Home | History | Annotate | Download | only in include
      1 /* bfdlink.h -- header file for BFD link routines
      2    Copyright 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002,
      3    2003, 2004, 2005, 2006, 2007, 2008, 2009 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 3 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., 51 Franklin Street - Fifth Floor, Boston,
     21    MA 02110-1301, USA.  */
     22 
     23 #ifndef BFDLINK_H
     24 #define BFDLINK_H
     25 
     26 /* Which symbols to strip during a link.  */
     27 enum bfd_link_strip
     28 {
     29   strip_none,		/* Don't strip any symbols.  */
     30   strip_debugger,	/* Strip debugging symbols.  */
     31   strip_some,		/* keep_hash is the list of symbols to keep.  */
     32   strip_all		/* Strip all symbols.  */
     33 };
     34 
     35 /* Which local symbols to discard during a link.  This is irrelevant
     36    if strip_all is used.  */
     37 enum bfd_link_discard
     38 {
     39   discard_sec_merge,	/* Discard local temporary symbols in SEC_MERGE
     40 			   sections.  */
     41   discard_none,		/* Don't discard any locals.  */
     42   discard_l,		/* Discard local temporary symbols.  */
     43   discard_all		/* Discard all locals.  */
     44 };
     45 
     46 /* Describes the type of hash table entry structure being used.
     47    Different hash table structure have different fields and so
     48    support different linking features.  */
     49 enum bfd_link_hash_table_type
     50   {
     51     bfd_link_generic_hash_table,
     52     bfd_link_elf_hash_table
     53   };
     54 
     55 /* These are the possible types of an entry in the BFD link hash
     57    table.  */
     58 
     59 enum bfd_link_hash_type
     60 {
     61   bfd_link_hash_new,		/* Symbol is new.  */
     62   bfd_link_hash_undefined,	/* Symbol seen before, but undefined.  */
     63   bfd_link_hash_undefweak,	/* Symbol is weak and undefined.  */
     64   bfd_link_hash_defined,	/* Symbol is defined.  */
     65   bfd_link_hash_defweak,	/* Symbol is weak and defined.  */
     66   bfd_link_hash_common,		/* Symbol is common.  */
     67   bfd_link_hash_indirect,	/* Symbol is an indirect link.  */
     68   bfd_link_hash_warning		/* Like indirect, but warn if referenced.  */
     69 };
     70 
     71 enum bfd_link_common_skip_ar_symbols
     72 {
     73   bfd_link_common_skip_none,
     74   bfd_link_common_skip_text,
     75   bfd_link_common_skip_data,
     76   bfd_link_common_skip_all
     77 };
     78 
     79 struct bfd_link_hash_common_entry
     80   {
     81     unsigned int alignment_power;	/* Alignment.  */
     82     asection *section;		/* Symbol section.  */
     83   };
     84 
     85 /* The linking routines use a hash table which uses this structure for
     86    its elements.  */
     87 
     88 struct bfd_link_hash_entry
     89 {
     90   /* Base hash table entry structure.  */
     91   struct bfd_hash_entry root;
     92 
     93   /* Type of this entry.  */
     94   enum bfd_link_hash_type type;
     95 
     96   /* A union of information depending upon the type.  */
     97   union
     98     {
     99       /* Nothing is kept for bfd_hash_new.  */
    100       /* bfd_link_hash_undefined, bfd_link_hash_undefweak.  */
    101       struct
    102 	{
    103 	  /* Undefined and common symbols are kept in a linked list through
    104 	     this field.  This field is present in all of the union element
    105 	     so that we don't need to remove entries from the list when we
    106 	     change their type.  Removing entries would either require the
    107 	     list to be doubly linked, which would waste more memory, or
    108 	     require a traversal.  When an undefined or common symbol is
    109 	     created, it should be added to this list, the head of which is in
    110 	     the link hash table itself.  As symbols are defined, they need
    111 	     not be removed from the list; anything which reads the list must
    112 	     doublecheck the symbol type.
