include/bfdlink.h

   1 /* bfdlink.h -- header file for BFD link routines
   2    Copyright (C) 1993-2016 Free Software Foundation, Inc.
   3    Written by Steve Chamberlain and Ian Lance Taylor, Cygnus Support.
   4
   5    This file is part of BFD, the Binary File Descriptor library.
   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, write to the Free Software
  19    Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  20    MA 02110-1301, USA.  */
  21
  22 #ifndef BFDLINK_H
  23 #define BFDLINK_H
  24
  25 /* Which symbols to strip during a link.  */
  26 enum bfd_link_strip
  27 {
  28   strip_none,           /* Don't strip any symbols.  */
  29   strip_debugger,       /* Strip debugging symbols.  */
  30   strip_some,           /* keep_hash is the list of symbols to keep.  */
  31   strip_all             /* Strip all symbols.  */
  32 };
  33
  34 /* Which local symbols to discard during a link.  This is irrelevant
  35    if strip_all is used.  */
  36 enum bfd_link_discard
  37 {
  38   discard_sec_merge,    /* Discard local temporary symbols in SEC_MERGE
  39                            sections.  */
  40   discard_none,         /* Don't discard any locals.  */
  41   discard_l,            /* Discard local temporary symbols.  */
  42   discard_all           /* Discard all locals.  */
  43 };
  44
  45 /* Whether to generate ELF common symbols with the STT_COMMON type
  46    during a relocatable link.  */
  47 enum bfd_link_elf_stt_common
  48 {
  49   unchanged,
  50   elf_stt_common,
  51   no_elf_stt_common
  52 };
  53
  54 /* Describes the type of hash table entry structure being used.
  55    Different hash table structure have different fields and so
  56    support different linking features.  */
  57 enum bfd_link_hash_table_type
  58   {
  59     bfd_link_generic_hash_table,
  60     bfd_link_elf_hash_table
  61   };
  62 \f
  63 /* These are the possible types of an entry in the BFD link hash
  64    table.  */
  65
  66 enum bfd_link_hash_type
  67 {
  68   bfd_link_hash_new,            /* Symbol is new.  */
  69   bfd_link_hash_undefined,      /* Symbol seen before, but undefined.  */
  70   bfd_link_hash_undefweak,      /* Symbol is weak and undefined.  */
  71   bfd_link_hash_defined,        /* Symbol is defined.  */
  72   bfd_link_hash_defweak,        /* Symbol is weak and defined.  */
  73   bfd_link_hash_common,         /* Symbol is common.  */
  74   bfd_link_hash_indirect,       /* Symbol is an indirect link.  */
  75   bfd_link_hash_warning         /* Like indirect, but warn if referenced.  */
  76 };
  77
  78 enum bfd_link_common_skip_ar_symbols
  79 {
  80   bfd_link_common_skip_none,
  81   bfd_link_common_skip_text,
  82   bfd_link_common_skip_data,
  83   bfd_link_common_skip_all
  84 };
  85
  86 struct bfd_link_hash_common_entry
  87   {
  88     unsigned int alignment_power;       /* Alignment.  */
  89     asection *section;          /* Symbol section.  */
  90   };
  91
  92 /* The linking routines use a hash table which uses this structure for
  93    its elements.  */
  94
  95 struct bfd_link_hash_entry
  96 {
  97   /* Base hash table entry structure.  */
  98   struct bfd_hash_entry root;
  99
 100   /* Type of this entry.  */
 101   ENUM_BITFIELD (bfd_link_hash_type) type : 8;
 102
 103   /* Symbol is referenced in a normal object file, as distict from a LTO
 104      IR object file.  */
 105   unsigned int non_ir_ref : 1;
 106
 107   /* Symbol is a built-in define.  These will be overridden by PROVIDE
 108      in a linker script.  */
 109   unsigned int linker_def : 1;
 110
 111   /* A union of information depending upon the type.  */
 112   union
 113     {
 114       /* Nothing is kept for bfd_hash_new.  */
 115       /* bfd_link_hash_undefined, bfd_link_hash_undefweak.  */
 116       struct
 117         {
 118           /* Undefined and common symbols are kept in a linked list through
 119              this field.  This field is present in all of the union element
 120              so that we don't need to remove entries from the list when we
 121              change their type.  Removing entries would either require the
 122              list to be doubly linked, which would waste more memory, or
 123              require a traversal.  When an undefined or common symbol is
 124              created, it should be added to this list, the head of which is in
 125              the link hash table itself.  As symbols are defined, they need
 126              not be removed from the list; anything which reads the list must
 127              doublecheck the symbol type.
