4 files changed, 110 insertions, 1 deletions

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index cf6ba4181b14..e606633fb498 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -754,6 +754,7 @@ struct ftrace_event_call {
         int             (*raw_init)(void);
         int             (*raw_reg)(void);
         void            (*raw_unreg)(void);
+        int             (*show_format)(struct trace_seq *s);
 };
 
 void event_trace_printk(unsigned long ip, const char *fmt, ...);
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 26069fa6b3b0..d57a772981c1 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;
 }
diff --git a/kernel/trace/trace_events_stage_2.h b/kernel/trace/trace_events_stage_2.h
index dc79fe3a2ecb..3a80ea4e92cb 100644
--- a/kernel/trace/trace_events_stage_2.h
+++ b/kernel/trace/trace_events_stage_2.h
@@ -74,3 +74,55 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags)	\
 }
 
 #include <trace/trace_event_types.h>
+
+/*
+ * Setup the showing format of trace point.
+ *
+ * int
+ * ftrace_format_##call(struct trace_seq *s)
+ * {
+ *      struct ftrace_raw_##call field;
+ *      int ret;
+ *
+ *      ret = trace_seq_printf(s, #type " " #item ";"
+ *                             " size:%d; offset:%d;\n",
+ *                             sizeof(field.type),
+ *                             offsetof(struct ftrace_raw_##call,
+ *                                      item));
+ *
+ * }
+ */
+
+#undef TRACE_FIELD
+#define TRACE_FIELD(type, item, assign)                                 \
+        ret = trace_seq_printf(s, "\tfield:" #type " " #item ";\t"      \
+                               "offset:%lu;\tsize:%lu;\n",              \
+                               offsetof(typeof(field), item),           \
+                               sizeof(field.item));                     \
+        if (!ret)                                                       \
+                return 0;
+
+
+#undef TRACE_FIELD_SPECIAL
+#define TRACE_FIELD_SPECIAL(type_item, item, cmd)                       \
+        ret = trace_seq_printf(s, "\tfield special:" #type_item ";\t"   \
+                               "offset:%lu;\tsize:%lu;\n",              \
+                               offsetof(typeof(field), item),           \
+                               sizeof(field.item));                     \
+        if (!ret)                                                       \
+                return 0;
+
+#undef TRACE_EVENT_FORMAT
+#define TRACE_EVENT_FORMAT(call, proto, args, fmt, tstruct, tpfmt)      \
+int                                                                     \
+ftrace_format_##call(struct trace_seq *s)                               \
+{                                                                       \
+        struct ftrace_raw_##call field;                                 \
+        int ret;                                                        \
+                                                                        \
+        tstruct;                                                        \
+                                                                        \
+        return ret;                                                     \
+}
+
+#include <trace/trace_event_types.h>
diff --git a/kernel/trace/trace_events_stage_3.h b/kernel/trace/trace_events_stage_3.h
index 2ab65e958223..c62a4d2a5283 100644
--- a/kernel/trace/trace_events_stage_3.h
+++ b/kernel/trace/trace_events_stage_3.h
@@ -101,6 +101,7 @@
  *      .raw_init               = ftrace_raw_init_event_<call>,
  *      .raw_reg                = ftrace_raw_reg_event_<call>,
  *      .raw_unreg              = ftrace_raw_unreg_event_<call>,
+ *      .show_format            = ftrace_format_<call>,
  * }
  *
  */
@@ -230,4 +231,5 @@ __attribute__((section("_ftrace_events"))) event_##call = {		\
         .raw_init               = ftrace_raw_init_event_##call,         \
         .raw_reg                = ftrace_raw_reg_event_##call,          \
         .raw_unreg              = ftrace_raw_unreg_event_##call,        \
+        .show_format            = ftrace_format_##call,                 \
 }