This is bfd.info, produced by makeinfo version 4.3 from bfd.texinfo. START-INFO-DIR-ENTRY * Bfd: (bfd). The Binary File Descriptor library. END-INFO-DIR-ENTRY This file documents the BFD library. Copyright (C) 1991, 2000, 2001, 2003 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".  File: bfd.info, Node: typedef asection, Next: section prototypes, Prev: Section Output, Up: Sections typedef asection ---------------- Here is the section structure: /* This structure is used for a comdat section, as in PE. A comdat section is associated with a particular symbol. When the linker sees a comdat section, it keeps only one of the sections with a given name and associated with a given symbol. */ struct bfd_comdat_info { /* The name of the symbol associated with a comdat section. */ const char *name; /* The local symbol table index of the symbol associated with a comdat section. This is only meaningful to the object file format specific code; it is not an index into the list returned by bfd_canonicalize_symtab. */ long symbol; }; typedef struct sec { /* The name of the section; the name isn't a copy, the pointer is the same as that passed to bfd_make_section. */ const char *name; /* A unique sequence number. */ int id; /* Which section in the bfd; 0..n-1 as sections are created in a bfd. */ int index; /* The next section in the list belonging to the BFD, or NULL. */ struct sec *next; /* The field flags contains attributes of the section. Some flags are read in from the object file, and some are synthesized from other information. */ flagword flags; #define SEC_NO_FLAGS 0x000 /* Tells the OS to allocate space for this section when loading. This is clear for a section containing debug information only. */ #define SEC_ALLOC 0x001 /* Tells the OS to load the section from the file when loading. This is clear for a .bss section. */ #define SEC_LOAD 0x002 /* The section contains data still to be relocated, so there is some relocation information too. */ #define SEC_RELOC 0x004 /* ELF reserves 4 processor specific bits and 8 operating system specific bits in sh_flags; at present we can get away with just one in communicating between the assembler and BFD, but this isn't a good long-term solution. */ #define SEC_ARCH_BIT_0 0x008 /* A signal to the OS that the section contains read only data. */ #define SEC_READONLY 0x010 /* The section contains code only. */ #define SEC_CODE 0x020 /* The section contains data only. */ #define SEC_DATA 0x040 /* The section will reside in ROM. */ #define SEC_ROM 0x080 /* The section contains constructor information. This section type is used by the linker to create lists of constructors and destructors used by `g++'. When a back end sees a symbol which should be used in a constructor list, it creates a new section for the type of name (e.g., `__CTOR_LIST__'), attaches the symbol to it, and builds a relocation. To build the lists of constructors, all the linker has to do is catenate all the sections called `__CTOR_LIST__' and relocate the data contained within - exactly the operations it would peform on standard data. */ #define SEC_CONSTRUCTOR 0x100 /* The section has contents - a data section could be `SEC_ALLOC' | `SEC_HAS_CONTENTS'; a debug section could be `SEC_HAS_CONTENTS' */ #define SEC_HAS_CONTENTS 0x200 /* An instruction to the linker to not output the section even if it has information which would normally be written. */ #define SEC_NEVER_LOAD 0x400 /* The section is a COFF shared library section. This flag is only for the linker. If this type of section appears in the input file, the linker must copy it to the output file without changing the vma or size. FIXME: Although this was originally intended to be general, it really is COFF specific (and the flag was renamed to indicate this). It might be cleaner to have some more general mechanism to allow the back end to control what the linker does with sections. */ #define SEC_COFF_SHARED_LIBRARY 0x800 /* The section contains thread local data. */ #define SEC_THREAD_LOCAL 0x1000 /* The section has GOT references. This flag is only for the linker, and is currently only used by the elf32-hppa back end. It will be set if global offset table references were detected in this section, which indicate to the linker that the section contains PIC code, and must be handled specially when doing a static link. */ #define SEC_HAS_GOT_REF 0x4000 /* The section contains common symbols (symbols may be defined multiple times, the value of a symbol is the amount of space it requires, and the largest symbol value is the one used). Most targets have exactly one of these (which we translate to bfd_com_section_ptr), but ECOFF has two. */ #define SEC_IS_COMMON 0x8000 /* The section contains only debugging information. For example, this is set for ELF .debug and .stab sections. strip tests this flag to see if a section can be discarded. */ #define SEC_DEBUGGING 0x10000 /* The contents of this section are held in memory pointed to by the contents field. This is checked by bfd_get_section_contents, and the data is retrieved from memory if appropriate. */ #define SEC_IN_MEMORY 0x20000 /* The contents of this section are to be excluded by the linker for executable