include/bfdlink.h

   1 /* bfdlink.h -- header file for BFD link routines
   2    Copyright 1993, 94, 95, 96, 97, 1999 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 2 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  20
  21 #ifndef BFDLINK_H
  22 #define BFDLINK_H
  23
  24 /* Which symbols to strip during a link.  */
  25 enum bfd_link_strip
  26 {
  27   strip_none,           /* Don't strip any symbols.  */
  28   strip_debugger,       /* Strip debugging symbols.  */
  29   strip_some,           /* keep_hash is the list of symbols to keep.  */
  30   strip_all             /* Strip all symbols.  */
  31 };
  32
  33 /* Which local symbols to discard during a link.  This is irrelevant
  34    if strip_all is used.  */
  35 enum bfd_link_discard
  36 {
  37   discard_none,         /* Don't discard any locals.  */
  38   discard_l,            /* Discard local temporary symbols.  */
  39   discard_all           /* Discard all locals.  */
  40 };
  41 \f
  42 /* These are the possible types of an entry in the BFD link hash
  43    table.  */
  44
  45 enum bfd_link_hash_type
  46 {
  47   bfd_link_hash_new,            /* Symbol is new.  */
  48   bfd_link_hash_undefined,      /* Symbol seen before, but undefined.  */
  49   bfd_link_hash_undefweak,      /* Symbol is weak and undefined.  */
  50   bfd_link_hash_defined,        /* Symbol is defined.  */
  51   bfd_link_hash_defweak,        /* Symbol is weak and defined.  */
  52   bfd_link_hash_common,         /* Symbol is common.  */
  53   bfd_link_hash_indirect,       /* Symbol is an indirect link.  */
  54   bfd_link_hash_warning         /* Like indirect, but warn if referenced.  */
  55 };
  56
  57 /* The linking routines use a hash table which uses this structure for
  58    its elements.  */
  59
  60 struct bfd_link_hash_entry
  61 {
  62   /* Base hash table entry structure.  */
  63   struct bfd_hash_entry root;
  64   /* Type of this entry.  */
  65   enum bfd_link_hash_type type;
  66
  67   /* Undefined and common symbols are kept in a linked list through
  68      this field.  This field is not in the union because that would
  69      force us to remove entries from the list when we changed their
  70      type, which would force the list to be doubly linked, which would
  71      waste more memory.  When an undefined or common symbol is
  72      created, it should be added to this list, the head of which is in
  73      the link hash table itself.  As symbols are defined, they need
  74      not be removed from the list; anything which reads the list must
  75      doublecheck the symbol type.
  76
  77      Weak symbols are not kept on this list.
  78
  79      Defined and defweak symbols use this field as a reference marker.
  80      If the field is not NULL, or this structure is the tail of the
  81      undefined symbol list, the symbol has been referenced.  If the
  82      symbol is undefined and becomes defined, this field will
  83      automatically be non-NULL since the symbol will have been on the
  84      undefined symbol list.  */
  85   struct bfd_link_hash_entry *next;
  86   /* A union of information depending upon the type.  */
  87   union
  88     {
  89       /* Nothing is kept for bfd_hash_new.  */
  90       /* bfd_link_hash_undefined, bfd_link_hash_undefweak.  */
  91       struct
  92         {
  93           bfd *abfd;            /* BFD symbol was found in.  */
  94         } undef;
  95       /* bfd_link_hash_defined, bfd_link_hash_defweak.  */
  96       struct
  97         {
  98           bfd_vma value;        /* Symbol value.  */
  99           asection *section;    /* Symbol section.  */
 100         } def;
 101       /* bfd_link_hash_indirect, bfd_link_hash_warning.  */
 102       struct
 103         {
 104           struct bfd_link_hash_entry *link;     /* Real symbol.  */
 105           const char *warning;  /* Warning (bfd_link_hash_warning only).  */
 106         } i;
 107       /* bfd_link_hash_common.  */
 108       struct
 109         {
 110           /* The linker needs to know three things about common
 111              symbols: the size, the alignment, and the section in
 112              which the symbol should be placed.  We store the size
