gdb/dwarf2/read.h

   1 /* DWARF 2 debugging format support for GDB.
   2
   3    Copyright (C) 1994-2020 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef DWARF2READ_H
  21 #define DWARF2READ_H
  22
  23 #include <queue>
  24 #include <unordered_map>
  25 #include "dwarf2/index-cache.h"
  26 #include "dwarf2/section.h"
  27 #include "filename-seen-cache.h"
  28 #include "gdb_obstack.h"
  29 #include "gdbsupport/hash_enum.h"
  30 #include "psympriv.h"
  31
  32 /* Hold 'maintenance (set|show) dwarf' commands.  */
  33 extern struct cmd_list_element *set_dwarf_cmdlist;
  34 extern struct cmd_list_element *show_dwarf_cmdlist;
  35
  36 struct tu_stats
  37 {
  38   int nr_uniq_abbrev_tables;
  39   int nr_symtabs;
  40   int nr_symtab_sharers;
  41   int nr_stmt_less_type_units;
  42   int nr_all_type_units_reallocs;
  43 };
  44
  45 struct dwarf2_debug_sections;
  46 struct dwarf2_per_cu_data;
  47 struct mapped_index;
  48 struct mapped_debug_names;
  49 struct signatured_type;
  50
  51 /* One item on the queue of compilation units to read in full symbols
  52    for.  */
  53 struct dwarf2_queue_item
  54 {
  55   dwarf2_queue_item (dwarf2_per_cu_data *cu, enum language lang)
  56     : per_cu (cu),
  57       pretend_language (lang)
  58   {
  59   }
  60
  61   ~dwarf2_queue_item ();
  62
  63   DISABLE_COPY_AND_ASSIGN (dwarf2_queue_item);
  64
  65   struct dwarf2_per_cu_data *per_cu;
  66   enum language pretend_language;
  67 };
  68
  69 /* Collection of data recorded per objfile.
  70    This hangs off of dwarf2_objfile_data_key.  */
  71
  72 struct dwarf2_per_objfile
  73 {
  74   /* Construct a dwarf2_per_objfile for OBJFILE.  NAMES points to the
  75      dwarf2 section names, or is NULL if the standard ELF names are
  76      used.  CAN_COPY is true for formats where symbol
  77      interposition is possible and so symbol values must follow copy
  78      relocation rules.  */
  79   dwarf2_per_objfile (struct objfile *objfile,
  80                       const dwarf2_debug_sections *names,
  81                       bool can_copy);
  82
  83   ~dwarf2_per_objfile ();
  84
  85   DISABLE_COPY_AND_ASSIGN (dwarf2_per_objfile);
  86
  87   /* Return the CU/TU given its index.
  88
  89      This is intended for loops like:
  90
  91      for (i = 0; i < (dwarf2_per_objfile->n_comp_units
  92                       + dwarf2_per_objfile->n_type_units); ++i)
  93        {
  94          dwarf2_per_cu_data *per_cu = dwarf2_per_objfile->get_cutu (i);
  95
  96          ...;
  97        }
  98   */
  99   dwarf2_per_cu_data *get_cutu (int index);
 100
 101   /* Return the CU given its index.
 102      This differs from get_cutu in that it's for when you know INDEX refers to a
 103      CU.  */
 104   dwarf2_per_cu_data *get_cu (int index);
 105
 106   /* Return the TU given its index.
 107      This differs from get_cutu in that it's for when you know INDEX refers to a
 108      TU.  */
 109   signatured_type *get_tu (int index);
 110
 111   /* Free all cached compilation units.  */
 112   void free_cached_comp_units ();
 113
 114   /* Return pointer to string at .debug_line_str offset as read from BUF.
