include/bfdlink.h

   1 /* bfdlink.h -- header file for BFD link routines
   2    Copyright 1993 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., 675 Mass Ave, Cambridge, MA 02139, 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 locals with a certain prefix.  */
  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_weak,           /* Symbol is weak and undefined.  */
  50   bfd_link_hash_defined,        /* Symbol is defined.  */
  51   bfd_link_hash_common,         /* Symbol is common.  */
  52   bfd_link_hash_indirect,       /* Symbol is an indirect link.  */
  53   bfd_link_hash_warning         /* Like indirect, but warn if referenced.  */
  54 };
  55
  56 /* The linking routines use a hash table which uses this structure for
  57    its elements.  */
  58
  59 struct bfd_link_hash_entry
  60 {
  61   /* Base hash table entry structure.  */
  62   struct bfd_hash_entry root;
  63   /* Type of this entry.  */
  64   enum bfd_link_hash_type type;
  65
  66   /* Undefined and common symbols are kept in a linked list through
  67      this field.  This field is not in the union because that would
  68      force us to remove entries from the list when we changed their
  69      type, which would force the list to be doubly linked, which would
  70      waste more memory.  When an undefined or common symbol is
  71      created, it should be added to this list, the head of which is in
  72      the link hash table itself.  As symbols are defined, they need
  73      not be removed from the list; anything which reads the list must
  74      doublecheck the symbol type.
  75
  76      Weak symbols are not kept on this list.
  77
  78      Defined symbols use this field as a reference marker.  If the
  79      field is not NULL, or this structure is the tail of the undefined
  80      symbol list, the symbol has been referenced.  If the symbol is
  81      undefined and becomes defined, this field will automatically be
  82      non-NULL since the symbol will have been on the undefined symbol
  83      list.  */
  84   struct bfd_link_hash_entry *next;
  85   /* A union of information depending upon the type.  */
  86   union
  87     {
  88       /* Nothing is kept for bfd_hash_new.  */
  89       /* bfd_link_hash_undefined, bfd_link_hash_weak.  */
  90       struct
  91         {
  92           bfd *abfd;            /* BFD symbol was found in.  */
  93         } undef;
  94       /* bfd_link_hash_defined.  */
  95       struct
  96         {
  97           bfd_vma value;        /* Symbol value.  */
  98           asection *section;    /* Symbol section.  */
  99         } def;
 100       /* bfd_link_hash_indirect, bfd_link_hash_warning.  */
 101       struct
 102         {
 103           struct bfd_link_hash_entry *link;     /* Real symbol.  */
 104           const char *warning;  /* Warning (bfd_link_hash_warning only).  */
 105         } i;
 106       /* bfd_link_hash_common.  */
 107       struct
 108         {
 109           bfd_vma size;         /* Common symbol size.  */
 110           asection *section;    /* Symbol section.  */
 111         } c;
 112     } u;
 113 };
 114
 115 /* This is the link hash table.  It is a derived class of
 116    bfd_hash_table.  */
 117
 118 struct bfd_link_hash_table
 119 {
 120   /* The hash table itself.  */
 121   struct bfd_hash_table table;
 122   /* The back end which created this hash table.  This indicates the
 123      type of the entries in the hash table, which is sometimes
 124      important information when linking object files of different
 125      types together.  */
 126   bfd_target *creator;
 127   /* A linked list of undefined and common symbols, linked through the
 128      next field in the bfd_link_hash_entry structure.  */
 129   struct bfd_link_hash_entry *undefs;
 130   /* Entries are added to the tail of the undefs list.  */
 131   struct bfd_link_hash_entry *undefs_tail;
 132 };
 133
 134 /* Look up an entry in a link hash table.  If FOLLOW is true, this
 135    follows bfd_link_hash_indirect and bfd_link_hash_warning links to
 136    the real symbol.  */
 137 extern struct bfd_link_hash_entry *bfd_link_hash_lookup
