bfd/bfdwin.c

   1 /* Support for memory-mapped windows into a BFD.
   2    Copyright (C) 1995-2023 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
  51 .typedef struct _bfd_window_internal
  52 .{
  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 .bfd_window_internal;
  60 .
  61
  62 EXTERNAL
  63 .struct _bfd_window_internal;
  64 .
  65 .typedef struct _bfd_window
  66 .{
  67 .  {* What the user asked for.  *}
  68 .  void *data;
  69 .  bfd_size_type size;
  70 .  {* The actual window used by BFD.  Small user-requested read-only
  71 .     regions sharing a page may share a single window into the object
  72 .     file.  Read-write versions shouldn't until I've fixed things to
  73 .     keep track of which portions have been claimed by the
  74 .     application; don't want to give the same region back when the
  75 .     application wants two writable copies!  *}
  76 .  struct _bfd_window_internal *i;
  77 .}
  78 .bfd_window;
  79 .
  80 */
  81
  82 /*
  83 FUNCTION
  84         bfd_init_window
  85
  86 SYNOPSIS
  87         void bfd_init_window (bfd_window *);
  88
  89 DESCRIPTION
  90         Initialise mmap window.
  91 */
  92
  93 void
  94 bfd_init_window (bfd_window *windowp)
  95 {
  96   windowp->data = 0;
  97   windowp->i = 0;
  98   windowp->size = 0;
  99 }
 100
 101 /*
 102 FUNCTION
 103         bfd_free_window
 104
 105 SYNOPSIS
 106         void bfd_free_window (bfd_window *);
 107
 108 DESCRIPTION
 109         Finalise mmap window struct.
 110 */
 111
 112 void
 113 bfd_free_window (bfd_window *windowp)
 114 {
 115   bfd_window_internal *i = windowp->i;
 116   windowp->i = 0;
 117   windowp->data = 0;
 118   if (i == 0)
 119     return;
 120   i->refcount--;
 121   if (debug_windows)
 122     fprintf (stderr, "freeing window @%p<%p,%lx,%p>\n",
 123              windowp, windowp->data, (unsigned long) windowp->size, windowp->i);
 124   if (i->refcount != 0)
 125     return;
 126
 127   if (i->mapped)
 128     {
 129 #ifdef HAVE_MMAP
 130       munmap (i->data, i->size);
 131       goto no_free;
 132 #else
 133       abort ();
 134 #endif
 135     }
 136 #ifdef HAVE_MPROTECT
 137   mprotect (i->data, i->size, PROT_READ | PROT_WRITE);
 138 #endif
 139   free (i->data);
 140 #ifdef HAVE_MMAP
 141  no_free:
 142 #endif
 143   i->data = 0;
 144   /* There should be no more references to i at this point.  */
 145   free (i);
 146 }
 147
 148 /*
 149 FUNCTION
 150         bfd_get_file_window
 151
 152 SYNOPSIS
 153         bool bfd_get_file_window
 154           (bfd *, file_ptr, bfd_size_type, bfd_window *, bool {*writable*});
 155
 156 DESCRIPTION
 157         mmap from a bfd's iostream.
 158 */
 159
 160 bool
 161 bfd_get_file_window (bfd *abfd,
 162                      file_ptr offset,
 163                      bfd_size_type size,
 164                      bfd_window *windowp,
 165                      bool writable)
 166 {
 167   static int ok_to_map = 1;
 168   static size_t pagesize;
 169   bfd_window_internal *i = windowp->i;
 170   bfd_size_type size_to_alloc = size;
 171
 172   if (debug_windows)
 173     fprintf (stderr, "bfd_get_file_window (%p, %6ld, %6ld, %p<%p,%lx,%p>, %d)",
 174              abfd, (long) offset, (long) size,
 175              windowp, windowp->data, (unsigned long) windowp->size,
 176              windowp->i, writable);
 177
 178   /* Make sure we know the page size, so we can be friendly to mmap.  */
 179   if (pagesize == 0)
 180     pagesize = getpagesize ();
 181   if (pagesize == 0)
 182     abort ();
 183
 184   if (i == NULL)
 185     {
 186       i = bfd_zmalloc (sizeof (bfd_window_internal));
 187       if (i == NULL)
 188         return false;
 189       i->data = NULL;
 190     }
 191 #ifdef HAVE_MMAP
 192   if (ok_to_map
 193       && (i->data == NULL || i->mapped == 1)
 194       && (abfd->flags & BFD_IN_MEMORY) == 0)
 195     {
 196       file_ptr file_offset, offset2;
 197       size_t real_size;
 198       int fd;
 199
 200       /* Find the real file and the real offset into it.  */
