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Mon, 12 Jan 2026 02:45:44 -0800 (PST) From: Menglong Dong X-Google-Original-From: Menglong Dong To: ast@kernel.org, eddyz87@gmail.com Cc: daniel@iogearbox.net, john.fastabend@gmail.com, andrii@kernel.org, martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH bpf-next v4 1/2] bpf, x86: inline bpf_get_current_task() for x86_64 Date: Mon, 12 Jan 2026 18:45:28 +0800 Message-ID: <20260112104529.224645-2-dongml2@chinatelecom.cn> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260112104529.224645-1-dongml2@chinatelecom.cn> References: <20260112104529.224645-1-dongml2@chinatelecom.cn> 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. In !CONFIG_SMP case, the percpu variable is just a normal variable, and we can read the current_task directly. Signed-off-by: Menglong Dong --- v4: - handle the !CONFIG_SMP case v3: - implement it in the verifier with BPF_MOV64_PERCPU_REG() instead of in x86_64 JIT. --- kernel/bpf/verifier.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 3d44c5d06623..12e99171afd8 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -17688,6 +17688,8 @@ static bool verifier_inlines_helper_call(struct bpf= _verifier_env *env, s32 imm) switch (imm) { #ifdef CONFIG_X86_64 case BPF_FUNC_get_smp_processor_id: + case BPF_FUNC_get_current_task_btf: + case BPF_FUNC_get_current_task: return env->prog->jit_requested && bpf_jit_supports_percpu_insn(); #endif default: @@ -23273,6 +23275,33 @@ static int do_misc_fixups(struct bpf_verifier_env = *env) insn =3D new_prog->insnsi + i + delta; goto next_insn; } + + /* Implement bpf_get_current_task() and bpf_get_current_task_btf() inlin= e. */ + if ((insn->imm =3D=3D BPF_FUNC_get_current_task || insn->imm =3D=3D BPF_= FUNC_get_current_task_btf) && + verifier_inlines_helper_call(env, insn->imm)) { +#ifdef CONFIG_SMP + insn_buf[0] =3D BPF_MOV64_IMM(BPF_REG_0, (u32)(unsigned long)¤t_t= ask); + insn_buf[1] =3D BPF_MOV64_PERCPU_REG(BPF_REG_0, BPF_REG_0); + insn_buf[2] =3D BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 0); +#else + struct bpf_insn ld_current_addr[2] =3D { + BPF_LD_IMM64(BPF_REG_0, (unsigned long)¤t_task) + }; + insn_buf[0] =3D ld_current_addr[0]; + insn_buf[1] =3D ld_current_addr[1]; + insn_buf[2] =3D BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 0); +#endif + cnt =3D 3; + + new_prog =3D bpf_patch_insn_data(env, i + delta, insn_buf, cnt); + if (!new_prog) + return -ENOMEM; + + delta +=3D cnt - 1; + env->prog =3D prog =3D new_prog; + insn =3D new_prog->insnsi + i + delta; + goto next_insn; + } #endif /* Implement bpf_get_func_arg inline. */ if (prog_type =3D=3D BPF_PROG_TYPE_TRACING && --=20 2.52.0