ld.c

早期freebsd实现

	  break;

	case N_SETB:
	  reftype = "is a BSS set element";
	  break;

	case N_SETA:
	  reftype = "is an absolute set element";
	  break;

	case N_SETV:
	  reftype = "defined in data section as vector";
	  break;

	case N_INDR:
	  reftype = (char *) alloca (23
				     + strlen ((nlist_p + 1)->n_un.n_strx
					       + entry->strings));
	  sprintf (reftype, "defined equivalent to %s",
		   (nlist_p + 1)->n_un.n_strx + entry->strings);
	  break;

#ifdef sequent
	case N_SHUNDF:
	  reftype = "shared undf";
	  break;

/* These conflict with cases above.
	case N_SHDATA:
	  reftype = "shared data";
	  break;

	case N_SHBSS:
	  reftype = "shared BSS";
	  break;
*/
	default:
	  reftype = "I don't know this type";
	  break;
#endif
	}

      fprintf (stderr, "symbol %s %s in ", sp->name, reftype);
      print_file_name (entry, stderr);
      fprintf (stderr, "\n");
    }
}

/* This return 0 if the given file entry's symbol table does *not*
   contain the nlist point entry, and it returns the files entry
   pointer (cast to unsigned long) if it does. */

unsigned long
contains_symbol (entry, n_ptr)
     struct file_entry *entry;
     register struct nlist *n_ptr;
{
  if (n_ptr >= entry->symbols &&
      n_ptr < (entry->symbols
	       + (entry->header.a_syms / sizeof (struct nlist))))
    return (unsigned long) entry;
  return 0;
}


/* Searching libraries */

struct file_entry *decode_library_subfile ();
void linear_library (), symdef_library ();

/* Search the library ENTRY, already open on descriptor DESC.
   This means deciding which library members to load,
   making a chain of `struct file_entry' for those members,
   and entering their global symbols in the hash table.  */

void
search_library (desc, entry)
     int desc;
     struct file_entry *entry;
{
  int member_length;
  register char *name;
  register struct file_entry *subentry;

  if (!undefined_global_sym_count) return;

  /* Examine its first member, which starts SARMAG bytes in.  */
  subentry = decode_library_subfile (desc, entry, SARMAG, &member_length);
  if (!subentry) return;

  name = subentry->filename;
  free (subentry);

  /* Search via __.SYMDEF if that exists, else linearly.  */

  if (!strcmp (name, "__.SYMDEF"))
    symdef_library (desc, entry, member_length);
  else
    linear_library (desc, entry);
}

/* Construct and return a file_entry for a library member.
   The library's file_entry is library_entry, and the library is open on DESC.
   SUBFILE_OFFSET is the byte index in the library of this member's header.
   We store the length of the member into *LENGTH_LOC.  */

struct file_entry *
decode_library_subfile (desc, library_entry, subfile_offset, length_loc)
     int desc;
     struct file_entry *library_entry;
     int subfile_offset;
     int *length_loc;
{
  int bytes_read;
  register int namelen;
  int member_length;
  register char *name;
  struct ar_hdr hdr1;
  register struct file_entry *subentry;

  lseek (desc, subfile_offset, 0);

  bytes_read = read (desc, &hdr1, sizeof hdr1);
  if (!bytes_read)
    return 0;		/* end of archive */

  if (sizeof hdr1 != bytes_read)
    fatal_with_file ("malformed library archive ", library_entry);

  if (sscanf (hdr1.ar_size, "%d", &member_length) != 1)
    fatal_with_file ("malformatted header of archive member in ", library_entry);

  subentry = (struct file_entry *) xmalloc (sizeof (struct file_entry));
  bzero (subentry, sizeof (struct file_entry));

  for (namelen = 0;
       namelen < sizeof hdr1.ar_name
       && hdr1.ar_name[namelen] != 0 && hdr1.ar_name[namelen] != ' '
       && hdr1.ar_name[namelen] != '/';
       namelen++);

  name = (char *) xmalloc (namelen+1);
  strncpy (name, hdr1.ar_name, namelen);
  name[namelen] = 0;

  subentry->filename = name;
  subentry->local_sym_name = name;
  subentry->symbols = 0;
  subentry->strings = 0;
  subentry->subfiles = 0;
  subentry->starting_offset = subfile_offset + sizeof hdr1;
  subentry->superfile = library_entry;
  subentry->library_flag = 0;
  subentry->header_read_flag = 0;
  subentry->just_syms_flag = 0;
  subentry->chain = 0;
  subentry->total_size = member_length;

