FUNCTION_GRAPH_TRACER + UNWINDER_FRAME_POINTER broken on arm

[Arnd Bergmann]

On Mon, May 27, 2024, at 14:25, Uwe Kleine-König wrote:
> On Mon, May 27, 2024 at 11:18:32AM +0200, Arnd Bergmann wrote:
>> On Sat, May 25, 2024, at 09:59, Uwe Kleine-König wrote:
>> 
>> You added this in 4bf1fa5a34aa ("[ARM] 5613/1: implement
>> CALLER_ADDRESSx") 15 years ago, and it appears nobody ever
>> got around to finish the job for return_address() if I read
>> this correctly. Is this something we should finally add,
>> and then make the frame pointer unwinder specific to OABI
>> kernels?
>
> Oh, now you mention it I remember, but only on a high level and not the
> deep details. I guess nobody came around finishing it because having the
> dummy implementation for return_address doesn't hurt?
>
> Completing it would mean adding the numerous __notrace annotions??

I only know what I could see in the changelog, so that
is my best guess as well. It does look like there are
only a couple of CALLER_ADDR1 and CALLER_ADDR2 sites
in the tree, and CALLER_ADDR0 should already work
as intended even without an unwinder.

       Arnd