gdb/dwarf2read.h

   1 /* DWARF 2 debugging format support for GDB.
   2
   3    Copyright (C) 1994-2019 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 <unordered_map>
  24 #include "dwarf-index-cache.h"
  25 #include "filename-seen-cache.h"
  26 #include "gdb_obstack.h"
  27 #include "gdbsupport/hash_enum.h"
  28
  29 /* Hold 'maintenance (set|show) dwarf' commands.  */
  30 extern struct cmd_list_element *set_dwarf_cmdlist;
  31 extern struct cmd_list_element *show_dwarf_cmdlist;
  32
  33 typedef struct dwarf2_per_cu_data *dwarf2_per_cu_ptr;
  34 DEF_VEC_P (dwarf2_per_cu_ptr);
  35
  36 extern bool dwarf_always_disassemble;
  37
  38 /* A descriptor for dwarf sections.
  39
  40    S.ASECTION, SIZE are typically initialized when the objfile is first
  41    scanned.  BUFFER, READIN are filled in later when the section is read.
  42    If the section contained compressed data then SIZE is updated to record
  43    the uncompressed size of the section.
  44
  45    DWP file format V2 introduces a wrinkle that is easiest to handle by
  46    creating the concept of virtual sections contained within a real section.
  47    In DWP V2 the sections of the input DWO files are concatenated together
  48    into one section, but section offsets are kept relative to the original
  49    input section.
  50    If this is a virtual dwp-v2 section, S.CONTAINING_SECTION is a backlink to
  51    the real section this "virtual" section is contained in, and BUFFER,SIZE
  52    describe the virtual section.  */
  53
  54 struct dwarf2_section_info
  55 {
  56   union
  57   {
  58     /* If this is a real section, the bfd section.  */
  59     asection *section;
  60     /* If this is a virtual section, pointer to the containing ("real")
  61        section.  */
  62     struct dwarf2_section_info *containing_section;
  63   } s;
  64   /* Pointer to section data, only valid if readin.  */
  65   const gdb_byte *buffer;
  66   /* The size of the section, real or virtual.  */
  67   bfd_size_type size;
  68   /* If this is a virtual section, the offset in the real section.
  69      Only valid if is_virtual.  */
  70   bfd_size_type virtual_offset;
  71   /* True if we have tried to read this section.  */
  72   bool readin;
  73   /* True if this is a virtual section, False otherwise.
  74      This specifies which of s.section and s.containing_section to use.  */
  75   bool is_virtual;
  76 };
  77
  78 /* Read the contents of the section INFO.
  79    OBJFILE is the main object file, but not necessarily the file where
  80    the section comes from.  E.g., for DWO files the bfd of INFO is the bfd
  81    of the DWO file.
  82    If the section is compressed, uncompress it before returning.  */
  83
  84 void dwarf2_read_section (struct objfile *objfile, dwarf2_section_info *info);
  85
  86 struct tu_stats
  87 {
  88   int nr_uniq_abbrev_tables;
  89   int nr_symtabs;
  90   int nr_symtab_sharers;
  91   int nr_stmt_less_type_units;
  92   int nr_all_type_units_reallocs;
  93 };
  94
  95 struct dwarf2_debug_sections;
  96 struct mapped_index;
  97 struct mapped_debug_names;
  98 struct signatured_type;
  99 struct die_info;
 100 typedef struct die_info *die_info_ptr;
 101
 102 /* Collection of data recorded per objfile.
 103    This hangs off of dwarf2_objfile_data_key.  */
 104
 105 struct dwarf2_per_objfile
 106 {
 107   /* Construct a dwarf2_per_objfile for OBJFILE.  NAMES points to the
 108      dwarf2 section names, or is NULL if the standard ELF names are
 109      used.  */
 110   dwarf2_per_objfile (struct objfile *objfile,
 111                       const dwarf2_debug_sections *names);
 112
 113   ~dwarf2_per_objfile ();
 114
 115   DISABLE_COPY_AND_ASSIGN (dwarf2_per_objfile);
 116
 117   /* Return the CU/TU given its index.
 118
 119      This is intended for loops like:
 120
 121      for (i = 0; i < (dwarf2_per_objfile->n_comp_units
 122                       + dwarf2_per_objfile->n_type_units); ++i)
 123        {
 124          dwarf2_per_cu_data *per_cu = dwarf2_per_objfile->get_cutu (i);
 125
 126          ...;
 127        }
 128   */
 129   dwarf2_per_cu_data *get_cutu (int index);
 130
 131   /* Return the CU given its index.
