gdb/dwarf2read.h

   1 /* DWARF 2 debugging format support for GDB.
   2
   3    Copyright (C) 1994-2018 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 "filename-seen-cache.h"
  24 #include "gdb_obstack.h"
  25
  26 typedef struct dwarf2_per_cu_data *dwarf2_per_cu_ptr;
  27 DEF_VEC_P (dwarf2_per_cu_ptr);
  28
  29 /* A descriptor for dwarf sections.
  30
  31    S.ASECTION, SIZE are typically initialized when the objfile is first
  32    scanned.  BUFFER, READIN are filled in later when the section is read.
  33    If the section contained compressed data then SIZE is updated to record
  34    the uncompressed size of the section.
  35
  36    DWP file format V2 introduces a wrinkle that is easiest to handle by
  37    creating the concept of virtual sections contained within a real section.
  38    In DWP V2 the sections of the input DWO files are concatenated together
  39    into one section, but section offsets are kept relative to the original
  40    input section.
  41    If this is a virtual dwp-v2 section, S.CONTAINING_SECTION is a backlink to
  42    the real section this "virtual" section is contained in, and BUFFER,SIZE
  43    describe the virtual section.  */
  44
  45 struct dwarf2_section_info
  46 {
  47   union
  48   {
  49     /* If this is a real section, the bfd section.  */
  50     asection *section;
  51     /* If this is a virtual section, pointer to the containing ("real")
  52        section.  */
  53     struct dwarf2_section_info *containing_section;
  54   } s;
  55   /* Pointer to section data, only valid if readin.  */
  56   const gdb_byte *buffer;
  57   /* The size of the section, real or virtual.  */
  58   bfd_size_type size;
  59   /* If this is a virtual section, the offset in the real section.
  60      Only valid if is_virtual.  */
  61   bfd_size_type virtual_offset;
  62   /* True if we have tried to read this section.  */
  63   char readin;
  64   /* True if this is a virtual section, False otherwise.
  65      This specifies which of s.section and s.containing_section to use.  */
  66   char is_virtual;
  67 };
  68
  69 typedef struct dwarf2_section_info dwarf2_section_info_def;
  70 DEF_VEC_O (dwarf2_section_info_def);
  71
  72 /* Read the contents of the section INFO.
  73    OBJFILE is the main object file, but not necessarily the file where
  74    the section comes from.  E.g., for DWO files the bfd of INFO is the bfd
  75    of the DWO file.
  76    If the section is compressed, uncompress it before returning.  */
  77
  78 void dwarf2_read_section (struct objfile *objfile, dwarf2_section_info *info);
  79
  80 struct tu_stats
  81 {
  82   int nr_uniq_abbrev_tables;
  83   int nr_symtabs;
  84   int nr_symtab_sharers;
  85   int nr_stmt_less_type_units;
  86   int nr_all_type_units_reallocs;
  87 };
  88
  89 struct dwarf2_debug_sections;
  90 struct mapped_index;
  91 struct mapped_debug_names;
  92 struct signatured_type;
  93
  94 /* Collection of data recorded per objfile.
  95    This hangs off of dwarf2_objfile_data_key.  */
  96
  97 struct dwarf2_per_objfile : public allocate_on_obstack
  98 {
  99   /* Construct a dwarf2_per_objfile for OBJFILE.  NAMES points to the
 100      dwarf2 section names, or is NULL if the standard ELF names are
 101      used.  */
 102   dwarf2_per_objfile (struct objfile *objfile,
 103                       const dwarf2_debug_sections *names);
 104
 105   ~dwarf2_per_objfile ();
 106
 107   DISABLE_COPY_AND_ASSIGN (dwarf2_per_objfile);
 108
 109   /* Return the CU/TU given its index.
 110
 111      This is intended for loops like:
 112
 113      for (i = 0; i < (dwarf2_per_objfile->n_comp_units
 114                       + dwarf2_per_objfile->n_type_units); ++i)
 115        {
 116          dwarf2_per_cu_data *per_cu = dwarf2_per_objfile->get_cutu (i);
 117
 118          ...;
 119        }
 120   */
 121   dwarf2_per_cu_data *get_cutu (int index);
 122
 123   /* Return the CU given its index.
 124      This differs from get_cutu in that it's for when you know INDEX refers to a
 125      CU.  */
 126   dwarf2_per_cu_data *get_cu (int index);
 127
 128   /* Return the TU given its index.