and shared objects unless those objects are to be further relocated. */ #define SEC_EXCLUDE 0x40000 /* The contents of this section are to be sorted based on the sum of the symbol and addend values specified by the associated relocation entries. Entries without associated relocation entries will be appended to the end of the section in an unspecified order. */ #define SEC_SORT_ENTRIES 0x80000 /* When linking, duplicate sections of the same name should be discarded, rather than being combined into a single section as is usually done. This is similar to how common symbols are handled. See SEC_LINK_DUPLICATES below. */ #define SEC_LINK_ONCE 0x100000 /* If SEC_LINK_ONCE is set, this bitfield describes how the linker should handle duplicate sections. */ #define SEC_LINK_DUPLICATES 0x600000 /* This value for SEC_LINK_DUPLICATES means that duplicate sections with the same name should simply be discarded. */ #define SEC_LINK_DUPLICATES_DISCARD 0x0 /* This value for SEC_LINK_DUPLICATES means that the linker should warn if there are any duplicate sections, although it should still only link one copy. */ #define SEC_LINK_DUPLICATES_ONE_ONLY 0x200000 /* This value for SEC_LINK_DUPLICATES means that the linker should warn if any duplicate sections are a different size. */ #define SEC_LINK_DUPLICATES_SAME_SIZE 0x400000 /* This value for SEC_LINK_DUPLICATES means that the linker should warn if any duplicate sections contain different contents. */ #define SEC_LINK_DUPLICATES_SAME_CONTENTS 0x600000 /* This section was created by the linker as part of dynamic relocation or other arcane processing. It is skipped when going through the first-pass output, trusting that someone else up the line will take care of it later. */ #define SEC_LINKER_CREATED 0x800000 /* This section should not be subject to garbage collection. */ #define SEC_KEEP 0x1000000 /* This section contains "short" data, and should be placed "near" the GP. */ #define SEC_SMALL_DATA 0x2000000 /* This section contains data which may be shared with other executables or shared objects. */ #define SEC_SHARED 0x4000000 /* When a section with this flag is being linked, then if the size of the input section is less than a page, it should not cross a page boundary. If the size of the input section is one page or more, it should be aligned on a page boundary. */ #define SEC_BLOCK 0x8000000 /* Conditionally link this section; do not link if there are no references found to any symbol in the section. */ #define SEC_CLINK 0x10000000 /* Attempt to merge identical entities in the section. Entity size is given in the entsize field. */ #define SEC_MERGE 0x20000000 /* If given with SEC_MERGE, entities to merge are zero terminated strings where entsize specifies character size instead of fixed size entries. */ #define SEC_STRINGS 0x40000000 /* This section contains data about section groups. */ #define SEC_GROUP 0x80000000 /* End of section flags. */ /* Some internal packed boolean fields. */ /* See the vma field. */ unsigned int user_set_vma : 1; /* Whether relocations have been processed. */ unsigned int reloc_done : 1; /* A mark flag used by some of the linker backends. */ unsigned int linker_mark : 1; /* Another mark flag used by some of the linker backends. Set for output sections that have an input section. */ unsigned int linker_has_input : 1; /* A mark flag used by some linker backends for garbage collection. */ unsigned int gc_mark : 1; /* The following flags are used by the ELF linker. */ /* Mark sections which have been allocated to segments. */ unsigned int segment_mark : 1; /* Type of sec_info information. */ unsigned int sec_info_type:3; #define ELF_INFO_TYPE_NONE 0 #define ELF_INFO_TYPE_STABS 1 #define ELF_INFO_TYPE_MERGE 2 #define ELF_INFO_TYPE_EH_FRAME 3 #define ELF_INFO_TYPE_JUST_SYMS 4 /* Nonzero if this section uses RELA relocations, rather than REL. */ unsigned int use_rela_p:1; /* Bits used by various backends. */ unsigned int has_tls_reloc:1; /* Nonzero if this section needs the relax finalize pass. */ unsigned int need_finalize_relax:1; /* Usused bits. */ unsigned int flag12:1; unsigned int flag13:1; unsigned int flag14:1; unsigned int flag15:1; unsigned int flag16:4; unsigned int flag20:4; unsigned int flag24:8; /* End of internal packed boolean fields. */ /* The virtual memory address of the section - where it will be at run time. The symbols are relocated against this. The user_set_vma flag is maintained by bfd; if it's not set, the backend can assign addresses (for example, in `a.out', where the default address for `.data' is dependent on the specific target and various flags). */ bfd_vma vma; /* The load address of the section - where it would be in a rom image; really only used for writing section header information. */ bfd_vma lma; /* The size of the section in octets, as it will be output. Contains a value even if the section has no contents (e.g., the size of `.bss'). This will be filled in after relocation. */ bfd_size_type _cooked_size; /* The original size on disk of the section, in octets. Normally this value is the same as the size, but if some relaxing has been done, then this value will be bigger. */ bfd_size_type _raw_size; /* If this section