 113              here, and we allocate a small structure to hold the
 114              section and the alignment.  The alignment is stored as a
 115              power of two.  We don't store all the information
 116              directly because we don't want to increase the size of
 117              the union; this structure is a major space user in the
 118              linker.  */
 119           bfd_size_type size;   /* Common symbol size.  */
 120           struct bfd_link_hash_common_entry
 121             {
 122               unsigned int alignment_power;     /* Alignment.  */
 123               asection *section;                /* Symbol section.  */
 124             } *p;
 125         } c;
 126     } u;
 127 };
 128
 129 /* This is the link hash table.  It is a derived class of
 130    bfd_hash_table.  */
 131
 132 struct bfd_link_hash_table
 133 {
 134   /* The hash table itself.  */
 135   struct bfd_hash_table table;
 136   /* The back end which created this hash table.  This indicates the
 137      type of the entries in the hash table, which is sometimes
 138      important information when linking object files of different
 139      types together.  */
 140   const bfd_target *creator;
 141   /* A linked list of undefined and common symbols, linked through the
 142      next field in the bfd_link_hash_entry structure.  */
 143   struct bfd_link_hash_entry *undefs;
 144   /* Entries are added to the tail of the undefs list.  */
 145   struct bfd_link_hash_entry *undefs_tail;
 146 };
 147
 148 /* Look up an entry in a link hash table.  If FOLLOW is true, this
 149    follows bfd_link_hash_indirect and bfd_link_hash_warning links to
 150    the real symbol.  */
 151 extern struct bfd_link_hash_entry *bfd_link_hash_lookup
 152   PARAMS ((struct bfd_link_hash_table *, const char *, boolean create,
 153            boolean copy, boolean follow));
 154
 155 /* Look up an entry in the main linker hash table if the symbol might
 156    be wrapped.  This should only be used for references to an
 157    undefined symbol, not for definitions of a symbol.  */
 158
 159 extern struct bfd_link_hash_entry *bfd_wrapped_link_hash_lookup
 160   PARAMS ((bfd *, struct bfd_link_info *, const char *, boolean, boolean,
 161            boolean));
 162
 163 /* Traverse a link hash table.  */
 164 extern void bfd_link_hash_traverse
 165   PARAMS ((struct bfd_link_hash_table *,
 166            boolean (*) (struct bfd_link_hash_entry *, PTR),
 167            PTR));
 168
 169 /* Add an entry to the undefs list.  */
 170 extern void bfd_link_add_undef
 171   PARAMS ((struct bfd_link_hash_table *, struct bfd_link_hash_entry *));
 172 \f
 173 /* This structure holds all the information needed to communicate
 174    between BFD and the linker when doing a link.  */
 175
 176 struct bfd_link_info
 177 {
 178   /* Function callbacks.  */
 179   const struct bfd_link_callbacks *callbacks;
 180   /* true if BFD should generate a relocateable object file.  */
 181   boolean relocateable;
 182   /* true if BFD should generate relocation information in the final executable.  */
 183   boolean emitrelocations;
 184   /* true if BFD should generate a "task linked" object file,
 185      similar to relocatable but also with globals converted to statics. */
 186   boolean task_link;
 187   /* true if BFD should generate a shared object.  */
 188   boolean shared;
 189   /* true if BFD should pre-bind symbols in a shared object.  */
 190   boolean symbolic;
 191   /* true if shared objects should be linked directly, not shared.  */
 192   boolean static_link;
 193   /* true if the output file should be in a traditional format.  This
 194      is equivalent to the setting of the BFD_TRADITIONAL_FORMAT flag
 195      on the output file, but may be checked when reading the input
 196      files.  */
 197   boolean traditional_format;
 198   /* true if we want to produced optimized output files.  This might
 199      need much more time and therefore must be explicitly selected.  */
 200   boolean optimize;
 201   /* true if BFD should generate errors for undefined symbols
 202      even if generating a shared object.  */
 203   boolean no_undefined;
 204   /* true if BFD should allow undefined symbols in shared objects even
