bfd/section.c

   1 /* Object file "section" support for the BFD library.
   2    Copyright (C) 1990, 91, 92, 93, 94, 95, 96, 97, 98, 1999
   3    Free Software Foundation, Inc.
   4    Written by 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 2 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  21
  22 /*
  23 SECTION
  24         Sections
  25
  26         The raw data contained within a BFD is maintained through the
  27         section abstraction.  A single BFD may have any number of
  28         sections.  It keeps hold of them by pointing to the first;
  29         each one points to the next in the list.
  30
  31         Sections are supported in BFD in <<section.c>>.
  32
  33 @menu
  34 @* Section Input::
  35 @* Section Output::
  36 @* typedef asection::
  37 @* section prototypes::
  38 @end menu
  39
  40 INODE
  41 Section Input, Section Output, Sections, Sections
  42 SUBSECTION
  43         Section input
  44
  45         When a BFD is opened for reading, the section structures are
  46         created and attached to the BFD.
  47
  48         Each section has a name which describes the section in the
  49         outside world---for example, <<a.out>> would contain at least
  50         three sections, called <<.text>>, <<.data>> and <<.bss>>.
  51
  52         Names need not be unique; for example a COFF file may have several
  53         sections named <<.data>>.
  54
  55         Sometimes a BFD will contain more than the ``natural'' number of
  56         sections. A back end may attach other sections containing
  57         constructor data, or an application may add a section (using
  58         <<bfd_make_section>>) to the sections attached to an already open
  59         BFD. For example, the linker creates an extra section
  60         <<COMMON>> for each input file's BFD to hold information about
  61         common storage.
  62
  63         The raw data is not necessarily read in when
  64         the section descriptor is created. Some targets may leave the
  65         data in place until a <<bfd_get_section_contents>> call is
  66         made. Other back ends may read in all the data at once.  For
  67         example, an S-record file has to be read once to determine the
  68         size of the data. An IEEE-695 file doesn't contain raw data in
  69         sections, but data and relocation expressions intermixed, so
  70         the data area has to be parsed to get out the data and
  71         relocations.
  72
  73 INODE
  74 Section Output, typedef asection, Section Input, Sections
  75
  76 SUBSECTION
  77         Section output
  78
  79         To write a new object style BFD, the various sections to be
  80         written have to be created. They are attached to the BFD in
  81         the same way as input sections; data is written to the
  82         sections using <<bfd_set_section_contents>>.
  83
  84         Any program that creates or combines sections (e.g., the assembler
  85         and linker) must use the <<asection>> fields <<output_section>> and
  86         <<output_offset>> to indicate the file sections to which each
  87         section must be written.  (If the section is being created from
  88         scratch, <<output_section>> should probably point to the section
  89         itself and <<output_offset>> should probably be zero.)
  90
  91         The data to be written comes from input sections attached
  92         (via <<output_section>> pointers) to
  93         the output sections.  The output section structure can be
  94         considered a filter for the input section: the output section
  95         determines the vma of the output data and the name, but the
  96         input section determines the offset into the output section of
  97         the data to be written.
  98
  99         E.g., to create a section "O", starting at 0x100, 0x123 long,
 100         containing two subsections, "A" at offset 0x0 (i.e., at vma
 101         0x100) and "B" at offset 0x20 (i.e., at vma 0x120) the <<asection>>
 102         structures would look like:
 103
 104 |   section name          "A"
 105 |     output_offset   0x00
 106 |     size            0x20
 107 |     output_section ----------->  section name    "O"
 108 |                             |    vma             0x100
 109 |   section name          "B" |    size            0x123
 110 |     output_offset   0x20    |
 111 |     size            0x103   |
 112 |     output_section  --------|
 113
 114
 115 SUBSECTION
 116         Link orders
 117
 118         The data within a section is stored in a @dfn{link_order}.
 119         These are much like the fixups in <<gas>>.  The link_order
 120         abstraction allows a section to grow and shrink within itself.
 121
 122         A link_order knows how big it is, and which is the next
 123         link_order and where the raw data for it is; it also points to
 124         a list of relocations which apply to it.
 125
 126         The link_order is used by the linker to perform relaxing on
 127         final code.  The compiler creates code which is as big as
 128         necessary to make it work without relaxing, and the user can
 129         select whether to relax.  Sometimes relaxing takes a lot of
 130         time.  The linker runs around the relocations to see if any
 131         are attached to data which can be shrunk, if so it does it on
 132         a link_order by link_order basis.
 133
 134 */
 135
 136
 137 #include "bfd.h"
 138 #include "sysdep.h"
 139 #include "libbfd.h"
 140 #include "bfdlink.h"
 141
 142 /*
 143 DOCDD
 144 INODE
 145 typedef asection, section prototypes, Section Output, Sections
 146 SUBSECTION
 147         typedef asection
 148
 149         Here is the section structure:
 150
 151 CODE_FRAGMENT
 152 .
 153 . {* This structure is used for a comdat section, as in PE.  A comdat
 154 .    section is associated with a particular symbol.  When the linker
 155 .    sees a comdat section, it keeps only one of the sections with a
 156 .    given name and associated with a given symbol. *}
 157 .
 158 .struct bfd_comdat_info
 159 .{
 160 .  {* The name of the symbol associated with a comdat section.  *}
 161 .  const char *name;
 162 .
