FUNCTION_GRAPH_TRACER + UNWINDER_FRAME_POINTER broken on arm

[Linux regression tracking (Thorsten Leemhuis)]

On 25.05.24 09:59, Uwe Kleine-König wrote:
> 
> With FUNCTION_GRAPH_TRACER=y and CONFIG_UNWINDER_FRAME_POINTER=y I
> experience the following issue:
> 
> 	# echo function_graph > /sys/kernel/tracing/current_tracer
> 	[  303.812295] Kernel panic - not syncing: �e
> 	[  303.816738] ---[ end Kernel panic - not syncing: �e ]---
> 
> This reproduces reliably on v6.9 (on an i.MX25 based machine).
> 
> Bisection points on v5.18-rc1~150^2~7^2~6 ("ARM: ftrace: enable
> HAVE_FUNCTION_GRAPH_FP_TEST"). 
> 
> #regzbot introduced: 953f534a7ed6b725d4f101d2949393acc9262880

Thx for involving regzbot.

> I didn't try to understand the issue yet, but just disabled
> UNWINDER_FRAME_POINTER for now, which makes the problem disappear.
> Disabling CONFIG_DYNAMIC_FTRACE is another option to work around the
> problem.

TWIMC: I had a quick off-list chat with Uwe and pointed him to an
earlier thread about problems caused by that commit that might or might
contain an solution for the problem:
https://lore.kernel.org/all/d870c149-4363-43de-b0ea-7125dec5608e@broadcom.com/

He plans to look into this and report back.

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
--
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