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 location of a value.  */
  27 enum dwarf_value_location
  28 {
  29   /* The piece is in memory.  */
  30   DWARF_VALUE_MEMORY,
  31   /* The piece is in a register.  */
  32   DWARF_VALUE_REGISTER,
  33   /* The piece is on the stack.  */
  34   DWARF_VALUE_STACK,
  35   /* The piece is a literal.  */
  36   DWARF_VALUE_LITERAL
  37 };
  38
  39 /* The expression evaluator works with a dwarf_expr_context, describing
  40    its current state and its callbacks.  */
  41 struct dwarf_expr_context
  42 {
  43   /* The stack of values, allocated with xmalloc.  */
  44   CORE_ADDR *stack;
  45
  46   /* The number of values currently pushed on the stack, and the
  47      number of elements allocated to the stack.  */
  48   int stack_len, stack_allocated;
  49
  50   /* Target architecture to use for address operations.  */
  51   struct gdbarch *gdbarch;
  52
  53   /* Target address size in bytes.  */
  54   int addr_size;
  55
  56   /* An opaque argument provided by the caller, which will be passed
  57      to all of the callback functions.  */
  58   void *baton;
  59
  60   /* Return the value of register number REGNUM.  */
  61   CORE_ADDR (*read_reg) (void *baton, int regnum);
  62
  63   /* Read LENGTH bytes at ADDR into BUF.  */
  64   void (*read_mem) (void *baton, gdb_byte *buf, CORE_ADDR addr, size_t length);
  65
  66   /* Return the location expression for the frame base attribute, in
  67      START and LENGTH.  The result must be live until the current
  68      expression evaluation is complete.  */
  69   void (*get_frame_base) (void *baton, gdb_byte **start, size_t *length);
  70
  71   /* Return the CFA for the frame.  */
  72   CORE_ADDR (*get_frame_cfa) (void *baton);
  73
  74   /* Return the thread-local storage address for
  75      DW_OP_GNU_push_tls_address.  */
  76   CORE_ADDR (*get_tls_address) (void *baton, CORE_ADDR offset);
  77
  78 #if 0
  79   /* Not yet implemented.  */
  80
  81   /* Return the location expression for the dwarf expression
  82      subroutine in the die at OFFSET in the current compilation unit.
  83      The result must be live until the current expression evaluation
  84      is complete.  */
  85   unsigned char *(*get_subr) (void *baton, off_t offset, size_t *length);
  86
  87   /* Return the `object address' for DW_OP_push_object_address.  */
  88   CORE_ADDR (*get_object_address) (void *baton);
  89 #endif
  90
  91   /* The current depth of dwarf expression recursion, via DW_OP_call*,
  92      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
  93      depth we'll tolerate before raising an error.  */
  94   int recursion_depth, max_recursion_depth;
  95
  96   /* Location of the value.  */
  97   enum dwarf_value_location location;
  98
  99   /* For VALUE_LITERAL, a the current literal value's length and
 100      data.  */
 101   ULONGEST len;
 102   gdb_byte *data;
 103
 104   /* Initialization status of variable: Non-zero if variable has been
 105      initialized; zero otherwise.  */
 106   int initialized;
 107
 108   /* An array of pieces.  PIECES points to its first element;
 109      NUM_PIECES is its length.
 110
 111      Each time DW_OP_piece is executed, we add a new element to the
 112      end of this array, recording the current top of the stack, the
 113      current location, and the size given as the operand to
 114      DW_OP_piece.  We then pop the top value from the stack, rest the
 115      location, and resume evaluation.
 116
 117      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
 118      from the stack.  We do, ensuring that clients of this interface
 119      expecting to see a value left on the top of the stack (say, code
 120      evaluating frame base expressions or CFA's specified with
 121      DW_CFA_def_cfa_expression) will get an error if the expression
 122      actually marks all the values it computes as pieces.
 123
 124      If an expression never uses DW_OP_piece, num_pieces will be zero.
 125      (It would be nice to present these cases as expressions yielding
 126      a single piece, so that callers need not distinguish between the
 127      no-DW_OP_piece and one-DW_OP_piece cases.  But expressions with
 128      no DW_OP_piece operations have no value to place in a piece's
 129      'size' field; the size comes from the surrounding data.  So the
 130      two cases need to be handled separately.)  */
 131   int num_pieces;
 132   struct dwarf_expr_piece *pieces;
 133 };
 134
 135
 136 /* A piece of an object, as recorded by DW_OP_piece.  */
 137 struct dwarf_expr_piece
 138 {
 139   enum dwarf_value_location location;
 140
 141   union
 142   {
 143     /* This piece's address or register number.  */
 144     CORE_ADDR value;
 145
 146     struct
 147     {
 148       /* A pointer to the data making up this piece, for literal
 149          pieces.  */
 150       gdb_byte *data;
 151       /* The length of the available data.  */
 152       ULONGEST length;
 153     } literal;
 154   } v;
 155
 156   /* The length of the piece, in bytes.  */
 157   ULONGEST size;
 158 };
 159
 160 struct dwarf_expr_context *new_dwarf_expr_context (void);
 161 void free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 162 struct cleanup *
 163     make_cleanup_free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 164
 165 void dwarf_expr_push (struct dwarf_expr_context *ctx, CORE_ADDR value);
 166 void dwarf_expr_pop (struct dwarf_expr_context *ctx);
 167 void dwarf_expr_eval (struct dwarf_expr_context *ctx, unsigned char *addr,
 168                       size_t len);
 169 CORE_ADDR dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n);
 170
 171
 172 gdb_byte *read_uleb128 (gdb_byte *buf, gdb_byte *buf_end, ULONGEST * r);
 173 gdb_byte *read_sleb128 (gdb_byte *buf, gdb_byte *buf_end, LONGEST * r);
 174 CORE_ADDR dwarf2_read_address (struct gdbarch *gdbarch, gdb_byte *buf,
 175                                gdb_byte *buf_end, int addr_size);
 176
 177 #endif /* dwarf2expr.h */