 115      BUF is assumed to be in a compilation unit described by CU_HEADER.
 116      Return *BYTES_READ_PTR count of bytes read from BUF.  */
 117   const char *read_line_string (const gdb_byte *buf,
 118                                 const struct comp_unit_head *cu_header,
 119                                 unsigned int *bytes_read_ptr);
 120
 121 private:
 122   /* This function is mapped across the sections and remembers the
 123      offset and size of each of the debugging sections we are
 124      interested in.  */
 125   void locate_sections (bfd *abfd, asection *sectp,
 126                         const dwarf2_debug_sections &names);
 127
 128 public:
 129   /* Objects that can be shared across objfiles are stored in this
 130      obstack or on the psymtab obstack, while objects that are
 131      objfile-specific are stored on the objfile obstack.  */
 132   auto_obstack obstack;
 133
 134   dwarf2_section_info info {};
 135   dwarf2_section_info abbrev {};
 136   dwarf2_section_info line {};
 137   dwarf2_section_info loc {};
 138   dwarf2_section_info loclists {};
 139   dwarf2_section_info macinfo {};
 140   dwarf2_section_info macro {};
 141   dwarf2_section_info str {};
 142   dwarf2_section_info str_offsets {};
 143   dwarf2_section_info line_str {};
 144   dwarf2_section_info ranges {};
 145   dwarf2_section_info rnglists {};
 146   dwarf2_section_info addr {};
 147   dwarf2_section_info frame {};
 148   dwarf2_section_info eh_frame {};
 149   dwarf2_section_info gdb_index {};
 150   dwarf2_section_info debug_names {};
 151   dwarf2_section_info debug_aranges {};
 152
 153   std::vector<dwarf2_section_info> types;
 154
 155   /* Back link.  */
 156   struct objfile *objfile = NULL;
 157
 158   /* Table of all the compilation units.  This is used to locate
 159      the target compilation unit of a particular reference.  */
 160   std::vector<dwarf2_per_cu_data *> all_comp_units;
 161
 162   /* The .debug_types-related CUs (TUs).  */
 163   std::vector<signatured_type *> all_type_units;
 164
 165   /* Table of struct type_unit_group objects.
 166      The hash key is the DW_AT_stmt_list value.  */
 167   htab_up type_unit_groups;
 168
 169   /* A table mapping .debug_types signatures to its signatured_type entry.
 170      This is NULL if the .debug_types section hasn't been read in yet.  */
 171   htab_up signatured_types;
 172
 173   /* Type unit statistics, to see how well the scaling improvements
 174      are doing.  */
 175   struct tu_stats tu_stats {};
 176
 177   /* A chain of compilation units that are currently read in, so that
 178      they can be freed later.  */
 179   dwarf2_per_cu_data *read_in_chain = NULL;
 180
 181   /* A table mapping DW_AT_dwo_name values to struct dwo_file objects.
 182      This is NULL if the table hasn't been allocated yet.  */
 183   htab_up dwo_files;
 184
 185   /* True if we've checked for whether there is a DWP file.  */
 186   bool dwp_checked = false;
 187
 188   /* The DWP file if there is one, or NULL.  */
 189   std::unique_ptr<struct dwp_file> dwp_file;
 190
 191   /* The shared '.dwz' file, if one exists.  This is used when the
 192      original data was compressed using 'dwz -m'.  */
 193   std::unique_ptr<struct dwz_file> dwz_file;
 194
 195   /* Whether copy relocations are supported by this object format.  */
 196   bool can_copy;
 197
 198   /* A flag indicating whether this objfile has a section loaded at a
 199      VMA of 0.  */
 200   bool has_section_at_zero = false;
 201
 202   /* True if we are using the mapped index,
 203      or we are faking it for OBJF_READNOW's sake.  */
 204   bool using_index = false;
 205
 206   /* The mapped index, or NULL if .gdb_index is missing or not being used.  */
 207   std::unique_ptr<mapped_index> index_table;
 208
 209   /* The mapped index, or NULL if .debug_names is missing or not being used.  */
 210   std::unique_ptr<mapped_debug_names> debug_names_table;
 211
 212   /* When using index_table, this keeps track of all quick_file_names entries.
