write.c

早期freebsd实现

	  know( fragP -> fr_next );
	  fragP -> fr_offset
	    =     fragP -> fr_next -> fr_address
	      -   fragP -> fr_address
		- fragP -> fr_fix;
	  break;

	case rs_fill:
	  break;

	case rs_machine_dependent:
	  md_convert_frag (fragP);
	  /*
	   * After md_convert_frag, we make the frag into a ".space 0".
	   * Md_convert_frag() should set up any fixSs and constants
	   * required.
	   */
	  frag_wane (fragP);
	  break;

#ifndef WORKING_DOT_WORD
	case rs_broken_word:
	  {
	    struct broken_word *lie;
	    extern md_short_jump_size;
	    extern md_long_jump_size;

	    if(fragP->fr_subtype) {
	      fragP->fr_fix+=md_short_jump_size;
	      for(lie=(struct broken_word *)(fragP->fr_symbol);lie && lie->dispfrag==fragP;lie=lie->next_broken_word)
		if(lie->added==1)
		  fragP->fr_fix+=md_long_jump_size;
	    }
	    frag_wane(fragP);
	  }
	  break;
#endif

	default:
	  BAD_CASE( fragP -> fr_type );
	  break;
	}			/* switch (fr_type) */
    }				/* for each frag. */

#ifndef WORKING_DOT_WORD
    {
      struct broken_word *lie;
      struct broken_word **prevP;

      prevP= &broken_words;
      for(lie=broken_words; lie; lie=lie->next_broken_word)
	if(!lie->added) {
#if defined(SPARC) || defined(I860)
	  fix_new(	lie->frag,  lie->word_goes_here - lie->frag->fr_literal,
	  		2,  lie->add,
			lie->sub,  lie->addnum,
			0,  NO_RELOC);
#endif
#ifdef NS32K
	  fix_new_ns32k(lie->frag,
	  		lie->word_goes_here - lie->frag->fr_literal,
			2,
			lie->add,
			lie->sub,
			lie->addnum,
			0, 0, 2, 0, 0);
#endif
#if !defined(SPARC) && !defined(NS32K) && !defined(I860)
	  fix_new(	lie->frag,  lie->word_goes_here - lie->frag->fr_literal,
	  		2,  lie->add,
			lie->sub,  lie->addnum,
			0);
#endif
	  /* md_number_to_chars(lie->word_goes_here,
			       lie->add->sy_value
			       + lie->addnum
			       - (lie->sub->sy_value),
			     2); */
	  *prevP=lie->next_broken_word;
	} else
	  prevP= &(lie->next_broken_word);

      for(lie=broken_words;lie;) {
	struct broken_word *untruth;
	char	*table_ptr;
	long	table_addr;
	long	from_addr,
		to_addr;
	int	n,
		m;

	extern	md_short_jump_size;
	extern	md_long_jump_size;
	void	md_create_short_jump();
	void	md_create_long_jump();



	fragP=lie->dispfrag;

	/* Find out how many broken_words go here */
	n=0;
	for(untruth=lie;untruth && untruth->dispfrag==fragP;untruth=untruth->next_broken_word)
	  if(untruth->added==1)
	    n++;

	table_ptr=lie->dispfrag->fr_opcode;
	table_addr=lie->dispfrag->fr_address+(table_ptr - lie->dispfrag->fr_literal);
	/* Create the jump around the long jumps */
	/* This is a short jump from table_ptr+0 to table_ptr+n*long_jump_size */
	from_addr=table_addr;
	to_addr = table_addr + md_short_jump_size + n * md_long_jump_size;
	md_create_short_jump(table_ptr,from_addr,to_addr,lie->dispfrag,lie->add);
	table_ptr+=md_short_jump_size;
	table_addr+=md_short_jump_size;

	for(m=0;lie && lie->dispfrag==fragP;m++,lie=lie->next_broken_word) {
	  if(lie->added==2)
	    continue;
	  /* Patch the jump table */
	  /* This is the offset from ??? to table_ptr+0 */
	  to_addr =   table_addr
	            - (lie->sub->sy_value);
	  md_number_to_chars(lie->word_goes_here,to_addr,2);
	  for(untruth=lie->next_broken_word;untruth && untruth->dispfrag==fragP;untruth=untruth->next_broken_word) {
	    if(untruth->use_jump==lie)
	      md_number_to_chars(untruth->word_goes_here,to_addr,2);
	  }

