3 files changed, 87 insertions, 0 deletions

diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index f0aa486d131c..fac8f1ac6f49 100644
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -166,6 +166,11 @@ void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data);
 int ring_buffer_read_page(struct ring_buffer *buffer, void **data_page,
                           size_t len, int cpu, int full);
 
+struct trace_seq;
+
+int ring_buffer_print_entry_header(struct trace_seq *s);
+int ring_buffer_print_page_header(struct trace_seq *s);
+
 enum ring_buffer_flags {
         RB_FL_OVERWRITE         = 1 << 0,
 };
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index f935bd5ec3e8..84a6055f37c9 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -22,6 +22,28 @@
 #include "trace.h"
 
 /*
+ * The ring buffer header is special. We must manually up keep it.
+ */
+int ring_buffer_print_entry_header(struct trace_seq *s)
+{
+        int ret;
+
+        ret = trace_seq_printf(s, "\ttype        :    2 bits\n");
+        ret = trace_seq_printf(s, "\tlen         :    3 bits\n");
+        ret = trace_seq_printf(s, "\ttime_delta  :   27 bits\n");
+        ret = trace_seq_printf(s, "\tarray       :   32 bits\n");
+        ret = trace_seq_printf(s, "\n");
+        ret = trace_seq_printf(s, "\tpadding     : type == %d\n",
+                               RINGBUF_TYPE_PADDING);
+        ret = trace_seq_printf(s, "\ttime_extend : type == %d\n",
+                               RINGBUF_TYPE_TIME_EXTEND);
+        ret = trace_seq_printf(s, "\tdata        : type == %d\n",
+                               RINGBUF_TYPE_DATA);
+
+        return ret;
+}
+
+/*
  * The ring buffer is made up of a list of pages. A separate list of pages is
  * allocated for each CPU. A writer may only write to a buffer that is
  * associated with the CPU it is currently executing on.  A reader may read
@@ -340,6 +362,28 @@ static inline int test_time_stamp(u64 delta)
 
 #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
 
+int ring_buffer_print_page_header(struct trace_seq *s)
+{
+        struct buffer_data_page field;
+        int ret;
+
+        ret = trace_seq_printf(s, "\tfield: u64 timestamp;\t"
+                               "offset:0;\tsize:%u;\n",
+                               (unsigned int)sizeof(field.time_stamp));
+
+        ret = trace_seq_printf(s, "\tfield: local_t commit;\t"
+                               "offset:%u;\tsize:%u;\n",
+                               (unsigned int)offsetof(typeof(field), commit),
+                               (unsigned int)sizeof(field.commit));
+
+        ret = trace_seq_printf(s, "\tfield: char data;\t"
+                               "offset:%u;\tsize:%u;\n",
+                               (unsigned int)offsetof(typeof(field), data),
+                               (unsigned int)BUF_PAGE_SIZE);
+
+        return ret;
+}
+
 /*
  * head_page == tail_page && head == tail then buffer is empty.
  */
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index f81d6eec4e43..7163a2bb021a 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -610,6 +610,30 @@ subsystem_filter_write(struct file *filp, const char __user *ubuf, size_t cnt,
         return cnt;
 }
 
+static ssize_t
+show_header(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos)
+{
+        int (*func)(struct trace_seq *s) = filp->private_data;
+        struct trace_seq *s;
+        int r;
+
+        if (*ppos)
+                return 0;
+
+        s = kmalloc(sizeof(*s), GFP_KERNEL);
+        if (!s)
+                return -ENOMEM;
+
+        trace_seq_init(s);
+
+        func(s);
+        r = simple_read_from_buffer(ubuf, cnt, ppos, s->buffer, s->len);
+
+        kfree(s);
+
+        return r;
+}
+
 static const struct seq_operations show_event_seq_ops = {
         .start = t_start,
         .next = t_next,
@@ -667,6 +691,11 @@ static const struct file_operations ftrace_subsystem_filter_fops = {
         .write = subsystem_filter_write,
 };
 
+static const struct file_operations ftrace_show_header_fops = {
+        .open = tracing_open_generic,
+        .read = show_header,
+};
+
 static struct dentry *event_trace_events_dir(void)
 {
         static struct dentry *d_tracer;
@@ -909,6 +938,15 @@ static __init int event_trace_init(void)
         if (!d_events)
                 return 0;
 
+        /* ring buffer internal formats */
+        trace_create_file("header_page", 0444, d_events,
+                          ring_buffer_print_page_header,
+                          &ftrace_show_header_fops);
+
+        trace_create_file("header_event", 0444, d_events,
+                          ring_buffer_print_entry_header,
+                          &ftrace_show_header_fops);
+
         for_each_event(call, __start_ftrace_events, __stop_ftrace_events) {
                 /* The linker may leave blanks */
                 if (!call->name)