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