From nobody Mon Feb 9 16:17:08 2026 Received: from mail-pl1-f193.google.com (mail-pl1-f193.google.com [209.85.214.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D255B2FD682 for ; Wed, 22 Oct 2025 08:02:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.193 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761120146; cv=none; b=X5HUh6AsdYxB73RELYqfR60f+D6Y32UD8Iuy0/zK0vWngPrkCun35XjuVLtbfAbnIQvIevIikl2rXKCRhwtBJAgo0qbtosvMpjVeG+zZTf5Hdjc+YcVulxuTcgBOs5SN7E9YLhs5y0xz1Xc99R5/5OrNhg4IBghxo8/XjKc1ltY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761120146; c=relaxed/simple; bh=MEFs+beI5cBBgDKfKyHyJzvZIINf6BRa4OCOzMkRRmc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=EtGU+Eku+T3/jrY0lSiUb/ypUdEYJwUyFY61q7YU0by6LkOE3PhfOdZ2+Qrjvxr0Kv8SmiZ1nmxylgb2WK5EqjvDQz09+CW6y4yqvMRJatWObyq60EBmNFYNrcysm4nbXZbhEXW8eeYBgiLpNS21qLkJnH2gaYPGfN6uKxezcrw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=XTs6Qcba; arc=none smtp.client-ip=209.85.214.193 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="XTs6Qcba" Received: by mail-pl1-f193.google.com with SMTP id d9443c01a7336-29226bc4bafso46990105ad.0 for ; Wed, 22 Oct 2025 01:02:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1761120140; x=1761724940; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=U0dIN4en5Nbyg37fgM4seNbI3NZS7JVL5G+Wmq/ATFM=; b=XTs6QcbaK1kyOTlGaNkKCHhCLwHvxno2yaCUVsidcyaX2a5yn/keuaeYN+EG1R3l6d fIhQfITJomjxWZq2cW2ZPcDFO4fT+w1qCM4cfU/DaXFP2/JOThHX71tdhG59CCf+URLv 0/TuEyCVvdbCz35DfpesngUL5slei2CSMBANj/RwXfuDCig+cra9Sk0iE9e6NlcHctZS WHFOTpmu3Kau8vBvqha/EicmdnyzhjD8FdFRCyuGPzhgtHJrQOBVPWdoor68QutiBef6 hPlUKxw9bS+MU/xeuYdS5JtrjJ+VN42MtOUTFojOwhVGfUkgWWbCaBF5tzLX456uPmJS l6Ag== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1761120140; x=1761724940; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=U0dIN4en5Nbyg37fgM4seNbI3NZS7JVL5G+Wmq/ATFM=; b=oNv4lGvn76g3TyK4nADoJ6aK6HPq/qH0RHcyOFYIyuwNUB3kLKOVB5b4FfFmZWr4cy iM7DLu7+hC+u8GujbXoiQ/bB7DpZljO3NBJbM2zBKXOlxusEW7UjPBWWiQ4wRNxjXS0D xF9h6xIXs2ec8OSNIVEzCPoixK6RsrxaStIjcfRqRyfrUiuTZ+aqHdaToq56IXgcUwsO tO+tOdenABHN2+KFWW2b2GYDEak3Qw7yTeq53Sdp4D1NwqibYXtyi5uxpoMXe7ViWgFu K5LnMY6JjpnBU/N2p0bytzgrBROhLIUBH6mar8Byf6+hFybX4StGpLlJtxIWghn9Hl/L H7yw== X-Forwarded-Encrypted: i=1; AJvYcCXtPdC60n3fBxtTg+U5icKyT/2LzwpvnOrH9QFYE32qUeAo2sFPwIYHXwtDHC1bXRXCvnEcM6LHmdyQf/0=@vger.kernel.org X-Gm-Message-State: AOJu0Yx6AHFAm31YaHTXlSKBF7fdjzOrxRGu5//C1fblzp2uhGHyD5rs zXYB2xouCiLFZMsCof4laGWNoG+pSDmZ7NO2znpial1vIlnOkc/lxg5Z X-Gm-Gg: ASbGncusHXvDs+MD7pVekL5utJIyhPFSIxR81VgaFVB1g9dSpn/B9pGpBAM1wzJ0P+B y7pvUTDgBTnkZNo2vI/uOH2Four5rDAbIpZAVpO2piq/5VE9V5wRXAO4EMKKUGAXvnBDEtHL/w/ TtINxMDHmKyg9uYTrJsizFbSEb8VyAp9/bJitQiQyATCEdyw6KHCN3MVIheV/Q2HULUOaRRdELi yV2eU8lqfL3d2eYZSxIARuhdVAxpc/9FBkBIqLTRvgVaP5tVogEVEusINNUi1pfh78Z66iNHnSU 2jbYHLJpEcl0YYp0UDCeB85OUFfBnNgOzZJs1pEFgJFpfPT+VZOkDVZF/mVvCkfLBqTzHRObnzQ 