[RFA] Reverse debugging, part 2/3: core interface

[Michael Snyder <msnyder at redhat dot com>]

This is the core gdb part of reverse debugging: mainly
the infrun/infcmd part.

It depends on part 1 (the target interface) only in that
it expects the method target_get_execution_direction to exist.

It doesn't depend on part 3 (the user interface) at all,
so they can be reviewed, accepted or rejected independantly.

The important parts to this patch are as described in the
changelog, where it adds handling for reverse execution in
various contexts (such as stepping into a function).

2006-03-31  Michael Snyder  <msnyder@redhat.com>

	Execution interface for reverse execution.
	* breakpoint.c (breakpoint_silence): New function.
	* breakpoint.h (breakpoint_silence): Export.
	* infcmd.c (finish_command): Check for reverse exec direction.
	(finish_backward): New function, handle finish cmd in reverse.
	* infrun.c (enum inferior_stop_reason): Add NO_HISTORY reason.
	(handle_inferior_event): Handle TARGET_WAITKIND_NO_HISTORY.
	Handle stepping over a function call in reverse.
	Handle stepping thru a line range in reverse.
	Handle setting a step-resume breakpoint in reverse.
	Handle stepping into a function in reverse.
	Handle stepping between line ranges in reverse.
	(print_stop_reason): Print reason for NO_HISTORY.

Index: breakpoint.c
===================================================================
RCS file: /cvs/src/src/gdb/breakpoint.c,v
retrieving revision 1.223
diff -p -r1.223 breakpoint.c
*** breakpoint.c	9 Feb 2006 11:24:46 -0000	1.223
--- breakpoint.c	31 Mar 2006 21:48:02 -0000
*************** breakpoint_clear_ignore_counts (void)
*** 7326,7331 ****
--- 7326,7338 ----
      b->ignore_count = 0;
  }
  
+ void
+ breakpoint_silence (struct breakpoint *b)
+ {
+   /* Silence the breakpoint.  */
+   b->silent = 1;
+ }
+ 
  /* Command to set ignore-count of breakpoint N to COUNT.  */
  
  static void
Index: breakpoint.h
===================================================================
RCS file: /cvs/src/src/gdb/breakpoint.h,v
retrieving revision 1.36
diff -p -r1.36 breakpoint.h
*** breakpoint.h	17 Dec 2005 22:33:59 -0000	1.36
--- breakpoint.h	31 Mar 2006 21:48:03 -0000
*************** extern int deprecated_exception_catchpoi
*** 805,808 ****
--- 805,811 ----
     reinitialized -- e.g. when program is re-run.  */
  extern int deprecated_exception_support_initialized;
  
+ /* Tell a breakpoint to be quiet.  */
+ extern void breakpoint_silence (struct breakpoint *);
+ 
  #endif /* !defined (BREAKPOINT_H) */
Index: infcmd.c
===================================================================
RCS file: /cvs/src/src/gdb/infcmd.c,v
retrieving revision 1.144
diff -p -r1.144 infcmd.c
*** infcmd.c	27 Jan 2006 20:05:27 -0000	1.144
--- infcmd.c	31 Mar 2006 21:48:04 -0000
*************** finish_command_continuation (struct cont
*** 1251,1256 ****
--- 1251,1258 ----
  /* "finish": Set a temporary breakpoint at the place the selected
     frame will return to, then continue.  */
  
+ static void finish_backwards (struct symbol *);
+ 
  static void
  finish_command (char *arg, int from_tty)
  {
*************** finish_command (char *arg, int from_tty)
*** 1293,1308 ****
  
    clear_proceed_status ();
  
-   sal = find_pc_line (get_frame_pc (frame), 0);
-   sal.pc = get_frame_pc (frame);
- 
-   breakpoint = set_momentary_breakpoint (sal, get_frame_id (frame), bp_finish);
- 
-   if (!target_can_async_p ())
-     old_chain = make_cleanup_delete_breakpoint (breakpoint);
-   else
-     old_chain = make_exec_cleanup_delete_breakpoint (breakpoint);
- 
    /* Find the function we will return from.  */
  
    function = find_pc_function (get_frame_pc (deprecated_selected_frame));
--- 1295,1300 ----
*************** finish_command (char *arg, int from_tty)
*** 1311,1320 ****
       source.  */
    if (from_tty)
      {
!       printf_filtered (_("Run till exit from "));
        print_stack_frame (get_selected_frame (NULL), 1, LOCATION);
      }
  