    113 
    114 	     Weak symbols are not kept on this list.
    115 
    116 	     Defined and defweak symbols use this field as a reference marker.
    117 	     If the field is not NULL, or this structure is the tail of the
    118 	     undefined symbol list, the symbol has been referenced.  If the
    119 	     symbol is undefined and becomes defined, this field will
    120 	     automatically be non-NULL since the symbol will have been on the
    121 	     undefined symbol list.  */
    122 	  struct bfd_link_hash_entry *next;
    123 	  bfd *abfd;		/* BFD symbol was found in.  */
    124 	  bfd *weak;		/* BFD weak symbol was found in.  */
    125 	} undef;
    126       /* bfd_link_hash_defined, bfd_link_hash_defweak.  */
    127       struct
    128 	{
    129 	  struct bfd_link_hash_entry *next;
    130 	  asection *section;	/* Symbol section.  */
    131 	  bfd_vma value;	/* Symbol value.  */
    132 	} def;
    133       /* bfd_link_hash_indirect, bfd_link_hash_warning.  */
    134       struct
    135 	{
    136 	  struct bfd_link_hash_entry *next;
    137 	  struct bfd_link_hash_entry *link;	/* Real symbol.  */
    138 	  const char *warning;	/* Warning (bfd_link_hash_warning only).  */
    139 	} i;
    140       /* bfd_link_hash_common.  */
    141       struct
    142 	{
    143 	  struct bfd_link_hash_entry *next;
    144 	  /* The linker needs to know three things about common
    145 	     symbols: the size, the alignment, and the section in
    146 	     which the symbol should be placed.  We store the size
    147 	     here, and we allocate a small structure to hold the
    148 	     section and the alignment.  The alignment is stored as a
    149 	     power of two.  We don't store all the information
    150 	     directly because we don't want to increase the size of
    151 	     the union; this structure is a major space user in the
    152 	     linker.  */
    153 	  struct bfd_link_hash_common_entry *p;
    154 	  bfd_size_type size;	/* Common symbol size.  */
    155 	} c;
    156     } u;
    157 };
    158 
    159 /* This is the link hash table.  It is a derived class of
    160    bfd_hash_table.  */
    161 
    162 struct bfd_link_hash_table
    163 {
    164   /* The hash table itself.  */
    165   struct bfd_hash_table table;
    166   /* A linked list of undefined and common symbols, linked through the
    167      next field in the bfd_link_hash_entry structure.  */
    168   struct bfd_link_hash_entry *undefs;
    169   /* Entries are added to the tail of the undefs list.  */
    170   struct bfd_link_hash_entry *undefs_tail;
    171   /* The type of the link hash table.  */
    172   enum bfd_link_hash_table_type type;
    173 };
    174 
    175 /* Look up an entry in a link hash table.  If FOLLOW is TRUE, this
    176    follows bfd_link_hash_indirect and bfd_link_hash_warning links to
    177    the real symbol.  */
    178 extern struct bfd_link_hash_entry *bfd_link_hash_lookup
    179   (struct bfd_link_hash_table *, const char *, bfd_boolean create,
    180    bfd_boolean copy, bfd_boolean follow);
    181 
    182 /* Look up an entry in the main linker hash table if the symbol might
    183    be wrapped.  This should only be used for references to an
    184    undefined symbol, not for definitions of a symbol.  */
    185 
    186 extern struct bfd_link_hash_entry *bfd_wrapped_link_hash_lookup
    187   (bfd *, struct bfd_link_info *, const char *, bfd_boolean,
    188    bfd_boolean, bfd_boolean);
    189 
    190 /* Traverse a link hash table.  */
    191 extern void bfd_link_hash_traverse
    192   (struct bfd_link_hash_table *,
    193     bfd_boolean (*) (struct bfd_link_hash_entry *, void *),
    194     void *);
    195 
    196 /* Add an entry to the undefs list.  */
    197 extern void bfd_link_add_undef
    198   (struct bfd_link_hash_table *, struct bfd_link_hash_entry *);
    199 
    200 /* Remove symbols from the undefs list that don't belong there.  */
    201 extern void bfd_link_repair_undef_list
    202   (struct bfd_link_hash_table *table);
    203 
    204 /* Read symbols and cache symbol pointer array in outsymbols.  */
    205 extern bfd_boolean bfd_generic_link_read_symbols (bfd *);
    206 
    207 struct bfd_sym_chain
    208 {
    209   struct bfd_sym_chain *next;
    210   const char *name;
    211 };
    212 
    213 /* How to handle unresolved symbols.
