[PATCH v2 08/11] ring-buffer: Save text and data locations in mapped meta data

[Steven Rostedt]

From: "Steven Rostedt (Google)" <rost...@goodmis.org>

When a ring buffer is mapped to a specific address, save the address of a
text function and some data. This will be used to determine the delta
between the last boot and the current boot for pointers to functions as
well as to data.

Signed-off-by: Steven Rostedt (Google) <rost...@goodmis.org>
---
 kernel/trace/ring_buffer.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 6f19e7612472..c68695ae2749 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -45,6 +45,8 @@
 static void update_pages_handler(struct work_struct *work);
 
 struct ring_buffer_meta {
+       unsigned long   text_addr;
+       unsigned long   data_addr;
        unsigned long   first_buffer;
        unsigned long   head_buffer;
        unsigned long   commit_buffer;
@@ -539,6 +541,9 @@ struct trace_buffer {
        unsigned long                   range_addr_start;
        unsigned long                   range_addr_end;
 
+       long                            last_text_delta;
+       long                            last_data_delta;
+
        unsigned int                    subbuf_size;
        unsigned int                    subbuf_order;
        unsigned int                    max_data_size;
@@ -1827,10 +1832,15 @@ static void rb_meta_validate_events(struct 
ring_buffer_per_cpu *cpu_buffer)
        }
 }
 
+/* Used to calculate data delta */
+static char rb_data_ptr[] __initdata = "";
+
 static void rb_range_meta_init(struct trace_buffer *buffer, int nr_pages)
 {
        struct ring_buffer_meta *meta;
        unsigned long delta;
+       unsigned long this_text = (unsigned long)rb_range_meta_init;
+       unsigned long this_data = (unsigned long)rb_data_ptr;
        void *subbuf;
        int cpu;
        int i;
@@ -1847,6 +1857,10 @@ static void rb_range_meta_init(struct trace_buffer 
*buffer, int nr_pages)
                        meta->first_buffer += delta;
                        meta->head_buffer += delta;
                        meta->commit_buffer += delta;
+                       buffer->last_text_delta = this_text - meta->text_addr;
+                       buffer->last_data_delta = this_data - meta->data_addr;
+                       meta->text_addr = this_text;
+                       meta->data_addr = this_data;
                        continue;
                }
 
@@ -1863,6 +1877,8 @@ static void rb_range_meta_init(struct trace_buffer 
*buffer, int nr_pages)
                subbuf = rb_subbufs_from_meta(meta);
 
                meta->first_buffer = (unsigned long)subbuf;
+               meta->text_addr = this_text;
+               meta->data_addr = this_data;
 
                /*
                 * The buffers[] array holds the order of the sub-buffers
-- 
2.43.0