Line data Source code
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
44 274 : write_file (Elf *elf, off_t size, int change_bo, size_t shnum)
45 : {
46 274 : int class = elf->class;
47 :
48 : /* Check the mode bits now, before modification might change them. */
49 : struct stat st;
50 548 : if (unlikely (fstat (elf->fildes, &st) != 0))
51 : {
52 0 : __libelf_seterrno (ELF_E_WRITE_ERROR);
53 0 : 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. */
61 274 : if (elf->parent == NULL
62 274 : && (elf->maximum_size == ~((size_t) 0)
63 274 : || (size_t) size > elf->maximum_size)
64 262 : && unlikely (ftruncate (elf->fildes, size) != 0))
65 : {
66 0 : __libelf_seterrno (ELF_E_WRITE_ERROR);
67 0 : return -1;
68 : }
69 :
70 : /* Try to map the file if this isn't done yet. */
71 274 : if (elf->map_address == NULL && elf->cmd == ELF_C_WRITE_MMAP)
72 : {
73 83 : elf->map_address = mmap (NULL, size, PROT_READ | PROT_WRITE,
74 : MAP_SHARED, elf->fildes, 0);
75 83 : if (unlikely (elf->map_address == MAP_FAILED))
76 0 : elf->map_address = NULL;
77 : }
78 :
79 274 : if (elf->map_address != NULL)
80 : {
81 : /* When using mmap we want to make sure the file content is
82 : really there. Only using ftruncate might mean the file is
83 : extended, but space isn't allocated yet. This might cause a
84 : SIGBUS once we write into the mmapped space and the disk is
85 : full. In glibc posix_fallocate is required to extend the
86 : file and allocate enough space even if the underlying
87 : filesystem would normally return EOPNOTSUPP. But other
88 : implementations might not work as expected. And the glibc
89 : fallback case might fail (with unexpected errnos) in some cases.
90 : So we only report an error when the call fails and errno is
91 : ENOSPC. Otherwise we ignore the error and treat it as just hint. */
92 89 : if (elf->parent == NULL
93 89 : && (elf->maximum_size == ~((size_t) 0)
94 89 : || (size_t) size > elf->maximum_size)
95 89 : && unlikely (posix_fallocate (elf->fildes, 0, size) != 0))
96 0 : if (errno == ENOSPC)
97 : {
98 0 : __libelf_seterrno (ELF_E_WRITE_ERROR);
99 0 : return -1;
100 : }
101 :
102 : /* The file is mmaped. */
103 89 : if ((class == ELFCLASS32
104 36 : ? __elf32_updatemmap (elf, change_bo, shnum)
105 125 : : __elf64_updatemmap (elf, change_bo, shnum)) != 0)
106 : /* Some problem while writing. */
107 0 : size = -1;
108 : }
109 : else
110 : {
111 : /* The file is not mmaped. */
112 185 : if ((class == ELFCLASS32
113 93 : ? __elf32_updatefile (elf, change_bo, shnum)
114 278 : : __elf64_updatefile (elf, change_bo, shnum)) != 0)
115 : /* Some problem while writing. */
116 0 : size = -1;
117 : }
118 :
119 : /* Reduce the file size if necessary. */
120 274 : if (size != -1
121 274 : && elf->parent == NULL
122 274 : && elf->maximum_size != ~((size_t) 0)
123 274 : && (size_t) size < elf->maximum_size
124 12 : && unlikely (ftruncate (elf->fildes, size) != 0))
125 : {
126 0 : __libelf_seterrno (ELF_E_WRITE_ERROR);
127 0 : size = -1;
128 : }
129 :
130 : /* POSIX says that ftruncate and write may clear the S_ISUID and S_ISGID
131 : mode bits. So make sure we restore them afterwards if they were set.
132 : This is not atomic if someone else chmod's the file while we operate. */
133 274 : if (size != -1
134 274 : && unlikely (st.st_mode & (S_ISUID | S_ISGID))
135 : /* fchmod ignores the bits we cannot change. */
136 0 : && unlikely (fchmod (elf->fildes, st.st_mode) != 0))
137 : {
138 0 : __libelf_seterrno (ELF_E_WRITE_ERROR);
139 0 : size = -1;
140 : }
141 :
142 274 : if (size != -1 && elf->parent == NULL)
143 274 : elf->maximum_size = size;
144 :
145 : return size;
146 : }
147 :
148 :
149 : off_t
150 330 : elf_update (Elf *elf, Elf_Cmd cmd)
151 : {
152 : size_t shnum;
153 : off_t size;
154 330 : int change_bo = 0;
155 :
156 660 : if (cmd != ELF_C_NULL
157 330 : && cmd != ELF_C_WRITE
158 9 : && unlikely (cmd != ELF_C_WRITE_MMAP))
159 : {
160 0 : __libelf_seterrno (ELF_E_INVALID_CMD);
161 0 : return -1;
162 : }
163 :
164 330 : if (elf == NULL)
165 : return -1;
166 :
167 330 : if (elf->kind != ELF_K_ELF)
168 : {
169 0 : __libelf_seterrno (ELF_E_INVALID_HANDLE);
170 0 : return -1;
171 : }
172 :
173 : rwlock_wrlock (elf->lock);
174 :
175 : /* Make sure we have an ELF header. */
176 330 : if (elf->state.elf.ehdr == NULL)
177 : {
178 0 : __libelf_seterrno (ELF_E_WRONG_ORDER_EHDR);
179 0 : size = -1;
180 0 : goto out;
181 : }
182 :
183 : /* Determine the number of sections. */
184 660 : shnum = (elf->state.elf.scns_last->cnt == 0
185 : ? 0
186 330 : : 1 + elf->state.elf.scns_last->data[elf->state.elf.scns_last->cnt - 1].index);
187 :
188 : /* Update the ELF descriptor. First, place the program header. It
189 : will come right after the ELF header. The count the size of all
190 : sections and finally place the section table. */
191 660 : size = (elf->class == ELFCLASS32
192 : ? __elf32_updatenull_wrlock (elf, &change_bo, shnum)
193 330 : : __elf64_updatenull_wrlock (elf, &change_bo, shnum));
194 330 : if (likely (size != -1)
195 : /* See whether we actually have to write out the data. */
196 330 : && (cmd == ELF_C_WRITE || cmd == ELF_C_WRITE_MMAP))
197 : {
198 548 : if (elf->cmd != ELF_C_RDWR
199 274 : && elf->cmd != ELF_C_RDWR_MMAP
200 248 : && elf->cmd != ELF_C_WRITE
201 83 : && unlikely (elf->cmd != ELF_C_WRITE_MMAP))
202 : {
203 0 : __libelf_seterrno (ELF_E_UPDATE_RO);
204 0 : size = -1;
205 : }
206 274 : else if (unlikely (elf->fildes == -1))
207 : {
208 : /* We closed the file already. */
209 0 : __libelf_seterrno (ELF_E_FD_DISABLED);
210 0 : size = -1;
211 : }
212 : else
213 274 : size = write_file (elf, size, change_bo, shnum);
214 : }
215 :
216 : out:
217 : rwlock_unlock (elf->lock);
218 :
219 : return size;
220 : }
|