 129      This differs from get_cutu in that it's for when you know INDEX refers to a
 130      TU.  */
 131   signatured_type *get_tu (int index);
 132
 133   /* Free all cached compilation units.  */
 134   void free_cached_comp_units ();
 135 private:
 136   /* This function is mapped across the sections and remembers the
 137      offset and size of each of the debugging sections we are
 138      interested in.  */
 139   void locate_sections (bfd *abfd, asection *sectp,
 140                         const dwarf2_debug_sections &names);
 141
 142 public:
 143   dwarf2_section_info info {};
 144   dwarf2_section_info abbrev {};
 145   dwarf2_section_info line {};
 146   dwarf2_section_info loc {};
 147   dwarf2_section_info loclists {};
 148   dwarf2_section_info macinfo {};
 149   dwarf2_section_info macro {};
 150   dwarf2_section_info str {};
 151   dwarf2_section_info line_str {};
 152   dwarf2_section_info ranges {};
 153   dwarf2_section_info rnglists {};
 154   dwarf2_section_info addr {};
 155   dwarf2_section_info frame {};
 156   dwarf2_section_info eh_frame {};
 157   dwarf2_section_info gdb_index {};
 158   dwarf2_section_info debug_names {};
 159   dwarf2_section_info debug_aranges {};
 160
 161   VEC (dwarf2_section_info_def) *types = NULL;
 162
 163   /* Back link.  */
 164   struct objfile *objfile = NULL;
 165
 166   /* Table of all the compilation units.  This is used to locate
 167      the target compilation unit of a particular reference.  */
 168   std::vector<dwarf2_per_cu_data *> all_comp_units;
 169
 170   /* The number of .debug_types-related CUs.  */
 171   int n_type_units = 0;
 172
 173   /* The number of elements allocated in all_type_units.
 174      If there are skeleton-less TUs, we add them to all_type_units lazily.  */
 175   int n_allocated_type_units = 0;
 176
 177   /* The .debug_types-related CUs (TUs).
 178      This is stored in malloc space because we may realloc it.  */
 179   struct signatured_type **all_type_units = NULL;
 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_t 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   struct dwp_file *dwp_file = NULL;
 206
 207   /* The shared '.dwz' file, if one exists.  This is used when the
 208      original data was compressed using 'dwz -m'.  */
 209   struct dwz_file *dwz_file = NULL;
 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   mapped_index *index_table = NULL;
 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   VEC (dwarf2_per_cu_ptr) *just_read_cus = NULL;
 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
 254 /* Get the dwarf2_per_objfile associated to OBJFILE.  */
 255
 256 dwarf2_per_objfile *get_dwarf2_per_objfile (struct objfile *objfile);
 257
 258 /* Persistent data held for a compilation unit, even when not
 259    processing it.  We put a pointer to this structure in the
 260    read_symtab_private field of the psymtab.  */
 261
 262 struct dwarf2_per_cu_data
 263 {
 264   /* The start offset and length of this compilation unit.
 265      NOTE: Unlike comp_unit_head.length, this length includes
 266      initial_length_size.
 267      If the DIE refers to a DWO file, this is always of the original die,
 268      not the DWO file.  */
 269   sect_offset sect_off;
 270   unsigned int length;
 271
 272   /* DWARF standard version this data has been read from (such as 4 or 5).  */
 273   short dwarf_version;
 274
 275   /* Flag indicating this compilation unit will be read in before
 276      any of the current compilation units are processed.  */
 277   unsigned int queued : 1;
 278
 279   /* This flag will be set when reading partial DIEs if we need to load
 280      absolutely all DIEs for this compilation unit, instead of just the ones
 281      we think are interesting.  It gets set if we look for a DIE in the
 282      hash table and don't find it.  */
 283   unsigned int load_all_dies : 1;
 284
 285   /* Non-zero if this CU is from .debug_types.
 286      Struct dwarf2_per_cu_data is contained in struct signatured_type iff
 287      this is non-zero.  */
 288   unsigned int is_debug_types : 1;
 289
 290   /* Non-zero if this CU is from the .dwz file.  */
 291   unsigned int is_dwz : 1;
 292
 293   /* Non-zero if reading a TU directly from a DWO file, bypassing the stub.
 294      This flag is only valid if is_debug_types is true.
 295      We can't read a CU directly from a DWO file: There are required
 296      attributes in the stub.  */
 297   unsigned int reading_dwo_directly : 1;
 298
 299   /* Non-zero if the TU has been read.