 128
 129              Weak symbols are not kept on this list.
 130
 131              Defined and defweak symbols use this field as a reference marker.
 132              If the field is not NULL, or this structure is the tail of the
 133              undefined symbol list, the symbol has been referenced.  If the
 134              symbol is undefined and becomes defined, this field will
 135              automatically be non-NULL since the symbol will have been on the
 136              undefined symbol list.  */
 137           struct bfd_link_hash_entry *next;
 138           /* BFD symbol was found in.  */
 139           bfd *abfd;
 140           /* For __start_<name> and __stop_<name> symbols, the first
 141              input section matching the name.  */
 142           asection *section;
 143         } undef;
 144       /* bfd_link_hash_defined, bfd_link_hash_defweak.  */
 145       struct
 146         {
 147           struct bfd_link_hash_entry *next;
 148           /* Symbol section.  */
 149           asection *section;
 150           /* Symbol value.  */
 151           bfd_vma value;
 152         } def;
 153       /* bfd_link_hash_indirect, bfd_link_hash_warning.  */
 154       struct
 155         {
 156           struct bfd_link_hash_entry *next;
 157           /* Real symbol.  */
 158           struct bfd_link_hash_entry *link;
 159           /* Warning message (bfd_link_hash_warning only).  */
 160           const char *warning;
 161         } i;
 162       /* bfd_link_hash_common.  */
 163       struct
 164         {
 165           struct bfd_link_hash_entry *next;
 166           /* The linker needs to know three things about common
 167              symbols: the size, the alignment, and the section in
 168              which the symbol should be placed.  We store the size
 169              here, and we allocate a small structure to hold the
 170              section and the alignment.  The alignment is stored as a
 171              power of two.  We don't store all the information
 172              directly because we don't want to increase the size of
 173              the union; this structure is a major space user in the
 174              linker.  */
 175           struct bfd_link_hash_common_entry *p;
 176           /* Common symbol size.  */
 177           bfd_size_type size;
 178         } c;
 179     } u;
 180 };
 181
 182 /* This is the link hash table.  It is a derived class of
 183    bfd_hash_table.  */
 184
 185 struct bfd_link_hash_table
 186 {
 187   /* The hash table itself.  */
 188   struct bfd_hash_table table;
 189   /* A linked list of undefined and common symbols, linked through the
 190      next field in the bfd_link_hash_entry structure.  */
 191   struct bfd_link_hash_entry *undefs;
 192   /* Entries are added to the tail of the undefs list.  */
 193   struct bfd_link_hash_entry *undefs_tail;
 194   /* Function to free the hash table on closing BFD.  */
 195   void (*hash_table_free) (bfd *);
 196   /* The type of the link hash table.  */
 197   enum bfd_link_hash_table_type type;
 198 };
 199
 200 /* Look up an entry in a link hash table.  If FOLLOW is TRUE, this
 201    follows bfd_link_hash_indirect and bfd_link_hash_warning links to
 202    the real symbol.  */
 203 extern struct bfd_link_hash_entry *bfd_link_hash_lookup
 204   (struct bfd_link_hash_table *, const char *, bfd_boolean create,
 205    bfd_boolean copy, bfd_boolean follow);
 206
 207 /* Look up an entry in the main linker hash table if the symbol might
 208    be wrapped.  This should only be used for references to an
 209    undefined symbol, not for definitions of a symbol.  */
 210
 211 extern struct bfd_link_hash_entry *bfd_wrapped_link_hash_lookup
 212   (bfd *, struct bfd_link_info *, const char *, bfd_boolean,
 213    bfd_boolean, bfd_boolean);
 214
 215 /* If H is a wrapped symbol, ie. the symbol name starts with "__wrap_"
 216    and the remainder is found in wrap_hash, return the real symbol.  */
 217
 218 extern struct bfd_link_hash_entry *unwrap_hash_lookup
 219   (struct bfd_link_info *, bfd *, struct bfd_link_hash_entry *);
 220
 221 /* Traverse a link hash table.  */
 222 extern void bfd_link_hash_traverse
 223   (struct bfd_link_hash_table *,
 224     bfd_boolean (*) (struct bfd_link_hash_entry *, void *),
 225     void *);
 226
 227 /* Add an entry to the undefs list.  */
 228 extern void bfd_link_add_undef
 229   (struct bfd_link_hash_table *, struct bfd_link_hash_entry *);
 230
 231 /* Remove symbols from the undefs list that don't belong there.  */
 232 extern void bfd_link_repair_undef_list
 233   (struct bfd_link_hash_table *table);
 234
 235 /* Read symbols and cache symbol pointer array in outsymbols.  */
 236 extern bfd_boolean bfd_generic_link_read_symbols (bfd *);
 237
 238 /* Check the relocs in the BFD.  Called after all the input
 239    files have been loaded, and garbage collection has tagged
 240    any unneeded sections.  */
 241 extern bfd_boolean bfd_link_check_relocs (bfd *,struct bfd_link_info *);
 242
 243 struct bfd_sym_chain
 244 {
 245   struct bfd_sym_chain *next;
 246   const char *name;
 247 };
 248 \f
 249 /* How to handle unresolved symbols.
