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
  28 struct dwarf_expr_context;
  29
  30 /* Offset relative to the start of its containing CU (compilation unit).  */
  31 typedef struct
  32 {
  33   unsigned int cu_off;
  34 } cu_offset;
  35
  36 /* Offset relative to the start of its .debug_info or .debug_types section.  */
  37 typedef struct
  38 {
  39   unsigned int sect_off;
  40 } sect_offset;
  41
  42 /* Virtual method table for struct dwarf_expr_context below.  */
  43
  44 struct dwarf_expr_context_funcs
  45 {
  46   /* Return the value of register number REGNUM.  */
  47   CORE_ADDR (*read_reg) (void *baton, int regnum);
  48
  49   /* Read LENGTH bytes at ADDR into BUF.  */
  50   void (*read_mem) (void *baton, gdb_byte *buf, CORE_ADDR addr, size_t length);
  51
  52   /* Return the location expression for the frame base attribute, in
  53      START and LENGTH.  The result must be live until the current
  54      expression evaluation is complete.  */
  55   void (*get_frame_base) (void *baton, const gdb_byte **start, size_t *length);
  56
  57   /* Return the CFA for the frame.  */
  58   CORE_ADDR (*get_frame_cfa) (void *baton);
  59
  60   /* Return the PC for the frame.  */
  61   CORE_ADDR (*get_frame_pc) (void *baton);
  62
  63   /* Return the thread-local storage address for
  64      DW_OP_GNU_push_tls_address.  */
  65   CORE_ADDR (*get_tls_address) (void *baton, CORE_ADDR offset);
  66
  67   /* Execute DW_AT_location expression for the DWARF expression subroutine in
  68      the DIE at DIE_OFFSET in the CU from CTX.  Do not touch STACK while it
  69      being passed to and returned from the called DWARF subroutine.  */
  70   void (*dwarf_call) (struct dwarf_expr_context *ctx, cu_offset die_offset);
  71
  72   /* Return the base type given by the indicated DIE.  This can throw
  73      an exception if the DIE is invalid or does not represent a base
  74      type.  If can also be NULL in the special case where the
  75      callbacks are not performing evaluation, and thus it is
  76      meaningful to substitute a stub type of the correct size.  */
  77   struct type *(*get_base_type) (struct dwarf_expr_context *ctx, cu_offset die);
  78
  79   /* Push on DWARF stack an entry evaluated for DW_TAG_GNU_call_site's
  80      DWARF_REG/FB_OFFSET at the caller of specified BATON.  If DWARF register
  81      number DWARF_REG specifying the push_dwarf_reg_entry_value parameter is
  82      not -1 FB_OFFSET is ignored.  Otherwise FB_OFFSET specifies stack
  83      parameter offset against caller's stack pointer (which equals the callee's
  84      frame base).  If DEREF_SIZE is not -1 then use
  85      DW_AT_GNU_call_site_data_value instead of DW_AT_GNU_call_site_value.  */
  86   void (*push_dwarf_reg_entry_value) (struct dwarf_expr_context *ctx,
  87                                       int dwarf_reg, CORE_ADDR fb_offset,
  88                                       int deref_size);
  89
  90   /* Return the address indexed by DW_OP_GNU_addr_index.
  91      This can throw an exception if the index is out of range.  */
  92   CORE_ADDR (*get_addr_index) (void *baton, unsigned int index);
  93
  94 #if 0
  95   /* Not yet implemented.  */
  96
  97   /* Return the `object address' for DW_OP_push_object_address.  */
  98   CORE_ADDR (*get_object_address) (void *baton);
  99 #endif
 100 };
 101
 102 /* The location of a value.  */
 103 enum dwarf_value_location
 104 {
 105   /* The piece is in memory.
 106      The value on the dwarf stack is its address.  */
 107   DWARF_VALUE_MEMORY,
 108
 109   /* The piece is in a register.
 110      The value on the dwarf stack is the register number.  */
 111   DWARF_VALUE_REGISTER,
 112
 113   /* The piece is on the dwarf stack.  */
 114   DWARF_VALUE_STACK,
 115
 116   /* The piece is a literal.  */
 117   DWARF_VALUE_LITERAL,
 118
 119   /* The piece was optimized out.  */
 120   DWARF_VALUE_OPTIMIZED_OUT,
 121
 122   /* The piece is an implicit pointer.  */
 123   DWARF_VALUE_IMPLICIT_POINTER
 124 };
 125
 126 /* The dwarf expression stack.  */
 127
 128 struct dwarf_stack_value
 129 {
 130   struct value *value;
 131
 132   /* Non-zero if the piece is in memory and is known to be
 133      on the program's stack.  It is always ok to set this to zero.
