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 /* The location of a value.  */
  29 enum dwarf_value_location
  30 {
  31   /* The piece is in memory.
  32      The value on the dwarf stack is its address.  */
  33   DWARF_VALUE_MEMORY,
  34
  35   /* The piece is in a register.
  36      The value on the dwarf stack is the register number.  */
  37   DWARF_VALUE_REGISTER,
  38
  39   /* The piece is on the dwarf stack.  */
  40   DWARF_VALUE_STACK,
  41
  42   /* The piece is a literal.  */
  43   DWARF_VALUE_LITERAL,
  44
  45   /* The piece was optimized out.  */
  46   DWARF_VALUE_OPTIMIZED_OUT,
  47
  48   /* The piece is an implicit pointer.  */
  49   DWARF_VALUE_IMPLICIT_POINTER
  50 };
  51
  52 /* The dwarf expression stack.  */
  53
  54 struct dwarf_stack_value
  55 {
  56   struct value *value;
  57
  58   /* Non-zero if the piece is in memory and is known to be
  59      on the program's stack.  It is always ok to set this to zero.
  60      This is used, for example, to optimize memory access from the target.
  61      It can vastly speed up backtraces on long latency connections when
  62      "set stack-cache on".  */
  63   int in_stack_memory;
  64 };
  65
  66 /* The expression evaluator works with a dwarf_expr_context, describing
  67    its current state and its callbacks.  */
  68 struct dwarf_expr_context
  69 {
  70   dwarf_expr_context ();
  71   ~dwarf_expr_context ();
  72
  73   void push_address (CORE_ADDR value, int in_stack_memory);
  74   void eval (const gdb_byte *addr, size_t len);
  75   struct value *fetch (int n);
  76   CORE_ADDR fetch_address (int n);
  77   int fetch_in_stack_memory (int n);
  78
  79   /* The stack of values, allocated with xmalloc.  */
  80   struct dwarf_stack_value *stack;
  81
  82   /* The number of values currently pushed on the stack, and the
  83      number of elements allocated to the stack.  */
  84   int stack_len, stack_allocated;
  85
  86   /* Target architecture to use for address operations.  */
  87   struct gdbarch *gdbarch;
  88
  89   /* Target address size in bytes.  */
  90   int addr_size;
  91
  92   /* DW_FORM_ref_addr size in bytes.  If -1 DWARF is executed from a frame
  93      context and operations depending on DW_FORM_ref_addr are not allowed.  */
  94   int ref_addr_size;
  95
  96   /* Offset used to relocate DW_OP_addr and DW_OP_GNU_addr_index arguments.  */
  97   CORE_ADDR offset;
  98
  99   /* The current depth of dwarf expression recursion, via DW_OP_call*,
 100      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
 101      depth we'll tolerate before raising an error.  */
 102   int recursion_depth, max_recursion_depth;
 103
 104   /* Location of the value.  */
 105   enum dwarf_value_location location;
 106
 107   /* For DWARF_VALUE_LITERAL, the current literal value's length and
 108      data.  For DWARF_VALUE_IMPLICIT_POINTER, LEN is the offset of the
 109      target DIE of sect_offset kind.  */
 110   ULONGEST len;
 111   const gdb_byte *data;
 112
 113   /* Initialization status of variable: Non-zero if variable has been
 114      initialized; zero otherwise.  */
 115   int initialized;
 116
 117   /* An array of pieces.  PIECES points to its first element;
 118      NUM_PIECES is its length.
 119
 120      Each time DW_OP_piece is executed, we add a new element to the
 121      end of this array, recording the current top of the stack, the
 122      current location, and the size given as the operand to
 123      DW_OP_piece.  We then pop the top value from the stack, reset the
 124      location, and resume evaluation.
 125
 126      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
 127      from the stack.  We do, ensuring that clients of this interface
 128      expecting to see a value left on the top of the stack (say, code
 129      evaluating frame base expressions or CFA's specified with
 130      DW_CFA_def_cfa_expression) will get an error if the expression
 131      actually marks all the values it computes as pieces.
