From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f178.google.com (mail-pl1-f178.google.com [209.85.214.178]) (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 8F96B2581; Sun, 12 Jan 2025 06:45:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736664335; cv=none; b=Zg+VcQSQs5A2l34ak9PenZHXhCN/Ef72zoiW49Kf8UaA45E1nhp4NmJ+7FOS44GGEBPQ0PcHYwbLGKpQNv2Pn5MbFKjO4zsG82rfJbU8sbFGVX/O3BWrSd91aGVp+QO0pORwdo6ay+P3UTScERZ30r/YIDQJ8C+tnftFqWOk2CQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736664335; c=relaxed/simple; bh=yph9RWVp5+2gMT8lCxwb6Bk0YWFvTgCp/ifMNozXs1c=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=LJt1lUTStCWhrIX0LlS/uR/yMTMl3q+oJAoVIDv5rCGHEAufv4sQ93FEAD40WOaFl9u1KveVowuHYRcd+3/xE5h3jNXXxp/KJDWPvUIRwrPCPFjxkxFbfBWaMtmuf8Cujwd6+AnJ42Znb9i4A/1jdqsPVVNtJ4Afa5ag6Y5I6xg= 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=i3v6phMk; arc=none smtp.client-ip=209.85.214.178 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="i3v6phMk" Received: by mail-pl1-f178.google.com with SMTP id d9443c01a7336-2161eb95317so56113895ad.1; Sat, 11 Jan 2025 22:45:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1736664333; x=1737269133; 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=hHJiOiyymPmTO+pR9BFdPEH9iK2DFBm9/nkjMVjpj48=; b=i3v6phMkLmgChpcTmArcTEKVg1cjIYJp6W6YyNOEa/d7YkOIbZUT/5HPNOSDIRxqUe nArXpMDyVII8mg+FQuPqv2821RAZ+U9amODdlkV2cA4DsHp8PJ3ptFOEHiuPdReg8qrr kO/ec4cruy2BfXT0uzGAfJUoVbv30s0Q0468dPTkZDaXzD66PxlYS1/n0qOJzTUTaOwK +88MaJjp/GrEEPajxffj0gh4czS1wXgP3azhWS/NjVulzjKnep/bYdZDLtjkdMqeqiTz Vc8aiPBdxqjlK5Qa5w8e0Ep5hrbvZAO4YTsWBYC686Qf+csjGkzp2vp4Ci9aaqCDFhVh PESw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1736664333; x=1737269133; 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=hHJiOiyymPmTO+pR9BFdPEH9iK2DFBm9/nkjMVjpj48=; b=PSqbPci5siZtpkdD13xxVgz+oy+FJb1q7N+KpAPsYz6wPSY6K/t9vPgvMATOcAtxmX dhAi+gr3CJe+jaVzipK8PY4GGpACkWGiIx4B53ZotRm2ysZA5/t67FAiYXh/P+dkCdZy MlZnORyOcjR2CO+RizPQBvavYIYu+xnwR47HgxglRm1fZHwnLaNuG4C1cBRp11va7xj3 /3ZVSPQZkLEMbEkq47wlDcrupHgufnDU57mcIVFgXIUulDXNzvcCmvO5A6jSqlZmcppN dw/+KLvLRyW5SSLlGrMQiZtxNbzuqeiiriNzTBqpH+w181ed6TA4dzIrvKprtYqsEqtn DQrA== X-Forwarded-Encrypted: i=1; AJvYcCW1aigbm89O7VjM+yb3Nq0Cz/Xq9LFhOfk4LxXiU6i4HkHi6THsm6Lgk3UipUg103vEWD4zNO0=@vger.kernel.org X-Gm-Message-State: AOJu0YxofHOjUVi3fbkvxf7FW6ZzBtmeIEW24BtqSZxw38C5+h/z83TJ MStBTbPzzfdGAr25mEFzKSw4sHEJHXDWnXjtnpkXg2lGixb3W/+U X-Gm-Gg: ASbGncsuNRDEILiM/ZTCjVOsSvqE/bGKmzMINp3YHr15DQql9H2YOYSDVT56OhHXT1t RkQmq+eUDHYV8iYgh/WMq2L2/NPnMjomRZgTIByWIUTkAgOsh86EOR3HTktRorNfF34Wa97Gnu6 B4PEpolOrG/Q7eeo0u34Qkh3gAdkPzVj/2kNHhNeElbsL260l3H5EXk+BxiBiKi0bg/Cu0e5J0f yFQQjkPQUevjv/GJ2qmjy+QiCmwJjulHS0AJZ901Rs7fWEUL3XScIGT0HB1gEWOUbiVBTCiyDhz HYCpDUA= X-Google-Smtp-Source: AGHT+IG1lANNaN61ZaBr3NfIM4fnRkOGdOCCjstNr+lOM6C264BEFW9sRINYjXTNcJgXHth73N14LQ== X-Received: by 2002:a05:6a21:3993:b0:1db:e509:c0a8 with SMTP id adf61e73a8af0-1e88cfd3c7emr25137907637.21.1736664332824; Sat, 11 Jan 2025 22:45:32 -0800 (PST) Received: from localhost.localdomain ([180.159.118.224]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-72d4059485bsm3791166b3a.83.2025.01.11.22.45.24 