 213      TUs typically share line table entries with a CU, so we maintain a
 214      separate table of all line table entries to support the sharing.
 215      Note that while there can be way more TUs than CUs, we've already
 216      sorted all the TUs into "type unit groups", grouped by their
 217      DW_AT_stmt_list value.  Therefore the only sharing done here is with a
 218      CU and its associated TU group if there is one.  */
 219   htab_up quick_file_names_table;
 220
 221   /* Set during partial symbol reading, to prevent queueing of full
 222      symbols.  */
 223   bool reading_partial_symbols = false;
 224
 225   /* Table mapping type DIEs to their struct type *.
 226      This is NULL if not allocated yet.
 227      The mapping is done via (CU/TU + DIE offset) -> type.  */
 228   htab_up die_type_hash;
 229
 230   /* The CUs we recently read.  */
 231   std::vector<dwarf2_per_cu_data *> just_read_cus;
 232
 233   /* Table containing line_header indexed by offset and offset_in_dwz.  */
 234   htab_up line_header_hash;
 235
 236   /* Table containing all filenames.  This is an optional because the
 237      table is lazily constructed on first access.  */
 238   gdb::optional<filename_seen_cache> filenames_cache;
 239
 240   /* If we loaded the index from an external file, this contains the
 241      resources associated to the open file, memory mapping, etc.  */
 242   std::unique_ptr<index_cache_resource> index_cache_res;
 243
 244   /* Mapping from abstract origin DIE to concrete DIEs that reference it as
 245      DW_AT_abstract_origin.  */
 246   std::unordered_map<sect_offset, std::vector<sect_offset>,
 247                      gdb::hash_enum<sect_offset>>
 248     abstract_to_concrete;
 249
 250   /* CUs that are queued to be read.  */
 251   std::queue<dwarf2_queue_item> queue;
 252 };
 253
 254 /* Get the dwarf2_per_objfile associated to OBJFILE.  */
 255
 256 dwarf2_per_objfile *get_dwarf2_per_objfile (struct objfile *objfile);
 257
 258 /* A partial symtab specialized for DWARF.  */
 259 struct dwarf2_psymtab : public standard_psymtab
 260 {
 261   dwarf2_psymtab (const char *filename, struct objfile *objfile,
 262                   dwarf2_per_cu_data *per_cu)
 263     : standard_psymtab (filename, objfile, 0),
 264       per_cu_data (per_cu)
 265   {
 266   }
 267
 268   void read_symtab (struct objfile *) override;
 269   void expand_psymtab (struct objfile *) override;
 270
 271   struct dwarf2_per_cu_data *per_cu_data;
 272 };
 273
 274 /* Persistent data held for a compilation unit, even when not
 275    processing it.  We put a pointer to this structure in the
 276    psymtab.  */
 277
 278 struct dwarf2_per_cu_data
 279 {
 280   /* The start offset and length of this compilation unit.
 281      NOTE: Unlike comp_unit_head.length, this length includes
 282      initial_length_size.
 283      If the DIE refers to a DWO file, this is always of the original die,
 284      not the DWO file.  */
 285   sect_offset sect_off;
 286   unsigned int length;
 287
 288   /* DWARF standard version this data has been read from (such as 4 or 5).  */
 289   short dwarf_version;
 290
 291   /* Flag indicating this compilation unit will be read in before
 292      any of the current compilation units are processed.  */
 293   unsigned int queued : 1;
 294
 295   /* This flag will be set when reading partial DIEs if we need to load
 296      absolutely all DIEs for this compilation unit, instead of just the ones
 297      we think are interesting.  It gets set if we look for a DIE in the
 298      hash table and don't find it.  */
 299   unsigned int load_all_dies : 1;
 300
 301   /* Non-zero if this CU is from .debug_types.
