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, const 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   /* Execute DW_AT_location expression for the DWARF expression subroutine in
 101      the DIE at DIE_OFFSET in the CU from CTX.  Do not touch STACK while it
 102      being passed to and returned from the called DWARF subroutine.  */
 103   void (*dwarf_call) (struct dwarf_expr_context *ctx, size_t die_offset);
 104
 105 #if 0
 106   /* Not yet implemented.  */
 107
 108   /* Return the `object address' for DW_OP_push_object_address.  */
 109   CORE_ADDR (*get_object_address) (void *baton);
 110 #endif
 111
 112   /* The current depth of dwarf expression recursion, via DW_OP_call*,
 113      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
 114      depth we'll tolerate before raising an error.  */
 115   int recursion_depth, max_recursion_depth;
 116
 117   /* Location of the value.  */
 118   enum dwarf_value_location location;
 119
 120   /* For VALUE_LITERAL, a the current literal value's length and
 121      data.  */
 122   ULONGEST len;
 123   const gdb_byte *data;
 124
 125   /* Initialization status of variable: Non-zero if variable has been
 126      initialized; zero otherwise.  */
 127   int initialized;
 128
 129   /* An array of pieces.  PIECES points to its first element;
 130      NUM_PIECES is its length.
 131
 132      Each time DW_OP_piece is executed, we add a new element to the
 133      end of this array, recording the current top of the stack, the
 134      current location, and the size given as the operand to
 135      DW_OP_piece.  We then pop the top value from the stack, reset the
 136      location, and resume evaluation.
 137
 138      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
 139      from the stack.  We do, ensuring that clients of this interface
 140      expecting to see a value left on the top of the stack (say, code
 141      evaluating frame base expressions or CFA's specified with
 142      DW_CFA_def_cfa_expression) will get an error if the expression
 143      actually marks all the values it computes as pieces.
 144
 145      If an expression never uses DW_OP_piece, num_pieces will be zero.
 146      (It would be nice to present these cases as expressions yielding
 147      a single piece, so that callers need not distinguish between the
 148      no-DW_OP_piece and one-DW_OP_piece cases.  But expressions with
 149      no DW_OP_piece operations have no value to place in a piece's
 150      'size' field; the size comes from the surrounding data.  So the
 151      two cases need to be handled separately.)  */
 152   int num_pieces;
 153   struct dwarf_expr_piece *pieces;
 154 };
 155
 156
 157 /* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece.  */
 158 struct dwarf_expr_piece
 159 {
 160   enum dwarf_value_location location;
 161
 162   union
 163   {
 164     struct
 165     {
 166       /* This piece's address or register number.  */
 167       CORE_ADDR value;
 168       /* Non-zero if the piece is known to be in memory and on
 169          the program's stack.  */
 170       int in_stack_memory;
 171     } expr;
 172
 173     struct
 174     {
 175       /* A pointer to the data making up this piece, for literal
 176          pieces.  */
 177       const gdb_byte *data;
 178       /* The length of the available data.  */
 179       ULONGEST length;
 180     } literal;
 181   } v;
 182
 183   /* The length of the piece, in bits.  */
 184   ULONGEST size;
 185   /* The piece offset, in bits.  */
 186   ULONGEST offset;
 187 };
 188
 189 struct dwarf_expr_context *new_dwarf_expr_context (void);
 190 void free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 191 struct cleanup *
 192     make_cleanup_free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 193
 194 void dwarf_expr_push (struct dwarf_expr_context *ctx, CORE_ADDR value,
 195                       int in_stack_memory);
 196 void dwarf_expr_pop (struct dwarf_expr_context *ctx);
 197 void dwarf_expr_eval (struct dwarf_expr_context *ctx, const gdb_byte *addr,
 198                       size_t len);
 199 CORE_ADDR dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n);
 200 int dwarf_expr_fetch_in_stack_memory (struct dwarf_expr_context *ctx, int n);
 201
 202
 203 const gdb_byte *read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 204                               ULONGEST * r);
 205 const gdb_byte *read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 206                               LONGEST * r);
 207 CORE_ADDR dwarf2_read_address (struct gdbarch *gdbarch, const gdb_byte *buf,
 208                                const gdb_byte *buf_end, int addr_size);
 209
 210 const char *dwarf_stack_op_name (unsigned int, int);
 211
 212 #endif /* dwarf2expr.h */