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 struct dwarf_expr_context;
  27
  28 /* Virtual method table for struct dwarf_expr_context below.  */
  29
  30 struct dwarf_expr_context_funcs
  31 {
  32   /* Return the value of register number REGNUM.  */
  33   CORE_ADDR (*read_reg) (void *baton, int regnum);
  34
  35   /* Read LENGTH bytes at ADDR into BUF.  */
  36   void (*read_mem) (void *baton, gdb_byte *buf, CORE_ADDR addr, size_t length);
  37
  38   /* Return the location expression for the frame base attribute, in
  39      START and LENGTH.  The result must be live until the current
  40      expression evaluation is complete.  */
  41   void (*get_frame_base) (void *baton, const gdb_byte **start, size_t *length);
  42
  43   /* Return the CFA for the frame.  */
  44   CORE_ADDR (*get_frame_cfa) (void *baton);
  45
  46   /* Return the PC for the frame.  */
  47   CORE_ADDR (*get_frame_pc) (void *baton);
  48
  49   /* Return the thread-local storage address for
  50      DW_OP_GNU_push_tls_address.  */
  51   CORE_ADDR (*get_tls_address) (void *baton, CORE_ADDR offset);
  52
  53   /* Execute DW_AT_location expression for the DWARF expression subroutine in
  54      the DIE at DIE_OFFSET in the CU from CTX.  Do not touch STACK while it
  55      being passed to and returned from the called DWARF subroutine.  */
  56   void (*dwarf_call) (struct dwarf_expr_context *ctx, size_t die_offset);
  57
  58   /* Return the base type given by the indicated DIE.  This can throw
  59      an exception if the DIE is invalid or does not represent a base
  60      type.  If can also be NULL in the special case where the
  61      callbacks are not performing evaluation, and thus it is
  62      meaningful to substitute a stub type of the correct size.  */
  63   struct type *(*get_base_type) (struct dwarf_expr_context *ctx, size_t die);
  64
  65 #if 0
  66   /* Not yet implemented.  */
  67
  68   /* Return the `object address' for DW_OP_push_object_address.  */
  69   CORE_ADDR (*get_object_address) (void *baton);
  70 #endif
  71 };
  72
  73 /* The location of a value.  */
  74 enum dwarf_value_location
  75 {
  76   /* The piece is in memory.
  77      The value on the dwarf stack is its address.  */
  78   DWARF_VALUE_MEMORY,
  79
  80   /* The piece is in a register.
  81      The value on the dwarf stack is the register number.  */
  82   DWARF_VALUE_REGISTER,
  83
  84   /* The piece is on the dwarf stack.  */
  85   DWARF_VALUE_STACK,
  86
  87   /* The piece is a literal.  */
  88   DWARF_VALUE_LITERAL,
  89
  90   /* The piece was optimized out.  */
  91   DWARF_VALUE_OPTIMIZED_OUT,
  92
  93   /* The piece is an implicit pointer.  */
  94   DWARF_VALUE_IMPLICIT_POINTER
  95 };
  96
  97 /* The dwarf expression stack.  */
  98
  99 struct dwarf_stack_value
 100 {
 101   struct value *value;
 102
 103   /* Non-zero if the piece is in memory and is known to be
 104      on the program's stack.  It is always ok to set this to zero.
 105      This is used, for example, to optimize memory access from the target.
 106      It can vastly speed up backtraces on long latency connections when
 107      "set stack-cache on".  */
 108   int in_stack_memory;
 109 };
 110
 111 /* The expression evaluator works with a dwarf_expr_context, describing
 112    its current state and its callbacks.  */
 113 struct dwarf_expr_context
 114 {
 115   /* The stack of values, allocated with xmalloc.  */
 116   struct dwarf_stack_value *stack;
 117
 118   /* The number of values currently pushed on the stack, and the
 119      number of elements allocated to the stack.  */
 120   int stack_len, stack_allocated;
 121
 122   /* Target architecture to use for address operations.  */
 123   struct gdbarch *gdbarch;
 124
 125   /* Target address size in bytes.  */
 126   int addr_size;
 127
 128   /* Offset used to relocate DW_OP_addr argument.  */
 129   CORE_ADDR offset;
 130
 131   /* An opaque argument provided by the caller, which will be passed
 132      to all of the callback functions.  */
 133   void *baton;
 134
 135   /* Callback functions.  */
 136   const struct dwarf_expr_context_funcs *funcs;
 137
 138   /* The current depth of dwarf expression recursion, via DW_OP_call*,
 139      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
 140      depth we'll tolerate before raising an error.  */
 141   int recursion_depth, max_recursion_depth;
 142
 143   /* Location of the value.  */
 144   enum dwarf_value_location location;
 145
 146   /* For DWARF_VALUE_LITERAL, the current literal value's length and
 147      data.  For DWARF_VALUE_IMPLICIT_POINTER, LEN is the offset of the
 148      target DIE.  */
 149   ULONGEST len;
 150   const gdb_byte *data;
 151
 152   /* Initialization status of variable: Non-zero if variable has been
 153      initialized; zero otherwise.  */
 154   int initialized;
 155
 156   /* An array of pieces.  PIECES points to its first element;
 157      NUM_PIECES is its length.
 158
 159      Each time DW_OP_piece is executed, we add a new element to the
 160      end of this array, recording the current top of the stack, the
 161      current location, and the size given as the operand to
 162      DW_OP_piece.  We then pop the top value from the stack, reset the
 163      location, and resume evaluation.