 138   PARAMS ((struct bfd_link_hash_table *, const char *, boolean create,
 139            boolean copy, boolean follow));
 140
 141 /* Traverse a link hash table.  */
 142 extern void bfd_link_hash_traverse
 143   PARAMS ((struct bfd_link_hash_table *,
 144            boolean (*) (struct bfd_link_hash_entry *, PTR),
 145            PTR));
 146
 147 /* Add an entry to the undefs list.  */
 148 extern void bfd_link_add_undef
 149   PARAMS ((struct bfd_link_hash_table *, struct bfd_link_hash_entry *));
 150 \f
 151 /* This structure holds all the information needed to communicate
 152    between BFD and the linker when doing a link.  */
 153
 154 struct bfd_link_info
 155 {
 156   /* Function callbacks.  */
 157   const struct bfd_link_callbacks *callbacks;
 158   /* true if BFD should generate a relocateable object file.  */
 159   boolean relocateable;
 160   /* true if BFD should generate a shared object.  */
 161   boolean shared;
 162   /* Which symbols to strip.  */
 163   enum bfd_link_strip strip;
 164   /* Which local symbols to discard.  */
 165   enum bfd_link_discard discard;
 166   /* The local symbol prefix to discard if using discard_l.  */
 167   unsigned int lprefix_len;
 168   const char *lprefix;
 169   /* true if symbols should be retained in memory, false if they
 170      should be freed and reread.  */
 171   boolean keep_memory;
 172   /* The list of input BFD's involved in the link.  These are chained
 173      together via the link_next field.  */
 174   bfd *input_bfds;
 175   /* If a symbol should be created for each input BFD, this is section
 176      where those symbols should be placed.  It must be a section in
 177      the output BFD.  It may be NULL, in which case no such symbols
 178      will be created.  This is to support CREATE_OBJECT_SYMBOLS in the
 179      linker command language.  */
 180   asection *create_object_symbols_section;
 181   /* Hash table handled by BFD.  */
 182   struct bfd_link_hash_table *hash;
 183   /* Hash table of symbols to keep.  This is NULL unless strip is
 184      strip_some.  */
 185   struct bfd_hash_table *keep_hash;
 186   /* Hash table of symbols to report back via notice_callback.  If
 187      this is NULL no symbols are reported back.  */
 188   struct bfd_hash_table *notice_hash;
 189 };
 190
 191 /* This structures holds a set of callback functions.  These are
 192    called by the BFD linker routines.  The first argument to each
 193    callback function is the bfd_link_info structure being used.  Each
 194    function returns a boolean value.  If the function returns false,
 195    then the BFD function which called it will return with a failure
 196    indication.  */
 197
 198 struct bfd_link_callbacks
 199 {
 200   /* A function which is called when an object is added from an
 201      archive.  ABFD is the archive element being added.  NAME is the
 202      name of the symbol which caused the archive element to be pulled
 203      in.  */
 204   boolean (*add_archive_element) PARAMS ((struct bfd_link_info *,
 205                                           bfd *abfd,
 206                                           const char *name));
 207   /* A function which is called when a symbol is found with multiple
 208      definitions.  NAME is the symbol which is defined multiple times.
 209      OBFD is the old BFD, OSEC is the old section, OVAL is the old
 210      value, NBFD is the new BFD, NSEC is the new section, and NVAL is
 211      the new value.  OBFD may be NULL.  OSEC and NSEC may be
 212      bfd_com_section or bfd_ind_section.  */
 213   boolean (*multiple_definition) PARAMS ((struct bfd_link_info *,
 214                                           const char *name,
 215                                           bfd *obfd,
 216                                           asection *osec,
 217                                           bfd_vma oval,
 218                                           bfd *nbfd,
 219                                           asection *nsec,
 220                                           bfd_vma nval));
 221   /* A function which is called when a common symbol is defined
 222      multiple times.  NAME is the symbol appearing multiple times.
