[PATCH v3 1/2] arm64: Implement arch_stack_walk_reliable

[Weinan Liu <wnliu@google.com>]

On Thu, Mar 20, 2025 at 10:16 AM Song Liu <song@kernel.org> wrote:
>
>  static __always_inline void
> @@ -230,8 +231,26 @@ kunwind_next_frame_record(struct kunwind_state *state)
>         new_fp = READ_ONCE(record->fp);
>         new_pc = READ_ONCE(record->lr);
>
> -       if (!new_fp && !new_pc)
> -               return kunwind_next_frame_record_meta(state);
> +       if (!new_fp && !new_pc) {
> +               int ret;
> +
> +               ret = kunwind_next_frame_record_meta(state);

The exception case kunwind_next_regs_pc() will return 0 when unwind success.
Should we return a different value for the success case of kunwind_next_regs_pc()?


> +               if (ret < 0) {
> +                       /*
> +                        * This covers two different conditions:
> +                        *  1. ret == -ENOENT, unwinding is done.
> +                        *  2. ret == -EINVAL, unwinding hit error.
> +                        */
> +                       return ret;
> +               }
> +               /*
> +                * Searching across exception boundaries. The stack is now
> +                * unreliable.
> +                */
> +               if (state->end_on_unreliable)
> +                       return -EINVAL;
> +               return 0;
> +       }