 132
 133      If an expression never uses DW_OP_piece, num_pieces will be zero.
 134      (It would be nice to present these cases as expressions yielding
 135      a single piece, so that callers need not distinguish between the
 136      no-DW_OP_piece and one-DW_OP_piece cases.  But expressions with
 137      no DW_OP_piece operations have no value to place in a piece's
 138      'size' field; the size comes from the surrounding data.  So the
 139      two cases need to be handled separately.)  */
 140   int num_pieces;
 141   struct dwarf_expr_piece *pieces;
 142
 143   /* Return the value of register number REGNUM (a DWARF register number),
 144      read as an address.  */
 145   virtual CORE_ADDR read_addr_from_reg (int regnum) = 0;
 146
 147   /* Return a value of type TYPE, stored in register number REGNUM
 148      of the frame associated to the given BATON.
 149
 150      REGNUM is a DWARF register number.  */
 151   virtual struct value *get_reg_value (struct type *type, int regnum) = 0;
 152
 153   /* Read LENGTH bytes at ADDR into BUF.  */
 154   virtual void read_mem (gdb_byte *buf, CORE_ADDR addr, size_t length) = 0;
 155
 156   /* Return the location expression for the frame base attribute, in
 157      START and LENGTH.  The result must be live until the current
 158      expression evaluation is complete.  */
 159   virtual void get_frame_base (const gdb_byte **start, size_t *length) = 0;
 160
 161   /* Return the CFA for the frame.  */
 162   virtual CORE_ADDR get_frame_cfa () = 0;
 163
 164   /* Return the PC for the frame.  */
 165   virtual CORE_ADDR get_frame_pc ()
 166   {
 167     error (_("%s is invalid in this context"), "DW_OP_GNU_implicit_pointer");
 168   }
 169
 170   /* Return the thread-local storage address for
 171      DW_OP_GNU_push_tls_address or DW_OP_form_tls_address.  */
 172   virtual CORE_ADDR get_tls_address (CORE_ADDR offset) = 0;
 173
 174   /* Execute DW_AT_location expression for the DWARF expression
 175      subroutine in the DIE at DIE_OFFSET in the CU.  Do not touch
 176      STACK while it being passed to and returned from the called DWARF
 177      subroutine.  */
 178   virtual void dwarf_call (cu_offset die_offset) = 0;
 179
 180   /* Return the base type given by the indicated DIE.  This can throw
 181      an exception if the DIE is invalid or does not represent a base
 182      type.  If can also be NULL in the special case where the
 183      callbacks are not performing evaluation, and thus it is
 184      meaningful to substitute a stub type of the correct size.  */
 185   virtual struct type *impl_get_base_type (cu_offset die)
 186   {
 187     /* Anything will do.  */
 188     return builtin_type (this->gdbarch)->builtin_int;
 189   }
 190
 191   /* Push on DWARF stack an entry evaluated for DW_TAG_GNU_call_site's
 192      parameter matching KIND and KIND_U at the caller of specified BATON.
 193      If DEREF_SIZE is not -1 then use DW_AT_GNU_call_site_data_value instead of
 194      DW_AT_GNU_call_site_value.  */
 195   virtual void push_dwarf_reg_entry_value (enum call_site_parameter_kind kind,
 196                                            union call_site_parameter_u kind_u,
 197                                            int deref_size) = 0;
 198
 199   /* Return the address indexed by DW_OP_GNU_addr_index.
