| 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 Free Software Foundation, Inc. |
| |
| Permission is granted to make and distribute verbatim copies of this |
| manual provided the copyright notice and this permission notice are |
| preserved on all copies. |
| |
| Permission is granted to copy and distribute modified versions of |
| this manual under the conditions for verbatim copying, subject to the |
| terms of the GNU General Public License, which includes the provision |
| that the entire resulting derived work is distributed under the terms |
| of a permission notice identical to this one. |
| |
| Permission is granted to copy and distribute translations of this |
| manual into another language, under the above conditions for modified |
| versions. |
| |
| |
| File: bfd.info, Node: coff, Next: elf, Prev: aout, Up: BFD back ends |
| |
| coff backends |
| ============= |
| |
| BFD supports a number of different flavours of coff format. The |
| major differences between formats are the sizes and alignments of |
| fields in structures on disk, and the occasional extra field. |
| |
| Coff in all its varieties is implemented with a few common files and |
| a number of implementation specific files. For example, The 88k bcs |
| coff format is implemented in the file `coff-m88k.c'. This file |
| `#include's `coff/m88k.h' which defines the external structure of the |
| coff format for the 88k, and `coff/internal.h' which defines the |
| internal structure. `coff-m88k.c' also defines the relocations used by |
| the 88k format *Note Relocations::. |
| |
| The Intel i960 processor version of coff is implemented in |
| `coff-i960.c'. This file has the same structure as `coff-m88k.c', |
| except that it includes `coff/i960.h' rather than `coff-m88k.h'. |
| |
| Porting to a new version of coff |
| -------------------------------- |
| |
| The recommended method is to select from the existing |
| implementations the version of coff which is most like the one you want |
| to use. For example, we'll say that i386 coff is the one you select, |
| and that your coff flavour is called foo. Copy `i386coff.c' to |
| `foocoff.c', copy `../include/coff/i386.h' to `../include/coff/foo.h', |
| and add the lines to `targets.c' and `Makefile.in' so that your new |
| back end is used. Alter the shapes of the structures in |
| `../include/coff/foo.h' so that they match what you need. You will |
| probably also have to add `#ifdef's to the code in `coff/internal.h' and |
| `coffcode.h' if your version of coff is too wild. |
| |
| You can verify that your new BFD backend works quite simply by |
| building `objdump' from the `binutils' directory, and making sure that |
| its version of what's going on and your host system's idea (assuming it |
| has the pretty standard coff dump utility, usually called `att-dump' or |
| just `dump') are the same. Then clean up your code, and send what |
| you've done to Cygnus. Then your stuff will be in the next release, and |
| you won't have to keep integrating it. |
| |
| How the coff backend works |
| -------------------------- |
| |
| File layout |
| ........... |
| |
| The Coff backend is split into generic routines that are applicable |
| to any Coff target and routines that are specific to a particular |
| target. The target-specific routines are further split into ones which |
| are basically the same for all Coff targets except that they use the |
| external symbol format or use different values for certain constants. |
| |
| The generic routines are in `coffgen.c'. These routines work for |
| any Coff target. They use some hooks into the target specific code; |
| the hooks are in a `bfd_coff_backend_data' structure, one of which |
| exists for each target. |
| |
| The essentially similar target-specific routines are in |
| `coffcode.h'. This header file includes executable C code. The |
