gdb/dwarf2expr.h

   1 /* DWARF 2 Expression Evaluator.
   2
   3    Copyright (C) 2001-2013 Free Software Foundation, Inc.
   4
   5    Contributed by Daniel Berlin <dan@dberlin.org>.
   6
   7    This file is part of GDB.
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 3 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  21
  22 #if !defined (DWARF2EXPR_H)
  23 #define DWARF2EXPR_H
  24
  25 #include "leb128.h"
  26 #include "gdbtypes.h"
  27
  28 struct dwarf_expr_context;
  29
  30 /* Virtual method table for struct dwarf_expr_context below.  */
  31
  32 struct dwarf_expr_context_funcs
  33 {
  34   /* Return the value of register number REGNUM (a DWARF register number),
  35      read as an address.  */
  36   CORE_ADDR (*read_reg) (void *baton, int regnum);
  37
  38   /* Return a value of type TYPE, stored in register number REGNUM
  39      of the frame associated to the given BATON.
  40
  41      REGNUM is a DWARF register number.  */
  42   struct value *(*get_reg_value) (void *baton, struct type *type, int regnum);
  43
  44   /* Read LENGTH bytes at ADDR into BUF.  */
  45   void (*read_mem) (void *baton, gdb_byte *buf, CORE_ADDR addr, size_t length);
  46
  47   /* Return the location expression for the frame base attribute, in
  48      START and LENGTH.  The result must be live until the current
  49      expression evaluation is complete.  */
  50   void (*get_frame_base) (void *baton, const gdb_byte **start, size_t *length);
  51
  52   /* Return the CFA for the frame.  */
  53   CORE_ADDR (*get_frame_cfa) (void *baton);
  54
  55   /* Return the PC for the frame.  */
  56   CORE_ADDR (*get_frame_pc) (void *baton);
  57
  58   /* Return the thread-local storage address for
  59      DW_OP_GNU_push_tls_address.  */
  60   CORE_ADDR (*get_tls_address) (void *baton, CORE_ADDR offset);
  61
  62   /* Execute DW_AT_location expression for the DWARF expression subroutine in
  63      the DIE at DIE_OFFSET in the CU from CTX.  Do not touch STACK while it
  64      being passed to and returned from the called DWARF subroutine.  */
  65   void (*dwarf_call) (struct dwarf_expr_context *ctx, cu_offset die_offset);
  66
  67   /* Return the base type given by the indicated DIE.  This can throw
  68      an exception if the DIE is invalid or does not represent a base
  69      type.  If can also be NULL in the special case where the
  70      callbacks are not performing evaluation, and thus it is
  71      meaningful to substitute a stub type of the correct size.  */
  72   struct type *(*get_base_type) (struct dwarf_expr_context *ctx, cu_offset die);
  73
  74   /* Push on DWARF stack an entry evaluated for DW_TAG_GNU_call_site's
  75      parameter matching KIND and KIND_U at the caller of specified BATON.
  76      If DEREF_SIZE is not -1 then use DW_AT_GNU_call_site_data_value instead of
  77      DW_AT_GNU_call_site_value.  */
  78   void (*push_dwarf_reg_entry_value) (struct dwarf_expr_context *ctx,
  79                                       enum call_site_parameter_kind kind,
  80                                       union call_site_parameter_u kind_u,
  81                                       int deref_size);
  82
  83   /* Return the address indexed by DW_OP_GNU_addr_index.
  84      This can throw an exception if the index is out of range.  */
  85   CORE_ADDR (*get_addr_index) (void *baton, unsigned int index);
  86
  87 #if 0
  88   /* Not yet implemented.  */
  89
  90   /* Return the `object address' for DW_OP_push_object_address.  */
  91   CORE_ADDR (*get_object_address) (void *baton);
  92 #endif
  93 };
  94
  95 /* The location of a value.  */
  96 enum dwarf_value_location
  97 {
  98   /* The piece is in memory.
  99      The value on the dwarf stack is its address.  */
 100   DWARF_VALUE_MEMORY,
 101
 102   /* The piece is in a register.
 103      The value on the dwarf stack is the register number.  */
 104   DWARF_VALUE_REGISTER,
 105
 106   /* The piece is on the dwarf stack.  */
 107   DWARF_VALUE_STACK,
 108
 109   /* The piece is a literal.  */
 110   DWARF_VALUE_LITERAL,
 111
 112   /* The piece was optimized out.  */
 113   DWARF_VALUE_OPTIMIZED_OUT,
 114
 115   /* The piece is an implicit pointer.  */
 116   DWARF_VALUE_IMPLICIT_POINTER
 117 };
 118
 119 /* The dwarf expression stack.  */
 120
 121 struct dwarf_stack_value
 122 {
 123   struct value *value;
 124
 125   /* Non-zero if the piece is in memory and is known to be
 126      on the program's stack.  It is always ok to set this to zero.
