static CORE_ADDR
execute_stack_op (unsigned char *exp, ULONGEST len,
		  struct frame_info *next_frame, CORE_ADDR initial)
{
  struct dwarf_expr_context *ctx;
  CORE_ADDR result;

  ctx = new_dwarf_expr_context ();
  ctx->baton = next_frame;
  ctx->read_reg = read_reg;
  ctx->read_mem = read_mem;
  ctx->get_frame_base = no_get_frame_base;
  ctx->get_tls_address = no_get_tls_address;

  dwarf_expr_push (ctx, initial);
  dwarf_expr_eval (ctx, exp, len);
  result = dwarf_expr_fetch (ctx, 0);

  if (ctx->in_reg)
    result = read_reg (next_frame, result);

  free_dwarf_expr_context (ctx);

  return result;
}
static int
dwarf2_loc_desc_needs_frame (gdb_byte *data, unsigned short size)
{
  struct needs_frame_baton baton;
  struct dwarf_expr_context *ctx;
  int in_reg;

  baton.needs_frame = 0;

  ctx = new_dwarf_expr_context ();
  ctx->baton = &baton;
  ctx->read_reg = needs_frame_read_reg;
  ctx->read_mem = needs_frame_read_mem;
  ctx->get_frame_base = needs_frame_frame_base;
  ctx->get_tls_address = needs_frame_tls_address;

  dwarf_expr_eval (ctx, data, size);

  in_reg = ctx->in_reg;

  if (ctx->num_pieces > 0)
    {
      int i;

      /* If the location has several pieces, and any of them are in
         registers, then we will need a frame to fetch them from.  */
      for (i = 0; i < ctx->num_pieces; i++)
        if (ctx->pieces[i].in_reg)
          in_reg = 1;
    }

  free_dwarf_expr_context (ctx);

  return baton.needs_frame || in_reg;
}
/* Evaluate a location description, starting at DATA and with length
   SIZE, to find the current location of variable VAR in the context
   of FRAME.  */
static struct value *
dwarf2_evaluate_loc_desc (struct symbol *var, struct frame_info *frame,
			  unsigned char *data, unsigned short size,
			  struct objfile *objfile)
{
  CORE_ADDR result;
  struct value *retval;
  struct dwarf_expr_baton baton;
  struct dwarf_expr_context *ctx;

  if (size == 0)
    {
      retval = allocate_value (SYMBOL_TYPE (var));
      VALUE_LVAL (retval) = not_lval;
      VALUE_OPTIMIZED_OUT (retval) = 1;
    }

  baton.frame = frame;
  baton.objfile = objfile;

  ctx = new_dwarf_expr_context ();
  ctx->baton = &baton;
  ctx->read_reg = dwarf_expr_read_reg;
  ctx->read_mem = dwarf_expr_read_mem;
  ctx->get_frame_base = dwarf_expr_frame_base;
  ctx->get_tls_address = dwarf_expr_tls_address;

  dwarf_expr_eval (ctx, data, size);
  result = dwarf_expr_fetch (ctx, 0);

  if (ctx->in_reg)
    {
      int regnum = DWARF2_REG_TO_REGNUM (result);
      retval = value_from_register (SYMBOL_TYPE (var), regnum, frame);
    }
  else
    {
      retval = allocate_value (SYMBOL_TYPE (var));
      VALUE_BFD_SECTION (retval) = SYMBOL_BFD_SECTION (var);

      VALUE_LVAL (retval) = lval_memory;
      VALUE_LAZY (retval) = 1;
      VALUE_ADDRESS (retval) = result;
    }

  free_dwarf_expr_context (ctx);

  return retval;
}
static int
dwarf2_loc_desc_needs_frame (unsigned char *data, unsigned short size)
{
  struct needs_frame_baton baton;
  struct dwarf_expr_context *ctx;
  int in_reg;

  baton.needs_frame = 0;

  ctx = new_dwarf_expr_context ();
  ctx->baton = &baton;
  ctx->read_reg = needs_frame_read_reg;
  ctx->read_mem = needs_frame_read_mem;
  ctx->get_frame_base = needs_frame_frame_base;
  ctx->get_tls_address = needs_frame_tls_address;

  dwarf_expr_eval (ctx, data, size);

  in_reg = ctx->in_reg;

  free_dwarf_expr_context (ctx);

  return baton.needs_frame || in_reg;
}
/* Evaluate a location description, starting at DATA and with length
   SIZE, to find the current location of variable VAR in the context
   of FRAME.  */
static struct value *
dwarf2_evaluate_loc_desc (struct symbol *var, struct frame_info *frame,
			  gdb_byte *data, unsigned short size,
			  struct objfile *objfile)
{
  struct gdbarch *arch = get_frame_arch (frame);
  struct value *retval;
  struct dwarf_expr_baton baton;
  struct dwarf_expr_context *ctx;

  if (size == 0)
    {
      retval = allocate_value (SYMBOL_TYPE (var));
      VALUE_LVAL (retval) = not_lval;
      set_value_optimized_out (retval, 1);
      return retval;
    }

