Re: [PATCH RFC 0/8] kasan: hardware tag-based mode for production use on arm64

[Marco Elver]

On Fri, 16 Oct 2020 at 15:17, 'Andrey Konovalov' via kasan-dev
<kasan-dev@xxxxxxxxxxxxxxxx> wrote:
[...]
> > > The intention with this kind of a high level switch is to hide the
> > > implementation details. Arguably, we could add multiple switches that allow
> > > to separately control each KASAN or MTE feature, but I'm not sure there's
> > > much value in that.
> > >
> > > Does this make sense? Any preference regarding the name of the parameter
> > > and its values?
> >
> > KASAN itself used to be a debugging tool only. So introducing an "on"
> > mode which no longer follows this convention may be confusing.
>
> Yeah, perhaps "on" is not the best name here.
>
> > Instead, maybe the following might be less confusing:
> >
> > "full" - current "debug", normal KASAN, all debugging help available.
> > "opt" - current "on", optimized mode for production.
>
> How about "prod" here?

SGTM.

[...]
>
> > > Should we somehow control whether to panic the kernel on a tag fault?
> > > Another boot time parameter perhaps?
> >
> > It already respects panic_on_warn, correct?
>
> Yes, but Android is unlikely to enable panic_on_warn as they have
> warnings happening all over. AFAIR Pixel 3/4 kernels actually have a
> custom patch that enables kernel panic for KASAN crashes specifically
> (even though they don't obviously use KASAN in production), and I
> think it's better to provide a similar facility upstream. Maybe call
> it panic_on_kasan or something?

Best would be if kasan= can take another option, e.g.
"kasan=prod,panic". I think you can change the strcmp() to a
str_has_prefix() for the checks for full/prod/on/off, and then check
if what comes after it is ",panic".

Thanks,
-- Marco