[RFC PATCH 3/3] arm64: stacktrace: Implement reliable stacktrace

[Miroslav Benes]

On Mon, 12 Oct 2020, Mark Brown wrote:

> +int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry,
> +			     void *cookie, struct task_struct *task)
> +{
> +	struct stackframe frame;
> +
> +	if (task == current)
> +		start_backtrace(&frame,
> +				(unsigned long)__builtin_frame_address(0),
> +				(unsigned long)arch_stack_walk_reliable);
> +	else
> +		start_backtrace(&frame, thread_saved_fp(task),
> +				thread_saved_pc(task));
> +
> +	while (1) {
> +		int ret;
> +
> +#ifdef CONFIG_KPROBES
> +		/*
> +		 * Mark stacktraces with kretprobed functions on them
> +		 * as unreliable.
> +		 */
> +		if (frame.pc == (unsigned long)kretprobe_trampoline)
> +			return -EINVAL;
> +#endif

I think it would be nice to check if frame.pc is a valid text address here
before it is consumed next.

> +		if (!consume_entry(cookie, frame.pc))
> +			return -EINVAL;
> +		ret = unwind_frame(task, &frame);
> +		if (ret == -ENOENT)
> +			return 0;
> +		if (ret < 0)
> +			return ret;
> +	}
> +}

Miroslav