| various Coff targets first include the appropriate Coff header file, |
| make any special defines that are needed, and then include `coffcode.h'. |
| |
| Some of the Coff targets then also have additional routines in the |
| target source file itself. |
| |
| For example, `coff-i960.c' includes `coff/internal.h' and |
| `coff/i960.h'. It then defines a few constants, such as `I960', and |
| includes `coffcode.h'. Since the i960 has complex relocation types, |
| `coff-i960.c' also includes some code to manipulate the i960 relocs. |
| This code is not in `coffcode.h' because it would not be used by any |
| other target. |
| |
| Bit twiddling |
| ............. |
| |
| Each flavour of coff supported in BFD has its own header file |
| describing the external layout of the structures. There is also an |
| internal description of the coff layout, in `coff/internal.h'. A major |
| function of the coff backend is swapping the bytes and twiddling the |
| bits to translate the external form of the structures into the normal |
| internal form. This is all performed in the `bfd_swap'_thing_direction |
| routines. Some elements are different sizes between different versions |
| of coff; it is the duty of the coff version specific include file to |
| override the definitions of various packing routines in `coffcode.h'. |
| E.g., the size of line number entry in coff is sometimes 16 bits, and |
| sometimes 32 bits. `#define'ing `PUT_LNSZ_LNNO' and `GET_LNSZ_LNNO' |
| will select the correct one. No doubt, some day someone will find a |
| version of coff which has a varying field size not catered to at the |
| moment. To port BFD, that person will have to add more `#defines'. |
| Three of the bit twiddling routines are exported to `gdb'; |
| `coff_swap_aux_in', `coff_swap_sym_in' and `coff_swap_lineno_in'. `GDB' |
| reads the symbol table on its own, but uses BFD to fix things up. More |
| of the bit twiddlers are exported for `gas'; `coff_swap_aux_out', |
| `coff_swap_sym_out', `coff_swap_lineno_out', `coff_swap_reloc_out', |
| `coff_swap_filehdr_out', `coff_swap_aouthdr_out', |
| `coff_swap_scnhdr_out'. `Gas' currently keeps track of all the symbol |
| table and reloc drudgery itself, thereby saving the internal BFD |
| overhead, but uses BFD to swap things on the way out, making cross |
| ports much safer. Doing so also allows BFD (and thus the linker) to |
| use the same header files as `gas', which makes one avenue to disaster |
| disappear. |
| |
| Symbol reading |
| .............. |
| |
| The simple canonical form for symbols used by BFD is not rich enough |
| to keep all the information available in a coff symbol table. The back |
| end gets around this problem by keeping the original symbol table |
| around, "behind the scenes". |
| |
| When a symbol table is requested (through a call to |
| `bfd_canonicalize_symtab'), a request gets through to |
| `coff_get_normalized_symtab'. This reads the symbol table from the coff |
| file and swaps all the structures inside into the internal form. It |
| also fixes up all the pointers in the table (represented in the file by |
| offsets from the first symbol in the table) into physical pointers to |
| elements in the new internal table. This involves some work since the |
| meanings of fields change depending upon context: a field that is a |
| pointer to another structure in the symbol table at one moment may be |
| the size in bytes of a structure at the next. Another pass is made |
| over the table. All symbols which mark file names (`C_FILE' symbols) |
| are modified so that the internal string points to the value in the |
| auxent (the real filename) rather than the normal text associated with |
| the symbol (`".file"'). |
| |
| At this time the symbol names are moved around. Coff stores all |