    /* If running asynchronously and the target support asynchronous
       execution, set things up for the rest of the finish command to be
       completed later on, when gdb has detected that the target has
--- 1303,1333 ----
       source.  */
    if (from_tty)
      {
!       if (target_get_execution_direction () == EXEC_REVERSE)
! 	printf_filtered ("Run back to call of ");
!       else
! 	printf_filtered ("Run till exit from ");
! 
        print_stack_frame (get_selected_frame (NULL), 1, LOCATION);
      }
  
+   if (target_get_execution_direction () == EXEC_REVERSE)
+     {
+       /* Split off at this point.  */
+       finish_backwards (function);
+       return;
+     }
+ 
+   sal = find_pc_line (get_frame_pc (frame), 0);
+   sal.pc = get_frame_pc (frame);
+ 
+   breakpoint = set_momentary_breakpoint (sal, get_frame_id (frame), bp_finish);
+ 
+   if (!target_can_async_p ())
+     old_chain = make_cleanup_delete_breakpoint (breakpoint);
+   else
+     old_chain = make_exec_cleanup_delete_breakpoint (breakpoint);
+ 
    /* If running asynchronously and the target support asynchronous
       execution, set things up for the rest of the finish command to be
       completed later on, when gdb has detected that the target has
*************** finish_command (char *arg, int from_tty)
*** 1371,1376 ****
--- 1384,1445 ----
        do_cleanups (old_chain);
      }
  }
+ 
+ static void
+ finish_backwards (struct symbol *function)
+ {
+   struct symtab_and_line sal;
+   struct breakpoint *breakpoint;
+   struct cleanup *old_chain;
+   CORE_ADDR func_addr;
+ 
+   if (find_pc_partial_function (get_frame_pc (get_current_frame ()),
+ 				NULL, &func_addr, NULL) == 0)
+     internal_error (__FILE__, __LINE__, 
+ 		    "Finish: couldn't find function.");
+ 
+   sal = find_pc_line (func_addr, 0);
+ 
+   /* Let's cheat and not worry about async until later.  */
+ 
+   /* We don't need a return value.  */
+   proceed_to_finish = 0;
+   /* Special case: if we're sitting at the function entry point, 
+      then all we need to do is take a reverse singlestep.  We
+      don't need to set a breakpoint, and indeed it would do us
+      no good to do so.
+ 
+      Note that this can only happen at frame #0, since there's
+      no way that a function up the stack can have a return address
+      that's equal to its entry point.  */
+ 
+   if (sal.pc != read_pc ())
+     {
+       /* Set breakpoint and continue.  */
+       breakpoint = 
+ 	set_momentary_breakpoint (sal, 
+ 				  get_frame_id (get_selected_frame (NULL)),
+ 				  bp_breakpoint);
+       /* Tell the breakpoint to keep quiet.  We won't be done 
+          until we've done another reverse single-step.  */
+       breakpoint_silence (breakpoint);
+       old_chain = make_cleanup_delete_breakpoint (breakpoint);
+       proceed ((CORE_ADDR) -1, TARGET_SIGNAL_DEFAULT, 0);
+       /* We will be stopped when proceed returns.  */
+       do_cleanups (old_chain);
+     }
+   if (bpstat_find_breakpoint (stop_bpstat, breakpoint) != NULL)
+     {
+       /* If in fact we hit the step-resume breakpoint (and not
+ 	 some other breakpoint), then we're almost there -- 
+ 	 we just need to back up by one more single-step.  */
+       /* (Kludgy way of letting wait_for_inferior know...) */
+       step_range_start = step_range_end = 1;
+       proceed ((CORE_ADDR) -1, TARGET_SIGNAL_DEFAULT, 1);
+     }
+   return;
+ }
+ 
  
  
  static void
Index: infrun.c
===================================================================
RCS file: /cvs/src/src/gdb/infrun.c,v
retrieving revision 1.210
diff -p -r1.210 infrun.c
*** infrun.c	30 Mar 2006 16:37:13 -0000	1.210
--- infrun.c	31 Mar 2006 21:48:07 -0000
*************** enum inferior_stop_reason
*** 905,911 ****
    /* Inferior exited. */
    EXITED,
    /* Inferior received signal, and user asked to be notified. */
!   SIGNAL_RECEIVED
  };
  
  /* This structure contains what used to be local variables in
--- 905,913 ----
    /* Inferior exited. */
    EXITED,
    /* Inferior received signal, and user asked to be notified. */
!   SIGNAL_RECEIVED,
!   /* Reverse execution -- target ran out of history info.  */
!   NO_HISTORY
  };
  
  /* This structure contains what used to be local variables in
*************** handle_inferior_event (struct execution_
*** 1504,1509 ****
--- 1506,1517 ----
        stop_signal = ecs->ws.value.sig;
        break;
  
