record-btrace: add (reverse-)stepping support

Provide to_resume and to_wait target methods for the btrace record target
to allow reverse stepping and replay support.

Replay is limited in the sense that only stepping and source correlation
are supported.  We do not record data and thus can not show variables.

Non-stop mode is not working.  Do not allow record-btrace in non-stop mode.

2014-01-16  Markus Metzger  <markus.t.metzger@intel.com>

	* btrace.h (btrace_thread_flag): New.
	(struct btrace_thread_info) <flags>: New.
	* record-btrace.c (record_btrace_resume_thread)
	(record_btrace_find_thread_to_move, btrace_step_no_history)
	(btrace_step_stopped, record_btrace_start_replaying)
	(record_btrace_step_thread, record_btrace_decr_pc_after_break)
	(record_btrace_find_resume_thread): New.
	(record_btrace_resume, record_btrace_wait): Extend.
	(record_btrace_can_execute_reverse): New.
	(record_btrace_open): Fail in non-stop mode.
	(record_btrace_set_replay): Split into this, ...
	(record_btrace_stop_replaying): ... this, ...
	(record_btrace_clear_histories): ... and this.
	(init_record_btrace_ops): Init to_can_execute_reverse.
	* NEWS: Announce it.

testsuite/
	* gdb.btrace/delta.exp: Check reverse stepi.
	* gdb.btrace/tailcall.exp: Update.  Add stepping tests.
	* gdb.btrace/finish.exp: New.
	* gdb.btrace/next.exp: New.
	* gdb.btrace/nexti.exp: New.
	* gdb.btrace/record_goto.c: Add comments.
	* gdb.btrace/step.exp: New.
	* gdb.btrace/stepi.exp: New.
	* gdb.btrace/multi-thread-step.c: New.
	* gdb.btrace/multi-thread-step.exp: New.
	* gdb.btrace/rn-dl-bind.c: New.
	* gdb.btrace/rn-dl-bind.exp: New.
	* gdb.btrace/data.c: New.
	* gdb.btrace/data.exp: New.
	* gdb.btrace/Makefile.in (EXECUTABLES): Add new.

doc/
	* gdb.texinfo: Document limited reverse/replay support
	for target record-btrace.

1 files changed, 22 insertions, 0 deletions

diff --git a/gdb/btrace.h b/gdb/btrace.h
index 193f916..f83a80f 100644
--- a/gdb/btrace.h
+++ b/gdb/btrace.h
@@ -153,6 +153,25 @@ struct btrace_call_history
   struct btrace_call_iterator end;
 };
 
+/* Branch trace thread flags.  */
+enum btrace_thread_flag
+{
+  /* The thread is to be stepped forwards.  */
+  BTHR_STEP = (1 << 0),
+
+  /* The thread is to be stepped backwards.  */
+  BTHR_RSTEP = (1 << 1),
+
+  /* The thread is to be continued forwards.  */
+  BTHR_CONT = (1 << 2),
+
+  /* The thread is to be continued backwards.  */
+  BTHR_RCONT = (1 << 3),
+
+  /* The thread is to be moved.  */
+  BTHR_MOVE = (BTHR_STEP | BTHR_RSTEP | BTHR_CONT | BTHR_RCONT)
+};
+
 /* Branch trace information per thread.
 
    This represents the branch trace configuration as well as the entry point
@@ -182,6 +201,9 @@ struct btrace_thread_info
      becomes zero.  */
   int level;
 
+  /* A bit-vector of btrace_thread_flag.  */
+  enum btrace_thread_flag flags;
+
   /* The instruction history iterator.  */
   struct btrace_insn_history *insn_history;