| symbols less than nine characters long physically within the symbol |
| table; longer strings are kept at the end of the file in the string |
| table. This pass moves all strings into memory and replaces them with |
| pointers to the strings. |
| |
| The symbol table is massaged once again, this time to create the |
| canonical table used by the BFD application. Each symbol is inspected |
| in turn, and a decision made (using the `sclass' field) about the |
| various flags to set in the `asymbol'. *Note Symbols::. The generated |
| canonical table shares strings with the hidden internal symbol table. |
| |
| Any linenumbers are read from the coff file too, and attached to the |
| symbols which own the functions the linenumbers belong to. |
| |
| Symbol writing |
| .............. |
| |
| Writing a symbol to a coff file which didn't come from a coff file |
| will lose any debugging information. The `asymbol' structure remembers |
| the BFD from which the symbol was taken, and on output the back end |
| makes sure that the same destination target as source target is present. |
| |
| When the symbols have come from a coff file then all the debugging |
| information is preserved. |
| |
| Symbol tables are provided for writing to the back end in a vector |
| of pointers to pointers. This allows applications like the linker to |
| accumulate and output large symbol tables without having to do too much |
| byte copying. |
| |
| This function runs through the provided symbol table and patches |
| each symbol marked as a file place holder (`C_FILE') to point to the |
| next file place holder in the list. It also marks each `offset' field |
| in the list with the offset from the first symbol of the current symbol. |
| |
| Another function of this procedure is to turn the canonical value |
| form of BFD into the form used by coff. Internally, BFD expects symbol |
| values to be offsets from a section base; so a symbol physically at |
| 0x120, but in a section starting at 0x100, would have the value 0x20. |
| Coff expects symbols to contain their final value, so symbols have |
| their values changed at this point to reflect their sum with their |
| owning section. This transformation uses the `output_section' field of |
| the `asymbol''s `asection' *Note Sections::. |
| |
| * `coff_mangle_symbols' |
| This routine runs though the provided symbol table and uses the |
| offsets generated by the previous pass and the pointers generated when |
| the symbol table was read in to create the structured hierachy required |
| by coff. It changes each pointer to a symbol into the index into the |
| symbol table of the asymbol. |
| |
| * `coff_write_symbols' |
| This routine runs through the symbol table and patches up the |
| symbols from their internal form into the coff way, calls the bit |
| twiddlers, and writes out the table to the file. |
| |
| `coff_symbol_type' |
| .................. |
| |
| *Description* |
| The hidden information for an `asymbol' is described in a |
| `combined_entry_type': |
| |
| |
| typedef struct coff_ptr_struct |
| { |
| |
| /* Remembers the offset from the first symbol in the file for |
| this symbol. Generated by coff_renumber_symbols. */ |
| unsigned int offset; |
| |
| /* Should the value of this symbol be renumbered. Used for |
| XCOFF C_BSTAT symbols. Set by coff_slurp_symbol_table. */ |
| unsigned int fix_value : 1; |
| |
| /* Should the tag field of this symbol be renumbered. |
| Created by coff_pointerize_aux. */ |
| unsigned int fix_tag : 1; |
| |
| /* Should the endidx field of this symbol be renumbered. |
| Created by coff_pointerize_aux. */ |
| unsigned int fix_end : 1; |
| |
| /* Should the x_csect.x_scnlen field be renumbered. |
| Created by coff_pointerize_aux. */ |
| unsigned int fix_scnlen : 1; |
| |
| /* Fix up an XCOFF C_BINCL/C_EINCL symbol. The value is the |
