Re: [ACPI] PATCH-ACPI based CPU hotplug[2/6]-ACPI Eject

Alex Williamson
2004-09-21T18:10:52Z

On Tue, 2004-09-21 at 13:25 -0400, Theodore Ts'o wrote:
> On Mon, Sep 20, 2004 at 09:02:18PM -0600, Alex Williamson wrote:
> > > But, some AML methods are risky to be called directly from user space,
> > > Not only because the side effect of its execution, but also because
> > > it could trigger potential AML method bug or interpreter bug, or even
> > > architectural defect. All of these headache is due to the AML method
> > > is NOT intended for being used by userspace program.
> >
> > I've made an attempt to hide the most obvious dangerous methods, but
> > undoubtedly, there will be some. Why are we any more likely to hit an
> > AML method bug, interpreter bug or architectural bug by having a
> > userspace interface?
>
> As long as the userspace interfaces are only available to the root
> filesystem, I'm not sure it's worth it to hide any of the methods.
> It's added complexity, and in any case, root can do untold amounts of
> damage by writing to /dev/mem, trying to upload firmware to IDE
> drives, etc., etc., etc.

Yes, very true. I think the difference is that in my current
implementation, objects are evaluated on read. This makes it terribly
easy to do the wrong thing "Hmm, I wonder what that file does... oops".
Evaluating on write would set the bar a little higher, but still has
some of the same issues. In theory, I definitely agree, the interface
shouldn't need to hide anything. (I'm sure there are ACPI firmware
folks frightened by that idea) Thanks,

Alex

--
Alex Williamson HP Linux & Open Source Lab