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   /* Push on DWARF stack an entry evaluated for DW_TAG_GNU_call_site's
  66      DWARF_REG/FB_OFFSET at the caller of specified BATON.  If DWARF register
  67      number DWARF_REG specifying the push_dwarf_reg_entry_value parameter is
  68      not -1 FB_OFFSET is ignored.  Otherwise FB_OFFSET specifies stack
  69      parameter offset against caller's stack pointer (which equals the callee's
  70      frame base).  */
  71   void (*push_dwarf_reg_entry_value) (struct dwarf_expr_context *ctx,
  72                                       int dwarf_reg, CORE_ADDR fb_offset);
  73
  74 #if 0
  75   /* Not yet implemented.  */
  76
  77   /* Return the `object address' for DW_OP_push_object_address.  */
  78   CORE_ADDR (*get_object_address) (void *baton);
  79 #endif
  80 };
  81
  82 /* The location of a value.  */
  83 enum dwarf_value_location
  84 {
  85   /* The piece is in memory.
  86      The value on the dwarf stack is its address.  */
  87   DWARF_VALUE_MEMORY,
  88
  89   /* The piece is in a register.
  90      The value on the dwarf stack is the register number.  */
  91   DWARF_VALUE_REGISTER,
  92
  93   /* The piece is on the dwarf stack.  */
  94   DWARF_VALUE_STACK,
  95
  96   /* The piece is a literal.  */
  97   DWARF_VALUE_LITERAL,
  98
  99   /* The piece was optimized out.  */
 100   DWARF_VALUE_OPTIMIZED_OUT,
 101
 102   /* The piece is an implicit pointer.  */
 103   DWARF_VALUE_IMPLICIT_POINTER
 104 };
 105
 106 /* The dwarf expression stack.  */
 107
 108 struct dwarf_stack_value
 109 {
 110   struct value *value;
 111
 112   /* Non-zero if the piece is in memory and is known to be
 113      on the program's stack.  It is always ok to set this to zero.
 114      This is used, for example, to optimize memory access from the target.
 115      It can vastly speed up backtraces on long latency connections when
 116      "set stack-cache on".  */
 117   int in_stack_memory;
 118 };
 119
 120 /* The expression evaluator works with a dwarf_expr_context, describing
 121    its current state and its callbacks.  */
 122 struct dwarf_expr_context
 123 {
 124   /* The stack of values, allocated with xmalloc.  */
 125   struct dwarf_stack_value *stack;
 126
 127   /* The number of values currently pushed on the stack, and the
 128      number of elements allocated to the stack.  */
 129   int stack_len, stack_allocated;
 130
 131   /* Target architecture to use for address operations.  */
 132   struct gdbarch *gdbarch;
 133
 134   /* Target address size in bytes.  */
 135   int addr_size;
 136
 137   /* DW_FORM_ref_addr size in bytes.  If -1 DWARF is executed from a frame
 138      context and operations depending on DW_FORM_ref_addr are not allowed.  */
 139   int ref_addr_size;
 140
 141   /* Offset used to relocate DW_OP_addr argument.  */
 142   CORE_ADDR offset;
 143
 144   /* An opaque argument provided by the caller, which will be passed
 145      to all of the callback functions.  */
 146   void *baton;
 147
 148   /* Callback functions.  */
 149   const struct dwarf_expr_context_funcs *funcs;
 150
 151   /* The current depth of dwarf expression recursion, via DW_OP_call*,
 152      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
 153      depth we'll tolerate before raising an error.  */
 154   int recursion_depth, max_recursion_depth;
 155
 156   /* Location of the value.  */
 157   enum dwarf_value_location location;
 158
 159   /* For DWARF_VALUE_LITERAL, the current literal value's length and
 160      data.  For DWARF_VALUE_IMPLICIT_POINTER, LEN is the offset of the
 161      target DIE.  */
 162   ULONGEST len;
 163   const gdb_byte *data;
 164
 165   /* Initialization status of variable: Non-zero if variable has been
 166      initialized; zero otherwise.  */
 167   int initialized;
 168
 169   /* An array of pieces.  PIECES points to its first element;
 170      NUM_PIECES is its length.
 171
 172      Each time DW_OP_piece is executed, we add a new element to the
 173      end of this array, recording the current top of the stack, the
 174      current location, and the size given as the operand to
 175      DW_OP_piece.  We then pop the top value from the stack, reset the
 176      location, and resume evaluation.
 177
 178      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
 179      from the stack.  We do, ensuring that clients of this interface
 180      expecting to see a value left on the top of the stack (say, code
 181      evaluating frame base expressions or CFA's specified with
 182      DW_CFA_def_cfa_expression) will get an error if the expression
 183      actually marks all the values it computes as pieces.