| index into the line number entries. Set by |
| coff_slurp_symbol_table. */ |
| unsigned int fix_line : 1; |
| |
| /* The container for the symbol structure as read and translated |
| from the file. */ |
| |
| union { |
| union internal_auxent auxent; |
| struct internal_syment syment; |
| } u; |
| } combined_entry_type; |
| |
| |
| /* Each canonical asymbol really looks like this: */ |
| |
| typedef struct coff_symbol_struct |
| { |
| /* The actual symbol which the rest of BFD works with */ |
| asymbol symbol; |
| |
| /* A pointer to the hidden information for this symbol */ |
| combined_entry_type *native; |
| |
| /* A pointer to the linenumber information for this symbol */ |
| struct lineno_cache_entry *lineno; |
| |
| /* Have the line numbers been relocated yet ? */ |
| boolean done_lineno; |
| } coff_symbol_type; |
| |
| `bfd_coff_backend_data' |
| ....................... |
| |
| /* COFF symbol classifications. */ |
| |
| enum coff_symbol_classification |
| { |
| /* Global symbol. */ |
| COFF_SYMBOL_GLOBAL, |
| /* Common symbol. */ |
| COFF_SYMBOL_COMMON, |
| /* Undefined symbol. */ |
| COFF_SYMBOL_UNDEFINED, |
| /* Local symbol. */ |
| COFF_SYMBOL_LOCAL, |
| /* PE section symbol. */ |
| COFF_SYMBOL_PE_SECTION |
| }; |
| Special entry points for gdb to swap in coff symbol table parts: |
| typedef struct |
| { |
| void (*_bfd_coff_swap_aux_in) PARAMS (( |
| bfd *abfd, |
| PTR ext, |
| int type, |
| int class, |
| int indaux, |
| int numaux, |
| PTR in)); |
| |
| void (*_bfd_coff_swap_sym_in) PARAMS (( |
| bfd *abfd , |
| PTR ext, |
| PTR in)); |
| |
| void (*_bfd_coff_swap_lineno_in) PARAMS (( |
| bfd *abfd, |
| PTR ext, |
| PTR in)); |
| Special entry points for gas to swap out coff parts: |
| unsigned int (*_bfd_coff_swap_aux_out) PARAMS (( |
| bfd *abfd, |
| PTR in, |
| int type, |
| int class, |
| int indaux, |
| int numaux, |
| PTR ext)); |
| |
| unsigned int (*_bfd_coff_swap_sym_out) PARAMS (( |
| bfd *abfd, |
| PTR in, |
| PTR ext)); |
| |
| unsigned int (*_bfd_coff_swap_lineno_out) PARAMS (( |
| bfd *abfd, |
| PTR in, |
| PTR ext)); |
| |
| unsigned int (*_bfd_coff_swap_reloc_out) PARAMS (( |
| bfd *abfd, |
| PTR src, |
| PTR dst)); |
| |
| unsigned int (*_bfd_coff_swap_filehdr_out) PARAMS (( |
| bfd *abfd, |
| PTR in, |
| PTR out)); |
| |
| unsigned int (*_bfd_coff_swap_aouthdr_out) PARAMS (( |
| bfd *abfd, |
| PTR in, |
| PTR out)); |
| |
| unsigned int (*_bfd_coff_swap_scnhdr_out) PARAMS (( |
| bfd *abfd, |
| PTR in, |
| PTR out)); |
| Special entry points for generic COFF routines to call target |
| dependent COFF routines: |
| unsigned int _bfd_filhsz; |
| unsigned int _bfd_aoutsz; |
| unsigned int _bfd_scnhsz; |
| unsigned int _bfd_symesz; |
| unsigned int _bfd_auxesz; |
| unsigned int _bfd_relsz; |
| unsigned int _bfd_linesz; |
| unsigned int _bfd_filnmlen; |
| boolean _bfd_coff_long_filenames; |
| boolean _bfd_coff_long_section_names; |
| unsigned int _bfd_coff_default_section_alignment_power; |
| void (*_bfd_coff_swap_filehdr_in) PARAMS (( |
| bfd *abfd, |
| PTR ext, |
| PTR in)); |
| void (*_bfd_coff_swap_aouthdr_in) PARAMS (( |
| bfd *abfd, |
| PTR ext, |
| PTR in)); |
| void (*_bfd_coff_swap_scnhdr_in) PARAMS (( |
| bfd *abfd, |
| PTR ext, |
| PTR in)); |
| void (*_bfd_coff_swap_reloc_in) PARAMS (( |
| bfd *abfd, |
| PTR ext, |
| PTR in)); |
| boolean (*_bfd_coff_bad_format_hook) PARAMS (( |
| bfd *abfd, |
| PTR internal_filehdr)); |
| boolean (*_bfd_coff_set_arch_mach_hook) PARAMS (( |
| bfd *abfd, |
| PTR internal_filehdr)); |
| PTR (*_bfd_coff_mkobject_hook) PARAMS (( |
| bfd *abfd, |
| PTR internal_filehdr, |
| PTR internal_aouthdr)); |
| flagword (*_bfd_styp_to_sec_flags_hook) PARAMS (( |
| bfd *abfd, |
| PTR internal_scnhdr, |
| const char *name, |
| asection *section)); |
| void (*_bfd_set_alignment_hook) PARAMS (( |
| bfd *abfd, |
| asection *sec, |