  baton.frame = frame;
  baton.objfile = objfile;

  ctx = new_dwarf_expr_context ();
  ctx->baton = &baton;
  ctx->read_reg = dwarf_expr_read_reg;
  ctx->read_mem = dwarf_expr_read_mem;
  ctx->get_frame_base = dwarf_expr_frame_base;
  ctx->get_tls_address = dwarf_expr_tls_address;

  dwarf_expr_eval (ctx, data, size);
  if (ctx->num_pieces > 0)
    {
      int i;
      long offset = 0;
      bfd_byte *contents;

      retval = allocate_value (SYMBOL_TYPE (var));
      contents = value_contents_raw (retval);
      for (i = 0; i < ctx->num_pieces; i++)
	{
	  struct dwarf_expr_piece *p = &ctx->pieces[i];
	  if (p->in_reg)
	    {
	      bfd_byte regval[MAX_REGISTER_SIZE];
	      int gdb_regnum = gdbarch_dwarf2_reg_to_regnum
				 (arch, p->value);
	      get_frame_register (frame, gdb_regnum, regval);
	      memcpy (contents + offset, regval, p->size);
	    }
	  else /* In memory?  */
	    {
	      read_memory (p->value, contents + offset, p->size);
	    }
	  offset += p->size;
	}
    }
  else if (ctx->in_reg)
    {
      CORE_ADDR dwarf_regnum = dwarf_expr_fetch (ctx, 0);
      int gdb_regnum = gdbarch_dwarf2_reg_to_regnum
			 (arch, dwarf_regnum);
      retval = value_from_register (SYMBOL_TYPE (var), gdb_regnum, frame);
    }
  else
    {
      CORE_ADDR address = dwarf_expr_fetch (ctx, 0);

      retval = allocate_value (SYMBOL_TYPE (var));
      VALUE_LVAL (retval) = lval_memory;
      set_value_lazy (retval, 1);
      VALUE_ADDRESS (retval) = address;
    }

  set_value_initialized (retval, ctx->initialized);

  free_dwarf_expr_context (ctx);

  return retval;
}
Beispiel #6
0
static void
execute_stack_op (struct dwarf_expr_context *ctx, unsigned char *op_ptr,
		  unsigned char *op_end)
{
  ctx->in_reg = 0;

  while (op_ptr < op_end)
    {
      enum dwarf_location_atom op = *op_ptr++;
      CORE_ADDR result;
      ULONGEST uoffset, reg;
      LONGEST offset;
      int bytes_read;

      switch (op)
	{
	case DW_OP_lit0:
	case DW_OP_lit1:
	case DW_OP_lit2:
	case DW_OP_lit3:
	case DW_OP_lit4:
	case DW_OP_lit5:
	case DW_OP_lit6:
	case DW_OP_lit7:
	case DW_OP_lit8:
	case DW_OP_lit9:
	case DW_OP_lit10:
	case DW_OP_lit11:
	case DW_OP_lit12:
	case DW_OP_lit13:
	case DW_OP_lit14:
	case DW_OP_lit15:
	case DW_OP_lit16:
	case DW_OP_lit17:
	case DW_OP_lit18:
	case DW_OP_lit19:
	case DW_OP_lit20:
	case DW_OP_lit21:
	case DW_OP_lit22:
	case DW_OP_lit23:
	case DW_OP_lit24:
	case DW_OP_lit25:
	case DW_OP_lit26:
	case DW_OP_lit27:
	case DW_OP_lit28:
	case DW_OP_lit29:
	case DW_OP_lit30:
	case DW_OP_lit31:
	  result = op - DW_OP_lit0;
	  break;

	case DW_OP_addr:
	  result = dwarf2_read_address (op_ptr, op_end, &bytes_read);
	  op_ptr += bytes_read;
	  break;

	case DW_OP_const1u:
	  result = extract_unsigned_integer (op_ptr, 1);
	  op_ptr += 1;
	  break;
	case DW_OP_const1s:
	  result = extract_signed_integer (op_ptr, 1);
	  op_ptr += 1;
	  break;
	case DW_OP_const2u:
	  result = extract_unsigned_integer (op_ptr, 2);
	  op_ptr += 2;
	  break;
	case DW_OP_const2s:
	  result = extract_signed_integer (op_ptr, 2);
	  op_ptr += 2;
	  break;
	case DW_OP_const4u:
	  result = extract_unsigned_integer (op_ptr, 4);
	  op_ptr += 4;
	  break;
	case DW_OP_const4s:
	  result = extract_signed_integer (op_ptr, 4);
	  op_ptr += 4;
	  break;
	case DW_OP_const8u:
	  result = extract_unsigned_integer (op_ptr, 8);
	  op_ptr += 8;
	  break;
	case DW_OP_const8s:
	  result = extract_signed_integer (op_ptr, 8);
	  op_ptr += 8;
	  break;
	case DW_OP_constu:
	  op_ptr = read_uleb128 (op_ptr, op_end, &uoffset);
	  result = uoffset;
	  break;
	case DW_OP_consts:
	  op_ptr = read_sleb128 (op_ptr, op_end, &offset);
	  result = offset;
	  break;

