include/bfdlink.h

   1 /* bfdlink.h -- header file for BFD link routines
   2    Copyright 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000
   3    Free Software Foundation, Inc.
   4    Written by Steve Chamberlain and Ian Lance Taylor, Cygnus Support.
   5
   6 This file is part of BFD, the Binary File Descriptor library.
   7
   8 This program is free software; you can redistribute it and/or modify
   9 it under the terms of the GNU General Public License as published by
  10 the Free Software Foundation; either version 2 of the License, or
  11 (at your option) any later version.
  12
  13 This program is distributed in the hope that it will be useful,
  14 but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 GNU General Public License for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with this program; if not, write to the Free Software
  20 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, 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 \f
  45 /* These are the possible types of an entry in the BFD link hash
  46    table.  */
  47
  48 enum bfd_link_hash_type
  49 {
  50   bfd_link_hash_new,            /* Symbol is new.  */
  51   bfd_link_hash_undefined,      /* Symbol seen before, but undefined.  */
  52   bfd_link_hash_undefweak,      /* Symbol is weak and undefined.  */
  53   bfd_link_hash_defined,        /* Symbol is defined.  */
  54   bfd_link_hash_defweak,        /* Symbol is weak and defined.  */
  55   bfd_link_hash_common,         /* Symbol is common.  */
  56   bfd_link_hash_indirect,       /* Symbol is an indirect link.  */
  57   bfd_link_hash_warning         /* Like indirect, but warn if referenced.  */
  58 };
  59
  60 /* The linking routines use a hash table which uses this structure for
  61    its elements.  */
  62
  63 struct bfd_link_hash_entry
  64 {
  65   /* Base hash table entry structure.  */
  66   struct bfd_hash_entry root;
  67   /* Type of this entry.  */
  68   enum bfd_link_hash_type type;
  69
  70   /* Undefined and common symbols are kept in a linked list through
  71      this field.  This field is not in the union because that would
  72      force us to remove entries from the list when we changed their
  73      type, which would force the list to be doubly linked, which would
  74      waste more memory.  When an undefined or common symbol is
  75      created, it should be added to this list, the head of which is in
  76      the link hash table itself.  As symbols are defined, they need
  77      not be removed from the list; anything which reads the list must
  78      doublecheck the symbol type.
  79
  80      Weak symbols are not kept on this list.
  81
  82      Defined and defweak symbols use this field as a reference marker.
  83      If the field is not NULL, or this structure is the tail of the
  84      undefined symbol list, the symbol has been referenced.  If the
  85      symbol is undefined and becomes defined, this field will
  86      automatically be non-NULL since the symbol will have been on the
  87      undefined symbol list.  */
  88   struct bfd_link_hash_entry *next;
  89   /* A union of information depending upon the type.  */
  90   union
  91     {
  92       /* Nothing is kept for bfd_hash_new.  */
  93       /* bfd_link_hash_undefined, bfd_link_hash_undefweak.  */
  94       struct
  95         {
  96           bfd *abfd;            /* BFD symbol was found in.  */
  97         } undef;
  98       /* bfd_link_hash_defined, bfd_link_hash_defweak.  */
  99       struct
 100         {
 101           bfd_vma value;        /* Symbol value.  */
 102           asection *section;    /* Symbol section.  */
 103         } def;
 104       /* bfd_link_hash_indirect, bfd_link_hash_warning.  */
 105       struct
 106         {
 107           struct bfd_link_hash_entry *link;     /* Real symbol.  */
 108           const char *warning;  /* Warning (bfd_link_hash_warning only).  */
 109         } i;
 110       /* bfd_link_hash_common.  */
 111       struct
 112         {
 113           /* The linker needs to know three things about common
 114              symbols: the size, the alignment, and the section in
 115              which the symbol should be placed.  We store the size
