tracing/kprobes: Check the probe on unloaded module correctly

mhiramat · rostedt · commit 59158ec4aef7 · 2018-10-10T22:19:12.000-04:00
Current kprobe event doesn't checks correctly whether the given event is on unloaded module or not. It just checks the event has ":" in the name. That is not enough because if we define a probe on non-exist symbol on loaded module, it allows to define that (with warning message) To ensure it correctly, this searches the module name on loaded module list and only if there is not, it allows to define it. (this event will be available when the target module is loaded) Link: http://lkml.kernel.org/r/153547309528.26502.8300278470528281328.stgit@devbox Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
@@ -62,9 +62,23 @@ static nokprobe_inline bool trace_kprobe_within_module(struct trace_kprobe *tk,
 	return strncmp(mod->name, name, len) == 0 && name[len] == ':';
 }
 
-static nokprobe_inline bool trace_kprobe_is_on_module(struct trace_kprobe *tk)
+static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk)
 {
-	return !!strchr(trace_kprobe_symbol(tk), ':');
+	char *p;
+	bool ret;
+
+	if (!tk->symbol)
+		return false;
+	p = strchr(tk->symbol, ':');
+	if (!p)
+		return true;
+	*p = '\0';
+	mutex_lock(&module_mutex);
+	ret = !!find_module(tk->symbol);
+	mutex_unlock(&module_mutex);
+	*p = ':';
+
+	return ret;
 }
 
 static nokprobe_inline unsigned long trace_kprobe_nhit(struct trace_kprobe *tk)
@@ -374,19 +388,13 @@ static int __register_trace_kprobe(struct trace_kprobe *tk)
 	else
 		ret = register_kprobe(&tk->rp.kp);
 
-	if (ret == 0)
+	if (ret == 0) {
 		tk->tp.flags |= TP_FLAG_REGISTERED;
-	else {
-		if (ret == -ENOENT && trace_kprobe_is_on_module(tk)) {
-			pr_warn("This probe might be able to register after target module is loaded. Continue.\n");
-			ret = 0;
-		} else if (ret == -EILSEQ) {
-			pr_warn("Probing address(0x%p) is not an instruction boundary.\n",
-				tk->rp.kp.addr);
-			ret = -EINVAL;
-		}
+	} else if (ret == -EILSEQ) {
+		pr_warn("Probing address(0x%p) is not an instruction boundary.\n",
+			tk->rp.kp.addr);
+		ret = -EINVAL;
 	}
-
 	return ret;
 }
 
@@ -449,6 +457,11 @@ static int register_trace_kprobe(struct trace_kprobe *tk)
 
 	/* Register k*probe */
 	ret = __register_trace_kprobe(tk);
+	if (ret == -ENOENT && !trace_kprobe_module_exist(tk)) {
+		pr_warn("This probe might be able to register after target module is loaded. Continue.\n");
+		ret = 0;
+	}
+
 	if (ret < 0)
 		unregister_kprobe_event(tk);
 	else