 250    There are four possibilities which are enumerated below:  */
 251 enum report_method
 252 {
 253   /* This is the initial value when then link_info structure is created.
 254      It allows the various stages of the linker to determine whether they
 255      allowed to set the value.  */
 256   RM_NOT_YET_SET = 0,
 257   RM_IGNORE,
 258   RM_GENERATE_WARNING,
 259   RM_GENERATE_ERROR
 260 };
 261
 262 typedef enum {with_flags, without_flags} flag_type;
 263
 264 /* A section flag list.  */
 265 struct flag_info_list
 266 {
 267   flag_type with;
 268   const char *name;
 269   bfd_boolean valid;
 270   struct flag_info_list *next;
 271 };
 272
 273 /* Section flag info.  */
 274 struct flag_info
 275 {
 276   flagword only_with_flags;
 277   flagword not_with_flags;
 278   struct flag_info_list *flag_list;
 279   bfd_boolean flags_initialized;
 280 };
 281
 282 struct bfd_elf_dynamic_list;
 283 struct bfd_elf_version_tree;
 284
 285 /* Types of output.  */
 286
 287 enum output_type
 288 {
 289   type_pde,
 290   type_pie,
 291   type_relocatable,
 292   type_dll,
 293 };
 294
 295 #define bfd_link_pde(info)         ((info)->type == type_pde)
 296 #define bfd_link_dll(info)         ((info)->type == type_dll)
 297 #define bfd_link_relocatable(info) ((info)->type == type_relocatable)
 298 #define bfd_link_pie(info)         ((info)->type == type_pie)
 299 #define bfd_link_executable(info)  (bfd_link_pde (info) || bfd_link_pie (info))
 300 #define bfd_link_pic(info)         (bfd_link_dll (info) || bfd_link_pie (info))
 301
 302 /* This structure holds all the information needed to communicate
 303    between BFD and the linker when doing a link.  */
 304
 305 struct bfd_link_info
 306 {
 307   /* Output type.  */
 308   ENUM_BITFIELD (output_type) type : 2;
 309
 310   /* TRUE if BFD should pre-bind symbols in a shared object.  */
 311   unsigned int symbolic: 1;
 312
 313   /* TRUE if executable should not contain copy relocs.
 314      Setting this true may result in a non-sharable text segment.  */
 315   unsigned int nocopyreloc: 1;
 316
 317   /* TRUE if BFD should export all symbols in the dynamic symbol table
 318      of an executable, rather than only those used.  */
 319   unsigned int export_dynamic: 1;
 320
 321   /* TRUE if a default symbol version should be created and used for
 322      exported symbols.  */
 323   unsigned int create_default_symver: 1;
 324
 325   /* TRUE if unreferenced sections should be removed.  */
 326   unsigned int gc_sections: 1;
 327
 328   /* TRUE if every symbol should be reported back via the notice
 329      callback.  */
 330   unsigned int notice_all: 1;
 331
 332   /* TRUE if the LTO plugin is active.  */
 333   unsigned int lto_plugin_active: 1;
 334
 335   /* TRUE if global symbols in discarded sections should be stripped.  */
 336   unsigned int strip_discarded: 1;
 337
 338   /* TRUE if all data symbols should be dynamic.  */
 339   unsigned int dynamic_data: 1;
 340
 341   /* Which symbols to strip.  */
 342   ENUM_BITFIELD (bfd_link_strip) strip : 2;
 343
 344   /* Which local symbols to discard.  */
 345   ENUM_BITFIELD (bfd_link_discard) discard : 2;
 346
 347   /* Whether to generate ELF common symbols with the STT_COMMON type.  */
 348   ENUM_BITFIELD (bfd_link_elf_stt_common) elf_stt_common : 2;
 349
 350   /* Criteria for skipping symbols when determining
 351      whether to include an object from an archive. */
 352   ENUM_BITFIELD (bfd_link_common_skip_ar_symbols) common_skip_ar_symbols : 2;
 353
 354   /* What to do with unresolved symbols in an object file.
 355      When producing executables the default is GENERATE_ERROR.
 356      When producing shared libraries the default is IGNORE.  The
 357      assumption with shared libraries is that the reference will be
 358      resolved at load/execution time.  */
 359   ENUM_BITFIELD (report_method) unresolved_syms_in_objects : 2;
 360
 361   /* What to do with unresolved symbols in a shared library.
