gdb/dwarf2expr.h

   1 /* DWARF 2 Expression Evaluator.
   2
   3    Copyright (C) 2001, 2002, 2003, 2005, 2007, 2008, 2009, 2010
   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      The value on the dwarf stack is its address.  */
  31   DWARF_VALUE_MEMORY,
  32
  33   /* The piece is in a register.
  34      The value on the dwarf stack is the register number.  */
  35   DWARF_VALUE_REGISTER,
  36
  37   /* The piece is on the dwarf stack.  */
  38   DWARF_VALUE_STACK,
  39
  40   /* The piece is a literal.  */
  41   DWARF_VALUE_LITERAL,
  42
  43   /* The piece was optimized out.  */
  44   DWARF_VALUE_OPTIMIZED_OUT
  45 };
  46
  47 /* The dwarf expression stack.  */
  48
  49 struct dwarf_stack_value
  50 {
  51   CORE_ADDR value;
  52
  53   /* Non-zero if the piece is in memory and is known to be
  54      on the program's stack.  It is always ok to set this to zero.
  55      This is used, for example, to optimize memory access from the target.
  56      It can vastly speed up backtraces on long latency connections when
  57      "set stack-cache on".  */
  58   int in_stack_memory;
  59 };
  60
  61 /* The expression evaluator works with a dwarf_expr_context, describing
  62    its current state and its callbacks.  */
  63 struct dwarf_expr_context
  64 {
  65   /* The stack of values, allocated with xmalloc.  */
  66   struct dwarf_stack_value *stack;
  67
  68   /* The number of values currently pushed on the stack, and the
  69      number of elements allocated to the stack.  */
  70   int stack_len, stack_allocated;
  71
  72   /* Target architecture to use for address operations.  */
  73   struct gdbarch *gdbarch;
  74
  75   /* Target address size in bytes.  */
  76   int addr_size;
  77
  78   /* An opaque argument provided by the caller, which will be passed
  79      to all of the callback functions.  */
  80   void *baton;
  81
  82   /* Return the value of register number REGNUM.  */
  83   CORE_ADDR (*read_reg) (void *baton, int regnum);
  84
  85   /* Read LENGTH bytes at ADDR into BUF.  */
  86   void (*read_mem) (void *baton, gdb_byte *buf, CORE_ADDR addr, size_t length);
  87
  88   /* Return the location expression for the frame base attribute, in
  89      START and LENGTH.  The result must be live until the current
  90      expression evaluation is complete.  */
  91   void (*get_frame_base) (void *baton, gdb_byte **start, size_t *length);
  92
  93   /* Return the CFA for the frame.  */
  94   CORE_ADDR (*get_frame_cfa) (void *baton);
  95
  96   /* Return the thread-local storage address for
  97      DW_OP_GNU_push_tls_address.  */
  98   CORE_ADDR (*get_tls_address) (void *baton, CORE_ADDR offset);
  99
 100 #if 0
 101   /* Not yet implemented.  */
 102
 103   /* Return the location expression for the dwarf expression
 104      subroutine in the die at OFFSET in the current compilation unit.
 105      The result must be live until the current expression evaluation
 106      is complete.  */
 107   unsigned char *(*get_subr) (void *baton, off_t offset, size_t *length);
 108
 109   /* Return the `object address' for DW_OP_push_object_address.  */
 110   CORE_ADDR (*get_object_address) (void *baton);
 111 #endif
 112
 113   /* The current depth of dwarf expression recursion, via DW_OP_call*,
 114      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
 115      depth we'll tolerate before raising an error.  */
 116   int recursion_depth, max_recursion_depth;
 117
 118   /* Location of the value.  */
 119   enum dwarf_value_location location;
 120
 121   /* For VALUE_LITERAL, a the current literal value's length and
 122      data.  */
 123   ULONGEST len;
 124   gdb_byte *data;
 125
 126   /* Initialization status of variable: Non-zero if variable has been
 127      initialized; zero otherwise.  */
 128   int initialized;
 129
 130   /* An array of pieces.  PIECES points to its first element;
 131      NUM_PIECES is its length.
 132
 133      Each time DW_OP_piece is executed, we add a new element to the
 134      end of this array, recording the current top of the stack, the
 135      current location, and the size given as the operand to
 136      DW_OP_piece.  We then pop the top value from the stack, reset the
 137      location, and resume evaluation.
 138
 139      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
 140      from the stack.  We do, ensuring that clients of this interface
 141      expecting to see a value left on the top of the stack (say, code
 142      evaluating frame base expressions or CFA's specified with
 143      DW_CFA_def_cfa_expression) will get an error if the expression
 144      actually marks all the values it computes as pieces.
 145
 146      If an expression never uses DW_OP_piece, num_pieces will be zero.
 147      (It would be nice to present these cases as expressions yielding
 148      a single piece, so that callers need not distinguish between the
 149      no-DW_OP_piece and one-DW_OP_piece cases.  But expressions with
 150      no DW_OP_piece operations have no value to place in a piece's
 151      'size' field; the size comes from the surrounding data.  So the
 152      two cases need to be handled separately.)  */
 153   int num_pieces;
 154   struct dwarf_expr_piece *pieces;
 155 };
 156
 157
 158 /* A piece of an object, as recorded by DW_OP_piece.  */
 159 struct dwarf_expr_piece
 160 {
 161   enum dwarf_value_location location;
 162
 163   union
 164   {
 165     struct
 166     {
 167       /* This piece's address or register number.  */
 168       CORE_ADDR value;
 169       /* Non-zero if the piece is known to be in memory and on
 170          the program's stack.  */
 171       int in_stack_memory;
 172     } expr;
 173
 174     struct
 175     {
 176       /* A pointer to the data making up this piece, for literal
 177          pieces.  */
 178       gdb_byte *data;
 179       /* The length of the available data.  */
 180       ULONGEST length;
 181     } literal;
 182   } v;
 183
 184   /* The length of the piece, in bytes.  */
 185   ULONGEST size;
 186 };
 187
 188 struct dwarf_expr_context *new_dwarf_expr_context (void);
 189 void free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 190 struct cleanup *
 191     make_cleanup_free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 192
 193 void dwarf_expr_push (struct dwarf_expr_context *ctx, CORE_ADDR value,
 194                       int in_stack_memory);
 195 void dwarf_expr_pop (struct dwarf_expr_context *ctx);
 196 void dwarf_expr_eval (struct dwarf_expr_context *ctx, unsigned char *addr,
 197                       size_t len);
 198 CORE_ADDR dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n);
 199 int dwarf_expr_fetch_in_stack_memory (struct dwarf_expr_context *ctx, int n);
 200
 201
 202 gdb_byte *read_uleb128 (gdb_byte *buf, gdb_byte *buf_end, ULONGEST * r);
 203 gdb_byte *read_sleb128 (gdb_byte *buf, gdb_byte *buf_end, LONGEST * r);
 204 CORE_ADDR dwarf2_read_address (struct gdbarch *gdbarch, gdb_byte *buf,
 205                                gdb_byte *buf_end, int addr_size);
 206
 207 #endif /* dwarf2expr.h */