Re: [PATCH RFC bpf-next 5/7] bpf: introduce bpf_arch_text_poke_type

Menglong Dong
2025-11-15T02:26:34Z

On Sat, Nov 15, 2025 at 2:42 AM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Fri, Nov 14, 2025 at 1:25 AM Menglong Dong <menglong8.dong@gmail.com> wrote:
> >
> > Introduce the function bpf_arch_text_poke_type(), which is able to specify
> > both the current and new opcode. If it is not implemented by the arch,
> > bpf_arch_text_poke() will be called directly if the current opcode is the
> > same as the new one. Otherwise, -EOPNOTSUPP will be returned.
> >
> > Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
> > ---
> > include/linux/bpf.h | 4 ++++
> > kernel/bpf/core.c | 10 ++++++++++
> > 2 files changed, 14 insertions(+)
> >
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index d65a71042aa3..aec7c65539f5 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -3711,6 +3711,10 @@ enum bpf_text_poke_type {
> > BPF_MOD_JUMP,
> > };
> >
> > +int bpf_arch_text_poke_type(void *ip, enum bpf_text_poke_type old_t,
> > + enum bpf_text_poke_type new_t, void *addr1,
> > + void *addr2);
> > +
>
> Instead of adding a new helper, I think, it's cleaner to change
> the existing bpf_arch_text_poke() across all archs in one patch,
> and also do:
>
> enum bpf_text_poke_type {
> + BPF_MOD_NOP,
> BPF_MOD_CALL,
> BPF_MOD_JUMP,
> };
>
> and use that instead of addr[12] = !NULL to indicate
> the transition.
>
> The callsites will be easier to read when they will look like:
> bpf_arch_text_poke(ip, BPF_MOD_CALL, BPF_MOD_CALL, old_addr, new_addr);
>
> bpf_arch_text_poke(ip, BPF_MOD_NOP, BPF_MOD_CALL, NULL, new_addr);
>
> bpf_arch_text_poke(ip, BPF_MOD_JMP, BPF_MOD_CALL, old_addr, new_addr);

Yeah, much clearer. The new helper also makes me feel a bit
dizzy.

Thanks!
Menglong Dong