 362      The same defaults apply.  */
 363   ENUM_BITFIELD (report_method) unresolved_syms_in_shared_libs : 2;
 364
 365   /* TRUE if shared objects should be linked directly, not shared.  */
 366   unsigned int static_link: 1;
 367
 368   /* TRUE if symbols should be retained in memory, FALSE if they
 369      should be freed and reread.  */
 370   unsigned int keep_memory: 1;
 371
 372   /* TRUE if BFD should generate relocation information in the final
 373      executable.  */
 374   unsigned int emitrelocations: 1;
 375
 376   /* TRUE if PT_GNU_RELRO segment should be created.  */
 377   unsigned int relro: 1;
 378
 379   /* Nonzero if .eh_frame_hdr section and PT_GNU_EH_FRAME ELF segment
 380      should be created.  1 for DWARF2 tables, 2 for compact tables.  */
 381   unsigned int eh_frame_hdr_type: 2;
 382
 383   /* TRUE if we should warn when adding a DT_TEXTREL to a shared object.  */
 384   unsigned int warn_shared_textrel: 1;
 385
 386   /* TRUE if we should error when adding a DT_TEXTREL.  */
 387   unsigned int error_textrel: 1;
 388
 389   /* TRUE if .hash section should be created.  */
 390   unsigned int emit_hash: 1;
 391
 392   /* TRUE if .gnu.hash section should be created.  */
 393   unsigned int emit_gnu_hash: 1;
 394
 395   /* If TRUE reduce memory overheads, at the expense of speed. This will
 396      cause map file generation to use an O(N^2) algorithm and disable
 397      caching ELF symbol buffer.  */
 398   unsigned int reduce_memory_overheads: 1;
 399
 400   /* TRUE if the output file should be in a traditional format.  This
 401      is equivalent to the setting of the BFD_TRADITIONAL_FORMAT flag
 402      on the output file, but may be checked when reading the input
 403      files.  */
 404   unsigned int traditional_format: 1;
 405
 406   /* TRUE if non-PLT relocs should be merged into one reloc section
 407      and sorted so that relocs against the same symbol come together.  */
 408   unsigned int combreloc: 1;
 409
 410   /* TRUE if a default symbol version should be created and used for
 411      imported symbols.  */
 412   unsigned int default_imported_symver: 1;
 413
 414   /* TRUE if the new ELF dynamic tags are enabled. */
 415   unsigned int new_dtags: 1;
 416
 417   /* FALSE if .eh_frame unwind info should be generated for PLT and other
 418      linker created sections, TRUE if it should be omitted.  */
 419   unsigned int no_ld_generated_unwind_info: 1;
 420
 421   /* TRUE if BFD should generate a "task linked" object file,
 422      similar to relocatable but also with globals converted to
 423      statics.  */
 424   unsigned int task_link: 1;
 425
 426   /* TRUE if ok to have multiple definition.  */
 427   unsigned int allow_multiple_definition: 1;
 428
 429   /* TRUE if ok to have version with no definition.  */
 430   unsigned int allow_undefined_version: 1;
 431
 432   /* TRUE if some symbols have to be dynamic, controlled by
 433      --dynamic-list command line options.  */
 434   unsigned int dynamic: 1;
 435
 436   /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W|PF_X
 437      flags.  */
 438   unsigned int execstack: 1;
 439
 440   /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W
 441      flags.  */
 442   unsigned int noexecstack: 1;
 443
 444   /* TRUE if we want to produced optimized output files.  This might
 445      need much more time and therefore must be explicitly selected.  */
 446   unsigned int optimize: 1;
 447
 448   /* TRUE if user should be informed of removed unreferenced sections.  */
 449   unsigned int print_gc_sections: 1;
 450
 451   /* TRUE if we should warn alternate ELF machine code.  */
 452   unsigned int warn_alternate_em: 1;
 453
 454   /* TRUE if the linker script contained an explicit PHDRS command.  */
 455   unsigned int user_phdrs: 1;
 456
 457   /* TRUE if we should check relocations after all input files have
 458      been opened.  */
 459   unsigned int check_relocs_after_open_input: 1;
 460
 461   /* TRUE if BND prefix in PLT entries is always generated.  */
 462   unsigned int bndplt: 1;
 463
 464   /* TRUE if generation of .interp/PT_INTERP should be suppressed.  */
 465   unsigned int nointerp: 1;
 466
 467   /* TRUE if we shouldn't check relocation overflow.  */
 468   unsigned int no_reloc_overflow_check: 1;
 469
 470   /* TRUE if generate a 1-byte NOP as suffix for x86 call instruction.  */
 471   unsigned int call_nop_as_suffix : 1;
 472
 473   /* The 1-byte NOP for x86 call instruction.  */
 474   char call_nop_byte;
 475
 476   /* Char that may appear as the first char of a symbol, but should be
 477      skipped (like symbol_leading_char) when looking up symbols in
 478      wrap_hash.  Used by PowerPC Linux for 'dot' symbols.  */
 479   char wrap_char;
 480
 481   /* Separator between archive and filename in linker script filespecs.  */
 482   char path_separator;
 483
 484   /* Compress DWARF debug sections.  */
 485   enum compressed_debug_section_type compress_debug;
 486
 487   /* Default stack size.  Zero means default (often zero itself), -1
 488      means explicitly zero-sized.  */
 489   bfd_signed_vma stacksize;
 490
 491   /* Enable or disable target specific optimizations.
