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

Menglong Dong posted 7 patches 2 months, 3 weeks ago
There is a newer version of this series
[PATCH RFC bpf-next 5/7] bpf: introduce bpf_arch_text_poke_type
Posted by Menglong Dong 2 months, 3 weeks ago 
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);
+
 int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
 		       void *addr1, void *addr2);
 
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index d595fe512498..608c636e6cf0 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -3135,6 +3135,16 @@ int __weak bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
 	return -ENOTSUPP;
 }
 
+int __weak bpf_arch_text_poke_type(void *ip, enum bpf_text_poke_type old_t,
+				   enum bpf_text_poke_type new_t, void *old_addr,
+				   void *new_addr)
+{
+	if (old_t == new_t)
+		return bpf_arch_text_poke(ip, old_t, old_addr, new_addr);
+
+	return -EOPNOTSUPP;
+}
+
 void * __weak bpf_arch_text_copy(void *dst, void *src, size_t len)
 {
 	return ERR_PTR(-ENOTSUPP);
-- 
2.51.2
Re: [PATCH RFC bpf-next 5/7] bpf: introduce bpf_arch_text_poke_type
Posted by Alexei Starovoitov 2 months, 3 weeks ago 
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);
Re: [PATCH RFC bpf-next 5/7] bpf: introduce bpf_arch_text_poke_type
Posted by Menglong Dong 2 months, 3 weeks ago 
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
Re: [PATCH RFC bpf-next 5/7] bpf: introduce bpf_arch_text_poke_type
Posted by bot+bpf-ci@kernel.org 2 months, 3 weeks ago 
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 8fb8c9bbd..975930e10 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -3712,6 +3712,10 @@ 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);
                                                          ^^^^^^^^^^^^

The header declaration uses parameter names addr1 and addr2, but the
implementation in kernel/bpf/core.c uses old_addr and new_addr. Should
these match? When developers implement arch-specific versions, they'll
see addr1/addr2 in the header but old_addr/new_addr in the weak default
implementation. The existing bpf_arch_text_poke() uses addr1/addr2, but
the x86 implementation of that function semantically treats them as
old_addr and new_addr. Would it be clearer to use old_addr/new_addr
consistently, or addr1/addr2 to match the existing function?

> +
>  int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
>  		       void *addr1, void *addr2);
>
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index ef4448f18..400eb70fd 100644
> --- a/kernel/bpf/core.c
> +++ b/kernel/bpf/core.c
> @@ -3156,6 +3156,16 @@ int __weak bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
>  	return -ENOTSUPP;
>  }
>
> +int __weak bpf_arch_text_poke_type(void *ip, enum bpf_text_poke_type old_t,
> +				   enum bpf_text_poke_type new_t, void *old_addr,
> +				   void *new_addr)
                                       ^^^^^^^^^^^^^^^^^^^^^^
> +{
> +	if (old_t == new_t)
> +		return bpf_arch_text_poke(ip, old_t, old_addr, new_addr);
> +
> +	return -EOPNOTSUPP;
> +}
> +
>  void * __weak bpf_arch_text_copy(void *dst, void *src, size_t len)
>  {
>  	return ERR_PTR(-ENOTSUPP);


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