gdb/dwarf2expr.h

   1 /* DWARF 2 Expression Evaluator.
   2
   3    Copyright (C) 2001, 2002, 2003, 2005, 2007, 2008
   4    Free Software Foundation, Inc.
   5
   6    Contributed by Daniel Berlin <dan@dberlin.org>.
   7
   8    This file is part of GDB.
   9
  10    This program is free software; you can redistribute it and/or modify
  11    it under the terms of the GNU General Public License as published by
  12    the Free Software Foundation; either version 3 of the License, or
  13    (at your option) any later version.
  14
  15    This program is distributed in the hope that it will be useful,
  16    but WITHOUT ANY WARRANTY; without even the implied warranty of
  17    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18    GNU General Public License for more details.
  19
  20    You should have received a copy of the GNU General Public License
  21    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  22
  23 #if !defined (DWARF2EXPR_H)
  24 #define DWARF2EXPR_H
  25
  26 /* The expression evaluator works with a dwarf_expr_context, describing
  27    its current state and its callbacks.  */
  28 struct dwarf_expr_context
  29 {
  30   /* The stack of values, allocated with xmalloc.  */
  31   CORE_ADDR *stack;
  32
  33   /* The number of values currently pushed on the stack, and the
  34      number of elements allocated to the stack.  */
  35   int stack_len, stack_allocated;
  36
  37   /* Target address size in bytes.  */
  38   int addr_size;
  39
  40   /* An opaque argument provided by the caller, which will be passed
  41      to all of the callback functions.  */
  42   void *baton;
  43
  44   /* Return the value of register number REGNUM.  */
  45   CORE_ADDR (*read_reg) (void *baton, int regnum);
  46
  47   /* Read LENGTH bytes at ADDR into BUF.  */
  48   void (*read_mem) (void *baton, gdb_byte *buf, CORE_ADDR addr, size_t length);
  49
  50   /* Return the location expression for the frame base attribute, in
  51      START and LENGTH.  The result must be live until the current
  52      expression evaluation is complete.  */
  53   void (*get_frame_base) (void *baton, gdb_byte **start, size_t *length);
  54
  55   /* Return the thread-local storage address for
  56      DW_OP_GNU_push_tls_address.  */
  57   CORE_ADDR (*get_tls_address) (void *baton, CORE_ADDR offset);
  58
  59 #if 0
  60   /* Not yet implemented.  */
  61
  62   /* Return the location expression for the dwarf expression
  63      subroutine in the die at OFFSET in the current compilation unit.
  64      The result must be live until the current expression evaluation
  65      is complete.  */
  66   unsigned char *(*get_subr) (void *baton, off_t offset, size_t *length);
  67
  68   /* Return the `object address' for DW_OP_push_object_address.  */
  69   CORE_ADDR (*get_object_address) (void *baton);
  70 #endif
  71
  72   /* The current depth of dwarf expression recursion, via DW_OP_call*,
  73      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
  74      depth we'll tolerate before raising an error.  */
  75   int recursion_depth, max_recursion_depth;
  76
  77   /* Non-zero if the result is in a register.  The register number
  78      will be on the expression stack.  */
  79   int in_reg;
  80
  81   /* Initialization status of variable: Non-zero if variable has been
  82      initialized; zero otherwise.  */
  83   int initialized;
  84
  85   /* An array of pieces.  PIECES points to its first element;
  86      NUM_PIECES is its length.
  87
  88      Each time DW_OP_piece is executed, we add a new element to the
  89      end of this array, recording the current top of the stack, the
  90      current in_reg flag, and the size given as the operand to
  91      DW_OP_piece.  We then pop the top value from the stack, clear the
  92      in_reg flag, and resume evaluation.
  93
  94      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
  95      from the stack.  We do, ensuring that clients of this interface
  96      expecting to see a value left on the top of the stack (say, code
  97      evaluating frame base expressions or CFA's specified with
  98      DW_CFA_def_cfa_expression) will get an error if the expression
  99      actually marks all the values it computes as pieces.
 100
 101      If an expression never uses DW_OP_piece, num_pieces will be zero.
 102      (It would be nice to present these cases as expressions yielding
 103      a single piece, with in_reg clear, so that callers need not
 104      distinguish between the no-DW_OP_piece and one-DW_OP_piece cases.
 105      But expressions with no DW_OP_piece operations have no value to
 106      place in a piece's 'size' field; the size comes from the
 107      surrounding data.  So the two cases need to be handled
 108      separately.)  */
 109   int num_pieces;
 110   struct dwarf_expr_piece *pieces;
 111 };
 112
 113
 114 /* A piece of an object, as recorded by DW_OP_piece.  */
 115 struct dwarf_expr_piece
 116 {
 117   /* If IN_REG is zero, then the piece is in memory, and VALUE is its address.
 118      If IN_REG is non-zero, then the piece is in a register, and VALUE
 119      is the register number.  */
 120   int in_reg;
 121
 122   /* This piece's address or register number.  */
 123   CORE_ADDR value;
 124
 125   /* The length of the piece, in bytes.  */
 126   ULONGEST size;
 127 };
 128
 129 struct dwarf_expr_context *new_dwarf_expr_context (void);
 130 void free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 131
 132 void dwarf_expr_push (struct dwarf_expr_context *ctx, CORE_ADDR value);
 133 void dwarf_expr_pop (struct dwarf_expr_context *ctx);
 134 void dwarf_expr_eval (struct dwarf_expr_context *ctx, unsigned char *addr,
 135                       size_t len);
 136 CORE_ADDR dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n);
 137
 138
 139 gdb_byte *read_uleb128 (gdb_byte *buf, gdb_byte *buf_end, ULONGEST * r);
 140 gdb_byte *read_sleb128 (gdb_byte *buf, gdb_byte *buf_end, LONGEST * r);
 141 CORE_ADDR dwarf2_read_address (gdb_byte *buf, gdb_byte *buf_end,
 142                                int addr_size);
 143
 144 #endif /* dwarf2expr.h */