write.c

早期freebsd实现

/* write.c - emit .o file - Copyright(C)1986 Free Software Foundation, Inc.
   Copyright (C) 1986,1987 Free Software Foundation, Inc.

This file is part of GAS, the GNU Assembler.

GAS 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 1, or (at your option)
any later version.

GAS 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 GAS; see the file COPYING.  If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */

/* 

   Umm, with real good luck, this thing should be set up to do byteordering
   correctly, but I may have managed to miss a place or two.  Treat a.out
   very carefully until you're SURE that it works. . .

   In order to cross-assemble the target machine must have an a.out header
   similar to the one in a.out.h on THIS machine.  Byteorder doesn't matter;
   we take special care of it, but the numbers must be the same SIZE (# of
   bytes) and in the same PLACE.  If this is not true, you will have some
   trouble.
 */

#include "as.h"
#include "md.h"
#include "subsegs.h"
#include "obstack.h"
#include "struc-symbol.h"
#include "write.h"
#include "symbols.h"

#ifdef SPARC
#include "sparc.h"
#endif
#ifdef I860
#include "i860.h"
#endif

void	append();

#ifdef hpux
#define EXEC_MACHINE_TYPE HP9000S200_ID
#endif

#ifdef DOT_LABEL_PREFIX
#define LOCAL_LABEL(name) (name[0] =='.' \
                         && ( name [1] == 'L' || name [1] == '.' ))
#else  /* not defined DOT_LABEL_PREFIX */
#define LOCAL_LABEL(name) (name [0] == 'L' )
#endif /* not defined DOT_LABEL_PREFIX */

/*
 * In: length of relocation (or of address) in chars: 1, 2 or 4.
 * Out: GNU LD relocation length code: 0, 1, or 2.
 */

static unsigned char

nbytes_r_length [] = {
  42, 0, 1, 42, 2
  };


static struct frag *	text_frag_root;
static struct frag *	data_frag_root;

static struct frag *	text_last_frag;	/* Last frag in segment. */
static struct frag *	data_last_frag;	/* Last frag in segment. */

static struct exec	the_exec;

static long int string_byte_count;

static char *		the_object_file;

#if !defined(SPARC) && !defined(I860)
static
#endif
char *		next_object_file_charP;	/* Tracks object file bytes. */

static long int		size_of_the_object_file; /* # bytes in object file. */

/* static long int		length; JF unused */	/* String length, including trailing '\0'. */

static void	relax_segment();
void		emit_segment();
static relax_addressT	relax_align();
static long int	fixup_segment();
#if !defined(SPARC) && !defined(I860)
static void		emit_relocations();
#endif
/*
 *			fix_new()
 *
 * Create a fixS in obstack 'notes'.
 */
void
#if defined(SPARC) || defined(I860)
fix_new (frag, where, size, add_symbol, sub_symbol, offset, pcrel, r_type)
#else
fix_new (frag, where, size, add_symbol, sub_symbol, offset, pcrel)
#endif
     fragS *	frag;		/* Which frag? */
     int	where;		/* Where in that frag? */
     short int	size;		/* 1, 2  or 4 usually. */
     symbolS *	add_symbol;	/* X_add_symbol. */
     symbolS *	sub_symbol;	/* X_subtract_symbol. */
     long int	offset;		/* X_add_number. */
     int	pcrel;		/* TRUE if PC-relative relocation. */
#if defined(SPARC) || defined(I860)
    int		r_type;
#endif
{
  register fixS *	fixP;

  fixP = (fixS *)obstack_alloc(&notes,sizeof(fixS));

  fixP -> fx_frag	= frag;
  fixP -> fx_where	= where;
  fixP -> fx_size	= size;
  fixP -> fx_addsy	= add_symbol;
  fixP -> fx_subsy	= sub_symbol;
  fixP -> fx_offset	= offset;
  fixP -> fx_pcrel	= pcrel;
  fixP -> fx_next	= * seg_fix_rootP;

  /* JF these 'cuz of the NS32K stuff */
  fixP -> fx_im_disp	= 0;
  fixP -> fx_pcrel_adjust = 0;
  fixP -> fx_bsr	= 0;
  fixP ->fx_bit_fixP	= 0;

#if defined(SPARC) || defined(I860)
  fixP->fx_r_type = r_type;
#endif

  * seg_fix_rootP = fixP;
}

void
write_object_file()
{
  register struct frchain *	frchainP; /* Track along all frchains. */
  register fragS *		fragP;	/* Track along all frags. */
  register struct frchain *	next_frchainP;
  register fragS * *		prev_fragPP;
  register char *		name;
  register symbolS *		symbolP;
  register symbolS **		symbolPP;
  /* register fixS *		fixP; JF unused */
  unsigned
  	text_siz,
	data_siz,
	syms_siz,
	tr_siz,
	dr_siz;
  void output_file_create();
  void output_file_append();
  void output_file_close();
#ifdef DONTDEF
  void gdb_emit();
  void gdb_end();
#endif
  extern long omagic;		/* JF magic # to write out.  Is different for
				   Suns and Vaxen and other boxes */

