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Sun, 04 Jan 2026 05:17:04 -0800 (PST) From: Menglong Dong X-Google-Original-From: Menglong Dong To: ast@kernel.org, eddyz87@gmail.com Cc: davem@davemloft.net, dsahern@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, 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, x86@kernel.org, hpa@zytor.com, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH bpf-next v2 1/2] bpf, x86: inline bpf_get_current_task() for x86_64 Date: Sun, 4 Jan 2026 21:16:34 +0800 Message-ID: <20260104131635.27621-2-dongml2@chinatelecom.cn> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260104131635.27621-1-dongml2@chinatelecom.cn> References: <20260104131635.27621-1-dongml2@chinatelecom.cn> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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] Signed-off-by: Menglong Dong --- v2: - check the variable type in emit_ldx_percpu_r0 with __verify_pcpu_ptr - remove the usage of const_current_task --- arch/x86/net/bpf_jit_comp.c | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index e3b1c4b1d550..f5ff7c77aad7 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -1300,6 +1300,25 @@ 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_ldx_percpu_r0(u8 **pprog, __force unsigned long ptr) +{ + u8 *prog = *pprog; + + /* mov rax, gs:[ptr] */ + EMIT2(0x65, 0x48); + EMIT2(0x8B, 0x04); + EMIT1(0x25); + EMIT((u32)ptr, 4); + + *pprog = prog; +} + +#define emit_ldx_percpu_r0(prog, variable) \ + do { \ + __verify_pcpu_ptr(&(variable)); \ + __emit_ldx_percpu_r0(&prog, (__force unsigned long)&(variable));\ + } while (0) + static int emit_atomic_rmw(u8 **pprog, u32 atomic_op, u32 dst_reg, u32 src_reg, s16 off, u8 bpf_size) { @@ -2441,6 +2460,12 @@ st: if (is_imm8(insn->off)) case BPF_JMP | BPF_CALL: { u8 *ip = image + addrs[i - 1]; + if (insn->src_reg == 0 && (insn->imm == BPF_FUNC_get_current_task || + insn->imm == BPF_FUNC_get_current_task_btf)) { + emit_ldx_percpu_r0(prog, current_task); + break; + } + func = (u8 *) __bpf_call_base + imm32; if (src_reg == BPF_PSEUDO_CALL && tail_call_reachable) { LOAD_TAIL_CALL_CNT_PTR(stack_depth); @@ -4082,3 +4107,14 @@ 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; + } +} -- 2.52.0