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/* Support for memory-mapped windows into a BFD.
Copyright (C) 1995-2020 Free Software Foundation, Inc.
Written by Cygnus Support.
This file is part of BFD, the Binary File Descriptor library.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
MA 02110-1301, USA. */
#include "sysdep.h"
#include "bfd.h"
#include "libbfd.h"
/* Currently, if USE_MMAP is undefined, none of the window stuff is
used. Enabled by --with-mmap. */
#ifdef USE_MMAP
#undef HAVE_MPROTECT /* code's not tested yet */
#if HAVE_MMAP || HAVE_MPROTECT || HAVE_MADVISE
#include <sys/mman.h>
#endif
#ifndef MAP_FILE
#define MAP_FILE 0
#endif
static int debug_windows;
/* The idea behind the next and refcount fields is that one mapped
region can suffice for multiple read-only windows or multiple
non-overlapping read-write windows. It's not implemented yet
though. */
/*
INTERNAL_DEFINITION
.struct _bfd_window_internal {
. struct _bfd_window_internal *next;
. void *data;
. bfd_size_type size;
. int refcount : 31; {* should be enough... *}
. unsigned mapped : 1; {* 1 = mmap, 0 = malloc *}
.};
*/
void
bfd_init_window (bfd_window *windowp)
{
windowp->data = 0;
windowp->i = 0;
windowp->size = 0;
}
void
bfd_free_window (bfd_window *windowp)
{
bfd_window_internal *i = windowp->i;
windowp->i = 0;
windowp->data = 0;
if (i == 0)
return;
i->refcount--;
if (debug_windows)
fprintf (stderr, "freeing window @%p<%p,%lx,%p>\n",
windowp, windowp->data, (unsigned long) windowp->size, windowp->i);
if (i->refcount != 0)
return;
if (i->mapped)
{
#ifdef HAVE_MMAP
munmap (i->data, i->size);
goto no_free;
#else
abort ();
#endif
}
#ifdef HAVE_MPROTECT
mprotect (i->data, i->size, PROT_READ | PROT_WRITE);
#endif
free (i->data);
#ifdef HAVE_MMAP
no_free:
#endif
i->data = 0;
/* There should be no more references to i at this point. */
free (i);
}
static int ok_to_map = 1;
bfd_boolean
bfd_get_file_window (bfd *abfd,
file_ptr offset,
bfd_size_type size,
bfd_window *windowp,
bfd_boolean writable)
{
static size_t pagesize;
bfd_window_internal *i = windowp->i;
bfd_size_type size_to_alloc = size;
if (debug_windows)
fprintf (stderr, "bfd_get_file_window (%p, %6ld, %6ld, %p<%p,%lx,%p>, %d)",
abfd, (long) offset, (long) size,
windowp, windowp->data, (unsigned long) windowp->size,
windowp->i, writable);
/* Make sure we know the page size, so we can be friendly to mmap. */
if (pagesize == 0)
pagesize = getpagesize ();
if (pagesize == 0)
abort ();
if (i == NULL)
{
i = bfd_zmalloc (sizeof (bfd_window_internal));
if (i == NULL)
return FALSE;
i->data = NULL;
}
#ifdef HAVE_MMAP
if (ok_to_map
&& (i->data == NULL || i->mapped == 1)
&& (abfd->flags & BFD_IN_MEMORY) == 0)
{
file_ptr file_offset, offset2;
size_t real_size;
int fd;
/* Find the real file and the real offset into it. */
while (abfd->my_archive != NULL
&& !bfd_is_thin_archive (abfd->my_archive))
{
offset += abfd->origin;
abfd = abfd->my_archive;
}
/* Seek into the file, to ensure it is open if cacheable. */
if (abfd->iostream == NULL
&& (abfd->iovec == NULL
|| abfd->iovec->bseek (abfd, offset, SEEK_SET) != 0))
goto free_and_fail;
fd = fileno ((FILE *) abfd->iostream);
/* Compute offsets and size for mmap and for the user's data. */
offset2 = offset % pagesize;
if (offset2 < 0)
abort ();
file_offset = offset - offset2;
real_size = offset + size - file_offset;
real_size = real_size + pagesize - 1;
real_size -= real_size % pagesize;
/* If we're re-using a memory region, make sure it's big enough. */
if (i->data != NULL && i->size < size)
{
munmap (i->data, i->size);
i->data = NULL;
}
i->data = mmap (i->data, real_size,
writable ? PROT_WRITE | PROT_READ : PROT_READ,
(writable
? MAP_FILE | MAP_PRIVATE
: MAP_FILE | MAP_SHARED),
fd, file_offset);
if (i->data == (void *) -1)
{
/* An error happened. Report it, or try using malloc, or
something. */
bfd_set_error (bfd_error_system_call);
windowp->data = 0;
if (debug_windows)
fprintf (stderr, "\t\tmmap failed!\n");
goto free_and_fail;
}
if (debug_windows)
fprintf (stderr, "\n\tmapped %ld at %p, offset is %ld\n",
(long) real_size, i->data, (long) offset2);
i->size = real_size;
windowp->data = (bfd_byte *) i->data + offset2;
windowp->size = size;
i->mapped = 1;
i->refcount = 1;
windowp->i = i;
return TRUE;
}
else if (debug_windows)
{
if (ok_to_map)
fprintf (stderr, _("not mapping: data=%lx mapped=%d\n"),
(unsigned long) i->data, (int) i->mapped);
else
fprintf (stderr, _("not mapping: env var not set\n"));
}
#else
ok_to_map = 0;
#endif
#ifdef HAVE_MPROTECT
if (!writable)
{
size_to_alloc += pagesize - 1;
size_to_alloc -= size_to_alloc % pagesize;
}
#endif
if (debug_windows)
fprintf (stderr, "\n\t%s(%6ld)",
i->data ? "realloc" : " malloc", (long) size_to_alloc);
i->data = bfd_realloc_or_free (i->data, size_to_alloc);
if (debug_windows)
fprintf (stderr, "\t-> %p\n", i->data);
if (i->data == NULL)
{
if (size_to_alloc == 0)
{
windowp->i = i;
return TRUE;
}
goto free_and_fail;
}
i->refcount = 1;
if (bfd_seek (abfd, offset, SEEK_SET) != 0)
goto free_and_fail;
i->size = bfd_bread (i->data, size, abfd);
if (i->size != size)
goto free_and_fail;
i->mapped = 0;
#ifdef HAVE_MPROTECT
if (!writable)
{
if (debug_windows)
fprintf (stderr, "\tmprotect (%p, %ld, PROT_READ)\n", i->data,
(long) i->size);
mprotect (i->data, i->size, PROT_READ);
}
#endif
windowp->data = i->data;
windowp->size = i->size;
windowp->i = i;
return TRUE;
free_and_fail:
/* We have a bfd_window_internal, but an error occurred. Free it. */
free (i);
return FALSE;
}
#endif /* USE_MMAP */
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