 223      OBFD is the BFD of the existing symbol.  OTYPE is the type of the
 224      existing symbol, either bfd_link_hash_defined or
 225      bfd_link_hash_common.  If OTYPE is bfd_link_hash_common, OSIZE is
 226      the size of the existing symbol.  NBFD is the BFD of the new
 227      symbol.  NTYPE is the type of the new symbol, either
 228      bfd_link_hash_defined or bfd_link_hash_common.  If NTYPE is
 229      bfd_link_hash_common, NSIZE is the size of the new symbol.  */
 230   boolean (*multiple_common) PARAMS ((struct bfd_link_info *,
 231                                       const char *name,
 232                                       bfd *obfd,
 233                                       enum bfd_link_hash_type otype,
 234                                       bfd_vma osize,
 235                                       bfd *nbfd,
 236                                       enum bfd_link_hash_type ntype,
 237                                       bfd_vma nsize));
 238   /* A function which is called to add a symbol to a set.  ENTRY is
 239      the link hash table entry for the set itself (e.g.,
 240      __CTOR_LIST__).  RELOC is the relocation to use for an entry in
 241      the set when generating a relocateable file, and is also used to
 242      get the size of the entry when generating an executable file.
 243      ABFD, SEC and VALUE identify the value to add to the set.  */
 244   boolean (*add_to_set) PARAMS ((struct bfd_link_info *,
 245                                  struct bfd_link_hash_entry *entry,
 246                                  bfd_reloc_code_real_type reloc,
 247                                  bfd *abfd, asection *sec, bfd_vma value));
 248   /* A function which is called when the name of a g++ constructor or
 249      destructor is found.  This is only called by some object file
 250      formats.  CONSTRUCTOR is true for a constructor, false for a
 251      destructor.  This will use BFD_RELOC_CTOR when generating a
 252      relocateable file.  NAME is the name of the symbol found.  ABFD,
 253      SECTION and VALUE are the value of the symbol.  */
 254   boolean (*constructor) PARAMS ((struct bfd_link_info *,
 255                                   boolean constructor,
 256                                   const char *name, bfd *abfd, asection *sec,
 257                                   bfd_vma value));
 258   /* A function which is called when there is a reference to a warning
 259      symbol.  WARNING is the warning to be issued.  */
 260   boolean (*warning) PARAMS ((struct bfd_link_info *,
 261                               const char *warning));
 262   /* A function which is called when a relocation is attempted against
 263      an undefined symbol.  NAME is the symbol which is undefined.
 264      ABFD, SECTION and ADDRESS identify the location from which the
 265      reference is made.  */
 266   boolean (*undefined_symbol) PARAMS ((struct bfd_link_info *,
 267                                        const char *name, bfd *abfd,
 268                                        asection *section, bfd_vma address));
 269   /* A function which is called when a reloc overflow occurs.  NAME is
 270      the name of the symbol or section the reloc is against,
 271      RELOC_NAME is the name of the relocation, and ADDEND is any
 272      addend that is used.  ABFD, SECTION and ADDRESS identify the
 273      location at which the overflow occurs; if this is the result of a
 274      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 275      ABFD will be NULL.  */
 276   boolean (*reloc_overflow) PARAMS ((struct bfd_link_info *,
 277                                      const char *name,
 278                                      const char *reloc_name, bfd_vma addend,
 279                                      bfd *abfd, asection *section,
 280                                      bfd_vma address));
 281   /* A function which is called when a dangerous reloc is performed.
 282      The canonical example is an a29k IHCONST reloc which does not
 283      follow an IHIHALF reloc.  MESSAGE is an appropriate message.