 492
 493      Not all targets have optimizations to enable.
 494
 495      Normally these optimizations are disabled by default but some targets
 496      prefer to enable them by default.  So this field is a tri-state variable.
 497      The values are:
 498
 499      zero: Enable the optimizations (either from --relax being specified on
 500        the command line or the backend's before_allocation emulation function.
 501
 502      positive: The user has requested that these optimizations be disabled.
 503        (Via the --no-relax command line option).
 504
 505      negative: The optimizations are disabled.  (Set when initializing the
 506        args_type structure in ldmain.c:main.  */
 507   signed int disable_target_specific_optimizations;
 508
 509   /* Function callbacks.  */
 510   const struct bfd_link_callbacks *callbacks;
 511
 512   /* Hash table handled by BFD.  */
 513   struct bfd_link_hash_table *hash;
 514
 515   /* Hash table of symbols to keep.  This is NULL unless strip is
 516      strip_some.  */
 517   struct bfd_hash_table *keep_hash;
 518
 519   /* Hash table of symbols to report back via the notice callback.  If
 520      this is NULL, and notice_all is FALSE, then no symbols are
 521      reported back.  */
 522   struct bfd_hash_table *notice_hash;
 523
 524   /* Hash table of symbols which are being wrapped (the --wrap linker
 525      option).  If this is NULL, no symbols are being wrapped.  */
 526   struct bfd_hash_table *wrap_hash;
 527
 528   /* Hash table of symbols which may be left unresolved during
 529      a link.  If this is NULL, no symbols can be left unresolved.  */
 530   struct bfd_hash_table *ignore_hash;
 531
 532   /* The output BFD.  */
 533   bfd *output_bfd;
 534
 535   /* The list of input BFD's involved in the link.  These are chained
 536      together via the link.next field.  */
 537   bfd *input_bfds;
 538   bfd **input_bfds_tail;
 539
 540   /* If a symbol should be created for each input BFD, this is section
 541      where those symbols should be placed.  It must be a section in
 542      the output BFD.  It may be NULL, in which case no such symbols
 543      will be created.  This is to support CREATE_OBJECT_SYMBOLS in the
 544      linker command language.  */
 545   asection *create_object_symbols_section;
 546
 547   /* List of global symbol names that are starting points for marking
 548      sections against garbage collection.  */
 549   struct bfd_sym_chain *gc_sym_list;
 550
 551   /* If a base output file is wanted, then this points to it */
 552   void *base_file;
 553
 554   /* The function to call when the executable or shared object is
 555      loaded.  */
 556   const char *init_function;
 557
 558   /* The function to call when the executable or shared object is
 559      unloaded.  */
 560   const char *fini_function;
 561
 562   /* Number of relaxation passes.  Usually only one relaxation pass
 563      is needed.  But a backend can have as many relaxation passes as
 564      necessary.  During bfd_relax_section call, it is set to the
 565      current pass, starting from 0.  */
 566   int relax_pass;
 567
 568   /* Number of relaxation trips.  This number is incremented every
 569      time the relaxation pass is restarted due to a previous
 570      relaxation returning true in *AGAIN.  */
 571   int relax_trip;
 572
 573   /* > 0 to treat protected data defined in the shared library as
 574      reference external.  0 to treat it as internal.  -1 to let
 575      backend to decide.  */
 576   int extern_protected_data;
 577
 578   /* > 0 to treat undefined weak symbol in the executable as dynamic,
 579      requiring dynamic relocation.  */
 580   int dynamic_undefined_weak;
 581
 582   /* Non-zero if auto-import thunks for DATA items in pei386 DLLs
 583      should be generated/linked against.  Set to 1 if this feature
 584      is explicitly requested by the user, -1 if enabled by default.  */
 585   int pei386_auto_import;
 586
 587   /* Non-zero if runtime relocs for DATA items with non-zero addends
 588      in pei386 DLLs should be generated.  Set to 1 if this feature
 589      is explicitly requested by the user, -1 if enabled by default.  */
 590   int pei386_runtime_pseudo_reloc;
 591
 592   /* How many spare .dynamic DT_NULL entries should be added?  */
 593   unsigned int spare_dynamic_tags;
 594
 595   /* May be used to set DT_FLAGS for ELF. */
 596   bfd_vma flags;
 597
 598   /* May be used to set DT_FLAGS_1 for ELF. */
 599   bfd_vma flags_1;
 600
 601   /* Start and end of RELRO region.  */
 602   bfd_vma relro_start, relro_end;
 603
 604   /* List of symbols should be dynamic.  */
 605   struct bfd_elf_dynamic_list *dynamic_list;
 606
 607   /* The version information.  */
 608   struct bfd_elf_version_tree *version_info;
 609 };
 610
 611 /* This structures holds a set of callback functions.  These are called
 612    by the BFD linker routines.  */
 613
 614 struct bfd_link_callbacks
 615 {
 616   /* A function which is called when an object is added from an
 617      archive.  ABFD is the archive element being added.  NAME is the
 618      name of the symbol which caused the archive element to be pulled
 619      in.  This function may set *SUBSBFD to point to an alternative
 620      BFD from which symbols should in fact be added in place of the
 621      original BFD's symbols.  Returns TRUE if the object should be
 622      added, FALSE if it should be skipped.  */
 623   bfd_boolean (*add_archive_element)
 624     (struct bfd_link_info *, bfd *abfd, const char *name, bfd **subsbfd);
 625   /* A function which is called when a symbol is found with multiple
 626      definitions.  H is the symbol which is defined multiple times.
