m68klinux.c

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/* BFD back-end for linux flavored m68k a.out binaries.
   Copyright 1992, 1993, 1994, 1995, 1996, 1997, 1999, 2000
   Free Software Foundation, Inc.

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.  */

#define	TARGET_PAGE_SIZE 4096
#define ZMAGIC_DISK_BLOCK_SIZE 1024
#define	SEGMENT_SIZE TARGET_PAGE_SIZE
#define TEXT_START_ADDR	0x0
#define N_SHARED_LIB(x) 0
#define BYTES_IN_WORD 4

#define MACHTYPE_OK(mtype) ((mtype) == M_68020 || (mtype) == M_UNKNOWN)

#include "bfd.h"
#include "sysdep.h"
#include "libbfd.h"
#include "aout/aout64.h"
#include "aout/stab_gnu.h"
#include "aout/ar.h"
#include "libaout.h"           /* BFD a.out internal data structures */

#define TARGET_IS_BIG_ENDIAN_P
#define DEFAULT_ARCH bfd_arch_m68k
#define MY(OP) CAT(m68klinux_,OP)
#define TARGETNAME "a.out-m68k-linux"

extern const bfd_target MY(vec);

/* We always generate QMAGIC files in preference to ZMAGIC files.  It
   would be possible to make this a linker option, if that ever
   becomes important.  */

static void MY_final_link_callback
  PARAMS ((bfd *, file_ptr *, file_ptr *, file_ptr *));
static boolean m68klinux_bfd_final_link
  PARAMS ((bfd *, struct bfd_link_info *));
static boolean m68klinux_write_object_contents PARAMS ((bfd *));

static boolean
m68klinux_bfd_final_link (abfd, info)
     bfd *abfd;
     struct bfd_link_info *info;
{
  obj_aout_subformat (abfd) = q_magic_format;
  return NAME(aout,final_link) (abfd, info, MY_final_link_callback);
}

#define MY_bfd_final_link m68klinux_bfd_final_link

/* Set the machine type correctly.  */

static boolean
m68klinux_write_object_contents (abfd)
     bfd *abfd;
{
  struct external_exec exec_bytes;
  struct internal_exec *execp = exec_hdr (abfd);

  N_SET_MACHTYPE (*execp, M_68020);

  obj_reloc_entry_size (abfd) = RELOC_STD_SIZE;

  WRITE_HEADERS(abfd, execp);

  return true;
}

#define MY_write_object_contents m68klinux_write_object_contents

/* Code to link against Linux a.out shared libraries.  */

/* See if a symbol name is a reference to the global offset table.  */

#ifndef GOT_REF_PREFIX
#define	GOT_REF_PREFIX	"__GOT_"
#endif

#define IS_GOT_SYM(name) \
  (strncmp (name, GOT_REF_PREFIX, sizeof GOT_REF_PREFIX - 1) == 0)

/* See if a symbol name is a reference to the procedure linkage table.  */

#ifndef PLT_REF_PREFIX
#define	PLT_REF_PREFIX	"__PLT_"
#endif

#define IS_PLT_SYM(name) \
  (strncmp (name, PLT_REF_PREFIX, sizeof PLT_REF_PREFIX - 1) == 0)

/* This string is used to generate specialized error messages.  */

#ifndef NEEDS_SHRLIB
#define NEEDS_SHRLIB "__NEEDS_SHRLIB_"
#endif

/* This special symbol is a set vector that contains a list of
   pointers to fixup tables.  It will be present in any dynamicly
   linked file.  The linker generated fixup table should also be added
   to the list, and it should always appear in the second slot (the
   first one is a dummy with a magic number that is defined in
   crt0.o).  */

#ifndef SHARABLE_CONFLICTS
#define SHARABLE_CONFLICTS "__SHARABLE_CONFLICTS__"
#endif