	/* The DW_OP_reg operations are required to occur alone in
	   location expressions.  */
	case DW_OP_reg0:
	case DW_OP_reg1:
	case DW_OP_reg2:
	case DW_OP_reg3:
	case DW_OP_reg4:
	case DW_OP_reg5:
	case DW_OP_reg6:
	case DW_OP_reg7:
	case DW_OP_reg8:
	case DW_OP_reg9:
	case DW_OP_reg10:
	case DW_OP_reg11:
	case DW_OP_reg12:
	case DW_OP_reg13:
	case DW_OP_reg14:
	case DW_OP_reg15:
	case DW_OP_reg16:
	case DW_OP_reg17:
	case DW_OP_reg18:
	case DW_OP_reg19:
	case DW_OP_reg20:
	case DW_OP_reg21:
	case DW_OP_reg22:
	case DW_OP_reg23:
	case DW_OP_reg24:
	case DW_OP_reg25:
	case DW_OP_reg26:
	case DW_OP_reg27:
	case DW_OP_reg28:
	case DW_OP_reg29:
	case DW_OP_reg30:
	case DW_OP_reg31:
	  if (op_ptr != op_end && *op_ptr != DW_OP_piece)
	    error ("DWARF-2 expression error: DW_OP_reg operations must be "
		   "used either alone or in conjuction with DW_OP_piece.");

	  result = op - DW_OP_reg0;
	  ctx->in_reg = 1;

	  break;

	case DW_OP_regx:
	  op_ptr = read_uleb128 (op_ptr, op_end, &reg);
	  if (op_ptr != op_end && *op_ptr != DW_OP_piece)
	    error ("DWARF-2 expression error: DW_OP_reg operations must be "
		   "used either alone or in conjuction with DW_OP_piece.");

	  result = reg;
	  ctx->in_reg = 1;
	  break;

	case DW_OP_breg0:
	case DW_OP_breg1:
	case DW_OP_breg2:
	case DW_OP_breg3:
	case DW_OP_breg4:
	case DW_OP_breg5:
	case DW_OP_breg6:
	case DW_OP_breg7:
	case DW_OP_breg8:
	case DW_OP_breg9:
	case DW_OP_breg10:
	case DW_OP_breg11:
	case DW_OP_breg12:
	case DW_OP_breg13:
	case DW_OP_breg14:
	case DW_OP_breg15:
	case DW_OP_breg16:
	case DW_OP_breg17:
	case DW_OP_breg18:
	case DW_OP_breg19:
	case DW_OP_breg20:
	case DW_OP_breg21:
	case DW_OP_breg22:
	case DW_OP_breg23:
	case DW_OP_breg24:
	case DW_OP_breg25:
	case DW_OP_breg26:
	case DW_OP_breg27:
	case DW_OP_breg28:
	case DW_OP_breg29:
	case DW_OP_breg30:
	case DW_OP_breg31:
	  {
	    op_ptr = read_sleb128 (op_ptr, op_end, &offset);
	    result = (ctx->read_reg) (ctx->baton, op - DW_OP_breg0);
	    result += offset;
	  }
	  break;
	case DW_OP_bregx:
	  {
	    op_ptr = read_uleb128 (op_ptr, op_end, &reg);
	    op_ptr = read_sleb128 (op_ptr, op_end, &offset);
	    result = (ctx->read_reg) (ctx->baton, reg);
	    result += offset;
	  }
	  break;
	case DW_OP_fbreg:
	  {
	    unsigned char *datastart;
	    size_t datalen;
	    unsigned int before_stack_len;

	    op_ptr = read_sleb128 (op_ptr, op_end, &offset);
	    /* Rather than create a whole new context, we simply
	       record the stack length before execution, then reset it
	       afterwards, effectively erasing whatever the recursive
	       call put there.  */
	    before_stack_len = ctx->stack_len;
	    /* FIXME: cagney/2003-03-26: This code should be using
               get_frame_base_address(), and then implement a dwarf2
               specific this_base method.  */
	    (ctx->get_frame_base) (ctx->baton, &datastart, &datalen);
	    dwarf_expr_eval (ctx, datastart, datalen);
	    result = dwarf_expr_fetch (ctx, 0);
	    if (ctx->in_reg)
	      result = (ctx->read_reg) (ctx->baton, result);
	    result = result + offset;
	    ctx->stack_len = before_stack_len;
	    ctx->in_reg = 0;
	  }
	  break;
	case DW_OP_dup:
	  result = dwarf_expr_fetch (ctx, 0);
	  break;

	case DW_OP_drop:
	  dwarf_expr_pop (ctx);
	  goto no_push;

	case DW_OP_pick:
	  offset = *op_ptr++;
	  result = dwarf_expr_fetch (ctx, offset);
	  break;

	case DW_OP_over:
	  result = dwarf_expr_fetch (ctx, 1);
	  break;

	case DW_OP_rot:
	  {
	    CORE_ADDR t1, t2, t3;