    215    There are four possibilities which are enumerated below:  */
    216 enum report_method
    217 {
    218   /* This is the initial value when then link_info structure is created.
    219      It allows the various stages of the linker to determine whether they
    220      allowed to set the value.  */
    221   RM_NOT_YET_SET = 0,
    222   RM_IGNORE,
    223   RM_GENERATE_WARNING,
    224   RM_GENERATE_ERROR
    225 };
    226 
    227 struct bfd_elf_dynamic_list;
    228 
    229 /* This structure holds all the information needed to communicate
    230    between BFD and the linker when doing a link.  */
    231 
    232 struct bfd_link_info
    233 {
    234   /* TRUE if BFD should generate a relocatable object file.  */
    235   unsigned int relocatable: 1;
    236 
    237   /* TRUE if BFD should generate relocation information in the final
    238      executable.  */
    239   unsigned int emitrelocations: 1;
    240 
    241   /* TRUE if BFD should generate a "task linked" object file,
    242      similar to relocatable but also with globals converted to
    243      statics.  */
    244   unsigned int task_link: 1;
    245 
    246   /* TRUE if BFD should generate a shared object.  */
    247   unsigned int shared: 1;
    248 
    249   /* TRUE if BFD should pre-bind symbols in a shared object.  */
    250   unsigned int symbolic: 1;
    251 
    252   /* TRUE if BFD should export all symbols in the dynamic symbol table
    253      of an executable, rather than only those used.  */
    254   unsigned int export_dynamic: 1;
    255 
    256   /* TRUE if shared objects should be linked directly, not shared.  */
    257   unsigned int static_link: 1;
    258 
    259   /* TRUE if the output file should be in a traditional format.  This
    260      is equivalent to the setting of the BFD_TRADITIONAL_FORMAT flag
    261      on the output file, but may be checked when reading the input
    262      files.  */
    263   unsigned int traditional_format: 1;
    264 
    265   /* TRUE if we want to produced optimized output files.  This might
    266      need much more time and therefore must be explicitly selected.  */
    267   unsigned int optimize: 1;
    268 
    269   /* TRUE if ok to have multiple definition.  */
    270   unsigned int allow_multiple_definition: 1;
    271 
    272   /* TRUE if ok to have version with no definition.  */
    273   unsigned int allow_undefined_version: 1;
    274 
    275   /* TRUE if a default symbol version should be created and used for
    276      exported symbols.  */
    277   unsigned int create_default_symver: 1;
    278 
    279   /* TRUE if a default symbol version should be created and used for
    280      imported symbols.  */
    281   unsigned int default_imported_symver: 1;
    282 
    283   /* TRUE if symbols should be retained in memory, FALSE if they
    284      should be freed and reread.  */
    285   unsigned int keep_memory: 1;
    286 
    287   /* TRUE if every symbol should be reported back via the notice
    288      callback.  */
    289   unsigned int notice_all: 1;
    290 
    291   /* TRUE if executable should not contain copy relocs.