 116              here, and we allocate a small structure to hold the
 117              section and the alignment.  The alignment is stored as a
 118              power of two.  We don't store all the information
 119              directly because we don't want to increase the size of
 120              the union; this structure is a major space user in the
 121              linker.  */
 122           bfd_size_type size;   /* Common symbol size.  */
 123           struct bfd_link_hash_common_entry
 124             {
 125               unsigned int alignment_power;     /* Alignment.  */
 126               asection *section;                /* Symbol section.  */
 127             } *p;
 128         } c;
 129     } u;
 130 };
 131
 132 /* This is the link hash table.  It is a derived class of
 133    bfd_hash_table.  */
 134
 135 struct bfd_link_hash_table
 136 {
 137   /* The hash table itself.  */
 138   struct bfd_hash_table table;
 139   /* The back end which created this hash table.  This indicates the
 140      type of the entries in the hash table, which is sometimes
 141      important information when linking object files of different
 142      types together.  */
 143   const bfd_target *creator;
 144   /* A linked list of undefined and common symbols, linked through the
 145      next field in the bfd_link_hash_entry structure.  */
 146   struct bfd_link_hash_entry *undefs;
 147   /* Entries are added to the tail of the undefs list.  */
 148   struct bfd_link_hash_entry *undefs_tail;
 149 };
 150
 151 /* Look up an entry in a link hash table.  If FOLLOW is true, this
 152    follows bfd_link_hash_indirect and bfd_link_hash_warning links to
 153    the real symbol.  */
 154 extern struct bfd_link_hash_entry *bfd_link_hash_lookup
 155   PARAMS ((struct bfd_link_hash_table *, const char *, boolean create,
 156            boolean copy, boolean follow));
 157
 158 /* Look up an entry in the main linker hash table if the symbol might
 159    be wrapped.  This should only be used for references to an
 160    undefined symbol, not for definitions of a symbol.  */
 161
 162 extern struct bfd_link_hash_entry *bfd_wrapped_link_hash_lookup
 163   PARAMS ((bfd *, struct bfd_link_info *, const char *, boolean, boolean,
 164            boolean));
 165
 166 /* Traverse a link hash table.  */
 167 extern void bfd_link_hash_traverse
 168   PARAMS ((struct bfd_link_hash_table *,
 169            boolean (*) (struct bfd_link_hash_entry *, PTR),
 170            PTR));
 171
 172 /* Add an entry to the undefs list.  */
 173 extern void bfd_link_add_undef
 174   PARAMS ((struct bfd_link_hash_table *, struct bfd_link_hash_entry *));
 175 \f
 176 /* This structure holds all the information needed to communicate
 177    between BFD and the linker when doing a link.  */
 178
 179 struct bfd_link_info
 180 {
 181   /* Function callbacks.  */
 182   const struct bfd_link_callbacks *callbacks;
 183   /* true if BFD should generate a relocateable object file.  */
 184   boolean relocateable;
 185   /* true if BFD should generate relocation information in the final executable.  */
 186   boolean emitrelocations;
 187   /* true if BFD should generate a "task linked" object file,
 188      similar to relocatable but also with globals converted to statics. */
 189   boolean task_link;
 190   /* true if BFD should generate a shared object.  */
 191   boolean shared;
 192   /* true if BFD should pre-bind symbols in a shared object.  */
 193   boolean symbolic;
 194   /* true if shared objects should be linked directly, not shared.  */
 195   boolean static_link;
 196   /* true if the output file should be in a traditional format.  This
 197      is equivalent to the setting of the BFD_TRADITIONAL_FORMAT flag
 198      on the output file, but may be checked when reading the input
 199      files.  */
 200   boolean traditional_format;
 201   /* true if we want to produced optimized output files.  This might
 202      need much more time and therefore must be explicitly selected.  */
 203   boolean optimize;
 204   /* true if BFD should generate errors for undefined symbols
 205      even if generating a shared object.  */
 206   boolean no_undefined;
 207   /* true if BFD should allow undefined symbols in shared objects even