 132      This differs from get_cutu in that it's for when you know INDEX refers to a
 133      CU.  */
 134   dwarf2_per_cu_data *get_cu (int index);
 135
 136   /* Return the TU given its index.
 137      This differs from get_cutu in that it's for when you know INDEX refers to a
 138      TU.  */
 139   signatured_type *get_tu (int index);
 140
 141   /* Free all cached compilation units.  */
 142   void free_cached_comp_units ();
 143 private:
 144   /* This function is mapped across the sections and remembers the
 145      offset and size of each of the debugging sections we are
 146      interested in.  */
 147   void locate_sections (bfd *abfd, asection *sectp,
 148                         const dwarf2_debug_sections &names);
 149
 150 public:
 151   dwarf2_section_info info {};
 152   dwarf2_section_info abbrev {};
 153   dwarf2_section_info line {};
 154   dwarf2_section_info loc {};
 155   dwarf2_section_info loclists {};
 156   dwarf2_section_info macinfo {};
 157   dwarf2_section_info macro {};
 158   dwarf2_section_info str {};
 159   dwarf2_section_info line_str {};
 160   dwarf2_section_info ranges {};
 161   dwarf2_section_info rnglists {};
 162   dwarf2_section_info addr {};
 163   dwarf2_section_info frame {};
 164   dwarf2_section_info eh_frame {};
 165   dwarf2_section_info gdb_index {};
 166   dwarf2_section_info debug_names {};
 167   dwarf2_section_info debug_aranges {};
 168
 169   std::vector<dwarf2_section_info> types;
 170
 171   /* Back link.  */
 172   struct objfile *objfile = NULL;
 173
 174   /* Table of all the compilation units.  This is used to locate
 175      the target compilation unit of a particular reference.  */
 176   std::vector<dwarf2_per_cu_data *> all_comp_units;
 177
 178   /* The .debug_types-related CUs (TUs).  */
 179   std::vector<signatured_type *> all_type_units;
 180
 181   /* Table of struct type_unit_group objects.
 182      The hash key is the DW_AT_stmt_list value.  */
 183   htab_t type_unit_groups {};
 184
 185   /* A table mapping .debug_types signatures to its signatured_type entry.
 186      This is NULL if the .debug_types section hasn't been read in yet.  */
 187   htab_t signatured_types {};
 188
 189   /* Type unit statistics, to see how well the scaling improvements
 190      are doing.  */
 191   struct tu_stats tu_stats {};
 192
 193   /* A chain of compilation units that are currently read in, so that
 194      they can be freed later.  */
 195   dwarf2_per_cu_data *read_in_chain = NULL;
 196
 197   /* A table mapping DW_AT_dwo_name values to struct dwo_file objects.
 198      This is NULL if the table hasn't been allocated yet.  */
 199   htab_up dwo_files;
 200
 201   /* True if we've checked for whether there is a DWP file.  */
 202   bool dwp_checked = false;
 203
 204   /* The DWP file if there is one, or NULL.  */
 205   std::unique_ptr<struct dwp_file> dwp_file;
 206
 207   /* The shared '.dwz' file, if one exists.  This is used when the
 208      original data was compressed using 'dwz -m'.  */
 209   std::unique_ptr<struct dwz_file> dwz_file;
 210
 211   /* A flag indicating whether this objfile has a section loaded at a
 212      VMA of 0.  */
 213   bool has_section_at_zero = false;
 214
 215   /* True if we are using the mapped index,
 216      or we are faking it for OBJF_READNOW's sake.  */
 217   bool using_index = false;
 218
 219   /* The mapped index, or NULL if .gdb_index is missing or not being used.  */
 220   std::unique_ptr<mapped_index> index_table;
 221
 222   /* The mapped index, or NULL if .debug_names is missing or not being used.  */
 223   std::unique_ptr<mapped_debug_names> debug_names_table;
 224
 225   /* When using index_table, this keeps track of all quick_file_names entries.
 226      TUs typically share line table entries with a CU, so we maintain a
 227      separate table of all line table entries to support the sharing.
 228      Note that while there can be way more TUs than CUs, we've already
 229      sorted all the TUs into "type unit groups", grouped by their
 230      DW_AT_stmt_list value.  Therefore the only sharing done here is with a
 231      CU and its associated TU group if there is one.  */
 232   htab_t quick_file_names_table {};
 233
 234   /* Set during partial symbol reading, to prevent queueing of full
 235      symbols.  */
 236   bool reading_partial_symbols = false;
 237
 238   /* Table mapping type DIEs to their struct type *.
