bfd/bfdwin.c

   1 /* Support for memory-mapped windows into a BFD.
   2    Copyright 1995, 1996, 2001, 2002, 2003, 2005, 2007
   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 3 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,
  21    MA 02110-1301, USA.  */
  22
  23 #include "sysdep.h"
  24
  25 #include "bfd.h"
  26 #include "libbfd.h"
  27
  28 /* Currently, if USE_MMAP is undefined, none if the window stuff is
  29    used.  Okay, so it's mis-named.  At least the command-line option
  30    "--without-mmap" is more obvious than "--without-windows" or some
  31    such.  */
  32
  33 #ifdef USE_MMAP
  34
  35 #undef HAVE_MPROTECT /* code's not tested yet */
  36
  37 #if HAVE_MMAP || HAVE_MPROTECT || HAVE_MADVISE
  38 #include <sys/mman.h>
  39 #endif
  40
  41 #ifndef MAP_FILE
  42 #define MAP_FILE 0
  43 #endif
  44
  45 static int debug_windows;
  46
  47 /* The idea behind the next and refcount fields is that one mapped
  48    region can suffice for multiple read-only windows or multiple
  49    non-overlapping read-write windows.  It's not implemented yet
  50    though.  */
  51
  52 /*
  53 INTERNAL_DEFINITION
  54
  55 .struct _bfd_window_internal {
  56 .  struct _bfd_window_internal *next;
  57 .  void *data;
  58 .  bfd_size_type size;
  59 .  int refcount : 31;           {* should be enough...  *}
  60 .  unsigned mapped : 1;         {* 1 = mmap, 0 = malloc *}
  61 .};
  62 */
  63
  64 void
  65 bfd_init_window (bfd_window *windowp)
  66 {
  67   windowp->data = 0;
  68   windowp->i = 0;
  69   windowp->size = 0;
  70 }
  71
  72 void
  73 bfd_free_window (bfd_window *windowp)
  74 {
  75   bfd_window_internal *i = windowp->i;
  76   windowp->i = 0;
  77   windowp->data = 0;
  78   if (i == 0)
  79     return;
  80   i->refcount--;
  81   if (debug_windows)
  82     fprintf (stderr, "freeing window @%p<%p,%lx,%p>\n",
  83              windowp, windowp->data, windowp->size, windowp->i);
  84   if (i->refcount != 0)
  85     return;
  86
  87   if (i->mapped)
  88     {
  89 #ifdef HAVE_MMAP
  90       munmap (i->data, i->size);
  91       goto no_free;
  92 #else
  93       abort ();
  94 #endif
  95     }
  96 #ifdef HAVE_MPROTECT
  97   mprotect (i->data, i->size, PROT_READ | PROT_WRITE);
  98 #endif
  99   free (i->data);
 100 #ifdef HAVE_MMAP
 101  no_free:
 102 #endif
 103   i->data = 0;
 104   /* There should be no more references to i at this point.  */
 105   free (i);
 106 }
 107
 108 static int ok_to_map = 1;
 109
 110 bfd_boolean
 111 bfd_get_file_window (bfd *abfd,
 112                      file_ptr offset,
 113                      bfd_size_type size,
 114                      bfd_window *windowp,
 115                      bfd_boolean writable)
 116 {
 117   static size_t pagesize;
 118   bfd_window_internal *i = windowp->i;
 119   bfd_size_type size_to_alloc = size;
 120
 121   if (debug_windows)
 122     fprintf (stderr, "bfd_get_file_window (%p, %6ld, %6ld, %p<%p,%lx,%p>, %d)",
 123              abfd, (long) offset, (long) size,
 124              windowp, windowp->data, (unsigned long) windowp->size,
 125              windowp->i, writable);
 126
 127   /* Make sure we know the page size, so we can be friendly to mmap.  */
 128   if (pagesize == 0)
 129     pagesize = getpagesize ();
 130   if (pagesize == 0)
 131     abort ();
 132
 133   if (i == 0)
 134     {
 135       i = bfd_zmalloc (sizeof (bfd_window_internal));
 136       windowp->i = i;
 137       if (i == 0)
 138         return FALSE;
 139       i->data = 0;
 140     }
 141 #ifdef HAVE_MMAP
 142   if (ok_to_map
 143       && (i->data == 0 || i->mapped == 1)
 144       && (abfd->flags & BFD_IN_MEMORY) == 0)
 145     {
 146       file_ptr file_offset, offset2;
 147       size_t real_size;
