1 /* Update data structures for changes and write them out.
2 Copyright (C) 1999, 2000, 2001, 2002, 2004, 2005, 2006, 2015 Red Hat, Inc.
3 This file is part of elfutils.
4 Contributed by Ulrich Drepper <drepper@redhat.com>, 1999.
5
6 This file is free software; you can redistribute it and/or modify
7 it under the terms of either
8
9 * the GNU Lesser General Public License as published by the Free
10 Software Foundation; either version 3 of the License, or (at
11 your option) any later version
12
13 or
14
15 * the GNU General Public License as published by the Free
16 Software Foundation; either version 2 of the License, or (at
17 your option) any later version
18
19 or both in parallel, as here.
20
21 elfutils is distributed in the hope that it will be useful, but
22 WITHOUT ANY WARRANTY; without even the implied warranty of
23 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
24 General Public License for more details.
25
26 You should have received copies of the GNU General Public License and
27 the GNU Lesser General Public License along with this program. If
28 not, see <http://www.gnu.org/licenses/>. */
29
30 #ifdef HAVE_CONFIG_H
31 # include <config.h>
32 #endif
33
34 #include <libelf.h>
35 #include <fcntl.h>
36 #include <unistd.h>
37 #include <sys/mman.h>
38 #include <sys/stat.h>
39
40 #include "libelfP.h"
41
42
43 static off_t
write_file(Elf * elf,off_t size,int change_bo,size_t shnum)44 write_file (Elf *elf, off_t size, int change_bo, size_t shnum)
45 {
46 int class = elf->class;
47
48 /* Check the mode bits now, before modification might change them. */
49 struct stat st;
50 if (unlikely (fstat (elf->fildes, &st) != 0))
51 {
52 __libelf_seterrno (ELF_E_WRITE_ERROR);
53 return -1;
54 }
55
56 /* Adjust the size in any case. We do this even if we use `write'.
57 We cannot do this if this file is in an archive. We also don't
58 do it *now* if we are shortening the file since this would
59 prevent programs to use the data of the file in generating the
60 new file. We truncate the file later in this case. */
61 if (elf->parent == NULL
62 && (elf->maximum_size == ~((size_t) 0)
63 || (size_t) size > elf->maximum_size)
64 && unlikely (ftruncate (elf->fildes, size) != 0))
65 {
66 __libelf_seterrno (ELF_E_WRITE_ERROR);
67 return -1;
68 }
69
70 /* Try to map the file if this isn't done yet. */
71 if (elf->map_address == NULL && elf->cmd == ELF_C_WRITE_MMAP)
72 {
73 elf->map_address = mmap (NULL, size, PROT_READ | PROT_WRITE,
74 MAP_SHARED, elf->fildes, 0);
75 if (unlikely (elf->map_address == MAP_FAILED))
76 elf->map_address = NULL;
77 else
78 elf->flags |= ELF_F_MMAPPED;
79 }
80
81 if (elf->map_address != NULL)
82 {
83 /* When using mmap we want to make sure the file content is
84 really there. Only using ftruncate might mean the file is
85 extended, but space isn't allocated yet. This might cause a
86 SIGBUS once we write into the mmapped space and the disk is
87 full. In glibc posix_fallocate is required to extend the
88 file and allocate enough space even if the underlying
89 filesystem would normally return EOPNOTSUPP. But other
90 implementations might not work as expected. And the glibc
91 fallback case might fail (with unexpected errnos) in some cases.
