bfd/bfdwin.c

   1 /* Support for memory-mapped windows into a BFD.
   2    Copyright 1995, 1996, 2001, 2002, 2003, 2005
   3    Free Software Foundation, Inc.
   4    Written by Cygnus Support.
   5
   6 This file is part of BFD, the Binary File Descriptor library.
   7
   8 This program is free software; you can redistribute it and/or modify
   9 it under the terms of the GNU General Public License as published by
  10 the Free Software Foundation; either version 2 of the License, or
  11 (at your option) any later version.
  12
  13 This program is distributed in the hope that it will be useful,
  14 but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 GNU General Public License for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with this program; if not, write to the Free Software
  20 Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA.  */
  21
  22 #include "sysdep.h"
  23
  24 #include "bfd.h"
  25 #include "libbfd.h"
  26
  27 /* Currently, if USE_MMAP is undefined, none if the window stuff is
  28    used.  Okay, so it's mis-named.  At least the command-line option
  29    "--without-mmap" is more obvious than "--without-windows" or some
  30    such.  */
  31
  32 #ifdef USE_MMAP
  33
  34 #undef HAVE_MPROTECT /* code's not tested yet */
  35
  36 #if HAVE_MMAP || HAVE_MPROTECT || HAVE_MADVISE
  37 #include <sys/mman.h>
  38 #endif
  39
  40 #ifndef MAP_FILE
  41 #define MAP_FILE 0
  42 #endif
  43
  44 static int debug_windows;
  45
  46 /* The idea behind the next and refcount fields is that one mapped
  47    region can suffice for multiple read-only windows or multiple
  48    non-overlapping read-write windows.  It's not implemented yet
  49    though.  */
  50
  51 /*
  52 INTERNAL_DEFINITION
  53
  54 .struct _bfd_window_internal {
  55 .  struct _bfd_window_internal *next;
  56 .  void *data;
  57 .  bfd_size_type size;
  58 .  int refcount : 31;           {* should be enough...  *}
  59 .  unsigned mapped : 1;         {* 1 = mmap, 0 = malloc *}
  60 .};
  61 */
  62
  63 void
  64 bfd_init_window (bfd_window *windowp)
  65 {
  66   windowp->data = 0;
  67   windowp->i = 0;
  68   windowp->size = 0;
  69 }
  70
  71 void
  72 bfd_free_window (bfd_window *windowp)
  73 {
  74   bfd_window_internal *i = windowp->i;
  75   windowp->i = 0;
  76   windowp->data = 0;
  77   if (i == 0)
  78     return;
  79   i->refcount--;
  80   if (debug_windows)
  81     fprintf (stderr, "freeing window @%p<%p,%lx,%p>\n",
  82              windowp, windowp->data, windowp->size, windowp->i);
  83   if (i->refcount != 0)
  84     return;
  85
  86   if (i->mapped)
  87     {
  88 #ifdef HAVE_MMAP
  89       munmap (i->data, i->size);
  90       goto no_free;
  91 #else
  92       abort ();
  93 #endif
  94     }
  95 #ifdef HAVE_MPROTECT
  96   mprotect (i->data, i->size, PROT_READ | PROT_WRITE);
  97 #endif
  98   free (i->data);
  99 #ifdef HAVE_MMAP
 100  no_free:
 101 #endif
 102   i->data = 0;
 103   /* There should be no more references to i at this point.  */
 104   free (i);
 105 }
 106
 107 static int ok_to_map = 1;
 108
 109 bfd_boolean
 110 bfd_get_file_window (bfd *abfd,
 111                      file_ptr offset,
 112                      bfd_size_type size,
 113                      bfd_window *windowp,
 114                      bfd_boolean writable)
 115 {
 116   static size_t pagesize;
 117   bfd_window_internal *i = windowp->i;
 118   bfd_size_type size_to_alloc = size;
 119
 120   if (debug_windows)
 121     fprintf (stderr, "bfd_get_file_window (%p, %6ld, %6ld, %p<%p,%lx,%p>, %d)",
 122              abfd, (long) offset, (long) size,
 123              windowp, windowp->data, (unsigned long) windowp->size,
 124              windowp->i, writable);
 125
 126   /* Make sure we know the page size, so we can be friendly to mmap.  */
 127   if (pagesize == 0)
 128     pagesize = getpagesize ();
 129   if (pagesize == 0)
 130     abort ();
 131
 132   if (i == 0)
 133     {
 134       i = bfd_zmalloc (sizeof (bfd_window_internal));
 135       windowp->i = i;
