gdb/dwarf2expr.h

   1 /* DWARF 2 Expression Evaluator.
   2
   3    Copyright (C) 2001-2003, 2005, 2007-2012 Free Software Foundation,
   4    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 /* Offset relative to the start of its containing CU (compilation unit).  */
  29 typedef struct
  30 {
  31   unsigned int cu_off;
  32 } cu_offset;
  33
  34 /* Offset relative to the start of its .debug_info or .debug_types section.  */
  35 typedef struct
  36 {
  37   unsigned int sect_off;
  38 } sect_offset;
  39
  40 /* Virtual method table for struct dwarf_expr_context below.  */
  41
  42 struct dwarf_expr_context_funcs
  43 {
  44   /* Return the value of register number REGNUM.  */
  45   CORE_ADDR (*read_reg) (void *baton, int regnum);
  46
  47   /* Read LENGTH bytes at ADDR into BUF.  */
  48   void (*read_mem) (void *baton, gdb_byte *buf, CORE_ADDR addr, size_t length);
  49
  50   /* Return the location expression for the frame base attribute, in
  51      START and LENGTH.  The result must be live until the current
  52      expression evaluation is complete.  */
  53   void (*get_frame_base) (void *baton, const gdb_byte **start, size_t *length);
  54
  55   /* Return the CFA for the frame.  */
  56   CORE_ADDR (*get_frame_cfa) (void *baton);
  57
  58   /* Return the PC for the frame.  */
  59   CORE_ADDR (*get_frame_pc) (void *baton);
  60
  61   /* Return the thread-local storage address for
  62      DW_OP_GNU_push_tls_address.  */
  63   CORE_ADDR (*get_tls_address) (void *baton, CORE_ADDR offset);
  64
  65   /* Execute DW_AT_location expression for the DWARF expression subroutine in
  66      the DIE at DIE_OFFSET in the CU from CTX.  Do not touch STACK while it
  67      being passed to and returned from the called DWARF subroutine.  */
  68   void (*dwarf_call) (struct dwarf_expr_context *ctx, cu_offset die_offset);
  69
  70   /* Return the base type given by the indicated DIE.  This can throw
  71      an exception if the DIE is invalid or does not represent a base
  72      type.  If can also be NULL in the special case where the
  73      callbacks are not performing evaluation, and thus it is
  74      meaningful to substitute a stub type of the correct size.  */
  75   struct type *(*get_base_type) (struct dwarf_expr_context *ctx, cu_offset die);
  76
  77   /* Push on DWARF stack an entry evaluated for DW_TAG_GNU_call_site's
  78      DWARF_REG/FB_OFFSET at the caller of specified BATON.  If DWARF register
  79      number DWARF_REG specifying the push_dwarf_reg_entry_value parameter is
  80      not -1 FB_OFFSET is ignored.  Otherwise FB_OFFSET specifies stack
  81      parameter offset against caller's stack pointer (which equals the callee's
  82      frame base).  If DEREF_SIZE is not -1 then use
  83      DW_AT_GNU_call_site_data_value instead of DW_AT_GNU_call_site_value.  */
  84   void (*push_dwarf_reg_entry_value) (struct dwarf_expr_context *ctx,
  85                                       int dwarf_reg, CORE_ADDR fb_offset,
  86                                       int deref_size);
  87
  88   /* Return the address indexed by DW_OP_GNU_addr_index.
  89      This can throw an exception if the index is out of range.  */
  90   CORE_ADDR (*get_addr_index) (void *baton, unsigned int index);
  91
  92 #if 0
  93   /* Not yet implemented.  */
  94
  95   /* Return the `object address' for DW_OP_push_object_address.  */
  96   CORE_ADDR (*get_object_address) (void *baton);
  97 #endif
  98 };
  99
 100 /* The location of a value.  */
 101 enum dwarf_value_location
 102 {
 103   /* The piece is in memory.
 104      The value on the dwarf stack is its address.  */
 105   DWARF_VALUE_MEMORY,
 106
 107   /* The piece is in a register.
