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 or DW_OP_form_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   dwarf_expr_context ();
 134   ~dwarf_expr_context ();
 135
 136   void push_address (CORE_ADDR value, int in_stack_memory);
 137   void eval (const gdb_byte *addr, size_t len);
 138   struct value *fetch (int n);
 139   CORE_ADDR fetch_address (int n);
 140   int fetch_in_stack_memory (int n);
 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 and DW_OP_GNU_addr_index arguments.  */
 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 sect_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 private:
 214
 215   struct type *address_type () const;
 216   void grow_stack (size_t need);
 217   void push (struct value *value, int in_stack_memory);
 218   int stack_empty_p () const;
 219   void add_piece (ULONGEST size, ULONGEST offset);
 220   struct type *get_base_type (cu_offset die, int size);
 221   void execute_stack_op (const gdb_byte *op_ptr, const gdb_byte *op_end);
 222   void pop ();
 223 };
 224
 225
 226 /* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece.  */
 227 struct dwarf_expr_piece
 228 {
 229   enum dwarf_value_location location;
 230
 231   union
 232   {
 233     struct
 234     {
 235       /* This piece's address, for DWARF_VALUE_MEMORY pieces.  */
 236       CORE_ADDR addr;
 237       /* Non-zero if the piece is known to be in memory and on
 238          the program's stack.  */
 239       int in_stack_memory;
 240     } mem;
 241
 242     /* The piece's register number, for DWARF_VALUE_REGISTER pieces.  */
 243     int regno;
 244
 245     /* The piece's literal value, for DWARF_VALUE_STACK pieces.  */
 246     struct value *value;
 247
 248     struct
 249     {
 250       /* A pointer to the data making up this piece,
 251          for DWARF_VALUE_LITERAL pieces.  */
 252       const gdb_byte *data;
 253       /* The length of the available data.  */
 254       ULONGEST length;
 255     } literal;
 256
 257     /* Used for DWARF_VALUE_IMPLICIT_POINTER.  */
 258     struct
 259     {
 260       /* The referent DIE from DW_OP_GNU_implicit_pointer.  */
 261       sect_offset die;
 262       /* The byte offset into the resulting data.  */
 263       LONGEST offset;
 264     } ptr;
 265   } v;
 266
 267   /* The length of the piece, in bits.  */
 268   ULONGEST size;
 269   /* The piece offset, in bits.  */
 270   ULONGEST offset;
 271 };
 272
 273 void dwarf_expr_require_composition (const gdb_byte *, const gdb_byte *,
 274                                      const char *);
 275
 276 /* Stub dwarf_expr_context_funcs implementations.  */
 277
 278 void ctx_no_get_frame_base (void *baton, const gdb_byte **start,
 279                             size_t *length);
 280 CORE_ADDR ctx_no_get_frame_cfa (void *baton);
 281 CORE_ADDR ctx_no_get_frame_pc (void *baton);
 282 CORE_ADDR ctx_no_get_tls_address (void *baton, CORE_ADDR offset);
 283 void ctx_no_dwarf_call (struct dwarf_expr_context *ctx, cu_offset die_offset);
 284 struct type *ctx_no_get_base_type (struct dwarf_expr_context *ctx,
 285                                    cu_offset die);
 286 void ctx_no_push_dwarf_reg_entry_value (struct dwarf_expr_context *ctx,
 287                                         enum call_site_parameter_kind kind,
 288                                         union call_site_parameter_u kind_u,
 289                                         int deref_size);
 290 CORE_ADDR ctx_no_get_addr_index (void *baton, unsigned int index);
 291
 292 int dwarf_block_to_dwarf_reg (const gdb_byte *buf, const gdb_byte *buf_end);
 293
 294 int dwarf_block_to_dwarf_reg_deref (const gdb_byte *buf,
 295                                     const gdb_byte *buf_end,
 296                                     CORE_ADDR *deref_size_return);
 297
 298 int dwarf_block_to_fb_offset (const gdb_byte *buf, const gdb_byte *buf_end,
 299                               CORE_ADDR *fb_offset_return);
 300
 301 int dwarf_block_to_sp_offset (struct gdbarch *gdbarch, const gdb_byte *buf,
 302                               const gdb_byte *buf_end,
 303                               CORE_ADDR *sp_offset_return);
 304
 305 /* Wrappers around the leb128 reader routines to simplify them for our
 306    purposes.  */
 307
 308 static inline const gdb_byte *
 309 gdb_read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 310                   uint64_t *r)
 311 {
 312   size_t bytes_read = read_uleb128_to_uint64 (buf, buf_end, r);
 313
 314   if (bytes_read == 0)
 315     return NULL;
 316   return buf + bytes_read;
 317 }
 318
 319 static inline const gdb_byte *
 320 gdb_read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 321                   int64_t *r)
 322 {
 323   size_t bytes_read = read_sleb128_to_int64 (buf, buf_end, r);
 324
 325   if (bytes_read == 0)
 326     return NULL;
 327   return buf + bytes_read;
 328 }
 329
 330 static inline const gdb_byte *
 331 gdb_skip_leb128 (const gdb_byte *buf, const gdb_byte *buf_end)
 332 {
 333   size_t bytes_read = skip_leb128 (buf, buf_end);
 334
 335   if (bytes_read == 0)
 336     return NULL;
 337   return buf + bytes_read;
 338 }
 339
 340 extern const gdb_byte *safe_read_uleb128 (const gdb_byte *buf,
 341                                           const gdb_byte *buf_end,
 342                                           uint64_t *r);
 343
 344 extern const gdb_byte *safe_read_sleb128 (const gdb_byte *buf,
 345                                           const gdb_byte *buf_end,
 346                                           int64_t *r);
 347
 348 extern const gdb_byte *safe_skip_leb128 (const gdb_byte *buf,
 349                                          const gdb_byte *buf_end);
 350
 351 #endif /* dwarf2expr.h */