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