Re: [PATCH] Let dwarf2 CFI's execute_stack_op be used outside of CFI

[Jim Blandy <jimb at redhat dot com>]

The patch looks fine to me.

In the long run, I think it would be nice if the location expression
interpreter took pointers to functions for reading registers and
memory.  Then it could be used with frames, contexts, or whatever.
But as you say --- small incremental changes are fine.

(Regarding authorship: when Jiri's original patch was accepted, Daniel
did jump in and mention that the code was originally his.  I think
it's fine to accept the authorship comment tentatively, until whatever
questions people have have been addressed.)


Daniel Berlin <dan@dberlin.org> writes:

> This patch simply adds an external entry point (dwarf2_execute_stack_op), 
> that doesn't require the CFA context. It also adds code so that when the 
> context passed to execute_stack_op is NULL, we use read_register_gen to 
> get registers.
> 
> Along the way, I made an obvious fix to DW_OP_deref_size that i'll commit 
> separately, but included in the changelog/patch because i didn't want to 
> hand edit it out.
> 
> 
> I also added my name to the top of the file, since in reality, it's based 
> on code I sent Jiri.
> 
> --Dan
> 2002-03-25  Daniel Berlin  <dan@dberlin.org>
> 
> 	* dwarf2cfi.c (dwarf2_execute_stack_op): New function, external
> 	entry point to execute_stack_op that doesn't require context.
> 	(execute_stack_op): If context is NULL, don't use get_reg, use
> 	read_register_gen.
>         Also fix bug in DW_OP_deref_size.
> 
> 	* dwarf2cfi.h (dwarf2_execute_stack_op): New prototype.
> Index: dwarf2cfi.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/dwarf2cfi.c,v
> retrieving revision 1.1
> diff -c -3 -p -w -B -b -r1.1 dwarf2cfi.c
> *** dwarf2cfi.c	2001/12/07 12:10:15	1.1
> --- dwarf2cfi.c	2002/03/25 23:50:16
> ***************
> *** 1,7 ****
>   /* Stack unwinding code based on dwarf2 frame info for GDB, the GNU debugger.
> !    Copyright 2001
>      Free Software Foundation, Inc.
>      Contributed by Jiri Smid, SuSE Labs.
>   
>      This file is part of GDB.
>   
> --- 1,8 ----
>   /* Stack unwinding code based on dwarf2 frame info for GDB, the GNU debugger.
> !    Copyright 2001, 2002
>      Free Software Foundation, Inc.
>      Contributed by Jiri Smid, SuSE Labs.
> +    Based on code written by Daniel Berlin (dan@dberlin.org)
>   
>      This file is part of GDB.
>   
> *************** get_reg (char *reg, struct context *cont
> *** 840,845 ****
> --- 841,854 ----
>       }
>   }
>   
> + /* External entry point for executing dwarf2 stack operations. */
> + CORE_ADDR
> + dwarf2_execute_stack_op (struct objfile *objfile, char *op_ptr,
> + 			 char *op_end, CORE_ADDR initial)
> + {
> +   return execute_stack_op (objfile, op_ptr, op_end, NULL, initial);
> + }
> + 
>   /* Decode a DW_OP stack program.  Return the top of stack.  Push INITIAL
>      onto the stack to start.  */
>   static CORE_ADDR
> *************** execute_stack_op (struct objfile *objfil
> *** 963,973 ****
> --- 972,989 ----
>   	case DW_OP_reg29:
>   	case DW_OP_reg30:
>   	case DW_OP_reg31:
> + 	  if (context)
>   	    get_reg ((char *) &result, context, op - DW_OP_reg0);
> + 	  else
> + 	    read_register_gen (op - DW_OP_reg0, (char *)&result);
