Re: [PATCH 13/14] x86/unwind/orc: Add more unwinder warnings

[Jann Horn]

On Thu, Mar 12, 2020 at 6:31 PM Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote:
> Make sure warnings are displayed for all error scenarios (except when
> encountering an empty unwind hint).
[...]
>         /* End-of-stack check for kernel threads: */
>         if (orc->sp_reg == ORC_REG_UNDEFINED) {
> -               if (!orc->end)
> +               if (!orc->end) {
> +                       /*
> +                        * This is reported as an error for the caller, but
> +                        * otherwise it isn't worth warning about.  In theory
> +                        * it can only happen when hitting UNWIND_HINT_EMPTY in
> +                        * entry code, close to a kernel exit point.
> +                        */
>                         goto err;

But UNWIND_HINT_EMPTY sets end=1, right? And this is the branch for
end==0. What am I missing?