# Re: \[PATCH v12 02/14\] unwind\_user: Add frame pointer support

- From: Steven Rostedt \<rostedt@goodmis.org\>
- Date: 2025-07-02 23:50:24 
- List: linux-trace-kernel
- Page: https://ratatoskr.run/linux-trace-kernel/2025/07/3118509
- Thread: https://ratatoskr.run/linux-trace-kernel/2025/07/3114813/t.md

```text
On Tue, 1 Jul 2025 17:36:55 +0200
Jens Remus [ref] wrote:

> On s390 the prev_frame_sp may be equal to curr_frame_sp for the topmost
> frame, as long as the topmost function did not allocate any stack.  For
> instance when early in the prologue or when in a leaf function that does
> not require any stack space.  My s390 sframe support patches would
> therefore currently change above check to:
> 
> 	/* stack going in wrong direction? */
> 	if (sp <= state->sp - topmost)
> 		goto done;

How do you calculate "topmost" then?

Is it another field you add to "state"?

-- Steve
```