 205      when no_undefined is set to disallow undefined symbols.  The net
 206      result will be that undefined symbols in regular objects will
 207      still trigger an error, but undefined symbols in shared objects
 208      will be ignored.  The implementation of no_undefined makes the
 209      assumption that the runtime linker will choke on undefined
 210      symbols.  However there is at least one system (BeOS) where
 211      undefined symbols in shared libraries is normal since the kernel
 212      patches them at load time to select which function is most
 213      appropriate for the current architecture.  I.E. dynamically
 214      select an appropriate memset function.  Apparently it is also
 215      normal for HPPA shared libraries to have undefined symbols.  */
 216   boolean allow_shlib_undefined;
 217   /* Which symbols to strip.  */
 218   enum bfd_link_strip strip;
 219   /* Which local symbols to discard.  */
 220   enum bfd_link_discard discard;
 221   /* true if symbols should be retained in memory, false if they
 222      should be freed and reread.  */
 223   boolean keep_memory;
 224   /* The list of input BFD's involved in the link.  These are chained
 225      together via the link_next field.  */
 226   bfd *input_bfds;
 227   /* If a symbol should be created for each input BFD, this is section
 228      where those symbols should be placed.  It must be a section in
 229      the output BFD.  It may be NULL, in which case no such symbols
 230      will be created.  This is to support CREATE_OBJECT_SYMBOLS in the
 231      linker command language.  */
 232   asection *create_object_symbols_section;
 233   /* Hash table handled by BFD.  */
 234   struct bfd_link_hash_table *hash;
 235   /* Hash table of symbols to keep.  This is NULL unless strip is
 236      strip_some.  */
 237   struct bfd_hash_table *keep_hash;
 238   /* true if every symbol should be reported back via the notice
 239      callback.  */
 240   boolean notice_all;
 241   /* Hash table of symbols to report back via the notice callback.  If
 242      this is NULL, and notice_all is false, then no symbols are
 243      reported back.  */
 244   struct bfd_hash_table *notice_hash;
 245   /* Hash table of symbols which are being wrapped (the --wrap linker
 246      option).  If this is NULL, no symbols are being wrapped.  */
 247   struct bfd_hash_table *wrap_hash;
 248   /* If a base output file is wanted, then this points to it */
 249   PTR base_file;
 250
 251   /* If non-zero, specifies that branches which are problematic for the
 252   MPC860 C0 (or earlier) should be checked for and modified.  It gives the
 253   number of bytes that should be checked at the end of each text page. */
 254   int mpc860c0;
 255
 256   /* The function to call when the executable or shared object is
 257      loaded.  */
 258   const char *init_function;
 259   /* The function to call when the executable or shared object is
 260      unloaded.  */
 261   const char *fini_function;
 262
 263   /* true if the new ELF dynamic tags are enabled. */
 264   boolean new_dtags;
 265
 266   /* May be used to set DT_FLAGS for ELF. */
 267   bfd_vma flags;
 268
 269   /* May be used to set DT_FLAGS_1 for ELF. */
 270   bfd_vma flags_1;
 271 };
 272
 273 /* This structures holds a set of callback functions.  These are
 274    called by the BFD linker routines.  The first argument to each
 275    callback function is the bfd_link_info structure being used.  Each
 276    function returns a boolean value.  If the function returns false,
 277    then the BFD function which called it will return with a failure
 278    indication.  */
 279
 280 struct bfd_link_callbacks
 281 {
 282   /* A function which is called when an object is added from an
 283      archive.  ABFD is the archive element being added.  NAME is the
 284      name of the symbol which caused the archive element to be pulled
 285      in.  */
 286   boolean (*add_archive_element) PARAMS ((struct bfd_link_info *,
 287                                           bfd *abfd,
 288                                           const char *name));
 289   /* A function which is called when a symbol is found with multiple
 290      definitions.  NAME is the symbol which is defined multiple times.