	    if (ctx->stack_len < 3)
	       error ("Not enough elements for DW_OP_rot. Need 3, have %d\n",
		      ctx->stack_len);
	    t1 = ctx->stack[ctx->stack_len - 1];
	    t2 = ctx->stack[ctx->stack_len - 2];
	    t3 = ctx->stack[ctx->stack_len - 3];
	    ctx->stack[ctx->stack_len - 1] = t2;
	    ctx->stack[ctx->stack_len - 2] = t3;
	    ctx->stack[ctx->stack_len - 3] = t1;
	    goto no_push;
	  }

	case DW_OP_deref:
	case DW_OP_deref_size:
	case DW_OP_abs:
	case DW_OP_neg:
	case DW_OP_not:
	case DW_OP_plus_uconst:
	  /* Unary operations.  */
	  result = dwarf_expr_fetch (ctx, 0);
	  dwarf_expr_pop (ctx);

	  switch (op)
	    {
	    case DW_OP_deref:
	      {
		char *buf = alloca (TARGET_ADDR_BIT / TARGET_CHAR_BIT);
		int bytes_read;

		(ctx->read_mem) (ctx->baton, buf, result,
				 TARGET_ADDR_BIT / TARGET_CHAR_BIT);
		result = dwarf2_read_address (buf,
					      buf + (TARGET_ADDR_BIT
						     / TARGET_CHAR_BIT),
					      &bytes_read);
	      }
	      break;

	    case DW_OP_deref_size:
	      {
		char *buf = alloca (TARGET_ADDR_BIT / TARGET_CHAR_BIT);
		int bytes_read;

		(ctx->read_mem) (ctx->baton, buf, result, *op_ptr++);
		result = dwarf2_read_address (buf,
					      buf + (TARGET_ADDR_BIT
						     / TARGET_CHAR_BIT),
					      &bytes_read);
	      }
	      break;

	    case DW_OP_abs:
	      if ((signed int) result < 0)
		result = -result;
	      break;
	    case DW_OP_neg:
	      result = -result;
	      break;
	    case DW_OP_not:
	      result = ~result;
	      break;
	    case DW_OP_plus_uconst:
	      op_ptr = read_uleb128 (op_ptr, op_end, &reg);
	      result += reg;
	      break;
	    }
	  break;

	case DW_OP_and:
	case DW_OP_div:
	case DW_OP_minus:
	case DW_OP_mod:
	case DW_OP_mul:
	case DW_OP_or:
	case DW_OP_plus:
	case DW_OP_shl:
	case DW_OP_shr:
	case DW_OP_shra:
	case DW_OP_xor:
	case DW_OP_le:
	case DW_OP_ge:
	case DW_OP_eq:
	case DW_OP_lt:
	case DW_OP_gt:
	case DW_OP_ne:
	  {
	    /* Binary operations.  Use the value engine to do computations in
	       the right width.  */
	    CORE_ADDR first, second;
	    enum exp_opcode binop;
	    struct value *val1, *val2;

	    second = dwarf_expr_fetch (ctx, 0);
	    dwarf_expr_pop (ctx);

	    first = dwarf_expr_fetch (ctx, 0);
	    dwarf_expr_pop (ctx);

	    val1 = value_from_longest (unsigned_address_type (), first);
	    val2 = value_from_longest (unsigned_address_type (), second);

	    switch (op)
	      {
	      case DW_OP_and:
		binop = BINOP_BITWISE_AND;
		break;
	      case DW_OP_div:
		binop = BINOP_DIV;
                break;
	      case DW_OP_minus:
		binop = BINOP_SUB;
		break;
	      case DW_OP_mod:
		binop = BINOP_MOD;
		break;
	      case DW_OP_mul:
		binop = BINOP_MUL;
		break;
	      case DW_OP_or:
		binop = BINOP_BITWISE_IOR;
		break;
	      case DW_OP_plus:
		binop = BINOP_ADD;
		break;
	      case DW_OP_shl:
		binop = BINOP_LSH;
		break;
	      case DW_OP_shr:
		binop = BINOP_RSH;
                break;
	      case DW_OP_shra:
		binop = BINOP_RSH;
		val1 = value_from_longest (signed_address_type (), first);
		break;
	      case DW_OP_xor:
		binop = BINOP_BITWISE_XOR;
		break;
	      case DW_OP_le:
		binop = BINOP_LEQ;
		break;
	      case DW_OP_ge:
		binop = BINOP_GEQ;
		break;
	      case DW_OP_eq:
		binop = BINOP_EQUAL;
		break;
	      case DW_OP_lt:
		binop = BINOP_LESS;
		break;
	      case DW_OP_gt:
		binop = BINOP_GTR;
		break;
	      case DW_OP_ne:
		binop = BINOP_NOTEQUAL;
		break;
	      default:
		internal_error (__FILE__, __LINE__,
				"Can't be reached.");
	      }
	    result = value_as_long (value_binop (val1, val2, binop));
	  }
	  break;