/* We keep a list of fixups.  The terminology is a bit strange, but
   each fixup contains two 32 bit numbers.  A regular fixup contains
   an address and a pointer, and at runtime we should store the
   address at the location pointed to by the pointer.  A builtin fixup
   contains two pointers, and we should read the address using one
   pointer and store it at the location pointed to by the other
   pointer.  Builtin fixups come into play when we have duplicate
   __GOT__ symbols for the same variable.  The builtin fixup will copy
   the GOT pointer from one over into the other.  */

struct fixup
{
  struct fixup *next;
  struct linux_link_hash_entry *h;
  bfd_vma value;

  /* Nonzero if this is a jump instruction that needs to be fixed,
     zero if this is just a pointer */
  char jump;

  char builtin;
};

/* We don't need a special hash table entry structure, but we do need
   to keep some information between linker passes, so we use a special
   hash table.  */

struct linux_link_hash_entry
{
  struct aout_link_hash_entry root;
};

struct linux_link_hash_table
{
  struct aout_link_hash_table root;

  /* First dynamic object found in link.  */
  bfd *dynobj;

  /* Number of fixups.  */
  size_t fixup_count;

  /* Number of builtin fixups.  */
  size_t local_builtins;

  /* List of fixups.  */
  struct fixup *fixup_list;
};

static struct bfd_hash_entry *linux_link_hash_newfunc
  PARAMS ((struct bfd_hash_entry *, struct bfd_hash_table *, const char *));
static struct bfd_link_hash_table *linux_link_hash_table_create
  PARAMS ((bfd *));
static struct fixup *new_fixup
  PARAMS ((struct bfd_link_info *, struct linux_link_hash_entry *,
	   bfd_vma, int));
static boolean linux_link_create_dynamic_sections
  PARAMS ((bfd *, struct bfd_link_info *));
static boolean linux_add_one_symbol
  PARAMS ((struct bfd_link_info *, bfd *, const char *, flagword, asection *,
	   bfd_vma, const char *, boolean, boolean,
	   struct bfd_link_hash_entry **));
static boolean linux_tally_symbols
  PARAMS ((struct linux_link_hash_entry *, PTR));
static boolean linux_finish_dynamic_link
  PARAMS ((bfd *, struct bfd_link_info *));

/* Routine to create an entry in an Linux link hash table.  */

static struct bfd_hash_entry *
linux_link_hash_newfunc (entry, table, string)
     struct bfd_hash_entry *entry;
     struct bfd_hash_table *table;
     const char *string;
{
  struct linux_link_hash_entry *ret = (struct linux_link_hash_entry *) entry;

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

  /* Call the allocation method of the superclass.  */
  ret = ((struct linux_link_hash_entry *)
	 NAME(aout,link_hash_newfunc) ((struct bfd_hash_entry *) ret,
				       table, string));
  if (ret != NULL)
    {
      /* Set local fields; there aren't any.  */
    }

  return (struct bfd_hash_entry *) ret;
}

/* Create a Linux link hash table.  */

static struct bfd_link_hash_table *
linux_link_hash_table_create (abfd)
     bfd *abfd;
{
  struct linux_link_hash_table *ret;

  ret = ((struct linux_link_hash_table *)
	 bfd_alloc (abfd, sizeof (struct linux_link_hash_table)));
  if (ret == (struct linux_link_hash_table *) NULL)
    {
      bfd_set_error (bfd_error_no_memory);
      return (struct bfd_link_hash_table *) NULL;
    }
  if (! NAME(aout,link_hash_table_init) (&ret->root, abfd,
					 linux_link_hash_newfunc))
    {
      free (ret);
      return (struct bfd_link_hash_table *) NULL;
    }

  ret->dynobj = NULL;
  ret->fixup_count = 0;
  ret->local_builtins = 0;
  ret->fixup_list = NULL;

  return &ret->root.root;
}

/* Look up an entry in a Linux link hash table.  */

#define linux_link_hash_lookup(table, string, create, copy, follow) \
  ((struct linux_link_hash_entry *) \
   aout_link_hash_lookup (&(table)->root, (string), (create), (copy),\
			  (follow)))

/* Traverse a Linux link hash table.  */

#define linux_link_hash_traverse(table, func, info)			\
  (aout_link_hash_traverse						\
   (&(table)->root,							\
    (boolean (*) PARAMS ((struct aout_link_hash_entry *, PTR))) (func),	\
    (info)))

