RE: [RFC PATCH v8 3/4] arm64: Introduce stack trace reliability checks in the unwinder

["nobuta.keiya@fujitsu.com" <nobuta.keiya@fujitsu.com>]

Hi Madhavan,

> @@ -245,7 +271,36 @@ noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry,
>  		fp = thread_saved_fp(task);
>  		pc = thread_saved_pc(task);
>  	}
> -	unwind(consume_entry, cookie, task, fp, pc);
> +	unwind(consume_entry, cookie, task, fp, pc, false);
> +}
> +
> +/*
> + * arch_stack_walk_reliable() may not be used for livepatch until all of
> + * the reliability checks are in place in unwind_consume(). However,
> + * debug and test code can choose to use it even if all the checks are not
> + * in place.
> + */

I'm glad to see the long-awaited function :)

Does the above comment mean that this comment will be removed by
another patch series that about live patch enablement, instead of [PATCH 4/4]?

It seems to take time... But I start thinking about test code.

Thanks,
Keiya


> +noinline int notrace arch_stack_walk_reliable(stack_trace_consume_fn consume_fn,
> +					      void *cookie,
> +					      struct task_struct *task)
> +{
> +	unsigned long fp, pc;
> +
> +	if (!task)
> +		task = current;
> +
> +	if (task == current) {
> +		/* Skip arch_stack_walk_reliable() in the stack trace. */
> +		fp = (unsigned long)__builtin_frame_address(1);
> +		pc = (unsigned long)__builtin_return_address(0);
> +	} else {
> +		/* Caller guarantees that the task is not running. */
> +		fp = thread_saved_fp(task);
> +		pc = thread_saved_pc(task);
> +	}
> +	if (unwind(consume_fn, cookie, task, fp, pc, true))
> +		return 0;
> +	return -EINVAL;
>  }
> 
>  #endif
> --
> 2.25.1