targets.c

早期freebsd实现

/* Generic target-file-type support for the BFD library.
   Copyright 1990, 1991, 1992 Free Software Foundation, Inc.
   Written by Cygnus Support.

This file is part of BFD, the Binary File Descriptor library.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */

#include "bfd.h"
#include "sysdep.h"
#include "libbfd.h"

/*
SECTION 
	Targets

DESCRIPTION
	Each port of BFD to a different machine requries the creation
	of a target back end. All the back end provides to the root
	part of BFD is a structure containing pointers to functions
	which perform certain low level operations on files. BFD
	translates the applications's requests through a pointer into
	calls to the back end routines. 

	When a file is opened with <<bfd_openr>>, its format and
	target are unknown. BFD uses various mechanisms to determine
	how to interpret the file. The operations performed are:

	o First a BFD is created by calling the internal routine
	<<new_bfd>>, then <<bfd_find_target>> is called with the
	target string supplied to <<bfd_openr>> and the new BFD pointer. 

	o If a null target string was provided to <<bfd_find_target>>,
	it looks up the environment variable <<GNUTARGET>> and uses
	that as the target string. 

	o If the target string is still NULL, or the target string is
	<<default>>, then the first item in the target vector is used
	as the target type, and <<target_defaulted>> is set to
	cause <<bfd_check_format>> to loop through all the targets.
	@xref{bfd_target}.  @xref{Formats}.

	o Otherwise, the elements in the target vector are inspected
	one by one, until a match on target name is found. When found,
	that is used. 

	o Otherwise the error <<invalid_target>> is returned to
	<<bfd_openr>>.

	o <<bfd_openr>> attempts to open the file using
	<<bfd_open_file>>, and returns the BFD.

	Once the BFD has been opened and the target selected, the file
	format may be determined. This is done by calling
	<<bfd_check_format>> on the BFD with a suggested format. 
	If <<target_defaulted>> has been set, each possible target
	type is tried to see if it recognizes the specified format.  The
	routine returns <<true>> when the application guesses right.
@menu
@* bfd_target::
@end menu
*/


/*

INODE
	bfd_target,  , Targets, Targets
DOCDD
SUBSECTION
	bfd_target

DESCRIPTION
	This structure contains everything that BFD knows about a
	target. It includes things like its byte order, name, what
	routines to call to do various operations, etc.   

	Every BFD points to a target structure with its <<xvec>>
	member. 

	Shortcut for declaring fields which are prototyped function
	pointers, while avoiding anguish on compilers that don't
	support protos.

.#define SDEF(ret, name, arglist) \
.                PROTO(ret,(*name),arglist)
.#define SDEF_FMT(ret, name, arglist) \
.                PROTO(ret,(*name[bfd_type_end]),arglist)

	These macros are used to dispatch to functions through the
	bfd_target vector. They are used in a number of macros further
	down in @file{bfd.h}, and are also used when calling various
	routines by hand inside the BFD implementation.  The "arglist"
	argument must be parenthesized; it contains all the arguments
	to the called function. 

	They make the documentation (more) unpleasant to read, so if
	someone wants to fix this and not break the above, please do.

.#define BFD_SEND(bfd, message, arglist) \
.               ((*((bfd)->xvec->message)) arglist)

	For operations which index on the BFD format 

.#define BFD_SEND_FMT(bfd, message, arglist) \
.            (((bfd)->xvec->message[(int)((bfd)->format)]) arglist)

	This is the struct which defines the type of BFD this is.  The
	<<xvec>> member of the struct <<bfd>> itself points here.  Each
	module that implements access to a different target under BFD,
	defines one of these.


	FIXME, these names should be rationalised with the names of
	the entry points which call them. Too bad we can't have one
	macro to define them both! 

.typedef struct bfd_target
.{

Identifies the kind of target, eg SunOS4, Ultrix, etc.

.  char *name;

The "flavour" of a back end is a general indication about the contents
of a file.

.  enum target_flavour {
.    bfd_target_unknown_flavour,
.    bfd_target_aout_flavour,
.    bfd_target_coff_flavour,
.    bfd_target_elf_flavour,
.    bfd_target_ieee_flavour,
.    bfd_target_oasys_flavour,
.    bfd_target_tekhex_flavour,
.    bfd_target_srec_flavour,
.    bfd_target_hppa_flavour} flavour;

The order of bytes within the data area of a file.

.  boolean byteorder_big_p;

The order of bytes within the header parts of a file.

.  boolean header_byteorder_big_p;

This is a mask of all the flags which an executable may have set -
from the set <<NO_FLAGS>>, <<HAS_RELOC>>, ...<<D_PAGED>>.

.  flagword object_flags;       

This is a mask of all the flags which a section may have set - from
the set <<SEC_NO_FLAGS>>, <<SEC_ALLOC>>, ...<<SET_NEVER_LOAD>>.

.  flagword section_flags;

The character normally found at the front of a symbol 
(if any), perhaps _.

.  char symbol_leading_char;

The pad character for filenames within an archive header.

.  char ar_pad_char;            

The maximum number of characters in an archive header.

. unsigned short ar_max_namelen;

The minimum alignment restriction for any section.

.  unsigned int align_power_min;

Entries for byte swapping for data. These are different to the other
entry points, since they don't take BFD as first arg.  Certain other handlers
could do the same.