    292      Setting this true may result in a non-sharable text segment.  */
    293   unsigned int nocopyreloc: 1;
    294 
    295   /* TRUE if the new ELF dynamic tags are enabled. */
    296   unsigned int new_dtags: 1;
    297 
    298   /* TRUE if non-PLT relocs should be merged into one reloc section
    299      and sorted so that relocs against the same symbol come together.  */
    300   unsigned int combreloc: 1;
    301 
    302   /* TRUE if .eh_frame_hdr section and PT_GNU_EH_FRAME ELF segment
    303      should be created.  */
    304   unsigned int eh_frame_hdr: 1;
    305 
    306   /* TRUE if global symbols in discarded sections should be stripped.  */
    307   unsigned int strip_discarded: 1;
    308 
    309   /* TRUE if generating a position independent executable.  */
    310   unsigned int pie: 1;
    311 
    312   /* TRUE if generating an executable, position independent or not.  */
    313   unsigned int executable : 1;
    314 
    315   /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W|PF_X
    316      flags.  */
    317   unsigned int execstack: 1;
    318 
    319   /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W
    320      flags.  */
    321   unsigned int noexecstack: 1;
    322 
    323   /* TRUE if PT_GNU_RELRO segment should be created.  */
    324   unsigned int relro: 1;
    325 
    326   /* TRUE if we should warn when adding a DT_TEXTREL to a shared object.  */
    327   unsigned int warn_shared_textrel: 1;
    328 
    329   /* TRUE if we should warn alternate ELF machine code.  */
    330   unsigned int warn_alternate_em: 1;
    331 
    332   /* TRUE if unreferenced sections should be removed.  */
    333   unsigned int gc_sections: 1;
    334 
    335   /* TRUE if user shoudl be informed of removed unreferenced sections.  */
    336   unsigned int print_gc_sections: 1;
    337 
    338   /* TRUE if .hash section should be created.  */
    339   unsigned int emit_hash: 1;
    340 
    341   /* TRUE if .gnu.hash section should be created.  */
    342   unsigned int emit_gnu_hash: 1;
    343 
    344   /* If TRUE reduce memory overheads, at the expense of speed. This will
    345      cause map file generation to use an O(N^2) algorithm and disable
    346      caching ELF symbol buffer.  */
    347   unsigned int reduce_memory_overheads: 1;
    348 
    349   /* TRUE if all data symbols should be dynamic.  */
    350    unsigned int dynamic_data: 1;
    351 
    352   /* TRUE if some symbols have to be dynamic, controlled by
    353      --dynamic-list command line options.  */
    354   unsigned int dynamic: 1;
    355 
    356   /* Non-NULL if .note.gnu.build-id section should be created.  */
    357   char *emit_note_gnu_build_id;
    358 
    359   /* What to do with unresolved symbols in an object file.
    360      When producing executables the default is GENERATE_ERROR.
    361      When producing shared libraries the default is IGNORE.  The
    362      assumption with shared libraries is that the reference will be
    363      resolved at load/execution time.  */
    364   enum report_method unresolved_syms_in_objects;
    365 
    366   /* What to do with unresolved symbols in a shared library.
    367      The same defaults apply.  */
    368   enum report_method unresolved_syms_in_shared_libs;
    369 
    370   /* Which symbols to strip.  */
    371   enum bfd_link_strip strip;
    372 
    373   /* Which local symbols to discard.  */
    374   enum bfd_link_discard discard;
    375 
    376   /* Criteria for skipping symbols when determining
    377      whether to include an object from an archive. */
    378   enum bfd_link_common_skip_ar_symbols common_skip_ar_symbols;
    379 
    380   /* Char that may appear as the first char of a symbol, but should be
    381      skipped (like symbol_leading_char) when looking up symbols in
    382      wrap_hash.  Used by PowerPC Linux for 'dot' symbols.  */
    383   char wrap_char;
    384 
    385   /* Separator between archive and filename in linker script filespecs.  */
    386   char path_separator;
    387 
    388   /* Function callbacks.  */
    389   const struct bfd_link_callbacks *callbacks;
    390 
    391   /* Hash table handled by BFD.  */
    392   struct bfd_link_hash_table *hash;
    393 
    394   /* Hash table of symbols to keep.  This is NULL unless strip is
    395      strip_some.  */
    396   struct bfd_hash_table *keep_hash;
    397 
    398   /* Hash table of symbols to report back via the notice callback.  If
    399      this is NULL, and notice_all is FALSE, then no symbols are
    400      reported back.  */
    401   struct bfd_hash_table *notice_hash;
    402 
    403   /* Hash table of symbols which are being wrapped (the --wrap linker
    404      option).  If this is NULL, no symbols are being wrapped.  */
    405   struct bfd_hash_table *wrap_hash;
    406 
    407   /* The output BFD.  */
    408   bfd *output_bfd;
    409 
