Re: [PATCH 4/4] mm/kasan: make kasan=on|off take effect for all three modes

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

On Fri, Aug 08, 2025 at 09:08:35PM +0800, Baoquan He wrote:
> On 08/06/25 at 05:26pm, Lorenzo Stoakes wrote:
> > > I found mm-new build fails when CONFIG_KASAN is unset as below, and 'git
> > > bisect' points this patch.
> >
> > Yup just hit this + bisected here.
>
> Sorry for the trouble and thanks for reporting.

No worries!

>
> >
> > >
> > >       LD      .tmp_vmlinux1
> > >     ld: lib/stackdepot.o:(__jump_table+0x8): undefined reference to `kasan_flag_enabled'
> > >
> > > Since kasna_flag_enabled is defined in mm/kasan/common.c, I confirmed diff like
> > > below fixes this.  I think it may not be a correct fix though, since I didn't
> > > read this patchset thoroughly.
> > >
> > > diff --git a/include/linux/kasan-enabled.h b/include/linux/kasan-enabled.h
> > > index b5857e15ef14..a53d112b1020 100644
> > > --- a/include/linux/kasan-enabled.h
> > > +++ b/include/linux/kasan-enabled.h
> > > @@ -8,11 +8,22 @@ extern bool kasan_arg_disabled;
> > >
> > >  DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled);
> > >
> > > +#ifdef CONFIG_KASAN
> > > +
> >
> > Shouldn't we put this above the static key declaration?
> >
> > Feels like the whole header should be included really.
>
> You are right, kasan_flag_enabled should be included in CONFIG_KASAN
> ifdeffery scope.

Firstly I _LOVE_ the term 'ifdeffery scope'. Fantastic :)

>
> Since CONFIG_KASAN_HW_TAGS depends on CONFIG_KASAN, we may not need
> include below CONFIG_KASAN_HW_TAGS ifdeffery into CONFIG_KASAN ifdeffery
> scope. Not sure if this is incorrect.

Well I don't think CONFIG_KASAN_HW_TAGS is necessarily implied right? So these
should remain I think, just nested in CONFIG_KASAN, should be fine.

>
> Thanks a lot for checking this.

No problem! Just ran in to it while doing other stuff in mm-new :)

Cheers, Lorenzo