 163 .  {* The local symbol table index of the symbol associated with a
 164 .     comdat section.  This is only meaningful to the object file format
 165 .     specific code; it is not an index into the list returned by
 166 .     bfd_canonicalize_symtab.  *}
 167 .  long symbol;
 168 .
 169 .  {* If this section is being discarded, the linker uses this field
 170 .     to point to the input section which is being kept.  *}
 171 .  struct sec *sec;
 172 .};
 173 .
 174 .typedef struct sec
 175 .{
 176 .        {* The name of the section; the name isn't a copy, the pointer is
 177 .        the same as that passed to bfd_make_section. *}
 178 .
 179 .    CONST char *name;
 180 .
 181 .        {* Which section is it; 0..nth.      *}
 182 .
 183 .   int index;
 184 .
 185 .        {* The next section in the list belonging to the BFD, or NULL. *}
 186 .
 187 .    struct sec *next;
 188 .
 189 .        {* The field flags contains attributes of the section. Some
 190 .           flags are read in from the object file, and some are
 191 .           synthesized from other information.  *}
 192 .
 193 .    flagword flags;
 194 .
 195 .#define SEC_NO_FLAGS   0x000
 196 .
 197 .        {* Tells the OS to allocate space for this section when loading.
 198 .           This is clear for a section containing debug information
 199 .           only. *}
 200 .#define SEC_ALLOC      0x001
 201 .
 202 .        {* Tells the OS to load the section from the file when loading.
 203 .           This is clear for a .bss section. *}
 204 .#define SEC_LOAD       0x002
 205 .
 206 .        {* The section contains data still to be relocated, so there is
 207 .           some relocation information too. *}
 208 .#define SEC_RELOC      0x004
 209 .
 210 .#if 0   {* Obsolete ? *}
 211 .#define SEC_BALIGN     0x008
 212 .#endif
 213 .
 214 .        {* A signal to the OS that the section contains read only
 215 .          data. *}
 216 .#define SEC_READONLY   0x010
 217 .
 218 .        {* The section contains code only. *}
 219 .#define SEC_CODE       0x020
 220 .
 221 .        {* The section contains data only. *}
 222 .#define SEC_DATA       0x040
 223 .
 224 .        {* The section will reside in ROM. *}
 225 .#define SEC_ROM        0x080
 226 .
 227 .        {* The section contains constructor information. This section
 228 .           type is used by the linker to create lists of constructors and
 229 .           destructors used by <<g++>>. When a back end sees a symbol
 230 .           which should be used in a constructor list, it creates a new
 231 .           section for the type of name (e.g., <<__CTOR_LIST__>>), attaches
 232 .           the symbol to it, and builds a relocation. To build the lists
 233 .           of constructors, all the linker has to do is catenate all the
 234 .           sections called <<__CTOR_LIST__>> and relocate the data
 235 .           contained within - exactly the operations it would peform on
 236 .           standard data. *}
 237 .#define SEC_CONSTRUCTOR 0x100
 238 .
 239 .        {* The section is a constructor, and should be placed at the
 240 .          end of the text, data, or bss section(?). *}
 241 .#define SEC_CONSTRUCTOR_TEXT 0x1100
 242 .#define SEC_CONSTRUCTOR_DATA 0x2100
 243 .#define SEC_CONSTRUCTOR_BSS  0x3100
 244 .
 245 .        {* The section has contents - a data section could be
 246 .           <<SEC_ALLOC>> | <<SEC_HAS_CONTENTS>>; a debug section could be
 247 .           <<SEC_HAS_CONTENTS>> *}
 248 .#define SEC_HAS_CONTENTS 0x200
 249 .
 250 .        {* An instruction to the linker to not output the section
 251 .           even if it has information which would normally be written. *}
 252 .#define SEC_NEVER_LOAD 0x400
 253 .
 254 .        {* The section is a COFF shared library section.  This flag is
 255 .           only for the linker.  If this type of section appears in
 256 .           the input file, the linker must copy it to the output file
 257 .           without changing the vma or size.  FIXME: Although this
 258 .           was originally intended to be general, it really is COFF
 259 .           specific (and the flag was renamed to indicate this).  It
 260 .           might be cleaner to have some more general mechanism to
 261 .           allow the back end to control what the linker does with
 262 .           sections. *}
 263 .#define SEC_COFF_SHARED_LIBRARY 0x800
 264 .
 265 .        {* The section contains common symbols (symbols may be defined
 266 .           multiple times, the value of a symbol is the amount of
 267 .           space it requires, and the largest symbol value is the one
 268 .           used).  Most targets have exactly one of these (which we
 269 .           translate to bfd_com_section_ptr), but ECOFF has two. *}
 270 .#define SEC_IS_COMMON 0x8000
 271 .
 272 .        {* The section contains only debugging information.  For
 273 .           example, this is set for ELF .debug and .stab sections.
 274 .           strip tests this flag to see if a section can be
 275 .           discarded. *}
 276 .#define SEC_DEBUGGING 0x10000
 277 .
 278 .        {* The contents of this section are held in memory pointed to
 279 .           by the contents field.  This is checked by
 280 .           bfd_get_section_contents, and the data is retrieved from
 281 .           memory if appropriate.  *}
 282 .#define SEC_IN_MEMORY 0x20000
 283 .
 284 .        {* The contents of this section are to be excluded by the
 285 .           linker for executable and shared objects unless those
 286 .           objects are to be further relocated.  *}
 287 .#define SEC_EXCLUDE 0x40000
 288 .