	  /* Install the long jump */
	  /* this is a long jump from table_ptr+0 to the final target */
	  from_addr=table_addr;
	  to_addr=lie->add->sy_value+lie->addnum;
	  md_create_long_jump(table_ptr,from_addr,to_addr,lie->dispfrag,lie->add);
	  table_ptr+=md_long_jump_size;
	  table_addr+=md_long_jump_size;
	}
      }
    }
#endif
#ifndef	VMS
  /*
   * Scan every FixS performing fixups. We had to wait until now to do
   * this because md_convert_frag() may have made some fixSs.
   */
  /* the_exec . a_trsize
    = sizeof(struct relocation_info) * fixup_segment (text_fix_root, N_TEXT);
  the_exec . a_drsize
    = sizeof(struct relocation_info) * fixup_segment (data_fix_root, N_DATA); */

  tr_siz=sizeof(struct relocation_info) * fixup_segment (text_fix_root, N_TEXT);
  md_number_to_chars((char *)&the_exec.a_trsize, tr_siz ,sizeof(the_exec.a_trsize));
  dr_siz=sizeof(struct relocation_info) * fixup_segment (data_fix_root, N_DATA);
  md_number_to_chars((char *)&the_exec.a_drsize, dr_siz, sizeof(the_exec.a_drsize));
  md_number_to_chars((char *)&the_exec.a_info,omagic,sizeof(the_exec.a_info));
  md_number_to_chars((char *)&the_exec.a_entry,0,sizeof(the_exec.a_entry));

#ifdef EXEC_MACHINE_TYPE
  md_number_to_chars((char *)&the_exec.a_machtype, EXEC_MACHINE_TYPE, sizeof(the_exec.a_machtype));
#endif
#ifdef EXEC_VERSION
  md_number_to_chars((char *)&the_exec.a_version,EXEC_VERSION,sizeof(the_exec.a_version));
#endif
  
  /* the_exec . a_entry = 0; */

  size_of_the_object_file =
    sizeof( the_exec ) +
      text_siz +
        data_siz +
	  syms_siz +
	    tr_siz +
	      dr_siz +
		string_byte_count;
	
  next_object_file_charP
    = the_object_file
      = xmalloc ( size_of_the_object_file );

  output_file_create (out_file_name);

  append (& next_object_file_charP, (char *)(&the_exec), (unsigned long)sizeof(the_exec));

  /*
   * Emit code.
   */
  for (fragP = text_frag_root;  fragP;  fragP = fragP -> fr_next)
    {
      register long int		count;
      register char *		fill_literal;
      register long int		fill_size;

      know( fragP -> fr_type == rs_fill );
      append (& next_object_file_charP, fragP -> fr_literal, (unsigned long)fragP -> fr_fix);
      fill_literal= fragP -> fr_literal + fragP -> fr_fix;
      fill_size   = fragP -> fr_var;
      know( fragP -> fr_offset >= 0 );
      for (count = fragP -> fr_offset;  count;  count --)
	  append (& next_object_file_charP, fill_literal, (unsigned long)fill_size);
    }				/* for each code frag. */

