5 Each port of BFD to a different machine requries the creation
6 of a target back end. All the back end provides to the root
7 part of BFD is a structure containing pointers to functions
8 which perform certain low level operations on files. BFD
9 translates the applications's requests through a pointer into
10 calls to the back end routines.
12 When a file is opened with @code{bfd_openr}, its format and
13 target are unknown. BFD uses various mechanisms to determine
14 how to interpret the file. The operations performed are:
19 Create a BFD by calling the internal routine
20 @code{_bfd_new_bfd}, then call @code{bfd_find_target} with the
21 target string supplied to @code{bfd_openr} and the new BFD pointer.
24 If a null target string was provided to @code{bfd_find_target},
25 look up the environment variable @code{GNUTARGET} and use
26 that as the target string.
29 If the target string is still @code{NULL}, or the target string is
30 @code{default}, then use the first item in the target vector
31 as the target type, and set @code{target_defaulted} in the BFD to
32 cause @code{bfd_check_format} to loop through all the targets.
33 @xref{bfd_target}. @xref{Formats}.
36 Otherwise, inspect the elements in the target vector
37 one by one, until a match on target name is found. When found,
41 Otherwise return the error @code{bfd_error_invalid_target} to
45 @code{bfd_openr} attempts to open the file using
46 @code{bfd_open_file}, and returns the BFD.
48 Once the BFD has been opened and the target selected, the file
49 format may be determined. This is done by calling
50 @code{bfd_check_format} on the BFD with a suggested format.
51 If @code{target_defaulted} has been set, each possible target
52 type is tried to see if it recognizes the specified format.
53 @code{bfd_check_format} returns @code{true} when the caller guesses right.
58 @node bfd_target, , Targets, Targets
60 @subsection bfd_target
63 @strong{Description}@*
64 This structure contains everything that BFD knows about a
65 target. It includes things like its byte order, name, and which
66 routines to call to do various operations.
68 Every BFD points to a target structure with its @code{xvec}
71 The macros below are used to dispatch to functions through the
72 @code{bfd_target} vector. They are used in a number of macros further
73 down in @file{bfd.h}, and are also used when calling various
74 routines by hand inside the BFD implementation. The @var{arglist}
75 argument must be parenthesized; it contains all the arguments
76 to the called function.
78 They make the documentation (more) unpleasant to read, so if
79 someone wants to fix this and not break the above, please do.
81 #define BFD_SEND(bfd, message, arglist) \
82 ((*((bfd)->xvec->message)) arglist)
86 #define BFD_SEND(bfd, message, arglist) \
87 (((bfd) && (bfd)->xvec && (bfd)->xvec->message) ? \
88 ((*((bfd)->xvec->message)) arglist) : \
89 (bfd_assert (__FILE__,__LINE__), NULL))
92 For operations which index on the BFD format:
94 #define BFD_SEND_FMT(bfd, message, arglist) \
95 (((bfd)->xvec->message[(int) ((bfd)->format)]) arglist)
99 #define BFD_SEND_FMT(bfd, message, arglist) \
100 (((bfd) && (bfd)->xvec && (bfd)->xvec->message) ? \
101 (((bfd)->xvec->message[(int) ((bfd)->format)]) arglist) : \
102 (bfd_assert (__FILE__,__LINE__), NULL))
106 This is the structure which defines the type of BFD this is. The
107 @code{xvec} member of the struct @code{bfd} itself points here. Each
108 module that implements access to a different target under BFD,
109 defines one of these.
111 FIXME, these names should be rationalised with the names of
112 the entry points which call them. Too bad we can't have one
113 macro to define them both!
