[patch v3 13/23] record-btrace, frame: supply target-specific unwinder

[Markus Metzger <markus dot t dot metzger at intel dot com>]

Supply a target-specific frame unwinder for the record-btrace target that does
not allow unwinding while replaying.

2013-02-11  Jan Kratochvil  <jan.kratochvil@redhat.com>
            Markus Metzger  <markus.t.metzger@intel.com>

gdb/
	* record-btrace.c: Include frame-unwind.h.
	(record_btrace_frame_unwind_stop_reason,
	record_btrace_frame_this_id, record_btrace_frame_prev_register,
	record_btrace_frame_sniffer, record_btrace_frame_unwind):
	New.
	(init_record_btrace_ops): Install it.


---
 gdb/record-btrace.c |   66 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 66 insertions(+), 0 deletions(-)

diff --git a/gdb/record-btrace.c b/gdb/record-btrace.c
index 651e0a0..da39411 100644
--- a/gdb/record-btrace.c
+++ b/gdb/record-btrace.c
@@ -33,6 +33,7 @@
 #include "symtab.h"
 #include "filenames.h"
 #include "regcache.h"
+#include "frame-unwind.h"
 
 /* The target_ops of record-btrace.  */
 static struct target_ops record_btrace_ops;
@@ -846,6 +847,70 @@ record_btrace_prepare_to_store (struct target_ops *ops,
       }
 }
 
+/* Implement stop_reason method for record_btrace_frame_unwind.  */
+
+static enum unwind_stop_reason
+record_btrace_frame_unwind_stop_reason (struct frame_info *this_frame,
+					void **this_cache)
+{
+  return UNWIND_UNAVAILABLE;
+}
+
+/* Implement this_id method for record_btrace_frame_unwind.  */
+
+static void
+record_btrace_frame_this_id (struct frame_info *this_frame, void **this_cache,
+			     struct frame_id *this_id)
+{
+  /* Leave there the outer_frame_id value.  */
+}
+
+/* Implement prev_register method for record_btrace_frame_unwind.  */
+
+static struct value *
+record_btrace_frame_prev_register (struct frame_info *this_frame,
+				   void **this_cache,
+				   int regnum)
+{
+  throw_error (NOT_AVAILABLE_ERROR,
+              _("Registers are not available in btrace record history"));
+}
+
+/* Implement sniffer method for record_btrace_frame_unwind.  */
+
+static int
+record_btrace_frame_sniffer (const struct frame_unwind *self,
+			     struct frame_info *this_frame,
+			     void **this_cache)
+{
+  struct thread_info *tp;
+  struct btrace_thread_info *btinfo;
+  struct btrace_insn_iterator *replay;
+
+  /* This doesn't seem right.  Yet, I don't see how I could get from a frame
+     to its thread.  */
+  tp = find_thread_ptid (inferior_ptid);
+  if (tp == NULL)
+    return 0;
+
+  return btrace_is_replaying (tp);
+}
+
+/* btrace recording does not store previous memory content, neither the stack
+   frames content.  Any unwinding would return errorneous results as the stack
+   contents no longer matches the changed PC value restored from history.
+   Therefore this unwinder reports any possibly unwound registers as
+   <unavailable>.  */
+
+static const struct frame_unwind record_btrace_frame_unwind =
+{
+  NORMAL_FRAME,
+  record_btrace_frame_unwind_stop_reason,
+  record_btrace_frame_this_id,
+  record_btrace_frame_prev_register,
+  NULL,
+  record_btrace_frame_sniffer
+};
 /* Initialize the record-btrace target ops.  */
 
 static void
@@ -876,6 +941,7 @@ init_record_btrace_ops (void)
   ops->to_fetch_registers = record_btrace_fetch_registers;
   ops->to_store_registers = record_btrace_store_registers;
   ops->to_prepare_to_store = record_btrace_prepare_to_store;
+  ops->to_get_unwinder = &record_btrace_frame_unwind;
   ops->to_stratum = record_stratum;
   ops->to_magic = OPS_MAGIC;
 }
-- 
1.7.1