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   /* DW_FORM_ref_addr size in bytes.  If -1 DWARF is executed from a frame
 129      context and operations depending on DW_FORM_ref_addr are not allowed.  */
 130   int ref_addr_size;
 131
 132   /* Offset used to relocate DW_OP_addr argument.  */
 133   CORE_ADDR offset;
 134
 135   /* An opaque argument provided by the caller, which will be passed
 136      to all of the callback functions.  */
 137   void *baton;
 138
 139   /* Callback functions.  */
 140   const struct dwarf_expr_context_funcs *funcs;
 141
 142   /* The current depth of dwarf expression recursion, via DW_OP_call*,
 143      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
 144      depth we'll tolerate before raising an error.  */
 145   int recursion_depth, max_recursion_depth;
 146
 147   /* Location of the value.  */
 148   enum dwarf_value_location location;
 149
 150   /* For DWARF_VALUE_LITERAL, the current literal value's length and
 151      data.  For DWARF_VALUE_IMPLICIT_POINTER, LEN is the offset of the
 152      target DIE.  */
 153   ULONGEST len;
 154   const gdb_byte *data;
 155
 156   /* Initialization status of variable: Non-zero if variable has been
 157      initialized; zero otherwise.  */
 158   int initialized;
 159
 160   /* An array of pieces.  PIECES points to its first element;
 161      NUM_PIECES is its length.
 162
 163      Each time DW_OP_piece is executed, we add a new element to the
 164      end of this array, recording the current top of the stack, the
 165      current location, and the size given as the operand to
 166      DW_OP_piece.  We then pop the top value from the stack, reset the
 167      location, and resume evaluation.
 168
 169      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
 170      from the stack.  We do, ensuring that clients of this interface
 171      expecting to see a value left on the top of the stack (say, code
 172      evaluating frame base expressions or CFA's specified with
 173      DW_CFA_def_cfa_expression) will get an error if the expression
 174      actually marks all the values it computes as pieces.
 175
 176      If an expression never uses DW_OP_piece, num_pieces will be zero.
 177      (It would be nice to present these cases as expressions yielding
 178      a single piece, so that callers need not distinguish between the
 179      no-DW_OP_piece and one-DW_OP_piece cases.  But expressions with
 180      no DW_OP_piece operations have no value to place in a piece's
 181      'size' field; the size comes from the surrounding data.  So the
 182      two cases need to be handled separately.)  */
 183   int num_pieces;
 184   struct dwarf_expr_piece *pieces;
 185 };
 186
 187
 188 /* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece.  */
 189 struct dwarf_expr_piece
 190 {
 191   enum dwarf_value_location location;
 192
 193   union
 194   {
 195     struct
 196     {
 197       /* This piece's address, for DWARF_VALUE_MEMORY pieces.  */
 198       CORE_ADDR addr;
 199       /* Non-zero if the piece is known to be in memory and on
 200          the program's stack.  */
 201       int in_stack_memory;
 202     } mem;
 203
 204     /* The piece's register number, for DWARF_VALUE_REGISTER pieces.  */
 205     int regno;
 206
 207     /* The piece's literal value, for DWARF_VALUE_STACK pieces.  */
 208     struct value *value;
 209
 210     struct
 211     {
 212       /* A pointer to the data making up this piece,
 213          for DWARF_VALUE_LITERAL pieces.  */
 214       const gdb_byte *data;
 215       /* The length of the available data.  */
 216       ULONGEST length;
 217     } literal;
 218
 219     /* Used for DWARF_VALUE_IMPLICIT_POINTER.  */
 220     struct
 221     {
 222       /* The referent DIE from DW_OP_GNU_implicit_pointer.  */
 223       ULONGEST die;
 224       /* The byte offset into the resulting data.  */
 225       LONGEST offset;
 226     } ptr;
 227   } v;
 228
 229   /* The length of the piece, in bits.  */
 230   ULONGEST size;
 231   /* The piece offset, in bits.  */
 232   ULONGEST offset;
 233 };
 234
 235 struct dwarf_expr_context *new_dwarf_expr_context (void);
 236 void free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 237 struct cleanup *
 238     make_cleanup_free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 239
 240 void dwarf_expr_push_address (struct dwarf_expr_context *ctx,
 241                               CORE_ADDR value,
 242                               int in_stack_memory);
 243 void dwarf_expr_eval (struct dwarf_expr_context *ctx, const gdb_byte *addr,
 244                       size_t len);
 245 struct value *dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n);
 246 CORE_ADDR dwarf_expr_fetch_address (struct dwarf_expr_context *ctx, int n);
 247 int dwarf_expr_fetch_in_stack_memory (struct dwarf_expr_context *ctx, int n);
 248
 249
 250 const gdb_byte *read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 251                               ULONGEST * r);
 252 const gdb_byte *read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 253                               LONGEST * r);
 254
 255 const char *dwarf_stack_op_name (unsigned int);
 256
 257 void dwarf_expr_require_composition (const gdb_byte *, const gdb_byte *,
 258                                      const char *);
 259
 260 /* Stub dwarf_expr_context_funcs implementations.  */
 261
 262 CORE_ADDR ctx_no_read_reg (void *baton, int regnum);
 263 void ctx_no_get_frame_base (void *baton, const gdb_byte **start,
 264                             size_t *length);
 265 CORE_ADDR ctx_no_get_frame_cfa (void *baton);
 266 CORE_ADDR ctx_no_get_frame_pc (void *baton);
 267 CORE_ADDR ctx_no_get_tls_address (void *baton, CORE_ADDR offset);
 268 void ctx_no_dwarf_call (struct dwarf_expr_context *ctx, size_t die_offset);
 269 struct type *ctx_no_get_base_type (struct dwarf_expr_context *ctx, size_t die);
 270
 271 #endif /* dwarf2expr.h */