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   /* Which symbols to strip.  */
 205   enum bfd_link_strip strip;
 206   /* Which local symbols to discard.  */
 207   enum bfd_link_discard discard;
 208   /* true if symbols should be retained in memory, false if they
 209      should be freed and reread.  */
 210   boolean keep_memory;
 211   /* The list of input BFD's involved in the link.  These are chained
 212      together via the link_next field.  */
 213   bfd *input_bfds;
 214   /* If a symbol should be created for each input BFD, this is section
 215      where those symbols should be placed.  It must be a section in
 216      the output BFD.  It may be NULL, in which case no such symbols
 217      will be created.  This is to support CREATE_OBJECT_SYMBOLS in the
 218      linker command language.  */
 219   asection *create_object_symbols_section;
 220   /* Hash table handled by BFD.  */
 221   struct bfd_link_hash_table *hash;
 222   /* Hash table of symbols to keep.  This is NULL unless strip is
 223      strip_some.  */
 224   struct bfd_hash_table *keep_hash;
 225   /* true if every symbol should be reported back via the notice
 226      callback.  */
 227   boolean notice_all;
 228   /* Hash table of symbols to report back via the notice callback.  If
 229      this is NULL, and notice_all is false, then no symbols are
 230      reported back.  */
 231   struct bfd_hash_table *notice_hash;
 232   /* Hash table of symbols which are being wrapped (the --wrap linker
 233      option).  If this is NULL, no symbols are being wrapped.  */
 234   struct bfd_hash_table *wrap_hash;
 235   /* If a base output file is wanted, then this points to it */
 236   PTR base_file;
 237
 238   /* If non-zero, specifies that branches which are problematic for the
 239   MPC860 C0 (or earlier) should be checked for and modified.  It gives the
 240   number of bytes that should be checked at the end of each text page. */
 241   int mpc860c0;
 242
 243   /* The function to call when the executable or shared object is
 244      loaded.  */
 245   const char *init_function;
 246   /* The function to call when the executable or shared object is
 247      unloaded.  */
 248   const char *fini_function;
 249
 250   /* true if the new ELF dynamic tags are enabled. */
 251   boolean new_dtags;
 252
 253   /* May be used to set DT_FLAGS for ELF. */
 254   bfd_vma flags;
 255
 256   /* May be used to set DT_FLAGS_1 for ELF. */
 257   bfd_vma flags_1;
 258 };
 259
 260 /* This structures holds a set of callback functions.  These are
 261    called by the BFD linker routines.  The first argument to each
 262    callback function is the bfd_link_info structure being used.  Each
 263    function returns a boolean value.  If the function returns false,
 264    then the BFD function which called it will return with a failure
 265    indication.  */
 266
 267 struct bfd_link_callbacks
 268 {
 269   /* A function which is called when an object is added from an
 270      archive.  ABFD is the archive element being added.  NAME is the
 271      name of the symbol which caused the archive element to be pulled
 272      in.  */
 273   boolean (*add_archive_element) PARAMS ((struct bfd_link_info *,
 274                                           bfd *abfd,
 275                                           const char *name));
 276   /* A function which is called when a symbol is found with multiple
 277      definitions.  NAME is the symbol which is defined multiple times.
 278      OBFD is the old BFD, OSEC is the old section, OVAL is the old
 279      value, NBFD is the new BFD, NSEC is the new section, and NVAL is
 280      the new value.  OBFD may be NULL.  OSEC and NSEC may be
 281      bfd_com_section or bfd_ind_section.  */
 282   boolean (*multiple_definition) PARAMS ((struct bfd_link_info *,
 283                                           const char *name,
 284                                           bfd *obfd,
 285                                           asection *osec,
 286                                           bfd_vma oval,
 287                                           bfd *nbfd,
 288                                           asection *nsec,
 289                                           bfd_vma nval));
 290   /* A function which is called when a common symbol is defined
 291      multiple times.  NAME is the symbol appearing multiple times.
 292      OBFD is the BFD of the existing symbol; it may be NULL if this is
 293      not known.  OTYPE is the type of the existing symbol, which may
 294      be bfd_link_hash_defined, bfd_link_hash_defweak,
 295      bfd_link_hash_common, or bfd_link_hash_indirect.  If OTYPE is
 296      bfd_link_hash_common, OSIZE is the size of the existing symbol.
 297      NBFD is the BFD of the new symbol.  NTYPE is the type of the new
 298      symbol, one of bfd_link_hash_defined, bfd_link_hash_common, or
 299      bfd_link_hash_indirect.  If NTYPE is bfd_link_hash_common, NSIZE
 300      is the size of the new symbol.  */
 301   boolean (*multiple_common) PARAMS ((struct bfd_link_info *,
 302                                       const char *name,
 303                                       bfd *obfd,
 304                                       enum bfd_link_hash_type otype,
 305                                       bfd_vma osize,
 306                                       bfd *nbfd,
 307                                       enum bfd_link_hash_type ntype,
 308                                       bfd_vma nsize));
 309   /* A function which is called to add a symbol to a set.  ENTRY is
 310      the link hash table entry for the set itself (e.g.,
 311      __CTOR_LIST__).  RELOC is the relocation to use for an entry in
 312      the set when generating a relocateable file, and is also used to
 313      get the size of the entry when generating an executable file.