| PTR internal_scnhdr)); |
| boolean (*_bfd_coff_slurp_symbol_table) PARAMS (( |
| bfd *abfd)); |
| boolean (*_bfd_coff_symname_in_debug) PARAMS (( |
| bfd *abfd, |
| struct internal_syment *sym)); |
| boolean (*_bfd_coff_pointerize_aux_hook) PARAMS (( |
| bfd *abfd, |
| combined_entry_type *table_base, |
| combined_entry_type *symbol, |
| unsigned int indaux, |
| combined_entry_type *aux)); |
| boolean (*_bfd_coff_print_aux) PARAMS (( |
| bfd *abfd, |
| FILE *file, |
| combined_entry_type *table_base, |
| combined_entry_type *symbol, |
| combined_entry_type *aux, |
| unsigned int indaux)); |
| void (*_bfd_coff_reloc16_extra_cases) PARAMS (( |
| bfd *abfd, |
| struct bfd_link_info *link_info, |
| struct bfd_link_order *link_order, |
| arelent *reloc, |
| bfd_byte *data, |
| unsigned int *src_ptr, |
| unsigned int *dst_ptr)); |
| int (*_bfd_coff_reloc16_estimate) PARAMS (( |
| bfd *abfd, |
| asection *input_section, |
| arelent *r, |
| unsigned int shrink, |
| struct bfd_link_info *link_info)); |
| enum coff_symbol_classification (*_bfd_coff_classify_symbol) PARAMS (( |
| bfd *abfd, |
| struct internal_syment *)); |
| boolean (*_bfd_coff_compute_section_file_positions) PARAMS (( |
| bfd *abfd)); |
| boolean (*_bfd_coff_start_final_link) PARAMS (( |
| bfd *output_bfd, |
| struct bfd_link_info *info)); |
| boolean (*_bfd_coff_relocate_section) PARAMS (( |
| bfd *output_bfd, |
| struct bfd_link_info *info, |
| bfd *input_bfd, |
| asection *input_section, |
| bfd_byte *contents, |
| struct internal_reloc *relocs, |
| struct internal_syment *syms, |
| asection **sections)); |
| reloc_howto_type *(*_bfd_coff_rtype_to_howto) PARAMS (( |
| bfd *abfd, |
| asection *sec, |
| struct internal_reloc *rel, |
| struct coff_link_hash_entry *h, |
| struct internal_syment *sym, |
| bfd_vma *addendp)); |
| boolean (*_bfd_coff_adjust_symndx) PARAMS (( |
| bfd *obfd, |
| struct bfd_link_info *info, |
| bfd *ibfd, |
| asection *sec, |
| struct internal_reloc *reloc, |
| boolean *adjustedp)); |
| boolean (*_bfd_coff_link_add_one_symbol) PARAMS (( |
| struct bfd_link_info *info, |
| bfd *abfd, |
| const char *name, |
| flagword flags, |
| asection *section, |
| bfd_vma value, |
| const char *string, |
| boolean copy, |
| boolean collect, |
| struct bfd_link_hash_entry **hashp)); |
| |
| boolean (*_bfd_coff_link_output_has_begun) PARAMS (( |
| bfd * abfd, |
| struct coff_final_link_info * pfinfo)); |
| boolean (*_bfd_coff_final_link_postscript) PARAMS (( |
| bfd * abfd, |
| struct coff_final_link_info * pfinfo)); |
| |
| } bfd_coff_backend_data; |
| |
| #define coff_backend_info(abfd) ((bfd_coff_backend_data *) (abfd)->xvec->backend_data) |
| |
| #define bfd_coff_swap_aux_in(a,e,t,c,ind,num,i) \ |
| ((coff_backend_info (a)->_bfd_coff_swap_aux_in) (a,e,t,c,ind,num,i)) |
| |
| #define bfd_coff_swap_sym_in(a,e,i) \ |
| ((coff_backend_info (a)->_bfd_coff_swap_sym_in) (a,e,i)) |
| |
| #define bfd_coff_swap_lineno_in(a,e,i) \ |
| ((coff_backend_info ( a)->_bfd_coff_swap_lineno_in) (a,e,i)) |
| |
| #define bfd_coff_swap_reloc_out(abfd, i, o) \ |
| ((coff_backend_info (abfd)->_bfd_coff_swap_reloc_out) (abfd, i, o)) |
| |
| #define bfd_coff_swap_lineno_out(abfd, i, o) \ |
| ((coff_backend_info (abfd)->_bfd_coff_swap_lineno_out) (abfd, i, o)) |
| |
| #define bfd_coff_swap_aux_out(a,i,t,c,ind,num,o) \ |
| ((coff_backend_info (a)->_bfd_coff_swap_aux_out) (a,i,t,c,ind,num,o)) |
| |
| #define bfd_coff_swap_sym_out(abfd, i,o) \ |
| ((coff_backend_info (abfd)->_bfd_coff_swap_sym_out) (abfd, i, o)) |
| |
| #define bfd_coff_swap_scnhdr_out(abfd, i,o) \ |
| ((coff_backend_info (abfd)->_bfd_coff_swap_scnhdr_out) (abfd, i, o)) |
| |
| #define bfd_coff_swap_filehdr_out(abfd, i,o) \ |
| ((coff_backend_info (abfd)->_bfd_coff_swap_filehdr_out) (abfd, i, o)) |
| |
| #define bfd_coff_swap_aouthdr_out(abfd, i,o) \ |