 302      Struct dwarf2_per_cu_data is contained in struct signatured_type iff
 303      this is non-zero.  */
 304   unsigned int is_debug_types : 1;
 305
 306   /* Non-zero if this CU is from the .dwz file.  */
 307   unsigned int is_dwz : 1;
 308
 309   /* Non-zero if reading a TU directly from a DWO file, bypassing the stub.
 310      This flag is only valid if is_debug_types is true.
 311      We can't read a CU directly from a DWO file: There are required
 312      attributes in the stub.  */
 313   unsigned int reading_dwo_directly : 1;
 314
 315   /* Non-zero if the TU has been read.
 316      This is used to assist the "Stay in DWO Optimization" for Fission:
 317      When reading a DWO, it's faster to read TUs from the DWO instead of
 318      fetching them from random other DWOs (due to comdat folding).
 319      If the TU has already been read, the optimization is unnecessary
 320      (and unwise - we don't want to change where gdb thinks the TU lives
 321      "midflight").
 322      This flag is only valid if is_debug_types is true.  */
 323   unsigned int tu_read : 1;
 324
 325   /* The section this CU/TU lives in.
 326      If the DIE refers to a DWO file, this is always the original die,
 327      not the DWO file.  */
 328   struct dwarf2_section_info *section;
 329
 330   /* Set to non-NULL iff this CU is currently loaded.  When it gets freed out
 331      of the CU cache it gets reset to NULL again.  This is left as NULL for
 332      dummy CUs (a CU header, but nothing else).  */
 333   struct dwarf2_cu *cu;
 334
 335   /* The unit type of this CU.  */
 336   enum dwarf_unit_type unit_type;
 337
 338   /* The language of this CU.  */
 339   enum language lang;
 340
 341   /* The corresponding dwarf2_per_objfile.  */
 342   struct dwarf2_per_objfile *dwarf2_per_objfile;
 343
 344   /* When dwarf2_per_objfile->using_index is true, the 'quick' field
 345      is active.  Otherwise, the 'psymtab' field is active.  */
 346   union
 347   {
 348     /* The partial symbol table associated with this compilation unit,
 349        or NULL for unread partial units.  */
 350     dwarf2_psymtab *psymtab;
 351
 352     /* Data needed by the "quick" functions.  */
 353     struct dwarf2_per_cu_quick_data *quick;
 354   } v;
 355
 356   /* The CUs we import using DW_TAG_imported_unit.  This is filled in
 357      while reading psymtabs, used to compute the psymtab dependencies,
 358      and then cleared.  Then it is filled in again while reading full
 359      symbols, and only deleted when the objfile is destroyed.
 360
 361      This is also used to work around a difference between the way gold
 362      generates .gdb_index version <=7 and the way gdb does.  Arguably this
 363      is a gold bug.  For symbols coming from TUs, gold records in the index
 364      the CU that includes the TU instead of the TU itself.  This breaks
 365      dw2_lookup_symbol: It assumes that if the index says symbol X lives
 366      in CU/TU Y, then one need only expand Y and a subsequent lookup in Y
 367      will find X.  Alas TUs live in their own symtab, so after expanding CU Y
 368      we need to look in TU Z to find X.  Fortunately, this is akin to
 369      DW_TAG_imported_unit, so we just use the same mechanism: For
 370      .gdb_index version <=7 this also records the TUs that the CU referred
 371      to.  Concurrently with this change gdb was modified to emit version 8
 372      indices so we only pay a price for gold generated indices.
 373      http://sourceware.org/bugzilla/show_bug.cgi?id=15021.