 201       while (abfd->my_archive != NULL
 202              && !bfd_is_thin_archive (abfd->my_archive))
 203         {
 204           offset += abfd->origin;
 205           abfd = abfd->my_archive;
 206         }
 207       offset += abfd->origin;
 208
 209       /* Seek into the file, to ensure it is open if cacheable.  */
 210       if (abfd->iostream == NULL
 211           && (abfd->iovec == NULL
 212               || abfd->iovec->bseek (abfd, offset, SEEK_SET) != 0))
 213         goto free_and_fail;
 214
 215       fd = fileno ((FILE *) abfd->iostream);
 216       /* Compute offsets and size for mmap and for the user's data.  */
 217       offset2 = offset % pagesize;
 218       if (offset2 < 0)
 219         abort ();
 220       file_offset = offset - offset2;
 221       real_size = offset + size - file_offset;
 222       real_size = real_size + pagesize - 1;
 223       real_size -= real_size % pagesize;
 224
 225       /* If we're re-using a memory region, make sure it's big enough.  */
 226       if (i->data != NULL && i->size < size)
 227         {
 228           munmap (i->data, i->size);
 229           i->data = NULL;
 230         }
 231       i->data = mmap (i->data, real_size,
 232                       writable ? PROT_WRITE | PROT_READ : PROT_READ,
 233                       (writable
 234                        ? MAP_FILE | MAP_PRIVATE
 235                        : MAP_FILE | MAP_SHARED),
 236                       fd, file_offset);
 237       if (i->data == (void *) -1)
 238         {
 239           /* An error happened.  Report it, or try using malloc, or
 240              something.  */
 241           bfd_set_error (bfd_error_system_call);
 242           windowp->data = 0;
 243           if (debug_windows)
 244             fprintf (stderr, "\t\tmmap failed!\n");
 245           goto free_and_fail;
 246         }
 247       if (debug_windows)
 248         fprintf (stderr, "\n\tmapped %ld at %p, offset is %ld\n",
 249                  (long) real_size, i->data, (long) offset2);
 250       i->size = real_size;
 251       windowp->data = (bfd_byte *) i->data + offset2;
 252       windowp->size = size;
 253       i->mapped = 1;
 254       i->refcount = 1;
 255       windowp->i = i;
 256       return true;
 257     }
 258   else if (debug_windows)
 259     {
 260       if (ok_to_map)
 261         fprintf (stderr, _("not mapping: data=%lx mapped=%d\n"),
 262                  (unsigned long) i->data, (int) i->mapped);
 263       else
 264         fprintf (stderr, _("not mapping: env var not set\n"));
 265     }
 266 #else
 267   ok_to_map = 0;
 268 #endif
 269
 270 #ifdef HAVE_MPROTECT
 271   if (!writable)
 272     {
 273       size_to_alloc += pagesize - 1;
 274       size_to_alloc -= size_to_alloc % pagesize;
 275     }
 276 #endif
 277   if (debug_windows)
 278     fprintf (stderr, "\n\t%s(%6ld)",
 279              i->data ? "realloc" : " malloc", (long) size_to_alloc);
 280   i->data = bfd_realloc_or_free (i->data, size_to_alloc);
 281   if (debug_windows)
 282     fprintf (stderr, "\t-> %p\n", i->data);
 283   if (i->data == NULL)
 284     {
 285       if (size_to_alloc == 0)
 286         {
 287           windowp->i = i;
 288           return true;
 289         }
 290       goto free_and_fail;
 291     }
 292   i->refcount = 1;
 293   if (bfd_seek (abfd, offset, SEEK_SET) != 0)
 294     goto free_and_fail;
 295   i->size = bfd_read (i->data, size, abfd);
 296   if (i->size != size)
 297     goto free_and_fail;
 298   i->mapped = 0;
 299 #ifdef HAVE_MPROTECT
 300   if (!writable)
 301     {
 302       if (debug_windows)
 303         fprintf (stderr, "\tmprotect (%p, %ld, PROT_READ)\n", i->data,
 304                  (long) i->size);
 305       mprotect (i->data, i->size, PROT_READ);
 306     }
 307 #endif
 308   windowp->data = i->data;
 309   windowp->size = i->size;
 310   windowp->i = i;
 311   return true;
 312
 313  free_and_fail:
 314   /* We have a bfd_window_internal, but an error occurred.  Free it. */
 315   free (i);
 316   return false;
 317 }
 318
 319 #endif /* USE_MMAP */