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1 1181 sfurman
@section Sections
2
The raw data contained within a BFD is maintained through the
3
section abstraction.  A single BFD may have any number of
4
sections.  It keeps hold of them by pointing to the first;
5
each one points to the next in the list.
6
 
7
Sections are supported in BFD in @code{section.c}.
8
 
9
@menu
10
* Section Input::
11
* Section Output::
12
* typedef asection::
13
* section prototypes::
14
@end menu
15
 
16
@node Section Input, Section Output, Sections, Sections
17
@subsection Section input
18
When a BFD is opened for reading, the section structures are
19
created and attached to the BFD.
20
 
21
Each section has a name which describes the section in the
22
outside world---for example, @code{a.out} would contain at least
23
three sections, called @code{.text}, @code{.data} and @code{.bss}.
24
 
25
Names need not be unique; for example a COFF file may have several
26
sections named @code{.data}.
27
 
28
Sometimes a BFD will contain more than the ``natural'' number of
29
sections. A back end may attach other sections containing
30
constructor data, or an application may add a section (using
31
@code{bfd_make_section}) to the sections attached to an already open
32
BFD. For example, the linker creates an extra section
33
@code{COMMON} for each input file's BFD to hold information about
34
common storage.
35
 
36
The raw data is not necessarily read in when
37
the section descriptor is created. Some targets may leave the
38
data in place until a @code{bfd_get_section_contents} call is
39
made. Other back ends may read in all the data at once.  For
40
example, an S-record file has to be read once to determine the
41
size of the data. An IEEE-695 file doesn't contain raw data in
42
sections, but data and relocation expressions intermixed, so
43
the data area has to be parsed to get out the data and
44
relocations.
45
 
46
@node Section Output, typedef asection, Section Input, Sections
47
@subsection Section output
48
To write a new object style BFD, the various sections to be
49
written have to be created. They are attached to the BFD in
50
the same way as input sections; data is written to the
51
sections using @code{bfd_set_section_contents}.
52
 
53
Any program that creates or combines sections (e.g., the assembler
54
and linker) must use the @code{asection} fields @code{output_section} and
55
@code{output_offset} to indicate the file sections to which each
56
section must be written.  (If the section is being created from
57
scratch, @code{output_section} should probably point to the section
58
itself and @code{output_offset} should probably be zero.)
59
 
60
The data to be written comes from input sections attached
61
(via @code{output_section} pointers) to
62
the output sections.  The output section structure can be
63
considered a filter for the input section: the output section
64
determines the vma of the output data and the name, but the
65
input section determines the offset into the output section of
66
the data to be written.
67
 
68
E.g., to create a section "O", starting at 0x100, 0x123 long,
69
containing two subsections, "A" at offset 0x0 (i.e., at vma
70
0x100) and "B" at offset 0x20 (i.e., at vma 0x120) the @code{asection}
71
structures would look like:
72
 
73
@example
74
   section name          "A"
75
     output_offset   0x00
76
     size            0x20
77
     output_section ----------->  section name    "O"
78
                             |    vma             0x100
79
   section name          "B" |    size            0x123
80
     output_offset   0x20    |
81
     size            0x103   |
82
     output_section  --------|
83
@end example
84
 
85
@subsection Link orders
86
The data within a section is stored in a @dfn{link_order}.
87
These are much like the fixups in @code{gas}.  The link_order
88
abstraction allows a section to grow and shrink within itself.
89
 
90
A link_order knows how big it is, and which is the next
91
link_order and where the raw data for it is; it also points to
92
a list of relocations which apply to it.
93
 
94
The link_order is used by the linker to perform relaxing on
95
final code.  The compiler creates code which is as big as
96
necessary to make it work without relaxing, and the user can
97
select whether to relax.  Sometimes relaxing takes a lot of
98
time.  The linker runs around the relocations to see if any
99
are attached to data which can be shrunk, if so it does it on
100
a link_order by link_order basis.
101
 