 164
 165      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
 166      from the stack.  We do, ensuring that clients of this interface
 167      expecting to see a value left on the top of the stack (say, code
 168      evaluating frame base expressions or CFA's specified with
 169      DW_CFA_def_cfa_expression) will get an error if the expression
 170      actually marks all the values it computes as pieces.
 171
 172      If an expression never uses DW_OP_piece, num_pieces will be zero.
 173      (It would be nice to present these cases as expressions yielding
 174      a single piece, so that callers need not distinguish between the
 175      no-DW_OP_piece and one-DW_OP_piece cases.  But expressions with
 176      no DW_OP_piece operations have no value to place in a piece's
 177      'size' field; the size comes from the surrounding data.  So the
 178      two cases need to be handled separately.)  */
 179   int num_pieces;
 180   struct dwarf_expr_piece *pieces;
 181 };
 182
 183
 184 /* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece.  */
 185 struct dwarf_expr_piece
 186 {
 187   enum dwarf_value_location location;
 188
 189   union
 190   {
 191     struct
 192     {
 193       /* This piece's address, for DWARF_VALUE_MEMORY pieces.  */
 194       CORE_ADDR addr;
 195       /* Non-zero if the piece is known to be in memory and on
 196          the program's stack.  */
 197       int in_stack_memory;
 198     } mem;
 199
 200     /* The piece's register number, for DWARF_VALUE_REGISTER pieces.  */
 201     int regno;
 202
 203     /* The piece's literal value, for DWARF_VALUE_STACK pieces.  */
 204     struct value *value;
 205
 206     struct
 207     {
 208       /* A pointer to the data making up this piece,
 209          for DWARF_VALUE_LITERAL pieces.  */
 210       const gdb_byte *data;
 211       /* The length of the available data.  */
 212       ULONGEST length;
 213     } literal;
 214
 215     /* Used for DWARF_VALUE_IMPLICIT_POINTER.  */
 216     struct
 217     {
 218       /* The referent DIE from DW_OP_GNU_implicit_pointer.  */
 219       ULONGEST die;
 220       /* The byte offset into the resulting data.  */
 221       LONGEST offset;
 222     } ptr;
 223   } v;
 224
 225   /* The length of the piece, in bits.  */
 226   ULONGEST size;
 227   /* The piece offset, in bits.  */
 228   ULONGEST offset;
 229 };
 230
 231 struct dwarf_expr_context *new_dwarf_expr_context (void);
 232 void free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 233 struct cleanup *
 234     make_cleanup_free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 235
 236 void dwarf_expr_push_address (struct dwarf_expr_context *ctx,
 237                               CORE_ADDR value,
 238                               int in_stack_memory);
 239 void dwarf_expr_eval (struct dwarf_expr_context *ctx, const gdb_byte *addr,
 240                       size_t len);
 241 struct value *dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n);
 242 CORE_ADDR dwarf_expr_fetch_address (struct dwarf_expr_context *ctx, int n);
 243 int dwarf_expr_fetch_in_stack_memory (struct dwarf_expr_context *ctx, int n);
 244
 245
 246 const gdb_byte *read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 247                               ULONGEST * r);
 248 const gdb_byte *read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 249                               LONGEST * r);
 250
 251 const char *dwarf_stack_op_name (unsigned int);
 252
 253 void dwarf_expr_require_composition (const gdb_byte *, const gdb_byte *,
 254                                      const char *);
 255
 256 /* Stub dwarf_expr_context_funcs implementations.  */
 257
 258 CORE_ADDR ctx_no_read_reg (void *baton, int regnum);
 259 void ctx_no_get_frame_base (void *baton, const gdb_byte **start,
 260                             size_t *length);
 261 CORE_ADDR ctx_no_get_frame_cfa (void *baton);
 262 CORE_ADDR ctx_no_get_frame_pc (void *baton);
 263 CORE_ADDR ctx_no_get_tls_address (void *baton, CORE_ADDR offset);
 264 void ctx_no_dwarf_call (struct dwarf_expr_context *ctx, size_t die_offset);
 265 struct type *ctx_no_get_base_type (struct dwarf_expr_context *ctx, size_t die);
 266
 267 #endif /* dwarf2expr.h */