Re: [RFC PATCH 0/2] perf: user stack dump on sparc64 needs an arch hook

[Stian Halseth]

Hi Magnus, thanks for the testing and feedback.

Almost done with a v2.

It has some minor changes based on the AI bot feedback, and my comments
to you below.


On Tue, 2026-09-22 at 19:04 +0200, Magnus Lindholm wrote:
> 
> Very nice series, thanks for working on this!
> 
> I built and booted the series on a sparc64 box and haven't
> noticed any regressions so far.
> 
> I also smoke-tested the new interfaces from 64-bit userspace with a
> small standalone C program using perf_event_open() and software
> cpu-clock events. The register-only, stack-only, and combined
> register/stack tests all passed. The test does not use tools/perf or
> request PERF_SAMPLE_CALLCHAIN. I haven't tested end-to-end DWARF
> unwinding yet.
> 
> I see that you plan to post the userspace changes once the hook is
> settled. Could you include the tools/perf support in the next
> revision,
> or post it as a follow-up or linked companion series? Having that
> available, along with a link to the matching elfutils changes, would
> make testing easier and let us exercise the intended DWARF unwinding
> use case directly.
Yes, I originally planned to post tools/perf after I got some feedback
on the first patches. Especially since it touches some generic code
that I'm not too familiar with, and I half expect that I have to
rewrite some of it based on maintainer feedback :-)

But since its "just" a RFC patch at this point, I guess I can post the
full series to allow end-to-end testing. 

I have mainly focused on the first patches, and the rest was done a bit
faster as a means to validate the "core" changes. It works (TM). I'm
looking through it now, but I probably make a second thorough review of
the entire final series, once the I know what changes I need to make.

I will publish and link to the elfutils changes as well.
> 
> Also, could you update the sparc entries from TODO to ok in:
> 
>   Documentation/features/perf/perf-regs/arch-support.txt
>   Documentation/features/perf/perf-stackdump/arch-support.txt
> 
> Those updates would fit naturally in patch 2 alongside the
> HAVE_PERF_REGS and HAVE_PERF_USER_STACK_DUMP selections.
Yes, agree.



-- 
Best regards
Stian Halseth
​

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