Info Node: (bfd.info)BFD front end

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(bfd.info)BFD front end

BFD front end ************* `typedef bfd' ============= A BFD has type `bfd'; objects of this type are the cornerstone of any application using BFD. Using BFD consists of making references though the BFD and to data in the BFD. Here is the structure that defines the type `bfd'. It contains the major data about the file and pointers to the rest of the data. struct _bfd { /* The filename the application opened the BFD with. */ const char *filename; /* A pointer to the target jump table. */ const struct bfd_target *xvec; /* To avoid dragging too many header files into every file that includes ``bfd.h'', IOSTREAM has been declared as a "char *", and MTIME as a "long". Their correct types, to which they are cast when used, are "FILE *" and "time_t". The iostream is the result of an fopen on the filename. However, if the BFD_IN_MEMORY flag is set, then iostream is actually a pointer to a bfd_in_memory struct. */ PTR iostream; /* Is the file descriptor being cached? That is, can it be closed as needed, and re-opened when accessed later? */ boolean cacheable; /* Marks whether there was a default target specified when the BFD was opened. This is used to select which matching algorithm to use to choose the back end. */ boolean target_defaulted; /* The caching routines use these to maintain a least-recently-used list of BFDs. */ struct _bfd *lru_prev, *lru_next; /* When a file is closed by the caching routines, BFD retains state information on the file here... */ ufile_ptr where; /* ... and here: (``once'' means at least once). */ boolean opened_once; /* Set if we have a locally maintained mtime value, rather than getting it from the file each time. */ boolean mtime_set; /* File modified time, if mtime_set is true. */ long mtime; /* Reserved for an unimplemented file locking extension. */ int ifd; /* The format which belongs to the BFD. (object, core, etc.) */ bfd_format format; /* The direction with which the BFD was opened. */ enum bfd_direction { no_direction = 0, read_direction = 1, write_direction = 2, both_direction = 3 } direction; /* Format_specific flags. */ flagword flags; /* Currently my_archive is tested before adding origin to anything. I believe that this can become always an add of origin, with origin set to 0 for non archive files. */ ufile_ptr origin; /* Remember when output has begun, to stop strange things from happening. */ boolean output_has_begun; /* A hash table for section names. */ struct bfd_hash_table section_htab; /* Pointer to linked list of sections. */ struct sec *sections; /* The place where we add to the section list. */ struct sec **section_tail; /* The number of sections. */ unsigned int section_count; /* Stuff only useful for object files: The start address. */ bfd_vma start_address; /* Used for input and output. */ unsigned int symcount; /* Symbol table for output BFD (with symcount entries). */ struct symbol_cache_entry **outsymbols; /* Pointer to structure which contains architecture information. */ const struct bfd_arch_info *arch_info; /* Stuff only useful for archives. */ PTR arelt_data; struct _bfd *my_archive; /* The containing archive BFD. */ struct _bfd *next; /* The next BFD in the archive. */ struct _bfd *archive_head; /* The first BFD in the archive. */ boolean has_armap; /* A chain of BFD structures involved in a link. */ struct _bfd *link_next; /* A field used by _bfd_generic_link_add_archive_symbols. This will be used only for archive elements. */ int archive_pass; /* Used by the back end to hold private data. */ union { struct aout_data_struct *aout_data; struct artdata *aout_ar_data; struct _oasys_data *oasys_obj_data; struct _oasys_ar_data *oasys_ar_data; struct coff_tdata *coff_obj_data; struct pe_tdata *pe_obj_data; struct xcoff_tdata *xcoff_obj_data; struct ecoff_tdata *ecoff_obj_data; struct ieee_data_struct *ieee_data; struct ieee_ar_data_struct *ieee_ar_data; struct srec_data_struct *srec_data; struct ihex_data_struct *ihex_data; struct tekhex_data_struct *tekhex_data; struct elf_obj_tdata *elf_obj_data; struct nlm_obj_tdata *nlm_obj_data; struct bout_data_struct *bout_data; struct mmo_data_struct *mmo_data; struct sun_core_struct *sun_core_data; struct sco5_core_struct *sco5_core_data; struct trad_core_struct *trad_core_data; struct som_data_struct *som_data; struct hpux_core_struct *hpux_core_data; struct hppabsd_core_struct *hppabsd_core_data; struct