 136       if (i == 0)
 137         return FALSE;
 138       i->data = 0;
 139     }
 140 #ifdef HAVE_MMAP
 141   if (ok_to_map
 142       && (i->data == 0 || i->mapped == 1)
 143       && (abfd->flags & BFD_IN_MEMORY) == 0)
 144     {
 145       file_ptr file_offset, offset2;
 146       size_t real_size;
 147       int fd;
 148
 149       /* Find the real file and the real offset into it.  */
 150       while (abfd->my_archive != NULL)
 151         {
 152           offset += abfd->origin;
 153           abfd = abfd->my_archive;
 154         }
 155
 156       /* Seek into the file, to ensure it is open if cacheable.  */
 157       if (abfd->iostream == NULL
 158           && (abfd->iovec == NULL
 159               || abfd->iovec->bseek (abfd, offset, SEEK_SET) != 0))
 160         return FALSE;
 161       fd = fileno ((FILE *) abfd->iostream);
 162
 163       /* Compute offsets and size for mmap and for the user's data.  */
 164       offset2 = offset % pagesize;
 165       if (offset2 < 0)
 166         abort ();
 167       file_offset = offset - offset2;
 168       real_size = offset + size - file_offset;
 169       real_size = real_size + pagesize - 1;
 170       real_size -= real_size % pagesize;
 171
 172       /* If we're re-using a memory region, make sure it's big enough.  */
 173       if (i->data && i->size < size)
 174         {
 175           munmap (i->data, i->size);
 176           i->data = 0;
 177         }
 178       i->data = mmap (i->data, real_size,
 179                       writable ? PROT_WRITE | PROT_READ : PROT_READ,
 180                       (writable
 181                        ? MAP_FILE | MAP_PRIVATE
 182                        : MAP_FILE | MAP_SHARED),
 183                       fd, file_offset);
 184       if (i->data == (void *) -1)
 185         {
 186           /* An error happened.  Report it, or try using malloc, or
 187              something.  */
 188           bfd_set_error (bfd_error_system_call);
 189           i->data = 0;
 190           windowp->data = 0;
 191           if (debug_windows)
 192             fprintf (stderr, "\t\tmmap failed!\n");
 193           return FALSE;
 194         }
 195       if (debug_windows)
 196         fprintf (stderr, "\n\tmapped %ld at %p, offset is %ld\n",
 197                  (long) real_size, i->data, (long) offset2);
 198       i->size = real_size;
 199       windowp->data = (bfd_byte *) i->data + offset2;
 200       windowp->size = size;
 201       i->mapped = 1;
 202       return TRUE;
 203     }
 204   else if (debug_windows)
 205     {
 206       if (ok_to_map)
 207         fprintf (stderr, _("not mapping: data=%lx mapped=%d\n"),
 208                  (unsigned long) i->data, (int) i->mapped);
 209       else
 210         fprintf (stderr, _("not mapping: env var not set\n"));
 211     }
 212 #else
 213   ok_to_map = 0;
 214 #endif
 215
 216 #ifdef HAVE_MPROTECT
 217   if (!writable)
 218     {
 219       size_to_alloc += pagesize - 1;
 220       size_to_alloc -= size_to_alloc % pagesize;
 221     }
 222 #endif
 223   if (debug_windows)
 224     fprintf (stderr, "\n\t%s(%6ld)",
 225              i->data ? "realloc" : " malloc", (long) size_to_alloc);
 226   i->data = bfd_realloc (i->data, size_to_alloc);
 227   if (debug_windows)
 228     fprintf (stderr, "\t-> %p\n", i->data);
 229   i->refcount = 1;
 230   if (i->data == NULL)
 231     {
 232       if (size_to_alloc == 0)
 233         return TRUE;
 234       return FALSE;
 235     }
 236   if (bfd_seek (abfd, offset, SEEK_SET) != 0)
 237     return FALSE;
 238   i->size = bfd_bread (i->data, size, abfd);
 239   if (i->size != size)
 240     return FALSE;
 241   i->mapped = 0;
 242 #ifdef HAVE_MPROTECT
 243   if (!writable)
 244     {
 245       if (debug_windows)
 246         fprintf (stderr, "\tmprotect (%p, %ld, PROT_READ)\n", i->data,
 247                  (long) i->size);
 248       mprotect (i->data, i->size, PROT_READ);
 249     }
 250 #endif
 251   windowp->data = i->data;
 252   windowp->size = i->size;
 253   return TRUE;
 254 }
 255
 256 #endif /* USE_MMAP */