  (*length_loc) = member_length;

  return subentry;
}

int subfile_wanted_p ();

/* Search a library that has a __.SYMDEF member.
   DESC is a descriptor on which the library is open.
     The file pointer is assumed to point at the __.SYMDEF data.
   ENTRY is the library's file_entry.
   MEMBER_LENGTH is the length of the __.SYMDEF data.  */

void
symdef_library (desc, entry, member_length)
     int desc;
     struct file_entry *entry;
     int member_length;
{
  int *symdef_data = (int *) xmalloc (member_length);
  register struct symdef *symdef_base;
  char *sym_name_base;
  int number_of_symdefs;
  int length_of_strings;
  int not_finished;
  int bytes_read;
  register int i;
  struct file_entry *prev = 0;
  int prev_offset = 0;

  bytes_read = read (desc, symdef_data, member_length);
  if (bytes_read != member_length)
    fatal_with_file ("malformatted __.SYMDEF in ", entry);

  number_of_symdefs = *symdef_data / sizeof (struct symdef);
  if (number_of_symdefs < 0 ||
       number_of_symdefs * sizeof (struct symdef) + 2 * sizeof (int) > member_length)
    fatal_with_file ("malformatted __.SYMDEF in ", entry);

  symdef_base = (struct symdef *) (symdef_data + 1);
  length_of_strings = *(int *) (symdef_base + number_of_symdefs);

  if (length_of_strings < 0
      || number_of_symdefs * sizeof (struct symdef) + length_of_strings
	  + 2 * sizeof (int) > member_length)
    fatal_with_file ("malformatted __.SYMDEF in ", entry);

  sym_name_base = sizeof (int) + (char *) (symdef_base + number_of_symdefs);

  /* Check all the string indexes for validity.  */

  for (i = 0; i < number_of_symdefs; i++)
    {
      register int index = symdef_base[i].symbol_name_string_index;
      if (index < 0 || index >= length_of_strings
	  || (index && *(sym_name_base + index - 1)))
	fatal_with_file ("malformatted __.SYMDEF in ", entry);
    }

  /* Search the symdef data for members to load.
     Do this until one whole pass finds nothing to load.  */

  not_finished = 1;
  while (not_finished)
    {
      not_finished = 0;

      /* Scan all the symbols mentioned in the symdef for ones that we need.
	 Load the library members that contain such symbols.  */

      for (i = 0;
	   (i < number_of_symdefs
	    && (undefined_global_sym_count || common_defined_global_count));
	   i++)
	if (symdef_base[i].symbol_name_string_index >= 0)
	  {
	    register symbol *sp;

	    sp = getsym_soft (sym_name_base
			      + symdef_base[i].symbol_name_string_index);

	    /* If we find a symbol that appears to be needed, think carefully
	       about the archive member that the symbol is in.  */

	    /*
	     * Per Mike Karels' recommendation, we no longer load library
	     * files if the only reference(s) that would be satisfied are
	     * 'common' references.  This prevents some problems with name
	     * pollution (e.g. a global common 'utime' linked to a function).
	     */
	    if (sp && sp->referenced && !sp->defined)
	      {
		int junk;
		register int j;
		register int offset = symdef_base[i].library_member_offset;
		struct file_entry *subentry;

		/* Don't think carefully about any archive member
		   more than once in a given pass.  */

		if (prev_offset == offset)
		  continue;
		prev_offset = offset;

		/* Read the symbol table of the archive member.  */

		subentry = decode_library_subfile (desc, entry, offset, &junk);
		if (subentry == 0)
		  fatal ("invalid offset for %s in symbol table of %s",
			 sym_name_base
			 + symdef_base[i].symbol_name_string_index,
			 entry->filename);
		read_entry_symbols (desc, subentry);
		subentry->strings = (char *) malloc (subentry->string_size);
		read_entry_strings (desc, subentry);

		/* Now scan the symbol table and decide whether to load.  */

		if (!subfile_wanted_p (subentry))
		  {
		    free (subentry->symbols);
		    free (subentry);
		  }
		else
		  {
		    /* This member is needed; load it.
		       Since we are loading something on this pass,
		       we must make another pass through the symdef data.  */

		    not_finished = 1;

		    enter_file_symbols (subentry);

		    if (prev)
		      prev->chain = subentry;
		    else entry->subfiles = subentry;
		    prev = subentry;