 289 .       {* The contents of this section are to be sorted by the
 290 .          based on the address specified in the associated symbol
 291 .          table.  *}
 292 .#define SEC_SORT_ENTRIES 0x80000
 293 .
 294 .       {* When linking, duplicate sections of the same name should be
 295 .          discarded, rather than being combined into a single section as
 296 .          is usually done.  This is similar to how common symbols are
 297 .          handled.  See SEC_LINK_DUPLICATES below.  *}
 298 .#define SEC_LINK_ONCE 0x100000
 299 .
 300 .       {* If SEC_LINK_ONCE is set, this bitfield describes how the linker
 301 .          should handle duplicate sections.  *}
 302 .#define SEC_LINK_DUPLICATES 0x600000
 303 .
 304 .       {* This value for SEC_LINK_DUPLICATES means that duplicate
 305 .          sections with the same name should simply be discarded. *}
 306 .#define SEC_LINK_DUPLICATES_DISCARD 0x0
 307 .
 308 .       {* This value for SEC_LINK_DUPLICATES means that the linker
 309 .          should warn if there are any duplicate sections, although
 310 .          it should still only link one copy.  *}
 311 .#define SEC_LINK_DUPLICATES_ONE_ONLY 0x200000
 312 .
 313 .       {* This value for SEC_LINK_DUPLICATES means that the linker
 314 .          should warn if any duplicate sections are a different size.  *}
 315 .#define SEC_LINK_DUPLICATES_SAME_SIZE 0x400000
 316 .
 317 .       {* This value for SEC_LINK_DUPLICATES means that the linker
 318 .          should warn if any duplicate sections contain different
 319 .          contents.  *}
 320 .#define SEC_LINK_DUPLICATES_SAME_CONTENTS 0x600000
 321 .
 322 .       {* This section was created by the linker as part of dynamic
 323 .          relocation or other arcane processing.  It is skipped when
 324 .          going through the first-pass output, trusting that someone
 325 .          else up the line will take care of it later.  *}
 326 .#define SEC_LINKER_CREATED 0x800000
 327 .
 328 .       {* This section should not be subject to garbage collection.  *}
 329 .#define SEC_KEEP 0x1000000
 330 .
 331 .       {* This section contains "short" data, and should be placed
 332 .          "near" the GP.  *}
 333 .#define SEC_SMALL_DATA 0x2000000
 334 .
 335 .       {* This section contains data which may be shared with other
 336 .          executables or shared objects.  *}
 337 .#define SEC_SHARED 0x4000000
 338 .
 339 .       {*  End of section flags.  *}
 340 .
 341 .       {* Some internal packed boolean fields.  *}
 342 .
 343 .       {* See the vma field.  *}
 344 .       unsigned int user_set_vma : 1;
 345 .
 346 .       {* Whether relocations have been processed.  *}
 347 .       unsigned int reloc_done : 1;
 348 .
 349 .       {* A mark flag used by some of the linker backends.  *}
 350 .       unsigned int linker_mark : 1;
 351 .
 352 .       {* A mark flag used by some linker backends for garbage collection.  *}
 353 .       unsigned int gc_mark : 1;
 354 .
 355 .       {* End of internal packed boolean fields.  *}
 356 .
 357 .       {*  The virtual memory address of the section - where it will be
 358 .           at run time.  The symbols are relocated against this.  The
 359 .           user_set_vma flag is maintained by bfd; if it's not set, the
 360 .           backend can assign addresses (for example, in <<a.out>>, where
 361 .           the default address for <<.data>> is dependent on the specific
 362 .           target and various flags).  *}
 363 .
 364 .   bfd_vma vma;
 365 .
 366 .       {*  The load address of the section - where it would be in a
 367 .           rom image; really only used for writing section header
 368 .           information. *}
 369 .
 370 .   bfd_vma lma;
 371 .
 372 .        {* The size of the section in octets, as it will be output.
 373 .           Contains a value even if the section has no contents (e.g., the
 374 .           size of <<.bss>>).  This will be filled in after relocation.  *}
 375 .
 376 .   bfd_size_type _cooked_size;
 377 .
 378 .        {* The original size on disk of the section, in octets.  Normally this
 379 .           value is the same as the size, but if some relaxing has
 380 .           been done, then this value will be bigger.  *}
 381 .
 382 .   bfd_size_type _raw_size;
 383 .
 384 .        {* If this section is going to be output, then this value is the
 385 .           offset in *bytes* into the output section of the first byte in the
 386 .           input section (byte ==> smallest addressable unit on the
 387 .           target).  In most cases, if this was going to start at the
 388 .           100th octet (8-bit quantity) in the output section, this value
 389 .           would be 100.  However, if the target byte size is 16 bits
 390 .           (bfd_octets_per_byte is "2"), this value would be 50. *}
 391 .
 392 .   bfd_vma output_offset;
 393 .
 394 .        {* The output section through which to map on output. *}
 395 .
 396 .   struct sec *output_section;
 397 .
 398 .        {* The alignment requirement of the section, as an exponent of 2 -
 399 .           e.g., 3 aligns to 2^3 (or 8). *}
 400 .
 401 .   unsigned int alignment_power;
 402 .
 403 .        {* If an input section, a pointer to a vector of relocation
 404 .           records for the data in this section. *}
 405 .
 406 .   struct reloc_cache_entry *relocation;
 407 .
 408 .        {* If an output section, a pointer to a vector of pointers to
 409 .           relocation records for the data in this section. *}
 410 .
