Re: [PATCH bpf-next v1] bpf: Return -ENOTSUPP if callbacks are not allowed in non-JITed programs

[Tiezhu Yang]

On 01/03/2024 08:05 AM, John Fastabend wrote:
> Eduard Zingerman wrote:
> > On Mon, 2023-12-25 at 17:18 +0800, Tiezhu Yang wrote:
> > > If CONFIG_BPF_JIT_ALWAYS_ON is not set and bpf_jit_enable is 0, there
> > > exist 6 failed tests.

...

> > > Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
> > > ---
> > >  kernel/bpf/verifier.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > > index a376eb609c41..1c780a893284 100644
> > > --- a/kernel/bpf/verifier.c
> > > +++ b/kernel/bpf/verifier.c
> > > @@ -19069,7 +19069,7 @@ static int fixup_call_args(struct bpf_verifier_env *env)
> > >  			 * have to be rejected, since interpreter doesn't support them yet.
> > >  			 */
> > >  			verbose(env, "callbacks are not allowed in non-JITed programs\n");
> > > -			return -EINVAL;
> > > +			return -ENOTSUPP;
> > >  		}
> > >
> > >  		if (!bpf_pseudo_call(insn))
> >
> > I agree with this change, however I think that it should be consistent.
> > Quick and non-exhaustive grepping shows that there are 4 places where
> > "non-JITed" is used in error messages: in check_map_func_compatibility()
> > and in fixup_call_args().
> > All these places currently use -EINVAL and should be updated to -ENOTSUPP,
> > if this change gets a green light.
>
> My preference is to just leave them as is unless its a serious
> problem. In this case any userspace has likely already figured
> out how to handle these errors so I don't think there is much
> value in changing things.

I am not quite sure whether to ignore this patch, but the state of
this patch is "Changes Requested" [1], I guess I should send v2 as
Eduard suggested.

[1] 
https://patchwork.kernel.org/project/netdevbpf/patch/20231225091830.6094-1-yangtiezhu@xxxxxxxxxxx/

Thanks,
Tiezhu