6ivPKvI4KAlveKvhVGOklcvssyLZ37vReXyr90E2oclO+3juTXfsBqwPUh1wLdvs6/PYEMGai X-Google-Smtp-Source: AGHT+IGIv/kxjl/Cr8AVdluhKxdEQMlUC/jiC9m9GjymD3dSUhssWXA9pvsnYvEYqz6+fWunATRtxw== X-Received: by 2002:a17:902:e88e:b0:24b:270e:56cb with SMTP id d9443c01a7336-290c9ce6427mr247961835ad.27.1761120140275; Wed, 22 Oct 2025 01:02:20 -0700 (PDT) Received: from 7950hx ([43.129.244.20]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-292471d7e41sm131947785ad.57.2025.10.22.01.02.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Oct 2025 01:02:19 -0700 (PDT) From: Menglong Dong X-Google-Original-From: Menglong Dong To: ast@kernel.org, jolsa@kernel.org Cc: daniel@iogearbox.net, john.fastabend@gmail.com, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, mattbobrowski@google.com, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, leon.hwang@linux.dev, jiang.biao@linux.dev, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: [PATCH bpf-next v2 02/10] bpf: add kfunc bpf_tracing_is_exit for TRACE_SESSION Date: Wed, 22 Oct 2025 16:01:51 +0800 Message-ID: <20251022080159.553805-3-dongml2@chinatelecom.cn> X-Mailer: git-send-email 2.51.1.dirty In-Reply-To: <20251022080159.553805-1-dongml2@chinatelecom.cn> References: <20251022080159.553805-1-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" If TRACE_SESSION exists, we will use extra 8-bytes in the stack of the trampoline to store the flags that we needed, and the 8-bytes lie after the return value, which means ctx[nr_args + 1]. And we will store the flag "is_exit" to the first bit of it. Introduce the kfunc bpf_tracing_is_exit(), which is used to tell if it is fexit currently. Meanwhile, inline it in the verifier. Signed-off-by: Menglong Dong Co-developed-by: Leon Hwang Signed-off-by: Leon Hwang --- v2: - store the session flags after return value, instead of before nr_args - inline the bpf_tracing_is_exit, as Jiri suggested --- kernel/bpf/verifier.c | 15 +++++++++++- kernel/trace/bpf_trace.c | 49 +++++++++++++++++++++++++++++++++++++--- 2 files changed, 60 insertions(+), 4 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 3ffdf2143f16..a4d0dd4440fd 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -12293,6 +12293,7 @@ enum special_kfunc_type { KF___bpf_trap, KF_bpf_task_work_schedule_signal, KF_bpf_task_work_schedule_resume, + KF_bpf_tracing_is_exit, }; =20 BTF_ID_LIST(special_kfunc_list) @@ -12365,6 +12366,7 @@ BTF_ID(func, bpf_res_spin_unlock_irqrestore) BTF_ID(func, __bpf_trap) BTF_ID(func, bpf_task_work_schedule_signal) BTF_ID(func, bpf_task_work_schedule_resume) +BTF_ID(func, bpf_tracing_is_exit) =20 static bool is_task_work_add_kfunc(u32 func_id) { @@ -12419,7 +12421,8 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env, struct bpf_reg_state *reg =3D ®s[regno]; bool arg_mem_size =3D false; =20 - if (meta->func_id =3D=3D special_kfunc_list[KF_bpf_cast_to_kern_ctx]) + if (meta->func_id =3D=3D