On Fri, Aug 11, 2017 at 03:16:08PM -0700, Tyrel Datwyler wrote:
> On 08/11/2017 01:15 PM, Dan Carpenter wrote:
> > Hello Benjamin Herrenschmidt,
> >
> > This is a semi-automatic email about new static checker warnings.
> >
> > The patch 424de9c6e3f8: "powerpc/mm/radix: Avoid flushing the PWC on
> > every flush_tlb_range" from Jul 19, 2017, leads to the following
> > Smatch complaint:
> >
> > arch/powerpc/mm/tlb-radix.c:368 radix__flush_tlb_collapsed_pmd()
> > error: we previously assumed 'mm' could be null (see line 362)
> >
> > arch/powerpc/mm/tlb-radix.c
> > 361
> > 362 pid = mm ? mm->context.id : 0;
> > ^^
> > Check for NULL.
> >
> > 363 if (unlikely(pid == MMU_NO_CONTEXT))
> > 364 goto no_context;
> > 365
> > 366 /* 4k page size, just blow the world */
> > 367 if (PAGE_SIZE == 0x1000) {
> > 368 radix__flush_all_mm(mm);
> > ^^
> > Unchecked dereference.
>
> Appears to be a false positive. MMU_NO_CONTEXT I believe is defined as "0".
> So, maybe it
> would be clearer that we take the goto branch if this line read:
>
> 362 pid = mm ? mm->context.id : MMU_NO_CONTEXT;
>
Ah... This is because I'm compiling code for other arches in a "best
effort" way. It doesn't pull in the right headers so it doesn't know
the value of MMU_NO_CONTEXT. Otherwise it would read the code correctly
and not complain.
Sorry for that.
regards,
dan carpenter
