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