102
 
103
@node typedef asection, section prototypes, Section Output, Sections
104
@subsection typedef asection
105
Here is the section structure:
106
 
107
 
108
@example
109
 
110
/* This structure is used for a comdat section, as in PE.  A comdat
111
   section is associated with a particular symbol.  When the linker
112
   sees a comdat section, it keeps only one of the sections with a
113
   given name and associated with a given symbol.  */
114
 
115
struct bfd_comdat_info
116
@{
117
  /* The name of the symbol associated with a comdat section.  */
118
  const char *name;
119
 
120
  /* The local symbol table index of the symbol associated with a
121
     comdat section.  This is only meaningful to the object file format
122
     specific code; it is not an index into the list returned by
123
     bfd_canonicalize_symtab.  */
124
  long symbol;
125
@};
126
 
127
typedef struct sec
128
@{
129
  /* The name of the section; the name isn't a copy, the pointer is
130
     the same as that passed to bfd_make_section.  */
131
  const char *name;
132
 
133
  /* A unique sequence number.  */
134
  int id;
135
 
136
  /* Which section in the bfd; 0..n-1 as sections are created in a bfd.  */
137
  int index;
138
 
139
  /* The next section in the list belonging to the BFD, or NULL.  */
140
  struct sec *next;
141
 
142
  /* The field flags contains attributes of the section. Some
143
     flags are read in from the object file, and some are
144
     synthesized from other information.  */
145
  flagword flags;
146
 
147
#define SEC_NO_FLAGS   0x000
148
 
149
  /* Tells the OS to allocate space for this section when loading.
150
     This is clear for a section containing debug information only.  */
151
#define SEC_ALLOC      0x001
152
 
153
  /* Tells the OS to load the section from the file when loading.
154
     This is clear for a .bss section.  */
155
#define SEC_LOAD       0x002
156
 
157
  /* The section contains data still to be relocated, so there is
158
     some relocation information too.  */
159
#define SEC_RELOC      0x004
160
 
161
  /* ELF reserves 4 processor specific bits and 8 operating system
162
     specific bits in sh_flags; at present we can get away with just
163
     one in communicating between the assembler and BFD, but this
164
     isn't a good long-term solution.  */
165
#define SEC_ARCH_BIT_0 0x008
166
 
167
  /* A signal to the OS that the section contains read only data.  */
168
#define SEC_READONLY   0x010
169
 
170
  /* The section contains code only.  */
171
#define SEC_CODE       0x020
172
 
173
  /* The section contains data only.  */
174
#define SEC_DATA       0x040
175
 
176
  /* The section will reside in ROM.  */
177
#define SEC_ROM        0x080
178
 
179
  /* The section contains constructor information. This section
180
     type is used by the linker to create lists of constructors and
181
     destructors used by @code{g++}. When a back end sees a symbol
182
     which should be used in a constructor list, it creates a new
183
     section for the type of name (e.g., @code{__CTOR_LIST__}), attaches
184
     the symbol to it, and builds a relocation. To build the lists
185
     of constructors, all the linker has to do is catenate all the
186
     sections called @code{__CTOR_LIST__} and relocate the data
187
     contained within - exactly the operations it would peform on
188
     standard data.  */
189
#define SEC_CONSTRUCTOR 0x100
190
 
191
  /* The section has contents - a data section could be
192
     @code{SEC_ALLOC} | @code{SEC_HAS_CONTENTS}; a debug section could be
193
     @code{SEC_HAS_CONTENTS}  */
194
#define SEC_HAS_CONTENTS 0x200
195
 
196
  /* An instruction to the linker to not output the section
197
     even if it has information which would normally be written.  */
198
#define SEC_NEVER_LOAD 0x400
199
 
