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Thu, 25 Dec 2025 02:45:14 -0800 (PST) Received: from 7940hx ([160.187.0.149]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-34e772ac06fsm9091379a91.11.2025.12.25.02.45.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 25 Dec 2025 02:45:14 -0800 (PST) From: Menglong Dong X-Google-Original-From: Menglong Dong To: ast@kernel.org Cc: davem@davemloft.net, dsahern@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, jiang.biao@linux.dev, x86@kernel.org, hpa@zytor.com, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH bpf-next] bpf, x86: inline bpf_get_current_task() for x86_64 Date: Thu, 25 Dec 2025 18:44:59 +0800 Message-ID: <20251225104459.204104-1-dongml2@chinatelecom.cn> X-Mailer: git-send-email 2.52.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Inline bpf_get_current_task() and bpf_get_current_task_btf() for x86_64 to obtain better performance. The instruction we use here is: 65 48 8B 04 25 [offset] // mov rax, gs:[offset] Not sure if there is any side effect here. Signed-off-by: Menglong Dong --- arch/x86/net/bpf_jit_comp.c | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index b69dc7194e2c..7f38481816f0 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -1300,6 +1300,19 @@ static void emit_st_r12(u8 **pprog, u32 size, u32 ds= t_reg, int off, int imm) emit_st_index(pprog, size, dst_reg, X86_REG_R12, off, imm); } =20 +static void emit_ldx_percpu_r0(u8 **pprog, const void __percpu *ptr) +{ + u8 *prog =3D *pprog; + + /* mov rax, gs:[offset] */ + EMIT2(0x65, 0x48); + EMIT2(0x8B, 0x04); + EMIT1(0x25); + EMIT((u32)(unsigned long)ptr, 4); + + *pprog =3D prog; +} + static int emit_atomic_rmw(u8 **pprog, u32 atomic_op, u32 dst_reg, u32 src_reg, s16 off, u8 bpf_size) { @@ -2435,6 +2448,15 @@ st: if (is_imm8(insn->off)) case BPF_JMP | BPF_CALL: { u8 *ip =3D image + addrs[i - 1]; =20 + if (insn->src_reg =3D=3D 0 && (insn->imm =3D=3D BPF_FUNC_get_current_ta= sk || + insn->imm =3D=3D BPF_FUNC_get_current_task_btf)) { + if (IS_ENABLED(CONFIG_USE_X86_SEG_SUPPORT)) + emit_ldx_percpu_r0(&prog, &const_current_task); + else + emit_ldx_percpu_r0(&prog, ¤t_task); + break; + } + func =3D (u8 *) __bpf_call_base + imm32; if (src_reg =3D=3D BPF_PSEUDO_CALL && tail_call_reachable) { LOAD_TAIL_CALL_CNT_PTR(stack_depth); @@ -4067,3 +4089,14 @@ bool bpf_jit_supports_timed_may_goto(void) { return true; } + +bool bpf_jit_inlines_helper_call(s32 imm) +{ + switch (imm) { + case BPF_FUNC_get_current_task: + case BPF_FUNC_get_current_task_btf: + return true; + default: + return false; + } +} --=20 2.52.0