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 3 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, see <http://www.gnu.org/licenses/>.  */
  21
  22 #if !defined (DWARF2EXPR_H)
  23 #define DWARF2EXPR_H
  24
  25 /* The expression evaluator works with a dwarf_expr_context, describing
  26    its current state and its callbacks.  */
  27 struct dwarf_expr_context
  28 {
  29   /* The stack of values, allocated with xmalloc.  */
  30   CORE_ADDR *stack;
  31
  32   /* The number of values currently pushed on the stack, and the
  33      number of elements allocated to the stack.  */
  34   int stack_len, stack_allocated;
  35
  36   /* An opaque argument provided by the caller, which will be passed
  37      to all of the callback functions.  */
  38   void *baton;
  39
  40   /* Return the value of register number REGNUM.  */
  41   CORE_ADDR (*read_reg) (void *baton, int regnum);
  42
  43   /* Read LENGTH bytes at ADDR into BUF.  */
  44   void (*read_mem) (void *baton, gdb_byte *buf, CORE_ADDR addr, 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, gdb_byte **start, size_t *length);
  50
  51   /* Return the thread-local storage address for
  52      DW_OP_GNU_push_tls_address.  */
  53   CORE_ADDR (*get_tls_address) (void *baton, CORE_ADDR offset);
  54
  55 #if 0
  56   /* Not yet implemented.  */
  57
  58   /* Return the location expression for the dwarf expression
  59      subroutine in the die at OFFSET in the current compilation unit.
  60      The result must be live until the current expression evaluation
  61      is complete.  */
  62   unsigned char *(*get_subr) (void *baton, off_t offset, size_t *length);
  63
  64   /* Return the `object address' for DW_OP_push_object_address.  */
  65   CORE_ADDR (*get_object_address) (void *baton);
  66 #endif
  67
  68   /* The current depth of dwarf expression recursion, via DW_OP_call*,
  69      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
  70      depth we'll tolerate before raising an error.  */
  71   int recursion_depth, max_recursion_depth;
  72
  73   /* Non-zero if the result is in a register.  The register number
  74      will be on the expression stack.  */
  75   int in_reg;
  76
  77   /* Initialization status of variable: Non-zero if variable has been
  78      initialized; zero otherwise.  */
  79   int initialized;
  80
  81   /* An array of pieces.  PIECES points to its first element;
  82      NUM_PIECES is its length.
  83
  84      Each time DW_OP_piece is executed, we add a new element to the
  85      end of this array, recording the current top of the stack, the
  86      current in_reg flag, and the size given as the operand to
  87      DW_OP_piece.  We then pop the top value from the stack, clear the
  88      in_reg flag, and resume evaluation.
  89
  90      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
  91      from the stack.  We do, ensuring that clients of this interface
  92      expecting to see a value left on the top of the stack (say, code
  93      evaluating frame base expressions or CFA's specified with
  94      DW_CFA_def_cfa_expression) will get an error if the expression
  95      actually marks all the values it computes as pieces.
  96
  97      If an expression never uses DW_OP_piece, num_pieces will be zero.
  98      (It would be nice to present these cases as expressions yielding
  99      a single piece, with in_reg clear, so that callers need not
 100      distinguish between the no-DW_OP_piece and one-DW_OP_piece cases.
 101      But expressions with no DW_OP_piece operations have no value to
 102      place in a piece's 'size' field; the size comes from the
 103      surrounding data.  So the two cases need to be handled
 104      separately.)  */
 105   int num_pieces;
 106   struct dwarf_expr_piece *pieces;
 107 };
 108
 109
 110 /* A piece of an object, as recorded by DW_OP_piece.  */
 111 struct dwarf_expr_piece
 112 {
 113   /* If IN_REG is zero, then the piece is in memory, and VALUE is its address.
 114      If IN_REG is non-zero, then the piece is in a register, and VALUE
 115      is the register number.  */
 116   int in_reg;
 117
 118   /* This piece's address or register number.  */
 119   CORE_ADDR value;
 120
 121   /* The length of the piece, in bytes.  */
 122   ULONGEST size;
 123 };
 124
 125 struct dwarf_expr_context *new_dwarf_expr_context (void);
 126 void free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 127
 128 void dwarf_expr_push (struct dwarf_expr_context *ctx, CORE_ADDR value);
 129 void dwarf_expr_pop (struct dwarf_expr_context *ctx);
 130 void dwarf_expr_eval (struct dwarf_expr_context *ctx, unsigned char *addr,
 131                       size_t len);
 132 CORE_ADDR dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n);
 133
 134
 135 gdb_byte *read_uleb128 (gdb_byte *buf, gdb_byte *buf_end, ULONGEST * r);
 136 gdb_byte *read_sleb128 (gdb_byte *buf, gdb_byte *buf_end, LONGEST * r);
 137 CORE_ADDR dwarf2_read_address (gdb_byte *buf, gdb_byte *buf_end,
 138                                int *bytes_read);
 139
 140 #endif /* dwarf2expr.h */