+     case TARGET_WAITKIND_NO_HISTORY:
+       /* Reverse execution: target ran out of history info.  */
+       print_stop_reason (NO_HISTORY, 0);
+       stop_stepping (ecs);
+       return;
+ 
        /* We had an event in the inferior, but we are not interested
           in handling it at this level. The lower layers have already
           done what needs to be done, if anything.
*************** process_event_stop_test:
*** 2129,2134 ****
--- 2137,2153 ----
  	    keep_going (ecs);
  	    return;
  	  }
+ 	if (stop_pc == ecs->stop_func_start &&
+ 	    target_get_execution_direction () == EXEC_REVERSE)
+ 	  {
+ 	    /* We are stepping over a function call in reverse, and
+ 	       just hit the step-resume breakpoint at the start
+ 	       address of the function.  Go back to single-stepping,
+ 	       which should take us back to the function call.  */
+ 	    ecs->another_trap = 1;
+ 	    keep_going (ecs);
+ 	    return;
+ 	  }
  	break;
  
        case BPSTAT_WHAT_THROUGH_SIGTRAMP:
*************** process_event_stop_test:
*** 2312,2318 ****
  	 fprintf_unfiltered (gdb_stdlog, "infrun: stepping inside range [0x%s-0x%s]\n",
  			    paddr_nz (step_range_start),
  			    paddr_nz (step_range_end));
!       keep_going (ecs);
        return;
      }
  
--- 2331,2352 ----
  	 fprintf_unfiltered (gdb_stdlog, "infrun: stepping inside range [0x%s-0x%s]\n",
  			    paddr_nz (step_range_start),
  			    paddr_nz (step_range_end));
! 
!       /* When stepping backward, stop at beginning of line range
! 	 (unles it's the function entry point, in which case 
! 	 keep going back to the call point).  */
!       if (stop_pc == step_range_start &&
! 	  stop_pc != ecs->stop_func_start &&
! 	  target_get_execution_direction () == EXEC_REVERSE)
! 	{
! 	  stop_step = 1;
! 	  print_stop_reason (END_STEPPING_RANGE, 0);
! 	  stop_stepping (ecs);
! 	}
!       else
! 	{
! 	  keep_going (ecs);
! 	}
        return;
      }
  
*************** process_event_stop_test:
*** 2393,2402 ****
  
        if (step_over_calls == STEP_OVER_ALL)
  	{
! 	  /* We're doing a "next", set a breakpoint at callee's return
! 	     address (the address at which the caller will
! 	     resume).  */
! 	  insert_step_resume_breakpoint_at_frame (get_prev_frame (get_current_frame ()));
  	  keep_going (ecs);
  	  return;
  	}
--- 2427,2459 ----
  
        if (step_over_calls == STEP_OVER_ALL)
  	{
! 	  /* We're doing a "next".
! 
! 	     Normal (forward) execution: set a breakpoint at the
! 	     callee's return address (the address at which the caller
! 	     will resume).
! 
! 	     Reverse (backward) execution.  set the step-resume
! 	     breakpoint at the start of the function that we just
! 	     stepped into (backwards), and continue to there.  When we
! 	     get there, we'll need to single-step back to the
! 	     caller.  */
! 
! 	  if (target_get_execution_direction () == EXEC_REVERSE)
! 	    {
! 	      /* FIXME: I'm not sure if we've handled the frame for
! 		 recursion.  */
! 
! 	      struct symtab_and_line sr_sal;
! 	      init_sal (&sr_sal);
! 	      sr_sal.pc = ecs->stop_func_start;
! 	      insert_step_resume_breakpoint_at_sal (sr_sal, null_frame_id);
! 	    }
! 	  else
! 	    {
! 	      insert_step_resume_breakpoint_at_frame
! 		(get_prev_frame (get_current_frame ()));
! 	    }
  	  keep_going (ecs);
  	  return;
  	}
*************** process_event_stop_test:
*** 2457,2465 ****
  	  return;
  	}
  
!       /* Set a breakpoint at callee's return address (the address at
!          which the caller will resume).  */
!       insert_step_resume_breakpoint_at_frame (get_prev_frame (get_current_frame ()));
        keep_going (ecs);
        return;
      }
--- 2514,2536 ----
  	  return;
  	}
  
