Re: Nice values for kernel modules

[ebiederm@xmission.com (Eric W. Biederman)]

Andi Kleen <ak@suse.de> writes:

> Alan Cox <alan@lxorguk.ukuu.org.uk> writes:
> 
> > > Ability to bypass the stupid commercial time-locked licences (at some time
> > > wordperfect demo was locked like that and my timetravel module turned a
> > > demo into full product -- users were happy, at least according to emails I
> > > received :)
> > 
> > Not any more. Under the DMCA your time travel module probably makes you
> > a fugtive from US justice 8)
> > 
> > In general though calling into the syscall table by hand is a bad move. If
> > the function you are calling is generically useful then its much better to
> > work out whether the real function should be exported.
> 
> Some programs depends on tapping the system call table. For example private
> ice and oprofile do this for execve and other calls to know when a new 
> process is started. It would be possible to add function pointers to all these
> functions, but just tapping the system call table actually looks cleaner
> to me. 
> 
> [yes, the approach has module unload races, but these modules tend to just 
> make themselves not unloadable]

What is wrong with using ptrace?  That should already give you a hook into
every syscall.

Eric