92 So we only report an error when the call fails and errno is
93 ENOSPC. Otherwise we ignore the error and treat it as just hint. */
94 if (elf->parent == NULL
95 && (elf->maximum_size == ~((size_t) 0)
96 || (size_t) size > elf->maximum_size))
97 {
98 if (unlikely (posix_fallocate (elf->fildes, 0, size) != 0))
99 if (errno == ENOSPC)
100 {
101 __libelf_seterrno (ELF_E_WRITE_ERROR);
102 return -1;
103 }
104
105 /* Extend the mmap address if needed. */
106 if (elf->cmd == ELF_C_RDWR_MMAP
107 && (size_t) size > elf->maximum_size)
108 {
109 if (mremap (elf->map_address, elf->maximum_size,
110 size, 0) == MAP_FAILED)
111 {
112 __libelf_seterrno (ELF_E_WRITE_ERROR);
113 return -1;
114 }
115 elf->maximum_size = size;
116 }
117
118 }
119
120 /* The file is mmaped. */
121 if ((class == ELFCLASS32
122 ? __elf32_updatemmap (elf, change_bo, shnum)
123 : __elf64_updatemmap (elf, change_bo, shnum)) != 0)
124 /* Some problem while writing. */
125 size = -1;
126 }
127 else
128 {
129 /* The file is not mmaped. */
130 if ((class == ELFCLASS32
131 ? __elf32_updatefile (elf, change_bo, shnum)
132 : __elf64_updatefile (elf, change_bo, shnum)) != 0)
133 /* Some problem while writing. */
134 size = -1;
135 }
136
137 /* Reduce the file size if necessary. */
138 if (size != -1
139 && elf->parent == NULL
140 && elf->maximum_size != ~((size_t) 0)
141 && (size_t) size < elf->maximum_size
142 && unlikely (ftruncate (elf->fildes, size) != 0))
143 {
144 __libelf_seterrno (ELF_E_WRITE_ERROR);
145 size = -1;
146 }
147
148 /* POSIX says that ftruncate and write may clear the S_ISUID and S_ISGID
149 mode bits. So make sure we restore them afterwards if they were set.
150 This is not atomic if someone else chmod's the file while we operate. */
151 if (size != -1
152 && unlikely (st.st_mode & (S_ISUID | S_ISGID))
153 /* fchmod ignores the bits we cannot change. */
154 && unlikely (fchmod (elf->fildes, st.st_mode) != 0))
155 {
156 __libelf_seterrno (ELF_E_WRITE_ERROR);
157 size = -1;
158 }
159
160 if (size != -1 && elf->parent == NULL)
161 elf->maximum_size = size;
162
163 return size;
164 }
165
166
167 off_t
elf_update(Elf * elf,Elf_Cmd cmd)168 elf_update (Elf *elf, Elf_Cmd cmd)
169 {
170 size_t shnum;
171 off_t size;
172 int change_bo = 0;
173
174 if (cmd != ELF_C_NULL
175 && cmd != ELF_C_WRITE
176 && unlikely (cmd != ELF_C_WRITE_MMAP))
177 {
178 __libelf_seterrno (ELF_E_INVALID_CMD);
179 return -1;
180 }
181
182 if (elf == NULL)
183 return -1;
184
185 if (elf->kind != ELF_K_ELF)
186 {
187 __libelf_seterrno (ELF_E_INVALID_HANDLE);
188 return -1;
189 }
190
191 rwlock_wrlock (elf->lock);
192
193 /* Make sure we have an ELF header. */
194 if (elf->state.elf.ehdr == NULL)
195 {
196 __libelf_seterrno (ELF_E_WRONG_ORDER_EHDR);
197 size = -1;
198 goto out;
199 }
200
201 /* Determine the number of sections. */
202 shnum = (elf->state.elf.scns_last->cnt == 0
203 ? 0
204 : 1 + elf->state.elf.scns_last->data[elf->state.elf.scns_last->cnt - 1].index);
205
206 /* Update the ELF descriptor. First, place the program header. It
207 will come right after the ELF header. The count the size of all
208 sections and finally place the section table. */
209 size = (elf->class == ELFCLASS32
210 ? __elf32_updatenull_wrlock (elf, &change_bo, shnum)
211 : __elf64_updatenull_wrlock (elf, &change_bo, shnum));
212 if (likely (size != -1)
213 /* See whether we actually have to write out the data. */
214 && (cmd == ELF_C_WRITE || cmd == ELF_C_WRITE_MMAP))
215 {
216 if (elf->cmd != ELF_C_RDWR
217 && elf->cmd != ELF_C_RDWR_MMAP
218 && elf->cmd != ELF_C_WRITE
219 && unlikely (elf->cmd != ELF_C_WRITE_MMAP))
220 {
221 __libelf_seterrno (ELF_E_UPDATE_RO);
222 size = -1;
223 }
224 else if (unlikely (elf->fildes == -1))
225 {
226 /* We closed the file already. */
227 __libelf_seterrno (ELF_E_FD_DISABLED);
228 size = -1;
229 }
230 else
231 size = write_file (elf, size, change_bo, shnum);
232 }
233
234 out:
235 rwlock_unlock (elf->lock);
236
237 return size;
238 }
239