bfd/bfdwin.c

   1 /* Support for memory-mapped windows into a BFD.
   2    Copyright (C) 1995-2018 Free Software Foundation, Inc.
   3    Written by Cygnus Support.
   4
   5    This file is part of BFD, the Binary File Descriptor library.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program; if not, write to the Free Software
  19    Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  20    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 of the window stuff is
  28    used.  Enabled by --with-mmap.  */
  29
  30 #ifdef USE_MMAP
  31
  32 #undef HAVE_MPROTECT /* code's not tested yet */
  33
  34 #if HAVE_MMAP || HAVE_MPROTECT || HAVE_MADVISE
  35 #include <sys/mman.h>
  36 #endif
  37
  38 #ifndef MAP_FILE
  39 #define MAP_FILE 0
  40 #endif
  41
  42 static int debug_windows;
  43
  44 /* The idea behind the next and refcount fields is that one mapped
  45    region can suffice for multiple read-only windows or multiple
  46    non-overlapping read-write windows.  It's not implemented yet
  47    though.  */
  48
  49 /*
  50 INTERNAL_DEFINITION
  51
  52 .struct _bfd_window_internal {
  53 .  struct _bfd_window_internal *next;
  54 .  void *data;
  55 .  bfd_size_type size;
  56 .  int refcount : 31;           {* should be enough...  *}
  57 .  unsigned mapped : 1;         {* 1 = mmap, 0 = malloc *}
  58 .};
  59 */
  60
  61 void
  62 bfd_init_window (bfd_window *windowp)
  63 {
  64   windowp->data = 0;
  65   windowp->i = 0;
  66   windowp->size = 0;
  67 }
  68
  69 void
  70 bfd_free_window (bfd_window *windowp)
  71 {
  72   bfd_window_internal *i = windowp->i;
  73   windowp->i = 0;
  74   windowp->data = 0;
  75   if (i == 0)
  76     return;
  77   i->refcount--;
  78   if (debug_windows)
  79     fprintf (stderr, "freeing window @%p<%p,%lx,%p>\n",
  80              windowp, windowp->data, (unsigned long) windowp->size, windowp->i);
  81   if (i->refcount != 0)
  82     return;
  83
  84   if (i->mapped)
  85     {
  86 #ifdef HAVE_MMAP
  87       munmap (i->data, i->size);
  88       goto no_free;
  89 #else
  90       abort ();
  91 #endif
  92     }
  93 #ifdef HAVE_MPROTECT
  94   mprotect (i->data, i->size, PROT_READ | PROT_WRITE);
  95 #endif
  96   free (i->data);
  97 #ifdef HAVE_MMAP
  98  no_free:
  99 #endif
 100   i->data = 0;
 101   /* There should be no more references to i at this point.  */
 102   free (i);
 103 }
 104
 105 static int ok_to_map = 1;
 106
 107 bfd_boolean
 108 bfd_get_file_window (bfd *abfd,
 109                      file_ptr offset,
 110                      bfd_size_type size,
 111                      bfd_window *windowp,
 112                      bfd_boolean writable)
 113 {
 114   static size_t pagesize;
 115   bfd_window_internal *i = windowp->i;
 116   bfd_size_type size_to_alloc = size;
 117
 118   if (debug_windows)
 119     fprintf (stderr, "bfd_get_file_window (%p, %6ld, %6ld, %p<%p,%lx,%p>, %d)",
 120              abfd, (long) offset, (long) size,
 121              windowp, windowp->data, (unsigned long) windowp->size,
 122              windowp->i, writable);
 123
 124   /* Make sure we know the page size, so we can be friendly to mmap.  */
 125   if (pagesize == 0)
 126     pagesize = getpagesize ();
 127   if (pagesize == 0)
 128     abort ();
 129
 130   if (i == NULL)
 131     {
 132       i = bfd_zmalloc (sizeof (bfd_window_internal));
 133       if (i == NULL)
 134         return FALSE;
 135       i->data = NULL;
 136     }
 137 #ifdef HAVE_MMAP
 138   if (ok_to_map
 139       && (i->data == NULL || i->mapped == 1)
 140       && (abfd->flags & BFD_IN_MEMORY) == 0)
 141     {
 142       file_ptr file_offset, offset2;
 143       size_t real_size;
 144       int fd;
 145
 146       /* Find the real file and the real offset into it.  */
 147       while (abfd->my_archive != NULL
 148              && !bfd_is_thin_archive (abfd->my_archive))
 149         {
