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
  93 /* Collection of data recorded per objfile.
  94    This hangs off of dwarf2_objfile_data_key.  */
  95
  96 struct dwarf2_per_objfile : public allocate_on_obstack
  97 {
  98   /* Construct a dwarf2_per_objfile for OBJFILE.  NAMES points to the
  99      dwarf2 section names, or is NULL if the standard ELF names are
 100      used.  */
 101   dwarf2_per_objfile (struct objfile *objfile,
 102                       const dwarf2_debug_sections *names);
 103
 104   ~dwarf2_per_objfile ();
 105
 106   DISABLE_COPY_AND_ASSIGN (dwarf2_per_objfile);
 107
 108   /* Free all cached compilation units.  */
 109   void free_cached_comp_units ();
 110 private:
 111   /* This function is mapped across the sections and remembers the
 112      offset and size of each of the debugging sections we are
 113      interested in.  */
 114   void locate_sections (bfd *abfd, asection *sectp,
 115                         const dwarf2_debug_sections &names);
 116
 117 public:
 118   dwarf2_section_info info {};
 119   dwarf2_section_info abbrev {};
 120   dwarf2_section_info line {};
 121   dwarf2_section_info loc {};
 122   dwarf2_section_info loclists {};
 123   dwarf2_section_info macinfo {};
 124   dwarf2_section_info macro {};
 125   dwarf2_section_info str {};
 126   dwarf2_section_info line_str {};
 127   dwarf2_section_info ranges {};
 128   dwarf2_section_info rnglists {};
 129   dwarf2_section_info addr {};
 130   dwarf2_section_info frame {};
 131   dwarf2_section_info eh_frame {};
 132   dwarf2_section_info gdb_index {};
 133   dwarf2_section_info debug_names {};
 134   dwarf2_section_info debug_aranges {};
 135
 136   VEC (dwarf2_section_info_def) *types = NULL;
 137
 138   /* Back link.  */
 139   struct objfile *objfile = NULL;
 140
 141   /* Table of all the compilation units.  This is used to locate
 142      the target compilation unit of a particular reference.  */
 143   struct dwarf2_per_cu_data **all_comp_units = NULL;
 144
 145   /* The number of compilation units in ALL_COMP_UNITS.  */
 146   int n_comp_units = 0;
 147
 148   /* The number of .debug_types-related CUs.  */
 149   int n_type_units = 0;
 150
 151   /* The number of elements allocated in all_type_units.
 152      If there are skeleton-less TUs, we add them to all_type_units lazily.  */
 153   int n_allocated_type_units = 0;
 154
 155   /* The .debug_types-related CUs (TUs).
 156      This is stored in malloc space because we may realloc it.  */
 157   struct signatured_type **all_type_units = NULL;
 158
 159   /* Table of struct type_unit_group objects.
 160      The hash key is the DW_AT_stmt_list value.  */
 161   htab_t type_unit_groups {};
 162
 163   /* A table mapping .debug_types signatures to its signatured_type entry.
 164      This is NULL if the .debug_types section hasn't been read in yet.  */
 165   htab_t signatured_types {};
 166
 167   /* Type unit statistics, to see how well the scaling improvements
 168      are doing.  */
 169   struct tu_stats tu_stats {};
 170
 171   /* A chain of compilation units that are currently read in, so that
 172      they can be freed later.  */
 173   dwarf2_per_cu_data *read_in_chain = NULL;
 174
 175   /* A table mapping DW_AT_dwo_name values to struct dwo_file objects.
 176      This is NULL if the table hasn't been allocated yet.  */
 177   htab_t dwo_files {};
 178
 179   /* True if we've checked for whether there is a DWP file.  */
 180   bool dwp_checked = false;
 181
 182   /* The DWP file if there is one, or NULL.  */
 183   struct dwp_file *dwp_file = NULL;
 184
 185   /* The shared '.dwz' file, if one exists.  This is used when the
 186      original data was compressed using 'dwz -m'.  */
 187   struct dwz_file *dwz_file = NULL;
 188
 189   /* A flag indicating whether this objfile has a section loaded at a
 190      VMA of 0.  */
 191   bool has_section_at_zero = false;
 192
 193   /* True if we are using the mapped index,
 194      or we are faking it for OBJF_READNOW's sake.  */
 195   bool using_index = false;
 196
 197   /* The mapped index, or NULL if .gdb_index is missing or not being used.  */
 198   mapped_index *index_table = NULL;
 199
 200   /* The mapped index, or NULL if .debug_names is missing or not being used.  */
 201   std::unique_ptr<mapped_debug_names> debug_names_table;
 202
 203   /* When using index_table, this keeps track of all quick_file_names entries.
