gdb/dwarf2expr.h

   1 /* DWARF 2 Expression Evaluator.
   2
   3    Copyright (C) 2001-2016 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_addr_from_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   /* Return the `object address' for DW_OP_push_object_address.  */
  88   CORE_ADDR (*get_object_address) (void *baton);
  89 };
  90
  91 /* The location of a value.  */
  92 enum dwarf_value_location
  93 {
  94   /* The piece is in memory.
  95      The value on the dwarf stack is its address.  */
  96   DWARF_VALUE_MEMORY,
  97
  98   /* The piece is in a register.
  99      The value on the dwarf stack is the register number.  */
 100   DWARF_VALUE_REGISTER,
 101
 102   /* The piece is on the dwarf stack.  */
 103   DWARF_VALUE_STACK,
 104
 105   /* The piece is a literal.  */
 106   DWARF_VALUE_LITERAL,
 107
 108   /* The piece was optimized out.  */
 109   DWARF_VALUE_OPTIMIZED_OUT,
 110
 111   /* The piece is an implicit pointer.  */
 112   DWARF_VALUE_IMPLICIT_POINTER
 113 };
 114
 115 /* The dwarf expression stack.  */
 116
 117 struct dwarf_stack_value
 118 {
 119   struct value *value;
 120
 121   /* Non-zero if the piece is in memory and is known to be
 122      on the program's stack.  It is always ok to set this to zero.
 123      This is used, for example, to optimize memory access from the target.
 124      It can vastly speed up backtraces on long latency connections when
 125      "set stack-cache on".  */
 126   int in_stack_memory;
 127 };
 128
 129 /* The expression evaluator works with a dwarf_expr_context, describing
 130    its current state and its callbacks.  */
 131 struct dwarf_expr_context
 132 {
 133   /* The stack of values, allocated with xmalloc.  */
 134   struct dwarf_stack_value *stack;
 135
 136   /* The number of values currently pushed on the stack, and the
 137      number of elements allocated to the stack.  */
 138   int stack_len, stack_allocated;
 139
 140   /* Target architecture to use for address operations.  */
 141   struct gdbarch *gdbarch;
 142
 143   /* Target address size in bytes.  */
 144   int addr_size;
 145
 146   /* DW_FORM_ref_addr size in bytes.  If -1 DWARF is executed from a frame
 147      context and operations depending on DW_FORM_ref_addr are not allowed.  */
 148   int ref_addr_size;
 149
 150   /* Offset used to relocate DW_OP_addr and DW_OP_GNU_addr_index arguments.  */
 151   CORE_ADDR offset;
 152
 153   /* An opaque argument provided by the caller, which will be passed
 154      to all of the callback functions.  */
 155   void *baton;
 156
 157   /* Callback functions.  */
 158   const struct dwarf_expr_context_funcs *funcs;
 159
 160   /* The current depth of dwarf expression recursion, via DW_OP_call*,
 161      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
 162      depth we'll tolerate before raising an error.  */
 163   int recursion_depth, max_recursion_depth;
 164
 165   /* Location of the value.  */
 166   enum dwarf_value_location location;
 167
 168   /* For DWARF_VALUE_LITERAL, the current literal value's length and
 169      data.  For DWARF_VALUE_IMPLICIT_POINTER, LEN is the offset of the
 170      target DIE of sect_offset kind.  */
 171   ULONGEST len;
 172   const gdb_byte *data;
 173
 174   /* Initialization status of variable: Non-zero if variable has been
 175      initialized; zero otherwise.  */
 176   int initialized;
 177
 178   /* An array of pieces.  PIECES points to its first element;
 179      NUM_PIECES is its length.
 180
 181      Each time DW_OP_piece is executed, we add a new element to the
 182      end of this array, recording the current top of the stack, the
 183      current location, and the size given as the operand to
 184      DW_OP_piece.  We then pop the top value from the stack, reset the
 185      location, and resume evaluation.
 186
 187      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
 188      from the stack.  We do, ensuring that clients of this interface
 189      expecting to see a value left on the top of the stack (say, code
 190      evaluating frame base expressions or CFA's specified with
 191      DW_CFA_def_cfa_expression) will get an error if the expression
 192      actually marks all the values it computes as pieces.