		    /* Clear out this member's symbols from the symdef data
		       so that following passes won't waste time on them.  */

		    for (j = 0; j < number_of_symdefs; j++)
		      {
			if (symdef_base[j].library_member_offset == offset)
			  symdef_base[j].symbol_name_string_index = -1;
		      }
		  }

		/* We'll read the strings again if we need them again.  */
		free (subentry->strings);
		subentry->strings = 0;
	      }
	  }
    }

  free (symdef_data);
}

/* Search a library that has no __.SYMDEF.
   ENTRY is the library's file_entry.
   DESC is the descriptor it is open on.  */

void
linear_library (desc, entry)
     int desc;
     struct file_entry *entry;
{
  register struct file_entry *prev = 0;
  register int this_subfile_offset = SARMAG;

  while (undefined_global_sym_count || common_defined_global_count)
    {
      int member_length;
      register struct file_entry *subentry;

      subentry = decode_library_subfile (desc, entry, this_subfile_offset,
					 &member_length);

      if (!subentry) return;

      read_entry_symbols (desc, subentry);
      subentry->strings = (char *) alloca (subentry->string_size);
      read_entry_strings (desc, subentry);

      if (!subfile_wanted_p (subentry))
	{
	  free (subentry->symbols);
	  free (subentry);
	}
      else
	{
	  enter_file_symbols (subentry);

	  if (prev)
	    prev->chain = subentry;
	  else entry->subfiles = subentry;
	  prev = subentry;
	  subentry->strings = 0; /* Since space will dissapear on return */
	}

      this_subfile_offset += member_length + sizeof (struct ar_hdr);
      if (this_subfile_offset & 1) this_subfile_offset++;
    }
}

/* ENTRY is an entry for a library member.
   Its symbols have been read into core, but not entered.
   Return nonzero if we ought to load this member.  */

int
subfile_wanted_p (entry)
     struct file_entry *entry;
{
  register struct nlist *p;
  register struct nlist *end
    = entry->symbols + entry->header.a_syms / sizeof (struct nlist);
#ifdef DOLLAR_KLUDGE
  register int dollar_cond = 0;
#endif

  for (p = entry->symbols; p < end; p++)
    {
      register int type = p->n_type;
      register char *name = p->n_un.n_strx + entry->strings;

      /* If the symbol has an interesting definition, we could
	 potentially want it.  */
      if (type & N_EXT
	  && (type != (N_UNDF | N_EXT) || p->n_value

#ifdef DOLLAR_KLUDGE
	       || name[1] == '$'
#endif
	      )
	  && !SET_ELEMENT_P (type)
	  && !set_element_prefixed_p (name))
	{
	  register symbol *sp = getsym_soft (name);

#ifdef DOLLAR_KLUDGE
	  if (name[1] == '$')
	    {
	      sp = getsym_soft (&name[2]);
	      dollar_cond = 1;
	      if (!sp) continue;
	      if (sp->referenced)
		{
		  if (write_map)
		    {
		      print_file_name (entry, stdout);
		      fprintf (stdout, " needed due to $-conditional %s\n", name);
		    }
		  return 1;
		}
	      continue;
	    }
#endif

	  /* If this symbol has not been hashed, we can't be looking for it. */

	  if (!sp) continue;

	  /*
	   * We don't load a file if it merely satisfies a common reference
	   * (see explanation above in symdef_library()).
	   */
	  if (sp->referenced && !sp->defined)
	    {
	      /* This is a symbol we are looking for.  It is either
	         not yet defined or defined as a common.  */
#ifdef DOLLAR_KLUDGE
	      if (dollar_cond) continue;
#endif
	      if (type == (N_UNDF | N_EXT))
		{
		  /* Symbol being defined as common.
		     Remember this, but don't load subfile just for this.  */

		  /* If it didn't used to be common, up the count of
		     common symbols.  */
		  if (!sp->max_common_size)
		    common_defined_global_count++;

		  if (sp->max_common_size < p->n_value)
		    sp->max_common_size = p->n_value;
		  if (!sp->defined)
		    undefined_global_sym_count--;
		  sp->defined = 1;
		  continue;
		}

	      if (write_map)
		{
		  print_file_name (entry, stdout);
		  fprintf (stdout, " needed due to %s\n", sp->name);
		}
	      return 1;
	    }
	}
    }

  return 0;
}

void consider_file_section_lengths (), relocate_file_addresses ();

/* Having entered all the global symbols and found the sizes of sections
   of all files to be linked, make all appropriate deductions from this data.

   We propagate global