is going to be output, then this value is the offset in *bytes* into the output section of the first byte in the input section (byte ==> smallest addressable unit on the target). In most cases, if this was going to start at the 100th octet (8-bit quantity) in the output section, this value would be 100. However, if the target byte size is 16 bits (bfd_octets_per_byte is "2"), this value would be 50. */ bfd_vma output_offset; /* The output section through which to map on output. */ struct sec *output_section; /* The alignment requirement of the section, as an exponent of 2 - e.g., 3 aligns to 2^3 (or 8). */ unsigned int alignment_power; /* If an input section, a pointer to a vector of relocation records for the data in this section. */ struct reloc_cache_entry *relocation; /* If an output section, a pointer to a vector of pointers to relocation records for the data in this section. */ struct reloc_cache_entry **orelocation; /* The number of relocation records in one of the above. */ unsigned reloc_count; /* Information below is back end specific - and not always used or updated. */ /* File position of section data. */ file_ptr filepos; /* File position of relocation info. */ file_ptr rel_filepos; /* File position of line data. */ file_ptr line_filepos; /* Pointer to data for applications. */ PTR userdata; /* If the SEC_IN_MEMORY flag is set, this points to the actual contents. */ unsigned char *contents; /* Attached line number information. */ alent *lineno; /* Number of line number records. */ unsigned int lineno_count; /* Entity size for merging purposes. */ unsigned int entsize; /* Optional information about a COMDAT entry; NULL if not COMDAT. */ struct bfd_comdat_info *comdat; /* When a section is being output, this value changes as more linenumbers are written out. */ file_ptr moving_line_filepos; /* What the section number is in the target world. */ int target_index; PTR used_by_bfd; /* If this is a constructor section then here is a list of the relocations created to relocate items within it. */ struct relent_chain *constructor_chain; /* The BFD which owns the section. */ bfd *owner; /* A symbol which points at this section only. */ struct symbol_cache_entry *symbol; struct symbol_cache_entry **symbol_ptr_ptr; struct bfd_link_order *link_order_head; struct bfd_link_order *link_order_tail; } asection; /* These sections are global, and are managed by BFD. The application and target back end are not permitted to change the values in these sections. New code should use the section_ptr macros rather than referring directly to the const sections. The const sections may eventually vanish. */ #define BFD_ABS_SECTION_NAME "*ABS*" #define BFD_UND_SECTION_NAME "*UND*" #define BFD_COM_SECTION_NAME "*COM*" #define BFD_IND_SECTION_NAME "*IND*" /* The absolute section. */ extern const asection bfd_abs_section; #define bfd_abs_section_ptr ((asection *) &bfd_abs_section) #define bfd_is_abs_section(sec) ((sec) == bfd_abs_section_ptr) /* Pointer to the undefined section. */ extern const asection bfd_und_section; #define bfd_und_section_ptr ((asection *) &bfd_und_section) #define bfd_is_und_section(sec) ((sec) == bfd_und_section_ptr) /* Pointer to the common section. */ extern const asection bfd_com_section; #define bfd_com_section_ptr ((asection *) &bfd_com_section) /* Pointer to the indirect section. */ extern const asection bfd_ind_section; #define bfd_ind_section_ptr ((asection *) &bfd_ind_section) #define bfd_is_ind_section(sec) ((sec) == bfd_ind_section_ptr) #define bfd_is_const_section(SEC) \ ( ((SEC) == bfd_abs_section_ptr) \ || ((SEC) == bfd_und_section_ptr) \ || ((SEC) == bfd_com_section_ptr) \ || ((SEC) == bfd_ind_section_ptr)) extern const struct symbol_cache_entry * const bfd_abs_symbol; extern const struct symbol_cache_entry * const bfd_com_symbol; extern const struct symbol_cache_entry * const bfd_und_symbol; extern const struct symbol_cache_entry * const bfd_ind_symbol; #define bfd_get_section_size_before_reloc(section) \ ((section)->reloc_done ? (abort (), (bfd_size_type) 1) \ : (section)->_raw_size) #define bfd_get_section_size_after_reloc(section) \ ((section)->reloc_done ? (section)->_cooked_size \ : (abort (), (bfd_size_type) 1)) /* Macros to handle insertion and deletion of a bfd's sections. These only handle the list pointers, ie. do not adjust section_count, target_index etc. */ #define bfd_section_list_remove(ABFD, PS) \ do \ { \ asection **_ps = PS; \ asection *_s = *_ps; \ *_ps = _s->next; \ if (_s->next == NULL) \ (ABFD)->section_tail = _ps; \ } \ while (0) #define bfd_section_list_insert(ABFD, PS, S) \ do \ { \ asection **_ps = PS; \ asection *_s = S; \ _s->next = *_ps; \ *_ps = _s; \ if (_s->next == NULL) \ (ABFD)->section_tail = &_s->next; \ } \ while (0)  File: bfd.info, Node: section prototypes, Prev: typedef asection, Up: Sections Section prototypes ------------------ These are the functions exported by the section handling part of BFD. `bfd_section_list_clear' ........................ *Synopsis* void bfd_section_list_clear (bfd *); *Description* Clears the section list, and also resets the section count and hash table entries. `bfd_get_section_by_name' ......................... *Synopsis* asection *bfd_get_section_by_name(bfd *abfd, const char *name); *Description* Run through ABFD and return the one of the `asection's whose name matches NAME, otherwise `NULL'. *Note Sections::, for more information. This should only be used in special cases; the normal way to process all sections of a given name is to use `bfd_map_over_sections' and `strcmp' on the name (or better yet, base it on the section flags or something else) for each section. `bfd_get_unique_section_name' ............................. *Synopsis* char *bfd_get_unique_section_name(bfd *abfd, const char *templat, int *count); *Description* Invent a section name that is unique in ABFD by tacking a dot and a digit suffix onto the original TEMPLAT. If COUNT is non-NULL, then it specifies the first number tried as a suffix to generate a unique name. The value pointed to by COUNT will be incremented in this case. `bfd_make_section_old_way' .......................... *Synopsis* asection *bfd_make_section_old_way(bfd *abfd, const char *name); *Description* Create a new empty section called NAME and attach it to the end of the chain of sections for the BFD ABFD. An attempt to create a section with a name which is already in use returns its pointer without changing the section chain. It has the funny name since this is the way it used to be before it was rewritten.... Possible errors are: * `bfd_error_invalid_operation' - If output has already started for this BFD. * `bfd_error_no_memory' - If memory allocation fails. `bfd_make_section_anyway' ......................... *Synopsis* asection *bfd_make_section_anyway(bfd *abfd, const char *name); *Description* Create a new empty section called NAME and attach it to the end of the chain of sections for ABFD. Create a new section even if there is already a section with that name. Return `NULL' and set `bfd_error' on error; possible errors are: * `bfd_error_invalid_operation' - If output has already started for ABFD. * `bfd_error_no_memory' - If memory allocation fails. `bfd_make_section' .................. *Synopsis* asection *bfd_make_section(bfd *, const char *name); *Description* Like `bfd_make_section_anyway', but return `NULL' (without calling bfd_set_error ()) without changing the section chain if there is already a section named NAME. If there is an error, return `NULL' and set `bfd_error'. `bfd_set_section_flags' ....................... *Synopsis* bfd_boolean bfd_set_section_flags (bfd *abfd, asection *sec, flagword flags); *Description* Set the attributes of the section SEC in the BFD ABFD to the value FLAGS. Return `TRUE' on success, `FALSE' on error. Possible error returns are: * `bfd_error_invalid_operation' - The section cannot have one or more of the attributes requested. For example, a .bss section in `a.out' may not have the `SEC_HAS_CONTENTS' field set. `bfd_map_over_sections' ....................... *Synopsis* void bfd_map_over_sections(bfd *abfd, void (*func) (bfd *abfd, asection *sect, PTR obj), PTR obj); *Description* Call the provided function FUNC for each section attached to the BFD ABFD, passing OBJ as an argument. The function will be called as if by func(abfd, the_section, obj); This is the prefered method for iterating over sections; an alternative would be to use a loop: section *p; for (p = abfd->sections; p != NULL; p = p->next) func(abfd, p, ...) `bfd_set_section_size' ...................... *Synopsis* bfd_boolean bfd_set_section_size (bfd *abfd, asection *sec, bfd_size_type val); *Description* Set SEC to the size VAL. If the operation is ok, then `TRUE' is returned, else `FALSE'. Possible error returns: * `bfd_error_invalid_operation' - Writing has started to the BFD, so setting the size is invalid. `bfd_set_section_contents' .......................... *Synopsis* bfd_boolean bfd_set_section_contents (bfd *abfd, asection *section, PTR data, file_ptr offset, bfd_size_type count); *Description* Sets the contents of the section SECTION in BFD ABFD to the data starting in memory at DATA. The data is written to the output section starting at offset OFFSET for COUNT octets. Normally `TRUE' is returned, else `FALSE'. Possible error returns are: * `bfd_error_no_contents' - The output section does not have the `SEC_HAS_CONTENTS' attribute, so nothing can be written to it. * and some more too This routine is front end to the back end function `_bfd_set_section_contents'. `bfd_get_section_contents' .......................... *Synopsis* bfd_boolean bfd_get_section_contents (bfd *abfd, asection *section, PTR location, file_ptr offset, bfd_size_type count); *Description* Read data from SECTION in BFD ABFD into memory starting at LOCATION. The data is read at an offset of OFFSET from the start of the input section, and is read for COUNT bytes. If the contents of a constructor with the `SEC_CONSTRUCTOR' flag set are requested or if the section does not have the `SEC_HAS_CONTENTS' flag set, then the LOCATION is filled with zeroes. If no errors occur, `TRUE' is returned, else `FALSE'. `bfd_copy_private_section_data' ............................... *Synopsis* bfd_boolean bfd_copy_private_section_data (bfd *ibfd, asection *isec, bfd *obfd, asection *osec); *Description* Copy private section information from ISEC in the BFD IBFD to the section OSEC in 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 OSEC. #define bfd_copy_private_section_data(ibfd, isection, obfd, osection) \ BFD_SEND (obfd, _bfd_copy_private_section_data, \ (ibfd, isection, obfd, osection)) `_bfd_strip_section_from_output' ................................ *Synopsis* void _bfd_strip_section_from_output (struct bfd_link_info *info, asection *section); *Description* Remove SECTION from the output. If the output section becomes empty, remove it from the output bfd. This function won't actually do anything except twiddle flags if called too late in the linking process, when it's not safe to remove sections. `bfd_generic_discard_group' ........................... *Synopsis* bfd_boolean bfd_generic_discard_group (bfd *abfd, asection *group); *Description* Remove all members of GROUP from the output.  File: bfd.info, Node: Symbols, Next: Archives, Prev: Sections, Up: BFD front end Symbols ======= BFD tries to maintain as much symbol information as it can when it moves information from file to file. BFD passes information to applications though the `asymbol' structure. When the application requests the symbol table, BFD reads the table in the native form and translates parts of it into the internal format. To maintain more than the information passed to applications, some targets keep some information "behind the scenes" in a structure only the particular back end knows about. For example, the coff back end keeps the original symbol table structure as well as the canonical structure when a BFD is read in. On output, the coff back end can reconstruct the output symbol table so that no information is lost, even information unique to coff which BFD doesn't know or understand. If a coff symbol table were read, but were written through an a.out back end, all the coff specific information would be lost. The symbol table of a BFD is not necessarily read in until a canonicalize request is made. Then the BFD back end fills in a table provided by the application with pointers to the canonical information. To output symbols, the application provides BFD with a table of pointers to pointers to `asymbol's. This allows applications like the linker to output a symbol as it was read, since the "behind the scenes" information will be still available. * Menu: * Reading Symbols:: * Writing Symbols:: * Mini Symbols:: * typedef asymbol:: * symbol handling functions::  File: bfd.info, Node: Reading Symbols, Next: Writing Symbols, Prev: Symbols, Up: Symbols Reading symbols --------------- There are two stages to reading a symbol table from a BFD: allocating storage, and the actual reading process. This is an excerpt from an application which reads the symbol table: long storage_needed; asymbol **symbol_table; long number_of_symbols; long i; storage_needed = bfd_get_symtab_upper_bound (abfd); if (storage_needed < 0) FAIL if (storage_needed == 0) return; symbol_table = (asymbol **) xmalloc (storage_needed); ... number_of_symbols = bfd_canonicalize_symtab (abfd, symbol_table); if (number_of_symbols < 0) FAIL for (i = 0; i < number_of_symbols; i++) process_symbol (symbol_table[i]); All storage for the symbols themselves is in an objalloc connected to the BFD; it is freed when the BFD is closed.  File: bfd.info, Node: Writing Symbols, Next: Mini Symbols, Prev: Reading Symbols, Up: Symbols Writing symbols --------------- Writing of a symbol table is automatic when a BFD open for writing is closed. The application attaches a vector of pointers to pointers to symbols to the BFD being written, and fills in the symbol count. The close and cleanup code reads through the table provided and performs all the necessary operations. The BFD output code must always be provided with an "owned" symbol: one which has come from another BFD, or one which has been created using `bfd_make_empty_symbol'. Here is an example showing the creation of a symbol table with only one element: #include "bfd.h" int main (void) { bfd *abfd; asymbol *ptrs[2]; asymbol *new; abfd = bfd_openw ("foo","a.out-sunos-big"); bfd_set_format (abfd, bfd_object); new = bfd_make_empty_symbol (abfd); new->name = "dummy_symbol"; new->section = bfd_make_section_old_way (abfd, ".text"); new->flags = BSF_GLOBAL; new->value = 0x12345; ptrs[0] = new; ptrs[1] = (asymbol *)0; bfd_set_symtab (abfd, ptrs, 1); bfd_close (abfd); return 0; } ./makesym nm foo 00012345 A dummy_symbol Many formats cannot represent arbitary symbol information; for instance, the `a.out' object format does not allow an arbitary number of sections. A symbol pointing to a section which is not one of `.text', `.data' or `.bss' cannot be described.  File: bfd.info, Node: Mini Symbols, Next: typedef asymbol, Prev: Writing Symbols, Up: Symbols Mini Symbols ------------ Mini symbols provide read-only access to the symbol table. They use less memory space, but require more time to access. They can be useful for tools like nm or objdump, which may have to handle symbol tables of extremely large executables. The `bfd_read_minisymbols' function will read the symbols into memory in an internal form. It will return a `void *' pointer to a block of memory, a symbol count, and the size of each symbol. The pointer is allocated using `malloc', and should be freed by the caller when it is no longer needed. The function `bfd_minisymbol_to_symbol' will take a pointer to a minisymbol, and a pointer to a structure returned by `bfd_make_empty_symbol', and return a `asymbol' structure. The return value may or may not be the same as the value from `bfd_make_empty_symbol' which was passed in.  