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   /* The stack of values, allocated with xmalloc.  */
 137   struct dwarf_stack_value *stack;
 138
 139   /* The number of values currently pushed on the stack, and the
 140      number of elements allocated to the stack.  */
 141   int stack_len, stack_allocated;
 142
 143   /* Target architecture to use for address operations.  */
 144   struct gdbarch *gdbarch;
 145
 146   /* Target address size in bytes.  */
 147   int addr_size;
 148
 149   /* DW_FORM_ref_addr size in bytes.  If -1 DWARF is executed from a frame
 150      context and operations depending on DW_FORM_ref_addr are not allowed.  */
 151   int ref_addr_size;
 152
 153   /* Offset used to relocate DW_OP_addr and DW_OP_GNU_addr_index arguments.  */
 154   CORE_ADDR offset;
 155
 156   /* An opaque argument provided by the caller, which will be passed
 157      to all of the callback functions.  */
 158   void *baton;
 159
 160   /* Callback functions.  */
 161   const struct dwarf_expr_context_funcs *funcs;
 162
 163   /* The current depth of dwarf expression recursion, via DW_OP_call*,
 164      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
 165      depth we'll tolerate before raising an error.  */
 166   int recursion_depth, max_recursion_depth;
 167
 168   /* Location of the value.  */
 169   enum dwarf_value_location location;
 170
 171   /* For DWARF_VALUE_LITERAL, the current literal value's length and
 172      data.  For DWARF_VALUE_IMPLICIT_POINTER, LEN is the offset of the
 173      target DIE of sect_offset kind.  */
 174   ULONGEST len;
 175   const gdb_byte *data;
 176
 177   /* Initialization status of variable: Non-zero if variable has been
 178      initialized; zero otherwise.  */
 179   int initialized;
 180
 181   /* An array of pieces.  PIECES points to its first element;
 182      NUM_PIECES is its length.
 183
 184      Each time DW_OP_piece is executed, we add a new element to the
 185      end of this array, recording the current top of the stack, the
 186      current location, and the size given as the operand to
 187      DW_OP_piece.  We then pop the top value from the stack, reset the
 188      location, and resume evaluation.
 189
 190      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
 191      from the stack.  We do, ensuring that clients of this interface
 192      expecting to see a value left on the top of the stack (say, code
 193      evaluating frame base expressions or CFA's specified with
 194      DW_CFA_def_cfa_expression) will get an error if the expression
 195      actually marks all the values it computes as pieces.
 196
 197      If an expression never uses DW_OP_piece, num_pieces will be zero.
 198      (It would be nice to present these cases as expressions yielding
 199      a single piece, so that callers need not distinguish between the
 200      no-DW_OP_piece and one-DW_OP_piece cases.  But expressions with
 201      no DW_OP_piece operations have no value to place in a piece's
 202      'size' field; the size comes from the surrounding data.  So the
 203      two cases need to be handled separately.)  */
 204   int num_pieces;
 205   struct dwarf_expr_piece *pieces;
 206 };
 207
 208
 209 /* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece.  */
 210 struct dwarf_expr_piece
 211 {
 212   enum dwarf_value_location location;
 213
 214   union
 215   {
 216     struct
 217     {
 218       /* This piece's address, for DWARF_VALUE_MEMORY pieces.  */
 219       CORE_ADDR addr;
 220       /* Non-zero if the piece is known to be in memory and on
 221          the program's stack.  */
 222       int in_stack_memory;
 223     } mem;
 224
 225     /* The piece's register number, for DWARF_VALUE_REGISTER pieces.  */
 226     int regno;
 227
 228     /* The piece's literal value, for DWARF_VALUE_STACK pieces.  */
 229     struct value *value;
 230
 231     struct
 232     {
 233       /* A pointer to the data making up this piece,
 234          for DWARF_VALUE_LITERAL pieces.  */
 235       const gdb_byte *data;
 236       /* The length of the available data.  */
 237       ULONGEST length;
 238     } literal;
 239
 240     /* Used for DWARF_VALUE_IMPLICIT_POINTER.  */
 241     struct
 242     {
 243       /* The referent DIE from DW_OP_GNU_implicit_pointer.  */
 244       sect_offset die;
 245       /* The byte offset into the resulting data.  */
 246       LONGEST offset;
 247     } ptr;
 248   } v;
 249
 250   /* The length of the piece, in bits.  */
 251   ULONGEST size;
 252   /* The piece offset, in bits.  */
 253   ULONGEST offset;
 254 };
 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 */