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   /* The evaluator is value-based, and frees values up to this point
  85      when the expression context is destroyed.  */
  86   struct value *mark;
  87
  88   /* An opaque argument provided by the caller, which will be passed
  89      to all of the callback functions.  */
  90   void *baton;
  91
  92   /* Return the value of register number REGNUM.  */
  93   CORE_ADDR (*read_reg) (void *baton, int regnum);
  94
  95   /* Read LENGTH bytes at ADDR into BUF.  */
  96   void (*read_mem) (void *baton, gdb_byte *buf, CORE_ADDR addr, size_t length);
  97
  98   /* Return the location expression for the frame base attribute, in
  99      START and LENGTH.  The result must be live until the current
 100      expression evaluation is complete.  */
 101   void (*get_frame_base) (void *baton, const gdb_byte **start, size_t *length);
 102
 103   /* Return the CFA for the frame.  */
 104   CORE_ADDR (*get_frame_cfa) (void *baton);
 105
 106   /* Return the PC for the frame.  */
 107   CORE_ADDR (*get_frame_pc) (void *baton);
 108
 109   /* Return the thread-local storage address for
 110      DW_OP_GNU_push_tls_address.  */
 111   CORE_ADDR (*get_tls_address) (void *baton, CORE_ADDR offset);
 112
 113   /* Execute DW_AT_location expression for the DWARF expression subroutine in
 114      the DIE at DIE_OFFSET in the CU from CTX.  Do not touch STACK while it
 115      being passed to and returned from the called DWARF subroutine.  */
 116   void (*dwarf_call) (struct dwarf_expr_context *ctx, size_t die_offset);
 117
 118   /* Return the base type given by the indicated DIE.  This can throw
 119      an exception if the DIE is invalid or does not represent a base
 120      type.  If can also be NULL in the special case where the
 121      callbacks are not performing evaluation, and thus it is
 122      meaningful to substitute a stub type of the correct size.  */
 123   struct type *(*get_base_type) (struct dwarf_expr_context *ctx, size_t die);
 124
 125 #if 0
 126   /* Not yet implemented.  */
 127
 128   /* Return the `object address' for DW_OP_push_object_address.  */
 129   CORE_ADDR (*get_object_address) (void *baton);
 130 #endif
 131
 132   /* The current depth of dwarf expression recursion, via DW_OP_call*,
 133      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
 134      depth we'll tolerate before raising an error.  */
 135   int recursion_depth, max_recursion_depth;
 136
 137   /* Location of the value.  */
 138   enum dwarf_value_location location;
 139
 140   /* For DWARF_VALUE_LITERAL, the current literal value's length and
 141      data.  For DWARF_VALUE_IMPLICIT_POINTER, LEN is the offset of the
 142      target DIE.  */
 143   ULONGEST len;
 144   const gdb_byte *data;
 145
 146   /* Initialization status of variable: Non-zero if variable has been
 147      initialized; zero otherwise.  */
 148   int initialized;
 149
 150   /* An array of pieces.  PIECES points to its first element;
 151      NUM_PIECES is its length.
 152
 153      Each time DW_OP_piece is executed, we add a new element to the
 154      end of this array, recording the current top of the stack, the
 155      current location, and the size given as the operand to
 156      DW_OP_piece.  We then pop the top value from the stack, reset the
 157      location, and resume evaluation.
 158
 159      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
 160      from the stack.  We do, ensuring that clients of this interface
 161      expecting to see a value left on the top of the stack (say, code
 162      evaluating frame base expressions or CFA's specified with
 163      DW_CFA_def_cfa_expression) will get an error if the expression
 164      actually marks all the values it computes as pieces.
 165
 166      If an expression never uses DW_OP_piece, num_pieces will be zero.
 167      (It would be nice to present these cases as expressions yielding
 168      a single piece, so that callers need not distinguish between the
 169      no-DW_OP_piece and one-DW_OP_piece cases.  But expressions with
 170      no DW_OP_piece operations have no value to place in a piece's
 171      'size' field; the size comes from the surrounding data.  So the
 172      two cases need to be handled separately.)  */
 173   int num_pieces;
 174   struct dwarf_expr_piece *pieces;
 175 };
 176
 177
 178 /* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece.  */
 179 struct dwarf_expr_piece
 180 {
 181   enum dwarf_value_location location;
 182
 183   union
 184   {
 185     struct
 186     {
 187       /* This piece's address, for DWARF_VALUE_MEMORY pieces.  */
 188       CORE_ADDR addr;
 189       /* Non-zero if the piece is known to be in memory and on
 190          the program's stack.  */
 191       int in_stack_memory;
 192     } mem;
 193
 194     /* The piece's register number, for DWARF_VALUE_REGISTER pieces.  */
 195     int regno;
 196
 197     /* The piece's literal value, for DWARF_VALUE_STACK pieces.  */
 198     struct value *value;
 199
 200     struct
 201     {
 202       /* A pointer to the data making up this piece,
 203          for DWARF_VALUE_LITERAL pieces.  */
 204       const gdb_byte *data;
 205       /* The length of the available data.  */
 206       ULONGEST length;
 207     } literal;
 208
 209     /* Used for DWARF_VALUE_IMPLICIT_POINTER.  */
 210     struct
 211     {
 212       /* The referent DIE from DW_OP_GNU_implicit_pointer.  */
 213       ULONGEST die;
 214       /* The byte offset into the resulting data.  */
 215       LONGEST offset;
 216     } ptr;
 217   } v;
 218
 219   /* The length of the piece, in bits.  */
 220   ULONGEST size;
 221   /* The piece offset, in bits.  */
 222   ULONGEST offset;
 223 };
 224
 225 struct dwarf_expr_context *new_dwarf_expr_context (void);
 226 void free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 227 struct cleanup *
 228     make_cleanup_free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 229
 230 void dwarf_expr_push_address (struct dwarf_expr_context *ctx,
 231                               CORE_ADDR value,
 232                               int in_stack_memory);
 233 void dwarf_expr_eval (struct dwarf_expr_context *ctx, const gdb_byte *addr,
 234                       size_t len);
 235 struct value *dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n);
 236 CORE_ADDR dwarf_expr_fetch_address (struct dwarf_expr_context *ctx, int n);
 237 int dwarf_expr_fetch_in_stack_memory (struct dwarf_expr_context *ctx, int n);
 238
 239
 240 const gdb_byte *read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 241                               ULONGEST * r);
 242 const gdb_byte *read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 243                               LONGEST * r);
 244
 245 const char *dwarf_stack_op_name (unsigned int);
 246
 247 void dwarf_expr_require_composition (const gdb_byte *, const gdb_byte *,
 248                                      const char *);
 249
 250 #endif /* dwarf2expr.h */