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 #include "leb128.h"
  27 #include "gdbtypes.h"
  28
  29 struct dwarf_expr_context;
  30
  31 /* Virtual method table for struct dwarf_expr_context below.  */
  32
  33 struct dwarf_expr_context_funcs
  34 {
  35   /* Return the value of register number REGNUM.  */
  36   CORE_ADDR (*read_reg) (void *baton, int regnum);
  37
  38   /* Read LENGTH bytes at ADDR into BUF.  */
  39   void (*read_mem) (void *baton, gdb_byte *buf, CORE_ADDR addr, size_t length);
  40
  41   /* Return the location expression for the frame base attribute, in
  42      START and LENGTH.  The result must be live until the current
  43      expression evaluation is complete.  */
  44   void (*get_frame_base) (void *baton, const gdb_byte **start, size_t *length);
  45
  46   /* Return the CFA for the frame.  */
  47   CORE_ADDR (*get_frame_cfa) (void *baton);
  48
  49   /* Return the PC for the frame.  */
  50   CORE_ADDR (*get_frame_pc) (void *baton);
  51
  52   /* Return the thread-local storage address for
  53      DW_OP_GNU_push_tls_address.  */
  54   CORE_ADDR (*get_tls_address) (void *baton, CORE_ADDR offset);
  55
  56   /* Execute DW_AT_location expression for the DWARF expression subroutine in
  57      the DIE at DIE_OFFSET in the CU from CTX.  Do not touch STACK while it
  58      being passed to and returned from the called DWARF subroutine.  */
  59   void (*dwarf_call) (struct dwarf_expr_context *ctx, cu_offset die_offset);
  60
  61   /* Return the base type given by the indicated DIE.  This can throw
  62      an exception if the DIE is invalid or does not represent a base
  63      type.  If can also be NULL in the special case where the
  64      callbacks are not performing evaluation, and thus it is
  65      meaningful to substitute a stub type of the correct size.  */
  66   struct type *(*get_base_type) (struct dwarf_expr_context *ctx, cu_offset die);
  67
  68   /* Push on DWARF stack an entry evaluated for DW_TAG_GNU_call_site's
  69      parameter matching KIND and KIND_U at the caller of specified BATON.
  70      If DEREF_SIZE is not -1 then use DW_AT_GNU_call_site_data_value instead of
  71      DW_AT_GNU_call_site_value.  */
  72   void (*push_dwarf_reg_entry_value) (struct dwarf_expr_context *ctx,
  73                                       enum call_site_parameter_kind kind,
  74                                       union call_site_parameter_u kind_u,
  75                                       int deref_size);
  76
  77   /* Return the address indexed by DW_OP_GNU_addr_index.
  78      This can throw an exception if the index is out of range.  */
  79   CORE_ADDR (*get_addr_index) (void *baton, unsigned int index);
  80
  81 #if 0
  82   /* Not yet implemented.  */
  83
  84   /* Return the `object address' for DW_OP_push_object_address.  */
  85   CORE_ADDR (*get_object_address) (void *baton);
  86 #endif
  87 };
  88
  89 /* The location of a value.  */
  90 enum dwarf_value_location
  91 {
  92   /* The piece is in memory.
  93      The value on the dwarf stack is its address.  */
  94   DWARF_VALUE_MEMORY,
  95
  96   /* The piece is in a register.
  97      The value on the dwarf stack is the register number.  */
  98   DWARF_VALUE_REGISTER,
  99
 100   /* The piece is on the dwarf stack.  */
 101   DWARF_VALUE_STACK,
 102
 103   /* The piece is a literal.  */
 104   DWARF_VALUE_LITERAL,
 105
 106   /* The piece was optimized out.  */
 107   DWARF_VALUE_OPTIMIZED_OUT,
 108
 109   /* The piece is an implicit pointer.  */
 110   DWARF_VALUE_IMPLICIT_POINTER
 111 };
 112
 113 /* The dwarf expression stack.  */
 114
 115 struct dwarf_stack_value
 116 {
 117   struct value *value;
 118
 119   /* Non-zero if the piece is in memory and is known to be
 120      on the program's stack.  It is always ok to set this to zero.