!       if (target_get_execution_direction () == EXEC_REVERSE)
! 	{
! 	  /* Set a breakpoint at callee's start address.
! 	     From there we can step once and be back in the caller.  */
! 	  /* FIXME: I'm not sure we've handled the frame for recursion.  */
! 	  struct symtab_and_line sr_sal;
! 	  init_sal (&sr_sal);
! 	  sr_sal.pc = ecs->stop_func_start;
! 	  insert_step_resume_breakpoint_at_sal (sr_sal, null_frame_id);
! 	}
!       else
! 	{
! 	  /* Set a breakpoint at callee's return address (the address
! 	     at which the caller will resume).  */
! 	  insert_step_resume_breakpoint_at_frame
! 	    (get_prev_frame (get_current_frame ()));
! 	}
        keep_going (ecs);
        return;
      }
*************** process_event_stop_test:
*** 2585,2601 ****
  
    if (ecs->stop_func_end && ecs->sal.end >= ecs->stop_func_end)
      {
!       /* If this is the last line of the function, don't keep stepping
!          (it would probably step us out of the function).
!          This is particularly necessary for a one-line function,
!          in which after skipping the prologue we better stop even though
!          we will be in mid-line.  */
!       if (debug_infrun)
! 	 fprintf_unfiltered (gdb_stdlog, "infrun: stepped to a different function\n");
!       stop_step = 1;
!       print_stop_reason (END_STEPPING_RANGE, 0);
!       stop_stepping (ecs);
!       return;
      }
    step_range_start = ecs->sal.pc;
    step_range_end = ecs->sal.end;
--- 2656,2693 ----
  
    if (ecs->stop_func_end && ecs->sal.end >= ecs->stop_func_end)
      {
!       if (target_get_execution_direction () != EXEC_REVERSE)
! 	{
! 	  /* If this is the last line of the function, don't keep
! 	     stepping (it would probably step us out of the function).
! 	     This is particularly necessary for a one-line function,
! 	     in which after skipping the prologue we better stop even
! 	     though we will be in mid-line.  */
! 	  if (debug_infrun)
! 	    fprintf_unfiltered (gdb_stdlog, 
! 				"infrun: stepped to a different function\n");
! 	  stop_step = 1;
! 	  print_stop_reason (END_STEPPING_RANGE, 0);
! 	  stop_stepping (ecs);
! 	  return;
! 	}
!       else
! 	{
! 	  /* If we stepped backward into the last line of a function,
! 	     then we've presumably stepped thru a return.  We want to
! 	     keep stepping backward until we reach the beginning of
! 	     the new line.  */
! 	  step_range_start = ecs->sal.pc;
! 	  step_range_end = ecs->sal.end;
! 	  step_frame_id = get_frame_id (get_current_frame ());
! 	  ecs->current_line = ecs->sal.line;
! 	  ecs->current_symtab = ecs->sal.symtab;
! 	  /* Adjust for prologue, in case of a one-line function.  */
! 	  if (in_prologue (step_range_start, ecs->stop_func_start))
! 	    step_range_start = SKIP_PROLOGUE (step_range_start);
! 	  keep_going (ecs);
! 	  return;
! 	}
      }
    step_range_start = ecs->sal.pc;
    step_range_end = ecs->sal.end;
*************** step_into_function (struct execution_con
*** 2658,2663 ****
--- 2750,2777 ----
    if (s && s->language != language_asm)
      ecs->stop_func_start = SKIP_PROLOGUE (ecs->stop_func_start);
  
+   if (target_get_execution_direction () == EXEC_REVERSE)
+     {
+       ecs->sal = find_pc_line (stop_pc, 0);
+ 
+       /* OK, we're just gonna keep stepping here.  */
+       if (ecs->sal.pc == stop_pc)
+ 	{
+ 	  /* We're there already.  Just stop stepping now.  */
+ 	  stop_step = 1;
+ 	  print_stop_reason (END_STEPPING_RANGE, 0);
+ 	  stop_stepping (ecs);
+ 	  return;
+ 	}
+       /* Else just reset the step range and keep going.
+ 	 No step-resume breakpoint, they don't work for
+ 	 epilogues, which can have multiple entry paths.  */
+       step_range_start = ecs->sal.pc;
+       step_range_end   = ecs->sal.end;
+       keep_going (ecs);
+       return;
+     }
+   /* else... */
    ecs->sal = find_pc_line (ecs->stop_func_start, 0);
    /* Use the step_resume_break to step until the end of the prologue,
       even if that involves jumps (as it seems to on the vax under
*************** print_stop_reason (enum inferior_stop_re
*** 2960,2965 ****
--- 3074,3083 ----
        annotate_signal_string_end ();
        ui_out_text (uiout, ".\n");
        break;
+     case NO_HISTORY:
+       /* Reverse execution: target ran out of history info.  */
+       ui_out_text (uiout, "\nNo more reverse-execution history.\n");
+       break;
      default:
        internal_error (__FILE__, __LINE__,
  		      _("print_stop_reason: unrecognized enum value"));