Re: [BUG?] ppc64le: fentry BPF not triggered after live patch (v6.14)

Hari Bathini
2025-10-02T19:45:59Z

On 07/04/25 1:52 pm, Hari Bathini wrote:
>
>
> On 04/04/25 12:03 am, Song Liu wrote:
>> On Thu, Apr 3, 2025 at 8:30 AM Naveen N Rao <naveen@kernel.org> wrote:
>> [...]
>>>
>>> We haven't addressed this particular interaction in the powerpc support
>>> for ftrace direct and BPF trampolines. Right now, live patching takes
>>> priority so we call the livepatch'ed function and skip further ftrace
>>> direct calls.
>>>
>>> I'm curious if this works on arm64 with which we share support for
>>> DYNAMIC_FTRACE_WITH_CALL_OPS.
>>
>> We still need to land [1] for arm64 to support livepatch. In a quick test
>> with [1], livepatch and bpf trampoline works together. I haven't looked
>> into the arm64 JIT code, so I am not sure whether all the corner cases
>> are properly handled.
>>
>> [1] https://lore.kernel.org/live-patching/20250320171559.3423224-1-
>> song@kernel.org/
>
> Thanks for checking this on arm64, Song.
> As Naveen pointed out, with out of line trampoline
> on ppc64le, there are a few things to sort out with
> regard to livepatch & BPF Trampoline interaction. Will
> try and take a stab at it soon.

Sorry, couldn't get to it sooner.
Posted the change that fixes livepatch & BPF trampoline
interaction in powerpc upstream now. Please take a look:

https://lore.kernel.org/all/20251002192755.86441-1-hbathini@linux.ibm.com/

- Hari