 121      This is used, for example, to optimize memory access from the target.
 122      It can vastly speed up backtraces on long latency connections when
 123      "set stack-cache on".  */
 124   int in_stack_memory;
 125 };
 126
 127 /* The expression evaluator works with a dwarf_expr_context, describing
 128    its current state and its callbacks.  */
 129 struct dwarf_expr_context
 130 {
 131   /* The stack of values, allocated with xmalloc.  */
 132   struct dwarf_stack_value *stack;
 133
 134   /* The number of values currently pushed on the stack, and the
 135      number of elements allocated to the stack.  */
 136   int stack_len, stack_allocated;
 137
 138   /* Target architecture to use for address operations.  */
 139   struct gdbarch *gdbarch;
 140
 141   /* Target address size in bytes.  */
 142   int addr_size;
 143
 144   /* DW_FORM_ref_addr size in bytes.  If -1 DWARF is executed from a frame
 145      context and operations depending on DW_FORM_ref_addr are not allowed.  */
 146   int ref_addr_size;
 147
 148   /* Offset used to relocate DW_OP_addr and DW_OP_GNU_addr_index arguments.  */
 149   CORE_ADDR offset;
 150
 151   /* An opaque argument provided by the caller, which will be passed
 152      to all of the callback functions.  */
 153   void *baton;
 154
 155   /* Callback functions.  */
 156   const struct dwarf_expr_context_funcs *funcs;
 157
 158   /* The current depth of dwarf expression recursion, via DW_OP_call*,
 159      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
 160      depth we'll tolerate before raising an error.  */
 161   int recursion_depth, max_recursion_depth;
 162
 163   /* Location of the value.  */
 164   enum dwarf_value_location location;
 165
 166   /* For DWARF_VALUE_LITERAL, the current literal value's length and
 167      data.  For DWARF_VALUE_IMPLICIT_POINTER, LEN is the offset of the
 168      target DIE of sect_offset kind.  */
 169   ULONGEST len;
 170   const gdb_byte *data;
 171
 172   /* Initialization status of variable: Non-zero if variable has been
 173      initialized; zero otherwise.  */
 174   int initialized;
 175
 176   /* An array of pieces.  PIECES points to its first element;
 177      NUM_PIECES is its length.
 178
 179      Each time DW_OP_piece is executed, we add a new element to the
 180      end of this array, recording the current top of the stack, the
 181      current location, and the size given as the operand to
 182      DW_OP_piece.  We then pop the top value from the stack, reset the
 183      location, and resume evaluation.
 184
 185      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
 186      from the stack.  We do, ensuring that clients of this interface
 187      expecting to see a value left on the top of the stack (say, code
 188      evaluating frame base expressions or CFA's specified with
 189      DW_CFA_def_cfa_expression) will get an error if the expression
 190      actually marks all the values it computes as pieces.
 191
 192      If an expression never uses DW_OP_piece, num_pieces will be zero.
 193      (It would be nice to present these cases as expressions yielding
 194      a single piece, so that callers need not distinguish between the
 195      no-DW_OP_piece and one-DW_OP_piece cases.  But expressions with
 196      no DW_OP_piece operations have no value to place in a piece's
 197      'size' field; the size comes from the surrounding data.  So the
 198      two cases need to be handled separately.)  */
 199   int num_pieces;
 200   struct dwarf_expr_piece *pieces;
 201 };
 202
 203
 204 /* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece.  */
 205 struct dwarf_expr_piece
 206 {
 207   enum dwarf_value_location location;
 208
 209   union
 210   {
 211     struct
 212     {
 213       /* This piece's address, for DWARF_VALUE_MEMORY pieces.  */
 214       CORE_ADDR addr;
 215       /* Non-zero if the piece is known to be in memory and on
 216          the program's stack.  */
 217       int in_stack_memory;
 218     } mem;
 219
 220     /* The piece's register number, for DWARF_VALUE_REGISTER pieces.  */
 221     int regno;
 222
 223     /* The piece's literal value, for DWARF_VALUE_STACK pieces.  */
 224     struct value *value;
 225
 226     struct
 227     {
 228       /* A pointer to the data making up this piece,
 229          for DWARF_VALUE_LITERAL pieces.  */
 230       const gdb_byte *data;
 231       /* The length of the available data.  */
 232       ULONGEST length;
 233     } literal;
 234