117 bfd_target_unknown_flavour,
118 bfd_target_aout_flavour,
119 bfd_target_coff_flavour,
120 bfd_target_ecoff_flavour,
121 bfd_target_xcoff_flavour,
122 bfd_target_elf_flavour,
123 bfd_target_ieee_flavour,
124 bfd_target_nlm_flavour,
125 bfd_target_oasys_flavour,
126 bfd_target_tekhex_flavour,
127 bfd_target_srec_flavour,
128 bfd_target_ihex_flavour,
129 bfd_target_som_flavour,
130 bfd_target_os9k_flavour,
131 bfd_target_versados_flavour,
132 bfd_target_msdos_flavour,
133 bfd_target_ovax_flavour,
134 bfd_target_evax_flavour,
135 bfd_target_mmo_flavour
138 enum bfd_endian @{ BFD_ENDIAN_BIG, BFD_ENDIAN_LITTLE, BFD_ENDIAN_UNKNOWN @};
140 /* Forward declaration. */
141 typedef struct bfd_link_info _bfd_link_info;
143 typedef struct bfd_target
145 /* Identifies the kind of target, e.g., SunOS4, Ultrix, etc. */
148 /* The "flavour" of a back end is a general indication about
149 the contents of a file. */
150 enum bfd_flavour flavour;
152 /* The order of bytes within the data area of a file. */
153 enum bfd_endian byteorder;
155 /* The order of bytes within the header parts of a file. */
156 enum bfd_endian header_byteorder;
158 /* A mask of all the flags which an executable may have set -
159 from the set @code{BFD_NO_FLAGS}, @code{HAS_RELOC}, ...@code{D_PAGED}. */
160 flagword object_flags;
162 /* A mask of all the flags which a section may have set - from
163 the set @code{SEC_NO_FLAGS}, @code{SEC_ALLOC}, ...@code{SET_NEVER_LOAD}. */
164 flagword section_flags;
166 /* The character normally found at the front of a symbol.
167 (if any), perhaps `_'. */
168 char symbol_leading_char;
170 /* The pad character for file names within an archive header. */
173 /* The maximum number of characters in an archive header. */
174 unsigned short ar_max_namelen;
176 /* Entries for byte swapping for data. These are different from the
177 other entry points, since they don't take a BFD asthe first argument.
178 Certain other handlers could do the same. */
179 bfd_vma (*bfd_getx64) PARAMS ((const bfd_byte *));
180 bfd_signed_vma (*bfd_getx_signed_64) PARAMS ((const bfd_byte *));
181 void (*bfd_putx64) PARAMS ((bfd_vma, bfd_byte *));
182 bfd_vma (*bfd_getx32) PARAMS ((const bfd_byte *));
183 bfd_signed_vma (*bfd_getx_signed_32) PARAMS ((const bfd_byte *));
184 void (*bfd_putx32) PARAMS ((bfd_vma, bfd_byte *));
185 bfd_vma (*bfd_getx16) PARAMS ((const bfd_byte *));
186 bfd_signed_vma (*bfd_getx_signed_16) PARAMS ((const bfd_byte *));
187 void (*bfd_putx16) PARAMS ((bfd_vma, bfd_byte *));
189 /* Byte swapping for the headers. */
190 bfd_vma (*bfd_h_getx64) PARAMS ((const bfd_byte *));
191 bfd_signed_vma (*bfd_h_getx_signed_64) PARAMS ((const bfd_byte *));
192 void (*bfd_h_putx64) PARAMS ((bfd_vma, bfd_byte *));
193 bfd_vma (*bfd_h_getx32) PARAMS ((const bfd_byte *));
194 bfd_signed_vma (*bfd_h_getx_signed_32) PARAMS ((const bfd_byte *));
195 void (*bfd_h_putx32) PARAMS ((bfd_vma, bfd_byte *));
196 bfd_vma (*bfd_h_getx16) PARAMS ((const bfd_byte *));
197 bfd_signed_vma (*bfd_h_getx_signed_16) PARAMS ((const bfd_byte *));
198 void (*bfd_h_putx16) PARAMS ((bfd_vma, bfd_byte *));
200 /* Format dependent routines: these are vectors of entry points
201 within the target vector structure, one for each format to check. */
203 /* Check the format of a file being read. Return a @code{bfd_target *} or zero. */
204 const struct bfd_target *(*_bfd_check_format[bfd_type_end]) PARAMS ((bfd *));
206 /* Set the format of a file being written. */
207 boolean (*_bfd_set_format[bfd_type_end]) PARAMS ((bfd *));
209 /* Write cached information into a file being written, at @code{bfd_close}. */
210 boolean (*_bfd_write_contents[bfd_type_end]) PARAMS ((bfd *));
