gdb/dwarf2expr.h

   1 /* DWARF 2 Expression Evaluator.
   2
   3    Copyright (C) 2001, 2002, 2003, 2005, 2007, 2008, 2009, 2010, 2011
   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   /* The piece is an implicit pointer.  */
  47   DWARF_VALUE_IMPLICIT_POINTER
  48 };
  49
  50 /* The dwarf expression stack.  */
  51
  52 struct dwarf_stack_value
  53 {
  54   struct value *value;
  55
  56   /* Non-zero if the piece is in memory and is known to be
  57      on the program's stack.  It is always ok to set this to zero.
  58      This is used, for example, to optimize memory access from the target.
  59      It can vastly speed up backtraces on long latency connections when
  60      "set stack-cache on".  */
  61   int in_stack_memory;
  62 };
  63
  64 /* The expression evaluator works with a dwarf_expr_context, describing
  65    its current state and its callbacks.  */
  66 struct dwarf_expr_context
  67 {
  68   /* The stack of values, allocated with xmalloc.  */
  69   struct dwarf_stack_value *stack;
  70
  71   /* The number of values currently pushed on the stack, and the
  72      number of elements allocated to the stack.  */
  73   int stack_len, stack_allocated;
  74
  75   /* Target architecture to use for address operations.  */
  76   struct gdbarch *gdbarch;
  77
  78   /* Target address size in bytes.  */
  79   int addr_size;
  80
  81   /* Offset used to relocate DW_OP_addr argument.  */
  82   CORE_ADDR offset;
  83
  84   /* An opaque argument provided by the caller, which will be passed
  85      to all of the callback functions.  */
  86   void *baton;
  87
  88   /* Return the value of register number REGNUM.  */
  89   CORE_ADDR (*read_reg) (void *baton, int regnum);
  90
  91   /* Read LENGTH bytes at ADDR into BUF.  */
  92   void (*read_mem) (void *baton, gdb_byte *buf, CORE_ADDR addr, size_t length);
  93
  94   /* Return the location expression for the frame base attribute, in
  95      START and LENGTH.  The result must be live until the current
  96      expression evaluation is complete.  */
  97   void (*get_frame_base) (void *baton, const gdb_byte **start, size_t *length);
  98
  99   /* Return the CFA for the frame.  */
 100   CORE_ADDR (*get_frame_cfa) (void *baton);
 101
 102   /* Return the PC for the frame.  */
 103   CORE_ADDR (*get_frame_pc) (void *baton);
 104
 105   /* Return the thread-local storage address for
 106      DW_OP_GNU_push_tls_address.  */
 107   CORE_ADDR (*get_tls_address) (void *baton, CORE_ADDR offset);
 108
 109   /* Execute DW_AT_location expression for the DWARF expression subroutine in
 110      the DIE at DIE_OFFSET in the CU from CTX.  Do not touch STACK while it
 111      being passed to and returned from the called DWARF subroutine.  */
 112   void (*dwarf_call) (struct dwarf_expr_context *ctx, size_t die_offset);
 113
 114   /* Return the base type given by the indicated DIE.  This can throw
 115      an exception if the DIE is invalid or does not represent a base
 116      type.  If can also be NULL in the special case where the
 117      callbacks are not performing evaluation, and thus it is
 118      meaningful to substitute a stub type of the correct size.  */
 119   struct type *(*get_base_type) (struct dwarf_expr_context *ctx, size_t die);
 120
 121 #if 0
 122   /* Not yet implemented.  */
 123
 124   /* Return the `object address' for DW_OP_push_object_address.  */
 125   CORE_ADDR (*get_object_address) (void *baton);
 126 #endif
 127
 128   /* The current depth of dwarf expression recursion, via DW_OP_call*,
 129      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
 130      depth we'll tolerate before raising an error.  */
 131   int recursion_depth, max_recursion_depth;
 132
 133   /* Location of the value.  */
 134   enum dwarf_value_location location;
 135
 136   /* For DWARF_VALUE_LITERAL, the current literal value's length and
 137      data.  For DWARF_VALUE_IMPLICIT_POINTER, LEN is the offset of the
 138      target DIE.  */
 139   ULONGEST len;
 140   const gdb_byte *data;
 141
 142   /* Initialization status of variable: Non-zero if variable has been
 143      initialized; zero otherwise.  */
 144   int initialized;
 145
 146   /* An array of pieces.  PIECES points to its first element;
