# Re: \[RFC PATCH v2 04/24\] unwind\_user: Flexible FP/RA recovery rules

- From: sashiko-bot@kernel.org
- Date: 2026-08-21 20:03:12 
- List: linux-trace-kernel
- Page: https://ratatoskr.run/linux-trace-kernel/2026/08/17446941
- Thread: https://ratatoskr.run/linux-trace-kernel/2026/08/17446896/t.md

```text
> To enable support for SFrame V3 flexible FDEs with a subsequent patch,
> add support for the following flexible frame pointer (FP) and return
> address (RA) recovery rules:
> 
>   FP/RA = *(CFA + offset)
>   FP/RA = register + offset
>   FP/RA = *(register + offset)
> 
> Note that FP/RA recovery rules that use arbitrary register contents are
> only valid when in the topmost frame, as their contents are otherwise
> unknown.
> 
> This also enables unwinding of user space for architectures, such as
> s390, that may save the frame pointer (FP) and/or return address (RA) in
> other registers, for instance when in a leaf function.
> 
> Reviewed-by: Indu Bhagat <redacted>
> Signed-off-by: Jens Remus <redacted>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260821195259.2688377-1-jremus@linux.ibm.com?part=4

```