Re: [patch v4 13/24] record-btrace, frame: supply target-specific unwinder

[Jan Kratochvil <jan.kratochvil@redhat.com>]

On Wed, 03 Jul 2013 11:14:23 +0200, Markus Metzger wrote:
> 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 e9c0801..cb1f3bb 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;
> @@ -844,6 +845,70 @@ 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.  */

That's OK.  Either remove the comment or:
  /* THIS_FRAME does not contain a reference to its thread.  */


> +  tp = find_thread_ptid (inferior_ptid);
> +  if (tp == NULL)
> +    return 0;

  gdb_assert (tp != NULL);


> +
> +  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
> @@ -874,6 +939,7 @@ 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