 239      This is NULL if not allocated yet.
 240      The mapping is done via (CU/TU + DIE offset) -> type.  */
 241   htab_t die_type_hash {};
 242
 243   /* The CUs we recently read.  */
 244   std::vector<dwarf2_per_cu_data *> just_read_cus;
 245
 246   /* Table containing line_header indexed by offset and offset_in_dwz.  */
 247   htab_t line_header_hash {};
 248
 249   /* Table containing all filenames.  This is an optional because the
 250      table is lazily constructed on first access.  */
 251   gdb::optional<filename_seen_cache> filenames_cache;
 252
 253   /* If we loaded the index from an external file, this contains the
 254      resources associated to the open file, memory mapping, etc.  */
 255   std::unique_ptr<index_cache_resource> index_cache_res;
 256
 257   /* Mapping from abstract origin DIE to concrete DIEs that reference it as
 258      DW_AT_abstract_origin.  */
 259   std::unordered_map<sect_offset, std::vector<sect_offset>, \
 260                      gdb::hash_enum<sect_offset>> \
 261     abstract_to_concrete;
 262 };
 263
 264 /* Get the dwarf2_per_objfile associated to OBJFILE.  */
 265
 266 dwarf2_per_objfile *get_dwarf2_per_objfile (struct objfile *objfile);
 267
 268 /* Persistent data held for a compilation unit, even when not
 269    processing it.  We put a pointer to this structure in the
 270    read_symtab_private field of the psymtab.  */
 271
 272 struct dwarf2_per_cu_data
 273 {
 274   /* The start offset and length of this compilation unit.
 275      NOTE: Unlike comp_unit_head.length, this length includes
 276      initial_length_size.
 277      If the DIE refers to a DWO file, this is always of the original die,
 278      not the DWO file.  */
 279   sect_offset sect_off;
 280   unsigned int length;
 281
 282   /* DWARF standard version this data has been read from (such as 4 or 5).  */
 283   short dwarf_version;
 284
 285   /* Flag indicating this compilation unit will be read in before
 286      any of the current compilation units are processed.  */
 287   unsigned int queued : 1;
 288
 289   /* This flag will be set when reading partial DIEs if we need to load
 290      absolutely all DIEs for this compilation unit, instead of just the ones
 291      we think are interesting.  It gets set if we look for a DIE in the
 292      hash table and don't find it.  */
 293   unsigned int load_all_dies : 1;
 294
 295   /* Non-zero if this CU is from .debug_types.
 296      Struct dwarf2_per_cu_data is contained in struct signatured_type iff
 297      this is non-zero.  */
 298   unsigned int is_debug_types : 1;
 299
 300   /* Non-zero if this CU is from the .dwz file.  */
 301   unsigned int is_dwz : 1;
 302
 303   /* Non-zero if reading a TU directly from a DWO file, bypassing the stub.
 304      This flag is only valid if is_debug_types is true.
 305      We can't read a CU directly from a DWO file: There are required
 306      attributes in the stub.  */
 307   unsigned int reading_dwo_directly : 1;
 308
 309   /* Non-zero if the TU has been read.
 310      This is used to assist the "Stay in DWO Optimization" for Fission:
 311      When reading a DWO, it's faster to read TUs from the DWO instead of
 312      fetching them from random other DWOs (due to comdat folding).
 313      If the TU has already been read, the optimization is unnecessary
 314      (and unwise - we don't want to change where gdb thinks the TU lives
 315      "midflight").
 316      This flag is only valid if is_debug_types is true.  */
 317   unsigned int tu_read : 1;
 318
 319   /* The section this CU/TU lives in.
 320      If the DIE refers to a DWO file, this is always the original die,
 321      not the DWO file.  */
 322   struct dwarf2_section_info *section;
 323
 324   /* Set to non-NULL iff this CU is currently loaded.  When it gets freed out
 325      of the CU cache it gets reset to NULL again.  This is left as NULL for
 326      dummy CUs (a CU header, but nothing else).  */
 327   struct dwarf2_cu *cu;
 328
 329   /* The corresponding dwarf2_per_objfile.  */
 330   struct dwarf2_per_objfile *dwarf2_per_objfile;
 331
 332   /* When dwarf2_per_objfile->using_index is true, the 'quick' field
 333      is active.  Otherwise, the 'psymtab' field is active.  */
 334   union
 335   {
 336     /* The partial symbol table associated with this compilation unit,
 337        or NULL for unread partial units.  */
 338     struct partial_symtab *psymtab;
 339
 340     /* Data needed by the "quick" functions.  */
 341     struct dwarf2_per_cu_quick_data *quick;
 342   } v;
 343
 344   /* The CUs we import using DW_TAG_imported_unit.  This is filled in
 345      while reading psymtabs, used to compute the psymtab dependencies,
 346      and then cleared.  Then it is filled in again while reading full
 347      symbols, and only deleted when the objfile is destroyed.