 150           offset += abfd->origin;
 151           abfd = abfd->my_archive;
 152         }
 153
 154       /* Seek into the file, to ensure it is open if cacheable.  */
 155       if (abfd->iostream == NULL
 156           && (abfd->iovec == NULL
 157               || abfd->iovec->bseek (abfd, offset, SEEK_SET) != 0))
 158         goto free_and_fail;
 159
 160       fd = fileno ((FILE *) abfd->iostream);
 161       /* Compute offsets and size for mmap and for the user's data.  */
 162       offset2 = offset % pagesize;
 163       if (offset2 < 0)
 164         abort ();
 165       file_offset = offset - offset2;
 166       real_size = offset + size - file_offset;
 167       real_size = real_size + pagesize - 1;
 168       real_size -= real_size % pagesize;
 169
 170       /* If we're re-using a memory region, make sure it's big enough.  */
 171       if (i->data != NULL && i->size < size)
 172         {
 173           munmap (i->data, i->size);
 174           i->data = NULL;
 175         }
 176       i->data = mmap (i->data, real_size,
 177                       writable ? PROT_WRITE | PROT_READ : PROT_READ,
 178                       (writable
 179                        ? MAP_FILE | MAP_PRIVATE
 180                        : MAP_FILE | MAP_SHARED),
 181                       fd, file_offset);
 182       if (i->data == (void *) -1)
 183         {
 184           /* An error happened.  Report it, or try using malloc, or
 185              something.  */
 186           bfd_set_error (bfd_error_system_call);
 187           windowp->data = 0;
 188           if (debug_windows)
 189             fprintf (stderr, "\t\tmmap failed!\n");
 190           goto free_and_fail;
 191         }
 192       if (debug_windows)
 193         fprintf (stderr, "\n\tmapped %ld at %p, offset is %ld\n",
 194                  (long) real_size, i->data, (long) offset2);
 195       i->size = real_size;
 196       windowp->data = (bfd_byte *) i->data + offset2;
 197       windowp->size = size;
 198       i->mapped = 1;
 199       i->refcount = 1;
 200       windowp->i = i;
 201       return TRUE;
 202     }
 203   else if (debug_windows)
 204     {
 205       if (ok_to_map)
 206         fprintf (stderr, _("not mapping: data=%lx mapped=%d\n"),
 207                  (unsigned long) i->data, (int) i->mapped);
 208       else
 209         fprintf (stderr, _("not mapping: env var not set\n"));
 210     }
 211 #else
 212   ok_to_map = 0;
 213 #endif
 214
 215 #ifdef HAVE_MPROTECT
 216   if (!writable)
 217     {
 218       size_to_alloc += pagesize - 1;
 219       size_to_alloc -= size_to_alloc % pagesize;
 220     }
 221 #endif
 222   if (debug_windows)
 223     fprintf (stderr, "\n\t%s(%6ld)",
 224              i->data ? "realloc" : " malloc", (long) size_to_alloc);
 225   i->data = bfd_realloc_or_free (i->data, size_to_alloc);
 226   if (debug_windows)
 227     fprintf (stderr, "\t-> %p\n", i->data);
 228   if (i->data == NULL)
 229     {
 230       if (size_to_alloc == 0)
 231         {
 232           windowp->i = i;
 233           return TRUE;
 234         }
 235       goto free_and_fail;
 236     }
 237   i->refcount = 1;
 238   if (bfd_seek (abfd, offset, SEEK_SET) != 0)
 239     goto free_and_fail;
 240   i->size = bfd_bread (i->data, size, abfd);
 241   if (i->size != size)
 242     goto free_and_fail;
 243   i->mapped = 0;
 244 #ifdef HAVE_MPROTECT
 245   if (!writable)
 246     {
 247       if (debug_windows)
 248         fprintf (stderr, "\tmprotect (%p, %ld, PROT_READ)\n", i->data,
 249                  (long) i->size);
 250       mprotect (i->data, i->size, PROT_READ);
 251     }
 252 #endif
 253   windowp->data = i->data;
 254   windowp->size = i->size;
 255   windowp->i = i;
 256   return TRUE;
 257
 258  free_and_fail:
 259   /* We have a bfd_window_internal, but an error occurred.  Free it. */
 260   free (i);
 261   return FALSE;
 262 }
 263
 264 #endif /* USE_MMAP */