gdb/dwarf2/expr.h

   1 /* DWARF 2 Expression Evaluator.
   2
   3    Copyright (C) 2001-2020 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 dwarf2_per_objfile;
  29
  30 /* The location of a value.  */
  31 enum dwarf_value_location
  32 {
  33   /* The piece is in memory.
  34      The value on the dwarf stack is its address.  */
  35   DWARF_VALUE_MEMORY,
  36
  37   /* The piece is in a register.
  38      The value on the dwarf stack is the register number.  */
  39   DWARF_VALUE_REGISTER,
  40
  41   /* The piece is on the dwarf stack.  */
  42   DWARF_VALUE_STACK,
  43
  44   /* The piece is a literal.  */
  45   DWARF_VALUE_LITERAL,
  46
  47   /* The piece was optimized out.  */
  48   DWARF_VALUE_OPTIMIZED_OUT,
  49
  50   /* The piece is an implicit pointer.  */
  51   DWARF_VALUE_IMPLICIT_POINTER
  52 };
  53
  54 /* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece.  */
  55 struct dwarf_expr_piece
  56 {
  57   enum dwarf_value_location location;
  58
  59   union
  60   {
  61     struct
  62     {
  63       /* This piece's address, for DWARF_VALUE_MEMORY pieces.  */
  64       CORE_ADDR addr;
  65       /* Non-zero if the piece is known to be in memory and on
  66          the program's stack.  */
  67       bool in_stack_memory;
  68     } mem;
  69
  70     /* The piece's register number, for DWARF_VALUE_REGISTER pieces.  */
  71     int regno;
  72
  73     /* The piece's literal value, for DWARF_VALUE_STACK pieces.  */
  74     struct value *value;
  75
  76     struct
  77     {
  78       /* A pointer to the data making up this piece,
  79          for DWARF_VALUE_LITERAL pieces.  */
  80       const gdb_byte *data;
  81       /* The length of the available data.  */
  82       ULONGEST length;
  83     } literal;
  84
  85     /* Used for DWARF_VALUE_IMPLICIT_POINTER.  */
  86     struct
  87     {
  88       /* The referent DIE from DW_OP_implicit_pointer.  */
  89       sect_offset die_sect_off;
  90       /* The byte offset into the resulting data.  */
  91       LONGEST offset;
  92     } ptr;
  93   } v;
  94
  95   /* The length of the piece, in bits.  */
  96   ULONGEST size;
  97   /* The piece offset, in bits.  */
  98   ULONGEST offset;
  99 };
 100
 101 /* The dwarf expression stack.  */
 102
 103 struct dwarf_stack_value
 104 {
 105   dwarf_stack_value (struct value *value_, int in_stack_memory_)
 106   : value (value_), in_stack_memory (in_stack_memory_)
 107   {}
 108
 109   struct value *value;
 110
 111   /* True if the piece is in memory and is known to be on the program's stack.
 112      It is always ok to set this to zero.  This is used, for example, to
 113      optimize memory access from the target.  It can vastly speed up backtraces
 114      on long latency connections when "set stack-cache on".  */
 115   bool in_stack_memory;
 116 };
 117
 118 /* The expression evaluator works with a dwarf_expr_context, describing
 119    its current state and its callbacks.  */
 120 struct dwarf_expr_context
 121 {
 122   dwarf_expr_context (dwarf2_per_objfile *per_objfile);
 123   virtual ~dwarf_expr_context () = default;
 124
 125   void push_address (CORE_ADDR value, bool in_stack_memory);
 126   void eval (const gdb_byte *addr, size_t len);
 127   struct value *fetch (int n);
 128   CORE_ADDR fetch_address (int n);
 129   bool fetch_in_stack_memory (int n);
 130
 131   /* The stack of values.  */
 132   std::vector<dwarf_stack_value> stack;
 133
 134   /* Target architecture to use for address operations.  */
 135   struct gdbarch *gdbarch;
 136
 137   /* Target address size in bytes.  */
 138   int addr_size;
 139
 140   /* DW_FORM_ref_addr size in bytes.  If -1 DWARF is executed from a frame
 141      context and operations depending on DW_FORM_ref_addr are not allowed.  */
 142   int ref_addr_size;
 143
 144   /* The current depth of dwarf expression recursion, via DW_OP_call*,
 145      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
 146      depth we'll tolerate before raising an error.  */
 147   int recursion_depth, max_recursion_depth;
 148
 149   /* Location of the value.  */
 150   enum dwarf_value_location location;
 151
 152   /* For DWARF_VALUE_LITERAL, the current literal value's length and
 153      data.  For DWARF_VALUE_IMPLICIT_POINTER, LEN is the offset of the
 154      target DIE of sect_offset kind.  */
 155   ULONGEST len;
 156   const gdb_byte *data;
 157
 158   /* Initialization status of variable: Non-zero if variable has been
 159      initialized; zero otherwise.  */
 160   int initialized;
 161
 162   /* A vector of pieces.
