include/bfdlink.h

   1 /* bfdlink.h -- header file for BFD link routines
   2    Copyright 1993, 94, 95, 96, 1997 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 a "task linked" object file,
 183      similar to relocatable but also with globals converted to statics. */
 184   boolean task_link;
 185   /* true if BFD should generate a shared object.  */
 186   boolean shared;
 187   /* true if BFD should pre-bind symbols in a shared object.  */
 188   boolean symbolic;
 189   /* true if shared objects should be linked directly, not shared.  */
 190   boolean static_link;
 191   /* true if the output file should be in a traditional format.  This
 192      is equivalent to the setting of the BFD_TRADITIONAL_FORMAT flag
 193      on the output file, but may be checked when reading the input
 194      files.  */
 195   boolean traditional_format;
 196   /* true if we want to produced optimized output files.  This might
 197      need much more time and therefore must be explicitly selected.  */
 198   boolean optimize;
 199   /* Which symbols to strip.  */
 200   enum bfd_link_strip strip;
 201   /* Which local symbols to discard.  */
 202   enum bfd_link_discard discard;
 203   /* true if symbols should be retained in memory, false if they
 204      should be freed and reread.  */
 205   boolean keep_memory;
 206   /* The list of input BFD's involved in the link.  These are chained
 207      together via the link_next field.  */
 208   bfd *input_bfds;
 209   /* If a symbol should be created for each input BFD, this is section
 210      where those symbols should be placed.  It must be a section in
 211      the output BFD.  It may be NULL, in which case no such symbols
 212      will be created.  This is to support CREATE_OBJECT_SYMBOLS in the
 213      linker command language.  */
 214   asection *create_object_symbols_section;
 215   /* Hash table handled by BFD.  */
 216   struct bfd_link_hash_table *hash;
 217   /* Hash table of symbols to keep.  This is NULL unless strip is
 218      strip_some.  */
 219   struct bfd_hash_table *keep_hash;
 220   /* true if every symbol should be reported back via the notice
 221      callback.  */
 222   boolean notice_all;
 223   /* Hash table of symbols to report back via the notice callback.  If
 224      this is NULL, and notice_all is false, then no symbols are
 225      reported back.  */
 226   struct bfd_hash_table *notice_hash;
 227   /* Hash table of symbols which are being wrapped (the --wrap linker
 228      option).  If this is NULL, no symbols are being wrapped.  */
 229   struct bfd_hash_table *wrap_hash;
 230   /* If a base output file is wanted, then this points to it */
 231   PTR base_file;
 232 };
 233
 234 /* This structures holds a set of callback functions.  These are
 235    called by the BFD linker routines.  The first argument to each
 236    callback function is the bfd_link_info structure being used.  Each
 237    function returns a boolean value.  If the function returns false,
 238    then the BFD function which called it will return with a failure
 239    indication.  */
 240
 241 struct bfd_link_callbacks
 242 {
 243   /* A function which is called when an object is added from an
 244      archive.  ABFD is the archive element being added.  NAME is the
 245      name of the symbol which caused the archive element to be pulled
 246      in.  */
 247   boolean (*add_archive_element) PARAMS ((struct bfd_link_info *,
 248                                           bfd *abfd,
 249                                           const char *name));
 250   /* A function which is called when a symbol is found with multiple
 251      definitions.  NAME is the symbol which is defined multiple times.
 252      OBFD is the old BFD, OSEC is the old section, OVAL is the old
 253      value, NBFD is the new BFD, NSEC is the new section, and NVAL is
 254      the new value.  OBFD may be NULL.  OSEC and NSEC may be
 255      bfd_com_section or bfd_ind_section.  */
 256   boolean (*multiple_definition) PARAMS ((struct bfd_link_info *,
 257                                           const char *name,
 258                                           bfd *obfd,
 259                                           asection *osec,
 260                                           bfd_vma oval,
 261                                           bfd *nbfd,
 262                                           asection *nsec,
 263                                           bfd_vma nval));
 264   /* A function which is called when a common symbol is defined
 265      multiple times.  NAME is the symbol appearing multiple times.
 266      OBFD is the BFD of the existing symbol; it may be NULL if this is
 267      not known.  OTYPE is the type of the existing symbol, which may
 268      be bfd_link_hash_defined, bfd_link_hash_defweak,
 269      bfd_link_hash_common, or bfd_link_hash_indirect.  If OTYPE is
 270      bfd_link_hash_common, OSIZE is the size of the existing symbol.
 271      NBFD is the BFD of the new symbol.  NTYPE is the type of the new
 272      symbol, one of bfd_link_hash_defined, bfd_link_hash_common, or
 273      bfd_link_hash_indirect.  If NTYPE is bfd_link_hash_common, NSIZE
 274      is the size of the new symbol.  */
 275   boolean (*multiple_common) PARAMS ((struct bfd_link_info *,
 276                                       const char *name,
 277                                       bfd *obfd,
 278                                       enum bfd_link_hash_type otype,
 279                                       bfd_vma osize,
 280                                       bfd *nbfd,
 281                                       enum bfd_link_hash_type ntype,
 282                                       bfd_vma nsize));
 283   /* A function which is called to add a symbol to a set.  ENTRY is
 284      the link hash table entry for the set itself (e.g.,
 285      __CTOR_LIST__).  RELOC is the relocation to use for an entry in
 286      the set when generating a relocateable file, and is also used to
 287      get the size of the entry when generating an executable file.