 627      NBFD is the new BFD, NSEC is the new section, and NVAL is the new
 628      value.  NSEC may be bfd_com_section or bfd_ind_section.  */
 629   void (*multiple_definition)
 630     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 631      bfd *nbfd, asection *nsec, bfd_vma nval);
 632   /* A function which is called when a common symbol is defined
 633      multiple times.  H is the symbol appearing multiple times.
 634      NBFD is the BFD of the new symbol.  NTYPE is the type of the new
 635      symbol, one of bfd_link_hash_defined, bfd_link_hash_common, or
 636      bfd_link_hash_indirect.  If NTYPE is bfd_link_hash_common, NSIZE
 637      is the size of the new symbol.  */
 638   void (*multiple_common)
 639     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 640      bfd *nbfd, enum bfd_link_hash_type ntype, bfd_vma nsize);
 641   /* A function which is called to add a symbol to a set.  ENTRY is
 642      the link hash table entry for the set itself (e.g.,
 643      __CTOR_LIST__).  RELOC is the relocation to use for an entry in
 644      the set when generating a relocatable file, and is also used to
 645      get the size of the entry when generating an executable file.
 646      ABFD, SEC and VALUE identify the value to add to the set.  */
 647   void (*add_to_set)
 648     (struct bfd_link_info *, struct bfd_link_hash_entry *entry,
 649      bfd_reloc_code_real_type reloc, bfd *abfd, asection *sec, bfd_vma value);
 650   /* A function which is called when the name of a g++ constructor or
 651      destructor is found.  This is only called by some object file
 652      formats.  CONSTRUCTOR is TRUE for a constructor, FALSE for a
 653      destructor.  This will use BFD_RELOC_CTOR when generating a
 654      relocatable file.  NAME is the name of the symbol found.  ABFD,
 655      SECTION and VALUE are the value of the symbol.  */
 656   void (*constructor)
 657     (struct bfd_link_info *, bfd_boolean constructor, const char *name,
 658      bfd *abfd, asection *sec, bfd_vma value);
 659   /* A function which is called to issue a linker warning.  For
 660      example, this is called when there is a reference to a warning
 661      symbol.  WARNING is the warning to be issued.  SYMBOL is the name
 662      of the symbol which triggered the warning; it may be NULL if
 663      there is none.  ABFD, SECTION and ADDRESS identify the location
 664      which trigerred the warning; either ABFD or SECTION or both may
 665      be NULL if the location is not known.  */
 666   void (*warning)
 667     (struct bfd_link_info *, const char *warning, const char *symbol,
 668      bfd *abfd, asection *section, bfd_vma address);
 669   /* A function which is called when a relocation is attempted against
 670      an undefined symbol.  NAME is the symbol which is undefined.
 671      ABFD, SECTION and ADDRESS identify the location from which the
 672      reference is made. IS_FATAL indicates whether an undefined symbol is
 673      a fatal error or not. In some cases SECTION may be NULL.  */
 674   void (*undefined_symbol)
 675     (struct bfd_link_info *, const char *name, bfd *abfd,
 676      asection *section, bfd_vma address, bfd_boolean is_fatal);
 677   /* A function which is called when a reloc overflow occurs. ENTRY is
 678      the link hash table entry for the symbol the reloc is against.