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sat, 11 Jan 2025 22:45:32 -0800 (PST) From: Yafang Shao To: andrii@kernel.org, eddyz87@gmail.com, ast@kernel.org, daniel@iogearbox.net, 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, edumazet@google.com, dxu@dxuuu.xyz Cc: bpf@vger.kernel.org, netdev@vger.kernel.org, Yafang Shao , Jiri Olsa Subject: [RFC PATCH v2 1/2] libbpf: Add support for dynamic tracepoint Date: Sun, 12 Jan 2025 14:45:12 +0800 Message-Id: <20250112064513.883-2-laoar.shao@gmail.com> X-Mailer: git-send-email 2.37.1 (Apple Git-137.1) In-Reply-To: <20250112064513.883-1-laoar.shao@gmail.com> References: <20250112064513.883-1-laoar.shao@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Dynamic tracepoints can be created using debugfs, perf or similar tools. For example: $ perf probe -a 'tcp_listendrop sk' This command creates a new tracepoint under debugfs: $ ls /sys/kernel/debug/tracing/events/probe/tcp_listendrop/ enable filter format hist id trigger Notably, the probed function tcp_listendrop() is an inlined kernel function. Although this dynamic tracepoint appears as a tracepoint, it is internally implemented as a kprobe. Therefore, if we want to attach a bpf prog to it, the bpf prog must be loaded as a kprobe prog. The primary motivation for adding support for dynamic tracepoints is to simplify tracing of inlined kernel functions using BPF tools, such as bpftrace. By leveraging tools like perf, users can create a dynamic tracepoint for an inlined kernel function and then attach a BPF program to it. To achieve this, a new section, SEC("kprobe/SUBSYSTEM/PROBE"), has been introduced. Suggested-by: Jiri Olsa Signed-off-by: Yafang Shao Cc: Daniel Xu --- tools/lib/bpf/libbpf.c | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 66173ddb5a2d..23ea9272491b 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -11600,11 +11600,34 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog, return libbpf_err_ptr(err); } +/* A dynamic tracepoint: "kprobe/SUBSYSTEM/PROBE" */ +static int attach_dynamic_tracepoint(const struct bpf_program *prog, const char *func_name, + struct bpf_link **link) +{ + char *tp_subsys, *tp_name; + + tp_subsys = strdup(func_name); + if (!tp_subsys) + return -ENOMEM; + + tp_name = strchr(tp_subsys, '/'); + if (!tp_name) { + free(tp_subsys); + return -EINVAL; + } + + *tp_name = '\0'; + tp_name++; + *link = bpf_program__attach_tracepoint(prog, tp_subsys, tp_name); + free(tp_subsys); + return libbpf_get_error(*link); +} + static int attach_kprobe(const struct bpf_program *prog, long cookie, struct bpf_link **link) { DECLARE_LIBBPF_OPTS(bpf_kprobe_opts, opts); + const char *func_name, *dynamic_tp; unsigned long offset = 0; - const char *func_name; char *func; int n; @@ -11620,6 +11643,10 @@ static int attach_kprobe(const struct bpf_program *prog, long cookie, struct bpf else func_name = prog->sec_name + sizeof("kprobe/") - 1; + dynamic_tp = strchr(func_name, '/'); + if (dynamic_tp) + return attach_dynamic_tracepoint(prog, func_name, link); + n = sscanf(func_name, "%m[a-zA-Z0-9_.]+%li", &func, &offset); if (n < 1) { pr_warn("kprobe name is invalid: %s\n", func_name); -- 2.43.5