tracing/kprobes: Check the probe on unloaded module correctly

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
index 3faaadbddf54714375d283553543ac7e360a0c1c..4727a13824f0da17f60bd4b9be1214ff7f17b345 100644 (file)
--- 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