gdb/dwarf2expr.h

   1 /* Dwarf2 Expression Evaluator
   2    Copyright 2001, 2002, 2003 Free Software Foundation, Inc.
   3    Contributed by Daniel Berlin (dan@dberlin.org)
   4    This file is part of GDB.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software
  18    Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #if !defined (DWARF2EXPR_H)
  22 #define DWARF2EXPR_H
  23
  24 /* The expression evaluator works with a dwarf_expr_context, describing
  25    its current state and its callbacks.  */
  26 struct dwarf_expr_context
  27 {
  28   /* The stack of values, allocated with xmalloc.  */
  29   CORE_ADDR *stack;
  30
  31   /* The number of values currently pushed on the stack, and the
  32      number of elements allocated to the stack.  */
  33   int stack_len, stack_allocated;
  34
  35   /* An opaque argument provided by the caller, which will be passed
  36      to all of the callback functions.  */
  37   void *baton;
  38
  39   /* Return the value of register number REGNUM.  */
  40   CORE_ADDR (*read_reg) (void *baton, int regnum);
  41
  42   /* Read LENGTH bytes at ADDR into BUF.  */
  43   void (*read_mem) (void *baton, char *buf, CORE_ADDR addr,
  44                     size_t length);
  45
  46   /* Return the location expression for the frame base attribute, in
  47      START and LENGTH.  The result must be live until the current
  48      expression evaluation is complete.  */
  49   void (*get_frame_base) (void *baton, unsigned char **start,
  50                          size_t *length);
  51
  52   /* Return the thread-local storage address for
  53      DW_OP_GNU_push_tls_address.  */
  54   CORE_ADDR (*get_tls_address) (void *baton, CORE_ADDR offset);
  55
  56 #if 0
  57   /* Not yet implemented.  */
  58
  59   /* Return the location expression for the dwarf expression
  60      subroutine in the die at OFFSET in the current compilation unit.
  61      The result must be live until the current expression evaluation
  62      is complete.  */
  63   unsigned char *(*get_subr) (void *baton, off_t offset, size_t *length);
  64
  65   /* Return the `object address' for DW_OP_push_object_address.  */
  66   CORE_ADDR (*get_object_address) (void *baton);
  67 #endif
  68
  69   /* The current depth of dwarf expression recursion, via DW_OP_call*,
  70      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
  71      depth we'll tolerate before raising an error.  */
  72   int recursion_depth, max_recursion_depth;
  73
  74   /* Non-zero if the result is in a register.  The register number
  75      will be on the expression stack.  */
  76   int in_reg;
  77
  78   /* An array of pieces.  PIECES points to its first element;
  79      NUM_PIECES is its length.
  80
  81      Each time DW_OP_piece is executed, we add a new element to the
  82      end of this array, recording the current top of the stack, the
  83      current in_reg flag, and the size given as the operand to
  84      DW_OP_piece.  We then pop the top value from the stack, clear the
  85      in_reg flag, and resume evaluation.
  86
  87      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
  88      from the stack.  We do, ensuring that clients of this interface
  89      expecting to see a value left on the top of the stack (say, code
  90      evaluating frame base expressions or CFA's specified with
  91      DW_CFA_def_cfa_expression) will get an error if the expression
  92      actually marks all the values it computes as pieces.
  93
  94      If an expression never uses DW_OP_piece, num_pieces will be zero.
  95      (It would be nice to present these cases as expressions yielding
  96      a single piece, with in_reg clear, so that callers need not
  97      distinguish between the no-DW_OP_piece and one-DW_OP_piece cases.
  98      But expressions with no DW_OP_piece operations have no value to
  99      place in a piece's 'size' field; the size comes from the
 100      surrounding data.  So the two cases need to be handled
 101      separately.)  */
 102   int num_pieces;
 103   struct dwarf_expr_piece *pieces;
 104 };
 105
 106
 107 /* A piece of an object, as recorded by DW_OP_piece.  */
 108 struct dwarf_expr_piece
 109 {
 110   /* If IN_REG is zero, then the piece is in memory, and VALUE is its address.
 111      If IN_REG is non-zero, then the piece is in a register, and VALUE
 112      is the register number.  */
 113   int in_reg;
 114
 115   /* This piece's address or register number.  */
 116   CORE_ADDR value;
 117
 118   /* The length of the piece, in bytes.  */
 119   ULONGEST size;
 120 };
 121
 122 struct dwarf_expr_context *new_dwarf_expr_context (void);
 123 void free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 124
 125 void dwarf_expr_push (struct dwarf_expr_context *ctx, CORE_ADDR value);
 126 void dwarf_expr_pop (struct dwarf_expr_context *ctx);
 127 void dwarf_expr_eval (struct dwarf_expr_context *ctx, unsigned char *addr,
 128                       size_t len);
 129 CORE_ADDR dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n);
 130
 131
 132 unsigned char *read_uleb128 (unsigned char *buf, unsigned char *buf_end,
 133                              ULONGEST * r);
 134 unsigned char *read_sleb128 (unsigned char *buf, unsigned char *buf_end,
 135                              LONGEST * r);
 136 CORE_ADDR dwarf2_read_address (unsigned char *buf, unsigned char *buf_end,
 137                                int *bytes_read);
 138
 139 #endif