bfd/bfdwin.c

   1 /* Support for memory-mapped windows into a BFD.
   2    Copyright (C) 1995-2021 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 bool
 108 bfd_get_file_window (bfd *abfd,
 109                      file_ptr offset,
 110                      bfd_size_type size,
 111                      bfd_window *windowp,
 112                      bool 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       offset += abfd->origin;
 154
 155       /* Seek into the file, to ensure it is open if cacheable.  */
 156       if (abfd->iostream == NULL
 157           && (abfd->iovec == NULL
 158               || abfd->iovec->bseek (abfd, offset, SEEK_SET) != 0))
 159         goto free_and_fail;
 160
 161       fd = fileno ((FILE *) abfd->iostream);
 162       /* Compute offsets and size for mmap and for the user's data.  */
 163       offset2 = offset % pagesize;
 164       if (offset2 < 0)
 165         abort ();
 166       file_offset = offset - offset2;
 167       real_size = offset + size - file_offset;
 168       real_size = real_size + pagesize - 1;
 169       real_size -= real_size % pagesize;
 170
 171       /* If we're re-using a memory region, make sure it's big enough.  */
 172       if (i->data != NULL && i->size < size)
 173         {
 174           munmap (i->data, i->size);
 175           i->data = NULL;
 176         }
 177       i->data = mmap (i->data, real_size,
 178                       writable ? PROT_WRITE | PROT_READ : PROT_READ,
 179                       (writable
 180                        ? MAP_FILE | MAP_PRIVATE
 181                        : MAP_FILE | MAP_SHARED),
 182                       fd, file_offset);
 183       if (i->data == (void *) -1)
 184         {
 185           /* An error happened.  Report it, or try using malloc, or
 186              something.  */
 187           bfd_set_error (bfd_error_system_call);
 188           windowp->data = 0;
 189           if (debug_windows)
 190             fprintf (stderr, "\t\tmmap failed!\n");
 191           goto free_and_fail;
 192         }
 193       if (debug_windows)
 194         fprintf (stderr, "\n\tmapped %ld at %p, offset is %ld\n",
 195                  (long) real_size, i->data, (long) offset2);
 196       i->size = real_size;
 197       windowp->data = (bfd_byte *) i->data + offset2;
 198       windowp->size = size;
 199       i->mapped = 1;
 200       i->refcount = 1;
 201       windowp->i = i;
 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_or_free (i->data, size_to_alloc);
 227   if (debug_windows)
 228     fprintf (stderr, "\t-> %p\n", i->data);
 229   if (i->data == NULL)
 230     {
 231       if (size_to_alloc == 0)
 232         {
 233           windowp->i = i;
 234           return true;
 235         }
 236       goto free_and_fail;
 237     }
 238   i->refcount = 1;
 239   if (bfd_seek (abfd, offset, SEEK_SET) != 0)
 240     goto free_and_fail;
 241   i->size = bfd_bread (i->data, size, abfd);
 242   if (i->size != size)
 243     goto free_and_fail;
 244   i->mapped = 0;
 245 #ifdef HAVE_MPROTECT
 246   if (!writable)
 247     {
 248       if (debug_windows)
 249         fprintf (stderr, "\tmprotect (%p, %ld, PROT_READ)\n", i->data,
 250                  (long) i->size);
 251       mprotect (i->data, i->size, PROT_READ);
 252     }
 253 #endif
 254   windowp->data = i->data;
 255   windowp->size = i->size;
 256   windowp->i = i;
 257   return true;
 258
 259  free_and_fail:
 260   /* We have a bfd_window_internal, but an error occurred.  Free it. */
 261   free (i);
 262   return false;
 263 }
 264
 265 #endif /* USE_MMAP */