 411 .   struct reloc_cache_entry **orelocation;
 412 .
 413 .        {* The number of relocation records in one of the above  *}
 414 .
 415 .   unsigned reloc_count;
 416 .
 417 .        {* Information below is back end specific - and not always used
 418 .           or updated.  *}
 419 .
 420 .        {* File position of section data    *}
 421 .
 422 .   file_ptr filepos;
 423 .
 424 .        {* File position of relocation info *}
 425 .
 426 .   file_ptr rel_filepos;
 427 .
 428 .        {* File position of line data       *}
 429 .
 430 .   file_ptr line_filepos;
 431 .
 432 .        {* Pointer to data for applications *}
 433 .
 434 .   PTR userdata;
 435 .
 436 .        {* If the SEC_IN_MEMORY flag is set, this points to the actual
 437 .           contents.  *}
 438 .   unsigned char *contents;
 439 .
 440 .        {* Attached line number information *}
 441 .
 442 .   alent *lineno;
 443 .
 444 .        {* Number of line number records   *}
 445 .
 446 .   unsigned int lineno_count;
 447 .
 448 .        {* Optional information about a COMDAT entry; NULL if not COMDAT *}
 449 .
 450 .   struct bfd_comdat_info *comdat;
 451 .
 452 .        {* When a section is being output, this value changes as more
 453 .           linenumbers are written out *}
 454 .
 455 .   file_ptr moving_line_filepos;
 456 .
 457 .        {* What the section number is in the target world  *}
 458 .
 459 .   int target_index;
 460 .
 461 .   PTR used_by_bfd;
 462 .
 463 .        {* If this is a constructor section then here is a list of the
 464 .           relocations created to relocate items within it. *}
 465 .
 466 .   struct relent_chain *constructor_chain;
 467 .
 468 .        {* The BFD which owns the section. *}
 469 .
 470 .   bfd *owner;
 471 .
 472 .        {* A symbol which points at this section only *}
 473 .   struct symbol_cache_entry *symbol;
 474 .   struct symbol_cache_entry **symbol_ptr_ptr;
 475 .
 476 .   struct bfd_link_order *link_order_head;
 477 .   struct bfd_link_order *link_order_tail;
 478 .} asection ;
 479 .
 480 .    {* These sections are global, and are managed by BFD.  The application
 481 .       and target back end are not permitted to change the values in
 482 .       these sections.  New code should use the section_ptr macros rather
 483 .       than referring directly to the const sections.  The const sections
 484 .       may eventually vanish.  *}
 485 .#define BFD_ABS_SECTION_NAME "*ABS*"
 486 .#define BFD_UND_SECTION_NAME "*UND*"
 487 .#define BFD_COM_SECTION_NAME "*COM*"
 488 .#define BFD_IND_SECTION_NAME "*IND*"
 489 .
 490 .    {* the absolute section *}
 491 .extern const asection bfd_abs_section;
 492 .#define bfd_abs_section_ptr ((asection *) &bfd_abs_section)
 493 .#define bfd_is_abs_section(sec) ((sec) == bfd_abs_section_ptr)
 494 .    {* Pointer to the undefined section *}
 495 .extern const asection bfd_und_section;
 496 .#define bfd_und_section_ptr ((asection *) &bfd_und_section)
 497 .#define bfd_is_und_section(sec) ((sec) == bfd_und_section_ptr)
 498 .    {* Pointer to the common section *}
 499 .extern const asection bfd_com_section;
 500 .#define bfd_com_section_ptr ((asection *) &bfd_com_section)
 501 .    {* Pointer to the indirect section *}
 502 .extern const asection bfd_ind_section;
 503 .#define bfd_ind_section_ptr ((asection *) &bfd_ind_section)
 504 .#define bfd_is_ind_section(sec) ((sec) == bfd_ind_section_ptr)
 505 .
 506 .extern const struct symbol_cache_entry * const bfd_abs_symbol;
 507 .extern const struct symbol_cache_entry * const bfd_com_symbol;
 508 .extern const struct symbol_cache_entry * const bfd_und_symbol;
 509 .extern const struct symbol_cache_entry * const bfd_ind_symbol;
 510 .#define bfd_get_section_size_before_reloc(section) \
 511 .     ((section)->reloc_done ? (abort (), (bfd_size_type) 1) \
 512 .                            : (section)->_raw_size)
 513 .#define bfd_get_section_size_after_reloc(section) \
 514 .     ((section)->reloc_done ? (section)->_cooked_size \
 515 .                            : (abort (), (bfd_size_type) 1))
 516 */
 517
 518 /* We use a macro to initialize the static asymbol structures because
 519    traditional C does not permit us to initialize a union member while
 520    gcc warns if we don't initialize it.  */
 521  /* the_bfd, name, value, attr, section [, udata] */
 522 #ifdef __STDC__
 523 #define GLOBAL_SYM_INIT(NAME, SECTION) \
 524   { 0, NAME, 0, BSF_SECTION_SYM, (asection *) SECTION, { 0 }}
 525 #else
 526 #define GLOBAL_SYM_INIT(NAME, SECTION) \
 527   { 0, NAME, 0, BSF_SECTION_SYM, (asection *) SECTION }
 528 #endif
 529
 530 /* These symbols are global, not specific to any BFD.  Therefore, anything
 531    that tries to change them is broken, and should be repaired.  */
 532
 533 static const asymbol global_syms[] =
 534 {
 535   GLOBAL_SYM_INIT (BFD_COM_SECTION_NAME, &bfd_com_section),
 536   GLOBAL_SYM_INIT (BFD_UND_SECTION_NAME, &bfd_und_section),
 537   GLOBAL_SYM_INIT (BFD_ABS_SECTION_NAME, &bfd_abs_section),
 538   GLOBAL_SYM_INIT (BFD_IND_SECTION_NAME, &bfd_ind_section)
 539 };
 540
 541 #define STD_SECTION(SEC, FLAGS, SYM, NAME, IDX) \
