ioctl, copy string from user

[John Baldwin]

On Thursday 29 April 2010 1:52:45 pm Lukáš Czerner wrote:
> Hi,
> 
> I know that there are plenty of examples in the kernel code, but I
> just can not get it working, so maybe I am doing some stupid mistake
> I am not aware of. Please give me a hint if you can.
> 
> What I want to do is simply call the ioctl from the userspace with
> (char *) argument. Then, in kernel ioctl handling function copy the
> string argument into the kernel space. I have tried it various ways,
> everything without any success.
> 
> *** Userspace ***
> char name[MAXLEN];
> 
> strncpy(name, argv[1], MAXLEN);
> fprintf(stdout,"Name: %s\n",name);
> 
> if (ioctl(fd, MYIOCTL, name)) {

On BSD systems, ioctl() copies the data into the kernel for you ahead of time.  
What does the definition of MYIOCTL look like?

> And the second question. I have commented that I can allocate buffer
> dynamically, but I suppose that there will be some locks involved so
> I think I can not just use M_WAITOK, am I right ?

malloc() and free() acquire their own locks internally, you do not need to 
hold any locks to call them.

-- 
John Baldwin