netdev - [RFC PATCH bpf-next 1/2] libbpf: Add support for dynamic tracepoint

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Message-Id: <20250105124403.991-2-laoar.shao@gmail.com>
Date: Sun,  5 Jan 2025 20:44:02 +0800
From: Yafang Shao <laoar.shao@...il.com>
To: andrii@...nel.org,
	eddyz87@...il.com,
	ast@...nel.org,
	daniel@...earbox.net,
	martin.lau@...ux.dev,
	song@...nel.org,
	yonghong.song@...ux.dev,
	john.fastabend@...il.com,
	kpsingh@...nel.org,
	sdf@...ichev.me,
	haoluo@...gle.com,
	jolsa@...nel.org,
	edumazet@...gle.com
Cc: bpf@...r.kernel.org,
	netdev@...r.kernel.org,
	Yafang Shao <laoar.shao@...il.com>
Subject: [RFC PATCH bpf-next 1/2] libbpf: Add support for dynamic tracepoint

Dynamic tracepoints can be created using debugfs. For example:

   echo 'p:myprobe kernel_clone args' >> /sys/kernel/debug/tracing/kprobe_events

This command creates a new tracepoint under debugfs:

  $ ls /sys/kernel/debug/tracing/events/kprobes/myprobe/
  enable  filter  format  hist  id  trigger

Although this dynamic tracepoint appears as a tracepoint, it is internally
implemented as a kprobe. However, it must be attached as a tracepoint to
function correctly in certain contexts.

This update adds support in libbpf for handling such tracepoints,
simplifying their usage and integration in BPF workflows.

Signed-off-by: Yafang Shao <laoar.shao@...il.com>
---
 tools/lib/bpf/libbpf.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 66173ddb5a2d..077bec761ebf 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -9504,6 +9504,7 @@ static const struct bpf_sec_def section_defs[] = {
 	SEC_DEF("struct_ops.s+",	STRUCT_OPS, 0, SEC_SLEEPABLE),
 	SEC_DEF("sk_lookup",		SK_LOOKUP, BPF_SK_LOOKUP, SEC_ATTACHABLE),
 	SEC_DEF("netfilter",		NETFILTER, BPF_NETFILTER, SEC_NONE),
+	SEC_DEF("dynamic_tp+",          KPROBE, 0, SEC_NONE, attach_tp),
 };
 
 int libbpf_register_prog_handler(const char *sec,
@@ -12500,6 +12501,8 @@ static int attach_tp(const struct bpf_program *prog, long cookie, struct bpf_lin
 	/* extract "tp/<category>/<name>" or "tracepoint/<category>/<name>" */
 	if (str_has_pfx(prog->sec_name, "tp/"))
 		tp_cat = sec_name + sizeof("tp/") - 1;
+	else if (str_has_pfx(prog->sec_name, "dynamic_tp/"))
+		tp_cat = sec_name + sizeof("dynamic_tp/") - 1;
 	else
 		tp_cat = sec_name + sizeof("tracepoint/") - 1;
 	tp_name = strchr(tp_cat, '/');
-- 
2.43.5