 134      This is used, for example, to optimize memory access from the target.
 135      It can vastly speed up backtraces on long latency connections when
 136      "set stack-cache on".  */
 137   int in_stack_memory;
 138 };
 139
 140 /* The expression evaluator works with a dwarf_expr_context, describing
 141    its current state and its callbacks.  */
 142 struct dwarf_expr_context
 143 {
 144   /* The stack of values, allocated with xmalloc.  */
 145   struct dwarf_stack_value *stack;
 146
 147   /* The number of values currently pushed on the stack, and the
 148      number of elements allocated to the stack.  */
 149   int stack_len, stack_allocated;
 150
 151   /* Target architecture to use for address operations.  */
 152   struct gdbarch *gdbarch;
 153
 154   /* Target address size in bytes.  */
 155   int addr_size;
 156
 157   /* DW_FORM_ref_addr size in bytes.  If -1 DWARF is executed from a frame
 158      context and operations depending on DW_FORM_ref_addr are not allowed.  */
 159   int ref_addr_size;
 160
 161   /* Offset used to relocate DW_OP_addr argument.  */
 162   CORE_ADDR offset;
 163
 164   /* An opaque argument provided by the caller, which will be passed
 165      to all of the callback functions.  */
 166   void *baton;
 167
 168   /* Callback functions.  */
 169   const struct dwarf_expr_context_funcs *funcs;
 170
 171   /* The current depth of dwarf expression recursion, via DW_OP_call*,
 172      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
 173      depth we'll tolerate before raising an error.  */
 174   int recursion_depth, max_recursion_depth;
 175
 176   /* Location of the value.  */
 177   enum dwarf_value_location location;
 178
 179   /* For DWARF_VALUE_LITERAL, the current literal value's length and
 180      data.  For DWARF_VALUE_IMPLICIT_POINTER, LEN is the offset of the
 181      target DIE of cu_offset kind.  */
 182   ULONGEST len;
 183   const gdb_byte *data;
 184
 185   /* Initialization status of variable: Non-zero if variable has been
 186      initialized; zero otherwise.  */
 187   int initialized;
 188
 189   /* An array of pieces.  PIECES points to its first element;
 190      NUM_PIECES is its length.
 191
 192      Each time DW_OP_piece is executed, we add a new element to the
 193      end of this array, recording the current top of the stack, the
 194      current location, and the size given as the operand to
 195      DW_OP_piece.  We then pop the top value from the stack, reset the
 196      location, and resume evaluation.
 197
 198      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
 199      from the stack.  We do, ensuring that clients of this interface
 200      expecting to see a value left on the top of the stack (say, code
 201      evaluating frame base expressions or CFA's specified with
 202      DW_CFA_def_cfa_expression) will get an error if the expression
 203      actually marks all the values it computes as pieces.
 204
 205      If an expression never uses DW_OP_piece, num_pieces will be zero.
 206      (It would be nice to present these cases as expressions yielding
 207      a single piece, so that callers need not distinguish between the
 208      no-DW_OP_piece and one-DW_OP_piece cases.  But expressions with
 209      no DW_OP_piece operations have no value to place in a piece's
 210      'size' field; the size comes from the surrounding data.  So the
 211      two cases need to be handled separately.)  */
 212   int num_pieces;
 213   struct dwarf_expr_piece *pieces;
 214 };
 215
 216
 217 /* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece.  */
 218 struct dwarf_expr_piece
 219 {
 220   enum dwarf_value_location location;
 221
 222   union
 223   {
 224     struct
 225     {
 226       /* This piece's address, for DWARF_VALUE_MEMORY pieces.  */
 227       CORE_ADDR addr;
 228       /* Non-zero if the piece is known to be in memory and on
 229          the program's stack.  */
 230       int in_stack_memory;
 231     } mem;
 232
 233     /* The piece's register number, for DWARF_VALUE_REGISTER pieces.  */
 234     int regno;
 235
 236     /* The piece's literal value, for DWARF_VALUE_STACK pieces.  */
 237     struct value *value;
 238
 239     struct
 240     {
 241       /* A pointer to the data making up this piece,
 242          for DWARF_VALUE_LITERAL pieces.  */
 243       const gdb_byte *data;
 244       /* The length of the available data.  */
 245       ULONGEST length;
 246     } literal;