| ((coff_backend_info (abfd)->_bfd_coff_swap_aouthdr_out) (abfd, i, o)) |
| |
| #define bfd_coff_filhsz(abfd) (coff_backend_info (abfd)->_bfd_filhsz) |
| #define bfd_coff_aoutsz(abfd) (coff_backend_info (abfd)->_bfd_aoutsz) |
| #define bfd_coff_scnhsz(abfd) (coff_backend_info (abfd)->_bfd_scnhsz) |
| #define bfd_coff_symesz(abfd) (coff_backend_info (abfd)->_bfd_symesz) |
| #define bfd_coff_auxesz(abfd) (coff_backend_info (abfd)->_bfd_auxesz) |
| #define bfd_coff_relsz(abfd) (coff_backend_info (abfd)->_bfd_relsz) |
| #define bfd_coff_linesz(abfd) (coff_backend_info (abfd)->_bfd_linesz) |
| #define bfd_coff_filnmlen(abfd) (coff_backend_info (abfd)->_bfd_filnmlen) |
| #define bfd_coff_long_filenames(abfd) (coff_backend_info (abfd)->_bfd_coff_long_filenames) |
| #define bfd_coff_long_section_names(abfd) \ |
| (coff_backend_info (abfd)->_bfd_coff_long_section_names) |
| #define bfd_coff_default_section_alignment_power(abfd) \ |
| (coff_backend_info (abfd)->_bfd_coff_default_section_alignment_power) |
| #define bfd_coff_swap_filehdr_in(abfd, i,o) \ |
| ((coff_backend_info (abfd)->_bfd_coff_swap_filehdr_in) (abfd, i, o)) |
| |
| #define bfd_coff_swap_aouthdr_in(abfd, i,o) \ |
| ((coff_backend_info (abfd)->_bfd_coff_swap_aouthdr_in) (abfd, i, o)) |
| |
| #define bfd_coff_swap_scnhdr_in(abfd, i,o) \ |
| ((coff_backend_info (abfd)->_bfd_coff_swap_scnhdr_in) (abfd, i, o)) |
| |
| #define bfd_coff_swap_reloc_in(abfd, i, o) \ |
| ((coff_backend_info (abfd)->_bfd_coff_swap_reloc_in) (abfd, i, o)) |
| |
| #define bfd_coff_bad_format_hook(abfd, filehdr) \ |
| ((coff_backend_info (abfd)->_bfd_coff_bad_format_hook) (abfd, filehdr)) |
| |
| #define bfd_coff_set_arch_mach_hook(abfd, filehdr)\ |
| ((coff_backend_info (abfd)->_bfd_coff_set_arch_mach_hook) (abfd, filehdr)) |
| #define bfd_coff_mkobject_hook(abfd, filehdr, aouthdr)\ |
| ((coff_backend_info (abfd)->_bfd_coff_mkobject_hook) (abfd, filehdr, aouthdr)) |
| |
| #define bfd_coff_styp_to_sec_flags_hook(abfd, scnhdr, name, section)\ |
| ((coff_backend_info (abfd)->_bfd_styp_to_sec_flags_hook)\ |
| (abfd, scnhdr, name, section)) |
| |
| #define bfd_coff_set_alignment_hook(abfd, sec, scnhdr)\ |
| ((coff_backend_info (abfd)->_bfd_set_alignment_hook) (abfd, sec, scnhdr)) |
| |
| #define bfd_coff_slurp_symbol_table(abfd)\ |
| ((coff_backend_info (abfd)->_bfd_coff_slurp_symbol_table) (abfd)) |
| |
| #define bfd_coff_symname_in_debug(abfd, sym)\ |
| ((coff_backend_info (abfd)->_bfd_coff_symname_in_debug) (abfd, sym)) |
| |
| #define bfd_coff_print_aux(abfd, file, base, symbol, aux, indaux)\ |
| ((coff_backend_info (abfd)->_bfd_coff_print_aux)\ |
| (abfd, file, base, symbol, aux, indaux)) |
| |
| #define bfd_coff_reloc16_extra_cases(abfd, link_info, link_order, reloc, data, src_ptr, dst_ptr)\ |
| ((coff_backend_info (abfd)->_bfd_coff_reloc16_extra_cases)\ |
| (abfd, link_info, link_order, reloc, data, src_ptr, dst_ptr)) |
| |
| #define bfd_coff_reloc16_estimate(abfd, section, reloc, shrink, link_info)\ |
| ((coff_backend_info (abfd)->_bfd_coff_reloc16_estimate)\ |
| (abfd, section, reloc, shrink, link_info)) |
| |
| #define bfd_coff_classify_symbol(abfd, sym)\ |
| ((coff_backend_info (abfd)->_bfd_coff_classify_symbol)\ |
| (abfd, sym)) |
| |
| #define bfd_coff_compute_section_file_positions(abfd)\ |
| ((coff_backend_info (abfd)->_bfd_coff_compute_section_file_positions)\ |
| (abfd)) |
| |
| #define bfd_coff_start_final_link(obfd, info)\ |
| ((coff_backend_info (obfd)->_bfd_coff_start_final_link)\ |
| (obfd, info)) |
| #define bfd_coff_relocate_section(obfd,info,ibfd,o,con,rel,isyms,secs)\ |
| ((coff_backend_info (ibfd)->_bfd_coff_relocate_section)\ |
| (obfd, info, ibfd, o, con, rel, isyms, secs)) |
| #define bfd_coff_rtype_to_howto(abfd, sec, rel, h, sym, addendp)\ |
| ((coff_backend_info (abfd)->_bfd_coff_rtype_to_howto)\ |
| (abfd, sec, rel, h, sym, addendp)) |