special_kfunc_list[KF_bpf_cast_to_kern_ctx] || + meta->func_id =3D=3D special_kfunc_list[KF_bpf_tracing_is_exit]) return KF_ARG_PTR_TO_CTX; =20 /* In this function, we verify the kfunc's BTF as per the argument type, @@ -21994,6 +21997,16 @@ static int fixup_kfunc_call(struct bpf_verifier_en= v *env, struct bpf_insn *insn, desc->func_id =3D=3D special_kfunc_list[KF_bpf_rdonly_cast]) { insn_buf[0] =3D BPF_MOV64_REG(BPF_REG_0, BPF_REG_1); *cnt =3D 1; + } else if (desc->func_id =3D=3D special_kfunc_list[KF_bpf_tracing_is_exit= ]) { + /* Load nr_args from ctx - 8 */ + insn_buf[0] =3D BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, -8); + /* add rax, 1 */ + insn_buf[1] =3D BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, 1); + insn_buf[2] =3D BPF_ALU64_IMM(BPF_LSH, BPF_REG_0, 3); + insn_buf[3] =3D BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_1); + insn_buf[4] =3D BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 0); + insn_buf[5] =3D BPF_ALU64_IMM(BPF_AND, BPF_REG_0, 1); + *cnt =3D 6; } =20 if (env->insn_aux_data[insn_idx].arg_prog) { diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 4f87c16d915a..d0720d850621 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -3356,12 +3356,55 @@ static const struct btf_kfunc_id_set bpf_kprobe_mul= ti_kfunc_set =3D { .filter =3D bpf_kprobe_multi_filter, }; =20 -static int __init bpf_kprobe_multi_kfuncs_init(void) +__bpf_kfunc_start_defs(); + +__bpf_kfunc bool bpf_tracing_is_exit(void *ctx) +{ + /* This helper call is inlined by verifier. */ + u64 nr_args =3D ((u64 *)ctx)[-1]; + + /* + * ctx[nr_args + 1] is the session flags, and the last bit is + * is_exit. + */ + return ((u64 *)ctx)[nr_args + 1] & 1; +} + +__bpf_kfunc_end_defs(); + +BTF_KFUNCS_START(tracing_kfunc_set_ids) +BTF_ID_FLAGS(func, bpf_tracing_is_exit, KF_FASTCALL) +BTF_KFUNCS_END(tracing_kfunc_set_ids) + +static int bpf_tracing_filter(const struct bpf_prog *prog, u32 kfunc_id) { - return register_btf_kfunc_id_set(BPF_PROG_TYPE_KPROBE, &bpf_kprobe_multi_= kfunc_set); + if (!btf_id_set8_contains(&tracing_kfunc_set_ids, kfunc_id)) + return 0; + + if (prog->type !=3D BPF_PROG_TYPE_TRACING || + prog->expected_attach_type !=3D BPF_TRACE_SESSION) + return -EINVAL; + + return 0; +} + +static const struct btf_kfunc_id_set bpf_tracing_kfunc_set =3D { + .owner =3D THIS_MODULE, + .set =3D &tracing_kfunc_set_ids, + .filter =3D bpf_tracing_filter, +}; + +static int __init bpf_trace_kfuncs_init(void) +{ + int err =3D 0; + + err =3D err ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_KPROBE, &bpf_kprob= e_multi_kfunc_set); + err =3D err ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &bpf_trac= ing_kfunc_set); + + return err; } =20 -late_initcall(bpf_kprobe_multi_kfuncs_init); +late_initcall(bpf_trace_kfuncs_init); =20 typedef int (*copy_fn_t)(void *dst, const void *src, u32 size, struct task= _struct *tsk); =20 --=20 2.51.1.dirty