Re: [PATCH] Fix the j-core SOC build.

[Rich Felker <dalias@libc.org>]

On Sat, Oct 02, 2021 at 10:18:51PM -0400, Rich Felker wrote:
> On Sat, Oct 02, 2021 at 02:32:15PM -0500, Rob Landley wrote:
> > From: Rob Landley <rob@landley.net>
> > 
> > Commit b67177ecd956 broke the j-core SOC build with a link failure, because
> > mm/percpu.c function pcpu_post_unmap_tlb_flush() calls flush_tlb_kernel_range()
> > which is defined under #ifdef CONFIG_MMU.
> > 
> > Signed-off-by: Rob Landley <rob@landley.net>
> > ---
> > 
> >  arch/sh/kernel/smp.c |    5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/arch/sh/kernel/smp.c b/arch/sh/kernel/smp.c
> > index 65924d9ec245..3ec8f32aad85 100644
> > --- a/arch/sh/kernel/smp.c
> > +++ b/arch/sh/kernel/smp.c
> > @@ -468,4 +468,9 @@ void flush_tlb_one(unsigned long asid, unsigned long vaddr)
> >  	local_flush_tlb_one(asid, vaddr);
> >  }
> > 
> > +#else
> > +void flush_tlb_kernel_range(unsigned long start, unsigned long end)
> > +{
> > +	local_flush_tlb_all();
> > +}
> >  #endif
> 
> local_flush_tlb_all() is defined in arch/sh/mm/nommu.c as BUG(); so
> this is most likely wrong unless it just doesn't get called. I think
> there should probably be something at a very general level dummying
> out these functions/macros on nommu but I don't know where it should
> be.

I've looked into this some more, and while arch/arm does dummy its
equivalent functions out on nommu, arch/sh has always had them as
BUG(), and indeed it makes some sense to catch erroneous usage.
pcpu_post_unmap_tlb_flush should probably have the flush under #ifdef
CONFIG_MMU or something.

I've added the author of the commit that broke this to Cc in case he
has any thoughts.

Rich