200
  /* The section is a COFF shared library section.  This flag is
201
     only for the linker.  If this type of section appears in
202
     the input file, the linker must copy it to the output file
203
     without changing the vma or size.  FIXME: Although this
204
     was originally intended to be general, it really is COFF
205
     specific (and the flag was renamed to indicate this).  It
206
     might be cleaner to have some more general mechanism to
207
     allow the back end to control what the linker does with
208
     sections.  */
209
#define SEC_COFF_SHARED_LIBRARY 0x800
210
 
211
  /* The section contains thread local data.  */
212
#define SEC_THREAD_LOCAL 0x1000
213
 
214
  /* The section has GOT references.  This flag is only for the
215
     linker, and is currently only used by the elf32-hppa back end.
216
     It will be set if global offset table references were detected
217
     in this section, which indicate to the linker that the section
218
     contains PIC code, and must be handled specially when doing a
219
     static link.  */
220
#define SEC_HAS_GOT_REF 0x4000
221
 
222
  /* The section contains common symbols (symbols may be defined
223
     multiple times, the value of a symbol is the amount of
224
     space it requires, and the largest symbol value is the one
225
     used).  Most targets have exactly one of these (which we
226
     translate to bfd_com_section_ptr), but ECOFF has two.  */
227
#define SEC_IS_COMMON 0x8000
228
 
229
  /* The section contains only debugging information.  For
230
     example, this is set for ELF .debug and .stab sections.
231
     strip tests this flag to see if a section can be
232
     discarded.  */
233
#define SEC_DEBUGGING 0x10000
234
 
235
  /* The contents of this section are held in memory pointed to
236
     by the contents field.  This is checked by bfd_get_section_contents,
237
     and the data is retrieved from memory if appropriate.  */
238
#define SEC_IN_MEMORY 0x20000
239
 
240
  /* The contents of this section are to be excluded by the
241
     linker for executable and shared objects unless those
242
     objects are to be further relocated.  */
243
#define SEC_EXCLUDE 0x40000
244
 
245
  /* The contents of this section are to be sorted based on the sum of
246
     the symbol and addend values specified by the associated relocation
247
     entries.  Entries without associated relocation entries will be
248
     appended to the end of the section in an unspecified order.  */
249
#define SEC_SORT_ENTRIES 0x80000
250
 
251
  /* When linking, duplicate sections of the same name should be
252
     discarded, rather than being combined into a single section as
253
     is usually done.  This is similar to how common symbols are
254
     handled.  See SEC_LINK_DUPLICATES below.  */
255
#define SEC_LINK_ONCE 0x100000
256
 
257
  /* If SEC_LINK_ONCE is set, this bitfield describes how the linker
258
     should handle duplicate sections.  */
259
#define SEC_LINK_DUPLICATES 0x600000
260
 
261
  /* This value for SEC_LINK_DUPLICATES means that duplicate
262
     sections with the same name should simply be discarded.  */
263
#define SEC_LINK_DUPLICATES_DISCARD 0x0
264
 
265
  /* This value for SEC_LINK_DUPLICATES means that the linker
266
     should warn if there are any duplicate sections, although
267
     it should still only link one copy.  */
268
#define SEC_LINK_DUPLICATES_ONE_ONLY 0x200000
269
 
270
  /* This value for SEC_LINK_DUPLICATES means that the linker
271
     should warn if any duplicate sections are a different size.  */
272
#define SEC_LINK_DUPLICATES_SAME_SIZE 0x400000
273
 
274
  /* This value for SEC_LINK_DUPLICATES means that the linker
275
     should warn if any duplicate sections contain different
276
     contents.  */
277
#define SEC_LINK_DUPLICATES_SAME_CONTENTS 0x600000
278
 
279
  /* This section was created by the linker as part of dynamic
280
     relocation or other arcane processing.  It is skipped when
281
     going through the first-pass output, trusting that someone
282
     else up the line will take care of it later.  */
283
#define SEC_LINKER_CREATED 0x800000
284
 
