tracing/kprobes: Init print_fmt for kprobe events

This is part of a patch set that removes the show_format method
in the ftrace event macros.

Add the print_fmt initialization to the kprobe events.
The print_fmt is still not used, but will be in the follow up
patches.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
LKML-Reference: <4B273D45.3080100@cn.fujitsu.com>
Acked-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 6ea90c0e2c96a89835216314f3b9f792161c49de..147491dccead84be5efbc7d99e3658be1103a10c 100644 (file)
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1250,6 +1250,62 @@ static int kretprobe_event_show_format(struct ftrace_event_call *call,
                                         ", REC->" FIELD_STRING_RETIP);
 }
 
+static int __set_print_fmt(struct trace_probe *tp, char *buf, int len)
+{
+       int i;
+       int pos = 0;
+
+       const char *fmt, *arg;
+
+       if (!probe_is_return(tp)) {
+               fmt = "(%lx)";
+               arg = "REC->" FIELD_STRING_IP;
+       } else {
+               fmt = "(%lx <- %lx)";
+               arg = "REC->" FIELD_STRING_FUNC ", REC->" FIELD_STRING_RETIP;
+       }
+
+       /* When len=0, we just calculate the needed length */
+#define LEN_OR_ZERO (len ? len - pos : 0)
+
+       pos += snprintf(buf + pos, LEN_OR_ZERO, "\"%s", fmt);
+
+       for (i = 0; i < tp->nr_args; i++) {
+               pos += snprintf(buf + pos, LEN_OR_ZERO, " %s=%%lx",
+                               tp->args[i].name);
+       }
+
+       pos += snprintf(buf + pos, LEN_OR_ZERO, "\", %s", arg);
+
+       for (i = 0; i < tp->nr_args; i++) {
+               pos += snprintf(buf + pos, LEN_OR_ZERO, ", REC->%s",
+                               tp->args[i].name);
+       }
+
+#undef LEN_OR_ZERO
+
+       /* return the length of print_fmt */
+       return pos;
+}
+
+static int set_print_fmt(struct trace_probe *tp)
+{
+       int len;
+       char *print_fmt;
+
+       /* First: called with 0 length to calculate the needed length */
+       len = __set_print_fmt(tp, NULL, 0);
+       print_fmt = kmalloc(len + 1, GFP_KERNEL);
+       if (!print_fmt)
+               return -ENOMEM;
+
+       /* Second: actually write the @print_fmt */
+       __set_print_fmt(tp, print_fmt, len + 1);
+       tp->call.print_fmt = print_fmt;
+
+       return 0;
+}
+
 #ifdef CONFIG_EVENT_PROFILE
 
 /* Kprobe profile handler */
@@ -1456,10 +1512,14 @@ static int register_probe_event(struct trace_probe *tp)
                call->show_format = kprobe_event_show_format;
                call->define_fields = kprobe_event_define_fields;
        }
+       if (set_print_fmt(tp) < 0)
+               return -ENOMEM;
        call->event = &tp->event;
        call->id = register_ftrace_event(&tp->event);
-       if (!call->id)
+       if (!call->id) {
+               kfree(call->print_fmt);
                return -ENODEV;
+       }
        call->enabled = 0;
        call->regfunc = probe_event_enable;
        call->unregfunc = probe_event_disable;
@@ -1472,6 +1532,7 @@ static int register_probe_event(struct trace_probe *tp)
        ret = trace_add_event_call(call);
        if (ret) {
                pr_info("Failed to register kprobe event: %s\n", call->name);
+               kfree(call->print_fmt);
                unregister_ftrace_event(&tp->event);
        }
        return ret;
@@ -1481,6 +1542,7 @@ static void unregister_probe_event(struct trace_probe *tp)
 {
        /* tp->event is unregistered in trace_remove_event_call() */
        trace_remove_event_call(&tp->call);
+       kfree(tp->call.print_fmt);
 }
 
 /* Make a debugfs interface for controling probe points */