| #define bfd_coff_adjust_symndx(obfd, info, ibfd, sec, rel, adjustedp)\ |
| ((coff_backend_info (abfd)->_bfd_coff_adjust_symndx)\ |
| (obfd, info, ibfd, sec, rel, adjustedp)) |
| #define bfd_coff_link_add_one_symbol(info,abfd,name,flags,section,value,string,cp,coll,hashp)\ |
| ((coff_backend_info (abfd)->_bfd_coff_link_add_one_symbol)\ |
| (info, abfd, name, flags, section, value, string, cp, coll, hashp)) |
| |
| #define bfd_coff_link_output_has_begun(a,p) \ |
| ((coff_backend_info (a)->_bfd_coff_link_output_has_begun) (a,p)) |
| #define bfd_coff_final_link_postscript(a,p) \ |
| ((coff_backend_info (a)->_bfd_coff_final_link_postscript) (a,p)) |
| |
| Writing relocations |
| ................... |
| |
| To write relocations, the back end steps though the canonical |
| relocation table and create an `internal_reloc'. The symbol index to |
| use is removed from the `offset' field in the symbol table supplied. |
| The address comes directly from the sum of the section base address and |
| the relocation offset; the type is dug directly from the howto field. |
| Then the `internal_reloc' is swapped into the shape of an |
| `external_reloc' and written out to disk. |
| |
| Reading linenumbers |
| ................... |
| |
| Creating the linenumber table is done by reading in the entire coff |
| linenumber table, and creating another table for internal use. |
| |
| A coff linenumber table is structured so that each function is |
| marked as having a line number of 0. Each line within the function is |
| an offset from the first line in the function. The base of the line |
| number information for the table is stored in the symbol associated |
| with the function. |
| |
| Note: The PE format uses line number 0 for a flag indicating a new |
| source file. |
| |
| The information is copied from the external to the internal table, |
| and each symbol which marks a function is marked by pointing its... |
| |
| How does this work ? |
| |
| Reading relocations |
| ................... |
| |
| Coff relocations are easily transformed into the internal BFD form |
| (`arelent'). |
| |
| Reading a coff relocation table is done in the following stages: |
| |
| * Read the entire coff relocation table into memory. |
| |
| * Process each relocation in turn; first swap it from the external |
| to the internal form. |
| |
| * Turn the symbol referenced in the relocation's symbol index into a |
| pointer into the canonical symbol table. This table is the same |
| as the one returned by a call to `bfd_canonicalize_symtab'. The |
| back end will call that routine and save the result if a |
| canonicalization hasn't been done. |
| |
| * The reloc index is turned into a pointer to a howto structure, in |
| a back end specific way. For instance, the 386 and 960 use the |
| `r_type' to directly produce an index into a howto table vector; |
| the 88k subtracts a number from the `r_type' field and creates an |
| addend field. |
| |
| |
| File: bfd.info, Node: elf, Prev: coff, Up: BFD back ends |
| |
| ELF backends |
| ============ |
| |
| BFD support for ELF formats is being worked on. Currently, the best |
| supported back ends are for sparc and i386 (running svr4 or Solaris 2). |
| |
| Documentation of the internals of the support code still needs to be |
| written. The code is changing quickly enough that we haven't bothered |
| yet. |
| |
| `bfd_elf_find_section' |
| ...................... |
| |
| *Synopsis* |
| struct elf_internal_shdr *bfd_elf_find_section (bfd *abfd, char *name); |
| *Description* |
| Helper functions for GDB to locate the string tables. Since BFD hides |
| string tables from callers, GDB needs to use an internal hook to find |
| them. Sun's .stabstr, in particular, isn't even pointed to by the |
| .stab section, so ordinary mechanisms wouldn't work to find it, even if |
| we had some. |
| |