 247
 248     /* Used for DWARF_VALUE_IMPLICIT_POINTER.  */
 249     struct
 250     {
 251       /* The referent DIE from DW_OP_GNU_implicit_pointer.  */
 252       cu_offset die;
 253       /* The byte offset into the resulting data.  */
 254       LONGEST offset;
 255     } ptr;
 256   } v;
 257
 258   /* The length of the piece, in bits.  */
 259   ULONGEST size;
 260   /* The piece offset, in bits.  */
 261   ULONGEST offset;
 262 };
 263
 264 struct dwarf_expr_context *new_dwarf_expr_context (void);
 265 void free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 266 struct cleanup *
 267     make_cleanup_free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 268
 269 void dwarf_expr_push_address (struct dwarf_expr_context *ctx,
 270                               CORE_ADDR value,
 271                               int in_stack_memory);
 272 void dwarf_expr_eval (struct dwarf_expr_context *ctx, const gdb_byte *addr,
 273                       size_t len);
 274 struct value *dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n);
 275 CORE_ADDR dwarf_expr_fetch_address (struct dwarf_expr_context *ctx, int n);
 276 int dwarf_expr_fetch_in_stack_memory (struct dwarf_expr_context *ctx, int n);
 277
 278 void dwarf_expr_require_composition (const gdb_byte *, const gdb_byte *,
 279                                      const char *);
 280
 281 /* Stub dwarf_expr_context_funcs implementations.  */
 282
 283 void ctx_no_get_frame_base (void *baton, const gdb_byte **start,
 284                             size_t *length);
 285 CORE_ADDR ctx_no_get_frame_cfa (void *baton);
 286 CORE_ADDR ctx_no_get_frame_pc (void *baton);
 287 CORE_ADDR ctx_no_get_tls_address (void *baton, CORE_ADDR offset);
 288 void ctx_no_dwarf_call (struct dwarf_expr_context *ctx, cu_offset die_offset);
 289 struct type *ctx_no_get_base_type (struct dwarf_expr_context *ctx,
 290                                    cu_offset die);
 291 void ctx_no_push_dwarf_reg_entry_value (struct dwarf_expr_context *ctx,
 292                                         int dwarf_reg, CORE_ADDR fb_offset,
 293                                         int deref_size);
 294 CORE_ADDR ctx_no_get_addr_index (void *baton, unsigned int index);
 295
 296 int dwarf_block_to_dwarf_reg (const gdb_byte *buf, const gdb_byte *buf_end);
 297
 298 int dwarf_block_to_dwarf_reg_deref (const gdb_byte *buf,
 299                                     const gdb_byte *buf_end,
 300                                     CORE_ADDR *deref_size_return);
 301
 302 int dwarf_block_to_fb_offset (const gdb_byte *buf, const gdb_byte *buf_end,
 303                               CORE_ADDR *fb_offset_return);
 304
 305 int dwarf_block_to_sp_offset (struct gdbarch *gdbarch, const gdb_byte *buf,
 306                               const gdb_byte *buf_end,
 307                               CORE_ADDR *sp_offset_return);
 308
 309 /* Wrappers around the leb128 reader routines to simplify them for our
 310    purposes.  */
 311
 312 static inline const gdb_byte *
 313 gdb_read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 314                   unsigned long long *r)
 315 {
 316   size_t bytes_read = read_uleb128_to_ull (buf, buf_end, r);
 317
 318   if (bytes_read == 0)
 319     return NULL;
 320   return buf + bytes_read;
 321 }
 322
 323 static inline const gdb_byte *
 324 gdb_read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 325                   long long *r)
 326 {
 327   size_t bytes_read = read_sleb128_to_ll (buf, buf_end, r);
 328
 329   if (bytes_read == 0)
 330     return NULL;
 331   return buf + bytes_read;
 332 }
 333
 334 static inline const gdb_byte *
 335 gdb_skip_leb128 (const gdb_byte *buf, const gdb_byte *buf_end)
 336 {
 337   size_t bytes_read = skip_leb128 (buf, buf_end);
 338
 339   if (bytes_read == 0)
 340     return NULL;
 341   return buf + bytes_read;
 342 }
 343
 344 extern const gdb_byte *safe_read_uleb128 (const gdb_byte *buf,
 345                                           const gdb_byte *buf_end,
 346                                           unsigned long long *r);
 347
 348 extern const gdb_byte *safe_read_sleb128 (const gdb_byte *buf,
 349                                           const gdb_byte *buf_end,
 350                                           long long *r);
 351
 352 extern const gdb_byte *safe_skip_leb128 (const gdb_byte *buf,
 353                                          const gdb_byte *buf_end);
 354
 355 #endif /* dwarf2expr.h */