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1 /* Support for memory-mapped windows into a BFD.
2    Copyright (C) 1995-2014 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_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 
61 void
bfd_init_window(bfd_window * windowp)62 bfd_init_window (bfd_window *windowp)
63 {
64   windowp->data = 0;
65   windowp->i = 0;
66   windowp->size = 0;
67 }
68 
69 void
bfd_free_window(bfd_window * windowp)70 bfd_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 
105 static int ok_to_map = 1;
106 
107 bfd_boolean
bfd_get_file_window(bfd * abfd,file_ptr offset,bfd_size_type size,bfd_window * windowp,bfd_boolean writable)108 bfd_get_file_window (bfd *abfd,
109 		     file_ptr offset,
110 		     bfd_size_type size,
111 		     bfd_window *windowp,
112 		     bfd_boolean 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 	{
149 	  offset += abfd->origin;
150 	  abfd = abfd->my_archive;
151 	}
152 
153       /* Seek into the file, to ensure it is open if cacheable.  */
154       if (abfd->iostream == NULL
155 	  && (abfd->iovec == NULL
156 	      || abfd->iovec->bseek (abfd, offset, SEEK_SET) != 0))
157 	goto free_and_fail;
158 
159       fd = fileno ((FILE *) abfd->iostream);
160       /* Compute offsets and size for mmap and for the user's data.  */
161       offset2 = offset % pagesize;
162       if (offset2 < 0)
163 	abort ();
164       file_offset = offset - offset2;
165       real_size = offset + size - file_offset;
166       real_size = real_size + pagesize - 1;
167       real_size -= real_size % pagesize;
168 
169       /* If we're re-using a memory region, make sure it's big enough.  */
170       if (i->data != NULL && i->size < size)
171 	{
172 	  munmap (i->data, i->size);
173 	  i->data = NULL;
174 	}
175       i->data = mmap (i->data, real_size,
176 		      writable ? PROT_WRITE | PROT_READ : PROT_READ,
177 		      (writable
178 		       ? MAP_FILE | MAP_PRIVATE
179 		       : MAP_FILE | MAP_SHARED),
180 		      fd, file_offset);
181       if (i->data == (void *) -1)
182 	{
183 	  /* An error happened.  Report it, or try using malloc, or
184 	     something.  */
185 	  bfd_set_error (bfd_error_system_call);
186 	  windowp->data = 0;
187 	  if (debug_windows)
188 	    fprintf (stderr, "\t\tmmap failed!\n");
189 	  goto free_and_fail;
190 	}
191       if (debug_windows)
192 	fprintf (stderr, "\n\tmapped %ld at %p, offset is %ld\n",
193 		 (long) real_size, i->data, (long) offset2);
194       i->size = real_size;
195       windowp->data = (bfd_byte *) i->data + offset2;
196       windowp->size = size;
197       i->mapped = 1;
198       i->refcount = 1;
199       windowp->i = i;
200       return TRUE;
201     }
202   else if (debug_windows)
203     {
204       if (ok_to_map)
205 	fprintf (stderr, _("not mapping: data=%lx mapped=%d\n"),
206 		 (unsigned long) i->data, (int) i->mapped);
207       else
208 	fprintf (stderr, _("not mapping: env var not set\n"));
209     }
210 #else
211   ok_to_map = 0;
212 #endif
213 
214 #ifdef HAVE_MPROTECT
215   if (!writable)
216     {
217       size_to_alloc += pagesize - 1;
218       size_to_alloc -= size_to_alloc % pagesize;
219     }
220 #endif
221   if (debug_windows)
222     fprintf (stderr, "\n\t%s(%6ld)",
223 	     i->data ? "realloc" : " malloc", (long) size_to_alloc);
224   i->data = bfd_realloc_or_free (i->data, size_to_alloc);
225   if (debug_windows)
226     fprintf (stderr, "\t-> %p\n", i->data);
227   if (i->data == NULL)
228     {
229       if (size_to_alloc == 0)
230 	{
231 	  windowp->i = i;
232 	  return TRUE;
233 	}
234       goto free_and_fail;
235     }
236   i->refcount = 1;
237   if (bfd_seek (abfd, offset, SEEK_SET) != 0)
238     goto free_and_fail;
239   i->size = bfd_bread (i->data, size, abfd);
240   if (i->size != size)
241     goto free_and_fail;
242   i->mapped = 0;
243 #ifdef HAVE_MPROTECT
244   if (!writable)
245     {
246       if (debug_windows)
247 	fprintf (stderr, "\tmprotect (%p, %ld, PROT_READ)\n", i->data,
248 		 (long) i->size);
249       mprotect (i->data, i->size, PROT_READ);
250     }
251 #endif
252   windowp->data = i->data;
253   windowp->size = i->size;
254   windowp->i = i;
255   return TRUE;
256 
257  free_and_fail:
258   /* We have a bfd_window_internal, but an error occurred.  Free it. */
259   free (i);
260   return FALSE;
261 }
262 
263 #endif /* USE_MMAP */
264