    410   /* The list of input BFD's involved in the link.  These are chained
    411      together via the link_next field.  */
    412   bfd *input_bfds;
    413   bfd **input_bfds_tail;
    414 
    415   /* If a symbol should be created for each input BFD, this is section
    416      where those symbols should be placed.  It must be a section in
    417      the output BFD.  It may be NULL, in which case no such symbols
    418      will be created.  This is to support CREATE_OBJECT_SYMBOLS in the
    419      linker command language.  */
    420   asection *create_object_symbols_section;
    421 
    422   /* List of global symbol names that are starting points for marking
    423      sections against garbage collection.  */
    424   struct bfd_sym_chain *gc_sym_list;
    425 
    426   /* If a base output file is wanted, then this points to it */
    427   void *base_file;
    428 
    429   /* The function to call when the executable or shared object is
    430      loaded.  */
    431   const char *init_function;
    432 
    433   /* The function to call when the executable or shared object is
    434      unloaded.  */
    435   const char *fini_function;
    436 
    437   /* Number of relaxation passes.  Usually only one relaxation pass
    438      is needed.  But a backend can have as many relaxation passes as
    439      necessary.  During bfd_relax_section call, it is set to the
    440      current pass, starting from 0.  */
    441   int relax_pass;
    442 
    443   /* Number of relaxation trips.  This number is incremented every
    444      time the relaxation pass is restarted due to a previous
    445      relaxation returning true in *AGAIN.  */
    446   int relax_trip;
    447 
    448   /* Non-zero if auto-import thunks for DATA items in pei386 DLLs
    449      should be generated/linked against.  Set to 1 if this feature
    450      is explicitly requested by the user, -1 if enabled by default.  */
    451   int pei386_auto_import;
    452 
    453   /* Non-zero if runtime relocs for DATA items with non-zero addends
    454      in pei386 DLLs should be generated.  Set to 1 if this feature
    455      is explicitly requested by the user, -1 if enabled by default.  */
    456   int pei386_runtime_pseudo_reloc;
    457 
    458   /* How many spare .dynamic DT_NULL entries should be added?  */
    459   unsigned int spare_dynamic_tags;
    460 
    461   /* May be used to set DT_FLAGS for ELF. */
    462   bfd_vma flags;
    463 
    464   /* May be used to set DT_FLAGS_1 for ELF. */
    465   bfd_vma flags_1;
    466 
    467   /* Start and end of RELRO region.  */
    468   bfd_vma relro_start, relro_end;
    469 
    470   /* List of symbols should be dynamic.  */
    471   struct bfd_elf_dynamic_list *dynamic_list;
    472 };
    473 
    474 /* This structures holds a set of callback functions.  These are called
    475    by the BFD linker routines.  Except for the info functions, the first
    476    argument to each callback function is the bfd_link_info structure
    477    being used and each function returns a boolean value.  If the
    478    function returns FALSE, then the BFD function which called it should
    479    return with a failure indication.  */
    480 
    481 struct bfd_link_callbacks
    482 {
    483   /* A function which is called when an object is added from an
    484      archive.  ABFD is the archive element being added.  NAME is the
    485      name of the symbol which caused the archive element to be pulled
    486      in.  This function may set *SUBSBFD to point to an alternative
    487      BFD from which symbols should in fact be added in place of the
    488      original BFD's symbols.  */
    489   bfd_boolean (*add_archive_element)
    490     (struct bfd_link_info *, bfd *abfd, const char *name, bfd **subsbfd);
    491   /* A function which is called when a symbol is found with multiple
    492      definitions.  NAME is the symbol which is defined multiple times.
    493      OBFD is the old BFD, OSEC is the old section, OVAL is the old
    494      value, NBFD is the new BFD, NSEC is the new section, and NVAL is
    495      the new value.  OBFD may be NULL.  OSEC and NSEC may be
    496      bfd_com_section or bfd_ind_section.  */
    497   bfd_boolean (*multiple_definition)
    498     (struct bfd_link_info *, const char *name,
    499      bfd *obfd, asection *osec, bfd_vma oval,
    500      bfd *nbfd, asection *nsec, bfd_vma nval);
    501   /* A function which is called when a common symbol is defined
    502      multiple times.  NAME is the symbol appearing multiple times.
    503      OBFD is the BFD of the existing symbol; it may be NULL if this is
    504      not known.  OTYPE is the type of the existing symbol, which may
    505      be bfd_link_hash_defined, bfd_link_hash_defweak,
    506      bfd_link_hash_common, or bfd_link_hash_indirect.  If OTYPE is
    507      bfd_link_hash_common, OSIZE is the size of the existing symbol.