 314      ABFD, SEC and VALUE identify the value to add to the set.  */
 315   boolean (*add_to_set) PARAMS ((struct bfd_link_info *,
 316                                  struct bfd_link_hash_entry *entry,
 317                                  bfd_reloc_code_real_type reloc,
 318                                  bfd *abfd, asection *sec, bfd_vma value));
 319   /* A function which is called when the name of a g++ constructor or
 320      destructor is found.  This is only called by some object file
 321      formats.  CONSTRUCTOR is true for a constructor, false for a
 322      destructor.  This will use BFD_RELOC_CTOR when generating a
 323      relocateable file.  NAME is the name of the symbol found.  ABFD,
 324      SECTION and VALUE are the value of the symbol.  */
 325   boolean (*constructor) PARAMS ((struct bfd_link_info *,
 326                                   boolean constructor,
 327                                   const char *name, bfd *abfd, asection *sec,
 328                                   bfd_vma value));
 329   /* A function which is called to issue a linker warning.  For
 330      example, this is called when there is a reference to a warning
 331      symbol.  WARNING is the warning to be issued.  SYMBOL is the name
 332      of the symbol which triggered the warning; it may be NULL if
 333      there is none.  ABFD, SECTION and ADDRESS identify the location
 334      which trigerred the warning; either ABFD or SECTION or both may
 335      be NULL if the location is not known.  */
 336   boolean (*warning) PARAMS ((struct bfd_link_info *,
 337                               const char *warning, const char *symbol,
 338                               bfd *abfd, asection *section,
 339                               bfd_vma address));
 340   /* A function which is called when a relocation is attempted against
 341      an undefined symbol.  NAME is the symbol which is undefined.
 342      ABFD, SECTION and ADDRESS identify the location from which the
 343      reference is made. FATAL indicates whether an undefined symbol is
 344      a fatal error or not. In some cases SECTION may be NULL.  */
 345   boolean (*undefined_symbol) PARAMS ((struct bfd_link_info *,
 346                                        const char *name, bfd *abfd,
 347                                        asection *section,
 348                                        bfd_vma address,
 349                                        boolean fatal));
 350   /* A function which is called when a reloc overflow occurs.  NAME is
 351      the name of the symbol or section the reloc is against,
 352      RELOC_NAME is the name of the relocation, and ADDEND is any
 353      addend that is used.  ABFD, SECTION and ADDRESS identify the
 354      location at which the overflow occurs; if this is the result of a
 355      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 356      ABFD will be NULL.  */
 357   boolean (*reloc_overflow) PARAMS ((struct bfd_link_info *,
 358                                      const char *name,
 359                                      const char *reloc_name, bfd_vma addend,
 360                                      bfd *abfd, asection *section,
 361                                      bfd_vma address));
 362   /* A function which is called when a dangerous reloc is performed.
 363      The canonical example is an a29k IHCONST reloc which does not
 364      follow an IHIHALF reloc.  MESSAGE is an appropriate message.
 365      ABFD, SECTION and ADDRESS identify the location at which the
 366      problem occurred; if this is the result of a
 367      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 368      ABFD will be NULL.  */
 369   boolean (*reloc_dangerous) PARAMS ((struct bfd_link_info *,
 370                                       const char *message,
 371                                       bfd *abfd, asection *section,
 372                                       bfd_vma address));
 373   /* A function which is called when a reloc is found to be attached
 374      to a symbol which is not being written out.  NAME is the name of
 375      the symbol.  ABFD, SECTION and ADDRESS identify the location of
 376      the reloc; if this is the result of a
 377      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 378      ABFD will be NULL.  */
 379   boolean (*unattached_reloc) PARAMS ((struct bfd_link_info *,
 380                                        const char *name,
 381                                        bfd *abfd, asection *section,
 382                                        bfd_vma address));
 383   /* A function which is called when a symbol in notice_hash is
 384      defined or referenced.  NAME is the symbol.  ABFD, SECTION and
 385      ADDRESS are the value of the symbol.  If SECTION is
 386      bfd_und_section, this is a reference.  */
 387   boolean (*notice) PARAMS ((struct bfd_link_info *, const char *name,
 388                              bfd *abfd, asection *section, bfd_vma address));
 389 };
 390 \f
 391 /* The linker builds link_order structures which tell the code how to
 392    include input data in the output file.  */
 393
 394 /* These are the types of link_order structures.  */
 395
 396 enum bfd_link_order_type
 397 {
 398   bfd_undefined_link_order,     /* Undefined.  */
 399   bfd_indirect_link_order,      /* Built from a section.  */
 400   bfd_fill_link_order,          /* Fill with a 16 bit constant.  */