 204      TUs typically share line table entries with a CU, so we maintain a
 205      separate table of all line table entries to support the sharing.
 206      Note that while there can be way more TUs than CUs, we've already
 207      sorted all the TUs into "type unit groups", grouped by their
 208      DW_AT_stmt_list value.  Therefore the only sharing done here is with a
 209      CU and its associated TU group if there is one.  */
 210   htab_t quick_file_names_table {};
 211
 212   /* Set during partial symbol reading, to prevent queueing of full
 213      symbols.  */
 214   bool reading_partial_symbols = false;
 215
 216   /* Table mapping type DIEs to their struct type *.
 217      This is NULL if not allocated yet.
 218      The mapping is done via (CU/TU + DIE offset) -> type.  */
 219   htab_t die_type_hash {};
 220
 221   /* The CUs we recently read.  */
 222   VEC (dwarf2_per_cu_ptr) *just_read_cus = NULL;
 223
 224   /* Table containing line_header indexed by offset and offset_in_dwz.  */
 225   htab_t line_header_hash {};
 226
 227   /* Table containing all filenames.  This is an optional because the
 228      table is lazily constructed on first access.  */
 229   gdb::optional<filename_seen_cache> filenames_cache;
 230 };
 231
 232 /* Get the dwarf2_per_objfile associated to OBJFILE.  */
 233
 234 dwarf2_per_objfile *get_dwarf2_per_objfile (struct objfile *objfile);
 235
 236 /* Persistent data held for a compilation unit, even when not
 237    processing it.  We put a pointer to this structure in the
 238    read_symtab_private field of the psymtab.  */
 239
 240 struct dwarf2_per_cu_data
 241 {
 242   /* The start offset and length of this compilation unit.
 243      NOTE: Unlike comp_unit_head.length, this length includes
 244      initial_length_size.
 245      If the DIE refers to a DWO file, this is always of the original die,
 246      not the DWO file.  */
 247   sect_offset sect_off;
 248   unsigned int length;
 249
 250   /* DWARF standard version this data has been read from (such as 4 or 5).  */
 251   short dwarf_version;
 252
 253   /* Flag indicating this compilation unit will be read in before
 254      any of the current compilation units are processed.  */
 255   unsigned int queued : 1;
 256
 257   /* This flag will be set when reading partial DIEs if we need to load
 258      absolutely all DIEs for this compilation unit, instead of just the ones
 259      we think are interesting.  It gets set if we look for a DIE in the
 260      hash table and don't find it.  */
 261   unsigned int load_all_dies : 1;
 262
 263   /* Non-zero if this CU is from .debug_types.
 264      Struct dwarf2_per_cu_data is contained in struct signatured_type iff
 265      this is non-zero.  */
 266   unsigned int is_debug_types : 1;
 267
 268   /* Non-zero if this CU is from the .dwz file.  */
 269   unsigned int is_dwz : 1;
 270
 271   /* Non-zero if reading a TU directly from a DWO file, bypassing the stub.
 272      This flag is only valid if is_debug_types is true.
 273      We can't read a CU directly from a DWO file: There are required
 274      attributes in the stub.  */
 275   unsigned int reading_dwo_directly : 1;
 276
 277   /* Non-zero if the TU has been read.
 278      This is used to assist the "Stay in DWO Optimization" for Fission:
 279      When reading a DWO, it's faster to read TUs from the DWO instead of
 280      fetching them from random other DWOs (due to comdat folding).
 281      If the TU has already been read, the optimization is unnecessary
 282      (and unwise - we don't want to change where gdb thinks the TU lives
 283      "midflight").