 291      OBFD is the old BFD, OSEC is the old section, OVAL is the old
 292      value, NBFD is the new BFD, NSEC is the new section, and NVAL is
 293      the new value.  OBFD may be NULL.  OSEC and NSEC may be
 294      bfd_com_section or bfd_ind_section.  */
 295   boolean (*multiple_definition) PARAMS ((struct bfd_link_info *,
 296                                           const char *name,
 297                                           bfd *obfd,
 298                                           asection *osec,
 299                                           bfd_vma oval,
 300                                           bfd *nbfd,
 301                                           asection *nsec,
 302                                           bfd_vma nval));
 303   /* A function which is called when a common symbol is defined
 304      multiple times.  NAME is the symbol appearing multiple times.
 305      OBFD is the BFD of the existing symbol; it may be NULL if this is
 306      not known.  OTYPE is the type of the existing symbol, which may
 307      be bfd_link_hash_defined, bfd_link_hash_defweak,
 308      bfd_link_hash_common, or bfd_link_hash_indirect.  If OTYPE is
 309      bfd_link_hash_common, OSIZE is the size of the existing symbol.
 310      NBFD is the BFD of the new symbol.  NTYPE is the type of the new
 311      symbol, one of bfd_link_hash_defined, bfd_link_hash_common, or
 312      bfd_link_hash_indirect.  If NTYPE is bfd_link_hash_common, NSIZE
 313      is the size of the new symbol.  */
 314   boolean (*multiple_common) PARAMS ((struct bfd_link_info *,
 315                                       const char *name,
 316                                       bfd *obfd,
 317                                       enum bfd_link_hash_type otype,
 318                                       bfd_vma osize,
 319                                       bfd *nbfd,
 320                                       enum bfd_link_hash_type ntype,
 321                                       bfd_vma nsize));
 322   /* A function which is called to add a symbol to a set.  ENTRY is
 323      the link hash table entry for the set itself (e.g.,
 324      __CTOR_LIST__).  RELOC is the relocation to use for an entry in
 325      the set when generating a relocateable file, and is also used to
 326      get the size of the entry when generating an executable file.
 327      ABFD, SEC and VALUE identify the value to add to the set.  */
 328   boolean (*add_to_set) PARAMS ((struct bfd_link_info *,
 329                                  struct bfd_link_hash_entry *entry,
 330                                  bfd_reloc_code_real_type reloc,
 331                                  bfd *abfd, asection *sec, bfd_vma value));
 332   /* A function which is called when the name of a g++ constructor or
 333      destructor is found.  This is only called by some object file
 334      formats.  CONSTRUCTOR is true for a constructor, false for a
 335      destructor.  This will use BFD_RELOC_CTOR when generating a
 336      relocateable file.  NAME is the name of the symbol found.  ABFD,
 337      SECTION and VALUE are the value of the symbol.  */
 338   boolean (*constructor) PARAMS ((struct bfd_link_info *,
 339                                   boolean constructor,
 340                                   const char *name, bfd *abfd, asection *sec,
 341                                   bfd_vma value));
 342   /* A function which is called to issue a linker warning.  For
 343      example, this is called when there is a reference to a warning
 344      symbol.  WARNING is the warning to be issued.  SYMBOL is the name
 345      of the symbol which triggered the warning; it may be NULL if
 346      there is none.  ABFD, SECTION and ADDRESS identify the location
 347      which trigerred the warning; either ABFD or SECTION or both may
 348      be NULL if the location is not known.  */
 349   boolean (*warning) PARAMS ((struct bfd_link_info *,
 350                               const char *warning, const char *symbol,
 351                               bfd *abfd, asection *section,
 352                               bfd_vma address));
 353   /* A function which is called when a relocation is attempted against
 354      an undefined symbol.  NAME is the symbol which is undefined.