 163
 164      Each time DW_OP_piece is executed, we add a new element to the
 165      end of this array, recording the current top of the stack, the
 166      current location, and the size given as the operand to
 167      DW_OP_piece.  We then pop the top value from the stack, reset the
 168      location, and resume evaluation.
 169
 170      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
 171      from the stack.  We do, ensuring that clients of this interface
 172      expecting to see a value left on the top of the stack (say, code
 173      evaluating frame base expressions or CFA's specified with
 174      DW_CFA_def_cfa_expression) will get an error if the expression
 175      actually marks all the values it computes as pieces.
 176
 177      If an expression never uses DW_OP_piece, num_pieces will be zero.
 178      (It would be nice to present these cases as expressions yielding
 179      a single piece, so that callers need not distinguish between the
 180      no-DW_OP_piece and one-DW_OP_piece cases.  But expressions with
 181      no DW_OP_piece operations have no value to place in a piece's
 182      'size' field; the size comes from the surrounding data.  So the
 183      two cases need to be handled separately.)  */
 184   std::vector<dwarf_expr_piece> pieces;
 185
 186   /* We evaluate the expression in the context of this objfile.  */
 187   dwarf2_per_objfile *per_objfile;
 188
 189   /* Return the value of register number REGNUM (a DWARF register number),
 190      read as an address.  */
 191   virtual CORE_ADDR read_addr_from_reg (int regnum) = 0;
 192
 193   /* Return a value of type TYPE, stored in register number REGNUM
 194      of the frame associated to the given BATON.
 195
 196      REGNUM is a DWARF register number.  */
 197   virtual struct value *get_reg_value (struct type *type, int regnum) = 0;
 198
 199   /* Read LENGTH bytes at ADDR into BUF.  */
 200   virtual void read_mem (gdb_byte *buf, CORE_ADDR addr, size_t length) = 0;
 201
 202   /* Return the location expression for the frame base attribute, in
 203      START and LENGTH.  The result must be live until the current
 204      expression evaluation is complete.  */
 205   virtual void get_frame_base (const gdb_byte **start, size_t *length) = 0;
 206
 207   /* Return the CFA for the frame.  */
 208   virtual CORE_ADDR get_frame_cfa () = 0;
 209
 210   /* Return the PC for the frame.  */
 211   virtual CORE_ADDR get_frame_pc ()
 212   {
 213     error (_("%s is invalid in this context"), "DW_OP_implicit_pointer");
 214   }
 215
 216   /* Return the thread-local storage address for
 217      DW_OP_GNU_push_tls_address or DW_OP_form_tls_address.  */
 218   virtual CORE_ADDR get_tls_address (CORE_ADDR offset) = 0;
 219
 220   /* Execute DW_AT_location expression for the DWARF expression
 221      subroutine in the DIE at DIE_CU_OFF in the CU.  Do not touch
 222      STACK while it being passed to and returned from the called DWARF
 223      subroutine.  */
 224   virtual void dwarf_call (cu_offset die_cu_off) = 0;
 225
 226   /* Execute "variable value" operation on the DIE at SECT_OFF.  */
 227   virtual struct value *dwarf_variable_value (sect_offset sect_off) = 0;
 228
 229   /* Return the base type given by the indicated DIE at DIE_CU_OFF.
 230      This can throw an exception if the DIE is invalid or does not
 231      represent a base type.  SIZE is non-zero if this function should
 232      verify that the resulting type has the correct size.  */
 233   virtual struct type *get_base_type (cu_offset die_cu_off, int size)
 234   {
 235     /* Anything will do.  */
 236     return builtin_type (this->gdbarch)->builtin_int;
 237   }
 238
 239   /* Push on DWARF stack an entry evaluated for DW_TAG_call_site's
 240      parameter matching KIND and KIND_U at the caller of specified BATON.
 241      If DEREF_SIZE is not -1 then use DW_AT_call_data_value instead of
 242      DW_AT_call_value.  */
 243   virtual void push_dwarf_reg_entry_value (enum call_site_parameter_kind kind,
 244                                            union call_site_parameter_u kind_u,
 245                                            int deref_size) = 0;
 246
 247   /* Return the address indexed by DW_OP_addrx or DW_OP_GNU_addr_index.
 248      This can throw an exception if the index is out of range.  */
 249   virtual CORE_ADDR get_addr_index (unsigned int index) = 0;
 250
 251   /* Return the `object address' for DW_OP_push_object_address.  */
 252   virtual CORE_ADDR get_object_address () = 0;
 253
 254 private:
 255
 256   struct type *address_type () const;
 257   void push (struct value *value, bool in_stack_memory);
 258   bool stack_empty_p () const;
 259   void add_piece (ULONGEST size, ULONGEST offset);
 260   void execute_stack_op (const gdb_byte *op_ptr, const gdb_byte *op_end);
 261   void pop ();
 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 */