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

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Message-ID: <CAADnVQKUZsEvv64Y-U-hzCY-wc1iTfXTjhFhqG6Nq4fDsu_HsQ@mail.gmail.com>
Date: Fri, 9 Jan 2026 18:45:45 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Menglong Dong <menglong8.dong@...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 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.