285
  /* This section should not be subject to garbage collection.  */
286
#define SEC_KEEP 0x1000000
287
 
288
  /* This section contains "short" data, and should be placed
289
     "near" the GP.  */
290
#define SEC_SMALL_DATA 0x2000000
291
 
292
  /* This section contains data which may be shared with other
293
     executables or shared objects.  */
294
#define SEC_SHARED 0x4000000
295
 
296
  /* When a section with this flag is being linked, then if the size of
297
     the input section is less than a page, it should not cross a page
298
     boundary.  If the size of the input section is one page or more, it
299
     should be aligned on a page boundary.  */
300
#define SEC_BLOCK 0x8000000
301
 
302
  /* Conditionally link this section; do not link if there are no
303
     references found to any symbol in the section.  */
304
#define SEC_CLINK 0x10000000
305
 
306
  /* Attempt to merge identical entities in the section.
307
     Entity size is given in the entsize field.  */
308
#define SEC_MERGE 0x20000000
309
 
310
  /* If given with SEC_MERGE, entities to merge are zero terminated
311
     strings where entsize specifies character size instead of fixed
312
     size entries.  */
313
#define SEC_STRINGS 0x40000000
314
 
315
  /* This section contains data about section groups.  */
316
#define SEC_GROUP 0x80000000
317
 
318
  /*  End of section flags.  */
319
 
320
  /* Some internal packed boolean fields.  */
321
 
322
  /* See the vma field.  */
323
  unsigned int user_set_vma : 1;
324
 
325
  /* Whether relocations have been processed.  */
326
  unsigned int reloc_done : 1;
327
 
328
  /* A mark flag used by some of the linker backends.  */
329
  unsigned int linker_mark : 1;
330
 
331
  /* Another mark flag used by some of the linker backends.  Set for
332
     output sections that have an input section.  */
333
  unsigned int linker_has_input : 1;
334
 
335
  /* A mark flag used by some linker backends for garbage collection.  */
336
  unsigned int gc_mark : 1;
337
 
338
  /* Used by the ELF code to mark sections which have been allocated
339
     to segments.  */
340
  unsigned int segment_mark : 1;
341
 
342
  /* End of internal packed boolean fields.  */
343
 
344
  /*  The virtual memory address of the section - where it will be
345
      at run time.  The symbols are relocated against this.  The
346
      user_set_vma flag is maintained by bfd; if it's not set, the
347
      backend can assign addresses (for example, in @code{a.out}, where
348
      the default address for @code{.data} is dependent on the specific
349
      target and various flags).  */
350
  bfd_vma vma;
351
 
352
  /*  The load address of the section - where it would be in a
353
      rom image; really only used for writing section header
354
      information.  */
355
  bfd_vma lma;
356
 
357
  /* The size of the section in octets, as it will be output.
358
     Contains a value even if the section has no contents (e.g., the
359
     size of @code{.bss}).  This will be filled in after relocation.  */
360
  bfd_size_type _cooked_size;
361
 
362
  /* The original size on disk of the section, in octets.  Normally this
363
     value is the same as the size, but if some relaxing has
364
     been done, then this value will be bigger.  */
365
  bfd_size_type _raw_size;
366
 
367
  /* If this section is going to be output, then this value is the
368
     offset in *bytes* into the output section of the first byte in the
369
     input section (byte ==> smallest addressable unit on the
370
     target).  In most cases, if this was going to start at the
371
     100th octet (8-bit quantity) in the output section, this value
372
     would be 100.  However, if the target byte size is 16 bits
373
     (bfd_octets_per_byte is "2"), this value would be 50.  */
374
  bfd_vma output_offset;
375
 
376
  /* The output section through which to map on output.  */
377
  struct sec *output_section;
378
 
379
  /* The alignment requirement of the section, as an exponent of 2 -
380
     e.g., 3 aligns to 2^3 (or 8).  */
381
  unsigned int alignment_power;
382
 