 374
 375      This currently needs to be a public member due to how
 376      dwarf2_per_cu_data is allocated and used.  Ideally in future things
 377      could be refactored to make this private.  Until then please try to
 378      avoid direct access to this member, and instead use the helper
 379      functions above.  */
 380   std::vector <dwarf2_per_cu_data *> *imported_symtabs;
 381
 382   /* Return true of IMPORTED_SYMTABS is empty or not yet allocated.  */
 383   bool imported_symtabs_empty () const
 384   {
 385     return (imported_symtabs == nullptr || imported_symtabs->empty ());
 386   }
 387
 388   /* Push P to the back of IMPORTED_SYMTABS, allocated IMPORTED_SYMTABS
 389      first if required.  */
 390   void imported_symtabs_push (dwarf2_per_cu_data *p)
 391   {
 392     if (imported_symtabs == nullptr)
 393       imported_symtabs = new std::vector <dwarf2_per_cu_data *>;
 394     imported_symtabs->push_back (p);
 395   }
 396
 397   /* Return the size of IMPORTED_SYMTABS if it is allocated, otherwise
 398      return 0.  */
 399   size_t imported_symtabs_size () const
 400   {
 401     if (imported_symtabs == nullptr)
 402       return 0;
 403     return imported_symtabs->size ();
 404   }
 405
 406   /* Delete IMPORTED_SYMTABS and set the pointer back to nullptr.  */
 407   void imported_symtabs_free ()
 408   {
 409     delete imported_symtabs;
 410     imported_symtabs = nullptr;
 411   }
 412
 413   /* Return the OBJFILE associated with this compilation unit.  If
 414      this compilation unit came from a separate debuginfo file, then
 415      the master objfile is returned.  */
 416   struct objfile *objfile () const;
 417
 418   /* Return the address size given in the compilation unit header for
 419      this CU.  */
 420   int addr_size () const;
 421
 422   /* Return the offset size given in the compilation unit header for
 423      this CU.  */
 424   int offset_size () const;
 425
 426   /* Return the DW_FORM_ref_addr size given in the compilation unit
 427      header for this CU.  */
 428   int ref_addr_size () const;
 429
 430   /* Return the text offset of the CU.  The returned offset comes from
 431      this CU's objfile.  If this objfile came from a separate
 432      debuginfo file, then the offset may be different from the
 433      corresponding offset in the parent objfile.  */
 434   CORE_ADDR text_offset () const;
 435
 436   /* Return a type that is a generic pointer type, the size of which
 437      matches the address size given in the compilation unit header for
 438      this CU.  */
 439   struct type *addr_type () const;
 440
 441   /* Find an integer type SIZE_IN_BYTES bytes in size and return it.
 442      UNSIGNED_P controls if the integer is unsigned or not.  */
 443   struct type *int_type (int size_in_bytes, bool unsigned_p) const;
 444
 445   /* Find an integer type the same size as the address size given in
 446      the compilation unit header for this CU.  UNSIGNED_P controls if
 447      the integer is unsigned or not.  */
 448   struct type *addr_sized_int_type (bool unsigned_p) const;
 449
 450   /* Return DWARF version number of this CU.  */
 451   short version () const
 452   {
 453     return dwarf_version;
 454   }
 455
 456   /* A type unit group has a per_cu object that is recognized by
 457      having no section.  */
 458   bool type_unit_group_p () const
 459   {
 460     return section == nullptr;
 461   }
 462 };
 463
 464 /* Entry in the signatured_types hash table.  */
 465
 466 struct signatured_type
 467 {
 468   /* The "per_cu" object of this type.
 469      This struct is used iff per_cu.is_debug_types.
 470      N.B.: This is the first member so that it's easy to convert pointers
 471      between them.  */
 472   struct dwarf2_per_cu_data per_cu;
 473
 474   /* The type's signature.  */
 475   ULONGEST signature;
 476
 477   /* Offset in the TU of the type's DIE, as read from the TU header.
 478      If this TU is a DWO stub and the definition lives in a DWO file
 479      (specified by DW_AT_GNU_dwo_name), this value is unusable.  */
 480   cu_offset type_offset_in_tu;
 481
 482   /* Offset in the section of the type's DIE.