213 The general target vector. These vectors are initialized using the
214 BFD_JUMP_TABLE macros.
217 /* Generic entry points. */
219 Do not "beautify" the CONCAT* macro args. Traditional C will not
220 remove whitespace added here, and thus will fail to concatenate
223 #define BFD_JUMP_TABLE_GENERIC(NAME) \
224 CONCAT2 (NAME,_close_and_cleanup), \
225 CONCAT2 (NAME,_bfd_free_cached_info), \
226 CONCAT2 (NAME,_new_section_hook), \
227 CONCAT2 (NAME,_get_section_contents), \
228 CONCAT2 (NAME,_get_section_contents_in_window)
230 /* Called when the BFD is being closed to do any necessary cleanup. */
231 boolean (*_close_and_cleanup) PARAMS ((bfd *));
232 /* Ask the BFD to free all cached information. */
233 boolean (*_bfd_free_cached_info) PARAMS ((bfd *));
234 /* Called when a new section is created. */
235 boolean (*_new_section_hook) PARAMS ((bfd *, sec_ptr));
236 /* Read the contents of a section. */
237 boolean (*_bfd_get_section_contents) PARAMS ((bfd *, sec_ptr, PTR,
238 file_ptr, bfd_size_type));
239 boolean (*_bfd_get_section_contents_in_window)
240 PARAMS ((bfd *, sec_ptr, bfd_window *, file_ptr, bfd_size_type));
242 /* Entry points to copy private data. */
243 #define BFD_JUMP_TABLE_COPY(NAME) \
244 CONCAT2 (NAME,_bfd_copy_private_bfd_data), \
245 CONCAT2 (NAME,_bfd_merge_private_bfd_data), \
246 CONCAT2 (NAME,_bfd_copy_private_section_data), \
247 CONCAT2 (NAME,_bfd_copy_private_symbol_data), \
248 CONCAT2 (NAME,_bfd_set_private_flags), \
249 CONCAT2 (NAME,_bfd_print_private_bfd_data) \
250 /* Called to copy BFD general private data from one object file
252 boolean (*_bfd_copy_private_bfd_data) PARAMS ((bfd *, bfd *));
253 /* Called to merge BFD general private data from one object file
254 to a common output file when linking. */
255 boolean (*_bfd_merge_private_bfd_data) PARAMS ((bfd *, bfd *));
256 /* Called to copy BFD private section data from one object file
258 boolean (*_bfd_copy_private_section_data) PARAMS ((bfd *, sec_ptr,
260 /* Called to copy BFD private symbol data from one symbol
262 boolean (*_bfd_copy_private_symbol_data) PARAMS ((bfd *, asymbol *,
264 /* Called to set private backend flags. */
265 boolean (*_bfd_set_private_flags) PARAMS ((bfd *, flagword));
267 /* Called to print private BFD data. */
268 boolean (*_bfd_print_private_bfd_data) PARAMS ((bfd *, PTR));
270 /* Core file entry points. */
271 #define BFD_JUMP_TABLE_CORE(NAME) \
272 CONCAT2 (NAME,_core_file_failing_command), \
273 CONCAT2 (NAME,_core_file_failing_signal), \
274 CONCAT2 (NAME,_core_file_matches_executable_p)
275 char * (*_core_file_failing_command) PARAMS ((bfd *));
276 int (*_core_file_failing_signal) PARAMS ((bfd *));
277 boolean (*_core_file_matches_executable_p) PARAMS ((bfd *, bfd *));
279 /* Archive entry points. */
280 #define BFD_JUMP_TABLE_ARCHIVE(NAME) \
281 CONCAT2 (NAME,_slurp_armap), \
282 CONCAT2 (NAME,_slurp_extended_name_table), \
283 CONCAT2 (NAME,_construct_extended_name_table), \
