gdb/dwarf2expr.h

   1 /* DWARF 2 Expression Evaluator.
   2
   3    Copyright (C) 2001, 2002, 2003, 2005, 2007 Free Software Foundation, Inc.
   4
   5    Contributed by Daniel Berlin <dan@dberlin.org>.
   6
   7    This file is part of GDB.
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 2 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program; if not, write to the Free Software
  21    Foundation, Inc., 51 Franklin Street, Fifth Floor,
  22    Boston, MA 02110-1301, USA.  */
  23
  24 #if !defined (DWARF2EXPR_H)
  25 #define DWARF2EXPR_H
  26
  27 /* The expression evaluator works with a dwarf_expr_context, describing
  28    its current state and its callbacks.  */
  29 struct dwarf_expr_context
  30 {
  31   /* The stack of values, allocated with xmalloc.  */
  32   CORE_ADDR *stack;
  33
  34   /* The number of values currently pushed on the stack, and the
  35      number of elements allocated to the stack.  */
  36   int stack_len, stack_allocated;
  37
  38   /* An opaque argument provided by the caller, which will be passed
  39      to all of the callback functions.  */
  40   void *baton;
  41
  42   /* Return the value of register number REGNUM.  */
  43   CORE_ADDR (*read_reg) (void *baton, int regnum);
  44
  45   /* Read LENGTH bytes at ADDR into BUF.  */
  46   void (*read_mem) (void *baton, gdb_byte *buf, CORE_ADDR addr, size_t length);
  47
  48   /* Return the location expression for the frame base attribute, in
  49      START and LENGTH.  The result must be live until the current
  50      expression evaluation is complete.  */
  51   void (*get_frame_base) (void *baton, gdb_byte **start, size_t *length);
  52
  53   /* Return the thread-local storage address for
  54      DW_OP_GNU_push_tls_address.  */
  55   CORE_ADDR (*get_tls_address) (void *baton, CORE_ADDR offset);
  56
  57 #if 0
  58   /* Not yet implemented.  */
  59
  60   /* Return the location expression for the dwarf expression
  61      subroutine in the die at OFFSET in the current compilation unit.
  62      The result must be live until the current expression evaluation
  63      is complete.  */
  64   unsigned char *(*get_subr) (void *baton, off_t offset, size_t *length);
  65
  66   /* Return the `object address' for DW_OP_push_object_address.  */
  67   CORE_ADDR (*get_object_address) (void *baton);
  68 #endif
  69
  70   /* The current depth of dwarf expression recursion, via DW_OP_call*,
  71      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
  72      depth we'll tolerate before raising an error.  */
  73   int recursion_depth, max_recursion_depth;
  74
  75   /* Non-zero if the result is in a register.  The register number
  76      will be on the expression stack.  */
  77   int in_reg;
  78
  79   /* Initialization status of variable: Non-zero if variable has been
  80      initialized; zero otherwise.  */
  81   int initialized;
  82
  83   /* An array of pieces.  PIECES points to its first element;
  84      NUM_PIECES is its length.
  85
  86      Each time DW_OP_piece is executed, we add a new element to the
  87      end of this array, recording the current top of the stack, the
  88      current in_reg flag, and the size given as the operand to
  89      DW_OP_piece.  We then pop the top value from the stack, clear the
  90      in_reg flag, and resume evaluation.
  91
  92      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
  93      from the stack.  We do, ensuring that clients of this interface
  94      expecting to see a value left on the top of the stack (say, code
  95      evaluating frame base expressions or CFA's specified with
  96      DW_CFA_def_cfa_expression) will get an error if the expression
  97      actually marks all the values it computes as pieces.
  98
  99      If an expression never uses DW_OP_piece, num_pieces will be zero.
 100      (It would be nice to present these cases as expressions yielding
 101      a single piece, with in_reg clear, so that callers need not
 102      distinguish between the no-DW_OP_piece and one-DW_OP_piece cases.
 103      But expressions with no DW_OP_piece operations have no value to
 104      place in a piece's 'size' field; the size comes from the
 105      surrounding data.  So the two cases need to be handled
 106      separately.)  */
 107   int num_pieces;
 108   struct dwarf_expr_piece *pieces;
 109 };
 110
 111
 112 /* A piece of an object, as recorded by DW_OP_piece.  */
 113 struct dwarf_expr_piece
 114 {
 115   /* If IN_REG is zero, then the piece is in memory, and VALUE is its address.
 116      If IN_REG is non-zero, then the piece is in a register, and VALUE
 117      is the register number.  */
 118   int in_reg;
 119
 120   /* This piece's address or register number.  */
 121   CORE_ADDR value;
 122
 123   /* The length of the piece, in bytes.  */
 124   ULONGEST size;
 125 };
 126
 127 struct dwarf_expr_context *new_dwarf_expr_context (void);
 128 void free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 129
 130 void dwarf_expr_push (struct dwarf_expr_context *ctx, CORE_ADDR value);
 131 void dwarf_expr_pop (struct dwarf_expr_context *ctx);
 132 void dwarf_expr_eval (struct dwarf_expr_context *ctx, unsigned char *addr,
 133                       size_t len);
 134 CORE_ADDR dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n);
 135
 136
 137 gdb_byte *read_uleb128 (gdb_byte *buf, gdb_byte *buf_end, ULONGEST * r);
 138 gdb_byte *read_sleb128 (gdb_byte *buf, gdb_byte *buf_end, LONGEST * r);
 139 CORE_ADDR dwarf2_read_address (gdb_byte *buf, gdb_byte *buf_end,
 140                                int *bytes_read);
 141
 142 #endif /* dwarf2expr.h */