 127      This is used, for example, to optimize memory access from the target.
 128      It can vastly speed up backtraces on long latency connections when
 129      "set stack-cache on".  */
 130   int in_stack_memory;
 131 };
 132
 133 /* The expression evaluator works with a dwarf_expr_context, describing
 134    its current state and its callbacks.  */
 135 struct dwarf_expr_context
 136 {
 137   /* The stack of values, allocated with xmalloc.  */
 138   struct dwarf_stack_value *stack;
 139
 140   /* The number of values currently pushed on the stack, and the
 141      number of elements allocated to the stack.  */
 142   int stack_len, stack_allocated;
 143
 144   /* Target architecture to use for address operations.  */
 145   struct gdbarch *gdbarch;
 146
 147   /* Target address size in bytes.  */
 148   int addr_size;
 149
 150   /* DW_FORM_ref_addr size in bytes.  If -1 DWARF is executed from a frame
 151      context and operations depending on DW_FORM_ref_addr are not allowed.  */
 152   int ref_addr_size;
 153
 154   /* Offset used to relocate DW_OP_addr and DW_OP_GNU_addr_index arguments.  */
 155   CORE_ADDR offset;
 156
 157   /* An opaque argument provided by the caller, which will be passed
 158      to all of the callback functions.  */
 159   void *baton;
 160
 161   /* Callback functions.  */
 162   const struct dwarf_expr_context_funcs *funcs;
 163
 164   /* The current depth of dwarf expression recursion, via DW_OP_call*,
 165      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
 166      depth we'll tolerate before raising an error.  */
 167   int recursion_depth, max_recursion_depth;
 168
 169   /* Location of the value.  */
 170   enum dwarf_value_location location;
 171
 172   /* For DWARF_VALUE_LITERAL, the current literal value's length and
 173      data.  For DWARF_VALUE_IMPLICIT_POINTER, LEN is the offset of the
 174      target DIE of sect_offset kind.  */
 175   ULONGEST len;
 176   const gdb_byte *data;
 177
 178   /* Initialization status of variable: Non-zero if variable has been
 179      initialized; zero otherwise.  */
 180   int initialized;
 181
 182   /* An array of pieces.  PIECES points to its first element;
 183      NUM_PIECES is its length.
 184
 185      Each time DW_OP_piece is executed, we add a new element to the
 186      end of this array, recording the current top of the stack, the
 187      current location, and the size given as the operand to
 188      DW_OP_piece.  We then pop the top value from the stack, reset the
 189      location, and resume evaluation.
 190
 191      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
 192      from the stack.  We do, ensuring that clients of this interface
 193      expecting to see a value left on the top of the stack (say, code
 194      evaluating frame base expressions or CFA's specified with
 195      DW_CFA_def_cfa_expression) will get an error if the expression
 196      actually marks all the values it computes as pieces.
 197
 198      If an expression never uses DW_OP_piece, num_pieces will be zero.
 199      (It would be nice to present these cases as expressions yielding
 200      a single piece, so that callers need not distinguish between the
 201      no-DW_OP_piece and one-DW_OP_piece cases.  But expressions with
 202      no DW_OP_piece operations have no value to place in a piece's
 203      'size' field; the size comes from the surrounding data.  So the
 204      two cases need to be handled separately.)  */
 205   int num_pieces;
 206   struct dwarf_expr_piece *pieces;
 207 };
 208
 209
 210 /* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece.  */
 211 struct dwarf_expr_piece
 212 {
 213   enum dwarf_value_location location;
 214
 215   union
 216   {
 217     struct
 218     {
 219       /* This piece's address, for DWARF_VALUE_MEMORY pieces.  */
 220       CORE_ADDR addr;
 221       /* Non-zero if the piece is known to be in memory and on
 222          the program's stack.  */
 223       int in_stack_memory;
 224     } mem;
 225
 226     /* The piece's register number, for DWARF_VALUE_REGISTER pieces.  */
 227     int regno;
 228
 229     /* The piece's literal value, for DWARF_VALUE_STACK pieces.  */
 230     struct value *value;
 231
 232     struct
 233     {
 234       /* A pointer to the data making up this piece,
 235          for DWARF_VALUE_LITERAL pieces.  */
 236       const gdb_byte *data;
 237       /* The length of the available data.  */
 238       ULONGEST length;
 239     } literal;
 240
