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
  44 /* The dwarf expression stack.  */
  45
  46 struct dwarf_stack_value
  47 {
  48   CORE_ADDR value;
  49
  50   /* Non-zero if the piece is in memory and is known to be
  51      on the program's stack.  It is always ok to set this to zero.
  52      This is used, for example, to optimize memory access from the target.
  53      It can vastly speed up backtraces on long latency connections when
  54      "set stack-cache on".  */
  55   int in_stack_memory;
  56 };
  57
  58 /* The expression evaluator works with a dwarf_expr_context, describing
  59    its current state and its callbacks.  */
  60 struct dwarf_expr_context
  61 {
  62   /* The stack of values, allocated with xmalloc.  */
  63   struct dwarf_stack_value *stack;
  64
  65   /* The number of values currently pushed on the stack, and the
  66      number of elements allocated to the stack.  */
  67   int stack_len, stack_allocated;
  68
  69   /* Target architecture to use for address operations.  */
  70   struct gdbarch *gdbarch;
  71
  72   /* Target address size in bytes.  */
  73   int addr_size;
  74
  75   /* An opaque argument provided by the caller, which will be passed
  76      to all of the callback functions.  */
  77   void *baton;
  78
  79   /* Return the value of register number REGNUM.  */
  80   CORE_ADDR (*read_reg) (void *baton, int regnum);
  81
  82   /* Read LENGTH bytes at ADDR into BUF.  */
  83   void (*read_mem) (void *baton, gdb_byte *buf, CORE_ADDR addr, size_t length);
  84
  85   /* Return the location expression for the frame base attribute, in
  86      START and LENGTH.  The result must be live until the current
  87      expression evaluation is complete.  */
  88   void (*get_frame_base) (void *baton, gdb_byte **start, size_t *length);
  89
  90   /* Return the CFA for the frame.  */
  91   CORE_ADDR (*get_frame_cfa) (void *baton);
  92
  93   /* Return the thread-local storage address for
  94      DW_OP_GNU_push_tls_address.  */
  95   CORE_ADDR (*get_tls_address) (void *baton, CORE_ADDR offset);
  96
  97 #if 0
  98   /* Not yet implemented.  */
  99
 100   /* Return the location expression for the dwarf expression
 101      subroutine in the die at OFFSET in the current compilation unit.
 102      The result must be live until the current expression evaluation
 103      is complete.  */
 104   unsigned char *(*get_subr) (void *baton, off_t offset, size_t *length);
 105
 106   /* Return the `object address' for DW_OP_push_object_address.  */
 107   CORE_ADDR (*get_object_address) (void *baton);
 108 #endif
 109
 110   /* The current depth of dwarf expression recursion, via DW_OP_call*,
 111      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
 112      depth we'll tolerate before raising an error.  */
 113   int recursion_depth, max_recursion_depth;
 114
 115   /* Location of the value.  */
 116   enum dwarf_value_location location;
 117
 118   /* For VALUE_LITERAL, a the current literal value's length and
 119      data.  */
 120   ULONGEST len;
 121   gdb_byte *data;
 122
 123   /* Initialization status of variable: Non-zero if variable has been
 124      initialized; zero otherwise.  */
 125   int initialized;
 126
 127   /* An array of pieces.  PIECES points to its first element;
 128      NUM_PIECES is its length.
 129
 130      Each time DW_OP_piece is executed, we add a new element to the
 131      end of this array, recording the current top of the stack, the
 132      current location, and the size given as the operand to
 133      DW_OP_piece.  We then pop the top value from the stack, reset the
 134      location, and resume evaluation.
 135
 136      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
 137      from the stack.  We do, ensuring that clients of this interface
 138      expecting to see a value left on the top of the stack (say, code
 139      evaluating frame base expressions or CFA's specified with
 140      DW_CFA_def_cfa_expression) will get an error if the expression
 141      actually marks all the values it computes as pieces.
 142
 143      If an expression never uses DW_OP_piece, num_pieces will be zero.
 144      (It would be nice to present these cases as expressions yielding
 145      a single piece, so that callers need not distinguish between the
 146      no-DW_OP_piece and one-DW_OP_piece cases.  But expressions with
 147      no DW_OP_piece operations have no value to place in a piece's
 148      'size' field; the size comes from the surrounding data.  So the
 149      two cases need to be handled separately.)  */
 150   int num_pieces;
 151   struct dwarf_expr_piece *pieces;
 152 };
 153
 154
 155 /* A piece of an object, as recorded by DW_OP_piece.  */
 156 struct dwarf_expr_piece
 157 {
 158   enum dwarf_value_location location;
 159
 160   union
 161   {
 162     struct
 163     {
 164       /* This piece's address or register number.  */
 165       CORE_ADDR value;
 166       /* Non-zero if the piece is known to be in memory and on
 167          the program's stack.  */
 168       int in_stack_memory;
 169     } expr;
 170
 171     struct
 172     {
 173       /* A pointer to the data making up this piece, for literal
 174          pieces.  */
 175       gdb_byte *data;
 176       /* The length of the available data.  */
 177       ULONGEST length;
 178     } literal;
 179   } v;
 180
 181   /* The length of the piece, in bytes.  */
 182   ULONGEST size;
 183 };
 184
 185 struct dwarf_expr_context *new_dwarf_expr_context (void);
 186 void free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 187 struct cleanup *
 188     make_cleanup_free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 189
 190 void dwarf_expr_push (struct dwarf_expr_context *ctx, CORE_ADDR value,
 191                       int in_stack_memory);
 192 void dwarf_expr_pop (struct dwarf_expr_context *ctx);
 193 void dwarf_expr_eval (struct dwarf_expr_context *ctx, unsigned char *addr,
 194                       size_t len);
 195 CORE_ADDR dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n);
 196 int dwarf_expr_fetch_in_stack_memory (struct dwarf_expr_context *ctx, int n);
 197
 198
 199 gdb_byte *read_uleb128 (gdb_byte *buf, gdb_byte *buf_end, ULONGEST * r);
 200 gdb_byte *read_sleb128 (gdb_byte *buf, gdb_byte *buf_end, LONGEST * r);
 201 CORE_ADDR dwarf2_read_address (struct gdbarch *gdbarch, gdb_byte *buf,
 202                                gdb_byte *buf_end, int addr_size);
 203
 204 #endif /* dwarf2expr.h */