 288      ABFD, SEC and VALUE identify the value to add to the set.  */
 289   boolean (*add_to_set) PARAMS ((struct bfd_link_info *,
 290                                  struct bfd_link_hash_entry *entry,
 291                                  bfd_reloc_code_real_type reloc,
 292                                  bfd *abfd, asection *sec, bfd_vma value));
 293   /* A function which is called when the name of a g++ constructor or
 294      destructor is found.  This is only called by some object file
 295      formats.  CONSTRUCTOR is true for a constructor, false for a
 296      destructor.  This will use BFD_RELOC_CTOR when generating a
 297      relocateable file.  NAME is the name of the symbol found.  ABFD,
 298      SECTION and VALUE are the value of the symbol.  */
 299   boolean (*constructor) PARAMS ((struct bfd_link_info *,
 300                                   boolean constructor,
 301                                   const char *name, bfd *abfd, asection *sec,
 302                                   bfd_vma value));
 303   /* A function which is called to issue a linker warning.  For
 304      example, this is called when there is a reference to a warning
 305      symbol.  WARNING is the warning to be issued.  SYMBOL is the name
 306      of the symbol which triggered the warning; it may be NULL if
 307      there is none.  ABFD, SECTION and ADDRESS identify the location
 308      which trigerred the warning; either ABFD or SECTION or both may
 309      be NULL if the location is not known.  */
 310   boolean (*warning) PARAMS ((struct bfd_link_info *,
 311                               const char *warning, const char *symbol,
 312                               bfd *abfd, asection *section,
 313                               bfd_vma address));
 314   /* A function which is called when a relocation is attempted against
 315      an undefined symbol.  NAME is the symbol which is undefined.
 316      ABFD, SECTION and ADDRESS identify the location from which the
 317      reference is made.  In some cases SECTION may be NULL.  */
 318   boolean (*undefined_symbol) PARAMS ((struct bfd_link_info *,
 319                                        const char *name, bfd *abfd,
 320                                        asection *section, bfd_vma address));
 321   /* A function which is called when a reloc overflow occurs.  NAME is
 322      the name of the symbol or section the reloc is against,
 323      RELOC_NAME is the name of the relocation, and ADDEND is any
 324      addend that is used.  ABFD, SECTION and ADDRESS identify the
 325      location at which the overflow occurs; if this is the result of a
 326      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 327      ABFD will be NULL.  */
 328   boolean (*reloc_overflow) PARAMS ((struct bfd_link_info *,
 329                                      const char *name,
 330                                      const char *reloc_name, bfd_vma addend,
 331                                      bfd *abfd, asection *section,
 332                                      bfd_vma address));
 333   /* A function which is called when a dangerous reloc is performed.
 334      The canonical example is an a29k IHCONST reloc which does not
 335      follow an IHIHALF reloc.  MESSAGE is an appropriate message.
 336      ABFD, SECTION and ADDRESS identify the location at which the
 337      problem occurred; if this is the result of a
 338      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 339      ABFD will be NULL.  */
 340   boolean (*reloc_dangerous) PARAMS ((struct bfd_link_info *,
 341                                       const char *message,
 342                                       bfd *abfd, asection *section,
 343                                       bfd_vma address));
 344   /* A function which is called when a reloc is found to be attached
 345      to a symbol which is not being written out.  NAME is the name of
 346      the symbol.  ABFD, SECTION and ADDRESS identify the location of
 347      the reloc; if this is the result of a
 348      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 349      ABFD will be NULL.  */
 350   boolean (*unattached_reloc) PARAMS ((struct bfd_link_info *,
 351                                        const char *name,
 352                                        bfd *abfd, asection *section,
 353                                        bfd_vma address));
 354   /* A function which is called when a symbol in notice_hash is
 355      defined or referenced.  NAME is the symbol.  ABFD, SECTION and
 356      ADDRESS are the value of the symbol.  If SECTION is
 357      bfd_und_section, this is a reference.  */
 358   boolean (*notice) PARAMS ((struct bfd_link_info *, const char *name,
 359                              bfd *abfd, asection *section, bfd_vma address));
 360 };
 361 \f
 362 /* The linker builds link_order structures which tell the code how to
 363    include input data in the output file.  */
 364
 365 /* These are the types of link_order structures.  */
 366
 367 enum bfd_link_order_type
 368 {
 369   bfd_undefined_link_order,     /* Undefined.  */
 370   bfd_indirect_link_order,      /* Built from a section.  */
 371   bfd_fill_link_order,          /* Fill with a 16 bit constant.  */
 372   bfd_data_link_order,          /* Set to explicit data.  */
