( char *devname , char *queue){ struct ifrequ ifr; int sockfd; if((sockfd = socket(AF_INET,SOCK_DGRAM,0))<0）{ .... } strncpy(ifr.ifr_name, devname, sizeof(ifr.ifr_name)); ifr.ifr_data = pQueue; if((ret= ioctl(sockfd, SIOREGIFFLAGS, (int)&ifr))<0}{ } close(sockfd); return 1; } When the user application call the above function, the module driver in kernel can get the pointer of queue. And then I just store the pointer of queue. After I configure IP address and startup the module driver, I send a ping packet to the device. The packet arrived to the device correctly, then I need copy the data to queue in user space. Here, I have questions. 1) when I got the pointer of queue, can I access the item in the struct directly such as read, write etc? I try to do it. Sometimes it will crash OS. 2) Due to the above reason, I want to copy the struct of queue to kernel space and then access the item of the Queue. But I cannot get the correct content . static int usbModem_dev_xmit(struct sk_buff *skb, struct net_device *dev){ struct Queue *p = (struct Queue *)dev->priv; struct Queue kQueue; copy_from_user(&kQueue, *p, sizeof(struct Queue)); ...... // here , the data of kQueue is not the data in Queue in user space, I don't know why. } The strange thing is that when I use copy_from_user at ioctl function, everything is correct. How could figure it out? So far the quesiton is clear ? Thanks again. On Fri, 9 Jul 2004 17:57:57 -0400 (EDT), Richard B. Johnson wrote: > > > On Fri, 9 Jul 2004, Qiuyu Zhang wrote: > > > Hi all, > > I am working on writing a module driver. > > > > I am trying to use API copy_from_user to copy a bunch of memory from > > user space to kernel space. I write a ioctl function to register the > > pointer of the memory to kernel. And in the ioctl function I can use > > copy_from_user to get the correct data, but the strange thing is that > > when I use copy_from_user in other kernel function such as > > dev_hard_xmit function , I cannot > > get the correct result. I don't konw what the reason is . Thx. > > - > > Without looking at the code it's hard to figure out what you > may be doing. However, copy_from_user() and copy_to_user() may > not ever be executed with a spin-lock held. Generally, if > you need to put user data into kernel "things", you need > to buffer it, i.e., copy_from_user() into a kmalloc(ed) buffer, > then work with it in kernel space. > > Cheers, > Dick Johnson > Penguin : Linux version 2.4.26 on an i686 machine (5570.56 BogoMips). > Note 96.31% of all statistics are fiction. > >