 300      This is used to assist the "Stay in DWO Optimization" for Fission:
 301      When reading a DWO, it's faster to read TUs from the DWO instead of
 302      fetching them from random other DWOs (due to comdat folding).
 303      If the TU has already been read, the optimization is unnecessary
 304      (and unwise - we don't want to change where gdb thinks the TU lives
 305      "midflight").
 306      This flag is only valid if is_debug_types is true.  */
 307   unsigned int tu_read : 1;
 308
 309   /* The section this CU/TU lives in.
 310      If the DIE refers to a DWO file, this is always the original die,
 311      not the DWO file.  */
 312   struct dwarf2_section_info *section;
 313
 314   /* Set to non-NULL iff this CU is currently loaded.  When it gets freed out
 315      of the CU cache it gets reset to NULL again.  This is left as NULL for
 316      dummy CUs (a CU header, but nothing else).  */
 317   struct dwarf2_cu *cu;
 318
 319   /* The corresponding dwarf2_per_objfile.  */
 320   struct dwarf2_per_objfile *dwarf2_per_objfile;
 321
 322   /* When dwarf2_per_objfile->using_index is true, the 'quick' field
 323      is active.  Otherwise, the 'psymtab' field is active.  */
 324   union
 325   {
 326     /* The partial symbol table associated with this compilation unit,
 327        or NULL for unread partial units.  */
 328     struct partial_symtab *psymtab;
 329
 330     /* Data needed by the "quick" functions.  */
 331     struct dwarf2_per_cu_quick_data *quick;
 332   } v;
 333
 334   /* The CUs we import using DW_TAG_imported_unit.  This is filled in
 335      while reading psymtabs, used to compute the psymtab dependencies,
 336      and then cleared.  Then it is filled in again while reading full
 337      symbols, and only deleted when the objfile is destroyed.
 338
 339      This is also used to work around a difference between the way gold
 340      generates .gdb_index version <=7 and the way gdb does.  Arguably this
 341      is a gold bug.  For symbols coming from TUs, gold records in the index
 342      the CU that includes the TU instead of the TU itself.  This breaks
 343      dw2_lookup_symbol: It assumes that if the index says symbol X lives
 344      in CU/TU Y, then one need only expand Y and a subsequent lookup in Y
 345      will find X.  Alas TUs live in their own symtab, so after expanding CU Y
 346      we need to look in TU Z to find X.  Fortunately, this is akin to
 347      DW_TAG_imported_unit, so we just use the same mechanism: For
 348      .gdb_index version <=7 this also records the TUs that the CU referred
 349      to.  Concurrently with this change gdb was modified to emit version 8
 350      indices so we only pay a price for gold generated indices.
 351      http://sourceware.org/bugzilla/show_bug.cgi?id=15021.  */
 352   VEC (dwarf2_per_cu_ptr) *imported_symtabs;
 353 };
 354
 355 /* Entry in the signatured_types hash table.  */
 356
 357 struct signatured_type
 358 {
 359   /* The "per_cu" object of this type.
 360      This struct is used iff per_cu.is_debug_types.
 361      N.B.: This is the first member so that it's easy to convert pointers
 362      between them.  */
 363   struct dwarf2_per_cu_data per_cu;
 364
 365   /* The type's signature.  */
 366   ULONGEST signature;
 367
 368   /* Offset in the TU of the type's DIE, as read from the TU header.
 369      If this TU is a DWO stub and the definition lives in a DWO file
 370      (specified by DW_AT_GNU_dwo_name), this value is unusable.  */
 371   cu_offset type_offset_in_tu;
 372
 373   /* Offset in the section of the type's DIE.
 374      If the definition lives in a DWO file, this is the offset in the
 375      .debug_types.dwo section.
 376      The value is zero until the actual value is known.
 377      Zero is otherwise not a valid section offset.  */
 378   sect_offset type_offset_in_section;
 379
 380   /* Type units are grouped by their DW_AT_stmt_list entry so that they
 381      can share them.  This points to the containing symtab.  */
 382   struct type_unit_group *type_unit_group;
 383
 384   /* The type.
 385      The first time we encounter this type we fully read it in and install it
 386      in the symbol tables.  Subsequent times we only need the type.  */
 387   struct type *type;
 388
 389   /* Containing DWO unit.
 390      This field is valid iff per_cu.reading_dwo_directly.  */
 391   struct dwo_unit *dwo_unit;
 392 };
 393
 394 typedef struct signatured_type *sig_type_ptr;
 395 DEF_VEC_P (sig_type_ptr);
 396
 397 #endif /* DWARF2READ_H */