/* Get the Linux link hash table from the info structure.  This is
   just a cast.  */

#define linux_hash_table(p) ((struct linux_link_hash_table *) ((p)->hash))

/* Store the information for a new fixup.  */

static struct fixup *
new_fixup (info, h, value, builtin)
     struct bfd_link_info *info;
     struct linux_link_hash_entry *h;
     bfd_vma value;
     int builtin;
{
  struct fixup *f;

  f = (struct fixup *) bfd_hash_allocate (&info->hash->table,
					  sizeof (struct fixup));
  if (f == NULL)
    return f;
  f->next = linux_hash_table (info)->fixup_list;
  linux_hash_table (info)->fixup_list = f;
  f->h = h;
  f->value = value;
  f->builtin = builtin;
  f->jump = 0;
  ++linux_hash_table (info)->fixup_count;
  return f;
}

/* We come here once we realize that we are going to link to a shared
   library.  We need to create a special section that contains the
   fixup table, and we ultimately need to add a pointer to this into
   the set vector for SHARABLE_CONFLICTS.  At this point we do not
   know the size of the section, but that's OK - we just need to
   create it for now.  */

static boolean
linux_link_create_dynamic_sections (abfd, info)
     bfd *abfd;
     struct bfd_link_info *info ATTRIBUTE_UNUSED;
{
  flagword flags;
  register asection *s;

  /* Note that we set the SEC_IN_MEMORY flag.  */
  flags = SEC_ALLOC | SEC_LOAD | SEC_HAS_CONTENTS | SEC_IN_MEMORY;

  /* We choose to use the name ".linux-dynamic" for the fixup table.
     Why not? */
  s = bfd_make_section (abfd, ".linux-dynamic");
  if (s == NULL
      || ! bfd_set_section_flags (abfd, s, flags)
      || ! bfd_set_section_alignment (abfd, s, 2))
    return false;
  s->_raw_size = 0;
  s->contents = 0;

  return true;
}

/* Function to add a single symbol to the linker hash table.  This is
   a wrapper around _bfd_generic_link_add_one_symbol which handles the
   tweaking needed for dynamic linking support.  */

static boolean
linux_add_one_symbol (info, abfd, name, flags, section, value, string,
		      copy, collect, hashp)
     struct bfd_link_info *info;
     bfd *abfd;
     const char *name;
     flagword flags;
     asection *section;
     bfd_vma value;
     const char *string;
     boolean copy;
     boolean collect;
     struct bfd_link_hash_entry **hashp;
{
  struct linux_link_hash_entry *h;
  boolean insert;

  /* Look up and see if we already have this symbol in the hash table.
     If we do, and the defining entry is from a shared library, we
     need to create the dynamic sections.

     FIXME: What if abfd->xvec != info->hash->creator?  We may want to
     be able to link Linux a.out and ELF objects together, but serious
     confusion is possible.  */

  insert = false;

  if (! info->relocateable
      && linux_hash_table (info)->dynobj == NULL
      && strcmp (name, SHARABLE_CONFLICTS) == 0
      && (flags & BSF_CONSTRUCTOR) != 0
      && abfd->xvec == info->hash->creator)
    {
      if (! linux_link_create_dynamic_sections (abfd, info))
	return false;
      linux_hash_table (info)->dynobj = abfd;
      insert = true;
    }

  if (bfd_is_abs_section (section)
      && abfd->xvec == info->hash->creator)
    {
      h = linux_link_hash_lookup (linux_hash_table (info), name, false,
				  false, false);
      if (h != NULL
	  && (h->root.root.type == bfd_link_hash_defined
	      || h->root.root.type == bfd_link_hash_defweak))
	{
	  struct fixup *f;

	  if (hashp != NULL)
	    *hashp = (struct bfd_link_hash_entry *) h;

	  f = new_fixup (info, h, value, ! IS_PLT_SYM (name));
	  if (f == NULL)
	    return false;
	  f->jump = IS_PLT_SYM (name);