File: bfd.info, Node: typedef asymbol, Next: symbol handling functions, Prev: Mini Symbols, Up: Symbols typedef asymbol --------------- An `asymbol' has the form: typedef struct symbol_cache_entry { /* A pointer to the BFD which owns the symbol. This information is necessary so that a back end can work out what additional information (invisible to the application writer) is carried with the symbol. This field is *almost* redundant, since you can use section->owner instead, except that some symbols point to the global sections bfd_{abs,com,und}_section. This could be fixed by making these globals be per-bfd (or per-target-flavor). FIXME. */ struct bfd *the_bfd; /* Use bfd_asymbol_bfd(sym) to access this field. */ /* The text of the symbol. The name is left alone, and not copied; the application may not alter it. */ const char *name; /* The value of the symbol. This really should be a union of a numeric value with a pointer, since some flags indicate that a pointer to another symbol is stored here. */ symvalue value; /* Attributes of a symbol. */ #define BSF_NO_FLAGS 0x00 /* The symbol has local scope; `static' in `C'. The value is the offset into the section of the data. */ #define BSF_LOCAL 0x01 /* The symbol has global scope; initialized data in `C'. The value is the offset into the section of the data. */ #define BSF_GLOBAL 0x02 /* The symbol has global scope and is exported. The value is the offset into the section of the data. */ #define BSF_EXPORT BSF_GLOBAL /* No real difference. */ /* A normal C symbol would be one of: `BSF_LOCAL', `BSF_FORT_COMM', `BSF_UNDEFINED' or `BSF_GLOBAL'. */ /* The symbol is a debugging record. The value has an arbitary meaning, unless BSF_DEBUGGING_RELOC is also set. */ #define BSF_DEBUGGING 0x08 /* The symbol denotes a function entry point. Used in ELF, perhaps others someday. */ #define BSF_FUNCTION 0x10 /* Used by the linker. */ #define BSF_KEEP 0x20 #define BSF_KEEP_G 0x40 /* A weak global symbol, overridable without warnings by a regular global symbol of the same name. */ #define BSF_WEAK 0x80 /* This symbol was created to point to a section, e.g. ELF's STT_SECTION symbols. */ #define BSF_SECTION_SYM 0x100 /* The symbol used to be a common symbol, but now it is allocated. */ #define BSF_OLD_COMMON 0x200 /* The default value for common data. */ #define BFD_FORT_COMM_DEFAULT_VALUE 0 /* In some files the type of a symbol sometimes alters its location in an output file - ie in coff a `ISFCN' symbol which is also `C_EXT' symbol appears where it was declared and not at the end of a section. This bit is set by the target BFD part to convey this information. */ #define BSF_NOT_AT_END 0x400 /* Signal that the symbol is the label of constructor section. */ #define BSF_CONSTRUCTOR 0x800 /* Signal that the symbol is a warning symbol. The name is a warning. The name of the next symbol is the one to warn about; if a reference is made to a symbol with the same name as the next symbol, a warning is issued by the linker. */ #define BSF_WARNING 0x1000 /* Signal that the symbol is indirect. This symbol is an indirect pointer to the symbol with the same name as the next symbol. */ #define BSF_INDIRECT 0x2000 /* BSF_FILE marks symbols that contain a file name. This is used for ELF STT_FILE symbols. */ #define BSF_FILE 0x4000 /* Symbol is from dynamic linking information. */ #define BSF_DYNAMIC 0x8000 /* The symbol denotes a data object. Used in ELF, and perhaps others someday. */ #define BSF_OBJECT 0x10000 /* This symbol is a debugging symbol. The value is the offset into the section of the data. BSF_DEBUGGING should be set as well. */ #define BSF_DEBUGGING_RELOC 0x20000 /* This symbol is thread local. Used in ELF. */ #define BSF_THREAD_LOCAL 0x40000 flagword flags; /* A pointer to the section to which this symbol is relative. This will always be non NULL, there are special sections for undefined and absolute symbols. */ struct sec *section; /* Back end special data. */ union { PTR p; bfd_vma i; } udata; } asymbol;  File: bfd.info, Node: symbol handling functions, Prev: typedef asymbol, Up: Symbols Symbol handling functions ------------------------- `bfd_get_symtab_upper_bound' ............................ *Description* Return the number of bytes required to store a vector of pointers to `asymbols' for all the symbols in the BFD ABFD, including a terminal NULL pointer. If there are no symbols in the BFD, then return 0. If an error occurs, return -1. #define bfd_get_symtab_upper_bound(abfd) \ BFD_SEND (abfd, _bfd_get_symtab_upper_bound, (abfd)) `bfd_is_local_label' .................... *Synopsis* bfd_boolean bfd_is_local_label (bfd *abfd, asymbol *sym); *Description* Return TRUE if the given symbol SYM in the BFD ABFD is a compiler generated local label, else return FALSE. `bfd_is_local_label_name' ......................... *Synopsis* bfd_boolean bfd_is_local_label_name (bfd *abfd, const char *name); *Description* Return TRUE if a symbol with the name NAME in the BFD ABFD is a compiler generated local label, else return FALSE. This just checks whether the name has the form of a local label. #define bfd_is_local_label_name(abfd, name) \ BFD_SEND (abfd, _bfd_is_local_label_name, (abfd, name)) `bfd_canonicalize_symtab' ......................... *Description* Read the symbols from the BFD ABFD, and fills in the vector LOCATION with pointers to the symbols and a trailing NULL. Return the actual number of symbol pointers, not including the NULL. #define bfd_canonicalize_symtab(abfd, location) \ BFD_SEND (abfd, _bfd_canonicalize_symtab,\ (abfd, location)) `bfd_set_symtab' ................ *Synopsis* bfd_boolean bfd_set_symtab (bfd *abfd, asymbol **location, unsigned int count); *Description* Arrange that when the output BFD ABFD is closed, the table LOCATION of COUNT pointers to symbols will be written. `bfd_print_symbol_vandf' ........................ *Synopsis* void bfd_print_symbol_vandf (bfd *abfd, PTR file, asymbol *symbol); *Description* Print the value and flags of the SYMBOL supplied to the stream FILE. `bfd_make_empty_symbol' ....................... *Description* Create a new `asymbol' structure for the BFD ABFD and return a pointer to it. This routine is necessary because each back end has private information surrounding the `asymbol'. Building your own `asymbol' and pointing to it will not create the private information, and will cause problems later on. #define bfd_make_empty_symbol(abfd) \ BFD_SEND (abfd, _bfd_make_empty_symbol, (abfd)) `_bfd_generic_make_empty_symbol' ................................ *Synopsis* asymbol * _bfd_generic_make_empty_symbol (bfd *); *Description* Create a new `asymbol' structure for the BFD ABFD and return a pointer to it. Used by core file routines, binary back-end and anywhere else where no private info is needed. `bfd_make_debug_symbol' ....................... *Description* Create a new `asymbol' structure for the BFD ABFD, to be used as a debugging symbol. Further details of its use have yet to be worked out. #define bfd_make_debug_symbol(abfd,ptr,size) \ BFD_SEND (abfd, _bfd_make_debug_symbol, (abfd, ptr, size)) `bfd_decode_symclass' ..................... *Description* Return a character corresponding to the symbol class of SYMBOL, or '?' for an unknown class. *Synopsis* int bfd_decode_symclass (asymbol *symbol); `bfd_is_undefined_symclass' ........................... *Description* Returns non-zero if the class symbol returned by bfd_decode_symclass represents an undefined symbol. Returns zero otherwise. *Synopsis* bfd_boolean bfd_is_undefined_symclass (int symclass); `bfd_symbol_info' ................. *Description* Fill in the basic info about symbol that nm needs. Additional info may be added by the back-ends after calling this function. *Synopsis* void bfd_symbol_info (asymbol *symbol, symbol_info *ret); `bfd_copy_private_symbol_data' .............................. *Synopsis* bfd_boolean bfd_copy_private_symbol_data (bfd *ibfd, asymbol *isym, bfd *obfd, asymbol *osym); *Description* Copy private symbol information from ISYM in the BFD IBFD to the symbol OSYM in 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 OSEC. #define bfd_copy_private_symbol_data(ibfd, isymbol, obfd, osymbol) \ BFD_SEND (obfd, _bfd_copy_private_symbol_data, \ (ibfd, isymbol, obfd, osymbol))  File: bfd.info, Node: Archives, Next: Formats, Prev: Symbols, Up: BFD front end Archives ======== *Description* An archive (or library) is just another BFD. It has a symbol table, although there's not much a user program will do with it. The big difference between an archive BFD and an ordinary BFD is that the archive doesn't have sections. Instead it has a chain of BFDs that are considered its contents. These BFDs can be manipulated like any other. The BFDs contained in an archive opened for reading will all be opened for reading. You may put either input or output BFDs into an archive opened for output; they will be handled correctly when the archive is closed. Use `bfd_openr_next_archived_file' to step through the contents of an archive opened for input. You don't have to read the entire archive if you don't want to! Read it until you find what you want. Archive contents of output BFDs are chained through the `next' pointer in a BFD. The first one is findable through the `archive_head' slot of the archive. Set it with `bfd_set_archive_head' (q.v.). A given BFD may be in only one open output archive at a time. As expected, the BFD archive code is more general than the archive code of any given environment. BFD archives may contain files of different formats (e.g., a.out and coff) and even different architectures. You may even place archives recursively into archives! This can cause unexpected confusion, since some archive formats are more expressive than others. For instance, Intel COFF archives can preserve long filenames; SunOS a.out archives cannot. If you move a file from the first to the second format and back again, the filename may be truncated. Likewise, different