#ifdef	VMS
  /*
   *	Under VMS we try to be compatible with VAX-11 "C".  Thus, we
   *	call a routine to check for the definition of the procedure
   *	"_main", and if so -- fix it up so that it can be program
   *	entry point.
   */
  VMS_Check_For_Main();
#endif /* VMS */
  /*
   * After every sub-segment, we fake an ".align ...". This conforms to BSD4.2
   * brane-damage. We then fake ".fill 0" because that is the kind of frag
   * that requires least thought. ".align" frags like to have a following
   * frag since that makes calculating their intended length trivial.
   */
#define SUB_SEGMENT_ALIGN (2)
  for ( frchainP=frchain_root; frchainP; frchainP=frchainP->frch_next )
    {
#ifdef	VMS
      /*
       *	Under VAX/VMS, the linker (and PSECT specifications)
       *	take care of correctly aligning the segments.
       *	Doing the alignment here (on initialized data) can
       *	mess up the calculation of global data PSECT sizes.
       */
#undef	SUB_SEGMENT_ALIGN
#define	SUB_SEGMENT_ALIGN ((frchainP->frch_seg != SEG_DATA) ? 2 : 0)
#endif	/* VMS */
      subseg_new (frchainP -> frch_seg, frchainP -> frch_subseg);
      frag_align (SUB_SEGMENT_ALIGN, 0);
				/* frag_align will have left a new frag. */
				/* Use this last frag for an empty ".fill". */
      /*
       * For this segment ...
       * Create a last frag. Do not leave a "being filled in frag".
       */
      frag_wane (frag_now);
      frag_now -> fr_fix	= 0;
      know( frag_now -> fr_next == NULL );
      /* know( frags . obstack_c_base == frags . obstack_c_next_free ); */
      /* Above shows we haven't left a half-completed object on obstack. */
    }

  /*
   * From now on, we don't care about sub-segments.
   * Build one frag chain for each segment. Linked thru fr_next.
   * We know that there is at least 1 text frchain & at least 1 data frchain.
   */
  prev_fragPP = &text_frag_root;
  for ( frchainP=frchain_root; frchainP; frchainP=next_frchainP )
    {
      know( frchainP -> frch_root );
      * prev_fragPP = frchainP -> frch_root;
      prev_fragPP = & frchainP -> frch_last -> fr_next;
      if (   ((next_frchainP = frchainP->frch_next) == NULL)
	  || next_frchainP == data0_frchainP)
	{
	  prev_fragPP = & data_frag_root;
	  if ( next_frchainP )
	    {
	      text_last_frag = frchainP -> frch_last;
	    }
	  else
	    {
	      data_last_frag = frchainP -> frch_last;
	    }
	}
    }				/* for(each struct frchain) */

  /*
   * We have two segments. If user gave -R flag, then we must put the
   * data frags into the text segment. Do this before relaxing so
   * we know to take advantage of -R and make shorter addresses.
   */
  if ( flagseen [ 'R' ] )
    {
      fixS *tmp;

      text_last_frag -> fr_next = data_frag_root;
      text_last_frag = data_last_frag;
      data_last_frag = NULL;
      data_frag_root = NULL;
      if(text_fix_root) {
	for(tmp=text_fix_root;tmp->fx_next;tmp=tmp->fx_next)
	  ;
	tmp->fx_next=data_fix_root;
      } else
        text_fix_root=data_fix_root;
      data_fix_root=NULL;
    }

  relax_segment (text_frag_root, SEG_TEXT);
  relax_segment (data_frag_root, SEG_DATA);
  /*
   * Now the addresses of frags are correct within the segment.
   */

  know(   text_last_frag -> fr_type   == rs_fill && text_last_frag -> fr_offset == 0 );
  text_siz=text_last_frag->fr_address;
#ifdef SPARC
  text_siz= (text_siz+7)&(~7);
  text_last_frag->fr_address=text_siz;
#endif
  md_number_to_chars((char *)&the_exec.a_text,text_siz, sizeof(the_exec.a_text));
  /* the_exec . a_text = text_last_frag -> fr_address; */

