1 files changed, 55 insertions, 1 deletions

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 26069fa6b3b..d57a772981c 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -3,6 +3,9 @@
  *
  * Copyright (C) 2008 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
  *
+ *  - Added format output of fields of the trace point.
+ *    This was based off of work by Tom Zanussi <tzanussi@gmail.com>.
+ *
  */
 
 #include <linux/debugfs.h>
@@ -444,6 +447,42 @@ event_available_types_read(struct file *filp, char __user *ubuf, size_t cnt,
         return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
 }
 
+static ssize_t
+event_format_read(struct file *filp, char __user *ubuf, size_t cnt,
+                  loff_t *ppos)
+{
+        struct ftrace_event_call *call = filp->private_data;
+        struct trace_seq *s;
+        char *buf;
+        int r;
+
+        s = kmalloc(sizeof(*s), GFP_KERNEL);
+        if (!s)
+                return -ENOMEM;
+
+        trace_seq_init(s);
+
+        if (*ppos)
+                return 0;
+
+        r = call->show_format(s);
+        if (!r) {
+                /*
+                 * ug!  The format output is bigger than a PAGE!!
+                 */
+                buf = "FORMAT TOO BIG\n";
+                r = simple_read_from_buffer(ubuf, cnt, ppos,
+                                              buf, strlen(buf));
+                goto out;
+        }
+
+        r = simple_read_from_buffer(ubuf, cnt, ppos,
+                                    s->buffer, s->len);
+ out:
+        kfree(s);
+        return r;
+}
+
 static const struct seq_operations show_event_seq_ops = {
         .start = t_start,
         .next = t_next,
@@ -490,6 +529,11 @@ static const struct file_operations ftrace_available_types_fops = {
         .read = event_available_types_read,
 };
 
+static const struct file_operations ftrace_event_format_fops = {
+        .open = tracing_open_generic,
+        .read = event_format_read,
+};
+
 static struct dentry *event_trace_events_dir(void)
 {
         static struct dentry *d_tracer;
@@ -602,7 +646,17 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events)
                                     &ftrace_available_types_fops);
         if (!entry)
                 pr_warning("Could not create debugfs "
-                           "'%s/type' available_types\n", call->name);
+                           "'%s/available_types' entry\n", call->name);
+
+        /* A trace may not want to export its format */
+        if (!call->show_format)
+                return 0;
+
+        entry = debugfs_create_file("format", 0444, call->dir, call,
+                                    &ftrace_event_format_fops);
+        if (!entry)
+                pr_warning("Could not create debugfs "
+                           "'%s/format' entry\n", call->name);
 
         return 0;
 }