 148       int fd;
 149
 150       /* Find the real file and the real offset into it.  */
 151       while (abfd->my_archive != NULL)
 152         {
 153           offset += abfd->origin;
 154           abfd = abfd->my_archive;
 155         }
 156
 157       /* Seek into the file, to ensure it is open if cacheable.  */
 158       if (abfd->iostream == NULL
 159           && (abfd->iovec == NULL
 160               || abfd->iovec->bseek (abfd, offset, SEEK_SET) != 0))
 161         return FALSE;
 162       fd = fileno ((FILE *) abfd->iostream);
 163
 164       /* Compute offsets and size for mmap and for the user's data.  */
 165       offset2 = offset % pagesize;
 166       if (offset2 < 0)
 167         abort ();
 168       file_offset = offset - offset2;
 169       real_size = offset + size - file_offset;
 170       real_size = real_size + pagesize - 1;
 171       real_size -= real_size % pagesize;
 172
 173       /* If we're re-using a memory region, make sure it's big enough.  */
 174       if (i->data && i->size < size)
 175         {
 176           munmap (i->data, i->size);
 177           i->data = 0;
 178         }
 179       i->data = mmap (i->data, real_size,
 180                       writable ? PROT_WRITE | PROT_READ : PROT_READ,
 181                       (writable
 182                        ? MAP_FILE | MAP_PRIVATE
 183                        : MAP_FILE | MAP_SHARED),
 184                       fd, file_offset);
 185       if (i->data == (void *) -1)
 186         {
 187           /* An error happened.  Report it, or try using malloc, or
 188              something.  */
 189           bfd_set_error (bfd_error_system_call);
 190           i->data = 0;
 191           windowp->data = 0;
 192           if (debug_windows)
 193             fprintf (stderr, "\t\tmmap failed!\n");
 194           return FALSE;
 195         }
 196       if (debug_windows)
 197         fprintf (stderr, "\n\tmapped %ld at %p, offset is %ld\n",
 198                  (long) real_size, i->data, (long) offset2);
 199       i->size = real_size;
 200       windowp->data = (bfd_byte *) i->data + offset2;
 201       windowp->size = size;
 202       i->mapped = 1;
 203       return TRUE;
 204     }
 205   else if (debug_windows)
 206     {
 207       if (ok_to_map)
 208         fprintf (stderr, _("not mapping: data=%lx mapped=%d\n"),
 209                  (unsigned long) i->data, (int) i->mapped);
 210       else
 211         fprintf (stderr, _("not mapping: env var not set\n"));
 212     }
 213 #else
 214   ok_to_map = 0;
 215 #endif
 216
 217 #ifdef HAVE_MPROTECT
 218   if (!writable)
 219     {
 220       size_to_alloc += pagesize - 1;
 221       size_to_alloc -= size_to_alloc % pagesize;
 222     }
 223 #endif
 224   if (debug_windows)
 225     fprintf (stderr, "\n\t%s(%6ld)",
 226              i->data ? "realloc" : " malloc", (long) size_to_alloc);
 227   i->data = bfd_realloc (i->data, size_to_alloc);
 228   if (debug_windows)
 229     fprintf (stderr, "\t-> %p\n", i->data);
 230   i->refcount = 1;
 231   if (i->data == NULL)
 232     {
 233       if (size_to_alloc == 0)
 234         return TRUE;
 235       return FALSE;
 236     }
 237   if (bfd_seek (abfd, offset, SEEK_SET) != 0)
 238     return FALSE;
 239   i->size = bfd_bread (i->data, size, abfd);
 240   if (i->size != size)
 241     return FALSE;
 242   i->mapped = 0;
 243 #ifdef HAVE_MPROTECT
 244   if (!writable)
 245     {
 246       if (debug_windows)
 247         fprintf (stderr, "\tmprotect (%p, %ld, PROT_READ)\n", i->data,
 248                  (long) i->size);
 249       mprotect (i->data, i->size, PROT_READ);
 250     }
 251 #endif
 252   windowp->data = i->data;
 253   windowp->size = i->size;
 254   return TRUE;
 255 }
 256
 257 #endif /* USE_MMAP */