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

Hari Bathini
2025-04-07T08:23:08Z

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.

Thanks
Hari