	case DW_OP_GNU_push_tls_address:
	  /* Variable is at a constant offset in the thread-local
	  storage block into the objfile for the current thread and
	  the dynamic linker module containing this expression. Here
	  we return returns the offset from that base.  The top of the
	  stack has the offset from the beginning of the thread
	  control block at which the variable is located.  Nothing
	  should follow this operator, so the top of stack would be
	  returned.  */
	  result = dwarf_expr_fetch (ctx, 0);
	  dwarf_expr_pop (ctx);
	  result = (ctx->get_tls_address) (ctx->baton, result);
	  break;

	case DW_OP_skip:
	  offset = extract_signed_integer (op_ptr, 2);
	  op_ptr += 2;
	  op_ptr += offset;
	  goto no_push;

	case DW_OP_bra:
	  offset = extract_signed_integer (op_ptr, 2);
	  op_ptr += 2;
	  if (dwarf_expr_fetch (ctx, 0) != 0)
	    op_ptr += offset;
	  dwarf_expr_pop (ctx);
	  goto no_push;

	case DW_OP_nop:
	  goto no_push;

        case DW_OP_piece:
          {
            ULONGEST size;
            CORE_ADDR addr_or_regnum;

            /* Record the piece.  */
            op_ptr = read_uleb128 (op_ptr, op_end, &size);
            addr_or_regnum = dwarf_expr_fetch (ctx, 0);
            add_piece (ctx, ctx->in_reg, addr_or_regnum, size);

            /* Pop off the address/regnum, and clear the in_reg flag.  */
            dwarf_expr_pop (ctx);
            ctx->in_reg = 0;
          }
          goto no_push;

	default:
	  error ("Unhandled dwarf expression opcode 0x%x", op);
	}

      /* Most things push a result value.  */
      dwarf_expr_push (ctx, result);
    no_push:;
    }
}
static void
execute_stack_op (struct dwarf_expr_context *ctx,
		  gdb_byte *op_ptr, gdb_byte *op_end)
{
  enum bfd_endian byte_order = gdbarch_byte_order (ctx->gdbarch);
  ctx->location = DWARF_VALUE_MEMORY;
  ctx->initialized = 1;  /* Default is initialized.  */

  if (ctx->recursion_depth > ctx->max_recursion_depth)
    error (_("DWARF-2 expression error: Loop detected (%d)."),
	   ctx->recursion_depth);
  ctx->recursion_depth++;

  while (op_ptr < op_end)
    {
      enum dwarf_location_atom op = *op_ptr++;
      CORE_ADDR result;
      /* Assume the value is not in stack memory.
	 Code that knows otherwise sets this to 1.
	 Some arithmetic on stack addresses can probably be assumed to still
	 be a stack address, but we skip this complication for now.
	 This is just an optimization, so it's always ok to punt
	 and leave this as 0.  */
      int in_stack_memory = 0;
      ULONGEST uoffset, reg;
      LONGEST offset;

      switch (op)
	{
	case DW_OP_lit0:
	case DW_OP_lit1:
	case DW_OP_lit2:
	case DW_OP_lit3:
	case DW_OP_lit4:
	case DW_OP_lit5:
	case DW_OP_lit6:
	case DW_OP_lit7:
	case DW_OP_lit8:
	case DW_OP_lit9:
	case DW_OP_lit10:
	case DW_OP_lit11:
	case DW_OP_lit12:
	case DW_OP_lit13:
	case DW_OP_lit14:
	case DW_OP_lit15:
	case DW_OP_lit16:
	case DW_OP_lit17:
	case DW_OP_lit18:
	case DW_OP_lit19:
	case DW_OP_lit20:
	case DW_OP_lit21:
	case DW_OP_lit22:
	case DW_OP_lit23:
	case DW_OP_lit24:
	case DW_OP_lit25:
	case DW_OP_lit26:
	case DW_OP_lit27:
	case DW_OP_lit28:
	case DW_OP_lit29:
	case DW_OP_lit30:
	case DW_OP_lit31:
	  result = op - DW_OP_lit0;
	  break;

	case DW_OP_addr:
	  result = dwarf2_read_address (ctx->gdbarch,
					op_ptr, op_end, ctx->addr_size);
	  op_ptr += ctx->addr_size;
	  break;

	case DW_OP_const1u:
	  result = extract_unsigned_integer (op_ptr, 1, byte_order);
	  op_ptr += 1;
	  break;
	case DW_OP_const1s:
	  result = extract_signed_integer (op_ptr, 1, byte_order);
	  op_ptr += 1;
	  break;
	case DW_OP_const2u:
	  result = extract_unsigned_integer (op_ptr, 2, byte_order);
	  op_ptr += 2;
	  break;
	case DW_OP_const2s:
	  result = extract_signed_integer (op_ptr, 2, byte_order);
	  op_ptr += 2;
	  break;
	case DW_OP_const4u:
	  result = extract_unsigned_integer (op_ptr, 4, byte_order);
	  op_ptr += 4;
	  break;
	case DW_OP_const4s:
	  result = extract_signed_integer (op_ptr, 4, byte_order);
	  op_ptr += 4;
	  break;
	case DW_OP_const8u:
	  result = extract_unsigned_integer (op_ptr, 8, byte_order);
	  op_ptr += 8;
	  break;
	case DW_OP_const8s:
	  result = extract_signed_integer (op_ptr, 8, byte_order);
	  op_ptr += 8;
	  break;
	case DW_OP_constu:
	  op_ptr = read_uleb128 (op_ptr, op_end, &uoffset);
	  result = uoffset;
	  break;
	case DW_OP_consts:
	  op_ptr = read_sleb128 (op_ptr, op_end, &offset);
	  result = offset;
	  break;