  /*
   * Emit relocations.
   */
  emit_relocations (text_fix_root, (relax_addressT)0);
  emit_relocations (data_fix_root, text_last_frag -> fr_address);
  /*
   * Emit all symbols left in the symbol chain.
   * Any symbol still undefined is made N_EXT.
   */
  for (   symbolP = symbol_rootP;   symbolP;   symbolP = symbolP -> sy_next   )
    {
      register char *	temp;

      temp = symbolP -> sy_nlist . n_un . n_name;
      /* JF fix the numbers up. Call by value RULES! */
      md_number_to_chars((char *)&(symbolP -> sy_nlist  . n_un . n_strx ),symbolP -> sy_name_offset,sizeof(symbolP -> sy_nlist  . n_un . n_strx ));
      md_number_to_chars((char *)&(symbolP->sy_nlist.n_desc),symbolP->sy_nlist.n_desc,sizeof(symbolP -> sy_nlist  . n_desc));
      md_number_to_chars((char *)&(symbolP->sy_nlist.n_value),symbolP->sy_nlist.n_value,sizeof(symbolP->sy_nlist.n_value));
      /* symbolP -> sy_nlist  . n_un . n_strx = symbolP -> sy_name_offset; JF replaced by md above */
      if (symbolP -> sy_type == N_UNDF)
	  symbolP -> sy_type |= N_EXT; /* Any undefined symbols become N_EXT. */
      append (& next_object_file_charP, (char *)(& symbolP -> sy_nlist),
	      (unsigned long)sizeof(struct nlist));
      symbolP -> sy_nlist . n_un . n_name = temp;
    }				/* for each symbol */

  /*
   * next_object_file_charP -> slot for next object byte.
   * Emit strings.
   * Find strings by crawling along symbol table chain.
   */
/* Gotta do md_ byte-ordering stuff for string_byte_count first - KWK */
  md_number_to_chars((char *)&string_byte_count, string_byte_count, sizeof(string_byte_count));

  append (& next_object_file_charP, (char *)&string_byte_count, (unsigned long)sizeof(string_byte_count));
  for (   symbolP = symbol_rootP;   symbolP;   symbolP = symbolP -> sy_next   )
    {
      if (symbolP -> sy_name)
	{			/* Ordinary case: not .stabd. */
	  append (& next_object_file_charP, symbolP -> sy_name,
		  (unsigned long)(strlen (symbolP -> sy_name) + 1));
	}
    }				/* for each symbol */

  know( next_object_file_charP == the_object_file + size_of_the_object_file );

  output_file_append (the_object_file, size_of_the_object_file, out_file_name);

#ifdef DONTDEF
  if (flagseen['G'])		/* GDB symbol file to be appended? */
    {
      gdb_emit (out_file_name);
      gdb_end ();
    }
#endif

  output_file_close (out_file_name);
#else	/* VMS */
  /*
   *	Now do the VMS-dependent part of writing the object file
   */
  VMS_write_object_file(text_siz, data_siz, text_frag_root, data_frag_root);
#endif	/* VMS */
}				/* write_object_file() */

/*
 *			relax_segment()
 *
 * Now we have a segment, not a crowd of sub-segments, we can make fr_address
 * values.
 *
 * Relax the frags.
 *
 * After this, all frags in this segment have addresses that are correct
 * within the segment. Since segments live in different file addresses,
 * these frag addresses may not be the same as final object-file addresses.
 */
#ifndef	VMS
static
#endif	/* not VMS */
void
relax_segment (segment_frag_root, segment_type)
     struct frag *	segment_frag_root;
     segT		segment_type; /* N_DATA or N_TEXT */
{
  register struct frag *	fragP;
  register relax_addressT	address;
  /* register relax_addressT	old_address; JF unused */
  /* register relax_addressT	new_address; JF unused */

  know( segment_type == SEG_DATA || segment_type == SEG_TEXT );

  /* In case md_estimate_size_before_relax() wants to make fixSs. */
  subseg_change (segment_type, 0);

