tracing/kprobes: Check the probe on unloaded module correctly

[ Upstream commit 59158ec4aef7d44be51a6f3e7e17fc64c32604eb ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>