	/* The DW_OP_reg operations are required to occur alone in
	   location expressions.  */
	case DW_OP_reg0:
	case DW_OP_reg1:
	case DW_OP_reg2:
	case DW_OP_reg3:
	case DW_OP_reg4:
	case DW_OP_reg5:
	case DW_OP_reg6:
	case DW_OP_reg7:
	case DW_OP_reg8:
	case DW_OP_reg9:
	case DW_OP_reg10:
	case DW_OP_reg11:
	case DW_OP_reg12:
	case DW_OP_reg13:
	case DW_OP_reg14:
	case DW_OP_reg15:
	case DW_OP_reg16:
	case DW_OP_reg17:
	case DW_OP_reg18:
	case DW_OP_reg19:
	case DW_OP_reg20:
	case DW_OP_reg21:
	case DW_OP_reg22:
	case DW_OP_reg23:
	case DW_OP_reg24:
	case DW_OP_reg25:
	case DW_OP_reg26:
	case DW_OP_reg27:
	case DW_OP_reg28:
	case DW_OP_reg29:
	case DW_OP_reg30:
	case DW_OP_reg31:
	  if (op_ptr != op_end 
	      && *op_ptr != DW_OP_piece
	      && *op_ptr != DW_OP_GNU_uninit)
	    error (_("DWARF-2 expression error: DW_OP_reg operations must be "
		   "used either alone or in conjuction with DW_OP_piece."));

	  result = op - DW_OP_reg0;
	  ctx->location = DWARF_VALUE_REGISTER;
	  break;

	case DW_OP_regx:
	  op_ptr = read_uleb128 (op_ptr, op_end, &reg);
	  require_composition (op_ptr, op_end, "DW_OP_regx");

	  result = reg;
	  ctx->location = DWARF_VALUE_REGISTER;
	  break;

	case DW_OP_implicit_value:
	  {
	    ULONGEST len;
	    op_ptr = read_uleb128 (op_ptr, op_end, &len);
	    if (op_ptr + len > op_end)
	      error (_("DW_OP_implicit_value: too few bytes available."));
	    ctx->len = len;
	    ctx->data = op_ptr;
	    ctx->location = DWARF_VALUE_LITERAL;
	    op_ptr += len;
	    require_composition (op_ptr, op_end, "DW_OP_implicit_value");
	  }
	  goto no_push;

	case DW_OP_stack_value:
	  ctx->location = DWARF_VALUE_STACK;
	  require_composition (op_ptr, op_end, "DW_OP_stack_value");
	  goto no_push;

	case DW_OP_breg0:
	case DW_OP_breg1:
	case DW_OP_breg2:
	case DW_OP_breg3:
	case DW_OP_breg4:
	case DW_OP_breg5:
	case DW_OP_breg6:
	case DW_OP_breg7:
	case DW_OP_breg8:
	case DW_OP_breg9:
	case DW_OP_breg10:
	case DW_OP_breg11:
	case DW_OP_breg12:
	case DW_OP_breg13:
	case DW_OP_breg14:
	case DW_OP_breg15:
	case DW_OP_breg16:
	case DW_OP_breg17:
	case DW_OP_breg18:
	case DW_OP_breg19:
	case DW_OP_breg20:
	case DW_OP_breg21:
	case DW_OP_breg22:
	case DW_OP_breg23:
	case DW_OP_breg24:
	case DW_OP_breg25:
	case DW_OP_breg26:
	case DW_OP_breg27:
	case DW_OP_breg28:
	case DW_OP_breg29:
	case DW_OP_breg30:
	case DW_OP_breg31:
	  {
	    op_ptr = read_sleb128 (op_ptr, op_end, &offset);
	    result = (ctx->read_reg) (ctx->baton, op - DW_OP_breg0);
	    result += offset;
	  }
	  break;
	case DW_OP_bregx:
	  {
	    op_ptr = read_uleb128 (op_ptr, op_end, &reg);
	    op_ptr = read_sleb128 (op_ptr, op_end, &offset);
	    result = (ctx->read_reg) (ctx->baton, reg);
	    result += offset;
	  }
	  break;
	case DW_OP_fbreg:
	  {
	    gdb_byte *datastart;
	    size_t datalen;
	    unsigned int before_stack_len;

