| @section 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 |
| @file{coff-m88k.c}. This file @code{#include}s |
| @file{coff/m88k.h} which defines the external structure of the |
| coff format for the 88k, and @file{coff/internal.h} which |
| defines the internal structure. @file{coff-m88k.c} also |
| defines the relocations used by the 88k format |
| @xref{Relocations}. |
| |
| The Intel i960 processor version of coff is implemented in |
| @file{coff-i960.c}. This file has the same structure as |
| @file{coff-m88k.c}, except that it includes @file{coff/i960.h} |
| rather than @file{coff-m88k.h}. |
| |
| @subsection 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 @file{i386coff.c} to @file{foocoff.c}, copy |
| @file{../include/coff/i386.h} to @file{../include/coff/foo.h}, |
| and add the lines to @file{targets.c} and @file{Makefile.in} |
| so that your new back end is used. Alter the shapes of the |
| structures in @file{../include/coff/foo.h} so that they match |
| what you need. You will probably also have to add |
| @code{#ifdef}s to the code in @file{coff/internal.h} and |
| @file{coffcode.h} if your version of coff is too wild. |
| |
| You can verify that your new BFD backend works quite simply by |
| building @file{objdump} from the @file{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 @code{att-dump} or just |
| @code{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. |
| |
| @subsection How the coff backend works |
| |
| |
| @subsubsection 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 @file{coffgen.c}. These routines |
| work for any Coff target. They use some hooks into the target |
| specific code; the hooks are in a @code{bfd_coff_backend_data} |
| structure, one of which exists for each target. |
| |
| The essentially similar target-specific routines are in |
| @file{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 @file{coffcode.h}. |
| |
| Some of the Coff targets then also have additional routines in |
| the target source file itself. |
| |
| For example, @file{coff-i960.c} includes |
| @file{coff/internal.h} and @file{coff/i960.h}. It then |
| defines a few constants, such as @code{I960}, and includes |
| @file{coffcode.h}. Since the i960 has complex relocation |
| types, @file{coff-i960.c} also includes some code to |
| manipulate the i960 relocs. This code is not in |
| @file{coffcode.h} because it would not be used by any other |
| target. |
| |
| @subsubsection 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 |
| @file{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 |
| @code{bfd_swap}_@i{thing}_@i{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 |
| @file{coffcode.h}. E.g., the size of line number entry in coff is |
| sometimes 16 bits, and sometimes 32 bits. @code{#define}ing |
| @code{PUT_LNSZ_LNNO} and @code{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 @code{#defines}. |
| Three of the bit twiddling routines are exported to |
| @code{gdb}; @code{coff_swap_aux_in}, @code{coff_swap_sym_in} |
| and @code{coff_swap_lineno_in}. @code{GDB} reads the symbol |
| table on its own, but uses BFD to fix things up. More of the |
| bit twiddlers are exported for @code{gas}; |
| @code{coff_swap_aux_out}, @code{coff_swap_sym_out}, |
| @code{coff_swap_lineno_out}, @code{coff_swap_reloc_out}, |
| @code{coff_swap_filehdr_out}, @code{coff_swap_aouthdr_out}, |
| @code{coff_swap_scnhdr_out}. @code{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 @code{gas}, which makes one avenue to disaster disappear. |
| |
| @subsubsection 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 |
| @code{bfd_canonicalize_symtab}), a request gets through to |
| @code{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 |
| (@code{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 |
| (@code{".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 |
| @code{sclass} field) about the various flags to set in the |
| @code{asymbol}. @xref{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. |
| |
| @subsubsection Symbol writing |
| Writing a symbol to a coff file which didn't come from a coff |
| file will lose any debugging information. The @code{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 |
| (@code{C_FILE}) to point to the next file place holder in the |
| list. It also marks each @code{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 |
| @code{output_section} field of the @code{asymbol}'s |
| @code{asection} @xref{Sections}. |
| |
| @itemize @bullet |
| |
| @item |
| @code{coff_mangle_symbols} |
| @end itemize |
| 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. |
| |
| @itemize @bullet |
| |
| @item |
| @code{coff_write_symbols} |
| @end itemize |
| 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. |
| |
| @findex coff_symbol_type |
| @subsubsection @code{coff_symbol_type} |
| @strong{Description}@* |
| The hidden information for an @code{asymbol} is described in a |
| @code{combined_entry_type}: |
| |
| |
| @example |
| |
| 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; |
| @end example |
| @findex bfd_coff_backend_data |
| @subsubsection @code{bfd_coff_backend_data} |
| |
| @example |
| /* 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 |
| @}; |
| |
| @end example |
| Special entry points for gdb to swap in coff symbol table parts: |
| @example |
| 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)); |
| |
| @end example |
| Special entry points for gas to swap out coff parts: |
| @example |
| 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)); |
| |
| @end example |
| Special entry points for generic COFF routines to call target |
| dependent COFF routines: |
| @example |
| 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)) |
| |
| @end example |
| @subsubsection Writing relocations |
| To write relocations, the back end steps though the |
| canonical relocation table and create an |
| @code{internal_reloc}. The symbol index to use is removed from |
| the @code{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 @code{internal_reloc} is |
| swapped into the shape of an @code{external_reloc} and written |
| out to disk. |
| |
| @subsubsection 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 ? |
| |
| @subsubsection Reading relocations |
| Coff relocations are easily transformed into the internal BFD form |
| (@code{arelent}). |
| |
| Reading a coff relocation table is done in the following stages: |
| |
| @itemize @bullet |
| |
| @item |
| Read the entire coff relocation table into memory. |
| |
| @item |
| Process each relocation in turn; first swap it from the |
| external to the internal form. |
| |
| @item |
| 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 |
| @code{bfd_canonicalize_symtab}. The back end will call that |
| routine and save the result if a canonicalization hasn't been done. |
| |
| @item |
| 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 @code{r_type} to directly produce an index |
| into a howto table vector; the 88k subtracts a number from the |
| @code{r_type} field and creates an addend field. |
| @end itemize |
| |