 355      ABFD, SECTION and ADDRESS identify the location from which the
 356      reference is made. FATAL indicates whether an undefined symbol is
 357      a fatal error or not. In some cases SECTION may be NULL.  */
 358   boolean (*undefined_symbol) PARAMS ((struct bfd_link_info *,
 359                                        const char *name, bfd *abfd,
 360                                        asection *section,
 361                                        bfd_vma address,
 362                                        boolean fatal));
 363   /* A function which is called when a reloc overflow occurs.  NAME is
 364      the name of the symbol or section the reloc is against,
 365      RELOC_NAME is the name of the relocation, and ADDEND is any
 366      addend that is used.  ABFD, SECTION and ADDRESS identify the
 367      location at which the overflow occurs; if this is the result of a
 368      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 369      ABFD will be NULL.  */
 370   boolean (*reloc_overflow) PARAMS ((struct bfd_link_info *,
 371                                      const char *name,
 372                                      const char *reloc_name, bfd_vma addend,
 373                                      bfd *abfd, asection *section,
 374                                      bfd_vma address));
 375   /* A function which is called when a dangerous reloc is performed.
 376      The canonical example is an a29k IHCONST reloc which does not
 377      follow an IHIHALF reloc.  MESSAGE is an appropriate message.
 378      ABFD, SECTION and ADDRESS identify the location at which the
 379      problem occurred; if this is the result of a
 380      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 381      ABFD will be NULL.  */
 382   boolean (*reloc_dangerous) PARAMS ((struct bfd_link_info *,
 383                                       const char *message,
 384                                       bfd *abfd, asection *section,
 385                                       bfd_vma address));
 386   /* A function which is called when a reloc is found to be attached
 387      to a symbol which is not being written out.  NAME is the name of
 388      the symbol.  ABFD, SECTION and ADDRESS identify the location of
 389      the reloc; if this is the result of a
 390      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 391      ABFD will be NULL.  */
 392   boolean (*unattached_reloc) PARAMS ((struct bfd_link_info *,
 393                                        const char *name,
 394                                        bfd *abfd, asection *section,
 395                                        bfd_vma address));
 396   /* A function which is called when a symbol in notice_hash is
 397      defined or referenced.  NAME is the symbol.  ABFD, SECTION and
 398      ADDRESS are the value of the symbol.  If SECTION is
 399      bfd_und_section, this is a reference.  */
 400   boolean (*notice) PARAMS ((struct bfd_link_info *, const char *name,
 401                              bfd *abfd, asection *section, bfd_vma address));
 402 };
 403 \f
 404 /* The linker builds link_order structures which tell the code how to
 405    include input data in the output file.  */
 406
 407 /* These are the types of link_order structures.  */
 408
 409 enum bfd_link_order_type
 410 {
 411   bfd_undefined_link_order,     /* Undefined.  */
 412   bfd_indirect_link_order,      /* Built from a section.  */
 413   bfd_fill_link_order,          /* Fill with a 16 bit constant.  */
 414   bfd_data_link_order,          /* Set to explicit data.  */
 415   bfd_section_reloc_link_order, /* Relocate against a section.  */
 416   bfd_symbol_reloc_link_order   /* Relocate against a symbol.  */
 417 };
 418
 419 /* This is the link_order structure itself.  These form a chain
 420    attached to the section whose contents they are describing.  */
 421
 422 struct bfd_link_order
 423 {
 424   /* Next link_order in chain.  */
 425   struct bfd_link_order *next;
 426   /* Type of link_order.  */
 427   enum bfd_link_order_type type;
 428   /* Offset within output section.  */
 429   bfd_vma offset;
 430   /* Size within output section.  */
 431   bfd_size_type size;
 432   /* Type specific information.  */
 433   union
 434     {
 435       struct
 436         {
 437           /* Section to include.  If this is used, then
 438              section->output_section must be the section the
 439              link_order is attached to, section->output_offset must
 440              equal the link_order offset field, and section->_raw_size
 441              must equal the link_order size field.  Maybe these
 442              restrictions should be relaxed someday.  */
 443           asection *section;
 444         } indirect;
 445       struct
 446         {
 447           /* Value to fill with.  */
 448           unsigned int value;
 449         } fill;
 450       struct
 451         {
 452           /* Data to put into file.  The size field gives the number
 453              of bytes which this field points to.  */
 454           bfd_byte *contents;
 455         } data;
 456       struct
 457         {
 458           /* Description of reloc to generate.  Used for
 459              bfd_section_reloc_link_order and
 460              bfd_symbol_reloc_link_order.  */
 461           struct bfd_link_order_reloc *p;
 462         } reloc;
 463     } u;
 464 };
 465
 466 /* A linker order of type bfd_section_reloc_link_order or
 467    bfd_symbol_reloc_link_order means to create a reloc against a
 468    section or symbol, respectively.  This is used to implement -Ur to
 469    generate relocs for the constructor tables.  The
 470    bfd_link_order_reloc structure describes the reloc that BFD should
 471    create.  It is similar to a arelent, but I didn't use arelent
 472    because the linker does not know anything about most symbols, and
 473    any asymbol structure it creates will be partially meaningless.
