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

Song Liu
2025-04-03T18:33:21Z

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,
Song

> > >
> > > Hmm, I'm not sure how well BPF function attachment and live patching
> > > interact. Can you see if on x86 the live patch is actually updated when a
> > > BPF program is attached?