btrace, linux: add perf event buffer abstraction

Collect perf event buffer related fields from btrace_target_info into
a new struct perf_event_buffer.  Update functions that operated on the
buffer to take a struct perf_event_buffer pointer rather than a
btrace_target_info pointer.

2015-02-09  Markus Metzger  <markus.t.metzger@intel.com>

	* nat/linux-btrace.h (perf_event_buffer): New.
	(btrace_target_info) <buffer, size, data_head>: Replace with ...
	<bts>: ... this.
	* nat/linux-btrace.c (perf_event_header, perf_event_mmap_size)
	(perf_event_buffer_size, perf_event_buffer_begin)
	(perf_event_buffer_end, linux_btrace_has_changed): Removed.
	Updated users.
	(perf_event_new_data): New.

1 files changed, 25 insertions, 9 deletions

diff --git a/gdb/nat/linux-btrace.h b/gdb/nat/linux-btrace.h
index 24e06e8..602a571 100644
--- a/gdb/nat/linux-btrace.h
+++ b/gdb/nat/linux-btrace.h
@@ -32,6 +32,24 @@
 
 struct target_ops;
 
+#if HAVE_LINUX_PERF_EVENT_H
+/* A Linux perf event buffer.  */
+struct perf_event_buffer
+{
+  /* The mapped memory.  */
+  const uint8_t *mem;
+
+  /* The size of the mapped memory in bytes.  */
+  unsigned long long size;
+
+  /* A pointer to the data_head field for this buffer. */
+  volatile unsigned long long *data_head;
+
+  /* The data_head value from the last read.  */
+  unsigned long long last_head;
+};
+#endif /* HAVE_LINUX_PERF_EVENT_H */
+
 /* Branch trace target information per thread.  */
 struct btrace_target_info
 {
@@ -42,16 +60,14 @@ struct btrace_target_info
   /* The ptid of this thread.  */
   ptid_t ptid;
 
-  /* The mmap configuration mapping the branch trace perf_event buffer.
-
-     file      .. the file descriptor
-     buffer    .. the mmapped memory buffer
-     size      .. the buffer's size in pages without the configuration page
-     data_head .. the data head from the last read  */
+  /* The perf event file.  */
   int file;
-  void *buffer;
-  size_t size;
-  unsigned long data_head;
+
+  /* The perf event configuration page. */
+  volatile struct perf_event_mmap_page *header;
+
+  /* The BTS perf event buffer.  */
+  struct perf_event_buffer bts;
 #endif /* HAVE_LINUX_PERF_EVENT_H */
 
   /* The size of a pointer in bits for this thread.