sgi_core_struct *sgi_core_data; struct lynx_core_struct *lynx_core_data; struct osf_core_struct *osf_core_data; struct cisco_core_struct *cisco_core_data; struct versados_data_struct *versados_data; struct netbsd_core_struct *netbsd_core_data; PTR any; } tdata; /* Used by the application to hold private data. */ PTR usrdata; /* Where all the allocated stuff under this BFD goes. This is a struct objalloc *, but we use PTR to avoid requiring the inclusion of objalloc.h. */ PTR memory; }; Error reporting =============== Most BFD functions return nonzero on success (check their individual documentation for precise semantics). On an error, they call `bfd_set_error' to set an error condition that callers can check by calling `bfd_get_error'. If that returns `bfd_error_system_call', then check `errno'. The easiest way to report a BFD error to the user is to use `bfd_perror'. Type `bfd_error_type' --------------------- The values returned by `bfd_get_error' are defined by the enumerated type `bfd_error_type'. typedef enum bfd_error { bfd_error_no_error = 0, bfd_error_system_call, bfd_error_invalid_target, bfd_error_wrong_format, bfd_error_wrong_object_format, bfd_error_invalid_operation, bfd_error_no_memory, bfd_error_no_symbols, bfd_error_no_armap, bfd_error_no_more_archived_files, bfd_error_malformed_archive, bfd_error_file_not_recognized, bfd_error_file_ambiguously_recognized, bfd_error_no_contents, bfd_error_nonrepresentable_section, bfd_error_no_debug_section, bfd_error_bad_value, bfd_error_file_truncated, bfd_error_file_too_big, bfd_error_invalid_error_code } bfd_error_type; `bfd_get_error' ............... *Synopsis* bfd_error_type bfd_get_error (void); *Description* Return the current BFD error condition. `bfd_set_error' ............... *Synopsis* void bfd_set_error (bfd_error_type error_tag); *Description* Set the BFD error condition to be ERROR_TAG. `bfd_errmsg' ............ *Synopsis* const char *bfd_errmsg (bfd_error_type error_tag); *Description* Return a string describing the error ERROR_TAG, or the system error if ERROR_TAG is `bfd_error_system_call'. `bfd_perror' ............ *Synopsis* void bfd_perror (const char *message); *Description* Print to the standard error stream a string describing the last BFD error that occurred, or the last system error if the last BFD error was a system call failure. If MESSAGE is non-NULL and non-empty, the error string printed is preceded by MESSAGE, a colon, and a space. It is followed by a newline. BFD error handler ----------------- Some BFD functions want to print messages describing the problem. They call a BFD error handler function. This function may be overriden by the program. The BFD error handler acts like printf. typedef void (*bfd_error_handler_type) PARAMS ((const char *, ...)); `bfd_set_error_handler' ....................... *Synopsis* bfd_error_handler_type bfd_set_error_handler (bfd_error_handler_type); *Description* Set the BFD error handler function. Returns the previous function. `bfd_set_error_program_name' ............................ *Synopsis* void bfd_set_error_program_name (const char *); *Description* Set the program name to use when printing a BFD error. This is printed before the error message followed by a colon and space. The string must not be changed after it is passed to this function. `bfd_get_error_handler' ....................... *Synopsis* bfd_error_handler_type bfd_get_error_handler (void); *Description* Return the BFD error handler function. `bfd_archive_filename' ...................... *Synopsis* const char *bfd_archive_filename (bfd *); *Description* For a BFD that is a component of an archive, returns a string with both the archive name and file name. For other BFDs, just returns the file name. Symbols ======= `bfd_get_reloc_upper_bound' ........................... *Synopsis* long bfd_get_reloc_upper_bound(bfd *abfd, asection *sect); *Description* Return the number of bytes required to store the relocation information associated with section SECT attached to bfd ABFD. If an error occurs, return -1. `bfd_canonicalize_reloc' ........................ *Synopsis* long bfd_canonicalize_reloc (bfd *abfd, asection *sec, arelent **loc, asymbol **syms); *Description* Call the back end associated with the open BFD ABFD and translate the external form of the relocation information attached to SEC into the internal canonical form. Place the table into memory at LOC, which has been preallocated, usually by a call to `bfd_get_reloc_upper_bound'. Returns the number of relocs, or -1 on error. The SYMS table is also needed for horrible internal magic reasons. `bfd_set_reloc' ............... *Synopsis* void bfd_set_reloc (bfd *abfd, asection *sec, arelent **rel, unsigned int count); *Description* Set the relocation pointer and count within section SEC to the values REL and COUNT. The argument ABFD is ignored. `bfd_set_file_flags' .................... *Synopsis* boolean bfd_set_file_flags(bfd *abfd, flagword flags); *Description* Set the flag word in the BFD ABFD to the value FLAGS. Possible errors are: * `bfd_error_wrong_format' - The target bfd was not of object format. * `bfd_error_invalid_operation' - The target bfd was open for reading. * `bfd_error_invalid_operation' - The flag word contained a bit which was not applicable to the type of file. E.g., an attempt was made to set the `D_PAGED' bit on a BFD format which does not support demand paging. `bfd_get_arch_size' ................... *Synopsis* int bfd_get_arch_size (bfd *abfd); *Description* Returns the architecture address size, in bits, as determined by the object file's format. For ELF, this information is included in the header. *Returns* Returns the arch size in bits if known, `-1' otherwise. `bfd_get_sign_extend_vma' ......................... *Synopsis* int bfd_get_sign_extend_vma (bfd *abfd); *Description* Indicates if the target architecture "naturally" sign extends an address. Some architectures implicitly sign extend address values when they are converted to types larger than the size of an address. For instance, bfd_get_start_address() will return an address sign extended to fill a bfd_vma when this is the case. *Returns* Returns `1' if the target architecture is known to sign extend addresses, `0' if the target architecture is known to not sign extend addresses, and `-1' otherwise. `bfd_set_start_address' ....................... *Synopsis* boolean bfd_set_start_address(bfd *abfd, bfd_vma vma); *Description* Make VMA the entry point of output BFD ABFD. *Returns* Returns `true' on success, `false' otherwise. `bfd_get_mtime' ............... *Synopsis* long bfd_get_mtime(bfd *abfd); *Description* Return the file modification time (as read from the file system, or from the archive header for archive members). `bfd_get_size' .............. *Synopsis* long bfd_get_size(bfd *abfd); *Description* Return the file size (as read from file system) for the file associated with BFD ABFD. The initial motivation for, and use of, this routine is not so we can get the exact size of the object the BFD applies to, since that might not be generally possible (archive members for example). It would be ideal if someone could eventually modify it so that such results were guaranteed. Instead, we want to ask questions like "is this NNN byte sized object I'm about to try read from file offset YYY reasonable?" As as example of where we might do this, some object formats use string tables for which the first `sizeof (long)' bytes of the table contain the size of the table itself, including the size bytes. If an application tries to read what it thinks is one of these string tables, without some way to validate the size, and for some reason the size is wrong (byte swapping error, wrong location for the string table, etc.), the only clue is likely to be a read error when it tries to read the table, or a "virtual memory exhausted" error when it tries to allocate 15 bazillon bytes of space for the 15 bazillon byte table it is about to read. This function at least allows us to answer the quesion, "is the size reasonable?". `bfd_get_gp_size' ................. *Synopsis* unsigned int bfd_get_gp_size(bfd *abfd); *Description* Return the maximum size of objects to be optimized using the GP register under MIPS ECOFF. This is typically set by the `-G' argument to the compiler, assembler or linker. `bfd_set_gp_size' ................. *Synopsis* void bfd_set_gp_size(bfd *abfd, unsigned int i); *Description* Set the maximum size of objects to be optimized using the GP register under ECOFF or MIPS ELF. This is typically set by the `-G' argument to the compiler, assembler or linker. `bfd_scan_vma' .............. *Synopsis* bfd_vma bfd_scan_vma(const char *string, const char **end, int base); *Description* Convert, like `strtoul', a numerical expression STRING into a `bfd_vma' integer, and return that integer. (Though without as many bells and whistles as `strtoul'.) The expression is assumed to be unsigned (i.e., positive). If