284 CONCAT2 (NAME,_truncate_arname), \
285 CONCAT2 (NAME,_write_armap), \
286 CONCAT2 (NAME,_read_ar_hdr), \
287 CONCAT2 (NAME,_openr_next_archived_file), \
288 CONCAT2 (NAME,_get_elt_at_index), \
289 CONCAT2 (NAME,_generic_stat_arch_elt), \
290 CONCAT2 (NAME,_update_armap_timestamp)
291 boolean (*_bfd_slurp_armap) PARAMS ((bfd *));
292 boolean (*_bfd_slurp_extended_name_table) PARAMS ((bfd *));
293 boolean (*_bfd_construct_extended_name_table)
294 PARAMS ((bfd *, char **, bfd_size_type *, const char **));
295 void (*_bfd_truncate_arname) PARAMS ((bfd *, const char *, char *));
296 boolean (*write_armap)
297 PARAMS ((bfd *, unsigned int, struct orl *, unsigned int, int));
298 PTR (*_bfd_read_ar_hdr_fn) PARAMS ((bfd *));
299 bfd * (*openr_next_archived_file) PARAMS ((bfd *, bfd *));
300 #define bfd_get_elt_at_index(b,i) BFD_SEND(b, _bfd_get_elt_at_index, (b,i))
301 bfd * (*_bfd_get_elt_at_index) PARAMS ((bfd *, symindex));
302 int (*_bfd_stat_arch_elt) PARAMS ((bfd *, struct stat *));
303 boolean (*_bfd_update_armap_timestamp) PARAMS ((bfd *));
305 /* Entry points used for symbols. */
306 #define BFD_JUMP_TABLE_SYMBOLS(NAME) \
307 CONCAT2 (NAME,_get_symtab_upper_bound), \
308 CONCAT2 (NAME,_get_symtab), \
309 CONCAT2 (NAME,_make_empty_symbol), \
310 CONCAT2 (NAME,_print_symbol), \
311 CONCAT2 (NAME,_get_symbol_info), \
312 CONCAT2 (NAME,_bfd_is_local_label_name), \
313 CONCAT2 (NAME,_get_lineno), \
314 CONCAT2 (NAME,_find_nearest_line), \
315 CONCAT2 (NAME,_bfd_make_debug_symbol), \
316 CONCAT2 (NAME,_read_minisymbols), \
317 CONCAT2 (NAME,_minisymbol_to_symbol)
318 long (*_bfd_get_symtab_upper_bound) PARAMS ((bfd *));
319 long (*_bfd_canonicalize_symtab) PARAMS ((bfd *,
320 struct symbol_cache_entry **));
321 struct symbol_cache_entry *
322 (*_bfd_make_empty_symbol) PARAMS ((bfd *));
323 void (*_bfd_print_symbol) PARAMS ((bfd *, PTR,
324 struct symbol_cache_entry *,
325 bfd_print_symbol_type));
326 #define bfd_print_symbol(b,p,s,e) BFD_SEND(b, _bfd_print_symbol, (b,p,s,e))
327 void (*_bfd_get_symbol_info) PARAMS ((bfd *,
328 struct symbol_cache_entry *,
330 #define bfd_get_symbol_info(b,p,e) BFD_SEND(b, _bfd_get_symbol_info, (b,p,e))
331 boolean (*_bfd_is_local_label_name) PARAMS ((bfd *, const char *));
333 alent * (*_get_lineno) PARAMS ((bfd *, struct symbol_cache_entry *));
334 boolean (*_bfd_find_nearest_line)
335 PARAMS ((bfd *, struct sec *, struct symbol_cache_entry **, bfd_vma,
336 const char **, const char **, unsigned int *));
337 /* Back-door to allow format-aware applications to create debug symbols
338 while using BFD for everything else. Currently used by the assembler
339 when creating COFF files. */
340 asymbol *(*_bfd_make_debug_symbol) PARAMS ((bfd *, void *,
341 unsigned long size));
342 #define bfd_read_minisymbols(b, d, m, s) \
343 BFD_SEND (b, _read_minisymbols, (b, d, m, s))
344 long (*_read_minisymbols) PARAMS ((bfd *, boolean, PTR *,
346 #define bfd_minisymbol_to_symbol(b, d, m, f) \