 542   const asymbol * const SYM = (asymbol *) &global_syms[IDX]; \
 543   const asection SEC = \
 544     /* name, index, next, flags, set_vma, reloc_done, linker_mark, gc_mark */ \
 545     { NAME,  0,     0,    FLAGS, 0,       0,          0,           0,         \
 546                                                                               \
 547     /* vma, lma, _cooked_size, _raw_size, output_offset, output_section, */   \
 548        0,   0,   0,            0,         0,             (struct sec *) &SEC, \
 549                                                                               \
 550     /* alig..., reloc..., orel..., reloc_count, filepos, rel_..., line_... */ \
 551        0,       0,        0,       0,           0,       0,        0,         \
 552                                                                               \
 553     /* userdata, contents, lineno, lineno_count */                            \
 554        0,        0,        0,      0,                                         \
 555                                                                               \
 556     /* comdat_info, moving_line_filepos, target_index, used_by_bfd,  */       \
 557        NULL,        0,                   0,            0,                     \
 558                                                                               \
 559     /* cons..., owner, symbol */                                              \
 560        0,       0,     (struct symbol_cache_entry *) &global_syms[IDX],       \
 561                                                                               \
 562     /* symbol_ptr_ptr,                      link_order_head, ..._tail */      \
 563        (struct symbol_cache_entry **) &SYM, 0,               0                \
 564     }
 565
 566 STD_SECTION (bfd_com_section, SEC_IS_COMMON, bfd_com_symbol,
 567              BFD_COM_SECTION_NAME, 0);
 568 STD_SECTION (bfd_und_section, 0, bfd_und_symbol, BFD_UND_SECTION_NAME, 1);
 569 STD_SECTION (bfd_abs_section, 0, bfd_abs_symbol, BFD_ABS_SECTION_NAME, 2);
 570 STD_SECTION (bfd_ind_section, 0, bfd_ind_symbol, BFD_IND_SECTION_NAME, 3);
 571 #undef STD_SECTION
 572
 573 /*
 574 DOCDD
 575 INODE
 576 section prototypes,  , typedef asection, Sections
 577 SUBSECTION
 578         Section prototypes
 579
 580 These are the functions exported by the section handling part of BFD.
 581 */
 582
 583 /*
 584 FUNCTION
 585         bfd_get_section_by_name
 586
 587 SYNOPSIS
 588         asection *bfd_get_section_by_name(bfd *abfd, CONST char *name);
 589
 590 DESCRIPTION
 591         Run through @var{abfd} and return the one of the
 592         <<asection>>s whose name matches @var{name}, otherwise <<NULL>>.
 593         @xref{Sections}, for more information.
 594
 595         This should only be used in special cases; the normal way to process
 596         all sections of a given name is to use <<bfd_map_over_sections>> and
 597         <<strcmp>> on the name (or better yet, base it on the section flags
 598         or something else) for each section.
 599 */
 600
 601 asection *
 602 bfd_get_section_by_name (abfd, name)
 603      bfd *abfd;
 604      CONST char *name;
 605 {
 606   asection *sect;
 607
 608   for (sect = abfd->sections; sect != NULL; sect = sect->next)
 609     if (!strcmp (sect->name, name))
 610       return sect;
 611   return NULL;
 612 }
 613
 614
 615 /*
 616 FUNCTION
 617         bfd_make_section_old_way
 618
 619 SYNOPSIS
 620         asection *bfd_make_section_old_way(bfd *abfd, CONST char *name);
 621
 622 DESCRIPTION
 623         Create a new empty section called @var{name}
 624         and attach it to the end of the chain of sections for the
 625         BFD @var{abfd}. An attempt to create a section with a name which
 626         is already in use returns its pointer without changing the
 627         section chain.
 628
 629         It has the funny name since this is the way it used to be
 630         before it was rewritten....
 631
 632         Possible errors are:
 633         o <<bfd_error_invalid_operation>> -
 634         If output has already started for this BFD.
 635         o <<bfd_error_no_memory>> -
 636         If memory allocation fails.
 637
 638 */
 639
 640
 641 asection *
 642 bfd_make_section_old_way (abfd, name)
 643      bfd *abfd;
 644      CONST char *name;
 645 {
 646   asection *sec = bfd_get_section_by_name (abfd, name);
 647   if (sec == (asection *) NULL)
 648     {
 649       sec = bfd_make_section (abfd, name);
 650     }
 651   return sec;
 652 }
 653
 654 /*
 655 FUNCTION
 656         bfd_make_section_anyway
 657
 658 SYNOPSIS
 659         asection *bfd_make_section_anyway(bfd *abfd, CONST char *name);
 660
 661 DESCRIPTION
 662    Create a new empty section called @var{name} and attach it to the end of
 663    the chain of sections for @var{abfd}.  Create a new section even if there
 664    is already a section with that name.
 665
 666    Return <<NULL>> and set <<bfd_error>> on error; possible errors are:
 667    o <<bfd_error_invalid_operation>> - If output has already started for @var{abfd}.
