trace/kprobes: Sanitize derived event names

When we derive event names, convert some expected symbols (such as ':'
used to specify module:name and '.' present in some symbols) into
underscores so that the event name is not rejected.

Before this patch:
    # echo 'p kobject_example:foo_store' > kprobe_events
    trace_kprobe: Failed to allocate trace_probe.(-22)
    -sh: write error: Invalid argument

After this patch:
    # echo 'p kobject_example:foo_store' > kprobe_events
    # cat kprobe_events
    p:kprobes/p_kobject_example_foo_store_0 kobject_example:foo_store

Link: http://lkml.kernel.org/r/66c189e09e71361aba91dd4a5bd146a1b62a7a51.1499453040.git.naveen.n.rao@linux.vnet.ibm.comAcked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/trace_kprobe.c

@@ -598,6 +598,14 @@ static struct notifier_block trace_kprobe_module_nb = {
 	.priority = 1	/* Invoked after kprobe module callback */
 };
 
+/* Convert certain expected symbols into '_' when generating event names */
+static inline void sanitize_event_name(char *name)
+{
+	while (*name++ != '\0')
+		if (*name == ':' || *name == '.')
+			*name = '_';
+}
+
 static int create_trace_kprobe(int argc, char **argv)
 {
 	/*
@@ -740,6 +748,7 @@ static int create_trace_kprobe(int argc, char **argv)
 		else
 			snprintf(buf, MAX_EVENT_NAME_LEN, "%c_0x%p",
 				 is_return ? 'r' : 'p', addr);
+		sanitize_event_name(buf);
 		event = buf;
 	}
 	tk = alloc_trace_kprobe(group, event, addr, symbol, offset, maxactive,