 208      when no_undefined is set to disallow undefined symbols.  The net
 209      result will be that undefined symbols in regular objects will
 210      still trigger an error, but undefined symbols in shared objects
 211      will be ignored.  The implementation of no_undefined makes the
 212      assumption that the runtime linker will choke on undefined
 213      symbols.  However there is at least one system (BeOS) where
 214      undefined symbols in shared libraries is normal since the kernel
 215      patches them at load time to select which function is most
 216      appropriate for the current architecture.  I.E. dynamically
 217      select an appropriate memset function.  Apparently it is also
 218      normal for HPPA shared libraries to have undefined symbols.  */
 219   boolean allow_shlib_undefined;
 220   /* Which symbols to strip.  */
 221   enum bfd_link_strip strip;
 222   /* Which local symbols to discard.  */
 223   enum bfd_link_discard discard;
 224   /* true if symbols should be retained in memory, false if they
 225      should be freed and reread.  */
 226   boolean keep_memory;
 227   /* The list of input BFD's involved in the link.  These are chained
 228      together via the link_next field.  */
 229   bfd *input_bfds;
 230   /* If a symbol should be created for each input BFD, this is section
 231      where those symbols should be placed.  It must be a section in
 232      the output BFD.  It may be NULL, in which case no such symbols
 233      will be created.  This is to support CREATE_OBJECT_SYMBOLS in the
 234      linker command language.  */
 235   asection *create_object_symbols_section;
 236   /* Hash table handled by BFD.  */
 237   struct bfd_link_hash_table *hash;
 238   /* Hash table of symbols to keep.  This is NULL unless strip is
 239      strip_some.  */
 240   struct bfd_hash_table *keep_hash;
 241   /* true if every symbol should be reported back via the notice
 242      callback.  */
 243   boolean notice_all;
 244   /* Hash table of symbols to report back via the notice callback.  If
 245      this is NULL, and notice_all is false, then no symbols are
 246      reported back.  */
 247   struct bfd_hash_table *notice_hash;
 248   /* Hash table of symbols which are being wrapped (the --wrap linker
 249      option).  If this is NULL, no symbols are being wrapped.  */
 250   struct bfd_hash_table *wrap_hash;
 251   /* If a base output file is wanted, then this points to it */
 252   PTR base_file;
 253
 254   /* If non-zero, specifies that branches which are problematic for the
 255   MPC860 C0 (or earlier) should be checked for and modified.  It gives the
 256   number of bytes that should be checked at the end of each text page. */
 257   int mpc860c0;
 258
 259   /* The function to call when the executable or shared object is
 260      loaded.  */
 261   const char *init_function;
 262   /* The function to call when the executable or shared object is
 263      unloaded.  */
 264   const char *fini_function;
 265
 266   /* true if the new ELF dynamic tags are enabled. */
 267   boolean new_dtags;
 268
 269   /* May be used to set DT_FLAGS for ELF. */
 270   bfd_vma flags;
 271
 272   /* May be used to set DT_FLAGS_1 for ELF. */
 273   bfd_vma flags_1;
 274 };
 275
 276 /* This structures holds a set of callback functions.  These are
 277    called by the BFD linker routines.  The first argument to each
 278    callback function is the bfd_link_info structure being used.  Each
 279    function returns a boolean value.  If the function returns false,
 280    then the BFD function which called it will return with a failure
 281    indication.  */
 282
 283 struct bfd_link_callbacks
 284 {
 285   /* A function which is called when an object is added from an
 286      archive.  ABFD is the archive element being added.  NAME is the
 287      name of the symbol which caused the archive element to be pulled
 288      in.  */
 289   boolean (*add_archive_element) PARAMS ((struct bfd_link_info *,
 290                                           bfd *abfd,
 291                                           const char *name));
 292   /* A function which is called when a symbol is found with multiple
 293      definitions.  NAME is the symbol which is defined multiple times.