 401   bfd_data_link_order,          /* Set to explicit data.  */
 402   bfd_section_reloc_link_order, /* Relocate against a section.  */
 403   bfd_symbol_reloc_link_order   /* Relocate against a symbol.  */
 404 };
 405
 406 /* This is the link_order structure itself.  These form a chain
 407    attached to the section whose contents they are describing.  */
 408
 409 struct bfd_link_order
 410 {
 411   /* Next link_order in chain.  */
 412   struct bfd_link_order *next;
 413   /* Type of link_order.  */
 414   enum bfd_link_order_type type;
 415   /* Offset within output section.  */
 416   bfd_vma offset;
 417   /* Size within output section.  */
 418   bfd_size_type size;
 419   /* Type specific information.  */
 420   union
 421     {
 422       struct
 423         {
 424           /* Section to include.  If this is used, then
 425              section->output_section must be the section the
 426              link_order is attached to, section->output_offset must
 427              equal the link_order offset field, and section->_raw_size
 428              must equal the link_order size field.  Maybe these
 429              restrictions should be relaxed someday.  */
 430           asection *section;
 431         } indirect;
 432       struct
 433         {
 434           /* Value to fill with.  */
 435           unsigned int value;
 436         } fill;
 437       struct
 438         {
 439           /* Data to put into file.  The size field gives the number
 440              of bytes which this field points to.  */
 441           bfd_byte *contents;
 442         } data;
 443       struct
 444         {
 445           /* Description of reloc to generate.  Used for
 446              bfd_section_reloc_link_order and
 447              bfd_symbol_reloc_link_order.  */
 448           struct bfd_link_order_reloc *p;
 449         } reloc;
 450     } u;
 451 };
 452
 453 /* A linker order of type bfd_section_reloc_link_order or
 454    bfd_symbol_reloc_link_order means to create a reloc against a
 455    section or symbol, respectively.  This is used to implement -Ur to
 456    generate relocs for the constructor tables.  The
 457    bfd_link_order_reloc structure describes the reloc that BFD should
 458    create.  It is similar to a arelent, but I didn't use arelent
 459    because the linker does not know anything about most symbols, and
 460    any asymbol structure it creates will be partially meaningless.
 461    This information could logically be in the bfd_link_order struct,
 462    but I didn't want to waste the space since these types of relocs
 463    are relatively rare.  */
 464
 465 struct bfd_link_order_reloc
 466 {
 467   /* Reloc type.  */
 468   bfd_reloc_code_real_type reloc;
 469
 470   union
 471     {
 472       /* For type bfd_section_reloc_link_order, this is the section
 473          the reloc should be against.  This must be a section in the
 474          output BFD, not any of the input BFDs.  */
 475       asection *section;
 476       /* For type bfd_symbol_reloc_link_order, this is the name of the
 477          symbol the reloc should be against.  */
 478       const char *name;
 479     } u;
 480
 481   /* Addend to use.  The object file should contain zero.  The BFD
 482      backend is responsible for filling in the contents of the object
 483      file correctly.  For some object file formats (e.g., COFF) the
 484      addend must be stored into in the object file, and for some
 485      (e.g., SPARC a.out) it is kept in the reloc.  */
 486   bfd_vma addend;
 487 };
 488
 489 /* Allocate a new link_order for a section.  */
 490 extern struct bfd_link_order *bfd_new_link_order PARAMS ((bfd *, asection *));
 491
 492 /* These structures are used to describe version information for the
 493    ELF linker.  These structures could be manipulated entirely inside
 494    BFD, but it would be a pain.  Instead, the regular linker sets up
 495    these structures, and then passes them into BFD.  */
 496
 497 /* Regular expressions for a version.  */
 498
 499 struct bfd_elf_version_expr
 500 {
 501   /* Next regular expression for this version.  */
 502   struct bfd_elf_version_expr *next;
 503   /* Regular expression.  */
 504   const char *pattern;
 505   /* Matching function.  */
 506   int (*match) PARAMS((struct bfd_elf_version_expr *, const char *));
 507 };
 508
 509 /* Version dependencies.  */
 510
 511 struct bfd_elf_version_deps
 512 {
 513   /* Next dependency for this version.  */
 514   struct bfd_elf_version_deps *next;
 515   /* The version which this version depends upon.  */
 516   struct bfd_elf_version_tree *version_needed;
 517 };
 518
 519 /* A node in the version tree.  */
 520
 521 struct bfd_elf_version_tree
 522 {
 523   /* Next version.  */
 524   struct bfd_elf_version_tree *next;
 525   /* Name of this version.  */
 526   const char *name;
 527   /* Version number.  */
 528   unsigned int vernum;
 529   /* Regular expressions for global symbols in this version.  */
 530   struct bfd_elf_version_expr *globals;
 531   /* Regular expressions for local symbols in this version.  */
 532   struct bfd_elf_version_expr *locals;
 533   /* List of versions which this version depends upon.  */
 534   struct bfd_elf_version_deps *deps;
 535   /* Index of the version name.  This is used within BFD.  */
 536   unsigned int name_indx;
 537   /* Whether this version tree was used.  This is used within BFD.  */
 538   int used;
 539 };
 540
 541 #endif