383
  /* If an input section, a pointer to a vector of relocation
384
     records for the data in this section.  */
385
  struct reloc_cache_entry *relocation;
386
 
387
  /* If an output section, a pointer to a vector of pointers to
388
     relocation records for the data in this section.  */
389
  struct reloc_cache_entry **orelocation;
390
 
391
  /* The number of relocation records in one of the above.  */
392
  unsigned reloc_count;
393
 
394
  /* Information below is back end specific - and not always used
395
     or updated.  */
396
 
397
  /* File position of section data.  */
398
  file_ptr filepos;
399
 
400
  /* File position of relocation info.  */
401
  file_ptr rel_filepos;
402
 
403
  /* File position of line data.  */
404
  file_ptr line_filepos;
405
 
406
  /* Pointer to data for applications.  */
407
  PTR userdata;
408
 
409
  /* If the SEC_IN_MEMORY flag is set, this points to the actual
410
     contents.  */
411
  unsigned char *contents;
412
 
413
  /* Attached line number information.  */
414
  alent *lineno;
415
 
416
  /* Number of line number records.  */
417
  unsigned int lineno_count;
418
 
419
  /* Entity size for merging purposes.  */
420
  unsigned int entsize;
421
 
422
  /* Optional information about a COMDAT entry; NULL if not COMDAT.  */
423
  struct bfd_comdat_info *comdat;
424
 
425
  /* When a section is being output, this value changes as more
426
     linenumbers are written out.  */
427
  file_ptr moving_line_filepos;
428
 
429
  /* What the section number is in the target world.  */
430
  int target_index;
431
 
432
  PTR used_by_bfd;
433
 
434
  /* If this is a constructor section then here is a list of the
435
     relocations created to relocate items within it.  */
436
  struct relent_chain *constructor_chain;
437
 
438
  /* The BFD which owns the section.  */
439
  bfd *owner;
440
 
441
  /* A symbol which points at this section only.  */
442
  struct symbol_cache_entry *symbol;
443
  struct symbol_cache_entry **symbol_ptr_ptr;
444
 
445
  struct bfd_link_order *link_order_head;
446
  struct bfd_link_order *link_order_tail;
447
@} asection;
448
 
449
/* These sections are global, and are managed by BFD.  The application
450
   and target back end are not permitted to change the values in
451
   these sections.  New code should use the section_ptr macros rather
452
   than referring directly to the const sections.  The const sections
453
   may eventually vanish.  */
454
#define BFD_ABS_SECTION_NAME "*ABS*"
455
#define BFD_UND_SECTION_NAME "*UND*"
456
#define BFD_COM_SECTION_NAME "*COM*"
457
#define BFD_IND_SECTION_NAME "*IND*"
458
 
459
/* The absolute section.  */
460
extern const asection bfd_abs_section;
461
#define bfd_abs_section_ptr ((asection *) &bfd_abs_section)
462
#define bfd_is_abs_section(sec) ((sec) == bfd_abs_section_ptr)
463
/* Pointer to the undefined section.  */
464
extern const asection bfd_und_section;
465
#define bfd_und_section_ptr ((asection *) &bfd_und_section)
466
#define bfd_is_und_section(sec) ((sec) == bfd_und_section_ptr)
467
/* Pointer to the common section.  */
468
extern const asection bfd_com_section;
469
#define bfd_com_section_ptr ((asection *) &bfd_com_section)
470
/* Pointer to the indirect section.  */
471
extern const asection bfd_ind_section;
472
#define bfd_ind_section_ptr ((asection *) &bfd_ind_section)
473
#define bfd_is_ind_section(sec) ((sec) == bfd_ind_section_ptr)
474
 
475
#define bfd_is_const_section(SEC)              \
476
 (   ((SEC) == bfd_abs_section_ptr)            \
477
  || ((SEC) == bfd_und_section_ptr)            \
478
  || ((SEC) == bfd_com_section_ptr)            \
479
  || ((SEC) == bfd_ind_section_ptr))
480
 
