From f7fe094b296f099f81f662e10a4fcac3bc4438f6 Mon Sep 17 00:00:00 2001
From: Vicent Marti <tanoku@gmail.com>
Date: Sun, 1 May 2016 12:54:51 +0200
Subject: [PATCH] lua: Implement "Hello world" USDT example

---
 examples/lua/usdt_ruby.lua | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)
 create mode 100755 examples/lua/usdt_ruby.lua

diff --git a/examples/lua/usdt_ruby.lua b/examples/lua/usdt_ruby.lua
new file mode 100755
index 0000000..9eb7d63
--- /dev/null
+++ b/examples/lua/usdt_ruby.lua
@@ -0,0 +1,42 @@
+#!/usr/bin/env bcc-lua
+--[[
+Copyright 2016 GitHub, Inc
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+]]
+
+local program = [[
+#include <uapi/linux/ptrace.h>
+int trace_method(struct pt_regs *ctx) {
+    char fn_name[128] = {};
+    bpf_usdt_readarg_p(method__entry_2, ctx, &fn_name, sizeof(fn_name));
+    bpf_trace_printk("%s(...)\n", &fn_name);
+    return 0;
+};
+]]
+
+return function(BPF, util)
+  if not arg[1] then
+    print("usage: rubysyms.lua PID")
+    return
+  end
+
+  local u = util.USDT:new{pid=tonumber(arg[1])}
+  u:enable_probe{probe="method__entry", fn_name="trace_method"}
+
+  local b = BPF:new{text=program, usdt=u}
+  local pipe = b:pipe()
+  while true do
+    print(pipe:trace_fields())
+  end
+end
-- 
2.7.4