cofflink.c

来自「基于4个mips核的noc设计」· C语言 代码 · 共 2,243 行 · 第 1/5 页

/* COFF specific linker code.
   Copyright 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001
   Free Software Foundation, Inc.
   Written by Ian Lance Taylor, 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.  */

/* This file contains the COFF backend linker code.  */

#include "bfd.h"
#include "sysdep.h"
#include "bfdlink.h"
#include "libbfd.h"
#include "coff/internal.h"
#include "libcoff.h"

static boolean coff_link_add_object_symbols
  PARAMS ((bfd *, struct bfd_link_info *));
static boolean coff_link_check_archive_element
  PARAMS ((bfd *, struct bfd_link_info *, boolean *));
static boolean coff_link_check_ar_symbols
  PARAMS ((bfd *, struct bfd_link_info *, boolean *));
static boolean coff_link_add_symbols PARAMS ((bfd *, struct bfd_link_info *));
static char *dores_com PARAMS ((char *, bfd *, int));
static char *get_name PARAMS ((char *, char **));
static int process_embedded_commands
  PARAMS ((bfd *, struct bfd_link_info *, bfd *));
static void mark_relocs PARAMS ((struct coff_final_link_info *, bfd *));

/* Return true if SYM is a weak, external symbol.  */
#define IS_WEAK_EXTERNAL(abfd, sym)			\
  ((sym).n_sclass == C_WEAKEXT				\
   || (obj_pe (abfd) && (sym).n_sclass == C_NT_WEAK))

/* Return true if SYM is an external symbol.  */
#define IS_EXTERNAL(abfd, sym)				\
  ((sym).n_sclass == C_EXT || IS_WEAK_EXTERNAL (abfd, sym))

/* Define macros so that the ISFCN, et. al., macros work correctly.
   These macros are defined in include/coff/internal.h in terms of
   N_TMASK, etc.  These definitions require a user to define local
   variables with the appropriate names, and with values from the
   coff_data (abfd) structure.  */

#define N_TMASK n_tmask
#define N_BTSHFT n_btshft
#define N_BTMASK n_btmask

/* Create an entry in a COFF linker hash table.  */

struct bfd_hash_entry *
_bfd_coff_link_hash_newfunc (entry, table, string)
     struct bfd_hash_entry *entry;
     struct bfd_hash_table *table;
     const char *string;
{
  struct coff_link_hash_entry *ret = (struct coff_link_hash_entry *) entry;

  /* Allocate the structure if it has not already been allocated by a
     subclass.  */
  if (ret == (struct coff_link_hash_entry *) NULL)
    ret = ((struct coff_link_hash_entry *)
	   bfd_hash_allocate (table, sizeof (struct coff_link_hash_entry)));
  if (ret == (struct coff_link_hash_entry *) NULL)
    return (struct bfd_hash_entry *) ret;

  /* Call the allocation method of the superclass.  */
  ret = ((struct coff_link_hash_entry *)
	 _bfd_link_hash_newfunc ((struct bfd_hash_entry *) ret,
				 table, string));
  if (ret != (struct coff_link_hash_entry *) NULL)
    {
      /* Set local fields.  */
      ret->indx = -1;
      ret->type = T_NULL;
      ret->class = C_NULL;
      ret->numaux = 0;
      ret->auxbfd = NULL;
      ret->aux = NULL;
    }

  return (struct bfd_hash_entry *) ret;
}

/* Initialize a COFF linker hash table.  */

boolean
_bfd_coff_link_hash_table_init (table, abfd, newfunc)
     struct coff_link_hash_table *table;
     bfd *abfd;
     struct bfd_hash_entry *(*newfunc) PARAMS ((struct bfd_hash_entry *,
						struct bfd_hash_table *,
						const char *));
{
  table->stab_info = NULL;
  return _bfd_link_hash_table_init (&table->root, abfd, newfunc);
}

/* Create a COFF linker hash table.  */

struct bfd_link_hash_table *
_bfd_coff_link_hash_table_create (abfd)
     bfd *abfd;
{
  struct coff_link_hash_table *ret;

  ret = ((struct coff_link_hash_table *)
	 bfd_alloc (abfd, sizeof (struct coff_link_hash_table)));
  if (ret == NULL)
    return NULL;
  if (! _bfd_coff_link_hash_table_init (ret, abfd,
					_bfd_coff_link_hash_newfunc))
    {
      bfd_release (abfd, ret);
      return (struct bfd_link_hash_table *) NULL;
    }
  return &ret->root;
}

/* Create an entry in a COFF debug merge hash table.  */

struct bfd_hash_entry *
_bfd_coff_debug_merge_hash_newfunc (entry, table, string)
     struct bfd_hash_entry *entry;
     struct bfd_hash_table *table;
     const char *string;
{
  struct coff_debug_merge_hash_entry *ret =
    (struct coff_debug_merge_hash_entry *) entry;