481
extern const struct symbol_cache_entry * const bfd_abs_symbol;
482
extern const struct symbol_cache_entry * const bfd_com_symbol;
483
extern const struct symbol_cache_entry * const bfd_und_symbol;
484
extern const struct symbol_cache_entry * const bfd_ind_symbol;
485
#define bfd_get_section_size_before_reloc(section) \
486
     ((section)->reloc_done ? (abort (), (bfd_size_type) 1) \
487
                            : (section)->_raw_size)
488
#define bfd_get_section_size_after_reloc(section) \
489
     ((section)->reloc_done ? (section)->_cooked_size \
490
                            : (abort (), (bfd_size_type) 1))
491
 
492
/* Macros to handle insertion and deletion of a bfd's sections.  These
493
   only handle the list pointers, ie. do not adjust section_count,
494
   target_index etc.  */
495
#define bfd_section_list_remove(ABFD, PS) \
496
  do                                                   \
497
    @{                                                  \
498
      asection **_ps = PS;                             \
499
      asection *_s = *_ps;                             \
500
      *_ps = _s->next;                                 \
501
      if (_s->next == NULL)                            \
502
        (ABFD)->section_tail = _ps;                    \
503
    @}                                                  \
504
  while (0)
505
#define bfd_section_list_insert(ABFD, PS, S) \
506
  do                                                   \
507
    @{                                                  \
508
      asection **_ps = PS;                             \
509
      asection *_s = S;                                \
510
      _s->next = *_ps;                                 \
511
      *_ps = _s;                                       \
512
      if (_s->next == NULL)                            \
513
        (ABFD)->section_tail = &_s->next;              \
514
    @}                                                  \
515
  while (0)
516
 
517
@end example
518
 
519
@node section prototypes,  , typedef asection, Sections
520
@subsection Section prototypes
521
These are the functions exported by the section handling part of BFD.
522
 
523
@findex bfd_section_list_clear
524
@subsubsection @code{bfd_section_list_clear}
525
@strong{Synopsis}
526
@example
527
void bfd_section_list_clear (bfd *);
528
@end example
529
@strong{Description}@*
530
Clears the section list, and also resets the section count and
531
hash table entries.
532
 
533
@findex bfd_get_section_by_name
534
@subsubsection @code{bfd_get_section_by_name}
535
@strong{Synopsis}
536
@example
537
asection *bfd_get_section_by_name(bfd *abfd, const char *name);
538
@end example
539
@strong{Description}@*
540
Run through @var{abfd} and return the one of the
541
@code{asection}s whose name matches @var{name}, otherwise @code{NULL}.
542
@xref{Sections}, for more information.
543
 
544
This should only be used in special cases; the normal way to process
545
all sections of a given name is to use @code{bfd_map_over_sections} and
546
@code{strcmp} on the name (or better yet, base it on the section flags
547
or something else) for each section.
548
 
549
@findex bfd_get_unique_section_name
550
@subsubsection @code{bfd_get_unique_section_name}
551
@strong{Synopsis}
552
@example
553
char *bfd_get_unique_section_name(bfd *abfd,
554
    const char *templat,
555
    int *count);
556
@end example
557
@strong{Description}@*
558
Invent a section name that is unique in @var{abfd} by tacking
559
a dot and a digit suffix onto the original @var{templat}.  If
560
@var{count} is non-NULL, then it specifies the first number
561
tried as a suffix to generate a unique name.  The value
562
pointed to by @var{count} will be incremented in this case.
563
 
564
@findex bfd_make_section_old_way
565
@subsubsection @code{bfd_make_section_old_way}
566
@strong{Synopsis}
567
@example
568
asection *bfd_make_section_old_way(bfd *abfd, const char *name);
569
@end example
570
@strong{Description}@*
571
Create a new empty section called @var{name}
572
and attach it to the end of the chain of sections for the
573
BFD @var{abfd}. An attempt to create a section with a name which
574
is already in use returns its pointer without changing the
575
section chain.
576
 
