coffcode.h

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/* Support for the generic parts of most COFF variants, for BFD.
   Copyright 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
   2000, 2001
   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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

/*
Most of this hacked by  Steve Chamberlain,
			[e-mail]
*/
/*

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
	(<<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
	<<output_section>> field of the @code{asymbol}'s
	@code{asection} @xref{Sections}.

	o <<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.

	o <<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.

*/

/*
INTERNAL_DEFINITION
	coff_symbol_type

DESCRIPTION
	The hidden information for an <<asymbol>> is described in a
	<<combined_entry_type>>:

CODE_FRAGMENT
.
.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;

*/

#ifdef COFF_WITH_PE
#include "peicode.h"
#else
#include "coffswap.h"
#endif

#define STRING_SIZE_SIZE (4)

static long sec_to_styp_flags PARAMS ((const char *, flagword));
static flagword styp_to_sec_flags
  PARAMS ((bfd *, PTR, const char *, asection *));
static boolean coff_bad_format_hook PARAMS ((bfd *, PTR));
static void coff_set_custom_section_alignment
  PARAMS ((bfd *, asection *, const struct coff_section_alignment_entry *,
	   const unsigned int));
static boolean coff_new_section_hook PARAMS ((bfd *, asection *));
static boolean coff_set_arch_mach_hook PARAMS ((bfd *, PTR));
static boolean coff_write_relocs PARAMS ((bfd *, int));
static boolean coff_set_flags
  PARAMS ((bfd *, unsigned int *, unsigned short *));
static boolean coff_set_arch_mach
  PARAMS ((bfd *, enum bfd_architecture, unsigned long));
static boolean coff_compute_section_file_positions PARAMS ((bfd *));
static boolean coff_write_object_contents PARAMS ((bfd *));
static boolean coff_set_section_contents
  PARAMS ((bfd *, asection *, PTR, file_ptr, bfd_size_type));
static PTR buy_and_read PARAMS ((bfd *, file_ptr, int, size_t));
static boolean coff_slurp_line_table PARAMS ((bfd *, asection *));
static boolean coff_slurp_symbol_table PARAMS ((bfd *));
static enum coff_symbol_classification coff_classify_symbol
  PARAMS ((bfd *, struct internal_syment *));
static boolean coff_slurp_reloc_table PARAMS ((bfd *, asection *, asymbol **));
static long coff_canonicalize_reloc
  PARAMS ((bfd *, asection *, arelent **, asymbol **));
#ifndef coff_mkobject_hook
static PTR coff_mkobject_hook PARAMS ((bfd *, PTR,  PTR));
#endif
#ifdef COFF_WITH_PE
static flagword handle_COMDAT PARAMS ((bfd *, flagword, PTR, const char *, asection *));
#endif

/* void warning(); */

/* Return a word with STYP_* (scnhdr.s_flags) flags set to represent
   the incoming SEC_* flags.  The inverse of this function is
   styp_to_sec_flags().  NOTE: If you add to/change this routine, you
   should probably mirror the changes in styp_to_sec_flags().  */

#ifndef COFF_WITH_PE

/* Macros for setting debugging flags.  */
#ifdef STYP_DEBUG
#define STYP_XCOFF_DEBUG STYP_DEBUG
#else
#define STYP_XCOFF_DEBUG STYP_INFO
#endif

#ifdef COFF_ALIGN_IN_S_FLAGS
#define STYP_DEBUG_INFO STYP_DSECT
#else
#define STYP_DEBUG_INFO STYP_INFO
#endif

static long
sec_to_styp_flags (sec_name, sec_flags)
     CONST char *sec_name;
     flagword sec_flags;
{
  long styp_flags = 0;

  if (!strcmp (sec_name, _TEXT))
    {
      styp_flags = STYP_TEXT;
    }
  else if (!strcmp (sec_name, _DATA))
    {
      styp_flags = STYP_DATA;
    }
  else if (!strcmp (sec_name, _BSS))
    {
      styp_flags = STYP_BSS;
#ifdef _COMMENT
    }
  else if (!strcmp (sec_name, _COMMENT))
    {
      styp_flags = STYP_INFO;
#endif /* _COMMENT */
#ifdef _LIB
    }
  else if (!strcmp (sec_name, _LIB))
    {
      styp_flags = STYP_LIB;
#endif /* _LIB */
#ifdef _LIT
    }
  else if (!strcmp (sec_name, _LIT))
    {
      styp_flags = STYP_LIT;
#endif /* _LIT */
    }
  else if (!strncmp (sec_name, ".debug", 6))
    {
      /* Handle the XCOFF debug section and DWARF2 debug sections.  */
      if (!sec_name[6])
        styp_flags = STYP_XCOFF_DEBUG;
      else
        styp_flags = STYP_DEBUG_INFO;
    }
  else if (!strncmp (sec_name, ".stab", 5))
    {
      styp_flags = STYP_DEBUG_INFO;
    }
#ifdef COFF_LONG_SECTION_NAMES
  else if (!strncmp (sec_name, ".gnu.linkonce.wi.", 17))
    {