> + 	  
>   	  break;
>   	case DW_OP_regx:
>   	  reg = read_uleb128 (objfile->obfd, &op_ptr);
> + 	  if (context)
>   	    get_reg ((char *) &result, context, reg);
> + 	  else
> + 	    read_register_gen (reg, (char *)&result);
>   	  break;
>   
>   	case DW_OP_breg0:
> *************** execute_stack_op (struct objfile *objfil
> *** 1003,1015 ****
> --- 1019,1038 ----
>   	case DW_OP_breg30:
>   	case DW_OP_breg31:
>   	  offset = read_sleb128 (objfile->obfd, &op_ptr);
> + 	  if (context)
>   	    get_reg ((char *) &result, context, op - DW_OP_breg0);
> + 	  else
> + 	    read_register_gen (op - DW_OP_breg0, (char *)&result);
> + 	  
>   	  result += offset;
>   	  break;
>   	case DW_OP_bregx:
>   	  reg = read_uleb128 (objfile->obfd, &op_ptr);
>   	  offset = read_sleb128 (objfile->obfd, &op_ptr);
> + 	  if (context)
>   	    get_reg ((char *) &result, context, reg);
> + 	  else
> + 	    read_register_gen (reg, (char *)&result);
>   	  result += offset;
>   	  break;
>   
> *************** execute_stack_op (struct objfile *objfil
> *** 1067,1080 ****
>   	    {
>   	    case DW_OP_deref:
>   	      {
> ! 		char *ptr = (char *) result;
>   		result = read_pointer (objfile->obfd, &ptr);
>   	      }
>   	      break;
>   
>   	    case DW_OP_deref_size:
>   	      {
> ! 		char *ptr = (char *) result;
>   		switch (*op_ptr++)
>   		  {
>   		  case 1:
> --- 1090,1103 ----
>   	    {
>   	    case DW_OP_deref:
>   	      {
> ! 		char *ptr = (char *) &result;
>   		result = read_pointer (objfile->obfd, &ptr);
>   	      }
>   	      break;
>   
>   	    case DW_OP_deref_size:
>   	      {
> ! 		char *ptr = (char *) &result;
>   		switch (*op_ptr++)
>   		  {
>   		  case 1:
> Index: dwarf2cfi.h
> ===================================================================
> RCS file: /cvs/src/src/gdb/dwarf2cfi.h,v
> retrieving revision 1.1
> diff -c -3 -p -w -B -b -r1.1 dwarf2cfi.h
> *** dwarf2cfi.h	2001/12/07 12:10:15	1.1
> --- dwarf2cfi.h	2002/03/25 23:50:16
> *************** void cfi_get_saved_register (char *raw_b
> *** 63,66 ****
> --- 63,72 ----
>   void cfi_virtual_frame_pointer (CORE_ADDR pc, int *frame_regnum,
>   				LONGEST * frame_offset);
>   
> + /*  Execute a set of DWARF2 stack operations, starting with INITIAL
> +     as the address on the stack. */
> + CORE_ADDR dwarf2_execute_stack_op (struct objfile *objfile, 
> + 				   char *op_ptr, char *op_end,
> + 				   CORE_ADDR initial);
> + 
>   #endif
> Index: ChangeLog
> ===================================================================
> RCS file: /cvs/src/src/gdb/ChangeLog,v
> retrieving revision 1.2349
> diff -c -3 -p -w -B -b -r1.2349 ChangeLog
> *** ChangeLog	2002/03/25 19:47:39	1.2349
> --- ChangeLog	2002/03/25 23:50:17
> ***************
> *** 1,3 ****
> --- 1,12 ----
> + 2002-03-25  Daniel Berlin  <dan@dberlin.org>
> + 
> + 	* dwarf2cfi.c (dwarf2_execute_stack_op): New function, external
> + 	entry point to execute_stack_op that doesn't require context.
> + 	(execute_stack_op): If context is NULL, don't use get_reg, use
> + 	read_register_gen.
> + 
> + 	* dwarf2cfi.h (dwarf2_execute_stack_op): New prototype.
> + 
>   2002-03-25  Jeff Law (law@redhat.com)
>   
>   	* linux-proc.c (read_mapping): Scan up to end of line for filename.