577
It has the funny name since this is the way it used to be
578
before it was rewritten....
579
 
580
Possible errors are:
581
@itemize @bullet
582
 
583
@item
584
@code{bfd_error_invalid_operation} -
585
If output has already started for this BFD.
586
@item
587
@code{bfd_error_no_memory} -
588
If memory allocation fails.
589
@end itemize
590
 
591
@findex bfd_make_section_anyway
592
@subsubsection @code{bfd_make_section_anyway}
593
@strong{Synopsis}
594
@example
595
asection *bfd_make_section_anyway(bfd *abfd, const char *name);
596
@end example
597
@strong{Description}@*
598
Create a new empty section called @var{name} and attach it to the end of
599
the chain of sections for @var{abfd}.  Create a new section even if there
600
is already a section with that name.
601
 
602
Return @code{NULL} and set @code{bfd_error} on error; possible errors are:
603
@itemize @bullet
604
 
605
@item
606
@code{bfd_error_invalid_operation} - If output has already started for @var{abfd}.
607
@item
608
@code{bfd_error_no_memory} - If memory allocation fails.
609
@end itemize
610
 
611
@findex bfd_make_section
612
@subsubsection @code{bfd_make_section}
613
@strong{Synopsis}
614
@example
615
asection *bfd_make_section(bfd *, const char *name);
616
@end example
617
@strong{Description}@*
618
Like @code{bfd_make_section_anyway}, but return @code{NULL} (without calling
619
bfd_set_error ()) without changing the section chain if there is already a
620
section named @var{name}.  If there is an error, return @code{NULL} and set
621
@code{bfd_error}.
622
 
623
@findex bfd_set_section_flags
624
@subsubsection @code{bfd_set_section_flags}
625
@strong{Synopsis}
626
@example
627
boolean bfd_set_section_flags(bfd *abfd, asection *sec, flagword flags);
628
@end example
629
@strong{Description}@*
630
Set the attributes of the section @var{sec} in the BFD
631
@var{abfd} to the value @var{flags}. Return @code{true} on success,
632
@code{false} on error. Possible error returns are:
633
 
634
@itemize @bullet
635
 
636
@item
637
@code{bfd_error_invalid_operation} -
638
The section cannot have one or more of the attributes
639
requested. For example, a .bss section in @code{a.out} may not
640
have the @code{SEC_HAS_CONTENTS} field set.
641
@end itemize
642
 
643
@findex bfd_map_over_sections
644
@subsubsection @code{bfd_map_over_sections}
645
@strong{Synopsis}
646
@example
647
void bfd_map_over_sections(bfd *abfd,
648
    void (*func) (bfd *abfd,
649
    asection *sect,
650
    PTR obj),
651
    PTR obj);
652
@end example
653
@strong{Description}@*
654
Call the provided function @var{func} for each section
655
attached to the BFD @var{abfd}, passing @var{obj} as an
656
argument. The function will be called as if by
657
 
658
@example
659
       func(abfd, the_section, obj);
660
@end example
661
 
662
This is the prefered method for iterating over sections; an
663
alternative would be to use a loop:
664
 
665
@example
666
          section *p;
667
          for (p = abfd->sections; p != NULL; p = p->next)
668
             func(abfd, p, ...)
669
@end example
670
 
671
@findex bfd_set_section_size
672
@subsubsection @code{bfd_set_section_size}
673
@strong{Synopsis}
674
@example
675
boolean bfd_set_section_size(bfd *abfd, asection *sec, bfd_size_type val);
676
@end example
677
@strong{Description}@*
678
Set @var{sec} to the size @var{val}. If the operation is
679
ok, then @code{true} is returned, else @code{false}.
680
 
