bfd/bfdwin.c

   1 /* Support for memory-mapped windows into a BFD.
   2    Copyright (C) 1995-2024 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 static int debug_windows;
  35
  36 /* The idea behind the next and refcount fields is that one mapped
  37    region can suffice for multiple read-only windows or multiple
  38    non-overlapping read-write windows.  It's not implemented yet
  39    though.  */
  40
  41 /*
  42 INTERNAL
  43 .typedef struct _bfd_window_internal
  44 .{
  45 .  struct _bfd_window_internal *next;
  46 .  void *data;
  47 .  bfd_size_type size;
  48 .  int refcount : 31;           {* should be enough...  *}
  49 .  unsigned mapped : 1;         {* 1 = mmap, 0 = malloc *}
  50 .}
  51 .bfd_window_internal;
  52 .
  53
  54 EXTERNAL
  55 .struct _bfd_window_internal;
  56 .
  57 .typedef struct _bfd_window
  58 .{
  59 .  {* What the user asked for.  *}
  60 .  void *data;
  61 .  bfd_size_type size;
  62 .  {* The actual window used by BFD.  Small user-requested read-only
  63 .     regions sharing a page may share a single window into the object
  64 .     file.  Read-write versions shouldn't until I've fixed things to
  65 .     keep track of which portions have been claimed by the
  66 .     application; don't want to give the same region back when the
  67 .     application wants two writable copies!  *}
  68 .  struct _bfd_window_internal *i;
  69 .}
  70 .bfd_window;
  71 .
  72 */
  73
  74 /*
  75 FUNCTION
  76         bfd_init_window
  77
  78 SYNOPSIS
  79         void bfd_init_window (bfd_window *);
  80
  81 DESCRIPTION
  82         Initialise mmap window.
  83 */
  84
  85 void
  86 bfd_init_window (bfd_window *windowp)
  87 {
  88   windowp->data = 0;
  89   windowp->i = 0;
  90   windowp->size = 0;
  91 }
  92
  93 /*
  94 FUNCTION
  95         bfd_free_window
  96
  97 SYNOPSIS
  98         void bfd_free_window (bfd_window *);
  99
 100 DESCRIPTION
 101         Finalise mmap window struct.
 102 */
 103
 104 void
 105 bfd_free_window (bfd_window *windowp)
 106 {
 107   bfd_window_internal *i = windowp->i;
 108   windowp->i = 0;
 109   windowp->data = 0;
 110   if (i == 0)
 111     return;
 112   i->refcount--;
 113   if (debug_windows)
 114     fprintf (stderr, "freeing window @%p<%p,%lx,%p>\n",
 115              windowp, windowp->data, (unsigned long) windowp->size, windowp->i);
 116   if (i->refcount != 0)
 117     return;
 118
 119   if (i->mapped)
 120     {
 121 #ifdef HAVE_MMAP
 122       munmap (i->data, i->size);
 123       goto no_free;
 124 #else
 125       abort ();
 126 #endif
 127     }
 128 #ifdef HAVE_MPROTECT
 129   mprotect (i->data, i->size, PROT_READ | PROT_WRITE);
 130 #endif
 131   free (i->data);
 132 #ifdef HAVE_MMAP
 133  no_free:
 134 #endif
 135   i->data = 0;
 136   /* There should be no more references to i at this point.  */
 137   free (i);
 138 }
 139
 140 /*
 141 FUNCTION
 142         bfd_get_file_window
 143
 144 SYNOPSIS
 145         bool bfd_get_file_window
 146           (bfd *, file_ptr, bfd_size_type, bfd_window *, bool {*writable*});
 147
 148 DESCRIPTION
 149         mmap from a bfd's iostream.