 348
 349      This is also used to work around a difference between the way gold
 350      generates .gdb_index version <=7 and the way gdb does.  Arguably this
 351      is a gold bug.  For symbols coming from TUs, gold records in the index
 352      the CU that includes the TU instead of the TU itself.  This breaks
 353      dw2_lookup_symbol: It assumes that if the index says symbol X lives
 354      in CU/TU Y, then one need only expand Y and a subsequent lookup in Y
 355      will find X.  Alas TUs live in their own symtab, so after expanding CU Y
 356      we need to look in TU Z to find X.  Fortunately, this is akin to
 357      DW_TAG_imported_unit, so we just use the same mechanism: For
 358      .gdb_index version <=7 this also records the TUs that the CU referred
 359      to.  Concurrently with this change gdb was modified to emit version 8
 360      indices so we only pay a price for gold generated indices.
 361      http://sourceware.org/bugzilla/show_bug.cgi?id=15021.  */
 362   VEC (dwarf2_per_cu_ptr) *imported_symtabs;
 363 };
 364
 365 /* Entry in the signatured_types hash table.  */
 366
 367 struct signatured_type
 368 {
 369   /* The "per_cu" object of this type.
 370      This struct is used iff per_cu.is_debug_types.
 371      N.B.: This is the first member so that it's easy to convert pointers
 372      between them.  */
 373   struct dwarf2_per_cu_data per_cu;
 374
 375   /* The type's signature.  */
 376   ULONGEST signature;
 377
 378   /* Offset in the TU of the type's DIE, as read from the TU header.
 379      If this TU is a DWO stub and the definition lives in a DWO file
 380      (specified by DW_AT_GNU_dwo_name), this value is unusable.  */
 381   cu_offset type_offset_in_tu;
 382
 383   /* Offset in the section of the type's DIE.
 384      If the definition lives in a DWO file, this is the offset in the
 385      .debug_types.dwo section.
 386      The value is zero until the actual value is known.
 387      Zero is otherwise not a valid section offset.  */
 388   sect_offset type_offset_in_section;
 389
 390   /* Type units are grouped by their DW_AT_stmt_list entry so that they
 391      can share them.  This points to the containing symtab.  */
 392   struct type_unit_group *type_unit_group;
 393
 394   /* The type.
 395      The first time we encounter this type we fully read it in and install it
 396      in the symbol tables.  Subsequent times we only need the type.  */
 397   struct type *type;
 398
 399   /* Containing DWO unit.
 400      This field is valid iff per_cu.reading_dwo_directly.  */
 401   struct dwo_unit *dwo_unit;
 402 };
 403
 404 typedef struct signatured_type *sig_type_ptr;
 405 DEF_VEC_P (sig_type_ptr);
 406
 407 ULONGEST read_unsigned_leb128 (bfd *, const gdb_byte *, unsigned int *);
 408
 409 /* This represents a '.dwz' file.  */
 410
 411 struct dwz_file
 412 {
 413   dwz_file (gdb_bfd_ref_ptr &&bfd)
 414     : dwz_bfd (std::move (bfd))
 415   {
 416   }
 417
 418   const char *filename () const
 419   {
 420     return bfd_get_filename (this->dwz_bfd);
 421   }
 422
 423   /* A dwz file can only contain a few sections.  */
 424   struct dwarf2_section_info abbrev {};
 425   struct dwarf2_section_info info {};
 426   struct dwarf2_section_info str {};
 427   struct dwarf2_section_info line {};
 428   struct dwarf2_section_info macro {};
 429   struct dwarf2_section_info gdb_index {};
 430   struct dwarf2_section_info debug_names {};
 431
 432   /* The dwz's BFD.  */
 433   gdb_bfd_ref_ptr dwz_bfd;
 434
 435   /* If we loaded the index from an external file, this contains the
 436      resources associated to the open file, memory mapping, etc.  */
 437   std::unique_ptr<index_cache_resource> index_cache_res;
 438 };
 439
 440 /* Open the separate '.dwz' debug file, if needed.  Return NULL if
 441    there is no .gnu_debugaltlink section in the file.  Error if there
 442    is such a section but the file cannot be found.  */
 443
 444 extern struct dwz_file *dwarf2_get_dwz_file
 445     (struct dwarf2_per_objfile *dwarf2_per_objfile);
 446
 447 #endif /* DWARF2READ_H */