    508      NBFD is the BFD of the new symbol.  NTYPE is the type of the new
    509      symbol, one of bfd_link_hash_defined, bfd_link_hash_common, or
    510      bfd_link_hash_indirect.  If NTYPE is bfd_link_hash_common, NSIZE
    511      is the size of the new symbol.  */
    512   bfd_boolean (*multiple_common)
    513     (struct bfd_link_info *, const char *name,
    514      bfd *obfd, enum bfd_link_hash_type otype, bfd_vma osize,
    515      bfd *nbfd, enum bfd_link_hash_type ntype, bfd_vma nsize);
    516   /* A function which is called to add a symbol to a set.  ENTRY is
    517      the link hash table entry for the set itself (e.g.,
    518      __CTOR_LIST__).  RELOC is the relocation to use for an entry in
    519      the set when generating a relocatable file, and is also used to
    520      get the size of the entry when generating an executable file.
    521      ABFD, SEC and VALUE identify the value to add to the set.  */
    522   bfd_boolean (*add_to_set)
    523     (struct bfd_link_info *, struct bfd_link_hash_entry *entry,
    524      bfd_reloc_code_real_type reloc, bfd *abfd, asection *sec, bfd_vma value);
    525   /* A function which is called when the name of a g++ constructor or
    526      destructor is found.  This is only called by some object file
    527      formats.  CONSTRUCTOR is TRUE for a constructor, FALSE for a
    528      destructor.  This will use BFD_RELOC_CTOR when generating a
    529      relocatable file.  NAME is the name of the symbol found.  ABFD,
    530      SECTION and VALUE are the value of the symbol.  */
    531   bfd_boolean (*constructor)
    532     (struct bfd_link_info *, bfd_boolean constructor, const char *name,
    533      bfd *abfd, asection *sec, bfd_vma value);
    534   /* A function which is called to issue a linker warning.  For
    535      example, this is called when there is a reference to a warning
    536      symbol.  WARNING is the warning to be issued.  SYMBOL is the name
    537      of the symbol which triggered the warning; it may be NULL if
    538      there is none.  ABFD, SECTION and ADDRESS identify the location
    539      which trigerred the warning; either ABFD or SECTION or both may
    540      be NULL if the location is not known.  */
    541   bfd_boolean (*warning)
    542     (struct bfd_link_info *, const char *warning, const char *symbol,
    543      bfd *abfd, asection *section, bfd_vma address);
    544   /* A function which is called when a relocation is attempted against
    545      an undefined symbol.  NAME is the symbol which is undefined.
    546      ABFD, SECTION and ADDRESS identify the location from which the
    547      reference is made. IS_FATAL indicates whether an undefined symbol is
    548      a fatal error or not. In some cases SECTION may be NULL.  */
    549   bfd_boolean (*undefined_symbol)
    550     (struct bfd_link_info *, const char *name, bfd *abfd,
    551      asection *section, bfd_vma address, bfd_boolean is_fatal);
    552   /* A function which is called when a reloc overflow occurs. ENTRY is
    553      the link hash table entry for the symbol the reloc is against.
    554      NAME is the name of the local symbol or section the reloc is
    555      against, RELOC_NAME is the name of the relocation, and ADDEND is
    556      any addend that is used.  ABFD, SECTION and ADDRESS identify the
    557      location at which the overflow occurs; if this is the result of a
    558      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
    559      ABFD will be NULL.  */
    560   bfd_boolean (*reloc_overflow)
    561     (struct bfd_link_info *, struct bfd_link_hash_entry *entry,
    562      const char *name, const char *reloc_name, bfd_vma addend,
    563      bfd *abfd, asection *section, bfd_vma address);
    564   /* A function which is called when a dangerous reloc is performed.