 147      NUM_PIECES is its length.
 148
 149      Each time DW_OP_piece is executed, we add a new element to the
 150      end of this array, recording the current top of the stack, the
 151      current location, and the size given as the operand to
 152      DW_OP_piece.  We then pop the top value from the stack, reset the
 153      location, and resume evaluation.
 154
 155      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
 156      from the stack.  We do, ensuring that clients of this interface
 157      expecting to see a value left on the top of the stack (say, code
 158      evaluating frame base expressions or CFA's specified with
 159      DW_CFA_def_cfa_expression) will get an error if the expression
 160      actually marks all the values it computes as pieces.
 161
 162      If an expression never uses DW_OP_piece, num_pieces will be zero.
 163      (It would be nice to present these cases as expressions yielding
 164      a single piece, so that callers need not distinguish between the
 165      no-DW_OP_piece and one-DW_OP_piece cases.  But expressions with
 166      no DW_OP_piece operations have no value to place in a piece's
 167      'size' field; the size comes from the surrounding data.  So the
 168      two cases need to be handled separately.)  */
 169   int num_pieces;
 170   struct dwarf_expr_piece *pieces;
 171 };
 172
 173
 174 /* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece.  */
 175 struct dwarf_expr_piece
 176 {
 177   enum dwarf_value_location location;
 178
 179   union
 180   {
 181     struct
 182     {
 183       /* This piece's address, for DWARF_VALUE_MEMORY pieces.  */
 184       CORE_ADDR addr;
 185       /* Non-zero if the piece is known to be in memory and on
 186          the program's stack.  */
 187       int in_stack_memory;
 188     } mem;
 189
 190     /* The piece's register number, for DWARF_VALUE_REGISTER pieces.  */
 191     int regno;
 192
 193     /* The piece's literal value, for DWARF_VALUE_STACK pieces.  */
 194     struct value *value;
 195
 196     struct
 197     {
 198       /* A pointer to the data making up this piece,
 199          for DWARF_VALUE_LITERAL pieces.  */
 200       const gdb_byte *data;
 201       /* The length of the available data.  */
 202       ULONGEST length;
 203     } literal;
 204
 205     /* Used for DWARF_VALUE_IMPLICIT_POINTER.  */
 206     struct
 207     {
 208       /* The referent DIE from DW_OP_GNU_implicit_pointer.  */
 209       ULONGEST die;
 210       /* The byte offset into the resulting data.  */
 211       LONGEST offset;
 212     } ptr;
 213   } v;
 214
 215   /* The length of the piece, in bits.  */
 216   ULONGEST size;
 217   /* The piece offset, in bits.  */
 218   ULONGEST offset;
 219 };
 220
 221 struct dwarf_expr_context *new_dwarf_expr_context (void);
 222 void free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 223 struct cleanup *
 224     make_cleanup_free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 225
 226 void dwarf_expr_push_address (struct dwarf_expr_context *ctx,
 227                               CORE_ADDR value,
 228                               int in_stack_memory);
 229 void dwarf_expr_eval (struct dwarf_expr_context *ctx, const gdb_byte *addr,
 230                       size_t len);
 231 struct value *dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n);
 232 CORE_ADDR dwarf_expr_fetch_address (struct dwarf_expr_context *ctx, int n);
 233 int dwarf_expr_fetch_in_stack_memory (struct dwarf_expr_context *ctx, int n);
 234
 235
 236 const gdb_byte *read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 237                               ULONGEST * r);
 238 const gdb_byte *read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 239                               LONGEST * r);
 240
 241 const char *dwarf_stack_op_name (unsigned int);
 242
 243 void dwarf_expr_require_composition (const gdb_byte *, const gdb_byte *,
 244                                      const char *);
 245
 246 #endif /* dwarf2expr.h */