1/* Support for memory-mapped windows into a BFD.
2   Copyright 1995, 1996, 2001, 2002, 2003, 2005, 2007, 2008, 2009
3   Free Software Foundation, Inc.
4   Written by Cygnus Support.
5
6   This file is part of BFD, the Binary File Descriptor library.
7
8   This program is free software; you can redistribute it and/or modify
9   it under the terms of the GNU General Public License as published by
10   the Free Software Foundation; either version 3 of the License, or
11   (at your option) any later version.
12
13   This program is distributed in the hope that it will be useful,
14   but WITHOUT ANY WARRANTY; without even the implied warranty of
15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16   GNU General Public License for more details.
17
18   You should have received a copy of the GNU General Public License
19   along with this program; if not, write to the Free Software
20   Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
21   MA 02110-1301, USA.  */
22
23#include "sysdep.h"
24
25#include "bfd.h"
26#include "libbfd.h"
27
28/* Currently, if USE_MMAP is undefined, none of the window stuff is
29   used.  Enabled by --with-mmap.  */
30
31#ifdef USE_MMAP
32
33#undef HAVE_MPROTECT /* code's not tested yet */
34
35#if HAVE_MMAP || HAVE_MPROTECT || HAVE_MADVISE
36#include <sys/mman.h>
37#endif
38
39#ifndef MAP_FILE
40#define MAP_FILE 0
41#endif
42
43static int debug_windows;
44
45/* The idea behind the next and refcount fields is that one mapped
46   region can suffice for multiple read-only windows or multiple
47   non-overlapping read-write windows.  It's not implemented yet
48   though.  */
49
50/*
51INTERNAL_DEFINITION
52
53.struct _bfd_window_internal {
54.  struct _bfd_window_internal *next;
55.  void *data;
56.  bfd_size_type size;
57.  int refcount : 31;		{* should be enough...  *}
58.  unsigned mapped : 1;		{* 1 = mmap, 0 = malloc *}
59.};
60*/
61
62void
63bfd_init_window (bfd_window *windowp)
64{
65  windowp->data = 0;
66  windowp->i = 0;
67  windowp->size = 0;
68}
69
70void
71bfd_free_window (bfd_window *windowp)
72{
73  bfd_window_internal *i = windowp->i;
74  windowp->i = 0;
75  windowp->data = 0;
76  if (i == 0)
77    return;
78  i->refcount--;
79  if (debug_windows)
80    fprintf (stderr, "freeing window @%p<%p,%lx,%p>\n",
81	     windowp, windowp->data, (unsigned long) windowp->size, windowp->i);
82  if (i->refcount != 0)
83    return;
84
85  if (i->mapped)
86    {
87#ifdef HAVE_MMAP
88      munmap (i->data, i->size);
89      goto no_free;
90#else
91      abort ();
92#endif
93    }
94#ifdef HAVE_MPROTECT
95  mprotect (i->data, i->size, PROT_READ | PROT_WRITE);
96#endif
97  free (i->data);
98#ifdef HAVE_MMAP
99 no_free:
100#endif
101  i->data = 0;
102  /* There should be no more references to i at this point.  */
103  free (i);
104}
105
106static int ok_to_map = 1;
107
108bfd_boolean
109bfd_get_file_window (bfd *abfd,
110		     file_ptr offset,
111		     bfd_size_type size,
112		     bfd_window *windowp,
113		     bfd_boolean writable)
114{
115  static size_t pagesize;
116  bfd_window_internal *i = windowp->i;
117  bfd_size_type size_to_alloc = size;
118
119  if (debug_windows)
120    fprintf (stderr, "bfd_get_file_window (%p, %6ld, %6ld, %p<%p,%lx,%p>, %d)",
121	     abfd, (long) offset, (long) size,
122	     windowp, windowp->data, (unsigned long) windowp->size,
123	     windowp->i, writable);
124
125  /* Make sure we know the page size, so we can be friendly to mmap.  */
126  if (pagesize == 0)
127    pagesize = getpagesize ();
128  if (pagesize == 0)
129    abort ();
130
131  if (i == 0)
132    {
133      i = bfd_zmalloc (sizeof (bfd_window_internal));
134      windowp->i = i;
135      if (i == 0)
136	return FALSE;
137      i->data = 0;
138    }
139#ifdef HAVE_MMAP
140  if (ok_to_map
141      && (i->data == 0 || i->mapped == 1)
142      && (abfd->flags & BFD_IN_MEMORY) == 0)
143    {
144      file_ptr file_offset, offset2;
145      size_t real_size;
146      int fd;
147
148      /* Find the real file and the real offset into it.  */
149      while (abfd->my_archive != NULL)
150	{
151	  offset += abfd->origin;
152	  abfd = abfd->my_archive;
153	}
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	return FALSE;
160      fd = fileno ((FILE *) abfd->iostream);
161
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 && i->size < size)
173	{
174	  munmap (i->data, i->size);
175	  i->data = 0;
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	  i->data = 0;
189	  windowp->data = 0;
190	  if (debug_windows)
191	    fprintf (stderr, "\t\tmmap failed!\n");
192	  return FALSE;
193	}
194      if (debug_windows)
195	fprintf (stderr, "\n\tmapped %ld at %p, offset is %ld\n",
196		 (long) real_size, i->data, (long) offset2);
197      i->size = real_size;
198      windowp->data = (bfd_byte *) i->data + offset2;
199      windowp->size = size;
200      i->mapped = 1;
201      return TRUE;
202    }
203  else if (debug_windows)
204    {
205      if (ok_to_map)
206	fprintf (stderr, _("not mapping: data=%lx mapped=%d\n"),
207		 (unsigned long) i->data, (int) i->mapped);
208      else
209	fprintf (stderr, _("not mapping: env var not set\n"));
210    }
211#else
212  ok_to_map = 0;
213#endif
214
215#ifdef HAVE_MPROTECT
216  if (!writable)
217    {
218      size_to_alloc += pagesize - 1;
219      size_to_alloc -= size_to_alloc % pagesize;
220    }
221#endif
222  if (debug_windows)
223    fprintf (stderr, "\n\t%s(%6ld)",
224	     i->data ? "realloc" : " malloc", (long) size_to_alloc);
225  i->data = bfd_realloc_or_free (i->data, size_to_alloc);
226  if (debug_windows)
227    fprintf (stderr, "\t-> %p\n", i->data);
228  if (i->data == NULL)
229    {
230      if (size_to_alloc == 0)
231	return TRUE;
232      return FALSE;
233    }
234  i->refcount = 1;
235  if (bfd_seek (abfd, offset, SEEK_SET) != 0)
236    return FALSE;
237  i->size = bfd_bread (i->data, size, abfd);
238  if (i->size != size)
239    return FALSE;
240  i->mapped = 0;
241#ifdef HAVE_MPROTECT
242  if (!writable)
243    {
244      if (debug_windows)
245	fprintf (stderr, "\tmprotect (%p, %ld, PROT_READ)\n", i->data,
246		 (long) i->size);
247      mprotect (i->data, i->size, PROT_READ);
248    }
249#endif
250  windowp->data = i->data;
251  windowp->size = i->size;
252  return TRUE;
253}
254
255#endif /* USE_MMAP */
256