    565      MESSAGE is an appropriate message.
    566      ABFD, SECTION and ADDRESS identify the location at which the
    567      problem occurred; if this is the result of a
    568      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
    569      ABFD will be NULL.  */
    570   bfd_boolean (*reloc_dangerous)
    571     (struct bfd_link_info *, const char *message,
    572      bfd *abfd, asection *section, bfd_vma address);
    573   /* A function which is called when a reloc is found to be attached
    574      to a symbol which is not being written out.  NAME is the name of
    575      the symbol.  ABFD, SECTION and ADDRESS identify the location of
    576      the reloc; if this is the result of a
    577      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
    578      ABFD will be NULL.  */
    579   bfd_boolean (*unattached_reloc)
    580     (struct bfd_link_info *, const char *name,
    581      bfd *abfd, asection *section, bfd_vma address);
    582   /* A function which is called when a symbol in notice_hash is
    583      defined or referenced.  NAME is the symbol.  ABFD, SECTION and
    584      ADDRESS are the value of the symbol.  If SECTION is
    585      bfd_und_section, this is a reference.  */
    586   bfd_boolean (*notice)
    587     (struct bfd_link_info *, const char *name,
    588      bfd *abfd, asection *section, bfd_vma address);
    589   /* Error or warning link info message.  */
    590   void (*einfo)
    591     (const char *fmt, ...);
    592   /* General link info message.  */
    593   void (*info)
    594     (const char *fmt, ...);
    595   /* Message to be printed in linker map file.  */
    596   void (*minfo)
    597     (const char *fmt, ...);
    598   /* This callback provides a chance for users of the BFD library to
    599      override its decision about whether to place two adjacent sections
    600      into the same segment.  */
    601   bfd_boolean (*override_segment_assignment)
    602     (struct bfd_link_info *, bfd * abfd,
    603      asection * current_section, asection * previous_section,
    604      bfd_boolean new_segment);
    605 };
    606 
    607 /* The linker builds link_order structures which tell the code how to
    609    include input data in the output file.  */
    610 
    611 /* These are the types of link_order structures.  */
    612 
    613 enum bfd_link_order_type
    614 {
    615   bfd_undefined_link_order,	/* Undefined.  */
    616   bfd_indirect_link_order,	/* Built from a section.  */
    617   bfd_data_link_order,		/* Set to explicit data.  */
    618   bfd_section_reloc_link_order,	/* Relocate against a section.  */
    619   bfd_symbol_reloc_link_order	/* Relocate against a symbol.  */
    620 };
    621 
    622 /* This is the link_order structure itself.  These form a chain
    623    attached to the output section whose contents they are describing.  */
    624 
    625 struct bfd_link_order
    626 {
    627   /* Next link_order in chain.  */
    628   struct bfd_link_order *next;
    629   /* Type of link_order.  */
    630   enum bfd_link_order_type type;
    631   /* Offset within output section.  */
    632   bfd_vma offset;
    633   /* Size within output section.  */
    634   bfd_size_type size;
    635   /* Type specific information.  */
    636   union
    637     {
    638       struct
    639 	{
    640 	  /* Section to include.  If this is used, then
    641 	     section->output_section must be the section the
    642 	     link_order is attached to, section->output_offset must
    643 	     equal the link_order offset field, and section->size
    644 	     must equal the link_order size field.  Maybe these
    645 	     restrictions should be relaxed someday.  */
    646 	  asection *section;
    647 	} indirect;
    648       struct
    649 	{
    650 	  /* Size of contents, or zero when contents size == size
    651 	     within output section.
    652 	     A non-zero value allows filling of the output section
    653 	     with an arbitrary repeated pattern.  */
    654 	  unsigned int size;
    655 	  /* Data to put into file.  */
    656 	  bfd_byte *contents;
    657 	} data;
    658       struct
    659 	{
    660 	  /* Description of reloc to generate.  Used for
    661 	     bfd_section_reloc_link_order and
    662 	     bfd_symbol_reloc_link_order.  */
    663 	  struct bfd_link_order_reloc *p;
    664 	} reloc;
    665     } u;
    666 };
    667 
    668 /* A linker order of type bfd_section_reloc_link_order or
    669    bfd_symbol_reloc_link_order means to create a reloc against a
    670    section or symbol, respectively.  This is used to implement -Ur to
    671    generate relocs for the constructor tables.  The
    672    bfd_link_order_reloc structure describes the reloc that BFD should
    673    create.  It is similar to a arelent, but I didn't use arelent
    674    because the linker does not know anything about most symbols, and
    675    any asymbol structure it creates will be partially meaningless.