 294      OBFD is the old BFD, OSEC is the old section, OVAL is the old
 295      value, NBFD is the new BFD, NSEC is the new section, and NVAL is
 296      the new value.  OBFD may be NULL.  OSEC and NSEC may be
 297      bfd_com_section or bfd_ind_section.  */
 298   boolean (*multiple_definition) PARAMS ((struct bfd_link_info *,
 299                                           const char *name,
 300                                           bfd *obfd,
 301                                           asection *osec,
 302                                           bfd_vma oval,
 303                                           bfd *nbfd,
 304                                           asection *nsec,
 305                                           bfd_vma nval));
 306   /* A function which is called when a common symbol is defined
 307      multiple times.  NAME is the symbol appearing multiple times.
 308      OBFD is the BFD of the existing symbol; it may be NULL if this is
 309      not known.  OTYPE is the type of the existing symbol, which may
 310      be bfd_link_hash_defined, bfd_link_hash_defweak,
 311      bfd_link_hash_common, or bfd_link_hash_indirect.  If OTYPE is
 312      bfd_link_hash_common, OSIZE is the size of the existing symbol.
 313      NBFD is the BFD of the new symbol.  NTYPE is the type of the new
 314      symbol, one of bfd_link_hash_defined, bfd_link_hash_common, or
 315      bfd_link_hash_indirect.  If NTYPE is bfd_link_hash_common, NSIZE
 316      is the size of the new symbol.  */
 317   boolean (*multiple_common) PARAMS ((struct bfd_link_info *,
 318                                       const char *name,
 319                                       bfd *obfd,
 320                                       enum bfd_link_hash_type otype,
 321                                       bfd_vma osize,
 322                                       bfd *nbfd,
 323                                       enum bfd_link_hash_type ntype,
 324                                       bfd_vma nsize));
 325   /* A function which is called to add a symbol to a set.  ENTRY is
 326      the link hash table entry for the set itself (e.g.,
 327      __CTOR_LIST__).  RELOC is the relocation to use for an entry in
 328      the set when generating a relocateable file, and is also used to
 329      get the size of the entry when generating an executable file.
 330      ABFD, SEC and VALUE identify the value to add to the set.  */
 331   boolean (*add_to_set) PARAMS ((struct bfd_link_info *,
 332                                  struct bfd_link_hash_entry *entry,
 333                                  bfd_reloc_code_real_type reloc,
 334                                  bfd *abfd, asection *sec, bfd_vma value));
 335   /* A function which is called when the name of a g++ constructor or
 336      destructor is found.  This is only called by some object file
 337      formats.  CONSTRUCTOR is true for a constructor, false for a
 338      destructor.  This will use BFD_RELOC_CTOR when generating a
 339      relocateable file.  NAME is the name of the symbol found.  ABFD,
 340      SECTION and VALUE are the value of the symbol.  */
 341   boolean (*constructor) PARAMS ((struct bfd_link_info *,
 342                                   boolean constructor,
 343                                   const char *name, bfd *abfd, asection *sec,
 344                                   bfd_vma value));
 345   /* A function which is called to issue a linker warning.  For
 346      example, this is called when there is a reference to a warning
 347      symbol.  WARNING is the warning to be issued.  SYMBOL is the name
 348      of the symbol which triggered the warning; it may be NULL if
 349      there is none.  ABFD, SECTION and ADDRESS identify the location
 350      which trigerred the warning; either ABFD or SECTION or both may
 351      be NULL if the location is not known.  */
 352   boolean (*warning) PARAMS ((struct bfd_link_info *,
 353                               const char *warning, const char *symbol,
 354                               bfd *abfd, asection *section,
 355                               bfd_vma address));
 356   /* A function which is called when a relocation is attempted against
 357      an undefined symbol.  NAME is the symbol which is undefined.