 193
 194      If an expression never uses DW_OP_piece, num_pieces will be zero.
 195      (It would be nice to present these cases as expressions yielding
 196      a single piece, so that callers need not distinguish between the
 197      no-DW_OP_piece and one-DW_OP_piece cases.  But expressions with
 198      no DW_OP_piece operations have no value to place in a piece's
 199      'size' field; the size comes from the surrounding data.  So the
 200      two cases need to be handled separately.)  */
 201   int num_pieces;
 202   struct dwarf_expr_piece *pieces;
 203 };
 204
 205
 206 /* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece.  */
 207 struct dwarf_expr_piece
 208 {
 209   enum dwarf_value_location location;
 210
 211   union
 212   {
 213     struct
 214     {
 215       /* This piece's address, for DWARF_VALUE_MEMORY pieces.  */
 216       CORE_ADDR addr;
 217       /* Non-zero if the piece is known to be in memory and on
 218          the program's stack.  */
 219       int in_stack_memory;
 220     } mem;
 221
 222     /* The piece's register number, for DWARF_VALUE_REGISTER pieces.  */
 223     int regno;
 224
 225     /* The piece's literal value, for DWARF_VALUE_STACK pieces.  */
 226     struct value *value;
 227
 228     struct
 229     {
 230       /* A pointer to the data making up this piece,
 231          for DWARF_VALUE_LITERAL pieces.  */
 232       const gdb_byte *data;
 233       /* The length of the available data.  */
 234       ULONGEST length;
 235     } literal;
 236
 237     /* Used for DWARF_VALUE_IMPLICIT_POINTER.  */
 238     struct
 239     {
 240       /* The referent DIE from DW_OP_GNU_implicit_pointer.  */
 241       sect_offset die;
 242       /* The byte offset into the resulting data.  */
 243       LONGEST offset;
 244     } ptr;
 245   } v;
 246
 247   /* The length of the piece, in bits.  */
 248   ULONGEST size;
 249   /* The piece offset, in bits.  */
 250   ULONGEST offset;
 251 };
 252
 253 struct dwarf_expr_context *new_dwarf_expr_context (void);
 254 void free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 255 struct cleanup *
 256     make_cleanup_free_dwarf_expr_context (struct dwarf_expr_context *ctx);
 257
 258 void dwarf_expr_push_address (struct dwarf_expr_context *ctx,
 259                               CORE_ADDR value,
 260                               int in_stack_memory);
 261 void dwarf_expr_eval (struct dwarf_expr_context *ctx, const gdb_byte *addr,
 262                       size_t len);
 263 struct value *dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n);
 264 CORE_ADDR dwarf_expr_fetch_address (struct dwarf_expr_context *ctx, int n);
 265 int dwarf_expr_fetch_in_stack_memory (struct dwarf_expr_context *ctx, int n);
 266
 267 void dwarf_expr_require_composition (const gdb_byte *, const gdb_byte *,
 268                                      const char *);
 269
 270 /* Stub dwarf_expr_context_funcs implementations.  */
 271
 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, cu_offset die_offset);
 278 struct type *ctx_no_get_base_type (struct dwarf_expr_context *ctx,
 279                                    cu_offset die);
 280 void ctx_no_push_dwarf_reg_entry_value (struct dwarf_expr_context *ctx,
 281                                         enum call_site_parameter_kind kind,
 282                                         union call_site_parameter_u kind_u,
 283                                         int deref_size);
 284 CORE_ADDR ctx_no_get_addr_index (void *baton, unsigned int index);
 285
 286 int dwarf_block_to_dwarf_reg (const gdb_byte *buf, const gdb_byte *buf_end);
 287
 288 int dwarf_block_to_dwarf_reg_deref (const gdb_byte *buf,
 289                                     const gdb_byte *buf_end,
 290                                     CORE_ADDR *deref_size_return);
 291
 292 int dwarf_block_to_fb_offset (const gdb_byte *buf, const gdb_byte *buf_end,
 293                               CORE_ADDR *fb_offset_return);
 294
 295 int dwarf_block_to_sp_offset (struct gdbarch *gdbarch, const gdb_byte *buf,
 296                               const gdb_byte *buf_end,
 297                               CORE_ADDR *sp_offset_return);
 298
 299 /* Wrappers around the leb128 reader routines to simplify them for our
 300    purposes.  */
 301
 302 static inline const gdb_byte *
 303 gdb_read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 304                   uint64_t *r)
 305 {
 306   size_t bytes_read = read_uleb128_to_uint64 (buf, buf_end, r);
 307
 308   if (bytes_read == 0)
 309     return NULL;
 310   return buf + bytes_read;
 311 }
 312
 313 static inline const gdb_byte *
 314 gdb_read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 315                   int64_t *r)
 316 {
 317   size_t bytes_read = read_sleb128_to_int64 (buf, buf_end, r);
 318
 319   if (bytes_read == 0)
 320     return NULL;
 321   return buf + bytes_read;
 322 }
 323
 324 static inline const gdb_byte *
 325 gdb_skip_leb128 (const gdb_byte *buf, const gdb_byte *buf_end)
 326 {
 327   size_t bytes_read = skip_leb128 (buf, buf_end);
 328
 329   if (bytes_read == 0)
 330     return NULL;
 331   return buf + bytes_read;
 332 }
 333
 334 extern const gdb_byte *safe_read_uleb128 (const gdb_byte *buf,
 335                                           const gdb_byte *buf_end,
 336                                           uint64_t *r);
 337
 338 extern const gdb_byte *safe_read_sleb128 (const gdb_byte *buf,
 339                                           const gdb_byte *buf_end,
 340                                           int64_t *r);
 341
 342 extern const gdb_byte *safe_skip_leb128 (const gdb_byte *buf,
 343                                          const gdb_byte *buf_end);
 344
 345 #endif /* dwarf2expr.h */