	    op_ptr = read_sleb128 (op_ptr, op_end, &offset);
	    /* Rather than create a whole new context, we simply
	       record the stack length before execution, then reset it
	       afterwards, effectively erasing whatever the recursive
	       call put there.  */
	    before_stack_len = ctx->stack_len;
	    /* FIXME: cagney/2003-03-26: This code should be using
               get_frame_base_address(), and then implement a dwarf2
               specific this_base method.  */
	    (ctx->get_frame_base) (ctx->baton, &datastart, &datalen);
	    dwarf_expr_eval (ctx, datastart, datalen);
	    if (ctx->location == DWARF_VALUE_LITERAL
		|| ctx->location == DWARF_VALUE_STACK)
	      error (_("Not implemented: computing frame base using explicit value operator"));
	    result = dwarf_expr_fetch (ctx, 0);
	    if (ctx->location == DWARF_VALUE_REGISTER)
	      result = (ctx->read_reg) (ctx->baton, result);
	    result = result + offset;
	    in_stack_memory = 1;
	    ctx->stack_len = before_stack_len;
	    ctx->location = DWARF_VALUE_MEMORY;
	  }
	  break;

	case DW_OP_dup:
	  result = dwarf_expr_fetch (ctx, 0);
	  in_stack_memory = dwarf_expr_fetch_in_stack_memory (ctx, 0);
	  break;

	case DW_OP_drop:
	  dwarf_expr_pop (ctx);
	  goto no_push;

	case DW_OP_pick:
	  offset = *op_ptr++;
	  result = dwarf_expr_fetch (ctx, offset);
	  in_stack_memory = dwarf_expr_fetch_in_stack_memory (ctx, offset);
	  break;
	  
	case DW_OP_swap:
	  {
	    struct dwarf_stack_value t1, t2;

	    if (ctx->stack_len < 2)
	       error (_("Not enough elements for DW_OP_swap. Need 2, have %d."),
		      ctx->stack_len);
	    t1 = ctx->stack[ctx->stack_len - 1];
	    t2 = ctx->stack[ctx->stack_len - 2];
	    ctx->stack[ctx->stack_len - 1] = t2;
	    ctx->stack[ctx->stack_len - 2] = t1;
	    goto no_push;
	  }

	case DW_OP_over:
	  result = dwarf_expr_fetch (ctx, 1);
	  in_stack_memory = dwarf_expr_fetch_in_stack_memory (ctx, 1);
	  break;

	case DW_OP_rot:
	  {
	    struct dwarf_stack_value t1, t2, t3;

	    if (ctx->stack_len < 3)
	       error (_("Not enough elements for DW_OP_rot. Need 3, have %d."),
		      ctx->stack_len);
	    t1 = ctx->stack[ctx->stack_len - 1];
	    t2 = ctx->stack[ctx->stack_len - 2];
	    t3 = ctx->stack[ctx->stack_len - 3];
	    ctx->stack[ctx->stack_len - 1] = t2;
	    ctx->stack[ctx->stack_len - 2] = t3;
	    ctx->stack[ctx->stack_len - 3] = t1;
	    goto no_push;
	  }

	case DW_OP_deref:
	case DW_OP_deref_size:
	case DW_OP_abs:
	case DW_OP_neg:
	case DW_OP_not:
	case DW_OP_plus_uconst:
	  /* Unary operations.  */
	  result = dwarf_expr_fetch (ctx, 0);
	  dwarf_expr_pop (ctx);

	  switch (op)
	    {
	    case DW_OP_deref:
	      {
		gdb_byte *buf = alloca (ctx->addr_size);
		(ctx->read_mem) (ctx->baton, buf, result, ctx->addr_size);
		result = dwarf2_read_address (ctx->gdbarch,
					      buf, buf + ctx->addr_size,
					      ctx->addr_size);
	      }
	      break;

	    case DW_OP_deref_size:
	      {
		int addr_size = *op_ptr++;
		gdb_byte *buf = alloca (addr_size);
		(ctx->read_mem) (ctx->baton, buf, result, addr_size);
		result = dwarf2_read_address (ctx->gdbarch,
					      buf, buf + addr_size,
					      addr_size);
	      }
	      break;

	    case DW_OP_abs:
	      if ((signed int) result < 0)
		result = -result;
	      break;
	    case DW_OP_neg:
	      result = -result;
	      break;
	    case DW_OP_not:
	      result = ~result;
	      break;
	    case DW_OP_plus_uconst:
	      op_ptr = read_uleb128 (op_ptr, op_end, &reg);
	      result += reg;
	      break;
	    }
	  break;

	case DW_OP_and:
	case DW_OP_div:
	case DW_OP_minus:
	case DW_OP_mod:
	case DW_OP_mul:
	case DW_OP_or:
	case DW_OP_plus:
	case DW_OP_shl:
	case DW_OP_shr:
	case DW_OP_shra:
	case DW_OP_xor:
	case DW_OP_le:
	case DW_OP_ge:
	case DW_OP_eq:
	case DW_OP_lt:
	case DW_OP_gt:
	case DW_OP_ne:
	  {
	    /* Binary operations.  Use the value engine to do computations in
	       the right width.  */
	    CORE_ADDR first, second;
	    enum exp_opcode binop;
	    struct value *val1 = NULL, *val2 = NULL;
	    struct type *stype, *utype;

	    second = dwarf_expr_fetch (ctx, 0);
	    dwarf_expr_pop (ctx);