 358      ABFD, SECTION and ADDRESS identify the location from which the
 359      reference is made. FATAL indicates whether an undefined symbol is
 360      a fatal error or not. In some cases SECTION may be NULL.  */
 361   boolean (*undefined_symbol) PARAMS ((struct bfd_link_info *,
 362                                        const char *name, bfd *abfd,
 363                                        asection *section,
 364                                        bfd_vma address,
 365                                        boolean fatal));
 366   /* A function which is called when a reloc overflow occurs.  NAME is
 367      the name of the symbol or section the reloc is against,
 368      RELOC_NAME is the name of the relocation, and ADDEND is any
 369      addend that is used.  ABFD, SECTION and ADDRESS identify the
 370      location at which the overflow occurs; if this is the result of a
 371      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 372      ABFD will be NULL.  */
 373   boolean (*reloc_overflow) PARAMS ((struct bfd_link_info *,
 374                                      const char *name,
 375                                      const char *reloc_name, bfd_vma addend,
 376                                      bfd *abfd, asection *section,
 377                                      bfd_vma address));
 378   /* A function which is called when a dangerous reloc is performed.
 379      The canonical example is an a29k IHCONST reloc which does not
 380      follow an IHIHALF reloc.  MESSAGE is an appropriate message.
 381      ABFD, SECTION and ADDRESS identify the location at which the
 382      problem occurred; if this is the result of a
 383      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 384      ABFD will be NULL.  */
 385   boolean (*reloc_dangerous) PARAMS ((struct bfd_link_info *,
 386                                       const char *message,
 387                                       bfd *abfd, asection *section,
 388                                       bfd_vma address));
 389   /* A function which is called when a reloc is found to be attached
 390      to a symbol which is not being written out.  NAME is the name of
 391      the symbol.  ABFD, SECTION and ADDRESS identify the location of
 392      the reloc; if this is the result of a
 393      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 394      ABFD will be NULL.  */
 395   boolean (*unattached_reloc) PARAMS ((struct bfd_link_info *,
 396                                        const char *name,
 397                                        bfd *abfd, asection *section,
 398                                        bfd_vma address));
 399   /* A function which is called when a symbol in notice_hash is
 400      defined or referenced.  NAME is the symbol.  ABFD, SECTION and
 401      ADDRESS are the value of the symbol.  If SECTION is
 402      bfd_und_section, this is a reference.  */
 403   boolean (*notice) PARAMS ((struct bfd_link_info *, const char *name,
 404                              bfd *abfd, asection *section, bfd_vma address));
 405 };
 406 \f
 407 /* The linker builds link_order structures which tell the code how to
 408    include input data in the output file.  */
 409
 410 /* These are the types of link_order structures.  */
 411
 412 enum bfd_link_order_type
 413 {
 414   bfd_undefined_link_order,     /* Undefined.  */
 415   bfd_indirect_link_order,      /* Built from a section.  */
 416   bfd_fill_link_order,          /* Fill with a 16 bit constant.  */
 417   bfd_data_link_order,          /* Set to explicit data.  */
 418   bfd_section_reloc_link_order, /* Relocate against a section.  */
 419   bfd_symbol_reloc_link_order   /* Relocate against a symbol.  */
 420 };
 421
 422 /* This is the link_order structure itself.  These form a chain
 423    attached to the section whose contents they are describing.  */
 424
 425 struct bfd_link_order
 426 {
 427   /* Next link_order in chain.  */
 428   struct bfd_link_order *next;
 429   /* Type of link_order.  */
 430   enum bfd_link_order_type type;
 431   /* Offset within output section.  */
 432   bfd_vma offset;
 433   /* Size within output section.  */
 434   bfd_size_type size;
 435   /* Type specific information.  */
 436   union
 437     {
 438       struct
 439         {
 440           /* Section to include.  If this is used, then
 441              section->output_section must be the section the
 442              link_order is attached to, section->output_offset must
 443              equal the link_order offset field, and section->_raw_size
 444              must equal the link_order size field.  Maybe these
 445              restrictions should be relaxed someday.  */
 446           asection *section;
 447         } indirect;
 448       struct
 449         {
 450           /* Value to fill with.  */
 451           unsigned int value;
 452         } fill;
 453       struct
 454         {
 455           /* Data to put into file.  The size field gives the number
 456              of bytes which this field points to.  */
 457           bfd_byte *contents;
 458         } data;
 459       struct
 460         {
 461           /* Description of reloc to generate.  Used for
 462              bfd_section_reloc_link_order and
 463              bfd_symbol_reloc_link_order.  */
 464           struct bfd_link_order_reloc *p;
 465         } reloc;
 466     } u;
 467 };
 468
 469 /* A linker order of type bfd_section_reloc_link_order or
 470    bfd_symbol_reloc_link_order means to create a reloc against a
 471    section or symbol, respectively.  This is used to implement -Ur to
 472    generate relocs for the constructor tables.  The
 473    bfd_link_order_reloc structure describes the reloc that BFD should
 474    create.  It is similar to a arelent, but I didn't use arelent
 475    because the linker does not know anything about most symbols, and
 476    any asymbol structure it creates will be partially meaningless.
