1 /* Support for memory-mapped windows into a BFD.
2 Copyright (C) 1995-2023 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
51 .typedef struct _bfd_window_internal
52 .{
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 .bfd_window_internal;
60 .
61
62 EXTERNAL
63 .struct _bfd_window_internal;
64 .
65 .typedef struct _bfd_window
66 .{
67 . {* What the user asked for. *}
68 . void *data;
69 . bfd_size_type size;
70 . {* The actual window used by BFD. Small user-requested read-only
71 . regions sharing a page may share a single window into the object
72 . file. Read-write versions shouldn't until I've fixed things to
73 . keep track of which portions have been claimed by the
74 . application; don't want to give the same region back when the
75 . application wants two writable copies! *}
76 . struct _bfd_window_internal *i;
77 .}
78 .bfd_window;
79 .
80 */
81
82 /*
83 FUNCTION
84 bfd_init_window
85
86 SYNOPSIS
87 void bfd_init_window (bfd_window *);
88
89 DESCRIPTION
90 Initialise mmap window.
91 */
92
93 void
94 bfd_init_window (bfd_window *windowp)
95 {
96 windowp->data = 0;
97 windowp->i = 0;
98 windowp->size = 0;
99 }
100
101 /*
102 FUNCTION
103 bfd_free_window
104
105 SYNOPSIS
106 void bfd_free_window (bfd_window *);
107
108 DESCRIPTION
109 Finalise mmap window struct.
110 */
111
112 void
113 bfd_free_window (bfd_window *windowp)
114 {
115 bfd_window_internal *i = windowp->i;
116 windowp->i = 0;
117 windowp->data = 0;
118 if (i == 0)
119 return;
120 i->refcount--;
121 if (debug_windows)
122 fprintf (stderr, "freeing window @%p<%p,%lx,%p>\n",
123 windowp, windowp->data, (unsigned long) windowp->size, windowp->i);
124 if (i->refcount != 0)
125 return;
126
127 if (i->mapped)
128 {
129 #ifdef HAVE_MMAP
130 munmap (i->data, i->size);
131 goto no_free;
132 #else
133 abort ();
134 #endif
135 }
136 #ifdef HAVE_MPROTECT
137 mprotect (i->data, i->size, PROT_READ | PROT_WRITE);
138 #endif
139 free (i->data);
140 #ifdef HAVE_MMAP
141 no_free:
142 #endif
143 i->data = 0;
144 /* There should be no more references to i at this point. */
145 free (i);
146 }
147
148 /*
149 FUNCTION
150 bfd_get_file_window
151
152 SYNOPSIS
153 bool bfd_get_file_window
154 (bfd *, file_ptr, bfd_size_type, bfd_window *, bool {*writable*});
155
156 DESCRIPTION
157 mmap from a bfd's iostream.
158 */
159
160 bool
161 bfd_get_file_window (bfd *abfd,
162 file_ptr offset,
163 bfd_size_type size,
164 bfd_window *windowp,
165 bool writable)
166 {
167 static int ok_to_map = 1;
168 static size_t pagesize;
169 bfd_window_internal *i = windowp->i;
170 bfd_size_type size_to_alloc = size;
171
172 if (debug_windows)
173 fprintf (stderr, "bfd_get_file_window (%p, %6ld, %6ld, %p<%p,%lx,%p>, %d)",
174 abfd, (long) offset, (long) size,
175 windowp, windowp->data, (unsigned long) windowp->size,
176 windowp->i, writable);
177
178 /* Make sure we know the page size, so we can be friendly to mmap. */
179 if (pagesize == 0)
180 pagesize = getpagesize ();
181 if (pagesize == 0)
182 abort ();
183
184 if (i == NULL)
185 {
186 i = bfd_zmalloc (sizeof (bfd_window_internal));
187 if (i == NULL)
188 return false;
189 i->data = NULL;
190 }
191 #ifdef HAVE_MMAP
192 if (ok_to_map
193 && (i->data == NULL || i->mapped == 1)
194 && (abfd->flags & BFD_IN_MEMORY) == 0)
195 {
196 file_ptr file_offset, offset2;