  /* Allocate the structure if it has not already been allocated by a
     subclass.  */
  if (ret == (struct coff_debug_merge_hash_entry *) NULL)
    ret = ((struct coff_debug_merge_hash_entry *)
	   bfd_hash_allocate (table,
			      sizeof (struct coff_debug_merge_hash_entry)));
  if (ret == (struct coff_debug_merge_hash_entry *) NULL)
    return (struct bfd_hash_entry *) ret;

  /* Call the allocation method of the superclass.  */
  ret = ((struct coff_debug_merge_hash_entry *)
	 bfd_hash_newfunc ((struct bfd_hash_entry *) ret, table, string));
  if (ret != (struct coff_debug_merge_hash_entry *) NULL)
    {
      /* Set local fields.  */
      ret->types = NULL;
    }

  return (struct bfd_hash_entry *) ret;
}

/* Given a COFF BFD, add symbols to the global hash table as
   appropriate.  */

boolean
_bfd_coff_link_add_symbols (abfd, info)
     bfd *abfd;
     struct bfd_link_info *info;
{
  switch (bfd_get_format (abfd))
    {
    case bfd_object:
      return coff_link_add_object_symbols (abfd, info);
    case bfd_archive:
      return (_bfd_generic_link_add_archive_symbols
	      (abfd, info, coff_link_check_archive_element));
    default:
      bfd_set_error (bfd_error_wrong_format);
      return false;
    }
}

/* Add symbols from a COFF object file.  */

static boolean
coff_link_add_object_symbols (abfd, info)
     bfd *abfd;
     struct bfd_link_info *info;
{
  if (! _bfd_coff_get_external_symbols (abfd))
    return false;
  if (! coff_link_add_symbols (abfd, info))
    return false;

  if (! info->keep_memory)
    {
      if (! _bfd_coff_free_symbols (abfd))
	return false;
    }
  return true;
}

/* Check a single archive element to see if we need to include it in
   the link.  *PNEEDED is set according to whether this element is
   needed in the link or not.  This is called via
   _bfd_generic_link_add_archive_symbols.  */

static boolean
coff_link_check_archive_element (abfd, info, pneeded)
     bfd *abfd;
     struct bfd_link_info *info;
     boolean *pneeded;
{
  if (! _bfd_coff_get_external_symbols (abfd))
    return false;

  if (! coff_link_check_ar_symbols (abfd, info, pneeded))
    return false;

  if (*pneeded)
    {
      if (! coff_link_add_symbols (abfd, info))
	return false;
    }

  if (! info->keep_memory || ! *pneeded)
    {
      if (! _bfd_coff_free_symbols (abfd))
	return false;
    }

  return true;
}

/* Look through the symbols to see if this object file should be
   included in the link.  */

static boolean
coff_link_check_ar_symbols (abfd, info, pneeded)
     bfd *abfd;
     struct bfd_link_info *info;
     boolean *pneeded;
{
  bfd_size_type symesz;
  bfd_byte *esym;
  bfd_byte *esym_end;

  *pneeded = false;

  symesz = bfd_coff_symesz (abfd);
  esym = (bfd_byte *) obj_coff_external_syms (abfd);
  esym_end = esym + obj_raw_syment_count (abfd) * symesz;
  while (esym < esym_end)
    {
      struct internal_syment sym;
      enum coff_symbol_classification classification;

      bfd_coff_swap_sym_in (abfd, (PTR) esym, (PTR) &sym);

      classification = bfd_coff_classify_symbol (abfd, &sym);
      if (classification == COFF_SYMBOL_GLOBAL
	  || classification == COFF_SYMBOL_COMMON)
	{
	  const char *name;
	  char buf[SYMNMLEN + 1];
	  struct bfd_link_hash_entry *h;

	  /* This symbol is externally visible, and is defined by this
             object file.  */

	  name = _bfd_coff_internal_syment_name (abfd, &sym, buf);
	  if (name == NULL)
	    return false;
	  h = bfd_link_hash_lookup (info->hash, name, false, false, true);

	  /* We are only interested in symbols that are currently
	     undefined.  If a symbol is currently known to be common,
	     COFF linkers do not bring in an object file which defines
	     it.  */
	  if (h != (struct bfd_link_hash_entry *) NULL
	      && h->type == bfd_link_hash_undefined)
	    {
	      if (! (*info->callbacks->add_archive_element) (info, abfd, name))
		return false;
	      *pneeded = true;
	      return true;
	    }
	}

      esym += (sym.n_numaux + 1) * symesz;
    }

  /* We do not need this object file.  */
  return true;
}

/* Add all the symbols from an object file to the hash table.  */

static boolean
coff_link_add_symbols (abfd, info)
     bfd *abfd;
     struct bfd_link_info *info;
{
  unsigned int n_tmask = coff_data (abfd)->local_n_tmask;
  unsigned int n_btshft = coff_data (abfd)->local_n_btshft;
  unsigned int n_btmask = coff_data (abfd)->local_n_btmask;
  boolean keep_syms;
  boolean default_copy;
  bfd_size_type symcount;
  struct coff_link_hash_entry **sym_hash;
  bfd_size_type symesz;
  bfd_byte *esym;
  bfd_byte *esym_end;

