KLD and UID

[Chris Pressey]

On Tue, 16 Mar 2004 23:09:36 -0700
Simon Timms <timmssimon at shaw.ca> wrote:

> Hi there, I am playing around with kernel modules trying to learn
> something and hopefully not destroy my computer too badly.  Right now
> my goal is to print out the user id from an open() call.  I am basing
> my work around that found at http://www.nux-acid.org/src/open.c.  To
> that basic code I added (in the new_open method) 
>  
> printf("uid %u\n", p->p_ucred->cr_uid);
>  
> However this completely doesn't work and I end up crashing the kernel.
> I notice in other places people do things like
>  
> uid_t uid = p->p_cred->p_svuid;
>  
> however I don't see a p_cred member in the proc structure.  Is there
> something obvious I am missing here?  Complete code listing at
> http://simon.ma.cx/module.c.  Any additional comments/criticisms
> always appreciated.  
>  
> Thanks, Simon

What version of FreeBSD are you trying this on?

You might want to look at this thread on hackers@, it's very similar to
what you're trying to do, I think:

  http://docs.freebsd.org/cgi/mid.cgi?20040316163956.GD638

-Chris