 184
 185      If an expression never uses DW_OP_piece, num_pieces will be zero.
 186      (It would be nice to present these cases as expressions yielding
 187      a single piece, so that callers need not distinguish between the
 188      no-DW_OP_piece and one-DW_OP_piece cases.  But expressions with
 189      no DW_OP_piece operations have no value to place in a piece's
 190      'size' field; the size comes from the surrounding data.  So the
 191      two cases need to be handled separately.)  */
 192   int num_pieces;
 193   struct dwarf_expr_piece *pieces;
 194 };
 195
 196
 197 /* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece.  */
 198 struct dwarf_expr_piece
 199 {
 200   enum dwarf_value_location location;
 201
 202   union
 203   {
 204     struct
 205     {
 206       /* This piece's address, for DWARF_VALUE_MEMORY pieces.  */
 207       CORE_ADDR addr;
 208       /* Non-zero if the piece is known to be in memory and on
 209          the program's stack.  */
 210       int in_stack_memory;
 211     } mem;
 212
 213     /* The piece's register number, for DWARF_VALUE_REGISTER pieces.  */
 214     int regno;
 215
 216     /* The piece's literal value, for DWARF_VALUE_STACK pieces.  */
 217     struct value *value;
 218
 219     struct
 220     {
 221       /* A pointer to the data making up this piece,
 222          for DWARF_VALUE_LITERAL pieces.  */
 223       const gdb_byte *data;
 224       /* The length of the available data.  */
 225       ULONGEST length;
 226     } literal;
 227
 228     /* Used for DWARF_VALUE_IMPLICIT_POINTER.  */
 229     struct
 230     {
 231       /* The referent DIE from DW_OP_GNU_implicit_pointer.  */
 232       ULONGEST die;
 233       /* The byte offset into the resulting data.  */
 234       LONGEST offset;
 235     } ptr;
 236   } v;
 237
 238   /* The length of the piece, in bits.  */
 239   ULONGEST size;
 240   /* The piece offset, in bits.  */
 241   ULONGEST offset;
 242 };
 243
 244 struct dwarf_expr_context *new_dwarf_expr_context (void);
 245 void free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 246 struct cleanup *
 247     make_cleanup_free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 248
 249 void dwarf_expr_push_address (struct dwarf_expr_context *ctx,
 250                               CORE_ADDR value,
 251                               int in_stack_memory);
 252 void dwarf_expr_eval (struct dwarf_expr_context *ctx, const gdb_byte *addr,
 253                       size_t len);
 254 struct value *dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n);
 255 CORE_ADDR dwarf_expr_fetch_address (struct dwarf_expr_context *ctx, int n);
 256 int dwarf_expr_fetch_in_stack_memory (struct dwarf_expr_context *ctx, int n);
 257
 258
 259 const gdb_byte *read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 260                               ULONGEST * r);
 261 const gdb_byte *read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 262                               LONGEST * r);
 263
 264 const char *dwarf_stack_op_name (unsigned int);
 265
 266 void dwarf_expr_require_composition (const gdb_byte *, const gdb_byte *,
 267                                      const char *);
 268
 269 /* Stub dwarf_expr_context_funcs implementations.  */
 270
 271 CORE_ADDR ctx_no_read_reg (void *baton, int regnum);
 272 void ctx_no_get_frame_base (void *baton, const gdb_byte **start,
 273                             size_t *length);
 274 CORE_ADDR ctx_no_get_frame_cfa (void *baton);
 275 CORE_ADDR ctx_no_get_frame_pc (void *baton);
 276 CORE_ADDR ctx_no_get_tls_address (void *baton, CORE_ADDR offset);
 277 void ctx_no_dwarf_call (struct dwarf_expr_context *ctx, size_t die_offset);
 278 struct type *ctx_no_get_base_type (struct dwarf_expr_context *ctx, size_t die);
 279 void ctx_no_push_dwarf_reg_entry_value (struct dwarf_expr_context *ctx,
 280                                         int dwarf_reg, CORE_ADDR fb_offset);
 281
 282 int dwarf_block_to_dwarf_reg (const gdb_byte *buf, const gdb_byte *buf_end);
 283
 284 int dwarf_block_to_fb_offset (const gdb_byte *buf, const gdb_byte *buf_end,
 285                               CORE_ADDR *fb_offset_return);
 286
 287 int dwarf_block_to_sp_offset (struct gdbarch *gdbarch, const gdb_byte *buf,
 288                               const gdb_byte *buf_end,
 289                               CORE_ADDR *sp_offset_return);
 290
 291 #endif /* dwarf2expr.h */