347 BFD_SEND (b, _minisymbol_to_symbol, (b, d, m, f))
348 asymbol *(*_minisymbol_to_symbol) PARAMS ((bfd *, boolean, const PTR,
351 /* Routines for relocs. */
352 #define BFD_JUMP_TABLE_RELOCS(NAME) \
353 CONCAT2 (NAME,_get_reloc_upper_bound), \
354 CONCAT2 (NAME,_canonicalize_reloc), \
355 CONCAT2 (NAME,_bfd_reloc_type_lookup)
356 long (*_get_reloc_upper_bound) PARAMS ((bfd *, sec_ptr));
357 long (*_bfd_canonicalize_reloc) PARAMS ((bfd *, sec_ptr, arelent **,
358 struct symbol_cache_entry **));
359 /* See documentation on reloc types. */
361 (*reloc_type_lookup) PARAMS ((bfd *, bfd_reloc_code_real_type));
363 /* Routines used when writing an object file. */
364 #define BFD_JUMP_TABLE_WRITE(NAME) \
365 CONCAT2 (NAME,_set_arch_mach), \
366 CONCAT2 (NAME,_set_section_contents)
367 boolean (*_bfd_set_arch_mach) PARAMS ((bfd *, enum bfd_architecture,
369 boolean (*_bfd_set_section_contents) PARAMS ((bfd *, sec_ptr, PTR,
370 file_ptr, bfd_size_type));
372 /* Routines used by the linker. */
373 #define BFD_JUMP_TABLE_LINK(NAME) \
374 CONCAT2 (NAME,_sizeof_headers), \
375 CONCAT2 (NAME,_bfd_get_relocated_section_contents), \
376 CONCAT2 (NAME,_bfd_relax_section), \
377 CONCAT2 (NAME,_bfd_link_hash_table_create), \
378 CONCAT2 (NAME,_bfd_link_add_symbols), \
379 CONCAT2 (NAME,_bfd_final_link), \
380 CONCAT2 (NAME,_bfd_link_split_section), \
381 CONCAT2 (NAME,_bfd_gc_sections), \
382 CONCAT2 (NAME,_bfd_merge_sections)
383 int (*_bfd_sizeof_headers) PARAMS ((bfd *, boolean));
384 bfd_byte *(*_bfd_get_relocated_section_contents)
385 PARAMS ((bfd *, struct bfd_link_info *, struct bfd_link_order *,
386 bfd_byte *, boolean, struct symbol_cache_entry **));
388 boolean (*_bfd_relax_section)
389 PARAMS ((bfd *, struct sec *, struct bfd_link_info *, boolean *));
391 /* Create a hash table for the linker. Different backends store
392 different information in this table. */
393 struct bfd_link_hash_table *(*_bfd_link_hash_table_create) PARAMS ((bfd *));
395 /* Add symbols from this object file into the hash table. */
396 boolean (*_bfd_link_add_symbols) PARAMS ((bfd *, struct bfd_link_info *));
398 /* Do a link based on the link_order structures attached to each
399 section of the BFD. */
400 boolean (*_bfd_final_link) PARAMS ((bfd *, struct bfd_link_info *));
402 /* Should this section be split up into smaller pieces during linking. */
403 boolean (*_bfd_link_split_section) PARAMS ((bfd *, struct sec *));
405 /* Remove sections that are not referenced from the output. */
406 boolean (*_bfd_gc_sections) PARAMS ((bfd *, struct bfd_link_info *));
408 /* Attempt to merge SEC_MERGE sections. */
409 boolean (*_bfd_merge_sections) PARAMS ((bfd *, struct bfd_link_info *));
411 /* Routines to handle dynamic symbols and relocs. */
412 #define BFD_JUMP_TABLE_DYNAMIC(NAME) \
413 CONCAT2 (NAME,_get_dynamic_symtab_upper_bound), \
414 CONCAT2 (NAME,_canonicalize_dynamic_symtab), \
415 CONCAT2 (NAME,_get_dynamic_reloc_upper_bound), \