    676    This information could logically be in the bfd_link_order struct,
    677    but I didn't want to waste the space since these types of relocs
    678    are relatively rare.  */
    679 
    680 struct bfd_link_order_reloc
    681 {
    682   /* Reloc type.  */
    683   bfd_reloc_code_real_type reloc;
    684 
    685   union
    686     {
    687       /* For type bfd_section_reloc_link_order, this is the section
    688 	 the reloc should be against.  This must be a section in the
    689 	 output BFD, not any of the input BFDs.  */
    690       asection *section;
    691       /* For type bfd_symbol_reloc_link_order, this is the name of the
    692 	 symbol the reloc should be against.  */
    693       const char *name;
    694     } u;
    695 
    696   /* Addend to use.  The object file should contain zero.  The BFD
    697      backend is responsible for filling in the contents of the object
    698      file correctly.  For some object file formats (e.g., COFF) the
    699      addend must be stored into in the object file, and for some
    700      (e.g., SPARC a.out) it is kept in the reloc.  */
    701   bfd_vma addend;
    702 };
    703 
    704 /* Allocate a new link_order for a section.  */
    705 extern struct bfd_link_order *bfd_new_link_order (bfd *, asection *);
    706 
    707 /* These structures are used to describe version information for the
    708    ELF linker.  These structures could be manipulated entirely inside
    709    BFD, but it would be a pain.  Instead, the regular linker sets up
    710    these structures, and then passes them into BFD.  */
    711 
    712 /* Glob pattern for a version.  */
    713 
    714 struct bfd_elf_version_expr
    715 {
    716   /* Next glob pattern for this version.  */
    717   struct bfd_elf_version_expr *next;
    718   /* Glob pattern.  */
    719   const char *pattern;
    720   /* Set if pattern is not a glob.  */
    721   unsigned int literal : 1;
    722   /* Defined by ".symver".  */
    723   unsigned int symver : 1;
    724   /* Defined by version script.  */
    725   unsigned int script : 1;
    726   /* Pattern type.  */
    727 #define BFD_ELF_VERSION_C_TYPE		1
    728 #define BFD_ELF_VERSION_CXX_TYPE	2
    729 #define BFD_ELF_VERSION_JAVA_TYPE	4
    730   unsigned int mask : 3;
    731 };
    732 
    733 struct bfd_elf_version_expr_head
    734 {
    735   /* List of all patterns, both wildcards and non-wildcards.  */
    736   struct bfd_elf_version_expr *list;
    737   /* Hash table for non-wildcards.  */
    738   void *htab;
    739   /* Remaining patterns.  */
    740   struct bfd_elf_version_expr *remaining;
    741   /* What kind of pattern types are present in list (bitmask).  */
    742   unsigned int mask;
    743 };
    744 
    745 /* Version dependencies.  */
    746 
    747 struct bfd_elf_version_deps
    748 {
    749   /* Next dependency for this version.  */
    750   struct bfd_elf_version_deps *next;
    751   /* The version which this version depends upon.  */
    752   struct bfd_elf_version_tree *version_needed;
    753 };
    754 
    755 /* A node in the version tree.  */
    756 
    757 struct bfd_elf_version_tree
    758 {
    759   /* Next version.  */
    760   struct bfd_elf_version_tree *next;
    761   /* Name of this version.  */
    762   const char *name;
    763   /* Version number.  */
    764   unsigned int vernum;
    765   /* Regular expressions for global symbols in this version.  */
    766   struct bfd_elf_version_expr_head globals;
    767   /* Regular expressions for local symbols in this version.  */
    768   struct bfd_elf_version_expr_head locals;
    769   /* List of versions which this version depends upon.  */
    770   struct bfd_elf_version_deps *deps;
    771   /* Index of the version name.  This is used within BFD.  */
    772   unsigned int name_indx;
    773   /* Whether this version tree was used.  This is used within BFD.  */
    774   int used;
    775   /* Matching hook.  */
    776   struct bfd_elf_version_expr *(*match)
    777     (struct bfd_elf_version_expr_head *head,
    778      struct bfd_elf_version_expr *prev, const char *sym);
    779 };
    780 
    781 struct bfd_elf_dynamic_list
    782 {
    783   struct bfd_elf_version_expr_head head;
    784   struct bfd_elf_version_expr *(*match)
    785     (struct bfd_elf_version_expr_head *head,
    786      struct bfd_elf_version_expr *prev, const char *sym);
    787 };
    788 
    789 #endif
    790