  /*
   * For each frag in segment: count and store  (a 1st guess of) fr_address.
   */
  address = 0;
  for ( fragP = segment_frag_root;   fragP;   fragP = fragP -> fr_next )
    {
      fragP -> fr_address = address;
      address += fragP -> fr_fix;
      switch (fragP -> fr_type)
	{
	case rs_fill:
	  address += fragP -> fr_offset * fragP -> fr_var;
	  break;

	case rs_align:
	  address += relax_align (address, fragP -> fr_offset);
	  break;

	case rs_org:
	  /*
	   * Assume .org is nugatory. It will grow with 1st relax.
	   */
	  break;

	case rs_machine_dependent:
	  address += md_estimate_size_before_relax
	    (fragP, seg_N_TYPE [(int) segment_type]);
	  break;

#ifndef WORKING_DOT_WORD
		/* Broken words don't concern us yet */
	case rs_broken_word:
		break;
#endif

	default:
	  BAD_CASE( fragP -> fr_type );
	  break;
	}			/* switch(fr_type) */
    }				/* for each frag in the segment */

  /*
   * Do relax().
   */
  {
    register long int	stretch; /* May be any size, 0 or negative. */
				/* Cumulative number of addresses we have */
				/* relaxed this pass. */
				/* We may have relaxed more than one address. */
    register long int stretched;  /* Have we stretched on this pass? */
				  /* This is 'cuz stretch may be zero, when,
				     in fact some piece of code grew, and
				     another shrank.  If a branch instruction
				     doesn't fit anymore, we could be scrod */

    do
      {
	stretch = stretched = 0;
	for (fragP = segment_frag_root;  fragP;  fragP = fragP -> fr_next)
	  {
	    register long int	growth;
	    register long int	was_address;
	    /* register long int	var; */
	    register long int	offset;
	    register symbolS *	symbolP;
	    register long int	target;
	    register long int	after;
	    register long int	aim;

	    was_address = fragP -> fr_address;
	    address = fragP -> fr_address += stretch;
	    symbolP = fragP -> fr_symbol;
	    offset = fragP -> fr_offset;
	    /* var = fragP -> fr_var; */
	    switch (fragP -> fr_type)
	      {
	      case rs_fill:	/* .fill never relaxes. */
		growth = 0;
		break;

#ifndef WORKING_DOT_WORD
		/* JF:  This is RMS's idea.  I do *NOT* want to be blamed
		   for it I do not want to write it.  I do not want to have
		   anything to do with it.  This is not the proper way to
		   implement this misfeature. */
	      case rs_broken_word:
	        {
		struct broken_word *lie;
		struct broken_word *untruth;
		extern int md_short_jump_size;
		extern int md_long_jump_size;

			/* Yes this is ugly (storing the broken_word pointer
			   in the symbol slot).  Still, this whole chunk of
			   code is ugly, and I don't feel like doing anything
			   about it.  Think of it as stubbornness in action */
		growth=0;
	        for(lie=(struct broken_word *)(fragP->fr_symbol);
		    lie && lie->dispfrag==fragP;
		    lie=lie->next_broken_word) {

			if(lie->added)
				continue;
			offset=  lie->add->sy_frag->fr_address+lie->add->sy_value + lie->addnum -
				(lie->sub->sy_frag->fr_address+lie->sub->sy_value);
			if(offset<=-32768 || offset>=32767) {
				if(flagseen['k'])
					as_warn(".word %s-%s+%ld didn't fit",lie->add->sy_name,lie->sub->sy_name,lie->addnum);
				lie->added=1;
				if(fragP->fr_subtype==0) {
					fragP->fr_subtype++;
					growth+=md_short_jump_size;
				}
				for(untruth=lie->next_broken_word;untruth && untruth->dispfrag==lie->dispfrag;untruth=untruth->next_broken_word)
					if(untruth->add->sy_frag==lie->add->sy_frag && untruth->add->sy_value==lie->add->sy_value) {
						untruth->added=2;
						untruth->use_jump=lie;
					}
				growth+=md_long_jump_size;
			}
		    }
		}
		break;
#endif