bpf.lua: Implement `dump_func`

src/lua/bcc/bpf.lua

@@ -157,7 +157,8 @@ function Bpf:load_func(fn_name, prog_type)
     return self.funcs[fn_name]
   end
 
-  assert(libbcc.bpf_function_start(self.module, fn_name), "unknown program: "..fn_name)
+  assert(libbcc.bpf_function_start(self.module, fn_name) ~= nil,
+    "unknown program: "..fn_name)
 
   local fd = libbcc.bpf_prog_load(prog_type,
     libbcc.bpf_function_start(self.module, fn_name),
@@ -173,6 +174,14 @@ function Bpf:load_func(fn_name, prog_type)
   return fn
 end
 
+function Bpf:dump_func(fn_name)
+  local start = libbcc.bpf_function_start(self.module, fn_name)
+  assert(start ~= nil, "unknown program")
+
+  local len = libbcc.bpf_function_size(self.module, fn_name)
+  return ffi.string(start, tonumber(len))
+end
+
 function Bpf:attach_uprobe(args)
   Bpf.check_probe_quota(1)
 

tests/lua/test_dump.lua

+require("test_helper")
+
+function test_dump_func()
+  local raw = "\xb7\x00\x00\x00\x01\x00\x00\x00\x95\x00\x00\x00\x00\x00\x00\x00"
+  local b = BPF:new{text=[[int entry(void) { return 1; }]]}
+  assert_equals(b:dump_func("entry"), raw)
+end
+
+os.exit(LuaUnit.run())