 679      NAME is the name of the local symbol or section the reloc is
 680      against, RELOC_NAME is the name of the relocation, and ADDEND is
 681      any addend that is used.  ABFD, SECTION and ADDRESS identify the
 682      location at which the overflow occurs; if this is the result of a
 683      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 684      ABFD will be NULL.  */
 685   void (*reloc_overflow)
 686     (struct bfd_link_info *, struct bfd_link_hash_entry *entry,
 687      const char *name, const char *reloc_name, bfd_vma addend,
 688      bfd *abfd, asection *section, bfd_vma address);
 689   /* A function which is called when a dangerous reloc is performed.
 690      MESSAGE is an appropriate message.
 691      ABFD, SECTION and ADDRESS identify the location at which the
 692      problem occurred; if this is the result of a
 693      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 694      ABFD will be NULL.  */
 695   void (*reloc_dangerous)
 696     (struct bfd_link_info *, const char *message,
 697      bfd *abfd, asection *section, bfd_vma address);
 698   /* A function which is called when a reloc is found to be attached
 699      to a symbol which is not being written out.  NAME is the name of
 700      the symbol.  ABFD, SECTION and ADDRESS identify the location of
 701      the reloc; if this is the result of a
 702      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 703      ABFD will be NULL.  */
 704   void (*unattached_reloc)
 705     (struct bfd_link_info *, const char *name,
 706      bfd *abfd, asection *section, bfd_vma address);
 707   /* A function which is called when a symbol in notice_hash is
 708      defined or referenced.  H is the symbol, INH the indirect symbol
 709      if applicable.  ABFD, SECTION and ADDRESS are the (new) value of
 710      the symbol.  If SECTION is bfd_und_section, this is a reference.
 711      FLAGS are the symbol BSF_* flags.  */
 712   bfd_boolean (*notice)
 713     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 714      struct bfd_link_hash_entry *inh,
 715      bfd *abfd, asection *section, bfd_vma address, flagword flags);
 716   /* Error or warning link info message.  */
 717   void (*einfo)
 718     (const char *fmt, ...);
 719   /* General link info message.  */
 720   void (*info)
 721     (const char *fmt, ...);
 722   /* Message to be printed in linker map file.  */
 723   void (*minfo)
 724     (const char *fmt, ...);
 725   /* This callback provides a chance for users of the BFD library to
 726      override its decision about whether to place two adjacent sections
 727      into the same segment.  */
 728   bfd_boolean (*override_segment_assignment)
 729     (struct bfd_link_info *, bfd * abfd,
 730      asection * current_section, asection * previous_section,
 731      bfd_boolean new_segment);
 732 };
 733 \f
 734 /* The linker builds link_order structures which tell the code how to
 735    include input data in the output file.  */
 736
 737 /* These are the types of link_order structures.  */
 738
 739 enum bfd_link_order_type
 740 {
 741   bfd_undefined_link_order,     /* Undefined.  */
 742   bfd_indirect_link_order,      /* Built from a section.  */
 743   bfd_data_link_order,          /* Set to explicit data.  */
 744   bfd_section_reloc_link_order, /* Relocate against a section.  */
 745   bfd_symbol_reloc_link_order   /* Relocate against a symbol.  */
 746 };
 747
 748 /* This is the link_order structure itself.  These form a chain
 749    attached to the output section whose contents they are describing.  */
 750
 751 struct bfd_link_order
 752 {
 753   /* Next link_order in chain.  */
 754   struct bfd_link_order *next;
 755   /* Type of link_order.  */
 756   enum bfd_link_order_type type;
 757   /* Offset within output section.  */
 758   bfd_vma offset;
 759   /* Size within output section.  */
 760   bfd_size_type size;
 761   /* Type specific information.  */
 762   union
 763     {
 764       struct
 765         {
 766           /* Section to include.  If this is used, then
 767              section->output_section must be the section the
 768              link_order is attached to, section->output_offset must
 769              equal the link_order offset field, and section->size
 770              must equal the link_order size field.  Maybe these
 771              restrictions should be relaxed someday.  */
 772           asection *section;
 773         } indirect;
 774       struct
 775         {
 776           /* Size of contents, or zero when contents should be filled by
 777              the architecture-dependent fill function.
 778              A non-zero value allows filling of the output section
 779              with an arbitrary repeated pattern.  */
 780           unsigned int size;
 781           /* Data to put into file.  */
 782           bfd_byte *contents;
 783         } data;
 784       struct
 785         {
 786           /* Description of reloc to generate.  Used for
 787              bfd_section_reloc_link_order and
 788              bfd_symbol_reloc_link_order.  */
 789           struct bfd_link_order_reloc *p;
 790         } reloc;
 791     } u;
 792 };
 793
 794 /* A linker order of type bfd_section_reloc_link_order or
 795    bfd_symbol_reloc_link_order means to create a reloc against a
 796    section or symbol, respectively.  This is used to implement -Ur to
 797    generate relocs for the constructor tables.  The
 798    bfd_link_order_reloc structure describes the reloc that BFD should
 799    create.  It is similar to a arelent, but I didn't use arelent
 800    because the linker does not know anything about most symbols, and
 801    any asymbol structure it creates will be partially meaningless.
