Re: [PATCH v4 8/8] unwind: arm64: Use sframe to unwind interrupt frames

[Jens Remus <jremus@linux.ibm.com>]

On 4/22/2026 12:52 AM, Dylan Hatch wrote:
> Add unwind_next_frame_sframe() function to unwind by sframe info if
> present. Use this method at exception boundaries, falling back to
> frame-pointer unwind only on failure. In such failure cases, the
> stacktrace is considered unreliable.
> 
> During normal unwind, prefer frame pointer unwind (for better
> performance) with sframe as a backup.
> 
> This change restores the LR behavior originally introduced in commit
> c2c6b27b5aa14fa2 ("arm64: stacktrace: unwind exception boundaries"),
> But later removed in commit 32ed1205682e ("arm64: stacktrace: Skip
> reporting LR at exception boundaries")
> 
> This can be done because the sframe data can be used to determine
> whether the LR is current for the PC value recovered from pt_regs at the
> exception boundary.
> 
> Signed-off-by: Weinan Liu <wnliu@google.com>
> Reviewed-by: Prasanna Kumar T S M <ptsm@linux.microsoft.com>
> Signed-off-by: Dylan Hatch <dylanbhatch@google.com>

Reviewed-by: Jens Remus <jremus@linux.ibm.com>

> ---
>  arch/arm64/include/asm/stacktrace/common.h |   6 +
>  arch/arm64/kernel/stacktrace.c             | 246 +++++++++++++++++++--
>  2 files changed, 232 insertions(+), 20 deletions(-)
Regards,
Jens
-- 
Jens Remus
Linux on Z Development (D3303)
jremus@de.ibm.com / jremus@linux.ibm.com

IBM Deutschland Research & Development GmbH; Vorsitzender des Aufsichtsrats: Wolfgang Wendt; Geschäftsführung: David Faller; Sitz der Gesellschaft: Ehningen; Registergericht: Amtsgericht Stuttgart, HRB 243294
IBM Data Privacy Statement: https://www.ibm.com/privacy/