 284      This flag is only valid if is_debug_types is true.  */
 285   unsigned int tu_read : 1;
 286
 287   /* The section this CU/TU lives in.
 288      If the DIE refers to a DWO file, this is always the original die,
 289      not the DWO file.  */
 290   struct dwarf2_section_info *section;
 291
 292   /* Set to non-NULL iff this CU is currently loaded.  When it gets freed out
 293      of the CU cache it gets reset to NULL again.  This is left as NULL for
 294      dummy CUs (a CU header, but nothing else).  */
 295   struct dwarf2_cu *cu;
 296
 297   /* The corresponding dwarf2_per_objfile.  */
 298   struct dwarf2_per_objfile *dwarf2_per_objfile;
 299
 300   /* When dwarf2_per_objfile->using_index is true, the 'quick' field
 301      is active.  Otherwise, the 'psymtab' field is active.  */
 302   union
 303   {
 304     /* The partial symbol table associated with this compilation unit,
 305        or NULL for unread partial units.  */
 306     struct partial_symtab *psymtab;
 307
 308     /* Data needed by the "quick" functions.  */
 309     struct dwarf2_per_cu_quick_data *quick;
 310   } v;
 311
 312   /* The CUs we import using DW_TAG_imported_unit.  This is filled in
 313      while reading psymtabs, used to compute the psymtab dependencies,
 314      and then cleared.  Then it is filled in again while reading full
 315      symbols, and only deleted when the objfile is destroyed.
 316
 317      This is also used to work around a difference between the way gold
 318      generates .gdb_index version <=7 and the way gdb does.  Arguably this
 319      is a gold bug.  For symbols coming from TUs, gold records in the index
 320      the CU that includes the TU instead of the TU itself.  This breaks
 321      dw2_lookup_symbol: It assumes that if the index says symbol X lives
 322      in CU/TU Y, then one need only expand Y and a subsequent lookup in Y
 323      will find X.  Alas TUs live in their own symtab, so after expanding CU Y
 324      we need to look in TU Z to find X.  Fortunately, this is akin to
 325      DW_TAG_imported_unit, so we just use the same mechanism: For
 326      .gdb_index version <=7 this also records the TUs that the CU referred
 327      to.  Concurrently with this change gdb was modified to emit version 8
 328      indices so we only pay a price for gold generated indices.
 329      http://sourceware.org/bugzilla/show_bug.cgi?id=15021.  */
 330   VEC (dwarf2_per_cu_ptr) *imported_symtabs;
 331 };
 332
 333 /* Entry in the signatured_types hash table.  */
 334
 335 struct signatured_type
 336 {
 337   /* The "per_cu" object of this type.
 338      This struct is used iff per_cu.is_debug_types.
 339      N.B.: This is the first member so that it's easy to convert pointers
 340      between them.  */
 341   struct dwarf2_per_cu_data per_cu;
 342
 343   /* The type's signature.  */
 344   ULONGEST signature;
 345
 346   /* Offset in the TU of the type's DIE, as read from the TU header.
 347      If this TU is a DWO stub and the definition lives in a DWO file
 348      (specified by DW_AT_GNU_dwo_name), this value is unusable.  */
 349   cu_offset type_offset_in_tu;
 350
 351   /* Offset in the section of the type's DIE.
 352      If the definition lives in a DWO file, this is the offset in the
 353      .debug_types.dwo section.
 354      The value is zero until the actual value is known.
 355      Zero is otherwise not a valid section offset.  */
 356   sect_offset type_offset_in_section;
 357
 358   /* Type units are grouped by their DW_AT_stmt_list entry so that they
 359      can share them.  This points to the containing symtab.  */
 360   struct type_unit_group *type_unit_group;
 361
 362   /* The type.
 363      The first time we encounter this type we fully read it in and install it
 364      in the symbol tables.  Subsequent times we only need the type.  */
 365   struct type *type;
 366
 367   /* Containing DWO unit.
 368      This field is valid iff per_cu.reading_dwo_directly.  */
 369   struct dwo_unit *dwo_unit;
 370 };
 371
 372 typedef struct signatured_type *sig_type_ptr;
 373 DEF_VEC_P (sig_type_ptr);
 374
 375 #endif /* DWARF2READ_H */