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