given a BASE, it is used as the base for conversion. A base of 0 causes the function to interpret the string in hex if a leading "0x" or "0X" is found, otherwise in octal if a leading zero is found, otherwise in decimal. If the value would overflow, the maximum `bfd_vma' value is returned. `bfd_copy_private_bfd_data' ........................... *Synopsis* boolean bfd_copy_private_bfd_data(bfd *ibfd, bfd *obfd); *Description* Copy private BFD information from the BFD IBFD to the the BFD OBFD. Return `true' on success, `false' on error. Possible error returns are: * `bfd_error_no_memory' - Not enough memory exists to create private data for OBFD. #define bfd_copy_private_bfd_data(ibfd, obfd) \ BFD_SEND (obfd, _bfd_copy_private_bfd_data, \ (ibfd, obfd)) `bfd_merge_private_bfd_data' ............................ *Synopsis* boolean bfd_merge_private_bfd_data(bfd *ibfd, bfd *obfd); *Description* Merge private BFD information from the BFD IBFD to the the output file BFD OBFD when linking. Return `true' on success, `false' on error. Possible error returns are: * `bfd_error_no_memory' - Not enough memory exists to create private data for OBFD. #define bfd_merge_private_bfd_data(ibfd, obfd) \ BFD_SEND (obfd, _bfd_merge_private_bfd_data, \ (ibfd, obfd)) `bfd_set_private_flags' ....................... *Synopsis* boolean bfd_set_private_flags(bfd *abfd, flagword flags); *Description* Set private BFD flag information in the BFD ABFD. Return `true' on success, `false' on error. Possible error returns are: * `bfd_error_no_memory' - Not enough memory exists to create private data for OBFD. #define bfd_set_private_flags(abfd, flags) \ BFD_SEND (abfd, _bfd_set_private_flags, \ (abfd, flags)) `stuff' ....... *Description* Stuff which should be documented: #define bfd_sizeof_headers(abfd, reloc) \ BFD_SEND (abfd, _bfd_sizeof_headers, (abfd, reloc)) #define bfd_find_nearest_line(abfd, sec, syms, off, file, func, line) \ BFD_SEND (abfd, _bfd_find_nearest_line, (abfd, sec, syms, off, file, func, line)) /* Do these three do anything useful at all, for any back end? */ #define bfd_debug_info_start(abfd) \ BFD_SEND (abfd, _bfd_debug_info_start, (abfd)) #define bfd_debug_info_end(abfd) \ BFD_SEND (abfd, _bfd_debug_info_end, (abfd)) #define bfd_debug_info_accumulate(abfd, section) \ BFD_SEND (abfd, _bfd_debug_info_accumulate, (abfd, section)) #define bfd_stat_arch_elt(abfd, stat) \ BFD_SEND (abfd, _bfd_stat_arch_elt,(abfd, stat)) #define bfd_update_armap_timestamp(abfd) \ BFD_SEND (abfd, _bfd_update_armap_timestamp, (abfd)) #define bfd_set_arch_mach(abfd, arch, mach)\ BFD_SEND ( abfd, _bfd_set_arch_mach, (abfd, arch, mach)) #define bfd_relax_section(abfd, section, link_info, again) \ BFD_SEND (abfd, _bfd_relax_section, (abfd, section, link_info, again)) #define bfd_gc_sections(abfd, link_info) \ BFD_SEND (abfd, _bfd_gc_sections, (abfd, link_info)) #define bfd_merge_sections(abfd, link_info) \ BFD_SEND (abfd, _bfd_merge_sections, (abfd, link_info)) #define bfd_link_hash_table_create(abfd) \ BFD_SEND (abfd, _bfd_link_hash_table_create, (abfd)) #define bfd_link_add_symbols(abfd, info) \ BFD_SEND (abfd, _bfd_link_add_symbols, (abfd, info)) #define bfd_final_link(abfd, info) \ BFD_SEND (abfd, _bfd_final_link, (abfd, info)) #define bfd_free_cached_info(abfd) \ BFD_SEND (abfd, _bfd_free_cached_info, (abfd)) #define bfd_get_dynamic_symtab_upper_bound(abfd) \ BFD_SEND (abfd, _bfd_get_dynamic_symtab_upper_bound, (abfd)) #define bfd_print_private_bfd_data(abfd, file)\ BFD_SEND (abfd, _bfd_print_private_bfd_data, (abfd, file)) #define bfd_canonicalize_dynamic_symtab(abfd, asymbols) \ BFD_SEND (abfd, _bfd_canonicalize_dynamic_symtab, (abfd, asymbols)) #define bfd_get_dynamic_reloc_upper_bound(abfd) \ BFD_SEND (abfd, _bfd_get_dynamic_reloc_upper_bound, (abfd)) #define bfd_canonicalize_dynamic_reloc(abfd, arels, asyms) \ BFD_SEND (abfd, _bfd_canonicalize_dynamic_reloc, (abfd, arels, asyms)) extern bfd_byte *bfd_get_relocated_section_contents PARAMS ((bfd *, struct bfd_link_info *, struct bfd_link_order *, bfd_byte *, boolean, asymbol **)); `bfd_alt_mach_code' ................... *Synopsis* boolean bfd_alt_mach_code(bfd *abfd, int index); *Description* When more than one machine code number is available for the same machine type, this function can be used to switch between the preferred one (index == 0) and any others. Currently, only ELF supports this feature, with up to two alternate machine codes.

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