 241     /* Used for DWARF_VALUE_IMPLICIT_POINTER.  */
 242     struct
 243     {
 244       /* The referent DIE from DW_OP_GNU_implicit_pointer.  */
 245       sect_offset die;
 246       /* The byte offset into the resulting data.  */
 247       LONGEST offset;
 248     } ptr;
 249   } v;
 250
 251   /* The length of the piece, in bits.  */
 252   ULONGEST size;
 253   /* The piece offset, in bits.  */
 254   ULONGEST offset;
 255 };
 256
 257 struct dwarf_expr_context *new_dwarf_expr_context (void);
 258 void free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 259 struct cleanup *
 260     make_cleanup_free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 261
 262 void dwarf_expr_push_address (struct dwarf_expr_context *ctx,
 263                               CORE_ADDR value,
 264                               int in_stack_memory);
 265 void dwarf_expr_eval (struct dwarf_expr_context *ctx, const gdb_byte *addr,
 266                       size_t len);
 267 struct value *dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n);
 268 CORE_ADDR dwarf_expr_fetch_address (struct dwarf_expr_context *ctx, int n);
 269 int dwarf_expr_fetch_in_stack_memory (struct dwarf_expr_context *ctx, int n);
 270
 271 void dwarf_expr_require_composition (const gdb_byte *, const gdb_byte *,
 272                                      const char *);
 273
 274 /* Stub dwarf_expr_context_funcs implementations.  */
 275
 276 void ctx_no_get_frame_base (void *baton, const gdb_byte **start,
 277                             size_t *length);
 278 CORE_ADDR ctx_no_get_frame_cfa (void *baton);
 279 CORE_ADDR ctx_no_get_frame_pc (void *baton);
 280 CORE_ADDR ctx_no_get_tls_address (void *baton, CORE_ADDR offset);
 281 void ctx_no_dwarf_call (struct dwarf_expr_context *ctx, cu_offset die_offset);
 282 struct type *ctx_no_get_base_type (struct dwarf_expr_context *ctx,
 283                                    cu_offset die);
 284 void ctx_no_push_dwarf_reg_entry_value (struct dwarf_expr_context *ctx,
 285                                         enum call_site_parameter_kind kind,
 286                                         union call_site_parameter_u kind_u,
 287                                         int deref_size);
 288 CORE_ADDR ctx_no_get_addr_index (void *baton, unsigned int index);
 289
 290 int dwarf_block_to_dwarf_reg (const gdb_byte *buf, const gdb_byte *buf_end);
 291
 292 int dwarf_block_to_dwarf_reg_deref (const gdb_byte *buf,
 293                                     const gdb_byte *buf_end,
 294                                     CORE_ADDR *deref_size_return);
 295
 296 int dwarf_block_to_fb_offset (const gdb_byte *buf, const gdb_byte *buf_end,
 297                               CORE_ADDR *fb_offset_return);
 298
 299 int dwarf_block_to_sp_offset (struct gdbarch *gdbarch, const gdb_byte *buf,
 300                               const gdb_byte *buf_end,
 301                               CORE_ADDR *sp_offset_return);
 302
 303 /* Wrappers around the leb128 reader routines to simplify them for our
 304    purposes.  */
 305
 306 static inline const gdb_byte *
 307 gdb_read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 308                   uint64_t *r)
 309 {
 310   size_t bytes_read = read_uleb128_to_uint64 (buf, buf_end, r);
 311
 312   if (bytes_read == 0)
 313     return NULL;
 314   return buf + bytes_read;
 315 }
 316
 317 static inline const gdb_byte *
 318 gdb_read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 319                   int64_t *r)
 320 {
 321   size_t bytes_read = read_sleb128_to_int64 (buf, buf_end, r);
 322
 323   if (bytes_read == 0)
 324     return NULL;
 325   return buf + bytes_read;
 326 }
 327
 328 static inline const gdb_byte *
 329 gdb_skip_leb128 (const gdb_byte *buf, const gdb_byte *buf_end)
 330 {
 331   size_t bytes_read = skip_leb128 (buf, buf_end);
 332
 333   if (bytes_read == 0)
 334     return NULL;
 335   return buf + bytes_read;
 336 }
 337
 338 extern const gdb_byte *safe_read_uleb128 (const gdb_byte *buf,
 339                                           const gdb_byte *buf_end,
 340                                           uint64_t *r);
 341
 342 extern const gdb_byte *safe_read_sleb128 (const gdb_byte *buf,
 343                                           const gdb_byte *buf_end,
 344                                           int64_t *r);
 345
 346 extern const gdb_byte *safe_skip_leb128 (const gdb_byte *buf,
 347                                          const gdb_byte *buf_end);
 348
 349 #endif /* dwarf2expr.h */