 668    o <<bfd_error_no_memory>> - If memory allocation fails.
 669 */
 670
 671 sec_ptr
 672 bfd_make_section_anyway (abfd, name)
 673      bfd *abfd;
 674      CONST char *name;
 675 {
 676   asection *newsect;
 677   asection **prev = &abfd->sections;
 678   asection *sect = abfd->sections;
 679
 680   if (abfd->output_has_begun)
 681     {
 682       bfd_set_error (bfd_error_invalid_operation);
 683       return NULL;
 684     }
 685
 686   while (sect)
 687     {
 688       prev = &sect->next;
 689       sect = sect->next;
 690     }
 691
 692   newsect = (asection *) bfd_zalloc (abfd, sizeof (asection));
 693   if (newsect == NULL)
 694     return NULL;
 695
 696   newsect->name = name;
 697   newsect->index = abfd->section_count++;
 698   newsect->flags = SEC_NO_FLAGS;
 699
 700   newsect->userdata = NULL;
 701   newsect->contents = NULL;
 702   newsect->next = (asection *) NULL;
 703   newsect->relocation = (arelent *) NULL;
 704   newsect->reloc_count = 0;
 705   newsect->line_filepos = 0;
 706   newsect->owner = abfd;
 707   newsect->comdat = NULL;
 708
 709   /* Create a symbol whos only job is to point to this section. This is
 710      useful for things like relocs which are relative to the base of a
 711      section.  */
 712   newsect->symbol = bfd_make_empty_symbol (abfd);
 713   if (newsect->symbol == NULL)
 714     return NULL;
 715   newsect->symbol->name = name;
 716   newsect->symbol->value = 0;
 717   newsect->symbol->section = newsect;
 718   newsect->symbol->flags = BSF_SECTION_SYM;
 719
 720   newsect->symbol_ptr_ptr = &newsect->symbol;
 721
 722   if (BFD_SEND (abfd, _new_section_hook, (abfd, newsect)) != true)
 723     {
 724       free (newsect);
 725       return NULL;
 726     }
 727
 728   *prev = newsect;
 729   return newsect;
 730 }
 731
 732 /*
 733 FUNCTION
 734         bfd_make_section
 735
 736 SYNOPSIS
 737         asection *bfd_make_section(bfd *, CONST char *name);
 738
 739 DESCRIPTION
 740    Like <<bfd_make_section_anyway>>, but return <<NULL>> (without calling
 741    bfd_set_error ()) without changing the section chain if there is already a
 742    section named @var{name}.  If there is an error, return <<NULL>> and set
 743    <<bfd_error>>.
 744 */
 745
 746 asection *
 747 bfd_make_section (abfd, name)
 748      bfd *abfd;
 749      CONST char *name;
 750 {
 751   asection *sect = abfd->sections;
 752
 753   if (strcmp (name, BFD_ABS_SECTION_NAME) == 0)
 754     {
 755       return bfd_abs_section_ptr;
 756     }
 757   if (strcmp (name, BFD_COM_SECTION_NAME) == 0)
 758     {
 759       return bfd_com_section_ptr;
 760     }
 761   if (strcmp (name, BFD_UND_SECTION_NAME) == 0)
 762     {
 763       return bfd_und_section_ptr;
 764     }
 765
 766   if (strcmp (name, BFD_IND_SECTION_NAME) == 0)
 767     {
 768       return bfd_ind_section_ptr;
 769     }
 770
 771   while (sect)
 772     {
 773       if (!strcmp (sect->name, name))
 774         return NULL;
 775       sect = sect->next;
 776     }
 777
 778   /* The name is not already used; go ahead and make a new section.  */
 779   return bfd_make_section_anyway (abfd, name);
 780 }
 781
 782
 783 /*
 784 FUNCTION
 785         bfd_set_section_flags
 786
 787 SYNOPSIS
 788         boolean bfd_set_section_flags(bfd *abfd, asection *sec, flagword flags);
 789
 790 DESCRIPTION
 791         Set the attributes of the section @var{sec} in the BFD
 792         @var{abfd} to the value @var{flags}. Return <<true>> on success,
 793         <<false>> on error. Possible error returns are:
 794
 795         o <<bfd_error_invalid_operation>> -
 796         The section cannot have one or more of the attributes
 797         requested. For example, a .bss section in <<a.out>> may not
 798         have the <<SEC_HAS_CONTENTS>> field set.
 799
 800 */
 801
 802 /*ARGSUSED*/
 803 boolean
 804 bfd_set_section_flags (abfd, section, flags)
 805      bfd *abfd ATTRIBUTE_UNUSED;
 806      sec_ptr section;
 807      flagword flags;
 808 {
 809 #if 0
 810   /* If you try to copy a text section from an input file (where it
 811      has the SEC_CODE flag set) to an output file, this loses big if
 812      the bfd_applicable_section_flags (abfd) doesn't have the SEC_CODE
 813      set - which it doesn't, at least not for a.out.  FIXME */
 814
 815   if ((flags & bfd_applicable_section_flags (abfd)) != flags)
 816     {
 817       bfd_set_error (bfd_error_invalid_operation);
 818       return false;
 819     }
 820 #endif
 821
 822   section->flags = flags;
 823   return true;
 824 }
 825
 826
 827 /*
 828 FUNCTION
 829         bfd_map_over_sections
 830
 831 SYNOPSIS
 832         void bfd_map_over_sections(bfd *abfd,
 833                                    void (*func)(bfd *abfd,
 834                                                 asection *sect,
 835                                                 PTR obj),
 836                                    PTR obj);
 837
 838 DESCRIPTION
 839         Call the provided function @var{func} for each section
 840         attached to the BFD @var{abfd}, passing @var{obj} as an
 841         argument. The function will be called as if by
 842
 843 |       func(abfd, the_section, obj);
 844
 845         This is the prefered method for iterating over sections; an
 846         alternative would be to use a loop:
 847
 848 |          section *p;
 849 |          for (p = abfd->sections; p != NULL; p = p->next)
 850 |             func(abfd, p, ...)