  /*
   * Join the 2 segments into 1 huge segment.
   * To do this, re-compute every rn_address in the SEG_DATA frags.
   * Then join the data frags after the text frags.
   *
   * Determine a_data [length of data segment].
   */
  if (data_frag_root)
    {
      register relax_addressT	slide;

      know(   text_last_frag -> fr_type   == rs_fill && text_last_frag -> fr_offset == 0 );
      data_siz=data_last_frag->fr_address;
#ifdef SPARC
      data_siz += (8 - (data_siz % 8)) % 8;
      data_last_frag->fr_address = data_siz;
#endif
      md_number_to_chars((char *)&the_exec.a_data,data_siz,sizeof(the_exec.a_data));
      /* the_exec . a_data = data_last_frag -> fr_address; */
      slide = text_siz; /* Address in file of the data segment. */
      for (fragP = data_frag_root;
	   fragP;
	   fragP = fragP -> fr_next)
	{
	  fragP -> fr_address += slide;
	}
      know( text_last_frag );
      text_last_frag -> fr_next = data_frag_root;
    }
  else {
      md_number_to_chars((char *)&the_exec.a_data,0,sizeof(the_exec.a_data));
      data_siz = 0;
  }

  bss_address_frag . fr_address = text_siz + data_siz;
#ifdef SPARC
  local_bss_counter=(local_bss_counter+7)&(~7);
#endif
  md_number_to_chars((char *)&the_exec.a_bss,local_bss_counter,sizeof(the_exec.a_bss));

	      
  /*
   *
   * Crawl the symbol chain.
   *
   * For each symbol whose value depends on a frag, take the address of
   * that frag and subsume it into the value of the symbol.
   * After this, there is just one way to lookup a symbol value.
   * Values are left in their final state for object file emission.
   * We adjust the values of 'L' local symbols, even if we do
   * not intend to emit them to the object file, because their values
   * are needed for fix-ups.
   *
   * Unless we saw a -L flag, remove all symbols that begin with 'L'
   * from the symbol chain.
   *
   * Count the (length of the nlists of the) (remaining) symbols.
   * Assign a symbol number to each symbol.
   * Count the number of string-table chars we will emit.
   *
   */
  know( zero_address_frag . fr_address == 0 );
  string_byte_count = sizeof( string_byte_count );

  /* JF deal with forward references first. . . */
  for(symbolP=symbol_rootP;symbolP;symbolP=symbolP->sy_next) {
  	if(symbolP->sy_forward) {
		symbolP->sy_value+=symbolP->sy_forward->sy_value+symbolP->sy_forward->sy_frag->fr_address;
		symbolP->sy_forward=0;
	}
  }
  symbolPP = & symbol_rootP;	/* -> last symbol chain link. */
  {
    register long int		symbol_number;

    symbol_number = 0;
    while (symbolP  = * symbolPP)
      {
	name = symbolP -> sy_name;
	if(flagseen['R'] && (symbolP->sy_nlist.n_type&N_DATA)) {
	  symbolP->sy_nlist.n_type&= ~N_DATA;
	  symbolP->sy_nlist.n_type|= N_TEXT;
	}
	/* if(symbolP->sy_forward) {
	  symbolP->sy_value += symbolP->sy_forward->sy_value + symbolP->sy_forward->sy_frag->fr_address;
	} */
	
	symbolP -> sy_value += symbolP -> sy_frag -> fr_address;
		/* JF the 128 bit is a hack so stabs like
		   "LET_STMT:23. . ."  don't go away */
	/* CPH: 128 bit hack is moby loser.  N_SO for file "Lower.c"
	   fell through the cracks.  I think that N_STAB should be
	   used instead of 128. */
		/* JF the \001 bit is to make sure that local labels
		   ( 1: - 9: don't make it into the symtable either */
#ifndef	VMS	/* Under VMS we need to keep local symbols */
	if ( !name || (symbolP->sy_nlist.n_type&N_STAB)
	    || (name[2]!='\001' && (flagseen ['L'] || ! LOCAL_LABEL(name) )))
#endif	/* not VMS */
	  {
	    symbolP -> sy_number = symbol_number ++;
#ifndef	VMS
	    if (name)
	      {			/* Ordinary case. */
		symbolP -> sy_name_offset = string_byte_count;
		string_byte_count += strlen (symbolP  -> sy_name) + 1;
	      }
	    else			/* .Stabd case. */
#endif	/* not VMS */
		symbolP -> sy_name_offset = 0;
	    symbolPP = & (symbolP -> sy_next);
	  }
#ifndef	VMS
	else
	    * symbolPP = symbolP -> sy_next;
#endif	/* not VMS */
      }				/* for each symbol */

    syms_siz = sizeof( struct nlist) * symbol_number;
    md_number_to_chars((char *)&the_exec.a_syms,syms_siz,sizeof(the_exec.a_syms));
    /* the_exec . a_syms = sizeof( struct nlist) * symbol_number; */
  }

  /*
   * Addresses of frags now reflect addresses we use in the object file.
   * Symbol values are correct.
   * Scan the frags, converting any ".org"s and ".align"s to ".fill"s.
   * Also converting any machine-dependent frags using md_convert_frag();
   */
  subseg_change( SEG_TEXT, 0);

  for (fragP = text_frag_root;  fragP;  fragP = fragP -> fr_next)
    {
      switch (fragP -> fr_type)
	{
	case rs_align:
	case rs_org:
	  fragP -> fr_type = rs_fill;
	  know( fragP -> fr_var == 1 );