	    first = dwarf_expr_fetch (ctx, 0);
	    dwarf_expr_pop (ctx);

	    utype = unsigned_address_type (ctx->gdbarch, ctx->addr_size);
	    stype = signed_address_type (ctx->gdbarch, ctx->addr_size);

	    switch (op)
	      {
	      case DW_OP_and:
		binop = BINOP_BITWISE_AND;
		break;
	      case DW_OP_div:
		binop = BINOP_DIV;
		val1 = value_from_longest (stype, first);
		val2 = value_from_longest (stype, second);
                break;
	      case DW_OP_minus:
		binop = BINOP_SUB;
		break;
	      case DW_OP_mod:
		binop = BINOP_MOD;
		break;
	      case DW_OP_mul:
		binop = BINOP_MUL;
		break;
	      case DW_OP_or:
		binop = BINOP_BITWISE_IOR;
		break;
	      case DW_OP_plus:
		binop = BINOP_ADD;
		break;
	      case DW_OP_shl:
		binop = BINOP_LSH;
		break;
	      case DW_OP_shr:
		binop = BINOP_RSH;
                break;
	      case DW_OP_shra:
		binop = BINOP_RSH;
		val1 = value_from_longest (stype, first);
		break;
	      case DW_OP_xor:
		binop = BINOP_BITWISE_XOR;
		break;
	      case DW_OP_le:
		binop = BINOP_LEQ;
		val1 = value_from_longest (stype, first);
		val2 = value_from_longest (stype, second);
		break;
	      case DW_OP_ge:
		binop = BINOP_GEQ;
		val1 = value_from_longest (stype, first);
		val2 = value_from_longest (stype, second);
		break;
	      case DW_OP_eq:
		binop = BINOP_EQUAL;
		val1 = value_from_longest (stype, first);
		val2 = value_from_longest (stype, second);
		break;
	      case DW_OP_lt:
		binop = BINOP_LESS;
		val1 = value_from_longest (stype, first);
		val2 = value_from_longest (stype, second);
		break;
	      case DW_OP_gt:
		binop = BINOP_GTR;
		val1 = value_from_longest (stype, first);
		val2 = value_from_longest (stype, second);
		break;
	      case DW_OP_ne:
		binop = BINOP_NOTEQUAL;
		val1 = value_from_longest (stype, first);
		val2 = value_from_longest (stype, second);
		break;
	      default:
		internal_error (__FILE__, __LINE__,
				_("Can't be reached."));
	      }

	    /* We use unsigned operands by default.  */
	    if (val1 == NULL)
	      val1 = value_from_longest (utype, first);
	    if (val2 == NULL)
	      val2 = value_from_longest (utype, second);

	    result = value_as_long (value_binop (val1, val2, binop));
	  }
	  break;

	case DW_OP_call_frame_cfa:
	  result = (ctx->get_frame_cfa) (ctx->baton);
	  in_stack_memory = 1;
	  break;

	case DW_OP_GNU_push_tls_address:
	  /* Variable is at a constant offset in the thread-local
	  storage block into the objfile for the current thread and
	  the dynamic linker module containing this expression. Here
	  we return returns the offset from that base.  The top of the
	  stack has the offset from the beginning of the thread
	  control block at which the variable is located.  Nothing
	  should follow this operator, so the top of stack would be
	  returned.  */
	  result = dwarf_expr_fetch (ctx, 0);
	  dwarf_expr_pop (ctx);
	  result = (ctx->get_tls_address) (ctx->baton, result);
	  break;

	case DW_OP_skip:
	  offset = extract_signed_integer (op_ptr, 2, byte_order);
	  op_ptr += 2;
	  op_ptr += offset;
	  goto no_push;

	case DW_OP_bra:
	  offset = extract_signed_integer (op_ptr, 2, byte_order);
	  op_ptr += 2;
	  if (dwarf_expr_fetch (ctx, 0) != 0)
	    op_ptr += offset;
	  dwarf_expr_pop (ctx);
	  goto no_push;

	case DW_OP_nop:
	  goto no_push;

        case DW_OP_piece:
          {
            ULONGEST size;

            /* Record the piece.  */
            op_ptr = read_uleb128 (op_ptr, op_end, &size);
	    add_piece (ctx, size);

            /* Pop off the address/regnum, and reset the location
	       type.  */
	    if (ctx->location != DWARF_VALUE_LITERAL)
	      dwarf_expr_pop (ctx);
            ctx->location = DWARF_VALUE_MEMORY;
          }
          goto no_push;

	case DW_OP_GNU_uninit:
	  if (op_ptr != op_end)
	    error (_("DWARF-2 expression error: DW_OP_GNU_uninit must always "
		   "be the very last op."));

	  ctx->initialized = 0;
	  goto no_push;

	default:
	  error (_("Unhandled dwarf expression opcode 0x%x"), op);
	}

      /* Most things push a result value.  */
      dwarf_expr_push (ctx, result, in_stack_memory);
    no_push:;
    }

  ctx->recursion_depth--;
  gdb_assert (ctx->recursion_depth >= 0);
}