 474    This information could logically be in the bfd_link_order struct,
 475    but I didn't want to waste the space since these types of relocs
 476    are relatively rare.  */
 477
 478 struct bfd_link_order_reloc
 479 {
 480   /* Reloc type.  */
 481   bfd_reloc_code_real_type reloc;
 482
 483   union
 484     {
 485       /* For type bfd_section_reloc_link_order, this is the section
 486          the reloc should be against.  This must be a section in the
 487          output BFD, not any of the input BFDs.  */
 488       asection *section;
 489       /* For type bfd_symbol_reloc_link_order, this is the name of the
 490          symbol the reloc should be against.  */
 491       const char *name;
 492     } u;
 493
 494   /* Addend to use.  The object file should contain zero.  The BFD
 495      backend is responsible for filling in the contents of the object
 496      file correctly.  For some object file formats (e.g., COFF) the
 497      addend must be stored into in the object file, and for some
 498      (e.g., SPARC a.out) it is kept in the reloc.  */
 499   bfd_vma addend;
 500 };
 501
 502 /* Allocate a new link_order for a section.  */
 503 extern struct bfd_link_order *bfd_new_link_order PARAMS ((bfd *, asection *));
 504
 505 /* These structures are used to describe version information for the
 506    ELF linker.  These structures could be manipulated entirely inside
 507    BFD, but it would be a pain.  Instead, the regular linker sets up
 508    these structures, and then passes them into BFD.  */
 509
 510 /* Regular expressions for a version.  */
 511
 512 struct bfd_elf_version_expr
 513 {
 514   /* Next regular expression for this version.  */
 515   struct bfd_elf_version_expr *next;
 516   /* Regular expression.  */
 517   const char *pattern;
 518   /* Matching function.  */
 519   int (*match) PARAMS((struct bfd_elf_version_expr *, const char *));
 520 };
 521
 522 /* Version dependencies.  */
 523
 524 struct bfd_elf_version_deps
 525 {
 526   /* Next dependency for this version.  */
 527   struct bfd_elf_version_deps *next;
 528   /* The version which this version depends upon.  */
 529   struct bfd_elf_version_tree *version_needed;
 530 };
 531
 532 /* A node in the version tree.  */
 533
 534 struct bfd_elf_version_tree
 535 {
 536   /* Next version.  */
 537   struct bfd_elf_version_tree *next;
 538   /* Name of this version.  */
 539   const char *name;
 540   /* Version number.  */
 541   unsigned int vernum;
 542   /* Regular expressions for global symbols in this version.  */
 543   struct bfd_elf_version_expr *globals;
 544   /* Regular expressions for local symbols in this version.  */
 545   struct bfd_elf_version_expr *locals;
 546   /* List of versions which this version depends upon.  */
 547   struct bfd_elf_version_deps *deps;
 548   /* Index of the version name.  This is used within BFD.  */
 549   unsigned int name_indx;
 550   /* Whether this version tree was used.  This is used within BFD.  */
 551   int used;
 552 };
 553
 554 #endif