netdev - Re: [PATCH bpf-next v8 06/11] bpf,x86: introduce emit_st_r0

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Message-ID: <1950001.tdWV9SEqCh@7950hx>
Date: Sat, 10 Jan 2026 11:40:29 +0800
From: Menglong Dong <menglong.dong@...ux.dev>
To: Menglong Dong <menglong8.dong@...il.com>,
 Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Alexei Starovoitov <ast@...nel.org>, Andrii Nakryiko <andrii@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>,
 Martin KaFai Lau <martin.lau@...ux.dev>, Eduard <eddyz87@...il.com>,
 Song Liu <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>,
 Jiri Olsa <jolsa@...nel.org>, "David S. Miller" <davem@...emloft.net>,
 David Ahern <dsahern@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, jiang.biao@...ux.dev,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 X86 ML <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
 bpf <bpf@...r.kernel.org>, Network Development <netdev@...r.kernel.org>,
 LKML <linux-kernel@...r.kernel.org>
Subject:
 Re: [PATCH bpf-next v8 06/11] bpf,x86: introduce emit_st_r0_imm64() for
 trampoline

On 2026/1/10 10:45, Alexei Starovoitov wrote:
> On Wed, Jan 7, 2026 at 6:26 PM Menglong Dong <menglong8.dong@...il.com> wrote:
> >
> > Introduce the helper emit_st_r0_imm64(), which is used to store a imm64 to
> > the stack with the help of r0.
> >
> > Signed-off-by: Menglong Dong <dongml2@...natelecom.cn>
> > ---
> >  arch/x86/net/bpf_jit_comp.c | 15 +++++++++++----
> >  1 file changed, 11 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
> > index e3b1c4b1d550..a87304161d45 100644
> > --- a/arch/x86/net/bpf_jit_comp.c
> > +++ b/arch/x86/net/bpf_jit_comp.c
> > @@ -1300,6 +1300,15 @@ static void emit_st_r12(u8 **pprog, u32 size, u32 dst_reg, int off, int imm)
> >         emit_st_index(pprog, size, dst_reg, X86_REG_R12, off, imm);
> >  }
> >
> > +static void emit_st_r0_imm64(u8 **pprog, u64 value, int off)
> > +{
> > +       /* mov rax, value
> > +        * mov QWORD PTR [rbp - off], rax
> > +        */
> > +       emit_mov_imm64(pprog, BPF_REG_0, value >> 32, (u32) value);
> > +       emit_stx(pprog, BPF_DW, BPF_REG_FP, BPF_REG_0, -off);
> > +}
> 
> The name is cryptic.
> How about emit_store_stack_imm64(pprog, stack_off, imm64) ?
> or emit_mov_stack_imm64.

emit_store_stack_imm64() sounds fine. I'll use it in the next version.

Thanks!
Menglong Dong

> 
>