linux-kernel

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20250422080419.322136-1-yangfeng59949@163.com>
Date: Tue, 22 Apr 2025 16:04:19 +0800
From: Feng Yang <yangfeng59949@....com>
To: alexei.starovoitov@...il.com
Cc: andrii@...nel.org,
	ast@...nel.org,
	bpf@...r.kernel.org,
	daniel@...earbox.net,
	eddyz87@...il.com,
	linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org,
	martin.lau@...ux.dev,
	netdev@...r.kernel.org,
	song@...nel.org,
	yangfeng59949@....com,
	yangfeng@...inos.cn,
	yonghong.song@...ux.dev
Subject: 

Subject: Re: [PATCH bpf-next] bpf: Remove bpf_get_smp_processor_id_proto

On Mon, 21 Apr 2025 18:53:07 -0700 Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:

> On Thu, Apr 17, 2025 at 8:41 PM Feng Yang <yangfeng59949@....com> wrote:
> >
> > From: Feng Yang <yangfeng@...inos.cn>
> >
> > All BPF programs either disable CPU preemption or CPU migration,
> > so the bpf_get_smp_processor_id_proto can be safely removed,
> > and the bpf_get_raw_smp_processor_id_proto in bpf_base_func_proto works perfectly.
> >
> > Suggested-by: Andrii Nakryiko <andrii.nakryiko@...il.com>
> > Signed-off-by: Feng Yang <yangfeng@...inos.cn>
> > ---
> >  include/linux/bpf.h      |  1 -
> >  kernel/bpf/core.c        |  1 -
> >  kernel/bpf/helpers.c     | 12 ------------
> >  kernel/trace/bpf_trace.c |  2 --
> >  net/core/filter.c        |  6 ------
> >  5 files changed, 22 deletions(-)
> >
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index 3f0cc89c0622..36e525141556 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -3316,7 +3316,6 @@ extern const struct bpf_func_proto bpf_map_peek_elem_proto;
> >  extern const struct bpf_func_proto bpf_map_lookup_percpu_elem_proto;
> >
> >  extern const struct bpf_func_proto bpf_get_prandom_u32_proto;
> > -extern const struct bpf_func_proto bpf_get_smp_processor_id_proto;
> >  extern const struct bpf_func_proto bpf_get_numa_node_id_proto;
> >  extern const struct bpf_func_proto bpf_tail_call_proto;
> >  extern const struct bpf_func_proto bpf_ktime_get_ns_proto;
> > diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> > index ba6b6118cf50..1ad41a16b86e 100644
> > --- a/kernel/bpf/core.c
> > +++ b/kernel/bpf/core.c
> > @@ -2943,7 +2943,6 @@ const struct bpf_func_proto bpf_spin_unlock_proto __weak;
> >  const struct bpf_func_proto bpf_jiffies64_proto __weak;
> >
> >  const struct bpf_func_proto bpf_get_prandom_u32_proto __weak;
> > -const struct bpf_func_proto bpf_get_smp_processor_id_proto __weak;
> >  const struct bpf_func_proto bpf_get_numa_node_id_proto __weak;
> >  const struct bpf_func_proto bpf_ktime_get_ns_proto __weak;
> >  const struct bpf_func_proto bpf_ktime_get_boot_ns_proto __weak;
> > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> > index e3a2662f4e33..2d2bfb2911f8 100644
> > --- a/kernel/bpf/helpers.c
> > +++ b/kernel/bpf/helpers.c
> > @@ -149,18 +149,6 @@ const struct bpf_func_proto bpf_get_prandom_u32_proto = {
> >         .ret_type       = RET_INTEGER,
> >  };
> >
> > -BPF_CALL_0(bpf_get_smp_processor_id)
> > -{
> > -       return smp_processor_id();
> > -}
> > -
> > -const struct bpf_func_proto bpf_get_smp_processor_id_proto = {
> > -       .func           = bpf_get_smp_processor_id,
> > -       .gpl_only       = false,
> > -       .ret_type       = RET_INTEGER,
> > -       .allow_fastcall = true,
> > -};
> > -
> 
> bpf_get_raw_smp_processor_id_proto doesn't have
> allow_fastcall = true
> 
> so this breaks tests.
> 
> Instead of removing BPF_CALL_0(bpf_get_smp_processor_id)
> we should probably remove BPF_CALL_0(bpf_get_raw_cpu_id)
> and adjust SKF_AD_OFF + SKF_AD_CPU case.
> I don't recall why raw_ version was used back in 2014.
> 

The following two seem to explain the reason:
https://lore.kernel.org/all/7103e2085afa29c006cd5b94a6e4a2ac83efc30d.1467106475.git.daniel@iogearbox.net/
https://lore.kernel.org/all/02fa71ebe1c560cad489967aa29c653b48932596.1474586162.git.daniel@iogearbox.net/