 483      If the definition lives in a DWO file, this is the offset in the
 484      .debug_types.dwo section.
 485      The value is zero until the actual value is known.
 486      Zero is otherwise not a valid section offset.  */
 487   sect_offset type_offset_in_section;
 488
 489   /* Type units are grouped by their DW_AT_stmt_list entry so that they
 490      can share them.  This points to the containing symtab.  */
 491   struct type_unit_group *type_unit_group;
 492
 493   /* The type.
 494      The first time we encounter this type we fully read it in and install it
 495      in the symbol tables.  Subsequent times we only need the type.  */
 496   struct type *type;
 497
 498   /* Containing DWO unit.
 499      This field is valid iff per_cu.reading_dwo_directly.  */
 500   struct dwo_unit *dwo_unit;
 501 };
 502
 503 /* Open the separate '.dwz' debug file, if needed.  Return NULL if
 504    there is no .gnu_debugaltlink section in the file.  Error if there
 505    is such a section but the file cannot be found.  */
 506
 507 extern struct dwz_file *dwarf2_get_dwz_file
 508     (struct dwarf2_per_objfile *dwarf2_per_objfile);
 509
 510 /* Return the type of the DIE at DIE_OFFSET in the CU named by
 511    PER_CU.  */
 512
 513 struct type *dwarf2_get_die_type (cu_offset die_offset,
 514                                   struct dwarf2_per_cu_data *per_cu);
 515
 516 /* Given an index in .debug_addr, fetch the value.
 517    NOTE: This can be called during dwarf expression evaluation,
 518    long after the debug information has been read, and thus per_cu->cu
 519    may no longer exist.  */
 520
 521 CORE_ADDR dwarf2_read_addr_index (dwarf2_per_cu_data *per_cu,
 522                                   unsigned int addr_index);
 523
 524 /* Return DWARF block referenced by DW_AT_location of DIE at SECT_OFF at PER_CU.
 525    Returned value is intended for DW_OP_call*.  Returned
 526    dwarf2_locexpr_baton->data has lifetime of
 527    PER_CU->DWARF2_PER_OBJFILE->OBJFILE.  */
 528
 529 struct dwarf2_locexpr_baton dwarf2_fetch_die_loc_sect_off
 530   (sect_offset sect_off, dwarf2_per_cu_data *per_cu,
 531    CORE_ADDR (*get_frame_pc) (void *baton),
 532    void *baton, bool resolve_abstract_p = false);
 533
 534 /* Like dwarf2_fetch_die_loc_sect_off, but take a CU
 535    offset.  */
 536
 537 struct dwarf2_locexpr_baton dwarf2_fetch_die_loc_cu_off
 538   (cu_offset offset_in_cu, dwarf2_per_cu_data *per_cu,
 539    CORE_ADDR (*get_frame_pc) (void *baton),
 540    void *baton);
 541
 542 /* If the DIE at SECT_OFF in PER_CU has a DW_AT_const_value, return a
 543    pointer to the constant bytes and set LEN to the length of the
 544    data.  If memory is needed, allocate it on OBSTACK.  If the DIE
 545    does not have a DW_AT_const_value, return NULL.  */
 546
 547 extern const gdb_byte *dwarf2_fetch_constant_bytes
 548   (sect_offset sect_off, dwarf2_per_cu_data *per_cu, obstack *obstack,
 549    LONGEST *len);
 550
 551 /* Return the type of the die at SECT_OFF in PER_CU.  Return NULL if no
 552    valid type for this die is found.  */
 553
 554 struct type *dwarf2_fetch_die_type_sect_off
 555   (sect_offset sect_off, dwarf2_per_cu_data *per_cu);
 556
 557 /* When non-zero, dump line number entries as they are read in.  */
 558 extern unsigned int dwarf_line_debug;
 559
 560 #endif /* DWARF2READ_H */