 150 */
 151
 152 bool
 153 bfd_get_file_window (bfd *abfd,
 154                      file_ptr offset,
 155                      bfd_size_type size,
 156                      bfd_window *windowp,
 157                      bool writable)
 158 {
 159   static int ok_to_map = 1;
 160   static size_t pagesize;
 161   bfd_window_internal *i = windowp->i;
 162   bfd_size_type size_to_alloc = size;
 163
 164   if (debug_windows)
 165     fprintf (stderr, "bfd_get_file_window (%p, %6ld, %6ld, %p<%p,%lx,%p>, %d)",
 166              abfd, (long) offset, (long) size,
 167              windowp, windowp->data, (unsigned long) windowp->size,
 168              windowp->i, writable);
 169
 170   /* Make sure we know the page size, so we can be friendly to mmap.  */
 171   if (pagesize == 0)
 172     pagesize = getpagesize ();
 173   if (pagesize == 0)
 174     abort ();
 175
 176   if (i == NULL)
 177     {
 178       i = bfd_zmalloc (sizeof (bfd_window_internal));
 179       if (i == NULL)
 180         return false;
 181       i->data = NULL;
 182     }
 183 #ifdef HAVE_MMAP
 184   if (ok_to_map
 185       && (i->data == NULL || i->mapped == 1)
 186       && (abfd->flags & BFD_IN_MEMORY) == 0)
 187     {
 188       file_ptr file_offset, offset2;
 189       size_t real_size;
 190       int fd;
 191
 192       /* Find the real file and the real offset into it.  */
 193       while (abfd->my_archive != NULL
 194              && !bfd_is_thin_archive (abfd->my_archive))
 195         {
 196           offset += abfd->origin;
 197           abfd = abfd->my_archive;
 198         }
 199       offset += abfd->origin;
 200
 201       /* Seek into the file, to ensure it is open if cacheable.  */
 202       if (abfd->iostream == NULL
 203           && (abfd->iovec == NULL
 204               || abfd->iovec->bseek (abfd, offset, SEEK_SET) != 0))
 205         goto free_and_fail;
 206
 207       fd = fileno ((FILE *) abfd->iostream);
 208       /* Compute offsets and size for mmap and for the user's data.  */
 209       offset2 = offset % pagesize;
 210       if (offset2 < 0)
 211         abort ();
 212       file_offset = offset - offset2;
 213       real_size = offset + size - file_offset;
 214       real_size = real_size + pagesize - 1;
 215       real_size -= real_size % pagesize;
 216
 217       /* If we're re-using a memory region, make sure it's big enough.  */
 218       if (i->data != NULL && i->size < size)
 219         {
 220           munmap (i->data, i->size);
 221           i->data = NULL;
 222         }
 223       i->data = mmap (i->data, real_size,
 224                       writable ? PROT_WRITE | PROT_READ : PROT_READ,
 225                       (writable
 226                        ? MAP_FILE | MAP_PRIVATE
 227                        : MAP_FILE | MAP_SHARED),
 228                       fd, file_offset);
 229       if (i->data == MAP_FAILED)
 230         {
 231           /* An error happened.  Report it, or try using malloc, or
 232              something.  */
 233           bfd_set_error (bfd_error_system_call);
 234           windowp->data = 0;
 235           if (debug_windows)
 236             fprintf (stderr, "\t\tmmap failed!\n");
 237           goto free_and_fail;
 238         }
 239       if (debug_windows)
 240         fprintf (stderr, "\n\tmapped %ld at %p, offset is %ld\n",
 241                  (long) real_size, i->data, (long) offset2);
 242       i->size = real_size;
 243       windowp->data = (bfd_byte *) i->data + offset2;
 244       windowp->size = size;
 245       i->mapped = 1;
 246       i->refcount = 1;
 247       windowp->i = i;
 248       return true;
 249     }
 250   else if (debug_windows)
 251     {
 252       if (ok_to_map)
 253         fprintf (stderr, _("not mapping: data=%lx mapped=%d\n"),
 254                  (unsigned long) i->data, (int) i->mapped);
 255       else
 256         fprintf (stderr, _("not mapping: env var not set\n"));
 257     }
 258 #else
 259   ok_to_map = 0;
 260 #endif
 261
 262 #ifdef HAVE_MPROTECT
 263   if (!writable)
 264     {
 265       size_to_alloc += pagesize - 1;
 266       size_to_alloc -= size_to_alloc % pagesize;
 267     }
 268 #endif
 269   if (debug_windows)
 270     fprintf (stderr, "\n\t%s(%6ld)",
 271              i->data ? "realloc" : " malloc", (long) size_to_alloc);
 272   i->data = bfd_realloc_or_free (i->data, size_to_alloc);
 273   if (debug_windows)
 274     fprintf (stderr, "\t-> %p\n", i->data);
 275   if (i->data == NULL)
 276     {
 277       if (size_to_alloc == 0)
 278         {
 279           windowp->i = i;
 280           return true;
 281         }
 282       goto free_and_fail;
 283     }
 284   i->refcount = 1;
 285   if (bfd_seek (abfd, offset, SEEK_SET) != 0)
 286     goto free_and_fail;
 287   i->size = bfd_read (i->data, size, abfd);
 288   if (i->size != size)
 289     goto free_and_fail;
 290   i->mapped = 0;
 291 #ifdef HAVE_MPROTECT
 292   if (!writable)
 293     {
 294       if (debug_windows)
 295         fprintf (stderr, "\tmprotect (%p, %ld, PROT_READ)\n", i->data,
 296                  (long) i->size);
 297       mprotect (i->data, i->size, PROT_READ);
 298     }
 299 #endif
 300   windowp->data = i->data;
 301   windowp->size = i->size;
 302   windowp->i = i;
 303   return true;
 304
 305  free_and_fail:
 306   /* We have a bfd_window_internal, but an error occurred.  Free it. */
 307   free (i);
 308   return false;
 309 }
 310
 311 #endif /* USE_MMAP */