a.out environments have different conventions as to how they truncate filenames, whether they preserve directory names in filenames, etc. When interoperating with native tools, be sure your files are homogeneous. Beware: most of these formats do not react well to the presence of spaces in filenames. We do the best we can, but can't always handle this case due to restrictions in the format of archives. Many Unix utilities are braindead in regards to spaces and such in filenames anyway, so this shouldn't be much of a restriction. Archives are supported in BFD in `archive.c'. `bfd_get_next_mapent' ..................... *Synopsis* symindex bfd_get_next_mapent(bfd *abfd, symindex previous, carsym **sym); *Description* Step through archive ABFD's symbol table (if it has one). Successively update SYM with the next symbol's information, returning that symbol's (internal) index into the symbol table. Supply `BFD_NO_MORE_SYMBOLS' as the PREVIOUS entry to get the first one; returns `BFD_NO_MORE_SYMBOLS' when you've already got the last one. A `carsym' is a canonical archive symbol. The only user-visible element is its name, a null-terminated string. `bfd_set_archive_head' ...................... *Synopsis* bfd_boolean bfd_set_archive_head(bfd *output, bfd *new_head); *Description* Set the head of the chain of BFDs contained in the archive OUTPUT to NEW_HEAD. `bfd_openr_next_archived_file' .............................. *Synopsis* bfd *bfd_openr_next_archived_file(bfd *archive, bfd *previous); *Description* Provided a BFD, ARCHIVE, containing an archive and NULL, open an input BFD on the first contained element and returns that. Subsequent calls should pass the archive and the previous return value to return a created BFD to the next contained element. NULL is returned when there are no more.  File: bfd.info, Node: Formats, Next: Relocations, Prev: Archives, Up: BFD front end File formats ============ A format is a BFD concept of high level file contents type. The formats supported by BFD are: * `bfd_object' The BFD may contain data, symbols, relocations and debug info. * `bfd_archive' The BFD contains other BFDs and an optional index. * `bfd_core' The BFD contains the result of an executable core dump. `bfd_check_format' .................. *Synopsis* bfd_boolean bfd_check_format (bfd *abfd, bfd_format format); *Description* Verify if the file attached to the BFD ABFD is compatible with the format FORMAT (i.e., one of `bfd_object', `bfd_archive' or `bfd_core'). If the BFD has been set to a specific target before the call, only the named target and format combination is checked. If the target has not been set, or has been set to `default', then all the known target backends is interrogated to determine a match. If the default target matches, it is used. If not, exactly one target must recognize the file, or an error results. The function returns `TRUE' on success, otherwise `FALSE' with one of the following error codes: * `bfd_error_invalid_operation' - if `format' is not one of `bfd_object', `bfd_archive' or `bfd_core'. * `bfd_error_system_call' - if an error occured during a read - even some file mismatches can cause bfd_error_system_calls. * `file_not_recognised' - none of the backends recognised the file format. * `bfd_error_file_ambiguously_recognized' - more than one backend recognised the file format. `bfd_check_format_matches' .......................... *Synopsis* bfd_boolean bfd_check_format_matches (bfd *abfd, bfd_format format, char ***matching); *Description* Like `bfd_check_format', except when it returns FALSE with `bfd_errno' set to `bfd_error_file_ambiguously_recognized'. In that case, if MATCHING is not NULL, it will be filled in with a NULL-terminated list of the names of the formats that matched, allocated with `malloc'. Then the user may choose a format and try again. When done with the list that MATCHING points to, the caller should free it. `bfd_set_format' ................ *Synopsis* bfd_boolean bfd_set_format (bfd *abfd, bfd_format format); *Description* This function sets the file format of the BFD ABFD to the format FORMAT. If the target set in the BFD does not support the format requested, the format is invalid, or the BFD is not open for writing, then an error occurs. `bfd_format_string' ................... *Synopsis* const char *bfd_format_string (bfd_format format); *Description* Return a pointer to a const string `invalid', `object', `archive', `core', or `unknown', depending upon the value of FORMAT.  File: bfd.info, Node: Relocations, Next: Core Files, Prev: Formats, Up: BFD front end Relocations =========== BFD maintains relocations in much the same way it maintains symbols: they are left alone until required, then read in en-masse and translated into an internal form. A common routine `bfd_perform_relocation' acts upon the canonical form to do the fixup. Relocations are maintained on a per section basis, while symbols are maintained on a per BFD basis. All that a back end has to do to fit the BFD interface is to create a `struct reloc_cache_entry' for each relocation in a particular section, and fill in the right bits of the structures. * Menu: * typedef arelent:: * howto manager::