.  SDEF (bfd_vma,      bfd_getx64, (bfd_byte *));
.  SDEF (void,         bfd_putx64, (bfd_vma, bfd_byte *));
.  SDEF (bfd_vma, bfd_getx32, (bfd_byte *));
.  SDEF (void,         bfd_putx32, (bfd_vma, bfd_byte *));
.  SDEF (bfd_vma, bfd_getx16, (bfd_byte *));
.  SDEF (void,         bfd_putx16, (bfd_vma, bfd_byte *));

Byte swapping for the headers

.  SDEF (bfd_vma,   bfd_h_getx64, (bfd_byte *));
.  SDEF (void,          bfd_h_putx64, (bfd_vma, bfd_byte *));
.  SDEF (bfd_vma,  bfd_h_getx32, (bfd_byte *));
.  SDEF (void,          bfd_h_putx32, (bfd_vma, bfd_byte *));
.  SDEF (bfd_vma,  bfd_h_getx16, (bfd_byte *));
.  SDEF (void,          bfd_h_putx16, (bfd_vma, bfd_byte *));

Format dependent routines, these turn into vectors of entry points
within the target vector structure; one for each format to check.

Check the format of a file being read.  Return bfd_target * or zero. 

.  SDEF_FMT (struct bfd_target *, _bfd_check_format, (bfd *));

Set the format of a file being written.  

.  SDEF_FMT (boolean,            _bfd_set_format, (bfd *));

Write cached information into a file being written, at bfd_close. 

.  SDEF_FMT (boolean,            _bfd_write_contents, (bfd *));

The following functions are defined in <<JUMP_TABLE>>. The idea is
that the back end writer of <<foo>> names all the routines
<<foo_>>@var{entry_point}, <<JUMP_TABLE>> will built the entries
in this structure in the right order.

Core file entry points

.  SDEF (char *, _core_file_failing_command, (bfd *));
.  SDEF (int,    _core_file_failing_signal, (bfd *));
.  SDEF (boolean, _core_file_matches_executable_p, (bfd *, bfd *));

Archive entry points

. SDEF (boolean, _bfd_slurp_armap, (bfd *));
. SDEF (boolean, _bfd_slurp_extended_name_table, (bfd *));
. SDEF (void,   _bfd_truncate_arname, (bfd *, CONST char *, char *));
. SDEF (boolean, write_armap, (bfd *arch, 
.                              unsigned int elength,
.                              struct orl *map,
.                              unsigned int orl_count, 
.                              int stridx));

Standard stuff.

.  SDEF (boolean, _close_and_cleanup, (bfd *));
.  SDEF (boolean, _bfd_set_section_contents, (bfd *, sec_ptr, PTR,
.                                            file_ptr, bfd_size_type));
.  SDEF (boolean, _bfd_get_section_contents, (bfd *, sec_ptr, PTR, 
.                                            file_ptr, bfd_size_type));
.  SDEF (boolean, _new_section_hook, (bfd *, sec_ptr));

Symbols and relocations

.  SDEF (unsigned int, _get_symtab_upper_bound, (bfd *));
.  SDEF (unsigned int, _bfd_canonicalize_symtab,
.           (bfd *, struct symbol_cache_entry **));
.  SDEF (unsigned int, _get_reloc_upper_bound, (bfd *, sec_ptr));
.  SDEF (unsigned int, _bfd_canonicalize_reloc, (bfd *, sec_ptr, arelent **,
.                                               struct symbol_cache_entry**));
.  SDEF (struct symbol_cache_entry  *, _bfd_make_empty_symbol, (bfd *));
.  SDEF (void,     _bfd_print_symbol, (bfd *, PTR, struct symbol_cache_entry  *,
.                                      bfd_print_symbol_type));
.#define bfd_print_symbol(b,p,s,e) BFD_SEND(b, _bfd_print_symbol, (b,p,s,e))
.  SDEF (alent *,   _get_lineno, (bfd *, struct symbol_cache_entry  *));
.
.  SDEF (boolean,   _bfd_set_arch_mach, (bfd *, enum bfd_architecture,
.                                       unsigned long));
.
.  SDEF (bfd *,  openr_next_archived_file, (bfd *arch, bfd *prev));
.  SDEF (boolean, _bfd_find_nearest_line,
.        (bfd *abfd, struct sec  *section,
.         struct symbol_cache_entry  **symbols,bfd_vma offset,
.        CONST char **file, CONST char **func, unsigned int *line));
.  SDEF (int,    _bfd_stat_arch_elt, (bfd *, struct stat *));
.
.  SDEF (int,    _bfd_sizeof_headers, (bfd *, boolean));
.
.  SDEF (void, _bfd_debug_info_start, (bfd *));
.  SDEF (void, _bfd_debug_info_end, (bfd *));
.  SDEF (void, _bfd_debug_info_accumulate, (bfd *, struct sec  *));
.  SDEF (bfd_byte *, _bfd_get_relocated_section_contents, (bfd*,struct bfd_seclet_struct *, bfd_byte *data));
.  SDEF (boolean,_bfd_relax_section,(bfd *, struct sec *, struct symbol_cache_entry **));
Special entry points for gdb to swap in coff symbol table parts

.  SDEF(void, _bfd_coff_swap_aux_in,(
.       bfd            *abfd ,
.       PTR             ext,
.       int             type,
.       int             class ,
.       PTR             in));