 235     /* Used for DWARF_VALUE_IMPLICIT_POINTER.  */
 236     struct
 237     {
 238       /* The referent DIE from DW_OP_GNU_implicit_pointer.  */
 239       sect_offset die;
 240       /* The byte offset into the resulting data.  */
 241       LONGEST offset;
 242     } ptr;
 243   } v;
 244
 245   /* The length of the piece, in bits.  */
 246   ULONGEST size;
 247   /* The piece offset, in bits.  */
 248   ULONGEST offset;
 249 };
 250
 251 struct dwarf_expr_context *new_dwarf_expr_context (void);
 252 void free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 253 struct cleanup *
 254     make_cleanup_free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 255
 256 void dwarf_expr_push_address (struct dwarf_expr_context *ctx,
 257                               CORE_ADDR value,
 258                               int in_stack_memory);
 259 void dwarf_expr_eval (struct dwarf_expr_context *ctx, const gdb_byte *addr,
 260                       size_t len);
 261 struct value *dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n);
 262 CORE_ADDR dwarf_expr_fetch_address (struct dwarf_expr_context *ctx, int n);
 263 int dwarf_expr_fetch_in_stack_memory (struct dwarf_expr_context *ctx, int n);
 264
 265 void dwarf_expr_require_composition (const gdb_byte *, const gdb_byte *,
 266                                      const char *);
 267
 268 /* Stub dwarf_expr_context_funcs implementations.  */
 269
 270 void ctx_no_get_frame_base (void *baton, const gdb_byte **start,
 271                             size_t *length);
 272 CORE_ADDR ctx_no_get_frame_cfa (void *baton);
 273 CORE_ADDR ctx_no_get_frame_pc (void *baton);
 274 CORE_ADDR ctx_no_get_tls_address (void *baton, CORE_ADDR offset);
 275 void ctx_no_dwarf_call (struct dwarf_expr_context *ctx, cu_offset die_offset);
 276 struct type *ctx_no_get_base_type (struct dwarf_expr_context *ctx,
 277                                    cu_offset die);
 278 void ctx_no_push_dwarf_reg_entry_value (struct dwarf_expr_context *ctx,
 279                                         enum call_site_parameter_kind kind,
 280                                         union call_site_parameter_u kind_u,
 281                                         int deref_size);
 282 CORE_ADDR ctx_no_get_addr_index (void *baton, unsigned int index);
 283
 284 int dwarf_block_to_dwarf_reg (const gdb_byte *buf, const gdb_byte *buf_end);
 285
 286 int dwarf_block_to_dwarf_reg_deref (const gdb_byte *buf,
 287                                     const gdb_byte *buf_end,
 288                                     CORE_ADDR *deref_size_return);
 289
 290 int dwarf_block_to_fb_offset (const gdb_byte *buf, const gdb_byte *buf_end,
 291                               CORE_ADDR *fb_offset_return);
 292
 293 int dwarf_block_to_sp_offset (struct gdbarch *gdbarch, const gdb_byte *buf,
 294                               const gdb_byte *buf_end,
 295                               CORE_ADDR *sp_offset_return);
 296
 297 /* Wrappers around the leb128 reader routines to simplify them for our
 298    purposes.  */
 299
 300 static inline const gdb_byte *
 301 gdb_read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 302                   uint64_t *r)
 303 {
 304   size_t bytes_read = read_uleb128_to_uint64 (buf, buf_end, r);
 305
 306   if (bytes_read == 0)
 307     return NULL;
 308   return buf + bytes_read;
 309 }
 310
 311 static inline const gdb_byte *
 312 gdb_read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 313                   int64_t *r)
 314 {
 315   size_t bytes_read = read_sleb128_to_int64 (buf, buf_end, r);
 316
 317   if (bytes_read == 0)
 318     return NULL;
 319   return buf + bytes_read;
 320 }
 321
 322 static inline const gdb_byte *
 323 gdb_skip_leb128 (const gdb_byte *buf, const gdb_byte *buf_end)
 324 {
 325   size_t bytes_read = skip_leb128 (buf, buf_end);
 326
 327   if (bytes_read == 0)
 328     return NULL;
 329   return buf + bytes_read;
 330 }
 331
 332 extern const gdb_byte *safe_read_uleb128 (const gdb_byte *buf,
 333                                           const gdb_byte *buf_end,
 334                                           uint64_t *r);
 335
 336 extern const gdb_byte *safe_read_sleb128 (const gdb_byte *buf,
 337                                           const gdb_byte *buf_end,
 338                                           int64_t *r);
 339
 340 extern const gdb_byte *safe_skip_leb128 (const gdb_byte *buf,
 341                                          const gdb_byte *buf_end);
 342
 343 #endif /* dwarf2expr.h */