source: branches/libc-0.6/src/binutils/bfd/bfdwin.c

/* Support for memory-mapped windows into a BFD.
   Copyright 1995, 1996, 2001, 2002 Free Software Foundation, Inc.
   Written by 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.  */

#include "sysdep.h"

#include "bfd.h"
#include "libbfd.h"

/* Currently, if USE_MMAP is undefined, none if the window stuff is
   used.  Okay, so it's mis-named.  At least the command-line option
   "--without-mmap" is more obvious than "--without-windows" or some
   such.  */

#ifdef USE_MMAP

#undef HAVE_MPROTECT /* code's not tested yet */

#if HAVE_MMAP || HAVE_MPROTECT || HAVE_MADVISE
#include <sys/mman.h>
#endif

#ifndef MAP_FILE
#define MAP_FILE 0
#endif

static int debug_windows;

/* The idea behind the next and refcount fields is that one mapped
   region can suffice for multiple read-only windows or multiple
   non-overlapping read-write windows.  It's not implemented yet
   though.  */

/*
INTERNAL_DEFINITION

.struct _bfd_window_internal {
.  struct _bfd_window_internal *next;
.  PTR data;
.  bfd_size_type size;
.  int refcount : 31;           {* should be enough...  *}
.  unsigned mapped : 1;         {* 1 = mmap, 0 = malloc *}
.};
*/

void
bfd_init_window (windowp)
     bfd_window *windowp;
{
  windowp->data = 0;
  windowp->i = 0;
  windowp->size = 0;
}

void
bfd_free_window (windowp)
     bfd_window *windowp;
{
  bfd_window_internal *i = windowp->i;
  windowp->i = 0;
  windowp->data = 0;
  if (i == 0)
    return;
  i->refcount--;
  if (debug_windows)
    fprintf (stderr, "freeing window @%p<%p,%lx,%p>\n",
             windowp, windowp->data, windowp->size, windowp->i);
  if (i->refcount != 0)
    return;

  if (i->mapped)
    {
#ifdef HAVE_MMAP
      munmap (i->data, i->size);
      goto no_free;
#else
      abort ();
#endif
    }
#ifdef HAVE_MPROTECT
  mprotect (i->data, i->size, PROT_READ | PROT_WRITE);
#endif
  free (i->data);
#ifdef HAVE_MMAP
 no_free:
#endif
  i->data = 0;
  /* There should be no more references to i at this point.  */
  free (i);
}

static int ok_to_map = 1;

bfd_boolean
bfd_get_file_window (abfd, offset, size, windowp, writable)
     bfd *abfd;
     file_ptr offset;
     bfd_size_type size;
     bfd_window *windowp;
     bfd_boolean writable;
{
  static size_t pagesize;
  bfd_window_internal *i = windowp->i;
  bfd_size_type size_to_alloc = size;

  if (debug_windows)
    fprintf (stderr, "bfd_get_file_window (%p, %6ld, %6ld, %p<%p,%lx,%p>, %d)",
             abfd, (long) offset, (long) size,
             windowp, windowp->data, (unsigned long) windowp->size,
             windowp->i, writable);

  /* Make sure we know the page size, so we can be friendly to mmap.  */
  if (pagesize == 0)
    pagesize = getpagesize ();
  if (pagesize == 0)
    abort ();

  if (i == 0)
    {
      i = ((bfd_window_internal *)
           bfd_zmalloc ((bfd_size_type) sizeof (bfd_window_internal)));
      windowp->i = i;
      if (i == 0)
        return FALSE;
      i->data = 0;
    }
#ifdef HAVE_MMAP
  if (ok_to_map
      && (i->data == 0 || i->mapped == 1)
      && (abfd->flags & BFD_IN_MEMORY) == 0)
    {
      file_ptr file_offset, offset2;
      size_t real_size;
      int fd;
      FILE *f;

      /* Find the real file and the real offset into it.  */
      while (abfd->my_archive != NULL)
        {
          offset += abfd->origin;
          abfd = abfd->my_archive;
        }
      f = bfd_cache_lookup (abfd);
      fd = fileno (f);

      /* Compute offsets and size for mmap and for the user's data.  */
      offset2 = offset % pagesize;
      if (offset2 < 0)
        abort ();
      file_offset = offset - offset2;
      real_size = offset + size - file_offset;
      real_size = real_size + pagesize - 1;
      real_size -= real_size % pagesize;

      /* If we're re-using a memory region, make sure it's big enough.  */
      if (i->data && i->size < size)
        {
          munmap (i->data, i->size);
          i->data = 0;
        }
      i->data = mmap (i->data, real_size,
                      writable ? PROT_WRITE | PROT_READ : PROT_READ,
                      (writable
                       ? MAP_FILE | MAP_PRIVATE
                       : MAP_FILE | MAP_SHARED),
                      fd, file_offset);
      if (i->data == (PTR) -1)
        {
          /* An error happened.  Report it, or try using malloc, or
             something.  */
          bfd_set_error (bfd_error_system_call);
          i->data = 0;
          windowp->data = 0;
          if (debug_windows)
            fprintf (stderr, "\t\tmmap failed!\n");
          return FALSE;
        }
      if (debug_windows)
        fprintf (stderr, "\n\tmapped %ld at %p, offset is %ld\n",
                 (long) real_size, i->data, (long) offset2);
      i->size = real_size;
      windowp->data = (PTR) ((bfd_byte *) i->data + offset2);
      windowp->size = size;
      i->mapped = 1;
      return TRUE;
    }
  else if (debug_windows)
    {
      if (ok_to_map)
        fprintf (stderr, _("not mapping: data=%lx mapped=%d\n"),
                 (unsigned long) i->data, (int) i->mapped);
      else
        fprintf (stderr, _("not mapping: env var not set\n"));
    }
#else
  ok_to_map = 0;
#endif

#ifdef HAVE_MPROTECT
  if (!writable)
    {
      size_to_alloc += pagesize - 1;
      size_to_alloc -= size_to_alloc % pagesize;
    }
#endif
  if (debug_windows)
    fprintf (stderr, "\n\t%s(%6ld)",
             i->data ? "realloc" : " malloc", (long) size_to_alloc);
  i->data = (PTR) bfd_realloc (i->data, size_to_alloc);
  if (debug_windows)
    fprintf (stderr, "\t-> %p\n", i->data);
  i->refcount = 1;
  if (i->data == NULL)
    {
      if (size_to_alloc == 0)
        return TRUE;
      return FALSE;
    }
  if (bfd_seek (abfd, offset, SEEK_SET) != 0)
    return FALSE;
  i->size = bfd_bread (i->data, size, abfd);
  if (i->size != size)
    return FALSE;
  i->mapped = 0;
#ifdef HAVE_MPROTECT
  if (!writable)
    {
      if (debug_windows)
        fprintf (stderr, "\tmprotect (%p, %ld, PROT_READ)\n", i->data,
                 (long) i->size);
      mprotect (i->data, i->size, PROT_READ);
    }
#endif
  windowp->data = i->data;
  windowp->size = i->size;
  return TRUE;
}

#endif /* USE_MMAP */