 802    This information could logically be in the bfd_link_order struct,
 803    but I didn't want to waste the space since these types of relocs
 804    are relatively rare.  */
 805
 806 struct bfd_link_order_reloc
 807 {
 808   /* Reloc type.  */
 809   bfd_reloc_code_real_type reloc;
 810
 811   union
 812     {
 813       /* For type bfd_section_reloc_link_order, this is the section
 814          the reloc should be against.  This must be a section in the
 815          output BFD, not any of the input BFDs.  */
 816       asection *section;
 817       /* For type bfd_symbol_reloc_link_order, this is the name of the
 818          symbol the reloc should be against.  */
 819       const char *name;
 820     } u;
 821
 822   /* Addend to use.  The object file should contain zero.  The BFD
 823      backend is responsible for filling in the contents of the object
 824      file correctly.  For some object file formats (e.g., COFF) the
 825      addend must be stored into in the object file, and for some
 826      (e.g., SPARC a.out) it is kept in the reloc.  */
 827   bfd_vma addend;
 828 };
 829
 830 /* Allocate a new link_order for a section.  */
 831 extern struct bfd_link_order *bfd_new_link_order (bfd *, asection *);
 832
 833 /* These structures are used to describe version information for the
 834    ELF linker.  These structures could be manipulated entirely inside
 835    BFD, but it would be a pain.  Instead, the regular linker sets up
 836    these structures, and then passes them into BFD.  */
 837
 838 /* Glob pattern for a version.  */
 839
 840 struct bfd_elf_version_expr
 841 {
 842   /* Next glob pattern for this version.  */
 843   struct bfd_elf_version_expr *next;
 844   /* Glob pattern.  */
 845   const char *pattern;
 846   /* Set if pattern is not a glob.  */
 847   unsigned int literal : 1;
 848   /* Defined by ".symver".  */
 849   unsigned int symver : 1;
 850   /* Defined by version script.  */
 851   unsigned int script : 1;
 852   /* Pattern type.  */
 853 #define BFD_ELF_VERSION_C_TYPE          1
 854 #define BFD_ELF_VERSION_CXX_TYPE        2
 855 #define BFD_ELF_VERSION_JAVA_TYPE       4
 856   unsigned int mask : 3;
 857 };
 858
 859 struct bfd_elf_version_expr_head
 860 {
 861   /* List of all patterns, both wildcards and non-wildcards.  */
 862   struct bfd_elf_version_expr *list;
 863   /* Hash table for non-wildcards.  */
 864   void *htab;
 865   /* Remaining patterns.  */
 866   struct bfd_elf_version_expr *remaining;
 867   /* What kind of pattern types are present in list (bitmask).  */
 868   unsigned int mask;
 869 };
 870
 871 /* Version dependencies.  */
 872
 873 struct bfd_elf_version_deps
 874 {
 875   /* Next dependency for this version.  */
 876   struct bfd_elf_version_deps *next;
 877   /* The version which this version depends upon.  */
 878   struct bfd_elf_version_tree *version_needed;
 879 };
 880
 881 /* A node in the version tree.  */
 882
 883 struct bfd_elf_version_tree
 884 {
 885   /* Next version.  */
 886   struct bfd_elf_version_tree *next;
 887   /* Name of this version.  */
 888   const char *name;
 889   /* Version number.  */
 890   unsigned int vernum;
 891   /* Regular expressions for global symbols in this version.  */
 892   struct bfd_elf_version_expr_head globals;
 893   /* Regular expressions for local symbols in this version.  */
 894   struct bfd_elf_version_expr_head locals;
 895   /* List of versions which this version depends upon.  */
 896   struct bfd_elf_version_deps *deps;
 897   /* Index of the version name.  This is used within BFD.  */
 898   unsigned int name_indx;
 899   /* Whether this version tree was used.  This is used within BFD.  */
 900   int used;
 901   /* Matching hook.  */
 902   struct bfd_elf_version_expr *(*match)
 903     (struct bfd_elf_version_expr_head *head,
 904      struct bfd_elf_version_expr *prev, const char *sym);
 905 };
 906
 907 struct bfd_elf_dynamic_list
 908 {
 909   struct bfd_elf_version_expr_head head;
 910   struct bfd_elf_version_expr *(*match)
 911     (struct bfd_elf_version_expr_head *head,
 912      struct bfd_elf_version_expr *prev, const char *sym);
 913 };
 914
 915 #endif