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>

1 files changed, 63 insertions, 1 deletions

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 6ea90c0e2c96..147491dccead 100644
--- 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 */