gdb/dwarf2expr.h

   1 /* DWARF 2 Expression Evaluator.
   2
   3    Copyright (C) 2001-2017 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   virtual ~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_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_CU_OFF 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_cu_off) = 0;
 179
 180   /* Return the base type given by the indicated DIE at DIE_CU_OFF.
 181      This can throw an exception if the DIE is invalid or does not
 182      represent a base type.  SIZE is non-zero if this function should
 183      verify that the resulting type has the correct size.  */
 184   virtual struct type *get_base_type (cu_offset die_cu_off, int size)
 185   {
 186     /* Anything will do.  */
 187     return builtin_type (this->gdbarch)->builtin_int;
 188   }
 189
 190   /* Push on DWARF stack an entry evaluated for DW_TAG_call_site's
 191      parameter matching KIND and KIND_U at the caller of specified BATON.
 192      If DEREF_SIZE is not -1 then use DW_AT_call_data_value instead of
 193      DW_AT_call_value.  */
 194   virtual void push_dwarf_reg_entry_value (enum call_site_parameter_kind kind,
 195                                            union call_site_parameter_u kind_u,
 196                                            int deref_size) = 0;
 197
 198   /* Return the address indexed by DW_OP_GNU_addr_index.
 199      This can throw an exception if the index is out of range.  */
 200   virtual CORE_ADDR get_addr_index (unsigned int index) = 0;
 201
 202   /* Return the `object address' for DW_OP_push_object_address.  */
 203   virtual CORE_ADDR get_object_address () = 0;
 204
 205 private:
 206
 207   struct type *address_type () const;
 208   void grow_stack (size_t need);
 209   void push (struct value *value, int in_stack_memory);
 210   int stack_empty_p () const;
 211   void add_piece (ULONGEST size, ULONGEST offset);
 212   void execute_stack_op (const gdb_byte *op_ptr, const gdb_byte *op_end);
 213   void pop ();
 214 };
 215
 216
 217 /* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece.  */
 218 struct dwarf_expr_piece
 219 {
 220   enum dwarf_value_location location;
 221
 222   union
 223   {
 224     struct
 225     {
 226       /* This piece's address, for DWARF_VALUE_MEMORY pieces.  */
 227       CORE_ADDR addr;
 228       /* Non-zero if the piece is known to be in memory and on
 229          the program's stack.  */
 230       int in_stack_memory;
 231     } mem;
 232
 233     /* The piece's register number, for DWARF_VALUE_REGISTER pieces.  */
 234     int regno;
 235
 236     /* The piece's literal value, for DWARF_VALUE_STACK pieces.  */
 237     struct value *value;
 238
 239     struct
 240     {
 241       /* A pointer to the data making up this piece,
 242          for DWARF_VALUE_LITERAL pieces.  */
 243       const gdb_byte *data;
 244       /* The length of the available data.  */
 245       ULONGEST length;
 246     } literal;
 247
 248     /* Used for DWARF_VALUE_IMPLICIT_POINTER.  */
 249     struct
 250     {
 251       /* The referent DIE from DW_OP_implicit_pointer.  */
 252       sect_offset die_sect_off;
 253       /* The byte offset into the resulting data.  */
 254       LONGEST offset;
 255     } ptr;
 256   } v;
 257
 258   /* The length of the piece, in bits.  */
 259   ULONGEST size;
 260   /* The piece offset, in bits.  */
 261   ULONGEST offset;
 262 };
 263
 264 void dwarf_expr_require_composition (const gdb_byte *, const gdb_byte *,
 265                                      const char *);
 266
 267 int dwarf_block_to_dwarf_reg (const gdb_byte *buf, const gdb_byte *buf_end);
 268
 269 int dwarf_block_to_dwarf_reg_deref (const gdb_byte *buf,
 270                                     const gdb_byte *buf_end,
 271                                     CORE_ADDR *deref_size_return);
 272
 273 int dwarf_block_to_fb_offset (const gdb_byte *buf, const gdb_byte *buf_end,
 274                               CORE_ADDR *fb_offset_return);
 275
 276 int dwarf_block_to_sp_offset (struct gdbarch *gdbarch, const gdb_byte *buf,
 277                               const gdb_byte *buf_end,
 278                               CORE_ADDR *sp_offset_return);
 279
 280 /* Wrappers around the leb128 reader routines to simplify them for our
 281    purposes.  */
 282
 283 static inline const gdb_byte *
 284 gdb_read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 285                   uint64_t *r)
 286 {
 287   size_t bytes_read = read_uleb128_to_uint64 (buf, buf_end, r);
 288
 289   if (bytes_read == 0)
 290     return NULL;
 291   return buf + bytes_read;
 292 }
 293
 294 static inline const gdb_byte *
 295 gdb_read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 296                   int64_t *r)
 297 {
 298   size_t bytes_read = read_sleb128_to_int64 (buf, buf_end, r);
 299
 300   if (bytes_read == 0)
 301     return NULL;
 302   return buf + bytes_read;
 303 }
 304
 305 static inline const gdb_byte *
 306 gdb_skip_leb128 (const gdb_byte *buf, const gdb_byte *buf_end)
 307 {
 308   size_t bytes_read = skip_leb128 (buf, buf_end);
 309
 310   if (bytes_read == 0)
 311     return NULL;
 312   return buf + bytes_read;
 313 }
 314
 315 extern const gdb_byte *safe_read_uleb128 (const gdb_byte *buf,
 316                                           const gdb_byte *buf_end,
 317                                           uint64_t *r);
 318
 319 extern const gdb_byte *safe_read_sleb128 (const gdb_byte *buf,
 320                                           const gdb_byte *buf_end,
 321                                           int64_t *r);
 322
 323 extern const gdb_byte *safe_skip_leb128 (const gdb_byte *buf,
 324                                          const gdb_byte *buf_end);
 325
 326 #endif /* dwarf2expr.h */