 373   bfd_section_reloc_link_order, /* Relocate against a section.  */
 374   bfd_symbol_reloc_link_order   /* Relocate against a symbol.  */
 375 };
 376
 377 /* This is the link_order structure itself.  These form a chain
 378    attached to the section whose contents they are describing.  */
 379
 380 struct bfd_link_order
 381 {
 382   /* Next link_order in chain.  */
 383   struct bfd_link_order *next;
 384   /* Type of link_order.  */
 385   enum bfd_link_order_type type;
 386   /* Offset within output section.  */
 387   bfd_vma offset;
 388   /* Size within output section.  */
 389   bfd_size_type size;
 390   /* Type specific information.  */
 391   union
 392     {
 393       struct
 394         {
 395           /* Section to include.  If this is used, then
 396              section->output_section must be the section the
 397              link_order is attached to, section->output_offset must
 398              equal the link_order offset field, and section->_raw_size
 399              must equal the link_order size field.  Maybe these
 400              restrictions should be relaxed someday.  */
 401           asection *section;
 402         } indirect;
 403       struct
 404         {
 405           /* Value to fill with.  */
 406           unsigned int value;
 407         } fill;
 408       struct
 409         {
 410           /* Data to put into file.  The size field gives the number
 411              of bytes which this field points to.  */
 412           bfd_byte *contents;
 413         } data;
 414       struct
 415         {
 416           /* Description of reloc to generate.  Used for
 417              bfd_section_reloc_link_order and
 418              bfd_symbol_reloc_link_order.  */
 419           struct bfd_link_order_reloc *p;
 420         } reloc;
 421     } u;
 422 };
 423
 424 /* A linker order of type bfd_section_reloc_link_order or
 425    bfd_symbol_reloc_link_order means to create a reloc against a
 426    section or symbol, respectively.  This is used to implement -Ur to
 427    generate relocs for the constructor tables.  The
 428    bfd_link_order_reloc structure describes the reloc that BFD should
 429    create.  It is similar to a arelent, but I didn't use arelent
 430    because the linker does not know anything about most symbols, and
 431    any asymbol structure it creates will be partially meaningless.
 432    This information could logically be in the bfd_link_order struct,
 433    but I didn't want to waste the space since these types of relocs
 434    are relatively rare.  */
 435
 436 struct bfd_link_order_reloc
 437 {
 438   /* Reloc type.  */
 439   bfd_reloc_code_real_type reloc;
 440
 441   union
 442     {
 443       /* For type bfd_section_reloc_link_order, this is the section
 444          the reloc should be against.  This must be a section in the
 445          output BFD, not any of the input BFDs.  */
 446       asection *section;
 447       /* For type bfd_symbol_reloc_link_order, this is the name of the
 448          symbol the reloc should be against.  */
 449       const char *name;
 450     } u;
 451
 452   /* Addend to use.  The object file should contain zero.  The BFD
 453      backend is responsible for filling in the contents of the object
 454      file correctly.  For some object file formats (e.g., COFF) the
 455      addend must be stored into in the object file, and for some
 456      (e.g., SPARC a.out) it is kept in the reloc.  */
 457   bfd_vma addend;
 458 };
 459
 460 /* Allocate a new link_order for a section.  */
 461 extern struct bfd_link_order *bfd_new_link_order PARAMS ((bfd *, asection *));
 462
 463 /* These structures are used to describe version information for the
 464    ELF linker.  These structures could be manipulated entirely inside
 465    BFD, but it would be a pain.  Instead, the regular linker sets up
 466    these structures, and then passes them into BFD.  */
 467
 468 /* Regular expressions for a version.  */
 469
 470 struct bfd_elf_version_expr
 471 {
 472   /* Next regular expression for this version.  */
 473   struct bfd_elf_version_expr *next;
 474   /* Regular expression.  */
 475   const char *match;
 476 };
 477
 478 /* Version dependencies.  */
 479
 480 struct bfd_elf_version_deps
 481 {
 482   /* Next dependency for this version.  */
 483   struct bfd_elf_version_deps *next;
 484   /* The version which this version depends upon.  */
 485   struct bfd_elf_version_tree *version_needed;
 486 };
 487
 488 /* A node in the version tree.  */
 489
 490 struct bfd_elf_version_tree
 491 {
 492   /* Next version.  */
 493   struct bfd_elf_version_tree *next;
 494   /* Name of this version.  */
 495   const char *name;
 496   /* Version number.  */
 497   unsigned int vernum;
 498   /* Regular expressions for global symbols in this version.  */
 499   struct bfd_elf_version_expr *globals;
 500   /* Regular expressions for local symbols in this version.  */
 501   struct bfd_elf_version_expr *locals;
 502   /* List of versions which this version depends upon.  */
 503   struct bfd_elf_version_deps *deps;
 504   /* Index of the version name.  This is used within BFD.  */
 505   unsigned int name_indx;
 506   /* Whether this version tree was used.  This is used within BFD.  */
 507   int used;
 508 };
 509
 510 #endif