Re: Nice values for kernel modules

Eric W. Biederman (
25 Mar 2002 00:47:27 -0700

Andi Kleen <> writes:

> Alan Cox <> 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.


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