681
Possible error returns:
682
@itemize @bullet
683
 
684
@item
685
@code{bfd_error_invalid_operation} -
686
Writing has started to the BFD, so setting the size is invalid.
687
@end itemize
688
 
689
@findex bfd_set_section_contents
690
@subsubsection @code{bfd_set_section_contents}
691
@strong{Synopsis}
692
@example
693
boolean bfd_set_section_contents (bfd *abfd, asection *section,
694
    PTR data, file_ptr offset,
695
    bfd_size_type count);
696
@end example
697
@strong{Description}@*
698
Sets the contents of the section @var{section} in BFD
699
@var{abfd} to the data starting in memory at @var{data}. The
700
data is written to the output section starting at offset
701
@var{offset} for @var{count} octets.
702
 
703
Normally @code{true} is returned, else @code{false}. Possible error
704
returns are:
705
@itemize @bullet
706
 
707
@item
708
@code{bfd_error_no_contents} -
709
The output section does not have the @code{SEC_HAS_CONTENTS}
710
attribute, so nothing can be written to it.
711
@item
712
and some more too
713
@end itemize
714
This routine is front end to the back end function
715
@code{_bfd_set_section_contents}.
716
 
717
@findex bfd_get_section_contents
718
@subsubsection @code{bfd_get_section_contents}
719
@strong{Synopsis}
720
@example
721
boolean bfd_get_section_contents (bfd *abfd, asection *section,
722
    PTR location, file_ptr offset,
723
    bfd_size_type count);
724
@end example
725
@strong{Description}@*
726
Read data from @var{section} in BFD @var{abfd}
727
into memory starting at @var{location}. The data is read at an
728
offset of @var{offset} from the start of the input section,
729
and is read for @var{count} bytes.
730
 
731
If the contents of a constructor with the @code{SEC_CONSTRUCTOR}
732
flag set are requested or if the section does not have the
733
@code{SEC_HAS_CONTENTS} flag set, then the @var{location} is filled
734
with zeroes. If no errors occur, @code{true} is returned, else
735
@code{false}.
736
 
737
@findex bfd_copy_private_section_data
738
@subsubsection @code{bfd_copy_private_section_data}
739
@strong{Synopsis}
740
@example
741
boolean bfd_copy_private_section_data (bfd *ibfd, asection *isec,
742
    bfd *obfd, asection *osec);
743
@end example
744
@strong{Description}@*
745
Copy private section information from @var{isec} in the BFD
746
@var{ibfd} to the section @var{osec} in the BFD @var{obfd}.
747
Return @code{true} on success, @code{false} on error.  Possible error
748
returns are:
749
 
750
@itemize @bullet
751
 
752
@item
753
@code{bfd_error_no_memory} -
754
Not enough memory exists to create private data for @var{osec}.
755
@end itemize
756
@example
757
#define bfd_copy_private_section_data(ibfd, isection, obfd, osection) \
758
     BFD_SEND (obfd, _bfd_copy_private_section_data, \
759
               (ibfd, isection, obfd, osection))
760
@end example
761
 
762
@findex _bfd_strip_section_from_output
763
@subsubsection @code{_bfd_strip_section_from_output}
764
@strong{Synopsis}
765
@example
766
void _bfd_strip_section_from_output
767
   (struct bfd_link_info *info, asection *section);
768
@end example
769
@strong{Description}@*
770
Remove @var{section} from the output.  If the output section
771
becomes empty, remove it from the output bfd.
772
 
773
This function won't actually do anything except twiddle flags
774
if called too late in the linking process, when it's not safe
775
to remove sections.
776
 
777
@findex bfd_generic_discard_group
778
@subsubsection @code{bfd_generic_discard_group}
779
@strong{Synopsis}
780
@example
781
boolean bfd_generic_discard_group (bfd *abfd, asection *group);
782
@end example
783
@strong{Description}@*
784
Remove all members of @var{group} from the output.
785
 

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