 108      The value on the dwarf stack is the register number.  */
 109   DWARF_VALUE_REGISTER,
 110
 111   /* The piece is on the dwarf stack.  */
 112   DWARF_VALUE_STACK,
 113
 114   /* The piece is a literal.  */
 115   DWARF_VALUE_LITERAL,
 116
 117   /* The piece was optimized out.  */
 118   DWARF_VALUE_OPTIMIZED_OUT,
 119
 120   /* The piece is an implicit pointer.  */
 121   DWARF_VALUE_IMPLICIT_POINTER
 122 };
 123
 124 /* The dwarf expression stack.  */
 125
 126 struct dwarf_stack_value
 127 {
 128   struct value *value;
 129
 130   /* Non-zero if the piece is in memory and is known to be
 131      on the program's stack.  It is always ok to set this to zero.
 132      This is used, for example, to optimize memory access from the target.
 133      It can vastly speed up backtraces on long latency connections when
 134      "set stack-cache on".  */
 135   int in_stack_memory;
 136 };
 137
 138 /* The expression evaluator works with a dwarf_expr_context, describing
 139    its current state and its callbacks.  */
 140 struct dwarf_expr_context
 141 {
 142   /* The stack of values, allocated with xmalloc.  */
 143   struct dwarf_stack_value *stack;
 144
 145   /* The number of values currently pushed on the stack, and the
 146      number of elements allocated to the stack.  */
 147   int stack_len, stack_allocated;
 148
 149   /* Target architecture to use for address operations.  */
 150   struct gdbarch *gdbarch;
 151
 152   /* Target address size in bytes.  */
 153   int addr_size;
 154
 155   /* DW_FORM_ref_addr size in bytes.  If -1 DWARF is executed from a frame
 156      context and operations depending on DW_FORM_ref_addr are not allowed.  */
 157   int ref_addr_size;
 158
 159   /* Offset used to relocate DW_OP_addr argument.  */
 160   CORE_ADDR offset;
 161
 162   /* An opaque argument provided by the caller, which will be passed
 163      to all of the callback functions.  */
 164   void *baton;
 165
 166   /* Callback functions.  */
 167   const struct dwarf_expr_context_funcs *funcs;
 168
 169   /* The current depth of dwarf expression recursion, via DW_OP_call*,
 170      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
 171      depth we'll tolerate before raising an error.  */
 172   int recursion_depth, max_recursion_depth;
 173
 174   /* Location of the value.  */
 175   enum dwarf_value_location location;
 176
 177   /* For DWARF_VALUE_LITERAL, the current literal value's length and
 178      data.  For DWARF_VALUE_IMPLICIT_POINTER, LEN is the offset of the
 179      target DIE of cu_offset kind.  */
 180   ULONGEST len;
 181   const gdb_byte *data;
 182
 183   /* Initialization status of variable: Non-zero if variable has been
 184      initialized; zero otherwise.  */
 185   int initialized;
 186
 187   /* An array of pieces.  PIECES points to its first element;
 188      NUM_PIECES is its length.
 189
 190      Each time DW_OP_piece is executed, we add a new element to the
 191      end of this array, recording the current top of the stack, the
 192      current location, and the size given as the operand to
 193      DW_OP_piece.  We then pop the top value from the stack, reset the
 194      location, and resume evaluation.
 195
 196      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
 197      from the stack.  We do, ensuring that clients of this interface
 198      expecting to see a value left on the top of the stack (say, code
 199      evaluating frame base expressions or CFA's specified with
 200      DW_CFA_def_cfa_expression) will get an error if the expression
 201      actually marks all the values it computes as pieces.