 851
 852
 853 */
 854
 855 /*VARARGS2*/
 856 void
 857 bfd_map_over_sections (abfd, operation, user_storage)
 858      bfd *abfd;
 859      void (*operation) PARAMS ((bfd * abfd, asection * sect, PTR obj));
 860      PTR user_storage;
 861 {
 862   asection *sect;
 863   unsigned int i = 0;
 864
 865   for (sect = abfd->sections; sect != NULL; i++, sect = sect->next)
 866     (*operation) (abfd, sect, user_storage);
 867
 868   if (i != abfd->section_count) /* Debugging */
 869     abort ();
 870 }
 871
 872
 873 /*
 874 FUNCTION
 875         bfd_set_section_size
 876
 877 SYNOPSIS
 878         boolean bfd_set_section_size(bfd *abfd, asection *sec, bfd_size_type val);
 879
 880 DESCRIPTION
 881         Set @var{sec} to the size @var{val}. If the operation is
 882         ok, then <<true>> is returned, else <<false>>.
 883
 884         Possible error returns:
 885         o <<bfd_error_invalid_operation>> -
 886         Writing has started to the BFD, so setting the size is invalid.
 887
 888 */
 889
 890 boolean
 891 bfd_set_section_size (abfd, ptr, val)
 892      bfd *abfd;
 893      sec_ptr ptr;
 894      bfd_size_type val;
 895 {
 896   /* Once you've started writing to any section you cannot create or change
 897      the size of any others. */
 898
 899   if (abfd->output_has_begun)
 900     {
 901       bfd_set_error (bfd_error_invalid_operation);
 902       return false;
 903     }
 904
 905   ptr->_cooked_size = val;
 906   ptr->_raw_size = val;
 907
 908   return true;
 909 }
 910
 911 /*
 912 FUNCTION
 913         bfd_set_section_contents
 914
 915 SYNOPSIS
 916         boolean bfd_set_section_contents
 917          (bfd *abfd,
 918          asection *section,
 919          PTR data,
 920          file_ptr offset,
 921          bfd_size_type count);
 922
 923
 924 DESCRIPTION
 925         Sets the contents of the section @var{section} in BFD
 926         @var{abfd} to the data starting in memory at @var{data}. The
 927         data is written to the output section starting at offset
 928         @var{offset} for @var{count} octets.
 929
 930
 931
 932         Normally <<true>> is returned, else <<false>>. Possible error
 933         returns are:
 934         o <<bfd_error_no_contents>> -
 935         The output section does not have the <<SEC_HAS_CONTENTS>>
 936         attribute, so nothing can be written to it.
 937         o and some more too
 938
 939         This routine is front end to the back end function
 940         <<_bfd_set_section_contents>>.
 941
 942
 943 */
 944
 945 #define bfd_get_section_size_now(abfd,sec) \
 946 (sec->reloc_done \
 947  ? bfd_get_section_size_after_reloc (sec) \
 948  : bfd_get_section_size_before_reloc (sec))
 949
 950 boolean
 951 bfd_set_section_contents (abfd, section, location, offset, count)
 952      bfd *abfd;
 953      sec_ptr section;
 954      PTR location;
 955      file_ptr offset;
 956      bfd_size_type count;
 957 {
 958   bfd_size_type sz;
 959
 960   if (!(bfd_get_section_flags (abfd, section) & SEC_HAS_CONTENTS))
 961     {
 962       bfd_set_error (bfd_error_no_contents);
 963       return (false);
 964     }
 965
 966   if (offset < 0)
 967     {
 968     bad_val:
 969       bfd_set_error (bfd_error_bad_value);
 970       return false;
 971     }
 972   sz = bfd_get_section_size_now (abfd, section);
 973   if ((bfd_size_type) offset > sz
 974       || count > sz
 975       || offset + count > sz)
 976     goto bad_val;
 977
 978   switch (abfd->direction)
 979     {
 980     case read_direction:
 981     case no_direction:
 982       bfd_set_error (bfd_error_invalid_operation);
 983       return false;
 984
 985     case write_direction:
 986       break;
 987
 988     case both_direction:
 989       /* File is opened for update. `output_has_begun' some time ago when
 990            the file was created.  Do not recompute sections sizes or alignments
 991            in _bfd_set_section_content.  */
 992       abfd->output_has_begun = true;
 993       break;
 994     }
 995
 996   if (BFD_SEND (abfd, _bfd_set_section_contents,
 997                 (abfd, section, location, offset, count)))
 998     {
 999       abfd->output_has_begun = true;
1000       return true;
1001     }
1002
1003   return false;
1004 }
1005
1006 /*
1007 FUNCTION
1008         bfd_get_section_contents
1009
1010 SYNOPSIS
1011         boolean bfd_get_section_contents
1012         (bfd *abfd, asection *section, PTR location,
1013          file_ptr offset, bfd_size_type count);
1014
1015 DESCRIPTION
1016         Read data from @var{section} in BFD @var{abfd}
1017         into memory starting at @var{location}. The data is read at an
1018         offset of @var{offset} from the start of the input section,
1019         and is read for @var{count} bytes.
