1/* Support for memory-mapped windows into a BFD.
2   Copyright (C) 1995-2022 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
42static 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/*
50INTERNAL_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
61void
62bfd_init_window (bfd_window *windowp)
63{
64  windowp->data = 0;
65  windowp->i = 0;
66  windowp->size = 0;
67}
68
69void
70bfd_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
105static int ok_to_map = 1;
106
107bool
108bfd_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 */
266