 477    This information could logically be in the bfd_link_order struct,
 478    but I didn't want to waste the space since these types of relocs
 479    are relatively rare.  */
 480
 481 struct bfd_link_order_reloc
 482 {
 483   /* Reloc type.  */
 484   bfd_reloc_code_real_type reloc;
 485
 486   union
 487     {
 488       /* For type bfd_section_reloc_link_order, this is the section
 489          the reloc should be against.  This must be a section in the
 490          output BFD, not any of the input BFDs.  */
 491       asection *section;
 492       /* For type bfd_symbol_reloc_link_order, this is the name of the
 493          symbol the reloc should be against.  */
 494       const char *name;
 495     } u;
 496
 497   /* Addend to use.  The object file should contain zero.  The BFD
 498      backend is responsible for filling in the contents of the object
 499      file correctly.  For some object file formats (e.g., COFF) the
 500      addend must be stored into in the object file, and for some
 501      (e.g., SPARC a.out) it is kept in the reloc.  */
 502   bfd_vma addend;
 503 };
 504
 505 /* Allocate a new link_order for a section.  */
 506 extern struct bfd_link_order *bfd_new_link_order PARAMS ((bfd *, asection *));
 507
 508 /* These structures are used to describe version information for the
 509    ELF linker.  These structures could be manipulated entirely inside
 510    BFD, but it would be a pain.  Instead, the regular linker sets up
 511    these structures, and then passes them into BFD.  */
 512
 513 /* Regular expressions for a version.  */
 514
 515 struct bfd_elf_version_expr
 516 {
 517   /* Next regular expression for this version.  */
 518   struct bfd_elf_version_expr *next;
 519   /* Regular expression.  */
 520   const char *pattern;
 521   /* Matching function.  */
 522   int (*match) PARAMS((struct bfd_elf_version_expr *, const char *));
 523 };
 524
 525 /* Version dependencies.  */
 526
 527 struct bfd_elf_version_deps
 528 {
 529   /* Next dependency for this version.  */
 530   struct bfd_elf_version_deps *next;
 531   /* The version which this version depends upon.  */
 532   struct bfd_elf_version_tree *version_needed;
 533 };
 534
 535 /* A node in the version tree.  */
 536
 537 struct bfd_elf_version_tree
 538 {
 539   /* Next version.  */
 540   struct bfd_elf_version_tree *next;
 541   /* Name of this version.  */
 542   const char *name;
 543   /* Version number.  */
 544   unsigned int vernum;
 545   /* Regular expressions for global symbols in this version.  */
 546   struct bfd_elf_version_expr *globals;
 547   /* Regular expressions for local symbols in this version.  */
 548   struct bfd_elf_version_expr *locals;
 549   /* List of versions which this version depends upon.  */
 550   struct bfd_elf_version_deps *deps;
 551   /* Index of the version name.  This is used within BFD.  */
 552   unsigned int name_indx;
 553   /* Whether this version tree was used.  This is used within BFD.  */
 554   int used;
 555 };
 556
 557 #endif