Re: options KUBSAN on UEFI machine

[Maxime Villard <max%m00nbsd.net@localhost>]

Le 27/07/2019 à 14:14, Kamil Rytarowski a écrit :
> On 25.07.2019 06:39, Masanobu SAITOH wrote:
> >   Hi.
> >
> >   I have two UEFI based machines. I noticed both of them didn't boot
> > with KUBSAN. After loading kernel, the video console is cleared,
> > the cursol went upper left and then hang. I couldn't see the
> > NetBSD's copyright message.
> >
> >   Is this known problem?
>
> I have got a local problem that I'm not successfully booting my amd64
> desktop with enabled i915 DRM KMS Framebuffer driver.

This could be that the KMS driver itself is generating a KUBSAN message.
So printf() gets called, it lands back in the KMS driver to print the
actual thing, which triggers again a KUBSAN message, so printf() gets
called again, and so on. It likely dies in a deadlock on whatever mutex
we take along the way.

In Masanobu's case, it is probably that the UEFI boot path triggers a
KUBSAN message, printf() gets called, but the console hasn't yet been
initialized, so it faults and dies there.

> There is also a similar problem with Kernel UBSan + Kernel ASan.
> Something breaks during early boot and needs investigation.

You should not use two kernel sanitizers at the same time.