| This is bfd.info, produced by makeinfo version 4.0 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 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 is it; 0..nth. */ |
| |
| 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 |
| |
| #if 0 /* Obsolete ? */ |
| #define SEC_BALIGN 0x008 |
| #endif |
| |
| /* 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 is a constructor, and should be placed at the |
| end of the text, data, or bss section(?). */ |
| #define SEC_CONSTRUCTOR_TEXT 0x1100 |
| #define SEC_CONSTRUCTOR_DATA 0x2100 |
| #define SEC_CONSTRUCTOR_BSS 0x3100 |
| |
| /* 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 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 by the |
| based on the address specified in the associated symbol |
| table. */ |
| #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 |
| |
| /* 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 a input section. */ |
| unsigned int linker_has_input : 1; |
| |
| /* A mark flag used by some linker backends for garbage collection. */ |
| unsigned int gc_mark : 1; |
| |
| /* Used by the ELF code to mark sections which have been allocated to segments. */ |
| unsigned int segment_mark : 1; |
| |
| /* 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; |
| |
| /* Optional information about a COMDAT entry; NULL if not COMDAT. */ |
| |
| struct bfd_comdat_info *comdat; |
| |
| /* Points to the kept section if this section is a link-once section, |
| and is discarded. */ |
| struct sec *kept_section; |
| |
| /* 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) |
| |
| 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)) |
| |
| |
| 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_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* |
| 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* |
| 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* |
| 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* |
| 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* |
| 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. INFO may be NULL; if it is not, it is |
| used to decide whether the output section is empty. |
| |
| |
| 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" |
| main() |
| { |
| 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); |
| } |
| |
| ./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 |
| |
| 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* |
| 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* |
| 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* |
| 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(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_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* |
| 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* |
| 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* |
| 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* |
| 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* |
| 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* |
| 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:: |
| |
