Re: [PATCH] crypto: tcrypt: add option to not exit on success

Neil Horman
2009-05-13T11:08:49Z

On Wed, May 13, 2009 at 11:30:50AM +1000, Herbert Xu wrote:
> On Tue, May 12, 2009 at 08:37:27PM -0400, Neil Horman wrote:
> >
> > > Would there be any objections to dropping the noexit parameter
> > > entirely and just making its behavior the default? It would make
> > > all users regardless of fips mode notice failures more readily.
> > >
> > I think thats a fine idea. Theres no reason that a user of the tcrypt module
> > can't manually rmmod it when the testing is done. Doing it that way just seems
> > more sane to me to begin with anyway.
>
> No, tcrypt is only a relic for correctness testing. Its main
> purpose these days is for speed testing. Having to rmmod it
> is silly.
>
> There's really no need to load tcrypt for correctness testing
> anymore.
>

Not really sure I agree with the logic here. I agree that its pretty clear that
its major value is for quickly testing all the algorithms in a system, but
universally failing the loading of the module simply to save a few milliseconds
seems like a poor choice. In so doing you create an alias effect, as jarod
noted between a non-existent module and a module that failed to load. The
aliasing can be resolved, if you want to parse dmesg, but if speed is the issue
at hand, that parsing is a significant impact. If you allow the module to load
properly, then for the cost of an rmmod, you can tell simply from the exit code
of modprobe:
1) If the module was found
2) If the tests passed

And if the rmmod is simply to expensive for whatever reason, then for the cost
of a few k of ram taken up by the module, you can choose not to unload it.

Of course, if tcrypt is really as much of a relic as you say, perhaps that is an
argument for removing the module entirely. Perhaps the testmgr interface could
be exported to userspace and the tcrypt tests be packaged as a userspace suite.

Regards
Neil

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