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   ULONGEST 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   /* Offset used to relocate DW_OP_addr argument.  */
  79   CORE_ADDR offset;
  80
  81   /* An opaque argument provided by the caller, which will be passed
  82      to all of the callback functions.  */
  83   void *baton;
  84
  85   /* Return the value of register number REGNUM.  */
  86   CORE_ADDR (*read_reg) (void *baton, int regnum);
  87
  88   /* Read LENGTH bytes at ADDR into BUF.  */
  89   void (*read_mem) (void *baton, gdb_byte *buf, CORE_ADDR addr, size_t length);
  90
  91   /* Return the location expression for the frame base attribute, in
  92      START and LENGTH.  The result must be live until the current
  93      expression evaluation is complete.  */
  94   void (*get_frame_base) (void *baton, const gdb_byte **start, size_t *length);
  95
  96   /* Return the CFA for the frame.  */
  97   CORE_ADDR (*get_frame_cfa) (void *baton);
  98
  99   /* Return the thread-local storage address for
 100      DW_OP_GNU_push_tls_address.  */
 101   CORE_ADDR (*get_tls_address) (void *baton, CORE_ADDR offset);
 102
 103   /* Execute DW_AT_location expression for the DWARF expression subroutine in
 104      the DIE at DIE_OFFSET in the CU from CTX.  Do not touch STACK while it
 105      being passed to and returned from the called DWARF subroutine.  */
 106   void (*dwarf_call) (struct dwarf_expr_context *ctx, size_t die_offset);
 107
 108 #if 0
 109   /* Not yet implemented.  */
 110
 111   /* Return the `object address' for DW_OP_push_object_address.  */
 112   CORE_ADDR (*get_object_address) (void *baton);
 113 #endif
 114
 115   /* The current depth of dwarf expression recursion, via DW_OP_call*,
 116      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
 117      depth we'll tolerate before raising an error.  */
 118   int recursion_depth, max_recursion_depth;
 119
 120   /* Location of the value.  */
 121   enum dwarf_value_location location;
 122
 123   /* For VALUE_LITERAL, a the current literal value's length and
 124      data.  */
 125   ULONGEST len;
 126   const gdb_byte *data;
 127
 128   /* Initialization status of variable: Non-zero if variable has been
 129      initialized; zero otherwise.  */
 130   int initialized;
 131
 132   /* An array of pieces.  PIECES points to its first element;
 133      NUM_PIECES is its length.
 134
 135      Each time DW_OP_piece is executed, we add a new element to the
 136      end of this array, recording the current top of the stack, the
 137      current location, and the size given as the operand to
 138      DW_OP_piece.  We then pop the top value from the stack, reset the
 139      location, and resume evaluation.
 140
 141      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
 142      from the stack.  We do, ensuring that clients of this interface
 143      expecting to see a value left on the top of the stack (say, code
 144      evaluating frame base expressions or CFA's specified with
 145      DW_CFA_def_cfa_expression) will get an error if the expression
 146      actually marks all the values it computes as pieces.
 147
 148      If an expression never uses DW_OP_piece, num_pieces will be zero.
 149      (It would be nice to present these cases as expressions yielding
 150      a single piece, so that callers need not distinguish between the
 151      no-DW_OP_piece and one-DW_OP_piece cases.  But expressions with
 152      no DW_OP_piece operations have no value to place in a piece's
 153      'size' field; the size comes from the surrounding data.  So the
 154      two cases need to be handled separately.)  */
 155   int num_pieces;
 156   struct dwarf_expr_piece *pieces;
 157 };
 158
 159
 160 /* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece.  */
 161 struct dwarf_expr_piece
 162 {
 163   enum dwarf_value_location location;
 164
 165   union
 166   {
 167     struct
 168     {
 169       /* This piece's address, for DWARF_VALUE_MEMORY pieces.  */
 170       CORE_ADDR addr;
 171       /* Non-zero if the piece is known to be in memory and on
 172          the program's stack.  */
 173       int in_stack_memory;
 174     } mem;
 175
 176     /* The piece's register number or literal value, for
 177        DWARF_VALUE_REGISTER or DWARF_VALUE_STACK pieces.  */
 178     ULONGEST value;
 179
 180     struct
 181     {
 182       /* A pointer to the data making up this piece,
 183          for DWARF_VALUE_LITERAL pieces.  */
 184       const gdb_byte *data;
 185       /* The length of the available data.  */
 186       ULONGEST length;
 187     } literal;
 188   } v;
 189
 190   /* The length of the piece, in bits.  */
 191   ULONGEST size;
 192   /* The piece offset, in bits.  */
 193   ULONGEST offset;
 194 };
 195
 196 struct dwarf_expr_context *new_dwarf_expr_context (void);
 197 void free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 198 struct cleanup *
 199     make_cleanup_free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 200
 201 void dwarf_expr_push (struct dwarf_expr_context *ctx, ULONGEST value,
 202                       int in_stack_memory);
 203 void dwarf_expr_pop (struct dwarf_expr_context *ctx);
 204 void dwarf_expr_eval (struct dwarf_expr_context *ctx, const gdb_byte *addr,
 205                       size_t len);
 206 ULONGEST dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n);
 207 CORE_ADDR dwarf_expr_fetch_address (struct dwarf_expr_context *ctx, int n);
 208 int dwarf_expr_fetch_in_stack_memory (struct dwarf_expr_context *ctx, int n);
 209
 210
 211 const gdb_byte *read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 212                               ULONGEST * r);
 213 const gdb_byte *read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 214                               LONGEST * r);
 215
 216 const char *dwarf_stack_op_name (unsigned int, int);
 217
 218 void dwarf_expr_require_composition (const gdb_byte *, const gdb_byte *,
 219                                      const char *);
 220
 221 #endif /* dwarf2expr.h */