Re: [PATCH RFC bpf-next 1/2] bpf: propagate nullness information for reg to reg comparisons

[Eduard Zingerman <eddyz87@gmail.com>]

> On Tue, 2022-08-23 at 16:15 -0700, John Fastabend wrote:

Hi John,

Thank you for commenting!

> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index 2c1f8069f7b7..c48d34625bfd 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -472,6 +472,11 @@ static bool type_may_be_null(u32 type)
> >  	return type & PTR_MAYBE_NULL;
> >  }
> >  
> > +static bool type_is_pointer(enum bpf_reg_type type)
> > +{
> > +	return type != NOT_INIT && type != SCALAR_VALUE;
> > +}
> > +
> 
> Instead of having another helper is_pointer_value() could work here?
> Checking if we need NOT_INIT in that helper now.

Do you mean modifying the `__is_pointer_value` by adding a check
`reg->type != NOT_INIT`?

I tried this out and tests are passing, but __is_pointer_value /
is_pointer_value are used in a lot of places, seem to be a scary
change, to be honest.

Thanks,
Eduard