 202
 203      If an expression never uses DW_OP_piece, num_pieces will be zero.
 204      (It would be nice to present these cases as expressions yielding
 205      a single piece, so that callers need not distinguish between the
 206      no-DW_OP_piece and one-DW_OP_piece cases.  But expressions with
 207      no DW_OP_piece operations have no value to place in a piece's
 208      'size' field; the size comes from the surrounding data.  So the
 209      two cases need to be handled separately.)  */
 210   int num_pieces;
 211   struct dwarf_expr_piece *pieces;
 212 };
 213
 214
 215 /* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece.  */
 216 struct dwarf_expr_piece
 217 {
 218   enum dwarf_value_location location;
 219
 220   union
 221   {
 222     struct
 223     {
 224       /* This piece's address, for DWARF_VALUE_MEMORY pieces.  */
 225       CORE_ADDR addr;
 226       /* Non-zero if the piece is known to be in memory and on
 227          the program's stack.  */
 228       int in_stack_memory;
 229     } mem;
 230
 231     /* The piece's register number, for DWARF_VALUE_REGISTER pieces.  */
 232     int regno;
 233
 234     /* The piece's literal value, for DWARF_VALUE_STACK pieces.  */
 235     struct value *value;
 236
 237     struct
 238     {
 239       /* A pointer to the data making up this piece,
 240          for DWARF_VALUE_LITERAL pieces.  */
 241       const gdb_byte *data;
 242       /* The length of the available data.  */
 243       ULONGEST length;
 244     } literal;
 245
 246     /* Used for DWARF_VALUE_IMPLICIT_POINTER.  */
 247     struct
 248     {
 249       /* The referent DIE from DW_OP_GNU_implicit_pointer.  */
 250       cu_offset die;
 251       /* The byte offset into the resulting data.  */
 252       LONGEST offset;
 253     } ptr;
 254   } v;
 255
 256   /* The length of the piece, in bits.  */
 257   ULONGEST size;
 258   /* The piece offset, in bits.  */
 259   ULONGEST offset;
 260 };
 261
 262 struct dwarf_expr_context *new_dwarf_expr_context (void);
 263 void free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 264 struct cleanup *
 265     make_cleanup_free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 266
 267 void dwarf_expr_push_address (struct dwarf_expr_context *ctx,
 268                               CORE_ADDR value,
 269                               int in_stack_memory);
 270 void dwarf_expr_eval (struct dwarf_expr_context *ctx, const gdb_byte *addr,
 271                       size_t len);
 272 struct value *dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n);
 273 CORE_ADDR dwarf_expr_fetch_address (struct dwarf_expr_context *ctx, int n);
 274 int dwarf_expr_fetch_in_stack_memory (struct dwarf_expr_context *ctx, int n);
 275
 276
 277 const gdb_byte *read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 278                               ULONGEST * r);
 279 const gdb_byte *read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 280                               LONGEST * r);
 281
 282 const char *dwarf_stack_op_name (unsigned int);
 283
 284 void dwarf_expr_require_composition (const gdb_byte *, const gdb_byte *,
 285                                      const char *);
 286
 287 /* Stub dwarf_expr_context_funcs implementations.  */
 288
 289 void ctx_no_get_frame_base (void *baton, const gdb_byte **start,
 290                             size_t *length);
 291 CORE_ADDR ctx_no_get_frame_cfa (void *baton);
 292 CORE_ADDR ctx_no_get_frame_pc (void *baton);
 293 CORE_ADDR ctx_no_get_tls_address (void *baton, CORE_ADDR offset);
 294 void ctx_no_dwarf_call (struct dwarf_expr_context *ctx, cu_offset die_offset);
 295 struct type *ctx_no_get_base_type (struct dwarf_expr_context *ctx,
 296                                    cu_offset die);
 297 void ctx_no_push_dwarf_reg_entry_value (struct dwarf_expr_context *ctx,
 298                                         int dwarf_reg, CORE_ADDR fb_offset,
 299                                         int deref_size);
 300 CORE_ADDR ctx_no_get_addr_index (void *baton, unsigned int index);
 301
 302 int dwarf_block_to_dwarf_reg (const gdb_byte *buf, const gdb_byte *buf_end);
 303
 304 int dwarf_block_to_dwarf_reg_deref (const gdb_byte *buf,
 305                                     const gdb_byte *buf_end,
 306                                     CORE_ADDR *deref_size_return);
 307
 308 int dwarf_block_to_fb_offset (const gdb_byte *buf, const gdb_byte *buf_end,
 309                               CORE_ADDR *fb_offset_return);
 310
 311 int dwarf_block_to_sp_offset (struct gdbarch *gdbarch, const gdb_byte *buf,
 312                               const gdb_byte *buf_end,
 313                               CORE_ADDR *sp_offset_return);
 314
 315 #endif /* dwarf2expr.h */