gdb/dwarf2expr.h

   1 /* DWARF 2 Expression Evaluator.
   2
   3    Copyright (C) 2001, 2002, 2003, 2005, 2007, 2008, 2009
   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 architecture to use for address operations.  */
  38   struct gdbarch *gdbarch;
  39
  40   /* Target address size in bytes.  */
  41   int addr_size;
  42
  43   /* An opaque argument provided by the caller, which will be passed
  44      to all of the callback functions.  */
  45   void *baton;
  46
  47   /* Return the value of register number REGNUM.  */
  48   CORE_ADDR (*read_reg) (void *baton, int regnum);
  49
  50   /* Read LENGTH bytes at ADDR into BUF.  */
  51   void (*read_mem) (void *baton, gdb_byte *buf, CORE_ADDR addr, size_t length);
  52
  53   /* Return the location expression for the frame base attribute, in
  54      START and LENGTH.  The result must be live until the current
  55      expression evaluation is complete.  */
  56   void (*get_frame_base) (void *baton, gdb_byte **start, size_t *length);
  57
  58   /* Return the thread-local storage address for
  59      DW_OP_GNU_push_tls_address.  */
  60   CORE_ADDR (*get_tls_address) (void *baton, CORE_ADDR offset);
  61
  62 #if 0
  63   /* Not yet implemented.  */
  64
  65   /* Return the location expression for the dwarf expression
  66      subroutine in the die at OFFSET in the current compilation unit.
  67      The result must be live until the current expression evaluation
  68      is complete.  */
  69   unsigned char *(*get_subr) (void *baton, off_t offset, size_t *length);
  70
  71   /* Return the `object address' for DW_OP_push_object_address.  */
  72   CORE_ADDR (*get_object_address) (void *baton);
  73 #endif
  74
  75   /* The current depth of dwarf expression recursion, via DW_OP_call*,
  76      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
  77      depth we'll tolerate before raising an error.  */
  78   int recursion_depth, max_recursion_depth;
  79
  80   /* Non-zero if the result is in a register.  The register number
  81      will be on the expression stack.  */
  82   int in_reg;
  83
  84   /* Initialization status of variable: Non-zero if variable has been
  85      initialized; zero otherwise.  */
  86   int initialized;
  87
  88   /* An array of pieces.  PIECES points to its first element;
  89      NUM_PIECES is its length.
  90
  91      Each time DW_OP_piece is executed, we add a new element to the
  92      end of this array, recording the current top of the stack, the
  93      current in_reg flag, and the size given as the operand to
  94      DW_OP_piece.  We then pop the top value from the stack, clear the
  95      in_reg flag, and resume evaluation.
  96
  97      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
  98      from the stack.  We do, ensuring that clients of this interface
  99      expecting to see a value left on the top of the stack (say, code
 100      evaluating frame base expressions or CFA's specified with
 101      DW_CFA_def_cfa_expression) will get an error if the expression
 102      actually marks all the values it computes as pieces.
 103
 104      If an expression never uses DW_OP_piece, num_pieces will be zero.
 105      (It would be nice to present these cases as expressions yielding
 106      a single piece, with in_reg clear, so that callers need not
 107      distinguish between the no-DW_OP_piece and one-DW_OP_piece cases.
 108      But expressions with no DW_OP_piece operations have no value to
 109      place in a piece's 'size' field; the size comes from the
 110      surrounding data.  So the two cases need to be handled
 111      separately.)  */
 112   int num_pieces;
 113   struct dwarf_expr_piece *pieces;
 114 };
 115
 116
 117 /* A piece of an object, as recorded by DW_OP_piece.  */
 118 struct dwarf_expr_piece
 119 {
 120   /* If IN_REG is zero, then the piece is in memory, and VALUE is its address.
 121      If IN_REG is non-zero, then the piece is in a register, and VALUE
 122      is the register number.  */
 123   int in_reg;
 124
 125   /* This piece's address or register number.  */
 126   CORE_ADDR value;
 127
 128   /* The length of the piece, in bytes.  */
 129   ULONGEST size;
 130 };
 131
 132 struct dwarf_expr_context *new_dwarf_expr_context (void);
 133 void free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 134
 135 void dwarf_expr_push (struct dwarf_expr_context *ctx, CORE_ADDR value);
 136 void dwarf_expr_pop (struct dwarf_expr_context *ctx);
 137 void dwarf_expr_eval (struct dwarf_expr_context *ctx, unsigned char *addr,
 138                       size_t len);
 139 CORE_ADDR dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n);
 140
 141
 142 gdb_byte *read_uleb128 (gdb_byte *buf, gdb_byte *buf_end, ULONGEST * r);
 143 gdb_byte *read_sleb128 (gdb_byte *buf, gdb_byte *buf_end, LONGEST * r);
 144 CORE_ADDR dwarf2_read_address (struct gdbarch *gdbarch, gdb_byte *buf,
 145                                gdb_byte *buf_end, int addr_size);
 146
 147 #endif /* dwarf2expr.h */