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
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 bool
bfd_get_file_window(bfd * abfd,file_ptr offset,bfd_size_type size,bfd_window * windowp,bool writable)108 bfd_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