197 size_t real_size;
198 int fd;
199
200 /* Find the real file and the real offset into it. */
201 while (abfd->my_archive != NULL
202 && !bfd_is_thin_archive (abfd->my_archive))
203 {
204 offset += abfd->origin;
205 abfd = abfd->my_archive;
206 }
207 offset += abfd->origin;
208
209 /* Seek into the file, to ensure it is open if cacheable. */
210 if (abfd->iostream == NULL
211 && (abfd->iovec == NULL
212 || abfd->iovec->bseek (abfd, offset, SEEK_SET) != 0))
213 goto free_and_fail;
214
215 fd = fileno ((FILE *) abfd->iostream);
216 /* Compute offsets and size for mmap and for the user's data. */
217 offset2 = offset % pagesize;
218 if (offset2 < 0)
219 abort ();
220 file_offset = offset - offset2;
221 real_size = offset + size - file_offset;
222 real_size = real_size + pagesize - 1;
223 real_size -= real_size % pagesize;
224
225 /* If we're re-using a memory region, make sure it's big enough. */
226 if (i->data != NULL && i->size < size)
227 {
228 munmap (i->data, i->size);
229 i->data = NULL;
230 }
231 i->data = mmap (i->data, real_size,
232 writable ? PROT_WRITE | PROT_READ : PROT_READ,
233 (writable
234 ? MAP_FILE | MAP_PRIVATE
235 : MAP_FILE | MAP_SHARED),
236 fd, file_offset);
237 if (i->data == (void *) -1)
238 {
239 /* An error happened. Report it, or try using malloc, or
240 something. */
241 bfd_set_error (bfd_error_system_call);
242 windowp->data = 0;
243 if (debug_windows)
244 fprintf (stderr, "\t\tmmap failed!\n");
245 goto free_and_fail;
246 }
247 if (debug_windows)
248 fprintf (stderr, "\n\tmapped %ld at %p, offset is %ld\n",
249 (long) real_size, i->data, (long) offset2);
250 i->size = real_size;
251 windowp->data = (bfd_byte *) i->data + offset2;
252 windowp->size = size;
253 i->mapped = 1;
254 i->refcount = 1;
255 windowp->i = i;
256 return true;
257 }
258 else if (debug_windows)
259 {
260 if (ok_to_map)
261 fprintf (stderr, _("not mapping: data=%lx mapped=%d\n"),
262 (unsigned long) i->data, (int) i->mapped);
263 else
264 fprintf (stderr, _("not mapping: env var not set\n"));
265 }
266 #else
267 ok_to_map = 0;
268 #endif
269
270 #ifdef HAVE_MPROTECT
271 if (!writable)
272 {
273 size_to_alloc += pagesize - 1;
274 size_to_alloc -= size_to_alloc % pagesize;
275 }
276 #endif
277 if (debug_windows)
278 fprintf (stderr, "\n\t%s(%6ld)",
279 i->data ? "realloc" : " malloc", (long) size_to_alloc);
280 i->data = bfd_realloc_or_free (i->data, size_to_alloc);
281 if (debug_windows)
282 fprintf (stderr, "\t-> %p\n", i->data);
283 if (i->data == NULL)
284 {
285 if (size_to_alloc == 0)
286 {
287 windowp->i = i;
288 return true;
289 }
290 goto free_and_fail;
291 }
292 i->refcount = 1;
293 if (bfd_seek (abfd, offset, SEEK_SET) != 0)
294 goto free_and_fail;
295 i->size = bfd_bread (i->data, size, abfd);
296 if (i->size != size)
297 goto free_and_fail;
298 i->mapped = 0;
299 #ifdef HAVE_MPROTECT
300 if (!writable)
301 {
302 if (debug_windows)
303 fprintf (stderr, "\tmprotect (%p, %ld, PROT_READ)\n", i->data,
304 (long) i->size);
305 mprotect (i->data, i->size, PROT_READ);
306 }
307 #endif
308 windowp->data = i->data;
309 windowp->size = i->size;
310 windowp->i = i;
311 return true;
312
313 free_and_fail:
314 /* We have a bfd_window_internal, but an error occurred. Free it. */
315 free (i);
316 return false;
317 }
318
319 #endif /* USE_MMAP */