 284      ABFD, SECTION and ADDRESS identify the location at which the
 285      problem occurred; if this is the result of a
 286      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 287      ABFD will be NULL.  */
 288   boolean (*reloc_dangerous) PARAMS ((struct bfd_link_info *,
 289                                       const char *message,
 290                                       bfd *abfd, asection *section,
 291                                       bfd_vma address));
 292   /* A function which is called when a reloc is found to be attached
 293      to a symbol which is not being written out.  NAME is the name of
 294      the symbol.  ABFD, SECTION and ADDRESS identify the location of
 295      the reloc; if this is the result of a
 296      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 297      ABFD will be NULL.  */
 298   boolean (*unattached_reloc) PARAMS ((struct bfd_link_info *,
 299                                        const char *name,
 300                                        bfd *abfd, asection *section,
 301                                        bfd_vma address));
 302   /* A function which is called when a symbol in notice_hash is
 303      defined or referenced.  NAME is the symbol.  ABFD, SECTION and
 304      ADDRESS are the value of the symbol.  If SECTION is
 305      bfd_und_section, this is a reference.  */
 306   boolean (*notice) PARAMS ((struct bfd_link_info *, const char *name,
 307                              bfd *abfd, asection *section, bfd_vma address));
 308 };
 309 \f
 310 /* The linker builds link_order structures which tell the code how to
 311    include input data in the output file.  */
 312
 313 /* These are the types of link_order structures.  */
 314
 315 enum bfd_link_order_type
 316 {
 317   bfd_undefined_link_order,     /* Undefined.  */
 318   bfd_indirect_link_order,      /* Built from a section.  */
 319   bfd_fill_link_order,          /* Fill with a 16 bit constant.  */
 320   bfd_data_link_order,          /* Set to explicit data.  */
 321   bfd_section_reloc_link_order, /* Relocate against a section.  */
 322   bfd_symbol_reloc_link_order   /* Relocate against a symbol.  */
 323 };
 324
 325 /* This is the link_order structure itself.  These form a chain
 326    attached to the section whose contents they are describing.  */
 327
 328 struct bfd_link_order
 329 {
 330   /* Next link_order in chain.  */
 331   struct bfd_link_order *next;
 332   /* Type of link_order.  */
 333   enum bfd_link_order_type type;
 334   /* Offset within output section.  */
 335   bfd_vma offset;
 336   /* Size within output section.  */
 337   bfd_size_type size;
 338   /* Type specific information.  */
 339   union
 340     {
 341       struct
 342         {
 343           /* Section to include.  If this is used, then
 344              section->output_section must be the section the
 345              link_order is attached to, section->output_offset must
 346              equal the link_order offset field, and section->_raw_size
 347              must equal the link_order size field.  Maybe these
 348              restrictions should be relaxed someday.  */
 349           asection *section;
 350         } indirect;
 351       struct
 352         {
 353           /* Value to fill with.  */
 354           unsigned int value;
 355         } fill;
 356       struct
 357         {
 358           /* Data to put into file.  The size field gives the number
 359              of bytes which this field points to.  */
 360           bfd_byte *contents;
 361         } data;
 362       struct
 363         {
 364           /* Description of reloc to generate.  Used for
 365              bfd_section_reloc_link_order and
 366              bfd_symbol_reloc_link_order.  */
 367           struct bfd_link_order_reloc *p;
 368         } reloc;
 369     } u;
 370 };
 371
 372 /* A linker order of type bfd_section_reloc_link_order or
 373    bfd_symbol_reloc_link_order means to create a reloc against a
 374    section or symbol, respectively.  This is used to implement -Ur to
 375    generate relocs for the constructor tables.  The
 376    bfd_link_order_reloc structure describes the reloc that BFD should
 377    create.  It is similar to a arelent, but I didn't use arelent
 378    because the linker does not know anything about most symbols, and
 379    any asymbol structure it creates will be partially meaningless.
 380    This information could logically be in the bfd_link_order struct,
 381    but I didn't want to waste the space since these types of relocs
 382    are relatively rare.  */
 383
 384 struct bfd_link_order_reloc
 385 {
 386   /* Reloc type.  */
 387   bfd_reloc_code_real_type reloc;
 388
 389   union
 390     {
 391       /* For type bfd_section_reloc_link_order, this is the section
 392          the reloc should be against.  This must be a section in the
 393          output BFD, not any of the input BFDs.  */
 394       asection *section;
 395       /* For type bfd_symbol_reloc_link_order, this is the name of the
 396          symbol the reloc should be against.  */
 397       const char *name;
 398     } u;
 399
 400   /* Addend to use.  The object file should contain zero.  The BFD
 401      backend is responsible for filling in the contents of the object
 402      file correctly.  For some object file formats (e.g., COFF) the
 403      addend must be stored into in the object file, and for some
 404      (e.g., SPARC a.out) it is kept in the reloc.  */
 405   bfd_vma addend;
 406 };
 407
 408 /* Allocate a new link_order for a section.  */
 409 extern struct bfd_link_order *bfd_new_link_order PARAMS ((bfd *, asection *));
 410
 411 #endif