416 CONCAT2 (NAME,_canonicalize_dynamic_reloc)
417 /* Get the amount of memory required to hold the dynamic symbols. */
418 long (*_bfd_get_dynamic_symtab_upper_bound) PARAMS ((bfd *));
419 /* Read in the dynamic symbols. */
420 long (*_bfd_canonicalize_dynamic_symtab)
421 PARAMS ((bfd *, struct symbol_cache_entry **));
422 /* Get the amount of memory required to hold the dynamic relocs. */
423 long (*_bfd_get_dynamic_reloc_upper_bound) PARAMS ((bfd *));
424 /* Read in the dynamic relocs. */
425 long (*_bfd_canonicalize_dynamic_reloc)
426 PARAMS ((bfd *, arelent **, struct symbol_cache_entry **));
429 A pointer to an alternative bfd_target in case the current one is not
430 satisfactory. This can happen when the target cpu supports both big
431 and little endian code, and target chosen by the linker has the wrong
432 endianness. The function open_output() in ld/ldlang.c uses this field
433 to find an alternative output format that is suitable.
435 /* Opposite endian version of this target. */
436 const struct bfd_target * alternative_target;
438 /* Data for use by back-end routines, which isn't
439 generic enough to belong in this structure. */
446 @findex bfd_set_default_target
447 @subsubsection @code{bfd_set_default_target}
450 boolean bfd_set_default_target (const char *name);
452 @strong{Description}@*
453 Set the default target vector to use when recognizing a BFD.
454 This takes the name of the target, which may be a BFD target
455 name or a configuration triplet.
457 @findex bfd_find_target
458 @subsubsection @code{bfd_find_target}
461 const bfd_target *bfd_find_target(const char *target_name, bfd *abfd);
463 @strong{Description}@*
464 Return a pointer to the transfer vector for the object target
465 named @var{target_name}. If @var{target_name} is @code{NULL}, choose the
466 one in the environment variable @code{GNUTARGET}; if that is null or not
467 defined, then choose the first entry in the target list.
468 Passing in the string "default" or setting the environment
469 variable to "default" will cause the first entry in the target
470 list to be returned, and "target_defaulted" will be set in the
471 BFD. This causes @code{bfd_check_format} to loop over all the
472 targets to find the one that matches the file being read.
474 @findex bfd_target_list
475 @subsubsection @code{bfd_target_list}
478 const char **bfd_target_list(void);
480 @strong{Description}@*
481 Return a freshly malloced NULL-terminated
482 vector of the names of all the valid BFD targets. Do not
485 @findex bfd_seach_for_target
486 @subsubsection @code{bfd_seach_for_target}
489 const bfd_target * bfd_search_for_target (int (* search_func) (const bfd_target *, void *), void *);
491 @strong{Description}@*
492 Return a pointer to the first transfer vector in the list of
493 transfer vectors maintained by BFD that produces a non-zero
494 result when passed to the function @var{search_func}. The
495 parameter @var{data} is passed, unexamined, to the search