1020
1021         If the contents of a constructor with the <<SEC_CONSTRUCTOR>>
1022         flag set are requested or if the section does not have the
1023         <<SEC_HAS_CONTENTS>> flag set, then the @var{location} is filled
1024         with zeroes. If no errors occur, <<true>> is returned, else
1025         <<false>>.
1026
1027
1028
1029 */
1030 boolean
1031 bfd_get_section_contents (abfd, section, location, offset, count)
1032      bfd *abfd;
1033      sec_ptr section;
1034      PTR location;
1035      file_ptr offset;
1036      bfd_size_type count;
1037 {
1038   bfd_size_type sz;
1039
1040   if (section->flags & SEC_CONSTRUCTOR)
1041     {
1042       memset (location, 0, (unsigned) count);
1043       return true;
1044     }
1045
1046   if (offset < 0)
1047     {
1048     bad_val:
1049       bfd_set_error (bfd_error_bad_value);
1050       return false;
1051     }
1052   /* Even if reloc_done is true, this function reads unrelocated
1053      contents, so we want the raw size.  */
1054   sz = section->_raw_size;
1055   if ((bfd_size_type) offset > sz || count > sz || offset + count > sz)
1056     goto bad_val;
1057
1058   if (count == 0)
1059     /* Don't bother.  */
1060     return true;
1061
1062   if ((section->flags & SEC_HAS_CONTENTS) == 0)
1063     {
1064       memset (location, 0, (unsigned) count);
1065       return true;
1066     }
1067
1068   if ((section->flags & SEC_IN_MEMORY) != 0)
1069     {
1070       memcpy (location, section->contents + offset, (size_t) count);
1071       return true;
1072     }
1073
1074   return BFD_SEND (abfd, _bfd_get_section_contents,
1075                    (abfd, section, location, offset, count));
1076 }
1077
1078 /*
1079 FUNCTION
1080         bfd_copy_private_section_data
1081
1082 SYNOPSIS
1083         boolean bfd_copy_private_section_data(bfd *ibfd, asection *isec, bfd *obfd, asection *osec);
1084
1085 DESCRIPTION
1086         Copy private section information from @var{isec} in the BFD
1087         @var{ibfd} to the section @var{osec} in the BFD @var{obfd}.
1088         Return <<true>> on success, <<false>> on error.  Possible error
1089         returns are:
1090
1091         o <<bfd_error_no_memory>> -
1092         Not enough memory exists to create private data for @var{osec}.
1093
1094 .#define bfd_copy_private_section_data(ibfd, isection, obfd, osection) \
1095 .     BFD_SEND (obfd, _bfd_copy_private_section_data, \
1096 .               (ibfd, isection, obfd, osection))
1097 */
1098
1099 /*
1100 FUNCTION
1101         _bfd_strip_section_from_output
1102
1103 SYNOPSIS
1104         void _bfd_strip_section_from_output
1105         (struct bfd_link_info *info, asection *section);
1106
1107 DESCRIPTION
1108         Remove @var{section} from the output.  If the output section
1109         becomes empty, remove it from the output bfd.  @var{info} may
1110         be NULL; if it is not, it is used to decide whether the output
1111         section is empty.
1112 */
1113 void
1114 _bfd_strip_section_from_output (info, s)
1115      struct bfd_link_info *info;
1116      asection *s;
1117 {
1118   asection **spp, *os;
1119   struct bfd_link_order *p, *pp;
1120   boolean keep_os;
1121
1122   /* Excise the input section from the link order.
1123
1124      FIXME: For all calls that I can see to this function, the link
1125      orders have not yet been set up.  So why are we checking them? --
1126      Ian */
1127   os = s->output_section;
1128   for (p = os->link_order_head, pp = NULL; p != NULL; pp = p, p = p->next)
1129     if (p->type == bfd_indirect_link_order
1130         && p->u.indirect.section == s)
1131       {
1132         if (pp)
1133           pp->next = p->next;
1134         else
1135           os->link_order_head = p->next;
1136         if (!p->next)
1137           os->link_order_tail = pp;
1138         break;
1139       }
1140
1141   keep_os = os->link_order_head != NULL;
1142
1143   if (! keep_os && info != NULL)
1144     {
1145       bfd *abfd;
1146       for (abfd = info->input_bfds; abfd != NULL; abfd = abfd->link_next)
1147         {
1148           asection *is;
1149           for (is = abfd->sections; is != NULL; is = is->next)
1150             {
1151               if (is != s && is->output_section == os)
1152                 break;
1153             }
1154           if (is != NULL)
1155             break;
1156         }
1157       if (abfd != NULL)
1158         keep_os = true;
1159     }
1160
1161   /* If the output section is empty, remove it too.  Careful about sections
1162      that have been discarded in the link script -- they are mapped to
1163      bfd_abs_section, which has no owner.  */
1164   if (!keep_os && os->owner != NULL)
1165     {
1166       for (spp = &os->owner->sections; *spp; spp = &(*spp)->next)
1167         if (*spp == os)
1168           {
1169             *spp = os->next;
1170             os->owner->section_count--;
1171             break;
1172           }
1173     }
1174 }