 200      This can throw an exception if the index is out of range.  */
 201   virtual CORE_ADDR get_addr_index (unsigned int index) = 0;
 202
 203   /* Return the `object address' for DW_OP_push_object_address.  */
 204   virtual CORE_ADDR get_object_address () = 0;
 205
 206 private:
 207
 208   struct type *address_type () const;
 209   void grow_stack (size_t need);
 210   void push (struct value *value, int in_stack_memory);
 211   int stack_empty_p () const;
 212   void add_piece (ULONGEST size, ULONGEST offset);
 213   struct type *get_base_type (cu_offset die, int size);
 214   void execute_stack_op (const gdb_byte *op_ptr, const gdb_byte *op_end);
 215   void pop ();
 216 };
 217
 218
 219 /* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece.  */
 220 struct dwarf_expr_piece
 221 {
 222   enum dwarf_value_location location;
 223
 224   union
 225   {
 226     struct
 227     {
 228       /* This piece's address, for DWARF_VALUE_MEMORY pieces.  */
 229       CORE_ADDR addr;
 230       /* Non-zero if the piece is known to be in memory and on
 231          the program's stack.  */
 232       int in_stack_memory;
 233     } mem;
 234
 235     /* The piece's register number, for DWARF_VALUE_REGISTER pieces.  */
 236     int regno;
 237
 238     /* The piece's literal value, for DWARF_VALUE_STACK pieces.  */
 239     struct value *value;
 240
 241     struct
 242     {
 243       /* A pointer to the data making up this piece,
 244          for DWARF_VALUE_LITERAL pieces.  */
 245       const gdb_byte *data;
 246       /* The length of the available data.  */
 247       ULONGEST length;
 248     } literal;
 249
 250     /* Used for DWARF_VALUE_IMPLICIT_POINTER.  */
 251     struct
 252     {
 253       /* The referent DIE from DW_OP_GNU_implicit_pointer.  */
 254       sect_offset die;
 255       /* The byte offset into the resulting data.  */
 256       LONGEST offset;
 257     } ptr;
 258   } v;
 259
 260   /* The length of the piece, in bits.  */
 261   ULONGEST size;
 262   /* The piece offset, in bits.  */
 263   ULONGEST offset;
 264 };
 265
 266 void dwarf_expr_require_composition (const gdb_byte *, const gdb_byte *,
 267                                      const char *);
 268
 269 int dwarf_block_to_dwarf_reg (const gdb_byte *buf, const gdb_byte *buf_end);
 270
 271 int dwarf_block_to_dwarf_reg_deref (const gdb_byte *buf,
 272                                     const gdb_byte *buf_end,
 273                                     CORE_ADDR *deref_size_return);
 274
 275 int dwarf_block_to_fb_offset (const gdb_byte *buf, const gdb_byte *buf_end,
 276                               CORE_ADDR *fb_offset_return);
 277
 278 int dwarf_block_to_sp_offset (struct gdbarch *gdbarch, const gdb_byte *buf,
 279                               const gdb_byte *buf_end,
 280                               CORE_ADDR *sp_offset_return);
 281
 282 /* Wrappers around the leb128 reader routines to simplify them for our
 283    purposes.  */
 284
 285 static inline const gdb_byte *
 286 gdb_read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 287                   uint64_t *r)
 288 {
 289   size_t bytes_read = read_uleb128_to_uint64 (buf, buf_end, r);
 290
 291   if (bytes_read == 0)
 292     return NULL;
 293   return buf + bytes_read;
 294 }
 295
 296 static inline const gdb_byte *
 297 gdb_read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 298                   int64_t *r)
 299 {
 300   size_t bytes_read = read_sleb128_to_int64 (buf, buf_end, r);
 301
 302   if (bytes_read == 0)
 303     return NULL;
 304   return buf + bytes_read;
 305 }
 306
 307 static inline const gdb_byte *
 308 gdb_skip_leb128 (const gdb_byte *buf, const gdb_byte *buf_end)
 309 {
 310   size_t bytes_read = skip_leb128 (buf, buf_end);
 311
 312   if (bytes_read == 0)
 313     return NULL;
 314   return buf + bytes_read;
 315 }
 316
 317 extern const gdb_byte *safe_read_uleb128 (const gdb_byte *buf,
 318                                           const gdb_byte *buf_end,
 319                                           uint64_t *r);
 320
 321 extern const gdb_byte *safe_read_sleb128 (const gdb_byte *buf,
 322                                           const gdb_byte *buf_end,
 323                                           int64_t *r);
 324
 325 extern const gdb_byte *safe_skip_leb128 (const gdb_byte *buf,
 326                                          const gdb_byte *buf_end);
 327
 328 #endif /* dwarf2expr.h */