  /* Keep the symbols during this function, in case the linker needs
     to read the generic symbols in order to report an error message.  */
  keep_syms = obj_coff_keep_syms (abfd);
  obj_coff_keep_syms (abfd) = true;

  if (info->keep_memory)
    default_copy = false;
  else
    default_copy = true;

  symcount = obj_raw_syment_count (abfd);

  /* We keep a list of the linker hash table entries that correspond
     to particular symbols.  */
  sym_hash = ((struct coff_link_hash_entry **)
	      bfd_alloc (abfd,
			 ((size_t) symcount
			  * sizeof (struct coff_link_hash_entry *))));
  if (sym_hash == NULL && symcount != 0)
    goto error_return;
  obj_coff_sym_hashes (abfd) = sym_hash;
  memset (sym_hash, 0,
	  (size_t) symcount * sizeof (struct coff_link_hash_entry *));

  symesz = bfd_coff_symesz (abfd);
  BFD_ASSERT (symesz == bfd_coff_auxesz (abfd));
  esym = (bfd_byte *) obj_coff_external_syms (abfd);
  esym_end = esym + symcount * symesz;
  while (esym < esym_end)
    {
      struct internal_syment sym;
      enum coff_symbol_classification classification;
      boolean copy;

      bfd_coff_swap_sym_in (abfd, (PTR) esym, (PTR) &sym);

      classification = bfd_coff_classify_symbol (abfd, &sym);
      if (classification != COFF_SYMBOL_LOCAL)
	{
	  const char *name;
	  char buf[SYMNMLEN + 1];
	  flagword flags;
	  asection *section;
	  bfd_vma value;
	  boolean addit;

	  /* This symbol is externally visible.  */

	  name = _bfd_coff_internal_syment_name (abfd, &sym, buf);
	  if (name == NULL)
	    goto error_return;

	  /* We must copy the name into memory if we got it from the
             syment itself, rather than the string table.  */
	  copy = default_copy;
	  if (sym._n._n_n._n_zeroes != 0
	      || sym._n._n_n._n_offset == 0)
	    copy = true;

	  value = sym.n_value;

	  switch (classification)
	    {
	    default:
	      abort ();

	    case COFF_SYMBOL_GLOBAL:
	      flags = BSF_EXPORT | BSF_GLOBAL;
	      section = coff_section_from_bfd_index (abfd, sym.n_scnum);
	      if (! obj_pe (abfd))
		value -= section->vma;
	      break;

	    case COFF_SYMBOL_UNDEFINED:
	      flags = 0;
	      section = bfd_und_section_ptr;
	      break;

	    case COFF_SYMBOL_COMMON:
	      flags = BSF_GLOBAL;
	      section = bfd_com_section_ptr;
	      break;

	    case COFF_SYMBOL_PE_SECTION:
	      flags = BSF_SECTION_SYM | BSF_GLOBAL;
	      section = coff_section_from_bfd_index (abfd, sym.n_scnum);
	      break;
	    }

	  if (IS_WEAK_EXTERNAL (abfd, sym))
	    flags = BSF_WEAK;

	  addit = true;

	  /* In the PE format, section symbols actually refer to the
             start of the output section.  We handle them specially
             here.  */
	  if (obj_pe (abfd) && (flags & BSF_SECTION_SYM) != 0)
	    {
	      *sym_hash = coff_link_hash_lookup (coff_hash_table (info),
						 name, false, copy, false);
	      if (*sym_hash != NULL)
		{
		  if (((*sym_hash)->coff_link_hash_flags
		       & COFF_LINK_HASH_PE_SECTION_SYMBOL) == 0
		      && (*sym_hash)->root.type != bfd_link_hash_undefined
		      && (*sym_hash)->root.type != bfd_link_hash_undefweak)
		    (*_bfd_error_handler)
		      ("Warning: symbol `%s' is both section and non-section",
		       name);

		  addit = false;
		}
	    }

	  /* The Microsoft Visual C compiler does string pooling by
	     hashing the constants to an internal symbol name, and
	     relying on the the linker comdat support to discard
	     duplicate names.  However, if one string is a literal and
	     one is a data initializer, one will end up in the .data
	     section and one will end up in the .rdata section.  The
	     Microsoft linker will combine them into the .data
	     section, which seems to be wrong since it might cause the
	     literal to change.

	     As long as there are no external references to the
	     symbols, which there shouldn't be, we can treat the .data
	     and .rdata instances as separate symbols.  The comdat
	     code in the linker will do the appropriate merging.  Here
	     we avoid getting a multiple definition error for one of
	     these special symbols.