gdb/dwarf2/expr.h

   1 /* DWARF 2 Expression Evaluator.
   2
   3    Copyright (C) 2001-2021 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 = nullptr;
 136
 137   /* Target address size in bytes.  */
 138   int addr_size = 0;
 139
 140   /* The current depth of dwarf expression recursion, via DW_OP_call*,
 141      DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
 142      depth we'll tolerate before raising an error.  */
 143   int recursion_depth = 0, max_recursion_depth = 0x100;
 144
 145   /* Location of the value.  */
 146   dwarf_value_location location = DWARF_VALUE_MEMORY;
 147
 148   /* For DWARF_VALUE_LITERAL, the current literal value's length and
 149      data.  For DWARF_VALUE_IMPLICIT_POINTER, LEN is the offset of the
 150      target DIE of sect_offset kind.  */
 151   ULONGEST len = 0;
 152   const gdb_byte *data = nullptr;
 153
 154   /* Initialization status of variable: Non-zero if variable has been
 155      initialized; zero otherwise.  */
 156   int initialized = 0;
 157
 158   /* A vector of pieces.
 159
 160      Each time DW_OP_piece is executed, we add a new element to the
 161      end of this array, recording the current top of the stack, the
 162      current location, and the size given as the operand to
 163      DW_OP_piece.  We then pop the top value from the stack, reset the
 164      location, and resume evaluation.
 165
 166      The Dwarf spec doesn't say whether DW_OP_piece pops the top value
 167      from the stack.  We do, ensuring that clients of this interface
 168      expecting to see a value left on the top of the stack (say, code
 169      evaluating frame base expressions or CFA's specified with
 170      DW_CFA_def_cfa_expression) will get an error if the expression
 171      actually marks all the values it computes as pieces.
 172
 173      If an expression never uses DW_OP_piece, num_pieces will be zero.
 174      (It would be nice to present these cases as expressions yielding
 175      a single piece, so that callers need not distinguish between the
 176      no-DW_OP_piece and one-DW_OP_piece cases.  But expressions with
 177      no DW_OP_piece operations have no value to place in a piece's
 178      'size' field; the size comes from the surrounding data.  So the
 179      two cases need to be handled separately.)  */
 180   std::vector<dwarf_expr_piece> pieces;
 181
 182   /* We evaluate the expression in the context of this objfile.  */
 183   dwarf2_per_objfile *per_objfile;
 184
 185   /* Frame information used for the evaluation.  */
 186   frame_info *frame = nullptr;
 187
 188   /* Compilation unit used for the evaluation.  */
 189   dwarf2_per_cu_data *per_cu = nullptr;
 190
 191   /* Object address used for the evaluation.  */
 192   CORE_ADDR obj_address = 0;
 193
 194   /* Read LENGTH bytes at ADDR into BUF.  */
 195   virtual void read_mem (gdb_byte *buf, CORE_ADDR addr, size_t length);
 196
 197   /* Return the `object address' for DW_OP_push_object_address.  */
 198   virtual CORE_ADDR get_object_address ()
 199   {
 200     if (obj_address == 0)
 201       error (_("Location address is not set."));
 202     return obj_address;
 203   }
 204
 205 private:
 206
 207   struct type *address_type () const;
 208   void push (struct value *value, bool in_stack_memory);
 209   bool stack_empty_p () const;
 210   void add_piece (ULONGEST size, ULONGEST offset);
 211   void execute_stack_op (const gdb_byte *op_ptr, const gdb_byte *op_end);
 212   void pop ();
 213
 214   /* Return the location expression for the frame base attribute, in
 215      START and LENGTH.  The result must be live until the current
 216      expression evaluation is complete.  */
 217   void get_frame_base (const gdb_byte **start, size_t *length);
 218
 219   /* Return the base type given by the indicated DIE at DIE_CU_OFF.
 220      This can throw an exception if the DIE is invalid or does not
 221      represent a base type.  */
 222   struct type *get_base_type (cu_offset die_cu_off);
 223
 224   /* Execute DW_AT_location expression for the DWARF expression
 225      subroutine in the DIE at DIE_CU_OFF in the CU.  Do not touch
 226      STACK while it being passed to and returned from the called DWARF
 227      subroutine.  */
 228   void dwarf_call (cu_offset die_cu_off);
 229
 230   /* Push on DWARF stack an entry evaluated for DW_TAG_call_site's
 231      parameter matching KIND and KIND_U at the caller of specified BATON.
 232      If DEREF_SIZE is not -1 then use DW_AT_call_data_value instead of
 233      DW_AT_call_value.  */
 234   void push_dwarf_reg_entry_value (call_site_parameter_kind kind,
 235                                    call_site_parameter_u kind_u,
 236                                    int deref_size);
 237 };
 238
 239 /* Return the value of register number REG (a DWARF register number),
 240    read as an address in a given FRAME.  */
 241 CORE_ADDR read_addr_from_reg (frame_info *frame, int reg);
 242
 243 void dwarf_expr_require_composition (const gdb_byte *, const gdb_byte *,
 244                                      const char *);
 245
 246 int dwarf_block_to_dwarf_reg (const gdb_byte *buf, const gdb_byte *buf_end);
 247
 248 int dwarf_block_to_dwarf_reg_deref (const gdb_byte *buf,
 249                                     const gdb_byte *buf_end,
 250                                     CORE_ADDR *deref_size_return);
 251
 252 int dwarf_block_to_fb_offset (const gdb_byte *buf, const gdb_byte *buf_end,
 253                               CORE_ADDR *fb_offset_return);
 254
 255 int dwarf_block_to_sp_offset (struct gdbarch *gdbarch, const gdb_byte *buf,
 256                               const gdb_byte *buf_end,
 257                               CORE_ADDR *sp_offset_return);
 258
 259 /* Wrappers around the leb128 reader routines to simplify them for our
 260    purposes.  */
 261
 262 static inline const gdb_byte *
 263 gdb_read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 264                   uint64_t *r)
 265 {
 266   size_t bytes_read = read_uleb128_to_uint64 (buf, buf_end, r);
 267
 268   if (bytes_read == 0)
 269     return NULL;
 270   return buf + bytes_read;
 271 }
 272
 273 static inline const gdb_byte *
 274 gdb_read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
 275                   int64_t *r)
 276 {
 277   size_t bytes_read = read_sleb128_to_int64 (buf, buf_end, r);
 278
 279   if (bytes_read == 0)
 280     return NULL;
 281   return buf + bytes_read;
 282 }
 283
 284 static inline const gdb_byte *
 285 gdb_skip_leb128 (const gdb_byte *buf, const gdb_byte *buf_end)
 286 {
 287   size_t bytes_read = skip_leb128 (buf, buf_end);
 288
 289   if (bytes_read == 0)
 290     return NULL;
 291   return buf + bytes_read;
 292 }
 293
 294 extern const gdb_byte *safe_read_uleb128 (const gdb_byte *buf,
 295                                           const gdb_byte *buf_end,
 296                                           uint64_t *r);
 297
 298 extern const gdb_byte *safe_read_sleb128 (const gdb_byte *buf,
 299                                           const gdb_byte *buf_end,
 300                                           int64_t *r);
 301
 302 extern const gdb_byte *safe_skip_leb128 (const gdb_byte *buf,
 303                                          const gdb_byte *buf_end);
 304
 305 #endif /* dwarf2expr.h */